Advertisement
Research Article

Anti-HIV Activity in Cervical-Vaginal Secretions from HIV-Positive and -Negative Women Correlate with Innate Antimicrobial Levels and IgG Antibodies

  • Mimi Ghosh equal contributor,

    equal contributor Contributed equally to this work with: Mimi Ghosh, John V. Fahey

    Affiliation: Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • John V. Fahey equal contributor,

    equal contributor Contributed equally to this work with: Mimi Ghosh, John V. Fahey

    Affiliation: Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • Zheng Shen,

    Affiliation: Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • Timothy Lahey,

    Affiliation: Department of Microbiology and Immunology and Department of Medicine, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • Susan Cu-Uvin,

    Affiliation: The Immunology Center, The Miriam Hospital, Brown University, Providence, Rhode Island, United States of America

    X
  • Zhijin Wu,

    Affiliation: Department of Community Health and Center for Statistical Sciences, Brown University, Providence, Rhode Island, United States of America

    X
  • Kenneth Mayer,

    Affiliation: The Immunology Center, The Miriam Hospital, Brown University, Providence, Rhode Island, United States of America

    X
  • Peter F. Wright,

    Affiliation: Department of Pediatrics, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • John C. Kappes,

    Affiliations: Department of Medicine, University of Alabama, Birmingham, Alabama, United States of America, Department of Microbiology, University of Alabama, Birmingham, Alabama, United States of America, Department of Pathology, University of Alabama, Birmingham, Alabama, United States of America

    X
  • Christina Ochsenbauer,

    Affiliation: Department of Medicine, University of Alabama, Birmingham, Alabama, United States of America

    X
  • Charles R. Wira mail

    Charles.R.Wira@dartmouth.edu

    Affiliation: Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America

    X
  • Published: June 29, 2010
  • DOI: 10.1371/journal.pone.0011366

Abstract

Background

We investigated the impact of antimicrobials in cervicovaginal lavage (CVL) from HIV(+) and HIV(−) women on target cell infection with HIV. Since female reproductive tract (FRT) secretions contain a spectrum of antimicrobials, we hypothesized that CVL from healthy HIV(+) and (−) women inhibit HIV infection.

Methodology/Principal Findings

CVL from 32 HIV(+) healthy women with high CD4 counts and 15 healthy HIV(−) women were collected by gently washing the cervicovaginal area with 10 ml of sterile normal saline. Following centrifugation, anti-HIV activity in CVL was determined by incubating CVL with HIV prior to addition to TZM-bl cells. Antimicrobials and anti-gp160 HIV IgG antibodies were measured by ELISA. When CXCR4 and CCR5 tropic HIV-1 were incubated with CVL from HIV(+) women prior to addition to TZM-bl cells, anti-HIV activity in CVL ranged from none to 100% inhibition depending on the viral strains used. CVL from HIV(−) controls showed comparable anti-HIV activity. Analysis of CH077.c (clone of an R5-tropic, mucosally-transmitted founder virus) viral inhibition by CVL was comparable to laboratory strains. Measurement of CVL for antimicrobials HBD2, trappin-2/elafin, SLPI and MIP3α indicated that each was present in CVL from HIV(+) and HIV(−) women. HBD2 and MIP3α correlated with anti-HIV activity as did anti-gp160 HIV IgG antibodies in CVL from HIV(+) women.

Conclusions/Significance

These findings indicate that CVL from healthy HIV(+) and HIV(−) women contain innate and adaptive defense mechanisms that inhibit HIV infection. Our data suggest that innate endogenous antimicrobials and HIV-specific IgG in the FRT can act in concert to contribute toward the anti-HIV activity of the CVL and may play a role in inhibition of HIV transmission to women.

Introduction

Heterosexual transmission of HIV is the predominant driver of the growing HIV pandemic [1], [2]. Yet, while considerable attention has been directed to developing topical exogenous microbicides that reduce transmission of HIV-1, relatively little is known about endogenous microbicides produced within the female reproductive tract (FRT). That endogenous microbicides in the female reproductive tract secretions might limit or prevent HIV transmission is suggested by the relatively low risk of HIV transmission per heterosexual coitus, from 1:122 to 1:1000 [3], [4].

We and others have shown that cells of the FRT produce and secrete a spectrum of cytokines, chemokines, and antimicrobials [5][8]. Several specifically inhibit HIV infection of target cells [9], [10]. Antimicrobials secreted by FRT cells include well-characterized anti-HIV molecules, alpha/beta defensins, lactoferrin, and secretory leukocyte protease inhibitor (SLPI), as well as factors such as trappin-2/elafin and MIP3α, which have recently been shown to have anti-HIV activity [9][13]. Some of these factors such as human beta defensins 2 (HBD2) act directly to inhibit virus [10], while others including SDF1α, RANTES, MIP1α, and MIP1β bind to co-receptors to prevent viral entry into target cells [14]. Recent studies have linked the presence of cationic polypeptides in CVL to anti-HSV and anti-HIV activity [15], [16]. Venkataraman et al. showed that when all cationic polypeptides were depleted from the CVL, antimicrobial activity was lost [16].

The isolation of HIV-1 in the FRT was first reported in 1986 [17]. Since then, numerous studies have reported the presence of cell-free HIV-1 RNA, cell-associated HIV-1 RNA, proviral DNA, and culturable virus from the cervix and vagina of pregnant and non-pregnant infected women [18][20]. While it is clear that HIV-1 is shed into the FRT, a detailed understanding of this phenomenon and factors that affect the amount and infectivity of virus in the FRT has not yet been elucidated. Reichelderfer et al. reported that HIV-1 RNA levels in endocervical secretions were highest in the week preceding menses [21]. Other studies have shown no effect of the menstrual cycle on the amount or infectivity of HIV-1 in the FRT [22]. In a recent study, the number of HIV-1 infected cells in endocervical secretions was reported to increase at midcycle just after the periovulatory phase [23]. In other studies, Cummins and colleagues showed that certain innate immune factors in vaginal lavages were more closely associated with HIV-1 shedding in the genital mucosa than plasma viral load [24]. Whether virus is shed into the vagina from the upper FRT remains to be determined. Whereas HIV-1 shedding in CVL secretions is readily detectable, it remains unclear what percentage of the shed virus is actually infectious [24], [25].

In this study, we assessed the levels of multiple candidate endogenous microbicides in cervicovaginal lavage (CVL) specimens from HIV(+) and HIV(−) women, and characterized whether these microbicides correlate with protection from HIV infection. Of the four microbicides analyzed, we found that the levels of two endogenous microbicides, HBD2 and MIP3α correlated with activity against HIV. Analysis of CVL for HIV-specific IgG of healthy HIV(+) women further indicated a positive correlation with anti-HIV activity. These data indicate that CVL from HIV(+) and HIV(−) women contain endogenously produced antimicrobials and IgG (HIV+ samples) that correlate with protection against HIV infection. Further, these findings suggest that, as a consequence of antimicrobial activity in the lower FRT, an environment exists for viral inactivation, which in part may contribute to the low frequency of infectious virus found in FRT secretions. The identification of endogenous microbicides that inhibit HIV transmission should contribute both to our understanding of the pathogenesis of HIV-1, as well as facilitate the development of novel microbicides capitalizing on existing host immune mechanisms.

Methods

HIV(+) Participants

Specimen collection and patient information were provided as a part of an observational study on HIV shedding in women. This study was conducted according to the principles expressed in the Declaration of Helsinki. The study was approved by the Miriam Hospital Institutional Review Board (Brown University, Providence, RI). All patients (HIV(+) and HIV(−)) provided written informed consent for the collection of samples and subsequent analysis. Thirty two HIV(+), sexually abstinent women (48 hrs prior to sampling) between the ages of 16 and 41 years were recruited from The Immunology Center, Miriam Hospital (Table 1). Enrollment criteria included a normal menstrual history, not on hormonal contraceptives, CD4 T cell counts above 350 cells/mm3 (mean 713 (419–1517) cells/mm3), and no exposure to antiretroviral (ARV) drugs. Participants agreed to undergo colposcopic assessment, and were excluded for pregnancy, breastfeeding, menopause, or inter-menstrual bleeding in the previous three months. Additionally, women were excluded if they had douched, used any vaginal products, or had sexual intercourse during the 48 hrs prior to CVL collection. CVL was collected by gently washing the cervicovaginal area with 10 ml of sterile normal saline (pH~7.2). Following CVL collection, samples were centrifuged at 10,000×g for 5 min after which supernatants and cell pellets were stored at −80°C until used. Women were tested for lower genital tract infections including but not limited to bacterial vaginosis (BV), Trichomonas vaginalis, Neisseria gonorrhea and Candida albicans. Race and ethnicity were self-defined by the women involved in the study. Analysis of plasma viral load (PVL) and genital tract viral load (GTVL) RNA as well as CD4 counts, age and race are shown in Table 1.

thumbnail

Table 1. HIV-1 Patient Demographicsa.

doi:10.1371/journal.pone.0011366.t001

HIV(−) Participants

CVL from participants in this study were obtained from the Rhode Island site (Miriam Hospital, Brown University, Providence, RI) of the HIV Epidemiology Research (HER) study. Women ranged in age from 24 to 34 yrs. Race was self-defined by the women involved in the study. CVL was collected by gently washing the cervicovaginal area with 10 ml of sterile normal saline (pH~7.2). Following CVL collection, samples were immediately frozen at −80°C. At the time of analysis, samples were thawed to room temperature, centrifuged at 10,000×g for 5 min after which supernatants were assayed for anti-HIV activity. In preliminary studies (not shown), we compared CVL that were centrifuged after collection and prior to freezing with those that were freeze-thawed once prior to centrifugation and found no differences in anti-HIV inhibitory activity.

HIV Viral Stocks

Laboratory-adapted viral strains HIV-1 IIIB (X4) and BaL (R5) were obtained from Dr. P. Gupta (Univ. of Pittsburgh, PA). Virus stocks were propagated in PHA-stimulated human PBMC and stored frozen at −80°C. Virus stocks produced in PBMC of molecularly cloned HIV-1 NL4.3 (X4; lab-adapted) and YU-2.c (R5; directly cloned without culture) were used in this study. Virus titers were determined on TZM-bl cells as described [26]. Also used was a PBMC-derived virus stock of pCH077.c, a recently generated Clade B infectious molecular clone ([27], [28], Ochsenbauer et al., manuscript in preparation) matching the nucleotide sequence determined to be the transmitted/founder virus sequence of CHAVI subject 700010077.

Measurement of infectious HIV in CVL

Intrinsic anti-HIV activity in CVL was determined using TZM-bl cells [26]. The TZM-bl indicator cell line is a HeLa cell derivative that expresses high levels of CD4, CCR5 and CXCR4. Cells contain HIV long terminal repeat (LTR)-driven β-galactosidase and firefly luciferase reporter cassettes that are activated by HIV infection and subsequent Tat protein expression [26]. TZM-bl cells were routinely subcultured every 3 to 4 days by trypsinization and maintained in TZM-bl media consisting of phenol red-free DMEM (Invitrogen Life Technologies, Carlsbad, CA) supplemented with 10% defined FBS (HyClone, Logan, UT, USA), 2 mM L-glutamine (Invitrogen Life Technologies), and 50 µg/ml primocin (Invivogen, San Diego, CA, USA).

To measure the presence of infectious HIV-1 in CVL, TZM-bl cells were seeded at 2×104 cells per well in a 96-well microtiter plate and allowed to adhere overnight at 37°C. Patient CVL samples were diluted 1:4 in TZM-bl media prior to 100µl being added to TZM-bl cells for 48h at 37°C in 5% CO2. Luciferase activity was measured following manufacturer's instructions. Briefly, following aspiration of supernatants, a beta-glo luciferase substrate (Promega, Madison, WI) solution (100µl) was added to cells. The light intensity of each well was measured using a luminometer. Background luminescence was determined by analyzing uninfected TZM-bl cells. All infectivity assays were performed in quadruplicate. Media diluted CVL had neutral pH values (pH 7.0–7.2).

Measurement of CVL anti-HIV-1 activity

TZM-bl cells were seeded at 2×104 cells per well in a 96-well microtiter plate and allowed to adhere overnight at 37°C. CVL from individual patients were diluted 1:4 and incubated with virus (MOI = 1) for 1hr at 37°C in a final volume of 100µl. Following incubation, media was aspirated from TZM-bl cells and the virus plus CVL mixture (100µl) was added to the cells along with 100µl of TZM-bl media. Luciferase activity was measured as described above. Controls included incubation of TZM-bl with virus alone, CVL alone and cells in media. Uninfected cells were used to determine background luminescence and data was expressed in relative light units (RLU). To calculate percent inhibition, the RLU values of “virus only” wells were averaged and set to 100%. Values of CVL treated virus were calculated as a percentage of the “virus only” and then subtracted from 100 to calculate % inhibition. Viability of TZM-bl cells upon treatment with CVL was quantified using the CellTiter 96® AQueous One Solution Cell Proliferation Assay (Promega) according to manufacturer's instructions. Briefly, reagent was added directly to cell cultures and incubated for 30 min at 37°C followed by reading the plate in a plate reader at OD 490nm.

Measurement of antimicrobials in CVL

CVL supernatants were stored at −80°C until assayed for SLPI, MIP3α and trappin-2/elafin with ELISA test kits or ELISA Duoset kit from R&D Systems (Minneapolis, MN) according to the manufacturer's protocol. Standards for each ELISA were re-suspended in phosphate buffered saline (PBS). Samples were also diluted in 1xPBS. Cytokines were quantified based on standard curves obtained using an ELISA reader (Dynex, Chantilly, VA). HBD2 was assayed with an ELISA test kit from PeproTech (Rocky Hill NJ) according to the manufacturer's protocol.

Measurement of anti-gp160HIV IgA and IgG antibody levels in CVL

Specimens were tested by kinetic ELISA (kELISA) adapted from an assay previously described for influenza [29]. The kELISA measures substrate activation every 9 sec over the first 5 min of the enzymatic assay and plots the change in color per min as mOD/min using a Thermomax microplate reader (Molecular Devices, Sunnyvale, CA). Duplicate wells were coated with MN strain gp160 (Protein Sciences, Meriden, CT). An uncoated well was run with each sample to determine background, which was subtracted from the result. A standard curve with a known positive serum specimen was included in each assay as a measure of sensitivity and reproducibility. Biotinylated anti-human IgG and IgA conjugates were used with streptavidin-HRP and ABTS [29]. The presence of anti-HIV gp160 specific IgG and IgA antibodies used 15mOD as a cut-off for detection.

Measurement of HIV-1 RNA in CVL and Plasma

Nucleic acid sequence-based amplification (BioMerieux, Durham, NC) was used to measure HIV-1 RNA as previously described [30]. All results are expressed as copies per ml with a lower limit of detection of 2.6 log10 (400) copies/ml for both plasma and CVL.

Statistical analysis

Data were analyzed using GraphPad Prism (La Jolla, CA) and STATA 9 (College Station, TX). Mean and standard error were calculated for all data sets. Comparisons of anti-HIV activity between control and CVL groups were done using Mann-Whitney U tests, with a P value of less than 0.05 considered to be significant. We analyzed the correlation between CVL microbicide levels and the percent reduction in HIV infection of TZM-bl cells using Spearman correlation coefficients with a P value threshold for statistical significance of 0.05. The percent reduction in HIV infection of TZM-bl cells for each isolate was divided into quartiles, and a score assigned to each quartile. Then, to assess the impact of a given CVL microbicide with inhibition of target cell infection across viral strains, we assessed the correlation of levels of each endogenous microbicide with summed quartile scores using Spearman correlation coefficients as above.

Results

Infectious HIV-1 in Cervical Vaginal Lavage (CVL) specimens from HIV(+) women

Table 1 shows the patient profiles of HIV(+) women indicating age, race/ethnicity, CD4 count, plasma HIV viral load (PVL) and genital tract HIV viral load (GTVL). Owing to the conditions under which samples were collected, CVL were not collected according to the menstrual cycle stage. Since current methods of measuring GTVL do not distinguish between infectious and non-infectious HIV [24], [25], we used the TZM-bl assay to measure HIV infectivity of CVL specimens and correlated these data with GTVL, and PVL in our HIV(+) patient population. We evaluated 32 CVL from HIV infected women for infectious virus. CVL were obtained from HIV(+) women, who had CD4+ cell counts greater than 350 cells/mm3 and were not on anti-retroviral (ARV) therapy. Samples were diluted 1:4 in media (final pH 7.0–7.2) and added to TZM-bl cells to assess whether virus present in CVL was infectious. As shown in Figure 1, CVL from 3 of 32 women contained virus capable of infecting TZM-bl cells. On further analysis, we observed that of the three women, 2 had bacterial vaginosis, a known enhancement factor for HIV infection [31], and 1 had a Trichomonas infection. We found no correlation between GTVL (Table 1), PVL, and infectious virus in CVL. Of the 3 women with infectious virus (# 11, 25, 29), all had MIP3α and HIV specific IgG levels that were lower than average (Table 2).

thumbnail

Figure 1. Determination of the presence of infectious HIV-1 in CVL from HIV(+) women.

HIV(+) CVL from 32 patients were diluted 1:4 and added directly to TZM-bl cells. The assay was terminated 48h post-infection and HIV-1 infection was quantified by measuring luciferase reporter gene activity using a luminometer and expressed as relative light units (RLU). Each data point in graph represents one individual patient. In the Control (media only) column, each point represents replicate wells. When comparing Controls with the CVL samples (TZM-bl cells incubated with CVL), 3 out of 32 showed RLU levels at least 2-fold above background indicating that these 3 CVL contained infectious HIV-1 which trans-activated the LTR-driven reporter gene.

doi:10.1371/journal.pone.0011366.g001
thumbnail

Table 2. Anti-HIV-1 activity and levels of antimicrobials in secretions from HIV(+) patients.

doi:10.1371/journal.pone.0011366.t002

CVL from HIV(+) women have anti-HIV activity

To determine whether CVL from HIV(+) women inhibit HIV infection of target cells, CVL were incubated with either X4- or R5- tropic HIV-1 at MOI = 1 for 1h at 37°C prior to the measurement of HIV-1 infectivity via the TZM-bl assay. Among individual subjects, we found a spectrum of anti-HIV activity ranging from −134% to 100% inhibition in CVL (Figure 2). In Table 2, as has been reported by others [32][36], we found that some CVL, rather than inhibiting HIV infection, had a stimulatory effect on HIV infectivity without changing background RLU values. Values reported as less than 0% in Table 2 indicate stimulation and are included for completeness. The demonstration of enhancement of viral infection beyond control HIV infection was observed in 33 of 160 assays (20%). The pattern of inhibition was not consistent across viral strains, except in Subject 6 who had below average levels of endogenous microbicides. As seen in Table 2, when compared to virus alone, anti-HIV activity was measurable against both X4 and R5 viruses for the majority of CVL tested. In particular, we found that CVL from some patients had anti-HIV activity between 86–100% across all viruses examined (Patients # 20 and 30). In other cases, we found that anti-HIV activity varied with the virus tested (Patients # 7 and 21). As seen in Table 2, no significant differences were observed among median values for each viral strain examined. Overall, to the best of our knowledge, this is the first demonstration of anti-HIV activity in CVL from North American HIV(+) women who are healthy, and not on ARV therapy.

thumbnail

Figure 2. Measurement of antiviral activity in CVL from HIV(+) women.

Thirty two HIV(+) CVL were diluted 1:4 and incubated with HIV-1 IIIB (X4-tropic) and BaL (R5-tropic) (Panel A) or NL4.3 (X4) and YU-2.c (R5) (Panel B) at a multiplicity of infection (MOI) of 1 for 1h at 37°C prior to infecting TZM-bl cells. Data points in each graph represents one individual patient. Media, “Control”, and “CVL only” wells (Panel A) were set up as negative controls, and replica wells of virus (IIIB, BaL, NL4.3 and YU-2.c) were set up as positive controls. Significant differences (p values) between the mean of the control (virus alone) and that of the cognate virus+CVL are shown in the Figure.

doi:10.1371/journal.pone.0011366.g002

CVL from HIV(−) women have anti-HIV activity

To evaluate whether CVL from HIV(−) women had endogenous anti-HIV activity, samples from 15 healthy women were obtained from the RI HER Repository. As shown in Table 3, we found general inhibition of HIV infection of target cells. Similar to HIV(+) women, CVL from HIV(−) women showed limited enhancement of HIV infectivity beyond control infections (3 of 75 assays). Although 5/15 HIV(−) women had BV (# 3,4,5,10,15), we found no correlations of these samples with anti-HIV activity. As seen in Figures 3A and B, we found that some CVL had potent anti-HIV activity while others had little to no activity. As with HIV(+) healthy women, there was a wide diversity of CVL inhibition with individual viruses.

thumbnail

Figure 3. Analysis of antiviral activity in CVL from HIV(−) women.

Fifteen HIV(−) CVL were diluted 1:4 and incubated with HIV-1 IIIB (X4-tropic) and BaL (R5-tropic) (Panel A) or NL4.3 (X4) and YU-2.c (R5) (Panel B) at MOI 1 for 1h at 37°C prior to infecting TZM-bl cells. Media only “Control” and virus only (IIIB, BaL, NL4.3 and YU-2.c) wells were set up as positive controls. Each data point in graph represents one individual patient. Data points in each graph represents one individual patient. Significant differences between control (virus alone) and virus+CVL are indicated in Figure.

doi:10.1371/journal.pone.0011366.g003
thumbnail

Table 3. Anti-HIV-1 activity and levels of antimicrobials in CVL from HIV(−) women.

doi:10.1371/journal.pone.0011366.t003

Antiviral activity in CVL from HIV(+) and HIV(−) women against an infectious molecularly cloned, transmitted/founder virus

Recent studies focusing on initial HIV transmission have identified the genetic sequences of transmitted/founder HIV-1 viruses responsible for the establishment of initial infection [27]. We evaluated the impact of CVL from HIV(+) and HIV(−) women on infectivity of an infectious molecular clone containing the complete nucleotide sequences of transmitted/founder virus, CH077.c (Ochsenbauer et al. in preparation). As shown in Figures 4A and 4B, when anti-HIV activity was evaluated between different viruses, we found that transmitted/founder virus (CH077.c) was inhibited by CVL from both healthy HIV(+) and HIV(−) women as were laboratory-adapted viruses (IIIB, NL4.3, BaL, and YU-2.c) shown in Tables 2 and 3. These findings suggest that the CH077.c transmitted/founder virus is as susceptible to inhibition by FRT endogenous microbicides as the other strains tested.

thumbnail

Figure 4. Analysis of CH077.c (R5; transmitted/founder Virus) activity in CVL from HIV(+) and HIV(−) women.

Thirty two HIV(+) CVL and 15 HIV(−) CVL were diluted 1:4 and incubated with the R5 transmitted/founder HIV-1 virus CH077.c at MOI 1 for 1h at 37°C prior to infecting TZM-bl cells. Control wells incubated with CVL alone were set up as negative controls and CH077.c wells were set up as positive controls. Each data point in Figure 4A represents one of 32 individual patients. In Figure 4B each data point represents one of 15 individuals. Significant differences between control (CH077.c) and CH077.c + CVL are indicated in Figure.

doi:10.1371/journal.pone.0011366.g004

CVL from HIV(+) and (−) women contain a spectrum of antimicrobials

To define the mechanism(s) through which CVL from HIV(+) and (−) women protect target cells from HIV infection, we analyzed CVL specimens for key endogenous microbicide candidates which we and others have shown in cell culture to have antiviral activity [9][12]. Tables 2 and 3 contain a detailed breakdown of anti-HIV activity as well as the concentrations of 4 known anti-HIV molecules measured in individual CVL samples. Analysis of CVL from HIV(+) and (−) women for SLPI, trappin-2/elafin, MIP3α, and HBD2 indicated that each of these antivirals are present in CVL irrespective of HIV status. Recognizing that CVL specimens from HIV(+) and (−) women were obtained at different times and from different repositories with slightly different protocols, it was surprising to observe that concentrations of MIP3α and SLPI were virtually identical (Tables 2 and 3). Moreover, the concentrations of SLPI in CVL in our studies were comparable to that reported previously by others [15]. Unexpectedly, we found that HBD2 levels were approximately 3-fold greater in HIV(+) women than that seen in HIV(−) women. In contrast, HIV(−) women had significantly (p<0.05) higher values of trappin-2/elafin than HIV(+) women. These data suggest that HIV infection alters the distribution of some endogenous microbicides in FRT secretions.

Anti-gp160HIV IgA and IgG antibodies in CVL from HIV(+) women

To determine whether the CVL of HIV(+) women had antibodies against HIV, we assessed CVL samples for the presence of anti-HIV gp160 specific IgG and IgA antibodies using 15 mOD as a cut-off for detection [29]. As seen in Table 4, we found that 30 out of 32 CVL from HIV(+) women had anti-gp160HIV IgG antibodies, while none were positive for anti-HIV IgA antibodies (data not shown). Neither anti-HIV gp160 IgG nor IgA antibodies were detected in CVL from HIV(−) women (Table 4).

thumbnail

Table 4. HIV GP160-specific IgG in CVL from HIV(+) and HIV(−) women.

doi:10.1371/journal.pone.0011366.t004

Anti-HIV activity correlates with specific antimicrobials and anti-HIV IgG in CVL from HIV(+) women

Table 5 summarizes the correlation by Spearman analysis between % inhibition of HIV infection of target cells by each strain of HIV with concentrations of the four antimicrobials (HBD2, trappin-2/elafin, MIP3α, SLPI) and anti-HIV gp160 IgG. Of the 4 antimicrobials tested, we found positive correlations between the levels of HBD2 and MIP3α as well as anti-HIV IgG with inhibition of some HIV strains. In particular, MIP3α correlated with anti-HIV activity against all 3 of the R5 viruses but neither of the X4 viruses. In contrast, we found no correlation of anti-HIV activity with SLPI and trappin-2/elafin. Similarly, when we analyzed HBD2, MIP3α trappin-2/elafin, and SLPI vs anti-HIV activity in CVL from HIV(−) women, we found no evidence of a positive correlation (data not shown).

thumbnail

Tables 5. Correlation of levels of antimicrobials and anti-HIV IgG in CVL with anti-HIV activity against 5 different viruses.

doi:10.1371/journal.pone.0011366.t005

To further assess the overall contribution of each antimicrobial and anti-HIV IgG for protection against multiple HIV viral strains, the percent reduction in HIV infection of TZM-bl cells for each isolate was divided into quartiles, and a score assigned to each quartile. Then we assessed the correlation of levels of each antimicrobial or anti-HIV IgG with the summed quartile scores using Spearman correlation coefficients as above. As seen in Table 5 (right column), we found significant correlations, identical to that seen above with Spearman analysis, between the levels of HBD2, MIP3α and anti-HIV IgG with the summed percent reduction in HIV infection. These data are further supportive evidence of the importance of HBD2, MIP3α and anti-HIV IgG in protecting the FRT from multiple strains of HIV.

Discussion

The present study evaluated the presence of anti-HIV activity in CVL from HIV(+) healthy and HIV(−) women. When analyzed by ELISA, CVL from HIV(+) and HIV(−) women were found to contain a spectrum of endogenous microbicides with activity against both X4- and R5-tropic HIV.

When CXCR4 and CCR5 tropic HIV-1 were incubated with CVL from HIV(+) women prior to addition to TZM-bl cells, anti-HIV activity in CVL ranged from none to 100% inhibition with some showing enhancement, depending on the viral strains used. CVL from HIV(−) controls showed comparable anti-HIV activity. Importantly, CVL from HIV(+) and HIV(−) women demonstrated potent antiviral activity against a molecular clone of a transmitted/founder virus, CH077.c, that was comparable to laboratory strains. Measurement of CVL for antimicrobials demonstrated that HBD2 and MIP3α correlated with anti-HIV activity as did anti-gp160 HIV IgG antibodies in CVL from HIV(+) women.

The present studies demonstrate that CVL from HIV(+) and HIV(−) women contain at least four microbicides with known anti-HIV activity. We and others have examined SLPI, trappin-2/elafin, MIP3α, and HBD2 and found that each has anti-HIV activity [13], [14], [37][39]. Unexpectedly, in the present study, we found that anti-HIV-1 activity in CVL from HIV(+) women correlated with CVL levels of MIP3α and HBD2 but not with SLPI or trappin-2/elafin. Interestingly, MIP3α concentrations in HIV(+) CVL positively correlated with anti-HIV activity against all 3 R5 HIV strains, including the transmitted/founder virus CH077.c. In addition, anti-HIV activity in CVL from HIV(+) women correlated significantly with anti-gp160HIV IgG antibodies. This is the first study to correlate anti-HIV activity of healthy HIV(+) CVL from North American women with the levels of anti-HIV antibodies. While we have not established that these antibodies possess neutralizing ability, these data clearly suggest a role for antibodies in the immune defense against HIV transmission. Taken together, these findings indicate that CVL from HIV(+) and (−) women contain endogenously produced antimicrobials that inhibit HIV infection, and in doing so may limit both acquisition and transmission of infection.

An unexpected finding was that approximately 3/32 samples from HIV(+) CVL examined contained virus capable of infection, and that infectious virus was independent of plasma and genital tract viral load. While very few studies have measured infectious virus in CVL, others have reported similar low numbers of women with CVL infectious virus [24]. In our study, the 3 women with infectious virus had MIP3α and HIV-specific IgG levels that were lower than average (Table 2 and Table 4). This finding suggests that endogenous antimicrobials such as MIP3α and HIV-specific IgG antibodies are too low to inactivate virus. These findings are of particular importance because they suggest that local protection in CVL may inactivate infectious virus to limit sexual transmission. Others have demonstrated that low vaginal pH can inactivate HIV [40]. That this is unlikely is suggested from studies in which vaginal pH was measured both prior to and immediately following ejaculation. In all cases, vaginal pH was neutralized from 5.6 to 7.2 within 6 seconds [41], [42]. These findings suggest that antivirals, such as MIP3α measured in the present study along with other endogenous microbicides, are responsible for viral inactivation. Further studies are essential to identify the molecules involved in limiting the presence of infectious virus in genital tract secretions.

It is well established that during sexual transmission, R5 strains of HIV are selectively transmitted over X4 strains, although the mechanisms for this are poorly understood [43][45]. An unexpected finding in the present study was the variation in antiviral activity in CVL specimens between individuals and against different viruses. This range of inhibition existed between viruses of the same tropism (X4: IIIB and NL4.3; R5: BaL, YU-2.c and CH077.c) and was independent of subject demographic characteristics. One explanation is that variations in viral envelopes might lead to differences in sensitivity to antivirals in CVL. For example, SLPI and defensins have been shown to inhibit HIV infection based on tropism [46], [47]. Alternatively, since CVL contain a spectrum of antimicrobials that vary with stage of the menstrual cycle [15], it is likely that variations in both the quality and quantity of antimicrobials between individuals contribute to the diversity of antiviral activity seen in this study. The observation that MIP3α, which we have shown to inhibit HIV infection [13], correlated positively with anti-HIV activity against the R5, but not the X4, HIV strains suggests a unique protective role for this antimicrobial against HIV-1 infection. Whether viral differences, cycle stage or heterogeneity of antimicrobials in CVL samples are responsible remains to be determined.

Anti-HIV activity of CVL from HIV(−) women did not correlate with the levels of any of the measured microbicides (data not shown). One explanation for this finding is that the number of HIV(−) CVL samples analyzed in this study [15] was too low. An alternative explanation is that the anti-HIV activity of CVL stems from a combination of multiple endogenous microbicides and that the assessment of no single factor adequately captures the sum total anti-HIV activity of any one woman's CVL microbicides [15], [16], [48]. For example, others have shown that CVL contain the cathelicidin peptide LL37, calprotectin, alpha defensins and lactoferrin, each of which has limited innate antimicrobial activity but can act in synergy to inhibit HIV [9], [49]. What appears not to be involved is pH. Although low pH can selectively destabilize the viral envelope leading to altered viral infectivity [24], all samples tested in this study were diluted in buffered media and found to be pH neutral (pH 7–7.2) prior to assay for anti-HIV activity.

Our studies demonstrate that CVL from a subset of women enhanced HIV infection of target cells. This suggests that CVL from HIV(+) women may contain factors that enhance HIV infection. Such molecules include proinflammatory cytokines such as IL-6, IL-8, TNFα, and IL-1â. These are often present in the CVL in association with pre-existing infections with STI such as bacterial vaginosis (BV), HSV-2, Trichomonas vaginalis, Neisseria gonorrhea, and Candida albicans [50][52]. In fact, BV infection has been frequently found to be a major correlate for enhanced HIV replication in the FRT presumably through the enhanced production of proinflammatory cytokines. Several of these factors can directly enhance HIV replication by stimulating the HIV LTR [32][34], [52], [53]. Another molecule found in serum and mucosal secretions and associated with enhanced HIV replication is myeloid related proteins MRP 8/14 [35]. Another protein, a scavenger receptor gp340, has been shown to be expressed by cervical and vaginal epithelium and promote trans-infection of HIV even when the epithelium remains intact [36], [54].

Some recent studies have demonstrated that the mere presence of anti-HIV molecules in the genital tract does not necessarily correlate with HIV neutralization activity in vivo [55], [56]. This is because some of these anti-HIV molecules such as RANTES, LL37 and MIP3a have potent chemotactic activity and can attract target cells to the site of infection thereby causing an enhancement effect. Another factor that might explain the variability in HIV neutralization ability of CVL is the amount of bioactive anti-HIV molecules present at a given time. Bioactivity is often determined by the presence of multiple families of proteases in the genital tract that are responsible for specific activation and deactivation of immune factors. The Cathepsin family of proteases regulates the family of matrix metalloproteases, which are themselves responsible for activating/deactivating innate immune factors including the anti-HIV molecules SDF-1 and HNP1 [57][60]. Cathepsins are also responsible for directly regulating anti-HIV innate factors [61][63]. For example, Cathepsin D, a cysteine protease present in vaginal secretions [49] has been shown to enhance HIV replication [64], [65]. Although the mechanisms are unclear, it is known that Cathepsin D inhibits MIP3α [61], a known anti-HIV factor in CVL [13]. Kallikreins (KLK) are another family of serine proteases present in the genital mucosa that can activate/deactivate multiple immune factors in the FRT [66] including LL37, a potent anti-HIV molecule [67], [68]. Finally, CD26/dipeptidyl peptidase IV (DPIV) is a serine protease responsible for the cleavage and inactivation of chemokines such as RANTES and SDF-1, which are involved in blocking HIV entry [69], [70]. A further level of complexity arises in that, beyond their ability to activate and inactivate FRT antimicrobials, these protease families are regulated throughout the menstrual cycle by protease inhibitors present in the genital secretions. Several protease inhibitors such as SLPI and trappin-2/elafin are also known anti-HIV molecules [12], [37], [71].

We examined the role of specific endogenous microbicides in the reduction of HIV infection of target cells by CVL from HIV(+) and HIV(−) women, finding that the levels of HBD2 and MIP3α correlated significantly with inhibition of infection. HBD2 is reported to inhibit infection through direct interaction with the virus, as well as decreasing expression of CXCR4, the co-receptor for X4 HIV-1 viruses (but not CCR5) in peripheral blood mononuclear cells and T lymphocytic cells as shown by confocal microscopy and flow cytometry [46]. Sun et. al. did not find a decrease in co-receptor expression with HBD2 treatment, and suggest an effect on the intracellular environment that inhibits HIV [72]. We found that HBD2 and SLPI are present in CVL at concentrations comparable to previous reports [15], [73], [74]. Notably, CVL from HIV(+) women had significantly higher HBD2 than HIV(−) women, suggesting that HIV infection upregulates the production of this potentially protective endogenous microbicide.

One explanation for the variability seen in anti-HIV activity (innate and specific IgG antibodies) in the present study is that it was not possible to collect CVL from HIV(−) and HIV(+) women according to stage of the menstrual cycle. As discussed elsewhere [48], innate and adaptive immunity throughout the female reproductive tract are under hormonal control. For example, we found that midcycle suppression of the humoral immunity by estradiol, which confirms the findings of other laboratories [75], [76], extends to endogenous antimicrobials in CVL [15]. Analysis of the concentrations of cytokines, chemokines and antimicrobials in CVL indicated that SLPI, HBD2, HNP1-3 and lactoferrin dropped significantly at midcycle (day 13) and remained depressed for 7–10 days prior to returning to proliferative phase levels just prior to menstruation. Therefore, owing to hormonal changes during the menstrual cycle, antimicrobials and antibodies may not be present at concentrations sufficient to exert anti-HIV effects. Thus, without compensating mechanisms, innate immune protection is suppressed transiently at midcycle to optimize the chances for successful fertilization, implantation and pregnancy. What is likely is that antiviral activity in CVL is the net and possibly synergistic result of 12–20 antimicrobials present at varying concentrations over the course of the menstrual cycle. Studies to assess the spectrum of antimicrobials in CVL and the ways in which each is altered during the menstrual cycle are essential for a complete understanding of the role of the innate immune system in protection and control of sexual transmission of HIV.

Other studies have demonstrated the presence of anti-HIV antibodies in CVL from HIV(+) women [1], [77][79], but to the best of our knowledge, ours is the first to correlate the levels of these antibodies with anti-HIV activity in CVL from healthy North American HIV(+) women not on any ARVs. These results should prompt an assessment of whether these antibodies exhibit neutralizing activity against HIV, or if the correlation with protection of target cells arises from other mechanisms. Binding but non-neutralizing IgG in the CVL of HIV(+) women has been shown to be protective by lowering viral loads and presenting better clinical outcomes [80]. Such antibodies are believed to protect by inducing ADCC (antibody dependent cellular cytotoxicity) and ADCVI (Antibody dependent cell mediated viral inhibition) [81]. In fact, the recent vaccine trial in Thailand shows preliminary data indicative of protective effects from binding but non-neutralizing antibodies [82]. We also found, similar to other studies [78], [79], [83], that CVL from HIV(+) women lacked anti-HIV specific IgA antibodies, suggesting that IgA in the FRT might not play a substantive role in protection from HIV transmission.

In summary, this study demonstrates that CVL from healthy HIV(+) and HIV(−) women have intrinsic anti-HIV activity and that this activity is most likely mediated through a spectrum of endogenously produced antimicrobials which are capable of inhibiting X4 and R5 viruses. Whereas a spectrum of factors capable of mediating antimicrobial protection are present in CVL, the levels of HBD2, MIP3α and HIV specific IgG antibodies correlated with protection of target cells from infection with HIV. These findings highlight the need for additional studies to more fully understand the influences of the innate immune system and its regulation by sex hormones during the menstrual cycle, pregnancy and following menopause in immune protection throughout the reproductive tract. Moreover, it suggests that a clear understanding of innate protection in the female reproductive tract may lead to new candidate microbicides and approaches for microbicide-mediated immune protection.

Acknowledgments

The authors thank Richard Rossoll, M.S., Dartmouth Medical School, Deena Ratner, B.S., University of Pittsburgh, Irma Rodriguez, Brown University, and Jessica Ingersoll, M.S., Emory University, for excellent technical assistance in the preparation of samples, cells and virus stocks. The authors also thank Dr Phalguni Gupta, University of Pittsburgh, for generous sharing of reagents and information.

Author Contributions

Conceived and designed the experiments: MG JVF SCU KHM CRW. Performed the experiments: MG ZS PFW. Analyzed the data: MG JVF ZS TL ZW PFW CO CRW. Contributed reagents/materials/analysis tools: SCU KHM PFW JCK CO. Wrote the paper: MG JVF TL PFW CO CRW.

References

  1. 1. Mestecky J (2007) Humoral immune responses to the human immunodeficiency virus type-1 (HIV-1) in the genital tract compared to other mucosal sites. J Reprod Immunol 73: 86–97.
  2. 2. CDC (2008) HIV/AIDS Among Women. http://wwwcdcgov/hiv/topics/women/resour​ces/factsheets/pdf/womenpdf.
  3. 3. Gray RH, Wawer MJ, Brookmeyer R, Sewankambo NK, Serwadda D, et al. (2001) Probability of HIV-1 transmission per coital act in monogamous, heterosexual, HIV-1-discordant couples in Rakai, Uganda. Lancet 357: 1149–53.
  4. 4. Wawer MJ, Gray RH, Sewankambo NK, Serwadda D, Li X, et al. (2005) Rates of HIV-1 transmission per coital act, by stage of HIV-1 infection, in Rakai, Uganda. J Infect Dis 191: 1403–9.
  5. 5. Fahey JV, Wright JA, Shen L, Smith JM, Ghosh M, et al. (2008) Estradiol selectively regulates innate immune function by polarized human uterine epithelial cells in culture. Mucosal Immunol 1: 317–25.
  6. 6. Ghosh M, Schaefer TM, Fahey JV, Wright JA, Wira CR (2008) Antiviral responses of human Fallopian tube epithelial cells to toll-like receptor 3 agonist poly(I:C). Fertil Steril 89: 1497–506.
  7. 7. King AE, Fleming DC, Critchley HO, Kelly RW (2003) Differential expression of the natural antimicrobials, beta-defensins 3 and 4, in human endometrium. J Reprod Immunol 59: 1–16.
  8. 8. Schaefer TM, Fahey JV, Wright JA, Wira CR (2005) Innate immunity in the human female reproductive tract: antiviral response of uterine epithelial cells to the TLR3 agonist poly(I:C). J Immunol 174: 992–1002.
  9. 9. Cole AM, Cole AL (2008) Antimicrobial polypeptides are key anti-HIV-1 effector molecules of cervicovaginal host defense. Am J Reprod Immunol 59: 27–34.
  10. 10. Iqbal SM, Kaul R (2008) Mucosal innate immunity as a determinant of HIV susceptibility. Am J Reprod Immunol 59: 44–54.
  11. 11. Cole AM (2006) Innate host defense of human vaginal and cervical mucosae. Curr Top Microbiol Immunol 306: 199–230.
  12. 12. Moreau T, Baranger K, Dade S, Dallet-Choisy S, Guyot N, et al. (2008) Multifaceted roles of human elafin and secretory leukocyte proteinase inhibitor (SLPI), two serine protease inhibitors of the chelonianin family. Biochimie 90: 284–95.
  13. 13. Ghosh M, Shen Z, Schaefer TM, Fahey JV, Gupta P, et al. (2009) CCL20/MIP3alpha is a novel anti-HIV-1 molecule of the human female reproductive tract. Am J Reprod Immunol 62: 60–71.
  14. 14. Garzino-Demo A (2007) Chemokines and defensins as HIV suppressive factors: an evolving story. Curr Pharm Des 13: 163–72.
  15. 15. Keller MJ, Guzman E, Hazrati E, Kasowitz A, Cheshenko N, et al. (2007) PRO 2000 elicits a decline in genital tract immune mediators without compromising intrinsic antimicrobial activity. Aids 21: 467–76.
  16. 16. Venkataraman N, Cole AL, Svoboda P, Pohl J, Cole AM (2005) Cationic polypeptides are required for anti-HIV-1 activity of human vaginal fluid. J Immunol 175: 7560–7.
  17. 17. Vogt MW, Witt DJ, Craven DE, Byington R, Crawford DF, et al. (1986) Isolation of HTLV-III/LAV from cervical secretions of women at risk for AIDS. Lancet 1: 525–7.
  18. 18. Henin Y, Mandelbrot L, Henrion R, Pradinaud R, Coulaud JP, et al. (1993) Virus excretion in the cervicovaginal secretions of pregnant and nonpregnant HIV-infected women. J Acquir Immune Defic Syndr 6: 72–5.
  19. 19. Kreiss J, Willerford DM, Hensel M, Emonyi W, Plummer F, et al. (1994) Association between cervical inflammation and cervical shedding of human immunodeficiency virus DNA. J Infect Dis 170: 1597–601.
  20. 20. Moss GB, Clemetson D, D'Costa L, Plummer FA, Ndinya-Achola JO, et al. (1991) Association of cervical ectopy with heterosexual transmission of human immunodeficiency virus: results of a study of couples in Nairobi, Kenya. J Infect Dis 164: 588–91.
  21. 21. Reichelderfer PS, Coombs RW, Wright DJ, Cohn J, Burns DN, et al. (2000) Effect of menstrual cycle on HIV-1 levels in the peripheral blood and genital tract. WHS 001 Study Team. Aids 14: 2101–7.
  22. 22. Villanueva JM, Ellerbrock TV, Lennox JL, Bush TJ, Wright TC, et al. (2002) The menstrual cycle does not affect human immunodeficiency virus type 1 levels in vaginal secretions. J Infect Dis 185: 170–7.
  23. 23. Benki S, Mostad SB, Richardson BA, Mandaliya K, Kreiss JK, et al. (2008) Increased levels of HIV-1-infected cells in endocervical secretions after the luteinizing hormone surge. J Acquir Immune Defic Syndr 47: 529–34.
  24. 24. Cummins JE Jr, Villanueva JM, Evans-Strickfaden T, Sesay SM, Abner SR, et al. (2003) Detection of infectious human immunodeficiency virus type 1 in female genital secretions by a short-term culture method. J Clin Microbiol 41: 4081–8.
  25. 25. Kovacs A, Chan LS, Chen ZC, Meyer WA 3rd, Muderspach L, et al. (1999) HIV-1 RNA in plasma and genital tract secretions in women infected with HIV-1. J Acquir Immune Defic Syndr 22: 124–31.
  26. 26. Wei X, Decker JM, Liu H, Zhang Z, Arani RB, et al. (2002) Emergence of resistant human immunodeficiency virus type 1 in patients receiving fusion inhibitor (T-20) monotherapy. Antimicrob Agents Chemother 46: 1896–905.
  27. 27. Keele BF, Giorgi EE, Salazar-Gonzalez JF, Decker JM, Pham KT, et al. (2008) Identification and characterization of transmitted and early founder virus envelopes in primary HIV-1 infection. Proc Natl Acad Sci U S A 105: 7552–7.
  28. 28. Salazar-Gonzalez JF, Salazar MG, Keele BF, Learn GH, Giorgi EE, et al. (2009) Genetic identity, biological phenotype, and evolutionary pathways of transmitted/founder viruses in acute and early HIV-1 infection. J Exp Med 206: 1273–89.
  29. 29. Wright PF, Kozlowski PA, Rybczyk GK, Goepfert P, Staats HF, et al. (2002) Detection of mucosal antibodies in HIV type 1-infected individuals. AIDS Res Hum Retroviruses 18: 1291–300.
  30. 30. Cu-Uvin S, Snyder B, Harwell JI, Hogan J, Chibwesha C, et al. (2006) Association between paired plasma and cervicovaginal lavage fluid HIV-1 RNA levels during 36 months. J Acquir Immune Defic Syndr 42: 584–7.
  31. 31. Spear GT, St John E, Zariffard MR (2007) Bacterial vaginosis and human immunodeficiency virus infection. AIDS Res Ther 4: 25.
  32. 32. Lane BR, Lore K, Bock PJ, Andersson J, Coffey MJ, et al. (2001) Interleukin-8 stimulates human immunodeficiency virus type 1 replication and is a potential new target for antiretroviral therapy. J Virol 75: 8195–202.
  33. 33. Poli G, Bressler P, Kinter A, Duh E, Timmer WC, et al. (1990) Interleukin 6 induces human immunodeficiency virus expression in infected monocytic cells alone and in synergy with tumor necrosis factor alpha by transcriptional and post-transcriptional mechanisms. J Exp Med 172: 151–8.
  34. 34. Spear GT, Zariffard MR, Chen HY, Anzinger JJ, Anastos K, et al. (2008) Positive association between HIV RNA and IL-6 in the genital tract of Rwandan women. AIDS Res Hum Retroviruses 24: 973–6.
  35. 35. Hashemi FB, Mollenhauer J, Madsen LD, Sha BE, Nacken W, et al. (2001) Myeloid-related protein (MRP)-8 from cervico-vaginal secretions activates HIV replication. Aids 15: 441–9.
  36. 36. Stoddard E, Cannon G, Ni H, Kariko K, Capodici J, et al. (2007) gp340 expressed on human genital epithelia binds HIV-1 envelope protein and facilitates viral transmission. J Immunol 179: 3126–32.
  37. 37. Ghosh M, Shen Z, Fahey JV, Cu-Uvin S, Mayer K, et al. (2009) Trappin-2/Elafin: a novel innate anti-HIV-1 molecule of the human female reproductive tract. Immunology. In press.
  38. 38. McNeely T, Shugars D, Rosendahl M, Tucker C, Eisenberg S, et al. (1997) Inhibition of human immunodeficiency virus type 1 infectivity by secretory leukocyte protease inhibitor occurs prior to viral reverse transcription. Blood 90: 1141–9.
  39. 39. Bingle CD, Vyakarnam A (2008) Novel innate immune functions of the whey acidic protein family. Trends Immunol 29: 444–53.
  40. 40. Hillier S (1998) The vaginal microbial ecosystem and resistance to HIV. AIDS Res Hum Retroviruses Suppl 1: S17–21.
  41. 41. Fox CA, Meldrum SJ, Watson BW (1973) Continuous Measurement by radio-telemetry of vaginal pH during human coitus. J Reprod Fert 33: 69–75.
  42. 42. Tevi-Benissan C, Belec L, Levy M, Schneider-Fauveau V, Si Mohamed A, et al. (1997) In vivo semen-associated pH neutralization of cervicovaginal secretions. Clin Diagn Lab Immunol 4: 367–74.
  43. 43. Margolis L, Shattock R (2006) Selective transmission of CCR5-utilizing HIV-1: the ‘gatekeeper’ problem resolved? Nat Rev Microbiol 4: 312–7.
  44. 44. Berlier W, Bourlet T, Lawrence P, Hamzeh H, Lambert C, et al. (2005) Selective sequestration of X4 isolates by human genital epithelial cells: Implication for virus tropism selection process during sexual transmission of HIV. J Med Virol 77: 465–74.
  45. 45. Saidi H, Magri G, Nasreddine N, Requena M, Belec L (2007) R5- and X4-HIV-1 use differentially the endometrial epithelial cells HEC-1A to ensure their own spread: implication for mechanisms of sexual transmission. Virology 358: 55–68.
  46. 46. Quinones-Mateu ME, Lederman MM, Feng Z, Chakraborty B, Weber J, et al. (2003) Human epithelial beta-defensins 2 and 3 inhibit HIV-1 replication. Aids 17: F39–48.
  47. 47. Skott P, Lucht E, Ehnlund M, Bjorling E (2002) Inhibitory function of secretory leukocyte proteinase inhibitor (SLPI) in human saliva is HIV-1 specific and varies with virus tropism. Oral Dis 8: 160–7.
  48. 48. Wira CR, Fahey JV (2008) A new strategy to understand how HIV infects women: identification of a window of vulnerability during the menstrual cycle. Aids 22: 1909–17.
  49. 49. Cummins JE, Christensen L, Lennox JL, Bush TJ, Wu Z, et al. (2006) Mucosal innate immune factors in the female genital tract are associated with vaginal HIV-1 shedding independent of plasma viral load. AIDS Res Hum Retroviruses 22: 788–95.
  50. 50. Novak RM, Donoval BA, Graham PJ, Boksa LA, Spear G, et al. (2007) Cervicovaginal levels of lactoferrin, secretory leukocyte protease inhibitor, and RANTES and the effects of coexisting vaginoses in human immunodeficiency virus (HIV)-seronegative women with a high risk of heterosexual acquisition of HIV infection. Clin Vaccine Immunol 14: 1102–7.
  51. 51. Sha BE, D'Amico RD, Landay AL, Spear GT, Massad LS, et al. (1997) Evaluation of immunologic markers in cervicovaginal fluid of HIV-infected and uninfected women: implications for the immunologic response to HIV in the female genital tract. J Acquir Immune Defic Syndr Hum Retrovirol 16: 161–8.
  52. 52. Spear GT, Zariffard MR, Cohen MH, Sha BE (2008) Vaginal IL-8 levels are positively associated with Candida albicans and inversely with lactobacilli in HIV-infected women. J Reprod Immunol 78: 76–9.
  53. 53. Ryckman C, Robichaud GA, Roy J, Cantin R, Tremblay MJ, et al. (2002) HIV-1 transcription and virus production are both accentuated by the proinflammatory myeloid-related proteins in human CD4+ T lymphocytes. J Immunol 169: 3307–13.
  54. 54. Cannon G, Yi Y, Ni H, Stoddard E, Scales DA, et al. (2008) HIV envelope binding by macrophage-expressed gp340 promotes HIV-1 infection. J Immunol 181: 2065–70.
  55. 55. Kaul R, Pettengell C, Sheth PM, Sunderji S, Biringer A, et al. (2008) The genital tract immune milieu: an important determinant of HIV susceptibility and secondary transmission. J Reprod Immunol 77: 32–40.
  56. 56. Levinson P, Kaul R, Kimani J, Ngugi E, Moses S, et al. (2009) Levels of innate immune factors in genital fluids: association of alpha defensins and LL-37 with genital infections and increased HIV acquisition. Aids 23: 309–17.
  57. 57. Jokimaa V, Oksjoki S, Kujari H, Vuorio E, Anttila L (2001) Expression patterns of cathepsins B, H, K, L and S in the human endometrium. Mol Hum Reprod 7: 73–8.
  58. 58. McQuibban GA, Gong JH, Tam EM, McCulloch CA, Clark-Lewis I, et al. (2000) Inflammation dampened by gelatinase A cleavage of monocyte chemoattractant protein-3. Science (New York, NY 289: 1202–6.
  59. 59. Wilson CL, Ouellette AJ, Satchell DP, Ayabe T, Lopez-Boado YS, et al. (1999) Regulation of intestinal alpha-defensin activation by the metalloproteinase matrilysin in innate host defense. Science (New York, NY 286: 113–7.
  60. 60. Zhang K, McQuibban GA, Silva C, Butler GS, Johnston JB, et al. (2003) HIV-induced metalloproteinase processing of the chemokine stromal cell derived factor-1 causes neurodegeneration. Nat Neurosci 6: 1064–71.
  61. 61. Hasan L, Mazzucchelli L, Liebi M, Lis M, Hunger RE, et al. (2006) Function of liver activation-regulated chemokine/CC chemokine ligand 20 is differently affected by cathepsin B and cathepsin D processing. J Immunol 176: 6512–22.
  62. 62. Taggart CC, Greene CM, Smith SG, Levine RL, McCray PB Jr, et al. (2003) Inactivation of human beta-defensins 2 and 3 by elastolytic cathepsins. J Immunol 171: 931–7.
  63. 63. Lim JK, Lu W, Hartley O, DeVico AL (2006) N-terminal proteolytic processing by cathepsin G converts RANTES/CCL5 and related analogs into a truncated 4–68 variant. J Leukoc Biol 80: 1395–404.
  64. 64. El Messaoudi K, Thiry L, Van Tieghem N, Liesnard C, Englert Y, et al. (1999) HIV-1 infectivity and host range modification by cathepsin D present in human vaginal secretions. Aids 13: 333–9.
  65. 65. El Messaoudi K, Thiry LF, Liesnard C, Van Tieghem N, Bollen A, et al. (2000) A human milk factor susceptible to cathepsin D inhibitors enhances human immunodeficiency virus type 1 infectivity and allows virus entry into a mammary epithelial cell line. J Virol 74: 1004–7.
  66. 66. Shaw JL, Petraki C, Watson C, Bocking A, Diamandis EP (2008) Role of tissue kallikrein-related peptidases in cervical mucus remodeling and host defense. Biol Chem 389: 1513–22.
  67. 67. Steinstraesser L, Tippler B, Mertens J, Lamme E, Homann HH, et al. (2005) Inhibition of early steps in the lentiviral replication cycle by cathelicidin host defense peptides. Retrovirology 2: 2.
  68. 68. Yamasaki K, Schauber J, Coda A, Lin H, Dorschner RA, et al. (2006) Kallikrein-mediated proteolysis regulates the antimicrobial effects of cathelicidins in skin. Faseb J 20: 2068–80.
  69. 69. Oravecz T, Pall M, Roderiquez G, Gorrell MD, Ditto M, et al. (1997) Regulation of the receptor specificity and function of the chemokine RANTES (regulated on activation, normal T cell expressed and secreted) by dipeptidyl peptidase IV (CD26)-mediated cleavage. J Exp Med 186: 1865–72.
  70. 70. Shioda T, Kato H, Ohnishi Y, Tashiro K, Ikegawa M, et al. (1998) Anti-HIV-1 and chemotactic activities of human stromal cell-derived factor 1alpha (SDF-1alpha) and SDF-1beta are abolished by CD26/dipeptidyl peptidase IV-mediated cleavage. Proc Natl Acad Sci U S A 95: 6331–6.
  71. 71. Iqbal SM, Ball TB, Levinson P, Maranan L, Jaoko W, et al. (2009) Elevated elafin/trappin-2 in the female genital tract is associated with protection against HIV acquisition. Aids 23: 1669–77.
  72. 72. Sun L, Finnegan CM, Kish-Catalone T, Blumenthal R, Garzino-Demo P, et al. (2005) Human beta-defensins suppress human immunodeficiency virus infection: potential role in mucosal protection. J Virol 79: 14318–29.
  73. 73. Cummins JE Jr, Denniston M, Mayer KH, Pickard R, Novak RM, et al. (2007) Mucosal innate immune factors in secretions from high-risk individuals immunized with a bivalent gp120 vaccine. AIDS Res Hum Retroviruses 23: 748–54.
  74. 74. Fan SR, Liu XP, Liao QP (2008) Human defensins and cytokines in vaginal lavage fluid of women with bacterial vaginosis. Int J Gynaecol Obstet 103: 50–4.
  75. 75. Schumacher G (1973) Soluble proteins in cervical mucus. The biology of the cervix The University of Chicago Press 201–33.
  76. 76. Nardelli-Haefliger DJ, Wirthner D, Schiller J, Lowy D, Hildesheim A, et al. (2003) Specific Antibody Levels at the Cervix During the Menstrual Cycle of Women Vaccinated With Human Papillomavirus 16 Virus–Like Particles. J Nat Cancer Inst 95: 1128–37.
  77. 77. Alexander R, Mestecky J (2007) Neutralizing antibodies in mucosal secretions: IgG or IgA? Curr HIV Res 5: 588–93.
  78. 78. Fiore JR, Laddago V, Lepera A, La Grasta L, Di Stefano M, et al. (2000) Limited secretory-IgA response in cervicovaginal secretions from HIV-1 infected, but not high risk seronegative women: lack of correlation to genital viral shedding. New Microbiol 23: 85–92.
  79. 79. Kang G, Samuel R, Vijayakumar TS, Selvi S, Sridharan G, et al. (2005) Community prevalence of antibodies to human immunodeficiency virus in rural and urban Vellore, Tamil Nadu. Natl Med J India 18: 15–7.
  80. 80. Nag P, Kim J, Sapiega V, Landay AL, Bremer JW, et al. (2004) Women with cervicovaginal antibody-dependent cell-mediated cytotoxicity have lower genital HIV-1 RNA loads. J Infect Dis 190: 1970–8.
  81. 81. Florese RH, Demberg T, Xiao P, Kuller L, Larsen K, et al. (2009) Contribution of nonneutralizing vaccine-elicited antibody activities to improved protective efficacy in rhesus macaques immunized with Tat/Env compared with multigenic vaccines. J Immunol 182: 3718–27.
  82. 82. Rerks-Ngarm S, Pitisuttithum P, Nitayaphan S, Kaewkungwal J, Chiu J, et al. (2009) Vaccination with ALVAC and AIDSVAX to prevent HIV-1 infection in Thailand. N Engl J Med 361: 2209–20.
  83. 83. Mestecky J, Jackson S, Moldoveanu Z, Nesbit LR, Kulhavy R, et al. (2004) Paucity of antigen-specific IgA responses in sera and external secretions of HIV-type 1-infected individuals. AIDS Res Hum Retroviruses 20: 972–88.