Impact of microbicides and sexually transmitted infections on mucosal immunity in the female genital tract

Evaluation of the novel vaginal contraceptive agent PPCM in preclinical studies using sperm hyaluronan binding and acrosome status assays

Background

Polyphenylene carboxymethylene (PPCM) sodium salt is a promising multipurpose technology for prevention of both sexually transmitted infections (STIs) and pregnancy. In preclinical studies, PPCM has demonstrated significant (1) antimicrobial activity against several important viral and bacterial pathogens and (2) contraceptive activity associated with premature acrosome loss.

Objective

To further evaluate a vaginal antimicrobial compound as a contraceptive agent in preclinical studies utilizing a repurposed hyaluronan binding assay (HBA).

Materials and methods

Semen samples containing either neat semen or washed spermatozoa were treated with increasing concentrations of PPCM or calcium ionophore A23187 (positive control). Sperm inactivation was measured by two methods: (1) double acrosome staining (AS), and (2) a hyaluronan binding assay (HBA^®). Percentage of inactivated sperm was compared between untreated control sperm and those treated with PPCM or A23187.

Results

PPCM had a significant (p < 0.05) and dose‐dependent effect on sperm inactivation in both assays, with HBA detecting a higher proportion of inactivated sperm than AS. PPCM did not affect sperm motility and exhibited equivalent responses in the neat and washed samples.

Discussion

Both HBA and AS confirmed that spermatozoa were rapidly inactivated at PPCM concentrations likely present in the vagina under actual use conditions and in a time‐frame comparable to in vivo migration of spermatozoa out of seminal plasma into cervical mucus.

Conclusion

PPCM vaginal gel may provide contraceptive protection as well as help with STI prevention. HBA may be a sensitive and much needed biomarker for sperm activity in future contraceptive development.

Association of High-Risk Human Papillomavirus with Genital Tract Mucosal Immune Factors in HIV-Infected Women

PROBLEM

High-risk human papillomavirus (HR-HPV) is prevalent in HIV-infected women and may be associated with mucosal changes that promote HIV replication.

METHOD OF STUDY

Innate immune molecules, antimicrobial activity, HIV RNA, and HPV DNA genotypes were measured in a cross-sectional study of 128 HIV-infected women categorized into HPV-16 (n = 8), other HR-HPV (n = 41), and non-HR-HPV controls (n = 79).

RESULTS

Compared to controls, HR-HPV groups had higher plasma viral loads (P = 0.004), lower CD4 cells (P = 0.02), more genital tract HIV RNA (P = 0.03), greater number of different HPV types (P < 0.001), higher cervicovaginal lavage (CVL) IL-1α (P = 0.03) and human beta-defensin 2 (HBD2) (P = 0.049), and less anti-HIVB al activity (P = 0.03). HPV-16 remained significantly associated with higher HBD2 (P = 0.03), higher IL-1α (P = 0.009), and lower anti-HIVB aL activity (P = 0.03) compared to controls after adjusting for plasma viral load and CD4 T cell count.

CONCLUSION

HR-HPV is associated with mucosal changes in HIV-infected women that could adversely impact genital tract health.

The role of dendritic cells in driving genital tract inflammation and HIV transmission risk: are there opportunities to intervene?

Effective prevention of new HIV infections will require an understanding of the mechanisms involved in HIV acquisition. HIV transmission across the female genital tract is the major mode of new HIV infections in sub-Saharan Africa and involves complex processes, including cell activation, inflammation and recruitment of HIV target cells. Activated CD4(+) T-cells, dendritic cells (DC) and macrophages have been described as targets for HIV at the genital mucosa. Activation of these cells may occur in the presence of sexually-transmitted infections, disturbances of commensal flora and other inflammatory processes. In this review, we discuss causes and consequences of inflammation in the female genital tract, with a focus on DC. We describe the central role these cells may play in facilitating or preventing HIV transmission across the genital mucosa, and in the initial recognition of HIV and other pathogens, allowing activation of an adaptive immune response to infection. We discuss studies that investigate interventions to limit DC activation, inflammation and HIV transmission. This knowledge is essential in the development of novel strategies for effective HIV control, including microbicides and pre-exposure prophylaxis.

Antiviral activity of genital tract secretions after oral or topical tenofovir pre-exposure prophylaxis for HIV-1

BACKGROUND

Surrogate markers of HIV-1 pre-exposure prophylaxis and microbicide efficacy are needed. One potential surrogate is the antiviral activity in cervicovaginal lavage (CVL) after exposure to candidate products. We measured CVL antiviral activity in women using oral or vaginal tenofovir-based pre-exposure prophylaxis and correlated activity with drug and immune mediator levels.

METHODS

Inhibitory activity against HIV-1 and herpes simplex virus (HSV)-2 and concentrations of interleukin (IL)-1β, IL-6, IL-8, interferon-γ, induced protein 10 (IP-10), macrophage inflammatory protein (MIP)-1α, MIP-3a, lactoferrin, secretory leukocyte protease inhibitor, and defensins were measured in CVL obtained from 60 women at baseline and after 6 weeks of a randomized sequence of oral and topical tenofovir. CVL tenofovir concentrations were measured by mass spectrometry.

RESULTS

The number of women with CVL anti-HIV activity ≥ 90% increased significantly from 5.0% at baseline to 89.1% after daily use of 1% tenofovir gel (relative risk = 17.85, P < 0.001), but there was no increase after daily oral tenofovir. The CVL anti-HIV activity correlated with drug levels (Spearman correlation coefficient 0.64 after tenofovir gel; P < 0.001) but not with the concentrations of mucosal immune mediators. No increase in CVL anti-HSV activity was observed after either drug regimen, an observation consistent with the higher concentrations of tenofovir needed to inhibit HSV-2 infection. The CVL anti-HSV activity correlated with lactoferrin, defensins, IP-10, IL-8, and detectable levels of MIP-1α but not with drug levels.

CONCLUSIONS

CVL may provide a surrogate for local but not systemic drug efficacy and a tool to better understand mucosal factors that modulate antiviral activity in genital tract secretions.

Antigen-presenting cell candidates for HIV-1 transmission in human distal colonic mucosa defined by CD207 dendritic cells and CD209 macrophages

A common route for HIV-1 infection is sexual transmission across colorectal mucosa, which is thought to be 10-2,000 times more vulnerable to infection than that of the female genital tract. Mucosal surfaces are the first line of defense against many pathogens but the antigen-presenting cells (APCs), key regulators of innate immunity and determinants of adaptive immunity, are not well defined in these target tissues. Using immunohistochemistry, dendritic cells expressing Langerin (CD207(+)), a lectin known to bind and internalize HIV-1, were detected in the periphery of colonic glands and sparsely scattered in the submucosa similarly in colorectal mucosa. This cell type, well known in skin, has generally not been reported in colonic/rectal mucosa. Unexpectedly, the largest APC population observed was a macrophage-like population expressing the well-characterized tissue macrophage markers CD68 and CD163. Confocal microscopy of these cells revealed colocalization of CD209 (DC-SIGN), a presumed dendritic cell marker believed to facilitate HIV-1 transmission, but not other dendritic cell markers. These results show evidence of the unconfirmed presence of Langerhans cells in colorectal mucosa and a predominance of macrophage-like APCs that express CD209 (DC-SIGN). These findings define potential target cells in the pathogenesis of HIV-1 transmission, which may have key implications for the study of early transmission events in normal colorectal mucosa, as well as other infectious diseases and primary immune diseases involving the gut.

Multiplex immunoassay of lower genital tract mucosal fluid from women attending an urban STD clinic shows broadly increased IL1ß and lactoferrin

Background

More than one million new cases of sexually transmitted diseases (STDs) occur each day. The immune responses and inflammation induced by STDs and other frequent non-STD microbial colonizations (i.e. Candida and bacterial vaginosis) can have serious pathologic consequences in women including adverse pregnancy outcomes, infertility and increased susceptibility to infection by other pathogens. Understanding the types of immune mediators that are elicited in the lower genital tract by these infections/colonizations can give important insights into the innate and adaptive immune pathways that are activated and lead to strategies for preventing pathologic effects.

Methodology/Principal Findings

32 immune mediators were measured by multiplexed immunoassays to assess the immune environment of the lower genital tract mucosa in 84 women attending an urban STD clinic. IL-3, IL-1ß, VEGF, angiogenin, IL-8, ß2Defensin and ß3Defensin were detected in all subjects, Interferon-α was detected in none, while the remaining mediators were detected in 40% to 93% of subjects. Angiogenin, VEGF, FGF, IL-9, IL-7, lymphotoxin-α and IL-3 had not been previously reported in genital mucosal fluid from women. Strong correlations were observed between levels of TNF-α, IL-1ß and IL-6, between chemokines IP-10 and MIG and between myeloperoxidase, IL-8 and G-CSF. Samples from women with any STD/colonization had significantly higher levels of IL-8, IL-3, IL-7, IL-1ß, lactoferrin and myeloperoxidase. IL-1ß and lactoferrin were significantly increased in gonorrhea, Chlamydia, cervicitis, bacterial vaginosis and trichomoniasis.

Conclusions/Significance

These studies show that mucosal fluid in general appears to be an environment that is rich in immune mediators. Importantly, IL-1ß and lactoferrin are biomarkers for STDs/colonizations providing insights into immune responses and pathogenesis at this mucosal site.

Methodological issues in sampling the local immune system of the female genital tract in the context of HIV prevention trials

The spread of HIV continues unabated in the most vulnerable populations of the world. HIV prevention methods, such as a vaginal microbicide, a mucosal vaccine, pre-exposure prophylaxis or a vaccine, are urgently needed in the fight against new infections. We must make a commitment to supporting innovative research and product design, so that one or more of these products provide a halt to the spread of HIV. Above all, these products should be proven to be safe and not negatively disturb the local immune system in a way that facilitates or enhances heterosexual transmission of HIV. HIV specific and non specific cellular and humoral local vaginal immunity must be assessed in clinical trials when testing prevention products for safety or efficacy. A proven, well-documented and standardized sampling strategy will provide high quality data to be able to assess both safety and local immune responses. In this paper, we will discuss methods for vaginal immunology sampling in the context of clinical trials.

Potent and broad neutralizing activity of a single chain antibody fragment against cell-free and cell-associated HIV-1

Several human monoclonal antibodies (hmAbs) exhibit relatively potent and broad neutralizing activity against HIV-1, but there has not been much success in using them as potential therapeutics. We have previously hypothesized and demonstrated that small engineered antibodies can target highly conserved epitopes that are not accessible by full-size antibodies. However, their potency has not been comparatively evaluated with known HIV-1-neutralizing hmAbs against large panels of primary isolates. We report here the inhibitory activity of an engineered single chain antibody fragment (scFv), m9, against several panels of primary HIV-1 isolates from group M (clades A-G) using cell-free and cell-associated virus in cell line-based assays. M9 was much more potent than scFv 17b, and more potent than or comparable to the best-characterized broadly neutralizing hmAbs IgG(1) b12, 2G12, 2F5 and 4E10. It also inhibited cell-to-cell transmission of HIV-1 with higher potency than enfuvirtide (T-20, Fuzeon). M9 competed with a sulfated CCR5 N-terminal peptide for binding to gp120-CD4 complex, suggesting an overlapping epitope with the coreceptor binding site. M9 did not react with phosphatidylserine (PS) and cardiolipin (CL), nor did it react with a panel of autoantigens in an antinuclear autoantibody (ANA) assay. We further found that escape mutants resistant to m9 did not emerge in an immune selection assay. These results suggest that m9 is a novel anti-HIV-1 candidate with potential therapeutic or prophylactic properties, and its epitope is a new target for drug or vaccine development.

Microbicides and HIV prevention: lessons from the past, looking to the future

PURPOSE OF REVIEW

This review provides an update on developments in HIV microbicide research in the light of recent phase 3 efficacy studies and discusses how lessons learnt from early generation microbicide candidates can assist the development of future agents.

RECENT FINDINGS

Results of an interim analysis of a phase 3 trial suggested that cellulose sulfate increased the risk of HIV acquisition compared with placebo. Carraguard, SAVVY and Buffergel also failed to show any HIV protection in human efficacy trials. Recent research has focused on elucidating the reasons behind these failures as well as improving the assessment of safety and efficacy for the next generation of microbicide candidates. PRO 2000 0.5% gel is the only HIV microbicide candidate for which there are preliminary data suggesting efficacy in women. Antiretroviral agents and entry inhibitors may provide the key in the future to developing an effective HIV microbicide both for vaginal and rectal use.

SUMMARY

Development of a protective 'barrier' which can be controlled by the receptive partner independent of time of coitus remains a key goal in HIV prevention. A gel or ring-delivered combination of active anti-HIV agents may prove more efficacious than a single agent alone. Challenges in evaluating and manufacturing new candidates must be overcome before a well tolerated, effective, acceptable and affordable microbicide can be produced.

Human defensins and cytokines in vaginal lavage fluid of women with bacterial vaginosis

OBJECTIVE

To measure the concentrations of interferon gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, human beta-defensin 2 (HBD-2), and human defensin 5 (HD-5) in the vaginal lavage fluid (VLF) of healthy women and women with bacterial vaginosis (BV).

METHODS

VLF samples were obtained from 73 women with BV, 15 women with intermediate vaginal flora, 33 healthy women with vaginal pH greater than or equal to 4.5, and a control group of 39 healthy women with vaginal pH less than 4.5. The concentrations of IFN-gamma, IL-2, IL-4, IL-5, HBD-2, and HD-5 were measured using enzyme-linked immunosorbent assay kits.

RESULTS

Concentrations of HBD-2 and HD-5 in the VLF of women with BV were significantly higher than in the control group (P<0.05). IL-4 concentration was significantly lower in the VLF of women with BV than in the control group (P<0.05).

CONCLUSIONS

HBD-2 and HD-5 may be involved in defending against invasion by BV-related microorganisms and the decrease in IL-4 concentration may increase susceptibility to BV.

Amphipathic DNA polymers exhibit antiherpetic activity in vitro and in vivo

Phosphorothioated oligonucleotides have a sequence-independent antiviral activity as amphipathic polymers (APs). The activity of these agents against herpesvirus infections in vitro and in vivo was investigated. The previously established sequence-independent, phosphorothioation-dependent antiviral activity of APs was confirmed in vitro by showing that a variety of equivalently sized homo- and heteropolymeric AP sequences were similarly active against herpes simplex virus type 1 (HSV-1) infection in vitro compared to the 40mer degenerate parent compound (REP 9), while the absence of phosphorothioation resulted in the loss of antiviral activity. In addition, REP 9 demonstrated in vitro activity against a broad spectrum of other herpesviruses: HSV-2 (50% effective concentration [EC(50)], 0.02 to 0.06 microM), human cytomegalovirus (EC(50), 0.02 to 0.13 microM), varicella zoster virus (EC(50), <0.02 microM), Epstein-Barr virus (EC(50), 14.7 microM) and human herpesvirus types 6A/B (EC(50), 2.9 to 10.2 microM). The murine microbicide model of genital HSV-2 was then used to evaluate in vivo activity. REP 9 (275 mg/ml) protected 75% of animals from disease and infection when provided 5 or 30 min prior to vaginal challenge. When an acid-stable analog (REP 9C) was used, 75% of mice were protected when treated with 240 mg/ml 5 min prior to infection (P < 0.001), while a lower dose (100 mg/ml) protected 100% of the mice (P < 0.001). The acid stable REP 9C formulation also provided protection at 30 min (83%, P < 0.001) and 60 min (50%, P = 0.07) against disease. These observations suggest that APs may have microbicidal activity and potential as broad-spectrum antiherpetic agents and represent a novel class of agents that should be studied further.