The number and distribution of immune cells in the cervicovaginal mucosa remain constant throughout the menstrual cycle of rhesus macaques

Repeated semen exposure decreases cervicovaginal SIVmac251 infection in rhesus macaques

Semen is the vehicle for virion dissemination in the female reproductive tract (FRT) in male-to-female HIV transmission. Recent data suggests that higher frequency semen exposure is associated with activation of anti-HIV mechanisms in HIV negative sex workers. Here, we use a non-human primate (NHP) model to show that repeated vaginal exposure to semen significantly reduces subsequent infection by repeated low-dose vaginal SIVmac251 challenge. Repeated semen exposures result in lower CCR5 expression in circulating CD4+ T-cells, as well as higher expression of Mx1 (in correlation with IFNε expression) and FoxP3 in the cervicovaginal mucosa, and increased infiltration of CD4+ T-cells. Establishing in vivo evidence of competing effects of semen on transmission impacts our basic understanding of what factors may determine HIV infectivity in humans. Our results clearly indicate that repeated semen exposure can profoundly modulate the FRT microenvironment, paradoxically promoting host resistance against HIV acquisition.

Epithelium-innate immune cell axis in mucosal responses to SIV

In the SIV (simian immunodeficiency virus)-rhesus macaque model of HIV-1 (human immunodeficiency virus type I) transmission to women, one hallmark of the mucosal response to exposure to high doses of SIV is CD4 T-cell recruitment that fuels local virus expansion in early infection. In this study, we systematically analyzed the cellular events and chemoattractant profiles in cervical tissues that precede CD4 T-cell recruitment. We show that vaginal exposure to the SIV inoculum rapidly induces chemokine expression in cervical epithelium including CCL3, CCL20, and CXCL8. The chemokine expression is associated with early recruitment of macrophages and plasmacytoid dendritic cells that are co-clustered underneath the cervical epithelium. Production of chemokines CCL3 and CXCL8 by these cells in turn generates a chemokine gradient that is spatially correlated with the recruitment of CD4 T cells. We further show that the protection of SIVmac239Δnef vaccination against vaginal challenge is correlated with the absence of this epithelium-innate immune cell-CD4 T-cell axis response in the cervical mucosa. Our results reveal a critical role for cervical epithelium in initiating early mucosal responses to vaginal infection, highlight an important role for macrophages in target cell recruitment, and provide further evidence of a paradoxical dampening effect of a protective vaccine on these early mucosal responses.

Increases in Endogenous or Exogenous Progestins Promote Virus-Target Cell Interactions within the Non-human Primate Female Reproductive Tract

Currently, there are mounting data suggesting that HIV-1 acquisition in women can be affected by the use of certain hormonal contraceptives. However, in non-human primate models, endogenous or exogenous progestin-dominant states are shown to increase acquisition. To gain mechanistic insights into this increased acquisition, we studied how mucosal barrier function and CD4+ T-cell and CD68+ macrophage density and localization changed in the presence of natural progestins or after injection with high-dose DMPA. The presence of natural or injected progestins increased virus penetration of the columnar epithelium and the infiltration of susceptible cells into a thinned squamous epithelium of the vaginal vault, increasing the likelihood of potential virus interactions with target cells. These data suggest that increasing either endogenous or exogenous progestin can alter female reproductive tract barrier properties and provide plausible mechanisms for increased HIV-1 acquisition risk in the presence of increased progestin levels.

Comparison of Follicular and Luteal Phase Mucosal Markers of HIV Susceptibility in Healthy Women

The purpose of this study was to evaluate differences in vaginal immune cell populations, vaginal tissue gene expression, antimicrobial activity of the cervicovaginal (CV) lavage (CVL), vaginal flora, and p24 antigen production from CV tissues after ex vivo human immunodeficiency virus (HIV) infection between follicular (FOL) and luteal (LUT) phases of the menstrual cycle. CV tissue biopsies, CV secretions, and blood samples were obtained as part of two longitudinal clinical trials of healthy women (CONRAD D11-119 and A12-124 studies). Participants (n = 39) were HIV-seronegative women not using exogenous hormone supplementation, with normal menstrual cycles, who were screened to exclude sexually transmitted and reproductive tract infections. Serum levels of estradiol and progesterone were significantly higher in the LUT versus the FOL phase of the menstrual cycle. Controlling for race, reported contraceptive use/sexual practices, and clinical trial, we found no differences in vaginal tissue immune cell populations and activation status, transcriptomes, inhibition of HIV, herpes simplex virus type 2 and Escherichia coli by the CVL, vaginal pH or Nugent score, or production of p24 antigen after ex vivo infection by HIV-1BaL between CV samples obtained in the FOL phase versus the LUT phase of the menstrual cycle. There were no significant correlations between serum estradiol and progesterone levels and CV endpoints. The hypothesis that the LUT phase of the menstrual cycle represents a more vulnerable stage for mucosal infection with HIV was not supported by data from samples obtained from the lower genital tract (ectocervix and vagina) from these two clinical trials.

Lymphatic Dissemination of Simian Immunodeficiency Virus after Penile Inoculation

The human immunodeficiency virus (HIV) is primarily transmitted by heterosexual contact, and approximately equal numbers of men and women worldwide are infected with the virus. Understanding the biology of HIV acquisition and dissemination in men exposed to the virus by insertive penile intercourse is likely to help with the rational design of vaccines that can limit or prevent HIV transmission. To characterize the target cells and dissemination pathways involved in establishing systemic simian immunodeficiency virus (SIV) infection, we necropsied male rhesus macaques at 1, 3, 7, and 14 days after penile SIV inoculation and quantified the levels of unspliced SIV RNA and spliced SIV RNA in tissue lysates and the number of SIV RNA-positive cells in tissue sections. We found that penile (glans, foreskin, coronal sulcus) T cells and, to a lesser extent, macrophages and dendritic cells are primary targets of infection and that SIV rapidly reaches the regional lymph nodes. At 7 days after inoculation, SIV had disseminated to the blood, systemic lymph nodes, and mucosal lymphoid tissues. Further, at 7 days postinoculation (p.i.), spliced SIV RNA levels were the highest in the genital lymph nodes, indicating that this is the site where the infection is initially amplified. By 14 days p.i., spliced SIV RNA levels were high in all tissues, but they were the highest in the gastrointestinal tract, indicating that the primary site of virus replication had shifted from the genital lymph nodes to the gut. The stepwise pattern of virus replication and dissemination described here suggests that vaccine-elicited immune responses in the genital lymph nodes could help prevent infection after penile SIV challenge.

IMPORTANCE

To be the most effective, vaccines should produce antiviral immune responses in the anatomic sites of virus replication. Thus, understanding the path taken by HIV from the mucosal surfaces, which are the site of virus exposure, to the deeper tissues where the virus replicates will provide insight into where AIDS vaccines should produce immunity to be the most effective. In this study, we determined that, by day 7 after penile inoculation, SIV has moved first to the inguinal lymph nodes and replicates to high levels. Although the virus is widely disseminated to other tissues by day 7, replication is largely limited to the inguinal lymph nodes. The step-by-step movement of SIV from penile mucosal surfaces to the draining lymph nodes may allow an HIV vaccine that produces immunity in these lymph nodes to block HIV from establishing an infection in an exposed person.

A long-acting integrase inhibitor protects female macaques from repeated high-dose intravaginal SHIV challenge

Long-acting GSK1265744 (GSK744 LA) is a strand transfer inhibitor of the HIV/SIV (simian immunodeficiency virus) integrase and was shown to be an effective preexposure prophylaxis (PrEP) agent in a low-dose intrarectal SHIV (simian-human immunodeficiency virus) rhesus macaque challenge model. We examined the pharmacokinetics and efficacy of GSK744 LA as PrEP against repeat high-dose intravaginal SHIV challenge in female rhesus macaques treated with Depo-Provera (depot medroxyprogesterone acetate), which promotes viral transmission vaginally. When Depo-Provera-treated female rhesus macaques were dosed with GSK744 LA (50 mg/kg) monthly, systemic and tissue drug concentrations were lower than previously observed in male rhesus macaques. GSK744 concentrations were fivefold lower on average in cervical tissues than in rectal tissues. Eight female rhesus macaques were treated with GSK744 LA at week 0, and four female rhesus macaques served as controls. All animals received a high-dose challenge of SHIV162P3 at week 1. No infection was detected in GSK744 LA-treated rhesus macaques, whereas viremia was detected 1 to 2 weeks after SHIV challenge in all control animals. The GSK744 LA-treated rhesus macaques were given a second administration of drug at week 4 and further challenged at weeks 5 and 7. GSK744 LA treatment protected six of eight female rhesus macaques against three high-dose SHIV challenges, whereas all control animals became infected after the first challenge (P = 0.0003, log-rank test). These results support further clinical development of GSK744 LA for PrEP.

Preclinical evaluation of the immunomodulatory lymphocyte trafficking drug FTY720 for HIV prevention in the female genital mucosa of macaques

FTY720 has been shown to reduce inflammatory cytokines and immune cells in the genital mucosa of macaques. This pilot study examined the ability of FTY720 to inhibit HIV acquisition. Systemic treatment with FTY720 failed to prevent or delay vaginal SHIV transmission.

A quantitative multiplex nuclease protection assay reveals immunotoxicity gene expression profiles in the rabbit model for vaginal drug safety evaluation

Any vaginal product that alters the mucosal environment and impairs the immune barrier increases the risk of sexually transmitted infections, especially HIV infection, which thrives on mucosal damage and inflammation. The FDA-recommended rabbit vaginal irritation (RVI) model serves as a first line selection tool for vaginal products; however, for decades it has been limited to histopathology scoring, insufficient to select safe anti-HIV microbicides. In this study we incorporate to the RVI model a novel quantitative nuclease protection assay (qNPA) to quantify mRNA levels of 25 genes representing leukocyte differentiation markers, toll-like receptors (TLR), cytokines, chemokines, epithelial repair, microbicidal and vascular markers, by designing two multiplex arrays. Tissue sections were obtained from 36 rabbits (6 per treatment arm) after 14 daily applications of a placebo gel, saline, 4% nonoxynol-9 (N-9), and three combinations of the anti-HIV microbicides tenofovir (TFV) and UC781 in escalating concentrations (highest: 10% TFV+2.5%UC781). Results showed that increased expression levels of toll-like receptor (TLR)-4, interleukin (IL)-1β, CXCL8, epithelial membrane protein (EMP)-1 (P<0.05), and decreased levels of TLR2 (P<0.05), TLR3 and bactericidal permeability increasing protein (BPI) (P<0.001) were associated with cervicovaginal mucosal alteration (histopathology). Seven markers showed a significant linear trend predicting epithelial damage (up with CD4, IL-1β, CXCL8, CCL2, CCL21, EMP1 and down with BPI). Despite the low tissue damage RVI scores, the high-dose microbicide combination gel caused activation of HIV host cells (SLC and CD4) while N-9 caused proinflammatory gene upregulation (IL-8 and TLR4) suggesting a potential for increasing risk of HIV via different mechanisms depending on the chemical nature of the test product.

Non-human primate models of hormonal contraception and HIV

PROBLEM

Recent concerns that hormonal contraception (HC) may increase risk of HIV acquisition has led to keen interest in using non-human primates (NHP) to understand the underlying mechanism and the magnitude of the risk. This is, in part, because some experiments which would be difficult or logistically impossible in women are more easily conducted in NHP.

METHOD OF STUDY

NHP models of HIV can inform HIV acquisition and pathogenesis research and identify and evaluate biomedical preventions and treatments for HIV/AIDS. Widely used species include rhesus, pigtail, and cynomolgous macaques.

RESULTS

This paper reviews past, current and proposed NHP research around the intersection of HIV and HC.

CONCLUSION

NHP research may lead to the identification of hormonally regulated biomarkers that correlate with HIV-acquisition risk, to a ranking of existing or next-generation HC along an HIV-acquisition risk profile, and inform research around new biomedical preventions for HIV.

Mucosal immunology of HIV infection

Recent advances in the immunology, pathogenesis, and prevention of human immunodeficiency virus (HIV) infection continue to reveal clues to the mechanisms involved in the progressive immunodeficiency attributed to infection, but more importantly have shed light on the correlates of immunity to infection and disease progression. HIV selectively infects, eliminates, and/or dysregulates several key cells of the human immune system, thwarting multiple arms of the host immune response, and inflicting severe damage to mucosal barriers, resulting in tissue infiltration of 'symbiotic' intestinal bacteria and viruses that essentially become opportunistic infections promoting systemic immune activation. This leads to activation and recruitment or more target cells for perpetuating HIV infection, resulting in persistent, high-level viral replication in lymphoid tissues, rapid evolution of resistant strains, and continued evasion of immune responses. However, vaccine studies and studies of spontaneous controllers are finally providing correlates of immunity from protection and disease progression, including virus-specific CD4(+) T-cell responses, binding anti-bodies, innate immune responses, and generation of antibodies with potent antibody-dependent cell-mediated cytotoxicity activity. Emerging correlates of immunity indicate that prevention of HIV infection may be possible through effective vaccine strategies that protect and stimulate key regulatory cells and immune responses in susceptible hosts. Furthermore, immune therapies specifically directed toward boosting specific aspects of the immune system may eventually lead to a cure for HIV-infected patients.

Phenotype and functionality of CD4+ and CD8+ T cells in the upper reproductive tract of healthy premenopausal women

PROBLEM

The goal of this study was to investigate the phenotype and functional responsiveness of CD4(+) and CD8(+) T-cells in the upper reproductive tract of healthy premenopausal women. The lower reproductive tract is frequently studied as a site of sexually transmitted infections; however, the upper reproductive tract may also be a portal of entry and dissemination for pathogens, including HIV-1.

METHOD OF STUDY

Endometrial biopsy, endocervical curettage, cytobrush, and blood were collected during mid-luteal phase from 23 healthy women. T-cells were isolated and analyzed by flow cytometry.

RESULTS

As compared with their counterparts in blood, endometrial and endocervical T-cells had enhanced CCR5 expression, and were enriched for activated, effector memory cells. Endometrial T-cells were more responsive to polyclonal stimuli, producing a broad range of cytokines and chemokines.

CONCLUSION

These findings underscore the responsiveness of endometrial T-cells to stimulation, and reveal their activated phenotype. These findings also suggest susceptibility of the upper reproductive tract to HIV-1 infection.

Productive HIV-1 infection of human cervical tissue ex vivo is associated with the secretory phase of the menstrual cycle

Cervical tissue explants (CTEs) from 22 HIV-1 seronegative women were exposed to R5 HIV-1 ex vivo. Eight CTEs were productively infected in terms of HIV-1 p24Gag release in culture supernatants, whereas 14 were not. Nonetheless, both accumulation of HIV-1gag DNA and of p24Gag(+) CD4(+) T cells and macrophages occurred in both productive and, at lower levels, in nonproductive CTEs. Nonproductive CTEs differed from productive CTEs for higher secretion of C-C motif chemokine ligand 3 (CCL3) and CCL5. A post-hoc analysis revealed that all productive CTEs were established from women in their secretory phase of the menstrual cycle, whereas nonproductive CTEs were derived from women either in their secretory (28%) or proliferative (36%) menstrual cycle phases or with an atrophic endometrium (36%). Thus, our results support the epidemiological observation that sexual HIV-1 transmission from males to women as well as from women to men is more efficient during their secretory phase of the menstrual cycle.

Depot medroxyprogesterone acetate increases immune cell numbers and activation markers in human vaginal mucosal tissues

The relationship between exogenous contraceptive hormones and permissiveness of the female genital tract to human immunodeficiency virus type 1 (HIV-1) is the subject of renewed debate. To better characterize the effect of depot medroxyprogesterone acetate (DMPA) on HIV-1 cellular targets and epithelial integrity in the vagina, we compared leukocyte populations, markers of activation and proliferation, and the density of intercellular junctional proteins in the vaginal epithelium of women during the follicular and luteal phases of the menstrual cycle and approximately 12 weeks after receiving a DMPA injection. This prospective cohort study involved 15 healthy women. Vaginal biopsies were obtained in the follicular and luteal phases of the menstrual cycle, and approximately 12 weeks following a 150-mg intramuscular injection of DMPA. Leukocyte populations, activation phenotype, and epithelial tight junction and adherens proteins were evaluated by immunohistochemistry. After receiving DMPA, the numbers of CD45, CD3, CD8, CD68, HLA-DR, and CCR5 bearing immune cells were significantly (p<0.05) increased in vaginal tissues, compared to the follicular and/or luteal phases of untreated cycles. There were no significant differences in immune cell populations between the follicular and luteal phases of the control cycle. There were also no statistically significant differences in epithelial thickness and density of epithelial tight junction and adherens proteins among the follicular, luteal, and post-DMPA treatment sampling points. In this pilot study, vaginal immune cell populations were significantly altered by exogenous progesterone, resulting in increased numbers of T cells, macrophages, and HLA-DR- and CCR5-positive cells.

Spontaneous cervicovaginal lesions and immune cell infiltrates in nonhuman primates

Nonhuman primates, particularly rhesus macaques (Macaca mulatta), provide important model systems for studying human reproductive infectious diseases such as human immunodeficiency virus, human papillomavirus, and Chlamydia spp. An understanding of the spectrum of spontaneous cervical disease provides essential context for interpreting experimental disease outcomes in the female reproductive tract. This retrospective study characterizes the incidence of inflammatory and/or proliferative cervicovaginal lesions seen over a 14-year period in a multispecies nonhuman primate colony, focusing on rhesus macaques. The most common observations included a spectrum of lymphocytic accumulation from within normal limits to lymphoplasmacytic cervicitis, and suppurative inflammation with occasional squamous metaplasia or polyp formation. These inflammatory spectra frequently occurred in the context of immunosuppression following experimental simian immunodeficiency virus (SIV) infection. Cervical neoplasias were uncommon and included leiomyomas and carcinomas. Cervical sections from 13 representative cases, with an emphasis on proliferative and dysplastic lesions, were surveyed for leukocyte infiltration, abnormal epithelial proliferation, and the presence of papillomavirus antigens. Proliferative lesions showed sporadic evidence of spontaneous papillomavirus infection and variable immune cell responses. These results underscore the importance of pre screening potential experimental animals for the presence of preexisting reproductive tract disease, and the consideration of normal variability within cycling reproductive tracts in interpretation of cervical lesions.

HIV transmission

HIV-1 is transmitted by sexual contact across mucosal surfaces, by maternal-infant exposure, and by percutaneous inoculation. For reasons that are still incompletely understood, CCR5-tropic viruses (R5 viruses) are preferentially transmitted by all routes. Transmission is followed by an orderly appearance of viral and host markers of infection in the blood plasma. In the acute phase of infection, HIV-1 replicates exponentially and diversifies randomly, allowing for an unambiguous molecular identification of transmitted/founder virus genomes and a precise characterization of the population bottleneck to virus transmission. Sexual transmission of HIV-1 most often results in productive clinical infection arising from a single virus, highlighting the extreme bottleneck and inherent inefficiency in virus transmission. It remains to be determined if HIV-1 transmission is largely a stochastic process whereby any reasonably fit R5 virus can be transmitted or if there are features of transmitted/founder viruses that facilitate their transmission in a biologically meaningful way. Human tissue explant models of HIV-1 infection and animal models of SIV/SHIV/HIV-1 transmission, coupled with new challenge virus strains that more closely reflect transmitted/founder viruses, have the potential to elucidate fundamental mechanisms in HIV-1 transmission relevant to vaccine design and other prevention strategies.

Understanding factors that modulate HIV infection at the female genital tract mucosae for the rationale design of microbicides

Women are now becoming the pivot of the epidemiological spread of HIV infection worldwide, especially in developing countries. Therefore, research to develop an efficient microbicide is now a priority for the prevention of HIV-1 acquisition in exposed women. However, recent disappointing failures in microbicide clinical trials revealed major gaps in basic and applied knowledge that hinder the development of effective microbicide formulations. Indeed, the inhibitory power of microbicide molecules may be affected by several physiological and immunological factors present in male and female genital tracts. Furthermore, mucosal crossing of HIV-1 to increase the ability to reach the submucosal target cells (macrophages, lymphocytes, and dendritic cells) may be modulated by supraepithelial factors such as seminal complement components (opsonized HIV-1), by epithelial factors released in the submucosal microenvironment such as antimicrobial soluble factors, cytokines, and chemokines, and by potent intraepithelial and submucosal innate immunity. The design of vaginal microbicide formulations should take into account an understanding of the intimate mechanisms involved in the crossing of HIV through the female genital mucosae, in the context of a mixture of both male and female genital fluids.

Expression of CCR5, CXCR4 and DC-SIGN in Cervix of HIV-1 Heterosexually Infected Mexican Women

BACKGROUND

A number of studies have demonstrated that receptor and co-receptor expression levels which may affect viral entry, promoting cervical HIV infection. The aim was to evaluate the expression levels of CCR5, CXCR4and DC-SIGN mRNA in a sample of heterosexually HIV infected Mexican women.

METHODS

We enrolled twenty-six HIV heterosexual infected women attending a local infectious diseases medical unit.RNA was isolated from the cervix and gene expression analysis was performed using real-time PCR.

RESULTS

Expression rates for mRNA of CCR5 (median 1.82; range 0.003-2934) were higher than those observed for CXCR4 (0.79; 0.0061-3312) and DC-SIGN (0.33; 0.006-532) receptors (p < 0.05). A high correlation was found between the mRNA expression levels of these three receptors (rs = 0.52 to 0.85, p < 0.01).

CONCLUSION

Levels of expression of the tested chemokine receptors in the cervix are different from each other and alsovary from woman to woman, and seem to support the suggestion that chemokine receptor expression in genital tissues may be playing a role in the HIV transmission.

Live-attenuated lentivirus immunization modulates innate immunity and inflammation while protecting rhesus macaques from vaginal simian immunodeficiency virus challenge

Immunization with attenuated lentiviruses is the only reliable method of protecting rhesus macaques (RM) from vaginal challenge with pathogenic simian immunodeficiency virus (SIV). CD8(+) lymphocyte depletion prior to SIVmac239 vaginal challenge demonstrated that a modest, Gag-specific CD8(+) T cell response induced by immunization with simian-human immunodeficiency virus 89.6 (SHIV89.6) protects RM. Although CD8(+) T cells are required for protection, there is no anamnestic expansion of SIV-specific CD8(+) T cells in any tissues except the vagina after challenge. Further, SHIV immunization increased the number of viral target cells in the vagina and cervix, suggesting that the ratio of target cells to antiviral CD8(+) T cells was not a determinant of protection. We hypothesized that persistent replication of the attenuated vaccine virus modulates inflammatory responses and limits T cell activation and expansion by inducing immunoregulatory T cell populations. We found that attenuated SHIV infection decreased the number of circulating plasmacytoid dendritic cells, suppressed T cell activation, decreased mRNA levels of proinflammatory mediators, and increased mRNA levels of immunoregulatory molecules. Three days after SIV vaginal challenge, SHIV-immunized RM had significantly more T regulatory cells in the vagina than the unimmunized RM. By day 14 postchallenge, immune activation and inflammation were characteristic of unimmunized RM but were minimal in SHIV-immunized RM. Thus, a modest vaccine-induced CD8(+) T cell response in the context of immunoregulatory suppression of T cell activation may protect against vaginal HIV transmission.

Identification of immune cells by flow cytometry in vaginal lavages from women with vulvovaginitis and normal microflora

PROBLEM

  The extent of the vaginal immune response is not fully determined. The purpose of this study was to evaluate the vaginal immune cells from women with vulvovaginitis (VV).

METHOD OF STUDY

A total of 142 volunteers diagnosed with bacterial vaginosis (BV), vulvovaginal candidiasis (VC), and BV associated with VC or normal microflora were sampled to evaluate the immune cells by flow cytometry. The immune cells were obtained by vaginal lavage and labeled with fluorochrome-conjugated monoclonal antibodies to identify neutrophil granulocytes, macrophages, CD4(+) and CD8(+) T lymphocytes, B lymphocytes, and NK lymphocytes.

RESULTS

Neutrophil granulocytes were present in 84.6% of samples among the leukocyte populations. Considering samples in which neutrophils were present, the mean percentage of neutrophil granulocytes was significantly higher in women with VC than BV and normal microflora and was significantly lower in women with BV than normal microflora. Macrophages and lymphocytes were present in a lower percentage of samples. The mean percentage of CD4(+) T lymphocytes in vaginal lavages was significantly higher in VC and BV compared with women with normal microflora.

CONCLUSIONS

Neutrophils were the predominant leukocytes and were associated with VC and inversely with BV. CD4(+) T lymphocytes were associated with both VC and BV.

A limited number of simian immunodeficiency virus (SIV) env variants are transmitted to rhesus macaques vaginally inoculated with SIVmac251

Single-genome amplification (SGA) and sequencing of HIV-1 RNA in plasma of acutely infected humans allows the identification and enumeration of transmitted/founder viruses responsible for productive systemic infection. Use of this strategy as a means for identifying transmitted viruses suggested that intrarectal simian immunodeficiency virus (SIV) inoculation of macaques recapitulates key features of human rectal infection. However, no studies have used the SGA strategy to identify vaginally transmitted virus(es) in macaques or to determine how early SIV diversification in vaginally infected animals compares with HIV-1 in humans. We used SGA to amplify 227 partial env sequences from a SIVmac251 challenge stock and from seven rhesus macaques at the earliest plasma viral RNA-positive time point after low- and high-dose intravaginal inoculation. Sequences were analyzed phylogenetically to determine the relationship of transmitted/founder viruses within and between each animal and the challenge stock. In each animal, discrete low-diversity env sequence lineages were evident, and these coalesced phylogenetically to identical or near-identical env sequences in the challenge stock, thus confirming the validity of the SGA sequencing and modeling strategy for identifying vaginally transmitted SIV. Between 1 and 10 viruses were responsible for systemic infection, similar to humans infected by sexual contact, and the set of viruses transmitted to the seven animals studied represented the full genetic constellation of the challenge stock. These findings recapitulate many of the features of sexual HIV-1 transmission in women. Furthermore, the SIV rhesus macaque model can be used to understand the factors that influence the transmission of single versus multiple SIV variants.

Targeting early infection to prevent HIV-1 mucosal transmission

Measures to prevent sexual mucosal transmission of human immunodeficiency virus (HIV)-1 are urgently needed to curb the growth of the acquired immunodeficiency syndrome (AIDS) pandemic and ultimately bring it to an end. Studies in animal models and acute HIV-1 infection reviewed here reveal potential viral vulnerabilities at the mucosal portal of entry in the earliest stages of infection that might be most effectively targeted by vaccines and microbicides, thereby preventing acquisition and averting systemic infection, CD4 T-cell depletion and pathologies that otherwise rapidly ensue.

Sex steroid hormones, hormonal contraception, and the immunobiology of human immunodeficiency virus-1 infection

Worldwide, an increasing number of women use oral or injectable hormonal contraceptives. However, inadequate information is available to aid women and health care professionals in weighing the potential risks of hormonal contraceptive use in individuals living with HIV-1 or at high risk of infection. Numerous epidemiological studies and challenge studies in a rhesus macaque model suggest that progesterone-based contraceptives increase the risk of HIV-1 infection in humans and simian immunodeficiency virus (SIV) infection in macaques, accelerate disease progression, and increase viral shedding in the genital tract. However, because several other studies in humans have not observed any effect of exogenously administered progesterone on HIV-1 acquisition and disease progression, the issue continues to be a topic of intense research and ongoing discussion. In contrast to progesterone, systemic or intravaginal treatment with estrogen efficiently protects female rhesus macaques against the transmission of SIV, likely by enhancing the natural protective properties of the lower genital tract mucosal tissue. Although the molecular and cellular mechanisms underlying the effect of sex steroid hormones on HIV-1 and SIV acquisition and disease progression are not well understood, progesterone and estrogen are known to regulate a number of immune mechanisms that may exert an effect on retroviral infection. This review summarizes current knowledge of the effects of various types of sex steroid hormones on immune processes involved in the biology of HIV-1 infection.

Memory T cells in Rhesus macaques

The Rhesus macaque (Macaca mulatta) is one of the best studied species of Old World monkeys. DNA sequencing of the entire Rhesus macaque genome, completed in 2007, has demonstrated that humans and macaques share about 93% of their nucleotide sequence. Rhesus macaques have been widely used for medical research including drug testing, neurology, behavioral and cognitive science, reproduction, xenotransplantation and genetics. Because of the Rhesus macaque's sensitivity to bacteria, parasites and viruses that cause similar disease in humans, these animals represent an excellent model to study infectious diseases. The recent pandemic of HIV and the discovery of SIV, a lentivirus genetically related to HIV Type 1 that causes AIDS in Rhesus macaques, have prompted the development of reagents that can be used to study innate and adaptive immune responses in macaques at the single cell level. This review will focus on the distribution of memory cells in the different immunologic compartments of Rhesus macaques. In addition, the strategies available to manipulate memory cells in Rhesus macaques to understand their trafficking and function will be discussed. Emphasis is placed on studies of memory cells in macaques infected with SIV because many studies are available. Lastly, we highlight the usefulness of the Rhesus macaque model in studies related to the aging of the immune system.

Morphologic and Immunohistochemical Features of the Cynomolgus Macaque Cervix

Female macaques serve as an important model for the study of reproductive diseases in women. Here we summarize characteristics of the macaque cervix, with a particular emphasis on the cynomolgus macaque. Key anatomic features include a stratified squamous exocervix, squamocolumnar junction and transformation zone, and glandular endocervix with prominent colliculi. Endocervical eversion occurs with onset of ovarian cycling and regresses to varying degrees based on age, hormonal status, and individual conformation. The cervical epithelium in macaques is highly responsive to estrogens, which induce marked squamous epithelial maturation and glandular hypertrophy. Progestogen effects include further induction of endocervical secretory activity and release of viscous mucus, which functions in both mucosal immunity and fertility regulation. On immunohistochemistry, the squamous cervix shows strong expression of estrogen receptor α, the proliferation marker Ki67/MIB1, and cytokeratin 14, whereas endocervical epithelium strongly expresses estrogen and progesterone receptors and cytokeratins 18 and 19. These patterns of expression are altered in cervical intraepithelial neoplasia, which is a common spontaneous lesion of the macaque cervix associated with specific types of oncogenic papillomaviruses. This report highlights important similarities with human cervix that should be useful for future studies of genital infection, neoplasia, and immunity in the macaque model.

Competing Interests: This article was sponsored by Covance Inc. and Schering-Plough. The author did not declare any other competing interests.

Application of optical coherence tomography for monitoring changes in cervicovaginal epithelial morphology in macaques: potential for assessment of microbicide safety

OBJECTIVES

Safety is a primary concern in the development of topical microbicides. Optical coherence tomography (OCT), a high-resolution, in-depth cross-sectional imaging modality, was utilized in conjunction with colposcopy to assess induced cervicovaginal epithelial changes that may predict product safety.

STUDY DESIGN

OCT and colposcopic images of macaque vaginal and cervical tissues were obtained in excised tissue and in vivo under various conditions, including mechanical injury and nonoxynol-9 treatment.

RESULTS

A scoring system was developed to categorize and quantify the OCT images based on morphologic features that indicate the presence or absence of an intact epithelial layer and inflammation. Using 3 categories (normal, mild to moderately abnormal, and severely abnormal), differences between healthy and injured tissue were apparent on OCT images. Normal images (category 1) had a bilayered structure representative of the epithelium and submucosa. Mild to moderately abnormal images (category 2) had areas of normal and abnormal epithelium. Severely abnormal images (category 3) had complete loss of the epithelium and/or inflammation, with loss of the bilayered structure on OCT.

CONCLUSIONS

OCT is a noninvasive imaging modality complementary to colposcopy. It distinguished between normal and abnormal (or injured) tissue and thus holds promise for safety evaluations of candidate microbicides and other vaginal products.

Changes in vaginal morphology, steroid receptor and natural antimicrobial content following treatment with low-dose mifepristone

BACKGROUND

We have previously shown that the antigestagen mifepristone is contraceptive when given in a daily dose of 5 mg, po. Epidemiological studies suggest that gestagen-only contraceptives may increase the risk of transmission of human immunodeficiency virus (HIV) due to effects on the vaginal defenses to infection. We investigate the effects of mifepristone on vaginal thickness, steroid receptor and natural antimicrobial content and pharmacokinetics of mifepristone.

METHODS

In a pilot study, eight women were given mifepristone 5 mg/day for an average of 33 days. Ovarian function was assessed by measurement of estradiol and progesterone in blood and their metabolites in urine and by serial ultrasound of their ovaries. Vaginal biopsies were collected before (late proliferative) and after taking mifepristone.

RESULTS

All subjects showed a similar pattern of descending serum concentrations of mifepristone. The elimination phase half-life was 18+/-5.1 h (mean+/-SD). Mean Cmax measured at 1 h was 641.7 nmol/L (range, 502-740 nmol/L). All eight women reported amenorrhea for the duration of treatment and seven of eight women showed biochemical and ultrasound evidence of anovulation. There was no significant change in vaginal thickness following treatment [342+/-40 microm pretreatment, 303+/-69 microm posttreatment (mean+/-SEM); p>.05]. Estrogen (ERalpha, ERbeta) and androgen receptor were expressed in both vaginal epithelium and subepithelial stroma, whereas progesterone receptor was expressed predominantly in the subepithelial stroma. There was no change in receptor content and distribution following mifepristone treatment. Natural antimicrobial mRNA [secretory leukocyte protease inhibitor, human beta defensins mRNA (HBD1, HBD2, HBD3, HBD5), granulysin and elafin] was extracted from the vaginal tissues, and the content was unaffected by mifepristone treatment.

CONCLUSION

The absence of changes in vaginal thickness, steroid receptor and natural antimicrobial content and its distribution in this preliminary study suggests that in contrast to other estrogen-free contraceptives, mifepristone is unlikely to be associated with the increased risk of transmission of HIV and other sexually transmitted infections.

Distribution of simian immunodeficiency virus target cells in vaginal tissues of normal rhesus macaques: implications for virus transmission

Most new cases of HIV-1 infection occur as the result of vaginal transmission. Identifying the phenotype and distribution of potential viral target cells in the vagina is important for understanding events in viral transmission and for developing effective prevention strategies. For example, compounds that prevent CD4 or CCR5 binding have been demonstrated recently to prevent vaginal transmission in rhesus macaques, but the expression and distribution of CCR5 has not been examined in the macaque vagina. The objective of this study was to examine the distribution and phenotype of cells and molecules in the vagina of rhesus macaques that may be involved in HIV transmission, including CCR5, CD3, CD4, CD8, CD1a, CD28, CD95, CD123 and HLA-DR. Normal juvenile and adult female rhesus macaques were examined by multicolor immunohistochemistry and flow cytometry. Although both CD4 and CCR5 were observed in the lamina propria, essentially no CD4 or CCR5 expression was detected within the squamous or keratinized layers of the vaginal epithelium. CCR5 expression was higher in the vaginal lamina propria of mature macaques compared to 1-3-year-old juveniles. The vast majority of CD4(+)CCR5(+) lymphocytes in the vagina had a central memory (CD95(+)CD28(+)) phenotype. Numerous CCR5-expressing dendritic cells (CD123(+)) or macrophages (CD68(+)) were observed in the lamina propria, but no CCR5, CD4 or DC-SIGN expression was detectable in the epithelium. Thus, the multiple layers of squamous epithelium normally covering the vaginal mucosa may provide an effective barrier against vaginal HIV-1 transmission. Microbicides that block CD4 or CCR5 expression may act within the deeper layers of the vaginal epithelium rather than on the epithelial surface.

The HIV-1 clade C promoter is particularly well adapted to replication in the gut in primary infection

OBJECTIVE

Coinfection of rhesus macaques with human/simian immunodeficiency virus chimeras harbouring the minimal core-promoter/enhancer elements from HIV-1 clade B, C and E viral prototypes (STR-B, STR-C and STR-E) revealed a remarkable dichotomy in terms of spatio-temporal viral replication. The clade C chimera (STR-C) predominated in primary infection. The present study was aimed at identifying the origin of STR-C plasma viraemia at this infection phase.

DESIGN

By competing isogenic viruses differing only in their promoters, it was possible to identify subtle phenotypical differences in viral replication kinetics and compartmentalization in vivo.

METHODS

Two rhesus macaques were coinfected by the three STR chimeras and the relative colonization of different compartments, particularly blood and stool, was determined for each chimera. Moreover, growth competition experiments in thymic histocultures enriched in interleukin (IL)-7 were performed and relative percentages of chimeras were estimated in supernatants and thymocytes lysates at different time points.

RESULTS

It is demonstrated here that at the peak of primary infection, preferential replication of STR-C was supported by the gut-associated lymphoid tissue (GALT), an IL-7 rich microenvironment. This was shown by the correlation of the RNA viral genotype in blood and stools, compartments directly draining virions from the GALT. Thymic histocultures confirmed that replication of STR-C is particularly susceptible to this cytokine, compared to its STR-B and STR-E counterparts.

CONCLUSIONS

These data show that the GALT cytokine network may well favour HIV-1 clade C replication during primary infection. This could result in enhanced transmission.

The Toll-like receptor 7 (TLR7) agonist, imiquimod, and the TLR9 agonist, CpG ODN, induce antiviral cytokines and chemokines but do not prevent vaginal transmission of simian immunodeficiency virus when applied intravaginally to rhesus macaques

The initial host response to viral infection occurs after Toll-like receptors (TLRs) on dendritic cells (DC) are stimulated by viral nucleic acids (double-stranded RNA, single-stranded RNA) and alpha interferon (IFN-alpha) and IFN-beta are produced. We hypothesized that pharmacologic induction of innate antiviral responses in the cervicovaginal mucosa by topical application of TLR agonists prior to viral exposure could prevent or blunt vaginal transmission of simian immunodeficiency virus (SIV). To test this hypothesis, we treated rhesus monkeys intravaginally with either the TLR9 agonist, CpG oligodeoxynucleotides (ODN), or the TLR7 agonist, imiquimod. Both immune modifiers rapidly induced IFN-alpha and other antiviral effector molecules in the cervicovaginal mucosa of treated animals. However, both CpG ODN and imiquimod also induced proinflammatory cytokine expression in the cervicovaginal mucosa. In the vaginal mucosa of imiquimod-treated monkeys, we documented a massive mononuclear cell infiltrate consisting of activated CD4(+) T cells, DC, and beta-chemokine-secreting cells. After vaginal SIV inoculation, all TLR agonist-treated animals became infected and had plasma vRNA levels that were higher than those of control monkeys. We conclude that induction of mucosal innate immunity including an IFN-alpha response is not sufficient to prevent sexual transmission of human immunodeficiency virus.

Perils at mucosal front lines for HIV and SIV and their hosts

HIV-1 and simian immunodeficiency virus (SIV), as well as their hosts, face perils at mucosal front lines in early infection. At these sites, 'resting' CD4+ memory T cells fuel infection (because they are hosts for virus), depleting CD4+ memory T cells throughout the lymphoid tissues, particularly in the gut, and eliciting an immunosuppressive regulatory T-cell response that impairs host defence. But HIV-1 and SIV also risk elimination at the earliest stage of infection, at the mucosal point of entry, if founder populations of infected cells do not expand sufficiently to establish a self-propagating infection. Microbicides and vaccines could increase these viral vulnerabilities at mucosal front lines.

Safety and distribution of cellulose acetate 1,2-benzenedicarboxylate (CAP), a candidate anti-HIV microbicide in rhesus macaques

OBJECTIVES

To assess the safety and distribution of a cellulose acetate 1,2-benzenedicarboxylate (CAP) gel formulation in rhesus macaques as part of the development process for its use as a vaginally administered product in humans.

DESIGN

The similarities between the reproductive physiology, anatomy and vaginal microflora of human and non-human primates makes non-human primates a relevant animal model to assess the safety and distribution of candidate anti-HIV microbicides.

METHODS

CAP gel was instilled once or once daily for 4 days into the vaginal vault of rhesus macaques. Colposcopy and magnetic resonance imaging were performed to detect adverse effects and spread of CAP, respectively. Additionally, vaginal pH and composition of the vaginal micorflora in macaques before, during and after CAP instillations were determined, and vaginal biopsies obtained following repeated CAP exposures were examined to further document its safety.

RESULTS

CAP is safe for repeated use and exhibits a favorable distribution profile, showing no evidence of penetration into cells that line the vaginal epithelium. Further, the presence of CAP has no adverse effect on vaginal pH or the composition of the vaginal microflora, and does not induce vaginal epithelial thinning or inflammation.

CONCLUSIONS

CAP gel shows minimal toxicity in vivo, supporting its use as a candidate vaginal microbicide in humans.

HIV coreceptor and chemokine ligand gene expression in the male urethra and female cervix

OBJECTIVE

Isolates with a tropism for the coreceptor CCR5 are the predominant viral strain transmitted following heterosexual transmission. We have investigated coreceptor expression levels within male and female genital epithelia to assess whether selective transmission can be explained by elevated CCR5 expression within the genital epithelia per se.

DESIGN

Individuals attending a local genitourinary medicine unit were recruited, and samples of genital epithelia obtained using either a cytobrush (females) or urethral swab (males). Expression of coreceptor and cell marker mRNAs was then determined by reverse transcription (RT)-PCR.

METHODS

RNA was recovered from the epithelial cell samples then used as templates in competitive quantitative RT-PCR to measure mRNA expression of key chemokines, coreceptors and cell-type markers in the epithelial cell samples. Cell-surface coreceptor expression was also assessed in a sample of patients using fluorescent cell staining.

RESULTS

CXCR4 and CCR3 coreceptors were expressed at significantly higher levels than CCR5 within the female endo- and ectocervix and distal end of the male urethra. Increased levels of cell surface expressed CXCR4 compared to CCR5 was confirmed in samples obtained from the female genital tract by FACS analysis.

CONCLUSIONS

The selective transmission of CCR5-tropic viral variants is unlikely to result simply from differential coreceptor abundance at the genital epithelia.

Propagation and dissemination of infection after vaginal transmission of simian immunodeficiency virus

In the current global AIDS pandemic, more than half of new human immunodeficiency virus type 1 (HIV-1) infections are acquired by women through intravaginal HIV exposure. For this study, we explored pathogenesis issues relevant to the development of effective vaccines to prevent infection by this route, using an animal model in which female rhesus macaques were exposed intravaginally to a high dose of simian immunodeficiency virus (SIV). We examined in detail the events that transpire from hours to a few days after intravaginal SIV exposure through week 4 to provide a framework for understanding the propagation, dissemination, and establishment of infection in lymphatic tissues (LTs) during the acute stage of infection. We show that the mucosal barrier greatly limits the infection of cervicovaginal tissues, and thus the initial founder populations of infected cells are small. While there was evidence of rapid dissemination to distal sites, we also show that continuous seeding from an expanding source of production at the portal of entry is likely critical for the later establishment of a productive infection throughout the systemic LTs. The initially small founder populations and dependence on continuous seeding to establish a productive infection in systemic LTs define a small window of maximum vulnerability for the virus in which there is an opportunity for the host, vaccines, or other interventions to prevent or control infection.

HIV-1 clade promoters strongly influence spatial and temporal dynamics of viral replication in vivo

Although the primary determinant of cell tropism is the interaction of viral envelope or capsid proteins with cellular receptors, other viral elements can strongly modulate viral replication. While the HIV-1 promoter is polymorphic for a variety of transcription factor binding sites, the impact of these polymorphisms on viral replication in vivo is not known. To address this issue, we engineered isogenic SIVmac239 chimeras harboring the core promoter/enhancer from HIV-1 clades B, C, and E. Here it is shown that the clade C and E core promoters/enhancers bear a noncanonical activator protein-1 (AP-1) binding site, absent from the corresponding clade B region. Relative ex vivo replication of chimeras was strongly dependent on the tissue culture system used. Notably, in thymic histocultures, replication of the clade C chimera was favored by IL-7 enrichment, which suggests that the clade C polymorphism in the AP-1 and NF-kappaB binding sites is involved. Simultaneous infection of rhesus macaques with the 3 chimeras revealed a strong predominance of the clade C chimera during primary infection. Thereafter, the B chimera dominated in all tissues. These data show that the clade C promoter is particularly adapted to sustain viral replication in primary viremia and that clade-specific promoter polymorphisms constitute a major determinant for viral replication.

IL-8 increases transmission of HIV type 1 in cervical explant tissue

Interleukin-8 (IL-8) is the predominant cytokine expressed in the female genital tract of women with certain infectious/inflammatory conditions. IL-8 increased HIV-1 replication in T cells and to a greater extent in monocytes/macrophages in vitro. Physiological levels of IL-8 increased susceptibility to HIV-1 infection 5- to 8-fold in cervical explant tissues. Competitive inhibition of the IL-8 receptor CXCR2 with the small molecule inhibitor SB225002 resulted in a 45-70% decrease in cervical explant susceptibility to HIV-1 infection.

Abrogation of attenuated lentivirus-induced protection in rhesus macaques by administration of depo-provera before intravaginal challenge with simian immunodeficiency virus mac239

In nonhuman primate models of acquired immunodeficiency syndrome, live attenuated lentiviruses provide the most reliable protection from systemic and mucosal challenge with pathogenic simian immunodeficiency virus (SIV). Although live attenuated lentiviruses may never be used in humans because of safety concerns, understanding the nature of the protective immune mechanisms induced by live attenuated vaccines in primate models will be useful for developing other vaccine approaches. Approximately 60% of rhesus macaques immunized with nonpathogenic simian-human immunodeficiency virus (SHIV) strain 89.6 are protected from infection or clinical disease after intravaginal (IVAG) challenge with pathogenic SIVmac239. The goal of the present study was to determine whether administration of Depo-Provera before IVAG challenge with SIV decreases the protective efficacy of infection with SHIV89.6. The rate of protection after IVAG challenge with SIVmac239 was significantly lower (P<.05), and the acute postchallenge plasma viral RNA levels were significantly higher (P<.006), in Depo-Provera-treated, SHIV89.6-immunized macaques than in Depo-Provera-naive, SHIV89.6-immunized macaques. In the primate model of sexual transmission of human immunodeficiency virus, treatment with progesterone before IVAG challenge with a pathogenic virus can decrease the efficacy of a model "vaccine."

Roles of substrate availability and infection of resting and activated CD4+ T cells in transmission and acute simian immunodeficiency virus infection

In studies of sexual mucosal transmission and early stages of simian immunodeficiency virus (SIV) and HIV infections, productive infection predominates in CD4(+) T cell populations, in both ostensibly resting and activated cells. The surprising ability of SIV and HIV to replicate in resting cells in vivo, in contrast to propagation of infection in vitro, suggested a model in which during the early stages of infection these viruses exploit the greater availability of resting cells to maintain unbroken chains of transmission from an infected resting cell to another resting cell nearby. Because immune activation in response to infection provides more activated CD4(+) T cells, these viruses take advantage of the greater efficiency of virus production and spread in activated cells for propagation and dissemination of infection. In this article, we report the results of experimental tests of this model, including visualization at the light microscopic level and direct analysis of virus production by cells in tissues. Analysis of tissues of rhesus macaques inoculated intravaginally or i.v. with SIV supports the proposed roles of target cell availability, susceptibility, and virus production by infected resting and activated CD4(+) T cells in mucosal transmission and early infection, and points to a potential role for topical anti-inflammatory agents in moderating the initial propagation of infection.

A three-dimensional organotypic culture of the human uterine exocervix for studying mucosal epithelial differentiation and migrating leukocytes

We report on a three-dimensional organotypic culture in vitro of explants from the human uterine exocervix. Exocervical fragments (2-3 mm3) from pre-menopausal women were cultured on sponges submerged in Dulbecco's Modified Eagle's Medium containing p-nonylphenol and 10% fetal bovine serum for up to 3 weeks and the viability and cellular responses were assayed. The fragments were analyzed by immunohistochemistry for the expression and distribution of a broad spectrum of cellular markers: p63, Ki-67, involucrin, high molecular weight cytokeratins, estrogen receptor-alpha, vimentin, CD45, and CD31. The fragments preserved their tissue architecture and cellular heterogeneity comparable to that observed in exocervical tissue in vivo. Prior to culture, the original epithelium was composed of stratified multilayered keratinocytes with integrated monocyte/dendritic-like cells in the basal and suprabasal layers. The epithelium began to exfoliate in culture and within 4 days appeared to have lost its differentiated high-zone layers of keratinocytes. After 10 days a new epithelium, slightly different from the original one, was formed; it displayed an increasing prominence of basal and suprabasal keratinocyte layers, containing infiltrating leukocytes that had probably migrated from the submucosa. The epithelium subsequently lost its organization, concomitant with a progressive involution of the stroma. Subepithelial capillaries appeared to be well maintained throughout the culture period. Aside from the maintenance of cellular heterogeneity within the fragments of exocervix, these culture systems are a valuable tool for studying the mechanisms of epithelial regeneration, and may prove to be a useful model for studying mucosal immunity.

Gamma interferon-mediated inflammation is associated with lack of protection from intravaginal simian immunodeficiency virus SIVmac239 challenge in simian-human immunodeficiency virus 89.6-immunized rhesus macaques

Although gamma interferon (IFN-gamma) is a key mediator of antiviral defenses, it is also a mediator of inflammation. As inflammation can drive lentiviral replication, we sought to determine the relationship between IFN-gamma-related host immune responses and challenge virus replication in lymphoid tissues of simian-human immunodeficiency virus 89.6 (SHIV89.6)-vaccinated and unvaccinated rhesus macaques 6 months after challenge with simian immunodeficiency virus SIVmac239. Vaccinated-protected monkeys had low tissue viral RNA (vRNA) levels, vaccinated-unprotected animals had moderate tissue vRNA levels, and unvaccinated animals had high tissue vRNA levels. The long-term challenge outcome in vaccinated monkeys was correlated with the relative balance between SIV-specific IFN-gamma T-cell responses and nonspecific IFN-gamma-driven inflammation. Vaccinated-protected monkeys had slightly increased tissue IFN-gamma mRNA levels and a high frequency of IFN-gamma-secreting T cells responding to in vitro SIVgag peptide stimulation; thus, it is likely that they could develop effective anti-SIV cytotoxic T lymphocytes in vivo. In contrast, both high tissue IFN-gamma mRNA levels and strong in vitro SIV-specific IFN-gamma T-cell responses were detected in lymphoid tissues of vaccinated-unprotected monkeys. Unvaccinated monkeys had increased tissue IFN-gamma mRNA levels but weak in vitro anti-SIV IFN-gamma T-cell responses. In addition, in lymphoid tissues of vaccinated-unprotected and unvaccinated monkeys, the increased IFN-gamma mRNA levels were associated with increased Mig/CXCL9, IP-10/CXCL10, and CXCR3 mRNA levels, suggesting that increased Mig/CXCL9 and IP-10/CXCL10 expression resulted in recruitment of CXCR3(+) activated T cells. Thus, IFN-gamma-driven inflammation promotes SIV replication in vaccinated-unprotected and unvaccinated monkeys. Unlike all unvaccinated monkeys, most monkeys vaccinated with SHIV89.6 did not develop IFN-gamma-driven inflammation, but they did develop effective antiviral CD8(+)-T-cell responses.

Flow cytometry analysis of immune cell populations isolated from cervicovaginal secretions of cynomolgus monkeys

Flow cytometric analysis was used in this study to characterize the lymphocyte population present in the vaginal mucosa of the cynomolgus monkey. Vaginal immune cells were obtained, using absorbent wicks, from 11 normal cycling female monkeys at different stages of the menstrual cycle and from three nursing monkeys (not cycling). Leucocytes, including lymphocytes and monocyte-macrophage cells, were present in the cervicovaginal secretions of healthy cynomolgous primates throughout the three phases of the menstrual cycle. We also found that even if immune cells were constant throughout the menstrual cycle, among the T cell subsets there were differences. CD8+ cells [14.5+/-9% (mean+/-S.D.); range 3-30%] were more numerous compared to the mean number of CD4+ cells [7.3+/-5% (mean+/-S.D.); range 2-15%]. Characterization of the vaginal cells during the nursing period showed that the monocyte-macrophage (CD14+, CD11c+) cells were abundant compared with the low number of both B (CD20+) and T cells (CD2+). Our results show that cytometric analysis by FACS can be used to identify the immune cell populations present at the local level. This technique may provide a useful tool by which the vaginal environment can be studied in order to correlate cell phenotype with immune function.

Effects of ovarian steroids on immunoglobulin-secreting cell function in healthy women

To determine the effect of the ovarian hormone cycle on immunity, immunoglobulin-secreting cell (ISC) frequency and lymphocyte subsets were examined in the blood of healthy women. We found that immunoglobulin A (IgA)-secreting cells (IgA-ISC) were fourfold more frequent than IgG-ISC in peripheral blood mononuclear cells (PBMC). Further, the ISC frequency in PBMC was highest (P < 0.05) during the periovulatory stage of the menstrual cycle. Thus, endogenous ovarian steroids regulate the ISC frequency and this may explain why women are more resistant to viral infections and tend to have more immune-mediated diseases than men do.

Target cells in vaginal HIV transmission

Understanding the mechanisms of HIV transmission to women will be crucial to the development of effective strategies to curb this epidemic. Current data suggest that HIV has at least two routes to penetrate the vaginal epithelium and reach lymphoid tissues, trans-epithelial migration of infected Langerhans cells or virus penetration into the lamina propria through loss of epithelial integrity resulting in direct infection of lymphocytes, dendritic cells and macrophages.

How oestrogen or progesterone might change a woman's susceptibility to HIV-1 infection

Worldwide, 18.5 million women are infected with the human immunodeficiency virus (HIV-1). At least 80% of these HIV infections have occurred as a result of sexual intercourse with an infected male partner. This review focuses on how HIV-1 enters the human female reproductive tract, and how oestrogen or progesterone, by altering the cervicovaginal epithelium, might change a woman's susceptibility to HIV infection. Experiments on hysterectomised Rhesus monkeys suggest that the vagina, rather than the cervix or uterus, is the main site of viral entry. If ovariectomised monkeys are given systemic oestrogen treatment, this makes them completely resistant to infection by intravaginally administered simian immunodeficiency virus (SIV), whereas progesterone-treated animals, like the untreated controls, are extremely susceptible. Some studies have also shown that women on systemic long-acting gestagen-only contraceptives have a thinner vaginal epithelium and hence might be more susceptible to HIV infection; this is certainly true of post-menopausal women. The beneficial effects of oestrogen are thought to be due to increased thickness and cornification of the cervicovaginal epithelium, which prevents the virus from coming into contact with the target Langerhans cells (LCs). Topical vaginal oestrogen treatment is widely used as a safe and effective way of thickening and keratinising the vaginal epithelium in post-menopausal women. Perhaps this could be an exciting new way of protecting women from HIV infection.