Target cells in vaginal HIV transmission

Extracellular vesicles from seminal plasma interact with T cells in vitro and drive their differentiation into regulatory T-cells

Seminal plasma induces immune tolerance towards paternal allogenic antigens within the female reproductive tract and during foetal development. Recent evidence suggests a role for extracellular vesicles in seminal plasma (spEVs). We isolated spEVs from seminal plasma that was donated by vasectomized men, thereby excluding any contributions from the testis or epididymis. Previous analysis demonstrated that such isolated spEVs originate mainly from the prostate. Here we observed that when isolated fluorescently labelled spEVs were mixed with peripheral blood mononuclear cells, they were endocytosed predominantly by monocytes, and to a lesser extent also by T-cells. In a mixed lymphocyte reaction, T-cell proliferation was inhibited by spEVs. A direct effect of spEVs on T-cells was demonstrated when isolated T cells were activated by anti-CD3/CD28 coated beads. Again, spEVs interfered with T cell proliferation, as well as with the expression of CD25 and the release of IFN-γ, TNF, and IL-2. Moreover, spEVs stimulated the expression of Foxp3 and IL-10 by CD4+CD25+CD127- T cells, indicating differentiation into regulatory T-cells (Tregs). Prior treatment of spEVs with proteinase K revoked their effects on T-cells, indicating a requirement for surface-exposed spEV proteins. The adenosine A2A receptor-specific antagonist CPI-444 also reduced effects of spEVs on T-cells, consistent with the notion that the development of Tregs and their immune suppressive functions are under the influence of adenosine-A2A receptor signalling. We found that adenosine is highly enriched in spEVs and propose that spEVs are targeted to and endocytosed by T-cells, after which they may release their adenosine content into the lumen of endosomes, thus allowing endosome-localized A2A receptor signalling in spEVs targeted T-cells. Collectively, these data support the idea that spEVs can prime T cells directly for differentiation into Tregs.

HIV-1 and HTLV-1 Transmission Modes: Mechanisms and Importance for Virus Spread

So far, only two retroviruses, human immunodeficiency virus (HIV) (type 1 and 2) and human T-cell lymphotropic virus type 1 (HTLV-1), have been recognized as pathogenic for humans. Both viruses mainly infect CD4+ T lymphocytes. HIV replication induces the apoptosis of CD4 lymphocytes, leading to the development of acquired immunodeficiency syndrome (AIDS). After a long clinical latency period, HTLV-1 can transform lymphocytes, with subsequent uncontrolled proliferation and the manifestation of a disease called adult T-cell leukemia (ATLL). Certain infected patients develop neurological autoimmune disorder called HTLV-1-associated myelopathy, also known as tropical spastic paraparesis (HAM/TSP). Both viruses are transmitted between individuals via blood transfusion, tissue/organ transplantation, breastfeeding, and sexual intercourse. Within the host, these viruses can spread utilizing either cell-free or cell-to-cell modes of transmission. In this review, we discuss the mechanisms and importance of each mode of transmission for the biology of HIV-1 and HTLV-1.

Beyond bacterial vaginosis: vaginal lactobacilli and HIV risk

HIV incidence continues to be unacceptably high in Eastern and Southern Africa, with women disproportionately affected. An increased per-contact risk of HIV acquisition among African, Caribbean, and other Black (ACB) women has been associated with the higher prevalence of bacterial vaginosis (BV) in these communities, wherein the vaginal microbiota is predominated by diverse pro-inflammatory anaerobic bacteria. However, while the vaginal microbiota in BV-free women is typically predominated by one of several different Lactobacillus spp., the degree of HIV protection afforded by a Lactobacillus-predominant vaginal microbiota also varies considerably. Specifically, L. crispatus is associated with an immunoregulatory genital immune environment, exclusion of BV-associated bacteria, and reduced HIV risk. In contrast, less HIV protection or exclusion of BV-associated bacteria and fewer immune benefits have been associated with L. iners-which is unfortunately the most common Lactobacillus species among ACB women. These species-specific clinical differences are underpinned by substantial genomic differences between Lactobacillus species: for instance, the much smaller genome of L. iners lacks the coding sequence for D-lactic acid dehydrogenase and cannot produce the D-lactate isomer that enhances HIV trapping in mucus but encodes for epithelial cell toxins and stress resistance proteins that may enhance bacterial survival in the context of microbiota and environmental fluctuations. While more studies are needed to elucidate whether differences in HIV protection between Lactobacillus species are due to direct genital immune effects or the exclusion of proinflammatory BV-associated bacteria, the current body of work suggests that for BV treatment to succeed as an HIV prevention strategy, it may be necessary to induce a vaginal microbiota that is predominated by specific (non-iners) Lactobacillus species. Video abstract.

Inhibition of miR-155 Promotes TGF-β Mediated Suppression of HIV Release in the Cervical Epithelial Cells

TGF-β has been shown to play a differential role in either restricting or aiding HIV infection in different cell types, however its role in the cervical cells is hitherto undefined. Among females, more than 80% of infections occur through heterosexual contact where cervicovaginal mucosa plays a critical role, however the early events during the establishment of infection at female genital mucosa are poorly understood. We earlier showed that increased TGF-β level has been associated with cervical viral shedding in the HIV infected women, however a causal relationship could not be examined. Therefore, here we first established an in vitro cell-associated model of HIV infection in the cervical epithelial cells (ME-180) and demonstrated that TGF-β plays an important role as a negative regulator of HIV release in the infected cervical epithelial cells. Inhibition of miR-155 upregulated TGF-β signaling and mRNA expression of host restriction factors such as APOBEC-3G, IFI-16 and IFITM-3, while decreased the HIV release in ME-180 cells. To conclude, this is the first study to decipher the complex interplay between TGF-β, miR-155 and HIV release in the cervical epithelial cells. Collectively, our data suggest the plausible role of TGF-β in promoting HIV latency in cervical epithelial cells which needs further investigations.

Rectal tissue and vaginal tissue from intravenous VRC01 recipients show protection against ex vivo HIV-1 challenge

BackgroundVRC01, a potent, broadly neutralizing monoclonal antibody, inhibits simian-HIV infection in animal models. The HVTN 104 study assessed the safety and pharmacokinetics of VRC01 in humans. We extend the clinical evaluation to determine intravenously infused VRC01 distribution and protective function at mucosal sites of HIV-1 entry.MethodsHealthy, HIV-1-uninfected men (n = 7) and women (n = 5) receiving VRC01 every 2 months provided mucosal and serum samples once, 4-13 days after infusion. Eleven male and 8 female HIV-seronegative volunteers provided untreated control samples. VRC01 levels were measured in serum, secretions, and tissue, and HIV-1 inhibition was determined in tissue explants.ResultsMedian VRC01 levels were quantifiable in serum (96.2 μg/mL or 1.3 pg/ng protein), rectal tissue (0.11 pg/ng protein), rectal secretions (0.13 pg/ng protein), vaginal tissue (0.1 pg/ng protein), and cervical secretions (0.44 pg/ng protein) from all recipients. VRC01/IgG ratios in male serum correlated with those in paired rectal tissue (r = 0.893, P = 0.012) and rectal secretions (r = 0.9643, P = 0.003). Ex vivo HIV-1Bal26 challenge infected 4 of 21 rectal explants from VRC01 recipients versus 20 of 22 from controls (P = 0.005); HIV-1Du422.1 infected 20 of 21 rectal explants from VRC01 recipients and 12 of 12 from controls (P = 0.639). HIV-1Bal26 infected 0 of 14 vaginal explants of VRC01 recipients compared with 23 of 28 control explants (P = 0.003).ConclusionIntravenous VRC01 distributes into the female genital and male rectal mucosa and retains anti-HIV-1 functionality, inhibiting a highly neutralization-sensitive but not a highly resistant HIV-1 strain in mucosal tissue. These findings lend insight into VRC01 mucosal infiltration and provide perspective on in vivo protective efficacy.FundingNational Institute of Allergy and Infectious Diseases and Bill & Melinda Gates Foundation.

Prevalence and Factors Associated With HIV and Sexually Transmitted Infections Among Female Sex Workers in Bamako, Mali

BACKGROUND

We aimed to (1) estimate the prevalence of HIV and other sexually transmitted infections (STIs) among female sex workers (FSWs) in Bamako, Mali, and (2) identify factors associated with STIs including HIV infection in this population.

METHODS

We analyzed baseline data from a prospective observational cohort study on cervical cancer screening, human papillomavirus, and HIV infections among FSWs 18 years or older recruited in Bamako. Multivariable log-binomial regression was used to estimate the adjusted prevalence ratios (APRs) with 95% confidence interval (95% CI) for HIV infection and STIs versus associated factors.

RESULTS

Among 353 women participating in the study, mean age was 26.8 (±7.6) years. HIV prevalence was 20.4%, whereas 35.1% of the FSWs had at least one STI. Factors significantly associated with HIV were older age (P < 0.0001, test for trend), duration of sex work ≥6 years (APR, 1.92; 95% CI, 1.22-3.02), uneducated status (APR, 2.24; 95% CI, 1.16-4.34), less than 10 clients in the last 7 days (APR, 1.55; 95% CI, 1.02-2.34), and gonococcal (APR, 1.85; 95% CI, 1.21-2.82) and chlamydial (APR, 2.58; 95% CI, 1.44-4.62) infections. Younger age (P = 0.018, test for trend), having ≥10 clients in the last week (APR, 1.47; 95% CI, 1.11-1.94), and HIV infection (APR, 2.00; 95% CI, 1.49-2.69) were significantly associated with STIs.

CONCLUSIONS

HIV and curable STI prevalence are high among FSWs in Bamako. There is thus a need to enhance the efficiency of interventions toward FSWs in Mali to reduce the burden of HIV and STIs among them and prevent HIV spread to the general population.

Interactions with Commensal and Pathogenic Bacteria Induce HIV-1 Latency in Macrophages through Altered Transcription Factor Recruitment to the LTR

Macrophages are infected by HIV-1 in vivo and contribute to both viral spread and pathogenesis. Recent human and animal studies suggest that HIV-1-infected macrophages serve as a reservoir that contributes to HIV-1 persistence during anti-retroviral therapy. The ability of macrophages to serve as persistent viral reservoirs is likely influenced by the local tissue microenvironment, including interactions with pathogenic and commensal microbes. Here we show that the sexually transmitted pathogen Neisseria gonorrhoeae (GC) and the gut-associated microbe Escherichia coli (E. coli), which encode ligands for both Toll-like receptor 2 (TLR2) and TLR4, repressed HIV-1 replication in macrophages and thereby induced a state reminiscent of viral latency. This repression was mediated by signaling through TLR4 and the adaptor protein TRIF and was associated with increased production of type I interferons. Inhibiting TLR4 signaling, blocking type 1 interferon, or knocking-down TRIF reversed LPS- and GC-mediated repression of HIV-1. Finally, the repression of HIV-1 in macrophages was associated with the recruitment of interferon regulatory factor 8 (IRF8) to the interferon stimulated response element (ISRE) downstream of the 5' HIV-1 long terminal repeat (LTR). Our data indicate that IRF8 is responsible for repression of HIV-1 replication in macrophages in response to TRIF-dependent signaling during GC and E. coli co-infection. These findings highlight the potential role of macrophages as HIV-1 reservoirs as well as the role of the tissue microenvironment and co-infections as modulators of HIV-1 persistence.IMPORTANCE The major barrier toward the eradication of HIV-1 infection is the presence of a small reservoir of latently infected cells, which include CD4+ T cells and macrophages that escape immune-mediated clearance and the effects of anti-retroviral therapy. There remain crucial gaps in our understanding of the molecular mechanisms that lead to transcriptionally silent or latent HIV-1 infection of macrophages. The significance of our research is in identifying microenvironmental factors, such as commensal and pathogenic microbes, that can contribute to the establishment and maintenance of latent HIV-1 infection in macrophages. It is hoped that identifying key processes contributing to HIV-1 persistence in macrophages may ultimately lead to novel therapeutics to eliminate latent HIV-1 reservoirs in vivo.

Immunocompetent Human 3D Organ-Specific Hormone-Responding Vaginal Mucosa Model of HIV-1 Infection

The lack of appropriate experimental models often limits our ability to investigate the establishment of infections in specific tissues. To reproduce the structural and spatial organization of vaginal mucosae to study human immunodeficiency virus type-1 (HIV-1) infection, we used the self-assembly technique to bioengineer tridimensional vaginal mucosae using human cells extracted from HIV-1-negative healthy pre- and postmenopausal donors. We produced a stroma, free of exogenous material, that can be adapted to generate near-to-native vaginal tissue with the best complexity obtained with seeded epithelial cells on the organ-specific stroma. The autologous engineered tissues had mechanical properties close to native mucosa and shared similar glycogen production, which declined in reconstructed tissues of the postmenopausal donor. The in vitro-engineered tissues were also rendered immune competent by adding human monocyte-derived macrophages (MDMs) on the epithelium or in the stroma layers. The model was infected with HIV-1, and viral replication and transcytosis were observed when immunocompetent reconstructed vaginal mucosa tissue has incorporated MDMs into the stroma and infected with free HIV-1 green fluorescent protein (GFP) viral particles. These data illustrate a natural permissiveness of immunocompetent untransformed human vaginal mucosae to HIV-1 infection. This model offers a physiological tool to explore viral load, HIV-1 transmission in an environment that may contribute to the virus propagation, and new antiviral treatments in vitro. Impact statement This study introduces an innovative immunocompetent three-dimensional human organ-specific vaginal mucosa free of exogenous material for in vitro modeling of human immunodeficiency virus type-1 (HIV-1) infection. The proposed model is histologically close to native tissue, especially by presenting glycogen accumulation in the epithelium's superficial cells, responsive to estrogen, and able to sustain a monocyte-derived macrophage population infected or not by HIV-1 during ∼2 months.

miRNA profiling of primate cervicovaginal lavage and extracellular vesicles reveals miR-186-5p as a potential antiretroviral factor in macrophages

Cervicovaginal secretions, or their components collected, are referred to as cervicovaginal lavage (CVL). CVL constituents have utility as biomarkers and play protective roles in wound healing and against HIV-1 infection. However, several components of cervicovaginal fluids are less well understood, such as extracellular RNAs and their carriers, for example, extracellular vesicles (EVs). EVs comprise a wide array of double-leaflet membrane extracellular particles and range in diameter from 30 nm to over one micron. The aim of this study was to determine whether differentially regulated CVL microRNAs (miRNAs) might influence retrovirus replication. To this end, we characterized EVs and miRNAs of primate CVL during the menstrual cycle and simian immunodeficiency virus (SIV) infection of macaques. EVs were enriched by stepped ultracentrifugation, and miRNA profiles were assessed with a medium-throughput stem-loop/hydrolysis probe qPCR platform. Whereas hormone cycling was abnormal in infected subjects, EV concentration correlated with progesterone concentration in uninfected subjects. miRNAs were present predominantly in the EV-depleted CVL supernatant. Only a small number of CVL miRNAs changed during the menstrual cycle or SIV infection, for example, miR-186-5p, which was depleted in retroviral infection. This miRNA inhibited HIV replication in infected macrophages in vitro. In silico target prediction and pathway enrichment analyses shed light on the probable functions of miR-186-5p in hindering HIV infections via immunoregulation, T-cell regulation, disruption of viral pathways, etc. These results provide further evidence for the potential of EVs and small RNAs as biomarkers or effectors of disease processes in the reproductive tract.

The Innate Immune Cell Profile of the Cornea Predicts the Onset of Ocular Surface Inflammatory Disorders

Ocular surface inflammatory disorder (OSID) is a spectrum of disorders that have features of several etiologies whilst displaying similar phenotypic signs of ocular inflammation. They are complicated disorders with underlying mechanisms related to several autoimmune disorders, such as rheumatoid arthritis (RA), Sjögren’s syndrome, and systemic lupus erythematosus (SLE). Current literature shows the involvement of both innate and adaptive arms of the immune system in ocular surface inflammation. The ocular surface contains distinct components of the immune system in the conjunctiva and the cornea. The normal conjunctiva epithelium and sub-epithelial stroma contains resident immune cells, such as T cells, B cells (adaptive), dendritic cells, and macrophages (innate). The relative sterile environment of the cornea is achieved by the tolerogenic properties of dendritic cells in the conjunctiva, the presence of regulatory lymphocytes, and the existence of soluble immunosuppressive factors, such as the transforming growth factor (TGF)-β and macrophage migration inhibitory factors. With the presence of both innate and adaptive immune system components, it is intriguing to investigate the most important leukocyte population in the ocular surface, which is involved in immune surveillance. Our meta-analysis investigates into this with a focus on both infectious (contact lens wear, corneal graft rejection, Cytomegalovirus, keratitis, scleritis, ocular surgery) and non-infectious (dry eye disease, glaucoma, graft-vs-host disease, Sjögren’s syndrome) situations. We have found the predominance of dendritic cells in ocular surface diseases, along with the Th-related cytokines. Our goal is to improve the knowledge of immune cells in OSID and to open new dimensions in the field. The purpose of this study is not to limit ourselves in the ocular system, but to investigate the importance of dendritic cells in the disorders of other mucosal organs (e.g., lungs, gut, uterus). Holistically, we want to investigate if this is a common trend in the initiation of any disease related to the mucosal organs and find a unified therapeutic approach. In addition, we want to show the power of computational approaches to foster a collaboration between computational and biological science.

The Influence of Cervicovaginal Microbiota on Mucosal Immunity and Prophylaxis in the Battle against HIV

PURPOSE OF REVIEW

Young women in sub-Saharan Africa bear a disproportionate burden of the global HIV epidemic. In this review, we examine how cervicovaginal microbiota modulate structural and immune defenses in the female genital tract and influence HIV susceptibility.

RECENT FINDINGS

Highly diverse, anaerobic cervicovaginal microbiota prevalent in sub-Saharan African women increase HIV acquisition risk by over fourfold. These bacteria weaken the barrier properties of the vaginal mucosa and increase local inflammation and HIV target cell recruitment, creating an environment permissive to HIV. These communities also diminish the prophylactic efficacy of topical tenofovir and therefore may modulate both biological susceptibility to HIV and the effectiveness of pre-exposure prophylaxis (PrEP). Cervicovaginal bacteria influence multiple reproductive health outcomes, including HIV acquisition. High-diversity, low Lactobacillus abundance cervicovaginal communities prevalent in many regions with high HIV incidence are associated with increased HIV susceptibility. A better understanding of the host-microbial interactions mediating this risk is important to reduce HIV infections, particularly among women living in sub-Saharan Africa.

Defining early SIV replication and dissemination dynamics following vaginal transmission

Understanding HIV transmission is critical to guide the development of prophylactic interventions to prevent infection. We used a nonhuman primate (NHP) model with a synthetic swarm of sequence-tagged variants of SIVmac239 ("SIVmac239X") and scheduled necropsy during primary infection (days 3 to 14 after challenge) to study viral dynamics and host responses to the establishment and dissemination of infection following vaginal challenge. We demonstrate that local replication was initiated at multiple sites within the female genital tract (FGT), with each site having multiple viral variants. Local replication and spread in the FGT preceded lymphatic dissemination. Innate viral restriction factors were observed but appeared to follow viral replication and were ineffective at blocking initial viral establishment and dissemination. However, major delays were observed in time to dissemination in animals and among different viral variants within the same animal. It will be important to assess how phenotypic differences affect early viral dynamics.

Barriers of Mucosal Entry of HIV/SIV

Most new HIV infections, over 80%, occur through sexual transmission. During sexual transmission, the virus must bypass specific female and male reproductive tract anatomical barriers to encounter viable target cells. Understanding the generally efficient ability of these barrier to exclude HIV and the precise mechanisms of HIV translocation beyond these genital barriers is essential for vaccine and novel therapeutic development. In this review, we explore the mucosal, barriers of cervico-vaginal and penile tissues that comprise the female and male reproductive tracts. The unique cellular assemblies f the squamous and columnar epithelium are illustrate highlighting their structure and function. Each anatomical tissue offers a unique barrier to virus entry in healthy individuals. Unfortunately barrier dysfunction can lead to HIV transmission. How these diverse mucosal barriers have the potential to fail is considered, highlighting those anatomical areas that are postulated to offer a weaker barrier and are; therefore, more susceptible to viral ingress. Risk factors, such as sexually transmitted infections, microbiome dysbiosis, and high progestin environments are also associated with increased acquisition of HIV. How these states may affect the integrity of mucosal barriers leading to HIV acquisition are discussed suggesting mechanisms of transmission and revealing potential targets for intervention.

Neisseria gonorrhoeae uses cellular proteins CXCL10 and IL8 to enhance HIV-1 transmission across cervical mucosa

Problem

Neisseria gonorrhoeae (NG) infection has been shown to increase sexual transmission of HIV‐1. However, the mechanism of NG‐induced enhanced HIV‐1 transmission is unknown.

Methods

(a) The cervical tissues were exposed to NG, and cytokine induction was monitored by measuring cytokine proteins in culture supernatants and cytokine mRNAs in tissues. (b) Transcription and replication of HIV‐1 in TZM‐bl, U1, and ACH2 cells were measured by Beta‐Gal activity and p24 proteins in the supernatant, respectively. (c) HIV‐1 transmission was assayed in an organ culture system by measuring transmitted HIV‐1 in supernatant and HIV‐1 gag mRNA in the tissues. (d) Transcriptome analysis was done using second generation sequencing.

Results

(a) NG induced membrane ruffling of epithelial layer, caused migration of CD3+ cells to the intraepithelial region, and induced high levels of inflammatory cytokines IL‐1β and TNF‐α. (b) NG‐induced supernatants (NGIS) increased HIV‐1 transcription, induced HIV‐1 from latently infected cells, and increased transmission of HIV‐1 across cervical mucosa. (c) Transcriptome analysis of the epithelial layer of the tissues exposed to NG, and HIV‐1 showed significant upregulation of CXCL10 and IL8. IL‐1β increased the induction of CXCL10 and IL‐8 expression in cervical mucosa with a concomitant increase in HIV‐1 transmission.

Conclusion

We present a model in which IL‐1β produced from cervical epithelium during NG exposure increases CXCL10 and IL8 in epithelia. This in turn causes upon HIV‐1 infection, the migration of HIV‐1 target cells toward the subepithelium, resulting in increased HIV‐1 transcription in the sub‐mucosa and subsequent enhancement of transmission across cervical mucosa.

Defining characteristics of genital health in South African adolescent girls and young women at high risk for HIV infection

The genital tract of African women has been shown to differ from what is currently accepted as ‘normal’, defined by a pH≤4.5 and lactobacilli-dominated microbiota. Adolescent girls and young women (AGYW) from sub-Saharan Africa are at high risk for HIV, and we hypothesized that specific biological factors are likely to be influential. This study aimed to compare characteristics of vaginal health in HIV-negative AGYW (16-22-years-old), from two South African communities, to international norms. We measured plasma hormones, vaginal pH, presence of BV (Nugent scoring), sexually transmitted infections (multiplex PCR for Chlamydia trachomatis, Neisseria gonorrhoea, Trichomonas vaginalis, Mycoplasma genitalium) and candidiasis (Gram stain) in AGYW (n = 298) from Cape Town and Soweto. Cervicovaginal microbiota was determined by 16S pyrosequencing; 44 genital cytokines were measured by Luminex; and cervical T-cell activation/proliferation (CCR5, HLA-DR, CD38, Ki67) was measured by multiparametric flow cytometry. 90/298 (30.2%) AGYW were negative for BV, candidiasis and bacterial STIs. L. crispatus and L. iners were the dominant bacteria in cervicovaginal swabs, and the median vaginal pH was 4.7. AGYW with L. crispatus-dominant microbiota (42.4%) generally had the lowest cytokine concentrations compared to women with more diverse microbiota (34/44 significantly upregulated cytokines). Frequencies of CCR5+CD4⁺ T-cells co-expressing CD38 and HLA-DR correlated positively with interleukin (IL)-6, TNF-α, GRO-α, macrophage inflammatory protein (MIP)-1α, and IL-9. While endogenous oestrogen had an immune-dampening effect on IL-6, TNF-related apoptosis-inducing ligand (TRAIL) and IL-16, injectable hormone contraceptives (DMPA and Net-EN) were associated with significantly lower endogenous hormone concentrations (p<0.0001 for oestrogen and progesterone) and upregulation of 34/44 cytokines. Since genital inflammation and the presence of activated CD4+ T cells in the genital tract have been implicated in increased HIV risk in South African women, the observed high levels of genital cellular activation and cytokines from AGYW may point towards biological factors increasing HIV risk in this region.

Ecological dynamics of the vaginal microbiome in relation to health and disease

The bacterial composition of the vaginal microbiome is thought to be related to health and disease states of women. This microbiome is particularly dynamic, with compositional changes related to pregnancy, menstruation, and disease states such as bacterial vaginosis. In order to understand these dynamics and their impact on health and disease, ecological theories have been introduced to study the complex interactions between the many taxa in the vaginal bacterial ecosystem. The goal of this review is to introduce the ecological principles that are used in the study of the vaginal microbiome and its dynamics, and to review the application of ecology to vaginal microbial communities with respect to health and disease. Although applications of vaginal microbiome analysis and modulation have not yet been introduced into the routine clinical setting, a deeper understanding of its dynamics has the potential to facilitate development of future practices, for example in the context of postmenopausal vaginal symptoms, stratifying risk for obstetric complications, and controlling sexually transmitted infections.

A high mucosal blocking score is associated with HIV protection

BACKGROUND

Early steps of HIV infection are mediated by the binding of the envelope to mucosal receptors as α4β7 and the C-type lectins DC-SIGN and langerin. Previously Env-specific B-cell responses have been reported in highly exposed seronegative individuals (HESN).

METHOD

Here, we studied gp120-specific antibodies ability to block HIV interaction with α4β7, DC-SIGN and/or langerinin HESN. New cell-based assays were developed to analyze whether antibodies that can alter gp120 binding to α4β7, DC-SIGN and/or langerin are induced in HESN. A mucosal blocking score (MBS) was defined based on the ability of antibodies to interfere with gp120/α4β7, gp120/DC-SIGN, and gp120/langerin binding. A new MBS was evaluated in a cohort of 86 HESN individuals and compared with HIV+ patients or HIV- unexposed healthy individuals.

RESULTS

Antibodies reducing gp120 binding to both α4β7 and DC-SIGN were present in HESN serum but also in mucosal secretions, whereas antibodies from HIV+ patients facilitated gp120 binding to DC-SIGN. Any correlation was observed between MBS and the capacity of antibodies to neutralize infection of α4β7 CD4+ T cells with primary isolates.

CONCLUSIONS

MBS is significantly associated with protection in HESN and might reflect altered HIV spreading to mucosal-associated lymphoid tissues.

The relationship between sex hormones, the vaginal microbiome and immunity in HIV-1 susceptibility in women

The role of sex hormones in regulating immune responses in the female genital tract has been recognized for decades. More recently, it has become increasingly clear that sex hormones regulate susceptibility to sexually transmitted infections through direct and indirect mechanisms involving inflammation and immune responses. The reproductive cycle can influence simian/human immunodeficiency virus (SHIV) infections in primates and HIV-1 infection in ex vivo cervical tissues from women. Exogenous hormones, such as those found in hormonal contraceptives, have come under intense scrutiny because of the increased susceptibility to sexually transmitted infections seen in women using medroxyprogesterone acetate, a synthetic progestin-based contraceptive. Recent meta-analyses concluded that medroxyprogesterone acetate enhanced HIV-1 susceptibility in women by 40%. In contrast, estradiol-containing hormonal contraceptives were not associated with increased susceptibility and some studies reported a protective effect of estrogen on HIV/SIV infection, although the underlying mechanisms remain incompletely understood. Recent studies describe a key role for the vaginal microbiota in determining susceptibility to sexually transmitted infections, including HIV-1. While Lactobacillus spp.-dominated vaginal microbiota is associated with decreased susceptibility, complex microbiota, such as those seen in bacterial vaginosis, correlates with increased susceptibility to HIV-1. Interestingly, sex hormones are inherently linked to microbiota regulation in the vaginal tract. Estrogen has been postulated to play a key role in establishing a Lactobacillus-dominated microenvironment, whereas medroxyprogesterone acetate is linked to hypo-estrogenic effects. The aim of this Review is to contribute to a better understanding of the sex-hormone-microbiome-immunity axis, which can provide key information on the determinants of HIV-1 susceptibility in the female genital tract and, consequently, inform HIV-1 prevention strategies.

Sequential BMP7/TGF-β1 signaling and microbiota instruct mucosal Langerhans cell differentiation

Capucha et al. demonstrate that mucosal Langerhans cell (LC) differentiation from pre–dendritic cells and monocytes involves consecutive BMP7 and TGF-β1 signaling in separate anatomical locations. Moreover, mucosal microbiota regulates the development of LCs that in turn shape microbial and immunological homeostasis.

Mucosal Langerhans cells (LCs) originate from pre–dendritic cells and monocytes. However, the mechanisms involved in their in situ development remain unclear. Here, we demonstrate that the differentiation of murine mucosal LCs is a two-step process. In the lamina propria, signaling via BMP7-ALK3 promotes translocation of LC precursors to the epithelium. Within the epithelium, TGF-β1 finalizes LC differentiation, and ALK5 is crucial to this process. Moreover, the local microbiota has a major impact on the development of mucosal LCs, whereas LCs in turn maintain mucosal homeostasis and prevent tissue destruction. These results reveal the differential and sequential role of TGF-β1 and BMP7 in LC differentiation and highlight the intimate interplay of LCs with the microbiota.

Innate immunity in HIV-1 infection: epithelial and non-specific host factors of mucosal immunity- a workshop report

The interplay between HIV-1 and epithelial cells represents a critical aspect in mucosal HIV-1 transmission. Epithelial cells lining the oral cavity cover subepithelial tissues, which contain virus-susceptible host cells including CD4(+) T lymphocytes, monocytes/macrophages, and dendritic cells. Oral epithelia are among the sites of first exposure to both cell-free and cell-associated virus HIV-1 through breast-feeding and oral-genital contact. However, oral mucosa is considered to be naturally resistant to HIV-1 transmission. Oral epithelial cells have been shown to play a crucial role in innate host defense. Nevertheless, it is not clear to what degree these local innate immune factors contribute to HIV-1 resistance of the oral mucosa. This review paper addressed the following issues that were discussed at the 7th World Workshop on Oral Health and Disease in AIDS held in Hyderabad, India, during November 6-9, 2014: (i) What is the fate of HIV-1 after interactions with oral epithelial cells?; (ii) What are the keratinocyte and other anti-HIV effector oral factors, and how do they contribute to mucosal protection?; (iii) How can HIV-1 interactions with oral epithelium affect activation and populations of local immune cells?; (iv) How can HIV-1 interactions alter functions of oral epithelial cells?

Pharmacokinetics and Preliminary Safety of Pod-Intravaginal Rings Delivering the Monoclonal Antibody VRC01-N for HIV Prophylaxis in a Macaque Model

The broadly neutralizing antibody (bNAb) VRC01, capable of neutralizing 91% of known human immunodeficiency virus type 1 (HIV-1) isolates in vitro, is a promising candidate microbicide for preventing sexual HIV infection when administered topically to the vagina; however, accessibility to antibody-based prophylactic treatment by target populations in sub-Saharan Africa and other underdeveloped regions may be limited by the high cost of conventionally produced antibodies and the limited capacity to manufacture such antibodies. Intravaginal rings of the pod design (pod-IVRs) delivering Nicotiana-manufactured VRC01 (VRC01-N) over a range of release rates have been developed. The pharmacokinetics and preliminary safety of VRC01-N pod-IVRs were evaluated in a rhesus macaque model. The devices sustained VRC01-N release for up to 21 days at controlled rates, with mean steady-state VRC01-N levels in vaginal fluids in the range of 10² to 10³ μg g^-1 being correlated with in vitro release rates. No adverse safety indications were observed. These findings indicate that pod-IVRs are promising devices for the delivery of the candidate topical microbicide VRC01-N against HIV-1 infection and merit further preclinical evaluation.

The HIV-1 transmission bottleneck

It is well established that most new systemic infections of HIV-1 can be traced back to one or a limited number of founder viruses. Usually, these founders are more closely related to minor HIV-1 populations in the blood of the presumed donor than to more abundant lineages. This has led to the widely accepted idea that transmission selects for viral characteristics that facilitate crossing the mucosal barrier of the recipient’s genital tract, although the specific selective forces or advantages are not completely defined. However, there are other steps along the way to becoming a founder virus at which selection may occur. These steps include the transition from the donor’s general circulation to the genital tract compartment, survival within the transmission fluid, and establishment of a nascent stable local infection in the recipient’s genital tract. Finally, there is the possibility that important narrowing events may also occur during establishment of systemic infection. This is suggested by the surprising observation that the number of founder viruses detected after transmission in intravenous drug users is also limited. Although some of these steps may be heavily selective, others may result mostly in a stochastic narrowing of the available founder pool. Collectively, they shape the initial infection in each recipient.

Preformulation and Vaginal Film Formulation Development of Microbicide Drug Candidate CSIC for HIV prevention

PURPOSE

5-chloro-3-[phenylsulfonyl] indole-2-carboxamide (CSIC) is a highly potent non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1 which has been shown to have a more desirable resistance profile than other NNRTIs in development as HIV prevention strategies. This work involves generation of preformulation data for CSIC and systematic development of a cosolvent system to effectively solubilize this hydrophobic drug candidate. This system was then applied to produce a polymeric thin film solid dosage form for vaginal administration of CSIC for use in prevention of sexual acquisition of HIV.

METHODS

Extensive preformulation, formulation development, and film characterization studies were conducted. An HPLC method was developed for CSIC quantification. Preformulation tests included solubility, crystal properties, stability, and drug-excipient compatibility. Cytotoxicity was evaluated using both human epithelial and mouse macrophage cell lines. Ternary phase diagram methodology was used to identify a cosolvent system for CSIC solubility enhancement. Following preformulation evaluation, a CSIC film formulation was developed and manufactured using solvent casting technique. The developed film product was assessed for physicochemical properties, anti-HIV bioactivity, and Lactobacillus biocompatibility during 12-month stability testing period.

RESULTS

Preformulation studies showed CSIC to be very stable. Due to its hydrophobicity, a cosolvent system consisting of polyethylene glycol 400, propylene glycol, and glycerin (5:2:1, w/w/w) was developed, which provided a uniform dispersion of CSIC in the film formulation. The final film product met target specifications established for vaginal microbicide application.

CONCLUSIONS

The hydrophobic drug candidate CSIC was successfully formulated with high loading capacity in a vaginal film by means of a cosolvent system. The developed cosolvent strategy is applicable for incorporation of other hydrophobic drug candidates in the film platform.

Increase in HIV Receptors/Co-receptors/α-defensins in Inflamed Human Gingiva

Transmission of HIV-1 through the oral cavity is considered to be a rare event. To identify factors in resistance/susceptibility to oral HIV-1 infection, we analyzed expression in human gingiva of HIV-1 receptors Langerin, DC-SIGN, MR, and GalCer, HIV-1 co-receptors CCCR5, CXCR4, and anti-microbial protein α-defensin-1. Our results show that healthy gingiva is infiltrated with cells expressing all HIV-1 receptors tested; however, there are very few CCR5+ cells and a complete absence of CXCR4+ cells in the lamina propria. In chronic periodontitis (CP), DC-SIGN, MR, CXCR4, and CCR5 increase, but this was accompanied by a ten-fold increase in α-defensin-1 mRNA. The CCR5+ cells were revealed to be T-cells, macrophages, and dermal dendritic cells. Moreover, epithelial expression of GalCer and CXCR4 together was not apical and showed no trend with underlying inflammation. Thus, low expression of HIV-1 co-receptors in health and high expression of α-defensin during CP may comprise endogenous factors that provide protection from oral HIV-1 infection.

Knowledge and exercise of human rights, and barriers and facilitators to claiming rights: a cross-sectional study of female sex workers and high-risk men who have sex with men in Andhra Pradesh, India

Background

HIV prevention interventions recognize the need to protect the rights of key populations and support them to claim their rights as a vulnerability reduction strategy. This study explores knowledge of human rights, and barriers and facilitators to claiming rights, among female sex workers (FSWs) and high-risk men who have sex with men (HR-MSM) who are beneficiaries of a community mobilization intervention in Andhra Pradesh, India.

Methods

Data are drawn from a cross-sectional survey (2014) among 2400 FSWs and 1200 HR-MSM. Human rights awareness was assessed by asking respondents if they had heard of human rights (yes/no); those reporting awareness of rights were asked to spontaneously name specific rights from the following five pre-defined categories: right to health; dignity/equality; education; property; and freedom from discrimination. Respondents were classified into two groups: more knowledgeable (could identify two or more rights) and less knowledgeable (could identify one or no right). Univariate and bivariate analyses and chi-square tests were used. Data were analyzed using STATA 11.2.

Results

Overall 17% FSWs and 8% HR-MSM were not aware of their rights. Among those aware, 62% and 31% respectively were aware of just one or no right (less knowledgeable); only around half (54% vs 57%) were aware of health rights, and fewer (20% vs 16%) aware of their right to freedom from discrimination. Notably, 27% and 17% respectively had not exercised their rights. Barriers to claiming rights among FSWs and HR-MSM were neighbors (35% vs 37%), lack of knowledge (15% vs 14%), stigma (13% vs 22%) and spouse (19% FSWs). Community organizations (COs) were by far the leading facilitator in claiming rights (57% vs 72%).

Conclusions

The study findings show that awareness of human rights is limited among FSWs and HR-MSM, and a large proportion have not claimed their rights, elevating their HIV vulnerability. For a sustained HIV response, community mobilization efforts must focus on building key populations’ awareness of rights, and addressing the multiple barriers to claiming rights, with a view to creating a safe environment where vulnerable groups can demand and use services without fear of stigma, discrimination and violation of rights.

Recent Insights into the HIV/AIDS Pandemic

Etiology, transmission and protection: Transmission of HIV, the causative agent of AIDS, occurs predominantly through bodily fluids. Factors that significantly alter the risk of HIV transmission include male circumcision, condom use, high viral load, and the presence of other sexually transmitted diseases. Pathology/Symptomatology: HIV infects preferentially CD4+ T lymphocytes, and Monocytes. Because of their central role in regulating the immune response, depletion of CD4+ T cells renders the infected individual incapable of adequately responding to microorganisms otherwise inconsequential. Epidemiology, incidence and prevalence: New HIV infections affect predominantly young heterosexual women and homosexual men. While the mortality rates of AIDS related causes have decreased globally in recent years due to the use of highly active antiretroviral therapy (HAART) treatment, a vaccine remains an elusive goal. Treatment and curability: For those afflicted HIV infection remains a serious illness. Nonetheless, the use of advanced therapeutics have transformed a dire scenario into a chronic condition with near average life spans. When to apply those remedies appears to be as important as the remedies themselves. The high rate of HIV replication and the ability to generate variants are central to the viral survival strategy and major barriers to be overcome. Molecular mechanisms of infection: In this review, we assemble new details on the molecular events from the attachment of the virus, to the assembly and release of the viral progeny. Yet, much remains to be learned as understanding of the molecular mechanisms used in viral replication and the measures engaged in the evasion of immune surveillance will be important to develop effective interventions to address the global HIV pandemic.

Relationship of Estimated SHIV Acquisition Time Points During the Menstrual Cycle and Thinning of Vaginal Epithelial Layers in Pigtail Macaques

BACKGROUND

HIV acquisition in the female genital tract remains incompletely understood. Quantitative data on biological HIV risk factors, the influence of reproductive hormones, and infection risk are lacking. We evaluated vaginal epithelial thickness during the menstrual cycle in pigtail macaques (Macaca nemestrina). This model previously revealed increased susceptibility to vaginal infection during and after progesterone-dominated periods in the menstrual cycle.

METHODS

Nucleated and nonnucleated (superficial) epithelial layers were quantitated throughout the menstrual cycle of 16 macaques. We examined the relationship with previously estimated vaginal SHIVSF162P3 acquisition time points in the cycle of 43 different animals repeatedly exposed to low virus doses.

RESULTS

In the luteal phase (days 17 to cycle end), the mean vaginal epithelium thinned to 66% of mean follicular thickness (days 1-16; P = 0.007, Mann-Whitney test). Analyzing 4-day segments, the epithelium was thickest on days 9 to 12 and thinned to 31% thereof on days 29 to 32, with reductions of nucleated and nonnucleated layers to 36% and 15% of their previous thickness, respectively. The proportion of animals with estimated SHIV acquisition in each cycle segment correlated with nonnucleated layer thinning (Pearson r = 0.7, P < 0.05, linear regression analysis), but not nucleated layer thinning (Pearson r = 0.6, P = 0.15).

CONCLUSIONS

These data provide a detailed picture of dynamic cycle-related changes in the vaginal epithelium of pigtail macaques. Substantial thinning occurred in the superficial, nonnucleated layer, which maintains the vaginal microbiome. The findings support vaginal tissue architecture as susceptibility factor for infection and contribute to our understanding of innate resistance to SHIV infection.

Progress and Perspectives on HIV-1 microbicide development

The majority of HIV-1 infections occur via sexual intercourse. Women are the most affected by the epidemic, particularly in developing countries, due to their socio-economic dependence on men and the fact that they are often victims of gender based sexual violence. Despite significant efforts that resulted in the reduction of infection rates in some countries, there is still need for effective prevention methods against the virus. One of these methods for preventing sexual transmission in women is the use of microbicides. In this review we provide a summary of the progress made toward the discovery of affordable and effective HIV-1 microbicides and suggest future directions. We show that there is a wide range of compounds that have been proposed as potential microbicides. Although most of them have so far failed to show protection in humans, there are many promising ones currently in pre-clinical studies and in clinical trials.

Oral epithelial cells and their interactions with HIV-1

As the AIDS pandemic has continued, our understanding of the events that occur during the entry and infection of conventional, susceptible cells has increased dramatically, leading to the development of control therapies for HIV-infected individuals. However, an ongoing hole in our understanding is how HIV crosses the mucosal barriers to gain access to permissive cells, despite how important this information would be in developing successful vaccines and other preventative measures such as topical anti-HIV microbicides. In particular, our knowledge of the role that epithelial cells of the mucosal surfaces play in infection - both during early phases and throughout the life of an infected individual, is currently hazy at best. However, several studies in recent years suggest that HIV can bind to and traverse these mucosal epithelial cells, providing a reservoir of infection that can subsequently infect underlying permissive cells. Despite this interaction with epithelial cells, evidence suggests HIV-1 does not productively infect these cells, although they are capable of transferring surface-bound and transcytosed virus to other, permissive cells. Further, there appear to be key differences between adult and infant epithelial cells in the degree to which HIV can transcytose and infect the epithelium. Thus, it is clear that, whilst not primary targets for infection and virus replication, epithelial cells play an important role in the infection cycle and improving our understanding of their interactions with HIV could potentially provide key insights necessary to develop effective preventative therapies.

Effect of Physical Violence on Sexually Transmitted Infections and Treatment Seeking Behaviour among Female Sex Workers in Thane District, Maharashtra, India

BACKGROUND

Violence against sex workers can heighten their vulnerability to HIV and other sexually transmitted infections (STIs). Evidence suggests the risk of acquiring STI/HIV infections among female sex workers (FSWs) who have experienced violence to be almost three-times higher than FSWs, who have not experienced violence. Moreover, an experience of physical and sexual violence makes it difficult for them to negotiate safer sex with their partners and often act as a barrier to utilization of prevention services.

METHODS

This study utilizes data from 2785 FSWs aged 18 years and above who participated in a cross-sectional behavioural study conducted during 2013-14 in Thane district, Maharashtra. A probability-based two-stage cluster sampling method was used for data collection. This study assesses the effect of physical violence on self-reported STI symptoms (any STI and multiple STIs) and treatment seeking for the last STI symptom using propensity score matching method.

RESULTS

About 18% of sampled FSWs reported physical violence at the time of the survey. The likelihood of experiencing such violence was significantly higher among FSWs who solicited clients at public places, engaged in other economic activities apart from sex work, had savings, and reported high client volume per week. FSWs experiencing violence were also inconsistent condom users while engaging in sex with regular partners and clients. The average adjusted effect of violence clearly depicted an increase in the risk of any STI (11%, p<0.05) and multiple STIs (8%, p<0.10) and reduction in treatment seeking (10%, p<0.05).

CONCLUSIONS

This study demonstrates a significant effect of physical violence on reporting of any STI symptom and treatment seeking. Findings call for the immediate inclusion of strategies aimed to address violence related challenges in HIV prevention program currently being provided at Thane district. Such strategies would further help in enhancing the access to tailored STI prevention and care services among FSWs in the district.

HIV transmission biology: translation for HIV prevention

Rigorous testing of new HIV-prevention strategies is a time-consuming and expensive undertaking. Thus, making well informed decisions on which candidate-prevention approaches are most likely to provide the most benefit is critical to appropriately prioritizing clinical testing. In the case of biological interventions, the decision to test a given prevention approach in human trials rests largely on evidence of protection in preclinical studies. The ability of preclinical studies to predict efficacy in humans may depend on how well the model recapitulates key biological features of HIV transmission relevant to the question at hand. Here, we review our current understanding of the biology of HIV transmission based on data from animal models, cell culture, and viral sequence analysis from human infection. We summarize studies of the bottleneck in viral transmission; the characteristics of transmitted viruses; the establishment of infection; and the contribution of cell-free and cell-associated virus. We seek to highlight the implications of HIV-transmission biology for development of prevention interventions, and to discuss the limitations of existing preclinical models.

Human Alpha-Defensin HNP1 Increases HIV Traversal of the Epithelial Barrier: A Potential Role in STI-Mediated Enhancement of HIV Transmission

Alpha-defensins, including human neutrophil peptides 1-3 (HNP1-3) and human defensin 5 (HD5), are elevated at the genital mucosa in individuals with sexually transmitted infections (STIs). The presence of STIs is associated with an increased risk of human immunodeficiency virus (HIV) transmission, suggesting there may be a role for defensins in early events of HIV transmission. HD5 has been demonstrated to contribute to STI-mediated increased HIV infectivity in vitro. HNPs exhibit anti-HIV activity in vitro. However, increased levels of HNPs have been associated with enhanced HIV acquisition and higher viral load in breast milk. This study found that HNP1, but not HD5, significantly disrupted epithelial integrity and promoted HIV traversal of epithelial barriers. Linear HNP1 with the same charges did not affect epithelial permeability, indicating that the observed effect of HNP1 on the epithelial barrier was structure dependent. These results suggest a role for HNP1 in STI-mediated enhancement of HIV transmission.

In vitro antiretroviral activity and in vivo toxicity of the potential topical microbicide copper phthalocyanine sulfate

Background

Copper has antimicrobial properties and has been studied for its activity against viruses, including HIV. Copper complexed within a phthalocyanine ring, forming copper (II) phthalocyanine sulfate (CuPcS), may have a role in microbicide development when used intravaginally.

Methods

CuPcS toxicity was tested against cervical epithelial cells, TZM-BL cells, peripheral blood mononuclear cells (PBMC), and cervical explant tissues using cell viability assays. In vivo toxicity was assessed following intravaginal administration of CuPcS in female BALB/C mice and measured using a standardized histology grading system on reproductive tract tissues. Efficacy studies for preventing infection with HIV in the presence of various non-toxic concentrations of CuPcS were carried out in TZM-BL, PBMC, and cervical explant cultures using HIV-1_BAL and various pseudovirus subtypes. Non-linear regression was applied to the data to determine the EC50/90 and CC50/90.

Results

CuPcS demonstrated inhibition of HIV infection in PBMCs at concentrations that were non-toxic in cervical epithelial cells and PBMCs with EC50 values of approximately 50 μg/mL. Reproductive tract tissue analysis revealed no toxicity at 100 mg/mL. Human cervical explant tissues challenged with HIV in the presence of CuPcS also revealed a dose–response effect at preventing HIV infection at non-toxic concentrations with an EC50 value of 65 μg/mL.

Conclusion

These results suggest that CuPcS may be useful as a topical microbicide in concentrations that can be achieved in the female genital tract.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0358-5) contains supplementary material, which is available to authorized users.

Chemokine-mediated immune responses in the female genital tract mucosa

The genital tract mucosa is the site where sexually transmitted infections gain entry to the host. The immune response at this site is thus critical to provide innate protection against pathogens that are seen for the very first time as well as provide long-term pathogen-specific immunity, which would be required for an effective vaccine against sexually transmitted infection. A finely regulated immune response is therefore required to provide an effective barrier against pathogens without compromising the capacity of the genital tract to allow for successful conception and fetal development. We review recent developments in our understanding of the immune response in the female genital tract to infectious pathogens, using herpes simplex virus-2, human immunodeficiency virus-1 and Chlamydia trachomatis as examples, with a particular focus on the role of chemokines in orchestrating immune cell migration necessary to achieve effective innate and adaptive immune responses in the female genital tract.

Human T-Cell Development and Thymic Egress: An Infectious Disease Perspective

Emigration of mature naïve CD4 SP T cells from the human thymus to the periphery is not fully understood, although elucidation of the mechanisms that govern egress of T cells is crucial to understanding both basic immunology and the immune response in diseases such as HIV infection. Recent work has brought to light the requirement for sphingosine-1-phosphate (S1P) and its receptors in a variety of fields including mature naïve T-cell egress from the thymus of mice. We are examining the expression and function of this novel requisite T-cell egress receptor within the human thymus, characterizing changes observed in the expression and function of this receptor in infectious diseases. To perform this work, we use a variety of humanized murine models reviewed in this article. Future work in the field of T-cell egress, especially as it pertains to S1P receptors, should advance the fields of basic T-cell immunology and immunopathology and open new avenues for exploration into novel therapeutics.

Co-occurrence of Trichomonas vaginalis and bacterial vaginosis and vaginal shedding of HIV-1 RNA

BACKGROUND

Trichomonas vaginalis (TV) and bacterial vaginosis (BV) are independently associated with increased risk of vaginal shedding in HIV-positive women. Because these 2 conditions commonly co-occur, this study was undertaken to examine the association between TV/BV co-occurrence and vaginal shedding of HIV-1 RNA.

METHODS

HIV-positive women attending outpatient HIV clinics in 3 urban US cities underwent a clinical examination; were screened for TV, BV, Neisseria gonorrhoeae, Chlamydia trachomatis, and vulvovaginal candidiasis; and completed a behavioral survey. Women shedding HIV-1 RNA vaginally (≥50 copies/mL) were compared with women who had an undetectable (<50 copies/mL) vaginal viral load to determine if women who were TV positive and BV positive or had co-occurrence of TV/BV had higher odds of shedding vaginally when compared with women who did not have these conditions.

RESULTS

In this sample of 373 HIV-positive women, 43.1% (n = 161) had co-occurrence of TV/BV and 33.2% (n = 124) were shedding HIV-1 RNA vaginally. The odds of shedding HIV vaginally in the presence of TV alone or BV alone and when TV/BV co-occurred were 4.07 (95% confidence interval [CI], 1.78-9.37), 5.65 (95% CI, 2.64-12.01), and 18.63 (95% CI, 6.71-51.72), respectively, when compared with women with no diagnosis of TV or BV, and after adjusting for age, antiretroviral therapy status, and plasma viral load.

CONCLUSIONS

T. vaginalis and BV were independently and synergistically related to vaginal shedding of HIV-1 RNA. Screening and prompt treatment of these 2 conditions among HIV-positive women are important not only clinically but for HIV prevention, as well.

Vaginal challenge with an SIV-based dual reporter system reveals that infection can occur throughout the upper and lower female reproductive tract

The majority of new HIV infections occur in women as a result of heterosexual intercourse, overcoming multiple innate barriers to infection within the mucosa. However, the avenues through which infection is established, and the nature of bottlenecks to transmission, have been the source of considerable investigation and contention. Using a high dose of a single round non-replicating SIV-based vector containing a novel dual reporter system, we determined the sites of infection by the inoculum using the rhesus macaque vaginal transmission model. Here we show that the entire female reproductive tract (FRT), including the vagina, ecto- and endocervix, along with ovaries and local draining lymph nodes can contain transduced cells only 48 hours after inoculation. The distribution of infection shows that virions quickly disseminate after exposure and can access target cells throughout the FRT, with an apparent preference for infection in squamous vaginal and ectocervical mucosa. JRFL enveloped virions infect diverse CD4 expressing cell types, with T cells resident throughout the FRT representing the primary target. These findings establish a new perspective that the entire FRT is susceptible and virus can reach as far as the ovary and local draining lymph nodes. Based on these findings, it is essential that protective mechanisms for prevention of HIV acquisition must be present at protective levels throughout the entire FRT to provide complete protection.

There is currently a great effort world-wide to develop interventions such as vaccines and microbicides to decrease, or hopefully block, HIV transmission. To model the infection of women, the field utilizes the rhesus macaque vaginal transmission model. Understanding the initial events leading to infection after viral challenge of the female reproductive tract (FRT) is crucial for the development of functional prevention strategies. To this end, we developed a novel method for detecting infection in the rhesus macaque FRT after vaginal inoculation. This method utilizes single round replication defective vector that expresses dual reporter proteins, Luciferase and mCherry. Monitoring Luciferase expression allows us to identify the sites of infection within the intact FRT, while fluorescent protein mCherry allows us to visualize the single infected cells. Our studies revealed that virus can access the entire upper and lower reproductive tract. Infection occurs primarily in vaginal and ectocervical tissue, but can spread as far as the ovary and local draining lymph nodes. All classically defined susceptible cell types can be infected with the broadly tropic HIV envelope utilized in this study. Prevention strategies aimed at protecting from HIV infection should consider the entire FRT architecture as potentially susceptible and design interventions accordingly.

Mucosal immunity in the female genital tract, HIV/AIDS

Mucosal immunity consists of innate and adaptive immune responses which can be influenced by systemic immunity. Despite having been the subject of intensive studies, it is not fully elucidated what exactly occurs after HIV contact with the female genital tract mucosa. The sexual route is the main route of HIV transmission, with an increased risk of infection in women compared to men. Several characteristics of the female genital tract make it suitable for inoculation, establishment of infection, and systemic spread of the virus, which causes local changes that may favor the development of infections by other pathogens, often called sexually transmitted diseases (STDs). The relationship of these STDs with HIV infection has been widely studied. Here we review the characteristics of mucosal immunity of the female genital tract, its alterations due to HIV/AIDS, and the characteristics of coinfections between HIV/AIDS and the most prevalent STDs.

The regulation of inflammatory pathways and infectious disease of the cervix by seminal fluid

The connection between human papillomavirus (HPV) infection and the consequent sequelae which establishes cervical neoplastic transformation and invasive cervical cancer has redefined many aspects of cervical cancer research. However there is still much that we do not know. In particular, the impact of external factors, like seminal fluid in sexually active women, on pathways that regulate cervical inflammation and tumorigenesis, have yet to be fully understood. HPV infection is regarded as the initiating noninflammatory cause of the disease; however emerging evidence points to resident HPV infections as drivers of inflammatory pathways that play important roles in tumorigenesis as well as in the susceptibility to other infections such as human immunodeficiency virus (HIV) infection. Moreover there is emerging evidence to support a role for seminal fluid, in particular, the inflammatory bioactive lipids, and prostaglandins which are present in vast quantities in seminal fluid in regulating pathways that can exacerbate inflammation of the cervix, speed up tumorigenesis, and enhance susceptibility to HIV infection. This review will highlight some of our current knowledge of the role of seminal fluid as a potent driver of inflammatory and tumorigenic pathways in the cervix and will provide some evidence to propose a role for seminal plasma prostaglandins in HIV infection and AIDS-related cancer.

Regulation of mucosal immunity in the female reproductive tract: the role of sex hormones in immune protection against sexually transmitted pathogens

The immune system in the female reproductive tract (FRT) does not mount an attack against human immunodeficiency virus (HIV) or other sexually transmitted infections (STI) with a single endogenously produced microbicide or with a single arm of the immune system. Instead, the body deploys dozens of innate antimicrobials to the secretions of the FRT. Working together, these antimicrobials along with mucosal antibodies attack viral, bacterial, and fungal targets. Within the FRT, the unique challenges of protection against sexually transmitted pathogens coupled with the need to sustain the development of an allogeneic fetus, has evolved in such a way that sex hormones precisely regulate immune function to accomplish both tasks. The studies presented in this review demonstrate that estradiol (E2 ) and progesterone secreted during the menstrual cycle act both directly and indirectly on epithelial cells, fibroblasts and immune cells in the reproductive tract to modify immune function in a way that is unique to specific sites throughout the FRT. As presented in this review, studies from our laboratory and others demonstrate that the innate and adaptive immune systems are under hormonal control, that protection varies with the stage of the menstrual cycle and as such, is dampened during the secretory stage of the cycle to optimize conditions for fertilization and pregnancy. In doing so, a window of STI vulnerability is created during which potential pathogens including HIV enter the reproductive tract to infect host targets.

Pharmacokinetics and preliminary safety study of pod-intravaginal rings delivering antiretroviral combinations for HIV prophylaxis in a macaque model

Preexposure prophylaxis using oral regimens involving the HIV nucleoside reverse transcriptase inhibitors tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) demonstrated efficacy in three clinical trials. Adherence was determined to be a key parameter for success. Incorporation of the TDF-FTC combination into intravaginal rings (IVRs) for sustained mucosal delivery could increase product adherence and efficacy compared with those of oral and vaginal gel formulations. A novel pod-IVR technology capable of delivering multiple drugs is described; this constitutes the first report of an IVR delivering TDF and FTC, as well as a triple-combination IVR delivering TDF, FTC, and the entry inhibitor maraviroc (MVC). The pharmacokinetics and preliminary local safety of the two combination pod-IVRs were evaluated in the pig-tailed macaque model. The devices exhibited sustained release at controlled rates over the 28-day study period. Median steady-state drug levels in vaginal tissues in the TDF-FTC group were 30 μg g(-1) (tenofovir [TFV], in vivo hydrolysis product of TDF) and 500 μg g(-1) (FTC) and in the TDF-FTC-MVC group were 10 μg g(-1) (TFV), 150 μg g(-1) (FTC), and 20 μg g(-1) (MVC). No adverse events were observed, and there were no toxicological findings. Mild-to-moderate increases in inflammatory infiltrates were observed in the vaginal tissues of some animals in both the presence and the absence of the IVRs. The IVRs did not disturb the vaginal microbiota, and levels of proinflammatory cytokines remained stable throughout the study. Pod-IVR candidates based on the TDF-FTC combination have potential for the prevention of vaginal HIV acquisition and merit clinical investigation.

Effect of female genital schistosomiasis and anti-schistosomal treatment on monocytes, CD4+ T-cells and CCR5 expression in the female genital tract

Background

Schistosoma haematobium is a waterborne parasite that may cause female genital schistosomiasis (FGS), characterized by genital mucosal lesions. There is clinical and epidemiological evidence for a relationship between FGS and HIV. We investigated the impact of FGS on HIV target cell density and expression of the HIV co-receptor CCR5 in blood and cervical cytobrush samples. Furthermore we evaluated the effect of anti-schistosomal treatment on these cell populations.

Design

The study followed a case-control design with post treatment follow-up, nested in an on-going field study on FGS.

Methods

Blood and cervical cytobrush samples were collected from FGS negative and positive women for flow cytometry analyses. Urine samples were investigated for schistosome ova by microscopy and polymerase chain reaction (PCR).

Results

FGS was associated with a higher frequency of CD14⁺ cells (monocytes) in blood (11.5% in FGS+ vs. 2.2% in FGS-, p = 0.042). Frequencies of CD4⁺ cells expressing CCR5 were higher in blood samples from FGS+ than from FGS- women (4.7% vs. 1.5%, p = 0.018). The CD14⁺ cell population decreased significantly in both compartments after anti-schistosomal treatment (p = 0.043). Although the frequency of CD4+ cells did not change after treatment, frequencies of CCR5 expression by CD4+ cells decreased significantly in both compartments (from 3.4% to 0.5% in blood, p = 0.036; and from 42.4% to 5.6% in genital samples, p = 0.025).

Conclusions

The results support the hypothesis that FGS may increase the risk of HIV acquisition, not only through damage of the mucosal epithelial barrier, but also by affecting HIV target cell populations, and that anti-schistosomal treatment can modify this.

Oral and vaginal epithelial cell lines bind and transfer cell-free infectious HIV-1 to permissive cells but are not productively infected

The majority of HIV-1 infections worldwide are acquired via mucosal surfaces. However, unlike the vaginal mucosa, the issue of whether the oral mucosa can act as a portal of entry for HIV-1 infection remains controversial. To address potential differences with regard to the fate of HIV-1 after exposure to oral and vaginal epithelium, we utilized two epithelial cell lines representative of buccal (TR146) and pharyngeal (FaDu) sites of the oral cavity and compared them with a cell line derived from vaginal epithelium (A431) in order to determine (i) HIV-1 receptor gene and protein expression, (ii) whether HIV-1 genome integration into epithelial cells occurs, (iii) whether productive viral infection ensues, and (iv) whether infectious virus can be transferred to permissive cells. Using flow cytometry to measure captured virus by HIV-1 gp120 protein detection and western blot to detect HIV-1 p24 gag protein, we demonstrate that buccal, pharyngeal and vaginal epithelial cells capture CXCR4- and CCR5-utilising virus, probably via non-canonical receptors. Both oral and vaginal epithelial cells are able to transfer infectious virus to permissive cells either directly through cell-cell attachment or via transcytosis of HIV-1 across epithelial cells. However, HIV-1 integration, as measured by real-time PCR and presence of early gene mRNA transcripts and de novo protein production were not detected in either epithelial cell type. Importantly, both oral and vaginal epithelial cells were able to support integration and productive infection if HIV-1 entered via the endocytic pathway driven by VSV-G. Our data demonstrate that under normal conditions productive HIV-1 infection of epithelial cells leading to progeny virion production is unlikely, but that epithelial cells can act as mediators of systemic viral dissemination through attachment and transfer of HIV-1 to permissive cells.

Regulatory T Cells Diminish HIV Infection in Dendritic Cells - Conventional CD4(+) T Cell Clusters

Formation of immunological synapses (IS) between dendritic cells (DCs) and conventional CD4(+) T cells (Tcon) is critical for productive immune responses. However, when DCs are HIV-infected such synapses are critical to establish HIV infection. As regulatory T cells (Treg) control DC-Tcon interactions, we inquired whether Treg might interfere with DC to Tcon HIV infection. We developed a model, using monocyte-derived DC infected with R5-HIV, and cultured with Tcon in the presence or absence of autologous Treg, using the physiological ratio of 1 Treg for 10 Tcon. Cultures containing Treg significantly decreased HIV infection in DC:T cell clusters. Notably, Treg appear to have an effect on the quality of the IS, as Treg decreased actin polymerization and DC maturation. Importantly, Treg decreased the trafficking of HIV punctate to the IS. Further, CD152 and cyclic adenosine monophosphate were critical Treg effector molecules, as their individual or simultaneous blockade abolished Treg activity, however no additive effect was found. Together, these data suggest that Treg can reduce HIV dissemination, which may be beneficial to the host in the early stages of infection.

CCR5/CD4/CXCR4 oligomerization prevents HIV-1 gp120IIIB binding to the cell surface

CCR5 and CXCR4, the respective cell surface coreceptors of R5 and X4 HIV-1 strains, both form heterodimers with CD4, the principal HIV-1 receptor. Using several resonance energy transfer techniques, we determined that CD4, CXCR4, and CCR5 formed heterotrimers, and that CCR5 coexpression altered the conformation of both CXCR4/CXCR4 homodimers and CD4/CXCR4 heterodimers. As a result, binding of the HIV-1 envelope protein gp120IIIB to the CD4/CXCR4/CCR5 heterooligomer was negligible, and the gp120-induced cytoskeletal rearrangements necessary for HIV-1 entry were prevented. CCR5 reduced HIV-1 envelope-induced CD4/CXCR4-mediated cell-cell fusion. In nucleofected Jurkat CD4 cells and primary human CD4(+) T cells, CCR5 expression led to a reduction in X4 HIV-1 infectivity. These findings can help to understand why X4 HIV-1 strains infection affect T-cell types differently during AIDS development and indicate that receptor oligomerization might be a target for previously unidentified therapeutic approaches for AIDS intervention.

HIV-1 vaginal transmission: cell-free or cell-associated virus?

The vast majority of new HIV infections in male-to-female transmission occurs through semen, where HIV-1 is present in two different forms: as free and as cell-associated virus. In the female lower genital tract, semen mixes with female genital secretions that contain various factors, some of which facilitate or inhibit HIV-1 transmission. Next, HIV-1 crosses the genital epithelia, reaches the regional lymph nodes, and disseminates through the female host. Cervico-vaginal mucosa contains multiple barriers, resulting in a low probability of vaginal transmission. However, in some cases, HIV-1 is able to break these barriers. Although the exact mechanisms of how these barriers function remain unclear, their levels of efficiency against cell-free and cell-associated HIV-1 are different, and both cell-free and cell-associated virions seem to use different strategies to overcome these barriers. Understanding the basic mechanisms of HIV-1 vaginal transmission is required for the development of new antiviral strategies to contain HIV-1 epidemics.

HIV-1 infection: the role of the gastrointestinal tract

The intestinal mucosa has an important role as portal of entry during mother-to-child transmission of HIV-1 and during sexual transmission. Tissue morphology and integrity, as well as distribution of relevant cell types within the mucosa, spanning from the oropharynx to the rectum, can greatly influence viral infection, replication, presentation, and persistence. The relative contribution to transmission by cell-associated or cell-free virus is still not defined for the different routes of transmission. Although the main target cells for HIV-1 replication are the CD4+ T lymphocytes, which are rapidly depleted both in the periphery and in the mucosal tissues, dendritic cells, Langerhans' cells, and macrophages are players in each of these processes. The predominant cells involved may differ according to the tract of the gut and the route of transmission. The microenvironment of the intestinal mucosa, including mucus, antibodies, or chemo-cytokines, can as well influence infection and replication of the virus: their role is still under investigation. The understanding of these processes may help in developing efficient prevention strategies.

Dynamics analysis and simulation of a modified HIV infection model with a saturated infection rate

This paper studies a modified human immunodeficiency virus (HIV) infection differential equation model with a saturated infection rate. It is proved that if the basic virus reproductive number R 0 of the model is less than one, then the infection-free equilibrium point of the model is globally asymptotically stable; if R 0 of the model is more than one, then the endemic infection equilibrium point of the model is globally asymptotically stable. Based on the clinical data from HIV drug resistance database of Stanford University, using the proposed model simulates the dynamics of the two groups of patients' anti-HIV infection treatment. The numerical simulation results are in agreement with the evolutions of the patients' HIV RNA levels. It can be assumed that if an HIV infected individual's basic virus reproductive number R 0 < 1 then this person will recover automatically; if an antiretroviral therapy makes an HIV infected individual's R 0 < 1, this person will be cured eventually; if an antiretroviral therapy fails to suppress an HIV infected individual's HIV RNA load to be of unpredictable level, the time that the patient's HIV RNA level has achieved the minimum value may be the starting time that drug resistance has appeared.

Efficient transfer of HIV-1 in trans and in cis from Langerhans dendritic cells and macrophages to autologous T lymphocytes

OBJECTIVE

The chronology of HIV infection in mucosal tissue after sexual transmission is unknown. Several potential HIV target cells are present at these sites, including dendritic cells, macrophages, and CD4(+) T lymphocytes. Dendritic cells and macrophages are antigen-presenting cells (APCs) and are thus involved in cross-talk with T cells. This close contact may favor efficient HIV-1 transfer to T lymphocytes, resulting in rapid HIV-1 dissemination.

DESIGN

We investigated the role of APCs in HIV transfer to T cells by incubating Langerhans cells and interstitial dendritic cells (IDCs) or monocyte-derived macrophages (MDMs) with HIV for 2 h before addition of uninfected autologous CD4(+) T lymphocytes.

METHODS

HIV infection was recorded after different time points. Following staining, the measurement of intracellular p24 in the different cell populations was analyzed by flow cytometry.

RESULTS

We showed that Langerhans cells/IDCs and macrophages efficiently transferred HIV to CD4(+) T cells. Interestingly, a rapid HIV transfer in trans predominated in MDMs, whereas cis transfer mainly occurred in Langerhans cells/IDC cocultures. Neutralizing antibody 2G12, added to HIV-loaded APCs, efficiently blocked both the trans and the cis infection of T cells.

CONCLUSION

These findings highlight the major contributions of various mucosal cells in HIV dissemination and suggest that HIV hijacks the different properties of APCs to favor its dissemination through the body. They emphasize the role of macrophages in the rapid transmission of HIV to T lymphocytes at mucosal sites, dendritic cells being prone to migration to lymphoid organ for subsequent dissemination by cis transfer.