Setting the stage: host invasion by HIV

The Frequency of Vaccine-Induced T-Cell Responses Does Not Predict the Rate of Acquisition after Repeated Intrarectal SIVmac239 Challenges in Mamu-B*08+ Rhesus Macaques

Approximately 50% of rhesus macaques (RMs) expressing the major histocompatibility complex class I (MHC-I) allele Mamu-B*08 spontaneously control chronic-phase viremia after infection with the pathogenic simian immunodeficiency virus mac239 (SIVmac239) clone. CD8+ T-cell responses in these animals are focused on immunodominant Mamu-B*08-restricted SIV epitopes in Vif and Nef, and prophylactic vaccination with these epitopes increases the incidence of elite control in SIVmac239-infected Mamu-B*08-positive (Mamu-B*08+ ) RMs. Here we evaluated if robust vaccine-elicited CD8+ T-cell responses against Vif and Nef can prevent systemic infection in Mamu-B*08+ RMs following mucosal SIV challenges. Ten Mamu-B*08+ RMs were vaccinated with a heterologous prime/boost/boost regimen encoding Vif and Nef, while six sham-vaccinated MHC-I-matched RMs served as the controls for this experiment. Vaccine-induced CD8+ T cells against Mamu-B*08-restricted SIV epitopes reached high frequencies in blood but were present at lower levels in lymph node and gut biopsy specimens. Following repeated intrarectal challenges with SIVmac239, all control RMs became infected by the sixth SIV exposure. By comparison, four vaccinees were still uninfected after six challenges, and three of them remained aviremic after 3 or 4 additional challenges. The rate of SIV acquisition in the vaccinees was numerically lower (albeit not statistically significantly) than that in the controls. However, peak viremia was significantly reduced in infected vaccinees compared to control animals. We found no T-cell markers that distinguished vaccinees that acquired SIV infection from those that did not. Additional studies will be needed to validate these findings and determine if cellular immunity can be harnessed to prevent the establishment of productive immunodeficiency virus infection.IMPORTANCE It is generally accepted that the antiviral effects of vaccine-induced classical CD8+ T-cell responses against human immunodeficiency virus (HIV) are limited to partial reductions in viremia after the establishment of productive infection. Here we show that rhesus macaques (RMs) vaccinated with Vif and Nef acquired simian immunodeficiency virus (SIV) infection at a lower (albeit not statistically significant) rate than control RMs following repeated intrarectal challenges with a pathogenic SIV clone. All animals in the present experiment expressed the elite control-associated major histocompatibility complex class I (MHC-I) molecule Mamu-B*08 that binds immunodominant epitopes in Vif and Nef. Though preliminary, these results provide tantalizing evidence that the protective efficacy of vaccine-elicited CD8+ T cells may be greater than previously thought. Future studies should examine if vaccine-induced cellular immunity can prevent systemic viral replication in RMs that do not express MHC-I alleles associated with elite control of SIV infection.

Racial Discrimination, Protective Processes, and Sexual Risk Behaviors Among Black Young Males

Racial discrimination is a documented risk factor for sexual risk behaviors among young Black men. Mechanisms of effect and protective processes remain to be investigated. This study examined the mediating effect of emotional distress, self-regulation, and substance use on the association between racial discrimination and sexual risk behaviors. Sexual risk behaviors included in this study were inconsistent condom use and sexual concurrency (sexual partnerships that overlap overtime). The protective effect of protective social ties was also investigated. A sample of 505 heterosexually active men aged 19-22 years were recruited and surveyed for 3 time points. Men answered questions on racial discrimination, sexual risk behaviors, emotional distress, self-regulation, and substance use. Mediation and moderation models were tested. Racial discrimination (T1) significantly and positively predicted emotional distress (T2). Emotional distress, substance use, and self-regulation partially mediated the association between racial discrimination and sexual risk behaviors. Protective social ties attenuated the effects of emotional distress on substance use and self-regulation. Racial discrimination is an important context for sexual risk behaviors. Minority stress may translate to sexual risk behavior through psychosocial mediators, such as emotional distress, self-regulation, and substance use. Protective social ties may buffer against emotional distress to reduce substance use and increase self-regulation. The findings of this study can provide new insights through the investigation of risk and protective processes that influence sexual risk behaviors among young Black men.

Physiological Changes from Violence-Induced Stress and Trauma Enhance HIV Susceptibility Among Women

PURPOSE OF REVIEW

This theoretical review identifies physiological mechanisms by which violence against women (VAW) may increase women's susceptibility to HIV through trauma, stress, and immune dysfunction.

RECENT FINDINGS

Research documents systemic and local immune responses are related to stress and trauma from abuse across the life course (i.e., childhood, IPV, adulthood re-victimization). Findings are interpreted within a theoretical framework grounded in the Social Stress Theory and the concept of toxic stress, and highlight the current state of the science connecting: (1) VAW to the physiological stress response and immune dysfunction, and (2) the physiological stress response and inflammation to HIV susceptibility and infection in the female reproductive tract. Despite a dearth of research in human subjects, evidence suggests that VAW plays a significant role in creating a physiological environment conducive to HIV infection. We conclude with a discussion of promising future steps for this line of research.

Type I IFNs in the female reproductive tract: The first line of defense in an ever-changing battleground

The primary function of the female reproductive tract (FRT) is to enable successful reproduction, yet the biologic mechanisms required to accomplish this, which include fluctuating sex hormones and tolerance of semen and a semi-allogeneic fetus, can leave this unique mucosal environment susceptible to pathogenic challenge. Consequently, the FRT has evolved specialized innate and adaptive immune responses tailored to protecting itself from infection without compromising reproductive success. A family of innate immune cytokines that has emerged as important regulators of these immune responses is the type I IFNs. Type I IFNs are typically rapidly produced in response to pathogenic stimulation and are capable of sculpting pleotropic biologic effects, including immunomodulation, antiproliferative effects, and inducing antiviral and bactericidal molecules. Here, we review what is currently known about type I IFN-mediated immunity in the FRT in human, primate, and murine models and explore their importance with respect to three highly relevant FRT infections: HIV, Zika, and Chlamydia.

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.

HIV-1 intron-containing RNA expression induces innate immune activation and T cell dysfunction

Low levels of type I interferon (IFN-I) are thought to be a driving force for immune activation and T-cell exhaustion in HIV-1 infected individuals on combination antiretroviral therapy (cART), though the causative mechanisms for persistent IFN-I signaling have remained unclear. Here, we show Rev–CRM1-dependent nuclear export and peripheral membrane association of intron-containing HIV-1 RNA, independent of primary viral sequence or viral protein expression, is subject to sensing and signaling via MAVS, resulting in IFN-I-dependent pro-inflammatory responses in macrophages. Additionally, HIV-1 intron-containing-RNA-induced innate immune activation of macrophages leads to upregulation of inhibitory receptor expression and functional immune exhaustion of co-cultured T cells. Our findings suggest that persistent expression of HIV-1 intron-containing RNA in macrophages contributes to chronic immune activation and T-cell dysfunction and that use of HIV RNA expression inhibitors as adjunct therapy might abrogate aberrant inflammation and restore immune function in HIV-infected individuals on cART.

Type I Interferon is thought to be a driving force for immune activation and T cell exhaustion during HIV infection. Here the authors show that intron-containing HIV RNA induces innate immune activation resulting in associated T cell dysfunction.

HIV-1 cell-to-cell transmission and broadly neutralizing antibodies

HIV-1 spreads through contacts between infected and target cells. Polarized viral budding at the contact site forms the virological synapse. Additional cellular processes, such as nanotubes, filopodia, virus accumulation in endocytic or phagocytic compartments promote efficient viral propagation. Cell-to-cell transmission allows immune evasion and likely contributes to HIV-1 spread in vivo. Anti-HIV-1 broadly neutralizing antibodies (bNAbs) defeat the majority of circulating viral strains by binding to the viral envelope glycoprotein (Env). Several bNAbs have entered clinical evaluation during the last years. It is thus important to understand their mechanism of action and to determine how they interact with infected cells. In experimental models, HIV-1 cell-to-cell transmission is sensitive to neutralization, but the effect of antibodies is often less marked than during cell-free infection. This may be due to differences in the conformation or accessibility of Env at the surface of virions and cells. In this review, we summarize the current knowledge on HIV-1 cell-to-cell transmission and discuss the role of bNAbs during this process.

Similar Epitope Specificities of IgG and IgA Antibodies Elicited by Ad26 Vector Prime, Env Protein Boost Immunizations in Rhesus Monkeys

Vaccine-elicited immunoglobulin G (IgG) has been shown to be important for protection against simian-human immunodeficiency virus (SHIV) infection in rhesus monkeys. However, it remains unclear whether vaccine-elicited IgA responses are beneficial or detrimental for protection. In this study, we evaluated the kinetics, magnitude, breadth, and linear epitope specificities of vaccine-elicited IgG and IgA responses in serum and mucosal secretions following intramuscular immunization with adenovirus 26 (Ad26) prime, Env protein boost vaccination regimens. The systemic and mucosal antibody responses exhibited kinetics similar to those of the serum antibody responses but lower titers than the serum antibody responses. Moreover, the IgG and IgA responses were correlated, both in terms of the magnitude of the responses and in terms of the antibody specificities against linear human immunodeficiency virus type 1 (HIV-1) Env, Gag, and Pol epitopes. These data suggest that IgG and IgA responses are highly coordinated in both peripheral blood and mucosal compartments following Ad26/Env vaccination in rhesus monkeys.IMPORTANCE Vaccine-elicited IgG responses are important for protection against simian-human immunodeficiency virus (SHIV) infection in nonhuman primates. However, much less is known about the role and function of IgA, despite it being the predominant antibody in mucosal sites. There is debate as to whether HIV-1-specific IgA responses are beneficial or detrimental, since serum anti-Env IgA titers were shown to be inversely correlated with protection in the RV144 clinical trial. We thus assessed vaccine-elicited IgG and IgA antibody responses in peripheral blood and mucosal secretions following vaccination with the Ad26/Env vaccine.

HIV transmission from infected CD4+ T cells to allogenic T and dendritic cells is inhibited by broadly neutralizing antibodies

OBJECTIVE

In the semen, both free virus and infected cells are able to establish HIV infection during sexual intercourse. An efficient vaccine should therefore inhibit both infectious states. The aim of this study was to analyze the capacity of broadly neutralizing antibodies (bNAbs) to inhibit HIV transmission by the infected cells.

DESIGN/METHODS

We developed an in-vitro model aiming to mimic mucosal HIV transmission via infected cells. PHA-activated CD4+ T cells stained with PKH26 from donor A were infected and co-cultured with CD4+ T cells and dendritic cells from donor B in the presence of bNAbs.

RESULTS

We showed that dendritic cells were the preferential HIV target cells at early time points in this co-culture model. In the context of this co-culture model where infection and transmission occurred simultaneously, bNAbs efficiently inhibited HIV replication as well as HIV transmission from infected cells to allogenic dendritic cells and CD4+ T cells.

CONCLUSION

Overall, our results indicate that dendritic cells, in addition to CD4+ T cells, are key cells that are efficiently infected by HIV and bNAbs are potent inhibitors of infection of both target cells. Future HIV prophylactic vaccine design should develop immune strategies able to prevent the infection of dendritic cells, in addition to the inhibition of CD4+ T-cell infection.

On-demand microbicide products: design matters

Sexual intercourse (vaginal and anal) is the predominant mode of human immunodeficiency virus (HIV) transmission. Topical microbicides used in an on-demand format (i.e., immediately before or after sex) can be part of an effective tool kit utilized to prevent sexual transmission of HIV. The effectiveness of prevention products is positively correlated with adherence, which is likely to depend on user acceptability of the product. The development of an efficacious and acceptable product is therefore paramount for the success of an on-demand product. Acceptability of on-demand products (e.g., gels, films, and tablets) and their attributes is influenced by a multitude of user-specific factors that span behavioral, lifestyle, socio-economic, and cultural aspects. In addition, physicochemical properties of the drug, anatomical and physiological aspects of anorectal and vaginal compartments, issues relating to large-scale production, and cost can impact product development. These factors together with user preferences determine the design space of an effective, acceptable, and feasible on-demand product. In this review, we summarize the interacting factors that together determine product choice and its target product profile.

What Is the Predictive Value of Animal Models for Vaccine Efficacy in Humans? Rigorous Simian Immunodeficiency Virus Vaccine Trials Can Be Instructive

Simian immunodeficiency virus (SIV) challenge of rhesus macaques provides an invaluable tool to evaluate the clinical prospects of HIV-1 vaccine concepts. However, as with any animal model of human disease, it is crucial to understand the advantages and limitations of this system to maximize the translational value of SIV vaccine studies. Here, we discuss the importance of assessing the efficacy of vaccine prototypes using stringent SIV challenge regimens that mimic HIV-1 transmission and pathogenesis. We also review some of the cautionary tales of HIV-1 vaccine research because they provide general lessons for the preclinical assessment of vaccine candidates.

Pharmaceutical interactions between antiretroviral and antimalarial drugs used in chemoprophylaxis

Human immunodeficiency virus (HIV) is the causative agent of the Acquired Immunodeficiency Syndrome (AIDS). The pandemic is believed to have originated within the Northern Congo basin covering large parts of the Democratic Republic of Congo, the Republic of Congo, the Central African Republic, Cameroon and Gabon. Although over decades, HIV-1 has spread throughout the World leaving no country unaffected, sub-Saharan Africa remains the region with more than 80% of all infected individuals. The HIV-2 epidemic has largely remained restricted to West Africa along the Upper Guinean forests. Co-incident with these regions of highest HIV distribution is a part of the malaria belt and therefore, co-infections are common. In this review we carve out the consequences of HIV transmission prevention and synchronous malaria prophylaxis during occupational or leisure travelling activities within this World region. In particular, we elaborate on considering pre-existing drug resistances of both, the malaria parasites and the immunodeficiency viruses, when determining a combination for prophylactic and, if necessary, post-expositional measures with a focus on the compatibility of both medications.

Hormonal Contraception and HIV-1 Acquisition: Biological Mechanisms

Access to effective affordable contraception is critical for individual and public health. A wide range of hormonal contraceptives (HCs), which differ in composition, concentration of the progestin component, frequency of dosage, and method of administration, is currently available globally. However, the options are rather limited in settings with restricted economic resources that frequently overlap with areas of high HIV-1 prevalence. The predominant contraceptive used in sub-Saharan Africa is the progestin-only three-monthly injectable depot medroxyprogesterone acetate. Determination of whether HCs affect HIV-1 acquisition has been hampered by behavioral differences potentially confounding clinical observational data. Meta-analysis of these studies shows a significant association between depot medroxyprogesterone acetate use and increased risk of HIV-1 acquisition, raising important concerns. No association was found for combined oral contraceptives containing levonorgestrel, nor for the two-monthly injectable contraceptive norethisterone enanthate, although data for norethisterone enanthate are limited. Susceptibility to HIV-1 and other sexually transmitted infections may, however, be dependent on the type of progestin present in the formulation. Several underlying biological mechanisms that may mediate the effect of HCs on HIV-1 and other sexually transmitted infection acquisition have been identified in clinical, animal, and ex vivo studies. A substantial gap exists in the translation of basic research into clinical practice and public health policy. To bridge this gap, we review the current knowledge of underlying mechanisms and biological effects of commonly used progestins. The review sheds light on issues critical for an informed choice of progestins for the identification of safe, effective, acceptable, and affordable contraceptive methods.

Higher sequence diversity in the vaginal tract than in blood at early HIV-1 infection

In the majority of cases, human immunodeficiency virus type 1 (HIV-1) infection is transmitted through sexual intercourse. A single founder virus in the blood of the newly infected donor emerges from a genetic bottleneck, while in rarer instances multiple viruses are responsible for systemic infection. We sought to characterize the sequence diversity at early infection, between two distinct anatomical sites; the female reproductive tract vs. systemic compartment. We recruited 72 women from Uganda and Zimbabwe within seven months of HIV-1 infection. Using next generation deep sequencing, we analyzed the total genetic diversity within the C2-V3-C3 envelope region of HIV-1 isolated from the female genital tract at early infection and compared this to the diversity of HIV-1 in plasma. We then compared intra-patient viral diversity in matched cervical and blood samples with three or seven months post infection. Genetic analysis of the C2-V3-C3 region of HIV-1 env revealed that early HIV-1 isolates within blood displayed a more homogeneous genotype (mean 1.67 clones, range 1–5 clones) than clones in the female genital tract (mean 5.7 clones, range 3–10 clones) (p<0.0001). The higher env diversity observed within the genital tract compared to plasma was independent of HIV-1 subtype (A, C and D). Our analysis of early mucosal infections in women revealed high HIV-1 diversity in the vaginal tract but few transmitted clones in the blood. These novel in vivo finding suggest a possible mucosal sieve effect, leading to the establishment of a homogenous systemic infection.

During chronic HIV-1 infection, high viral diversity can be found in the blood and semen of donors. However, a single HIV-1 clone establishes productive infection in the recipient following heterosexual transmission. To investigate the genetic bottleneck occurring at the earliest stages of heterosexual HIV-1 transmission, we characterized the HIV-1 envelope sequence diversity at very early and early stages of infection in the female reproductive tract and matched plasma samples from a cohort of Ugandan and Zimbabwean women. A more diverse viral population was observed in the endocervical swab samples compared to plasma. Endocervical samples harbored a larger number of viral clones, while in the majority of plasma samples only a single clone was present early in infection. Interestingly, these observations were independent of HIV-1 subtype, hormonal contraceptive use or the number of sex acts and partners. Furthermore, in the cases of higher HIV-1 diversity in the blood during early infection, faster CD4 T cell decline were observed during chronic disease suggesting faster disease progression. Our findings provide novel in vivo evidence for the existence of an intra-patient genetic bottleneck restricting the HIV-1 from the vaginal tract to the blood during early heterosexual HIV-1 transmission.

Barriers to HIV Cure

Since the beginning of the epidemic, more than 70 million people have been infected with human immunodeficiency virus (HIV) and about 38 million have died from acquired immune deficiency syndrome (AIDS)-related illnesses. While the discovery of highly active antiretroviral therapy (HAART) in the mid 90's has saved millions of lives, a complete eradication of HIV is still not possible as HIV can persist for decades in a small reservoir of latently infected cells. Once reactivated, these latently infected cells can actively produce viral particles. Recent studies suggest that several sanctuaries exist within infected individuals where HIV can remain undetected by the immune system. These cellular, anatomical and microanatomical viral reservoirs represent a major obstacle for the eradication of HIV. Here we review recent findings on potential sanctuaries of HIV and address potential avenues to overcome these immunological barriers.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

Isolation of human lymphocytes with high yield and viability from the gastrointestinal and female reproductive tract of a humanized DRAG mouse

The mucosal tissues of the gut and female reproductive tract (FRT) are susceptible to pathogen infections including bacteria, viruses, and parasites, and are also the targets for immune disorders such as Crohn's disease, inflammatory bowel disease (IBD), and many types of cancers. However, the role of the mucosal immune cells to control these diseases is largely unknown. The limited availability of human mucosal biopsy tissue and the low number of cells that can be isolated from these tissues hampers the characterization of the phenotype and function of human mucosal immune cell subsets. Therefore, human-immune-system humanized mice are surrogate models to investigate the human mucosal immune cell responses during the course of the disease. The current protocols used to harvest the immune cells from the mucosal tissues, however, result in low recovery of cells with poor viability. We have established a novel protocol, which results in a high yield of human lymphocytes with high viability to overcome this issue. The immune cells obtained from a single DRAG mouse by our protocol were sufficient for conducting functional assays and for flow cytometry analyses including phenotypic, exhaustion, and functional panels.

The Effect of Commonly Used Excipients on the Epithelial Integrity of Human Cervicovaginal Tissue

Pharmaceutical excipients are widely used in vaginal drug products. The epithelial integrity of the cervicovaginal tissue is important for HIV-1 prevention. However, the effects of excipients on cervicovaginal epithelium remain unknown. This study aims at assessing the effects of vaginal product excipients on the integrity of human cervicovaginal epithelium and on a lead HIV prevention antiretroviral drug, tenofovir (TFV). In the current study, nine excipients commonly used in vaginal formulations were incubated for 6 h with excised human ectocervical tissue. The effects of the excipients were examined by measuring the transepithelial electrical resistance (TEER), epithelial morphology, paracellular/transcellular permeability, and cell viability. The efficacy of TFV for preventing HIV-1 infection in the ex vivo cultured ectocervix was also tested. We found that disodium ethyl-enediaminetetraacetate (EDTA), sorbic acid, and benzoic acid had no effect on the tissue TEER. Butylated hydroxyanisole, glycerin, propylene glycol, methylparaben, and propylparaben slightly to moderately decreased tissue TEER, whereas citric acid significantly decreased the TEER in a time-dependent manner. Tissue morphology observed post-exposure strongly correlated with TEER data; however, a less strong correlation was observed between paracellular permeability and TEER data after exposure to different excipients. In addition, treatment with EDTA, methylparaben, and propylene glycol at tested levels had no effect on the efficacy of TFV in preventing tissue HIV-1 infection. In conclusion, the combined measurements of TEER, morphology, permeability, and viability using human cervicovaginal tissue represent a clinically relevant platform for safety evaluation of excipients and formulated products for HIV-1 prevention.

HbAHP-25 attenuates HIV-1 gp120 mediated inflammation and barrier dysfunction

OBJECTIVES

Development of HbAHP-25, a peptide that prevents HIV-1 entry into cells by blocking gp120-CD4 interaction, as a topical anti-HIV drug, necessitates that it is first tested for toxic or abrasive effects on genital epithelial cells and also on the vaginal microbiome. The present study was, therefore, undertaken to investigate whether: (1) HbAHP-25 has any adverse effect on growth and membrane integrity of various cell lines, and (2) HbAHP-25 neutralizes gp120 mediated insults on genital epithelial cells.

METHODS

MTT and trans-epithelial resistance (TER) assays were performed to assess the viability and integrity of epithelial cells. Real-time PCR and Immunofluorescence/Western blotting were used to decipher the expression of tight junction proteins, at the mRNA and protein levels, respectively. A multiplex cytokine assay was performed to quantify the cytokines.

RESULTS

HbAHP-25 had no adverse effect on the viability of VK2/E6E7, End1/E6E7, Ect1/E6E7 and HEC-1A cells, and also on growth of lactobacilli. The barrier integrity of HbAHP-25-treated cells remained unaltered. Expression of tight junction proteins, Claudin-1 and ZO-1, at transcript and protein levels, remained unaltered in HbAHP-25-treated HEC-1A cells. Interestingly, HbAHP-25 treatment prevented the breach of barrier integrity caused by gp120. Further, HbAHP-25 did not elicit the expression of inflammatory cytokines. Instead, the in vitro induction of inflammatory cytokines by gp120 was also abrogated in the presence of HbAHP-25.

CONCLUSION

HbAHP-25 is exceedingly safe to genital epithelial cells and attenuates HIV-1 gp120-mediated barrier dysfunction by limiting excessive inflammation. This study provides significant evidences in the favor of HbAHP-25's potential as a topical anti-HIV agent.

Frequency of Human CD45+ Target Cells is a Key Determinant of Intravaginal HIV-1 Infection in Humanized Mice

Approximately 40% of HIV-1 infections occur in the female genital tract (FGT), primarily through heterosexual transmission. FGT factors determining outcome of HIV-1 exposure are incompletely understood, limiting prevention strategies. Here, humanized NOD-Rag1^−/− γc^−/− mice differentially reconstituted with human CD34+ -enriched hematopoietic stem cells (Hu-mice), were used to assess target cell frequency and viral inoculation dose as determinants of HIV-1 infection following intravaginal (IVAG) challenge. Results revealed a significant correlation between HIV-1 susceptibility and hCD45+ target cells in the blood, which correlated with presence of target cells in the FGT, in the absence of local inflammation. HIV-1 plasma load was associated with viral dose at inoculation and frequency of target cells. Events following IVAG HIV-1 infection; viral dissemination and CD4 depletion, were not affected by these parameters. Following IVAG inoculation, HIV-1 titres peaked, then declined in vaginal lavage while plasma showed a reciprocal pattern. The greatest frequency of HIV-1-infected (p24+) cells were found one week post-infection in the FGT versus blood and spleen, suggesting local viral amplification. Five weeks post-infection, HIV-1 disseminated into systemic tissues, in a dose-dependent manner, followed by depletion of hCD45+ CD3+ CD4+ cells. Results indicate target cell frequency in the Hu-mouse FGT is a key determinant of HIV-1 infection, which might provide a useful target for prophylaxis in women.

Medroxyprogesterone acetate-treated human, primary endometrial epithelial cells reveal unique gene expression signature linked to innate immunity and HIV-1 susceptibility

PROBLEM

Medroxyprogesterone acetate (MPA), a progestin-based hormonal contraceptive designed to mimic progesterone, has been linked to increased human immunodeficiency virus (HIV-1) susceptibility. Genital epithelial cells (GECs) form the mucosal lining of the female genital tract (FGT) and provide the first line of protection against HIV-1. The impact of endogenous sex hormones or MPA on the gene expression profile of GECs has not been comprehensively documented.

METHOD OF STUDY

Using microarray analysis, we characterized the transcriptional profile of primary endometrial epithelial cells grown in physiological levels of E2, P4, and MPA.

RESULTS

Each hormone treatment altered the gene expression profile of GECs in a unique manner. Interestingly, although MPA is a progestogen, the gene expression profile induced by it was distinct from P4. MPA increased gene expression of genes related to inflammation and cholesterol synthesis linked to innate immunity and HIV-1 susceptibility.

CONCLUSION

The analysis of gene expression profiles provides insights into the effects of sex hormones and MPA on GECs and allows us to posit possible mechanisms of the MPA-mediated increase in HIV-1 acquisition.

Evaluation of Different Parameters of Humoral and Cellular Immune Responses in HIV Serodiscordant Heterosexual Couples: Humoral Response Potentially Implicated in Modulating Transmission Rates

As the HIV/AIDS pandemic still progresses, understanding the mechanisms governing viral transmission as well as protection from HIV acquisition is fundamental. In this context, cohorts of HIV serodiscordant heterosexual couples (SDC) represent a unique tool. The present study was aimed to evaluate specific parameters of innate, cellular and humoral immune responses in SDC. Specifically, plasma levels of cytokines and chemokines, HIV-specific T-cell responses, gp120-specific IgG and IgA antibodies, and HIV-specific antibody-dependent cellular cytotoxicity (ADCC) activity were assessed in nine HIV-exposed seronegative individuals (ESN) and their corresponding HIV seropositive partners (HIV⁺-P), in eighteen chronically infected HIV subjects (C), nine chronically infected subjects known to be HIV transmitters (CT) and ten healthy HIV⁻ donors (HD). Very low magnitude HIV-specific cellular responses were found in two out of six ESN. Interestingly, HIV⁺-P had the highest ADCC magnitude, the lowest IgA levels and the highest IgG/IgA ratio, all compared to CT. Positive correlations between CD4⁺ T-cell counts and both IgG/IgA ratios and %ADCC killing uniquely distinguished HIV⁺-P. Additionally, evidence of IgA interference with ADCC responses from HIV⁺-P and CT is provided. These data suggest for the first time a potential role of ADCC and/or gp120-specific IgG/IgA balance in modulating heterosexual transmission. In sum, this study provides key information to understand the host factors that influence viral transmission, which should be considered in both the development of prophylactic vaccines and novel immunotherapies for HIV-1 infection.

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The evaluation of different immune parameters in HIV serodiscordant couples helped identify factors shaping transmission.

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Innate and cellular immune responses were apparently not involved in this scenario.

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HIV-specific ADCC, IgA titer and IgG/IgA balance were identified as factors involved in modulating viral transmission.

The existence of individuals that remain HIV negative despite being repeatedly exposed to the virus has long been described. To date, only homozygosis for a 32-base pair deletion in the ccr5 gene has been consistently shown to be a determinant of HIV resistance. Still, subjects bearing the WT ccr5 gene have also been described as resistant or less susceptible to HIV. Thus, other mechanisms must be involved in this phenomenon. The results presented here postulate ADCC and IgG/IgA ratio as potential mechanisms involved in modulating HIV transmission in the context of serodiscordant couples and inspire further investigations.

The History of the HIV/AIDS Epidemic in Africa

HIV testing of African immigrants in Belgium showed that HIV existed among Africans by 1983. However, the epidemic was recognized much later in most parts of sub-Saharan Africa (SSA) due to stigma and perceived fear of possible negative consequences to the countries' economies. This delay had devastating mortality, morbidity, and social consequences. In countries where earlier recognition occurred, political leadership was vital in mounting a response. The response involved establishment of AIDS control programs and research on the HIV epidemiology and candidate preventive interventions. Over time, the number of effective interventions has grown; the game changer being triple antiretroviral therapy (ART). ART has led to a rapid decline in HIV-related morbidity and mortality in addition to prevention of onward HIV transmission. Other effective interventions include safe male circumcision, pre-exposure prophylaxis, and post-exposure prophylaxis. However, since none of these is sufficient by itself, delivering a combination package of these interventions is important for ending the HIV epidemic as a public health threat.

Interferon-Inducible CD169/Siglec1 Attenuates Anti-HIV-1 Effects of Alpha Interferon

A hallmark of human immunodeficiency virus type 1 (HIV-1) infection in vivo is chronic immune activation concomitant with type I interferon (IFN) production. Although type I IFN induces an antiviral state in many cell types, HIV-1 can replicate in vivo via mechanisms that have remained unclear. We have recently identified a type I IFN-inducible protein, CD169, as the HIV-1 attachment factor on dendritic cells (DCs) that can mediate robust infection of CD4⁺ T cells in trans Since CD169 expression on macrophages is also induced by type I IFN, we hypothesized that type I IFN-inducible CD169 could facilitate productive HIV-1 infection in myeloid cells in cis and CD4⁺ T cells in trans and thus offset antiviral effects of type I IFN. In support of this hypothesis, infection of HIV-1 or murine leukemia virus Env (MLV-Env)-pseudotyped HIV-1 particles was enhanced in IFN-α-treated THP-1 monocytoid cells, and this enhancement was primarily dependent on CD169-mediated enhancement at the virus entry step, a phenomenon phenocopied in HIV-1 infections of IFN-α-treated primary monocyte-derived macrophages (MDMs). Furthermore, expression of CD169, a marker of type I IFN-induced immune activation in vivo, was enhanced in lymph nodes from pigtailed macaques infected with simian immunodeficiency virus (SIV) carrying HIV-1 reverse transcriptase (RT-SHIV), compared to uninfected macaques, and interestingly, there was extensive colocalization of p27^gag and CD169, suggesting productive infection of CD169⁺ myeloid cells in vivo While cell-free HIV-1 infection of IFN-α-treated CD4⁺ T cells was robustly decreased, initiation of infection in trans via coculture with CD169⁺ IFN-α-treated DCs restored infection, suggesting that HIV-1 exploits CD169 in cis and in trans to attenuate a type I IFN-induced antiviral state.IMPORTANCE HIV-1 infection in humans causes immune activation characterized by elevated levels of proinflammatory cytokines, including type I interferons (IFN). Although type I IFN induces an antiviral state in many cell types in vitro, HIV-1 can replicate in vivo via mechanisms that have remained unclear. In this study, we tested the hypothesis that CD169, a type I IFN-inducible HIV-1 attachment factor, offsets antiviral effects of type I IFN. Infection of HIV-1 was rescued in IFN-α-treated myeloid cells via upregulation of CD169 and a subsequent increase in CD169-dependent virus entry. Furthermore, extensive colocalization of viral Gag and CD169 was observed in lymph nodes of infected pigtailed macaques, suggesting productive infection of CD169⁺ cells in vivo Treatment of dendritic cell (DC)-T cell cocultures with IFN-α upregulated CD169 expression on DCs and rescued HIV-1 infection of CD4⁺ T cells in trans, suggesting that HIV-1 exploits CD169 to attenuate type I IFN-induced restrictions.

Mucus and Mucins: do they have a role in the inhibition of the human immunodeficiency virus?

BACKGROUND

Mucins are large O-linked glycosylated proteins which give mucus their gel-forming properties. There are indications that mucus and mucins in saliva, breast milk and in the cervical plug inhibit the human immunodeficiency virus (HIV-1) in an in vitro assay. Crude mucus gels form continuous layers on the epithelial surfaces of the major internal tracts of the body and protect these epithelial surfaces against aggressive luminal factors such as hydrochloric acid and pepsin proteolysis in the stomach lumen, the movement of hard faecal pellets in the colon at high pressure, the effects of shear against the vaginal epithelium during intercourse and the presence of foreign substances in the respiratory airways. Tumour-associated epitopes on mucins make them suitable as immune-targets on malignant epithelial cells, rendering mucins important as diagnostic and prognostic markers for various diseases, even influencing the design of mucin-based vaccines. Sub-Saharan Africa has the highest prevalence of HIV-AIDS in the world. The main points of viral transmission are via the vaginal epithelium during sexual intercourse and mother-to-child transmission during breast-feeding. There have been many studies showing that several body fluids have components that prevent the transmission of HIV-1 from infected to non-infected persons through various forms of contact. Crude saliva and its purified mucins, MUC5B and MUC7, and the purified mucins from breast milk, MUC1 and MUC4 and pregnancy plug cervical mucus (MUC2, MUC5AC, MUC5B and MUC6), inhibit HIV-1 in an in vitro assay. There are conflicting reports of whether crude breast-milk inhibits HIV-1 in an in vitro assay. However studies with a humanised BLT mouse show that breast-milk does inhibit HIV and that breast-feeding is still advisable even amongst HIV-positive women in under-resourced areas, preferably in conjunction with anti-retroviral treatment.

CONCLUSION

These findings raise questions of how such a naturally occurring biological substance such as mucus, with remarkable protective properties of epithelial surfaces against aggressive luminal factors in delicate locations, could be used as a tool in the fight against HIV-AIDS, which has reached epidemic proportions in sub-Saharan Africa.

Preliminary studies on the use of pertussis toxin for the modulation of intravaginal SIV transmission in rhesus macaques

BACKGROUND

Pertussis toxin (PTX) blocks GPCR signaling resulting in the inhibition of chemotaxis/cell adhesion. It was reasoned that inhibition of cell trafficking may be an approach to prevent HIV/SIV transmission.

METHODS

In this study, PTX in HEC gel was applied to the vaginal wall of monkeys that were then challenged intravaginally with SIVmac251.

RESULTS

Results of these studies showed that 2 of 4 animals were resistant to infection. Furthermore, infection was correlated with a marked increase in the plasma and cervicovaginal lavage levels of select chemokines and cytokines.

CONCLUSIONS

Results from this preliminary feasibility study dictate that further studies that include a larger number of animals are required to optimize this protocol and establish the efficacy of this approach. In addition, such future studies will provide important information on the role of specific chemokines that play a role in lymphocyte trafficking within the genital tract and serve as additional therapeutic targets.

Role of sex hormones and the vaginal microbiome in susceptibility and mucosal immunity to HIV-1 in the female genital tract

While the prevalence of Human immunodeficiency virus-1 (HIV-1) infection has stabilized globally, it continues to be the leading cause of death among women of reproductive age. The majority of new infections are transmitted heterosexually, and women have consistently been found to be more susceptible to HIV-1 infection during heterosexual intercourse compared to men. This emphasizes the need for a deeper understanding of how the microenvironment in the female genital tract (FGT) could influence HIV-1 acquisition. This short review focuses on our current understanding of the interplay between estrogen, progesterone, and the cervicovaginal microbiome and their immunomodulatory effects on the FGT. The role of hormonal contraceptives and bacterial vaginosis on tissue inflammation, T cell immunity and HIV-1 susceptibility is discussed. Taken together, this review provides valuable information for the future development of multi-purpose interventions to prevent HIV-1 infection in women.

The biology of how circumcision reduces HIV susceptibility: broader implications for the prevention field

Circumcision reduces heterosexual HIV-1 acquisition in men by at least 60%. However, the biological mechanisms by which circumcision is protective remain incompletely understood. We test the hypothesis that the sub-preputial microenvironment created by the foreskin drives immune activation in adjacent foreskin tissues, facilitating HIV-1 infection through a combination of epithelial barrier disruption, enhanced dendritic cell maturation, and the recruitment/activation of neutrophils and susceptible CD4 T cell subsets such as Th17 cells. Furthermore, we provide evidence that the genital microbiome may be an important driver of this immune activation. This suggests that new modalities to reduce genital immune activation and/or alter the genital microbiome, used alone or in combination with topical microbicides, may be of significant benefit to HIV prevention.

Modified Vaccinia Virus Ankara Vector Induces Specific Cellular and Humoral Responses in the Female Reproductive Tract, the Main HIV Portal of Entry

The female reproductive tract (FRT) is one of the major mucosal invasion sites for HIV-1. This site has been neglected in previous HIV-1 vaccine studies. Immune responses in the FRT after systemic vaccination remain to be characterized. Using a modified vaccinia virus Ankara (MVA) as a vaccine model, we characterized specific immune responses in all compartments of the FRT of nonhuman primates after systemic vaccination. Memory T cells were preferentially found in the lower tract (vagina and cervix), whereas APCs and innate lymphoid cells were mainly located in the upper tract (uterus and fallopian tubes). This compartmentalization of immune cells in the FRT was supported by transcriptomic analyses and a correlation network. Polyfunctional MVA-specific CD8⁺ T cells were detected in the blood, lymph nodes, vagina, cervix, uterus, and fallopian tubes. Anti-MVA IgG and IgA were detected in cervicovaginal fluid after a second vaccine dose. Thus, systemic vaccination with an MVA vector elicits cellular and Ab responses in the FRT.

Mucosal dendritic cells in HIV-1 susceptibility: a critical role for C-type lectin receptors

Sexual transmission is the major route of HIV-1 infection worldwide. The interaction of HIV-1 with mucosal dendritic cells (DCs) might determine HIV-1 susceptibility as well as initial antiviral immunity controlling virus in the chronic phase. Different DC subsets reside in mucosal tissues and express specific C-type lectin receptors (CLRs) that interact with HIV-1 with different outcomes. HIV-1 has been shown to subvert CLRs for viral transmission and immune evasion, whereas CLRs can also protect against HIV-1 infection. Here, we will discuss the role of CLRs in HIV-1 transmission and adaptive immunity, and how the CLRs dictate the function of DCs in infection. Ultimately, understanding the interplay between CLRs and HIV-1 will lead to targeted approaches in the search for preventative measures.

The rectal mucosa and condomless receptive anal intercourse in HIV-negative MSM: implications for HIV transmission and prevention

Most HIV transmissions among men who have sex with men (MSM), the group that accounted for 67% of new US infections in 2014, occur via exposure to the rectal mucosa. However, it is unclear how the act of condomless receptive anal intercourse (CRAI) may alter the mucosal immune environment in HIV-negative MSM. Here, we performed a comprehensive characterization of the rectal mucosal immune environment for the phenotype and production of pro-inflammatory cytokines by CD4 and CD8 T cells, global transcriptomic analyses, and the composition of microbiota in HIV-negative MSM. Our results show that compared with men who had never engaged in anal intercourse, the rectal mucosa of MSM engaging in CRAI has a distinct phenotype characterized by higher levels of Th17 cells, greater CD8+ T cell proliferation and production of pro-inflammatory cytokines, molecular signatures associated with mucosal injury and repair likely mediated by innate immune cells, and a microbiota enriched for the Prevotellaceae family. These data provide a high-resolution model of the immunological, molecular, and microbiological perturbations induced by CRAI, will have direct utility in understanding rectal HIV transmission among MSM, and will enhance the design of future biomedical prevention interventions, including candidate HIV vaccines.

Vaccine-induced immune responses against both Gag and Env improve control of simian immunodeficiency virus replication in rectally challenged rhesus macaques

The ability to control lentivirus replication may be determined, in part, by the extent to which individual viral proteins are targeted by the immune system. Consequently, defining the antigens that elicit the most protective immune responses may facilitate the design of effective HIV-1 vaccines. Here we vaccinated four groups of rhesus macaques with a heterologous vector prime/boost/boost/boost (PBBB) regimen expressing the following simian immunodeficiency virus (SIV) genes: env, gag, vif, rev, tat, and nef (Group 1); env, vif, rev, tat, and nef (Group 2); gag, vif, rev, tat, and nef (Group 3); or vif, rev, tat, and nef (Group 4). Following repeated intrarectal challenges with a marginal dose of the neutralization-resistant SIVmac239 clone, vaccinees in Groups 1-3 became infected at similar rates compared to control animals. Unexpectedly, vaccinees in Group 4 became infected at a slower pace than the other animals, although this difference was not statistically significant. Group 1 exhibited the best post-acquisition virologic control of SIV infection, with significant reductions in both peak and chronic phase viremia. Indeed, 5/8 Group 1 vaccinees had viral loads of less than 2,000 vRNA copies/mL of plasma in the chronic phase. Vaccine regimens that did not contain gag (Group 2), env (Group 3), or both of these inserts (Group 4) were largely ineffective at decreasing viremia. Thus, vaccine-induced immune responses against both Gag and Env appeared to maximize control of immunodeficiency virus replication. Collectively, these findings are relevant for HIV-1 vaccine design as they provide additional insights into which of the lentiviral proteins might serve as the best vaccine immunogens.

Sex and gender differences in HIV-1 infection

The major burden of the human immunodeficiency (HIV) type 1 pandemic is nowadays carried by women from sub-Saharan Africa. Differences in the manifestations of HIV-1 infection between women and men have been long reported, and might be due to both socio-economic (gender) and biological (sex) factors. Several studies have shown that women are more susceptible to HIV-1 acquisition than men. Following HIV-1 infection, women have lower viral loads during acute infection and exhibit stronger antiviral responses than men, which may contribute to differences in the size of viral reservoirs. Oestrogen receptor signalling could represent an important mediator of sex differences in HIV-1 reservoir size and may represent a potential therapeutic target. Furthermore, immune activation, a hallmark of HIV-1 infection, is generally higher in women than in men and could be a central mechanism in the sex difference observed in the speed of HIV-1 disease progression. Here, we review the literature regarding sex-based differences in HIV-1 infection and discuss how a better understanding of the underlying mechanisms could improve preventive and therapeutic strategies.

Virion-Associated Vpr Alleviates a Postintegration Block to HIV-1 Infection of Dendritic Cells

Viral protein R (Vpr) is an HIV-1 accessory protein whose function remains poorly understood. In this report, we sought to determine the requirement of Vpr for facilitating HIV-1 infection of monocyte-derived dendritic cells (MDDCs), one of the first cell types to encounter virus in the peripheral mucosal tissues. In this report, we characterize a significant restriction of Vpr-deficient virus replication and spread in MDDCs alone and in cell-to-cell spread in MDDC-CD4⁺ T cell cocultures. This restriction of HIV-1 replication in MDDCs was observed in a single round of virus replication and was rescued by the expression of Vpr in trans in the incoming virion. Interestingly, infections of MDDCs with viruses that encode Vpr mutants unable to interact with either the DCAF1/DDB1 E3 ubiquitin ligase complex or a host factor hypothesized to be targeted for degradation by Vpr also displayed a significant replication defect. While the extent of proviral integration in HIV-1-infected MDDCs was unaffected by the absence of Vpr, the transcriptional activity of the viral long terminal repeat (LTR) from Vpr-deficient proviruses was significantly reduced. Together, these results characterize a novel postintegration restriction of HIV-1 replication in MDDCs and show that the interaction of Vpr with the DCAF1/DDB1 E3 ubiquitin ligase complex and the yet-to-be-identified host factor might alleviate this restriction by inducing transcription from the viral LTR. Taken together, these findings identify a robust in vitro cell culture system that is amenable to addressing mechanisms underlying Vpr-mediated enhancement of HIV-1 replication.IMPORTANCE Despite decades of work, the function of the HIV-1 protein Vpr remains poorly understood, primarily due to the lack of an in vitro cell culture system that demonstrates a deficit in replication upon infection with viruses in the absence of Vpr. In this report, we describe a novel cell infection system that utilizes primary human dendritic cells, which display a robust decrease in viral replication upon infection with Vpr-deficient HIV-1. We show that this replication difference occurs in a single round of infection and is due to decreased transcriptional output from the integrated viral genome. Viral transcription could be rescued by virion-associated Vpr. Using mutational analysis, we show that domains of Vpr involved in binding to the DCAF1/DDB1/E3 ubiquitin ligase complex and prevention of cell cycle progression into mitosis are required for LTR-mediated viral expression, suggesting that the evolutionarily conserved G₂ cell cycle arrest function of Vpr is essential for HIV-1 replication.

Seminal plasma induces inflammation and enhances HIV-1 replication in human cervical tissue explants

The most immediate and evident effect of mucosal exposure to semen in vivo is a local release of proinflammatory mediators accompanied by an influx of leukocytes into the female genital mucosa (FGM). The implication of such response in HIV-1 transmission has never been addressed due to limitations of currently available experimental models. Using human tissue explants from the uterine cervix, we developed a system of mucosal exposure to seminal plasma (SP) that supports HIV-1 replication. Treatment of ectocervical explants with SP resulted in the upregulation of inflammatory and growth factors, including IL-6, TNF, CCL5, CCL20, CXCL1, and CXCL8, and IL1A, CSF2, IL7, PTGS2, as evaluated by measuring protein levels in explant conditioned medium (ECM) and gene expression in tissue. SP treatment was also associated with increased recruitment of monocytes and neutrophils, as observed upon incubation of peripheral blood leukocytes with ECM in a transwell system. To evaluate the impact of the SP-mediated response on local susceptibility to HIV-1, we infected ectocervical explants with the CCR5-tropic variant HIV-1BaL either in the presence of SP, or after explant pre-incubation with SP. In both experimental settings SP enhanced virus replication as evaluated by HIV-1 p24gag released in explant culture medium over time, as well as by HIV-1 DNA quantification in explants infected in the presence of SP. These results suggest that a sustained inflammatory response elicited by SP soon after coitus may promote HIV-1 transmission to the FGM. Nevertheless, ectocervical tissue explants did not support the replication of transmitted/founder HIV-1 molecular clones, regardless of SP treatment. Our system offers experimental and analytical advantages over traditional models of HIV-1 transmission for the study of SP immunoregulatory effect on the FGM, and may provide a useful platform to ultimately identify new determinants of HIV-1 infection at this site.

Targeting Glycans of HIV Envelope Glycoproteins for Vaccine Design

The surface of the envelope spike of the human immunodeficiency virus (HIV) is covered with a dense array of glycans, which is sufficient to impede the host antibody response while maintaining a window for receptor recognition. The glycan density significantly exceeds that typically observed on self glycoproteins and is sufficiently high to disrupt the maturation process of glycans, from oligomannose- to complex-type glycosylation, that normally occurs during glycoprotein transit through the secretory system. It is notable that this generates a degree of homogeneity not seen in the highly mutated protein moiety. The conserved, close glycan packing and divergences from default glycan processing give a window for immune recognition. Encouragingly, in a subset of individuals, broadly neutralizing antibodies (bNAbs) have been isolated that recognize these features and are protective in passive-transfer models. Here, we review the recent advances in our understanding of the glycan shield of HIV and outline the strategies that are being pursued to elicit glycan-binding bNAbs by vaccination.

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.

Semen Bacterial Concentrations and HIV-1 RNA Shedding Among HIV-1-Seropositive Kenyan Men

INTRODUCTION

HIV-1 is transmitted through semen from men to their sexual partners. Genital infections can increase HIV-1 RNA shedding in semen, but shedding also occurs in the absence of typical pathogens. We hypothesized that higher bacterial concentrations in semen would be associated with higher HIV-1 RNA levels.

METHODS

We analyzed semen samples from 42 HIV-1-seropositive Kenyan men using quantitative polymerase chain reaction (PCR) to assess bacterial concentrations and real-time PCR to measure HIV-1 RNA levels. Generalized estimation equations were used to evaluate associations between these 2 measures. Broad-range 16S rRNA gene PCR with pyrosequencing was performed on a subset of 13 samples to assess bacterial community composition.

RESULTS

Bacteria were detected in 96.6% of 88 samples by quantitative PCR. Semen bacterial concentration and HIV-1 RNA levels were correlated 0.30 (P = 0.01). The association between bacterial concentration and HIV-1 RNA detection was not significant after adjustment for antiretroviral therapy (ART) (adjusted odds ratio: 1.27, 95% CI: 0.84 to 1.91). Factors associated with semen bacterial concentration included insertive anal sex (adjusted beta 0.92, 95% CI: 0.12 to 1.73) and ART use (adjusted beta: -0.77, 95% CI: -1.50 to 0.04). Among 13 samples with pyrosequencing data, Corynebacterium spp., Staphylococcus spp., and Streptococcus spp. were most frequently detected.

CONCLUSION

Most of these HIV-1-infected men had bacteria in their semen. ART use was associated with undetectable semen HIV-1 RNA and lower semen bacterial concentrations, whereas insertive anal sex was associated with higher bacterial concentrations. Additional studies evaluating the relationship between semen bacteria, inflammation, mucosal immunity, and HIV-1 shedding are needed to understand implications for HIV-1 transmission.

Nanomedicines for dysfunctional macrophage-associated diseases

Macrophages play vital functions in host inflammatory reaction, tissue repair, homeostasis and immunity. Dysfunctional macrophages have significant pathophysiological impacts on diseases such as cancer, inflammatory diseases (rheumatoid arthritis and inflammatory bowel disease), metabolic diseases (atherosclerosis, diabetes and obesity) and major infections like human immunodeficiency virus infection. In view of this common etiology in these diseases, targeting the recruitment, activation and regulation of dysfunctional macrophages represents a promising therapeutic strategy. With the advancement of nanotechnology, development of nanomedicines to efficiently target dysfunctional macrophages can strengthen the effectiveness of therapeutics and improve clinical outcomes. This review discusses the specific roles of dysfunctional macrophages in various diseases and summarizes the latest advances in nanomedicine-based therapeutics and theranostics for treating diseases associated with dysfunctional macrophages.

Resistance to type 1 interferons is a major determinant of HIV-1 transmission fitness

Sexual transmission of HIV-1 is an inefficient process, with only one or few variants of the donor quasispecies establishing the new infection. A critical, and as yet unresolved, question is whether the mucosal bottleneck selects for viruses with increased transmission fitness. Here, we characterized 300 limiting dilution-derived virus isolates from the plasma, and in some instances genital secretions, of eight HIV-1 donor and recipient pairs. Although there were no differences in the amount of virion-associated envelope glycoprotein, recipient isolates were on average threefold more infectious (P = 0.0001), replicated to 1.4-fold higher titers (P = 0.004), were released from infected cells 4.2-fold more efficiently (P < 0.00001), and were significantly more resistant to type I IFNs than the corresponding donor isolates. Remarkably, transmitted viruses exhibited 7.8-fold higher IFNα2 (P < 0.00001) and 39-fold higher IFNβ (P < 0.00001) half-maximal inhibitory concentrations (IC50) than did donor isolates, and their odds of replicating in CD4+ T cells at the highest IFNα2 and IFNβ doses were 35-fold (P < 0.00001) and 250-fold (P < 0.00001) greater, respectively. Interestingly, pretreatment of CD4+ T cells with IFNβ, but not IFNα2, selected donor plasma isolates that exhibited a transmitted virus-like phenotype, and such viruses were also detected in the donor genital tract. These data indicate that transmitted viruses are phenotypically distinct, and that increased IFN resistance represents their most distinguishing property. Thus, the mucosal bottleneck selects for viruses that are able to replicate and spread efficiently in the face of a potent innate immune response.

Visualization of X4- and R5-Tropic HIV-1 Viruses Expressing Fluorescent Proteins in Human Endometrial Cells: Application to Tropism Study

Worldwide most HIV infections occur through heterosexual transmission, involving complex interactions of cell-free and cell-associated particles with cells of the female genital tract mucosa. The ability of HIV-1 to “infect” epithelial cells remains poorly understood. To address this question, replicative-competent chimeric constructs expressing fluorescent proteins and harboring the envelope of X4- or R5-tropic HIV-1 strains were used to “infect” endometrial HEC1-A cells. The virus-cell interactions were visualized using confocal microscopy (CM) at various times post infection. Combined with quantification of viral RNA and total HIV DNA in infected cells, the CM pictures suggest that epithelial cells do not support a complete viral replication cycle: X4-tropic viruses are imported into the nucleus in a non-productive way, whereas R5-tropic viruses transit through the cytoplasm without replication and are preferentially transmitted to susceptible activated peripheral blood mononuclear cells. Within the limit of experiments conducted in vitro on a continued cell line, these results indicate that the epithelial mucosa may participate to the selection of HIV-1 strains at the mucosal level.

Virus-Host Gene Interactions Define HIV-1 Disease Progression

In this chapter, we will review recent research on the virology of HIV-1 transmission and the impact of the transmitted virus genotype on subsequent disease progression. In most instances of HIV-1 sexual transmission, a single genetic variant, or a very limited number of variants from the diverse viral quasi-species present in the transmitting partner establishes systemic infection. Transmission involves both stochastic and selective processes, such that in general a minority variant in the donor is transmitted. While there is clear evidence for selection, the biological properties that mediate transmission remain incompletely defined. Nevertheless, the genotype of the transmitted founder virus, which reflects prior exposure to and escape from host immune responses, clearly influences disease progression. Some escape mutations impact replicative capacity, while others effectively cloak the virus from the newly infected host's immune response by preventing recognition. It is the balance between the impact of escape mutations on viral fitness and susceptibility to the host immunogenetics that defines HIV-1 disease progression.

Neutralization Takes Precedence Over IgG or IgA Isotype-related Functions in Mucosal HIV-1 Antibody-mediated Protection

HIV-1 infection occurs primarily through mucosal transmission. Application of biologically relevant mucosal models can advance understanding of the functional properties of antibodies that mediate HIV protection, thereby guiding antibody-based vaccine development. Here, we employed a human ex vivo vaginal HIV-1 infection model and a rhesus macaque in vivo intrarectal SHIV challenge model to probe the protective capacity of monoclonal broadly-neutralizing (bnAb) and non-neutralizing Abs (nnAbs) that were functionally modified by isotype switching. For human vaginal explants, we developed a replication-competent, secreted NanoLuc reporter virus system and showed that CD4 binding site bnAbs b12 IgG1 and CH31 IgG1 and IgA2 isoforms potently blocked HIV-1JR-CSF and HIV-1Bal26 infection. However, IgG1 and IgA nnAbs, either alone or together, did not inhibit infection despite the presence of FcR-expressing effector cells in the tissue. In macaques, the CH31 IgG1 and IgA2 isoforms infused before high-dose SHIV challenge were completely to partially protective, respectively, while nnAbs (CH54 IgG1 and CH38 mIgA2) were non-protective. Importantly, in both mucosal models IgG1 isotype bnAbs were more protective than the IgA2 isotypes, attributable in part to greater neutralization activity of the IgG1 variants. These findings underscore the importance of potent bnAb induction as a primary goal of HIV-1 vaccine development.

Chemokine Levels in the Penile Coronal Sulcus Correlate with HIV-1 Acquisition and Are Reduced by Male Circumcision in Rakai, Uganda

Individual susceptibility to HIV is heterogeneous, but the biological mechanisms explaining differences are incompletely understood. We hypothesized that penile inflammation may increase HIV susceptibility in men by recruiting permissive CD4 T cells, and that male circumcision may decrease HIV susceptibility in part by reducing genital inflammation. We used multi-array technology to measure levels of seven cytokines in coronal sulcus (penile) swabs collected longitudinally from initially uncircumcised men enrolled in a randomized trial of circumcision in Rakai, Uganda. Coronal sulcus cytokine levels were compared between men who acquired HIV and controls who remained seronegative. Cytokines were also compared within men before and after circumcision, and correlated with CD4 T cells subsets in foreskin tissue. HIV acquisition was associated with detectable coronal sulcus Interleukin-8 (IL-8 aOR 2.26, 95%CI 1.04–6.40) and Monokine Induced by γ-interferon (MIG aOR 2.72, 95%CI 1.15–8.06) at the visit prior to seroconversion, and the odds of seroconversion increased with detection of multiple cytokines. Coronal sulcus chemokine levels were not correlated with those in the vagina of a man’s female sex partner. The detection of IL-8 in swabs was significantly reduced 6 months after circumcision (PRR 0.59, 95%CI 0.44–0.87), and continued to decline for at least two years (PRR 0.29, 95%CI 0.16–0.54). Finally, prepuce IL-8 correlated with increased HIV target cell density in foreskin tissues, including highly susceptible CD4 T cells subsets, as well as with tissue neutrophil density. Together, these data suggest that penile inflammation increases HIV susceptibility and is reduced by circumcision.

The per-contact risk of infection with HIV through sexual exposure is low and highly variable. Understanding the biological basis for this variability could help in the development of new methods to prevent infection. There is some evidence that penile inflammation, even in the absence of any clinical symptoms, may increase HIV-susceptibility by recruiting CD4 T cells, the immune cell type that is the principal target of HIV. We analyzed soluble inflammatory mediators in prepuce swabs collected longitudinally from initially HIV-negative men enrolled in a randomized controlled trial of adult circumcision. We found that these inflammatory mediators were elevated in men who went on to acquire HIV. We also found that higher levels of these mediators were associated with an increased density of HIV-susceptible target cells in the underlying foreskin tissue and that circumcision reduced their levels, which may help to explain why circumcision reduces HIV risk by 60% or more. Together, these data suggest that penile inflammation, in the absence of genital infections, increases HIV susceptibility and is reduced by adult male circumcision.

The interaction between human papillomavirus and other viruses

The etiological role of human papillomavirus (HPV) in anogenital tract and head and neck cancers is well established. However, only a low percentage of HPV-positive women develop cancer, indicating that HPV is necessary but not sufficient in carcinogenesis. Several biological and environmental cofactors have been implicated in the development of HPV-associated carcinoma that include immune status, hormonal changes, parity, dietary habits, tobacco usage, and co-infection with other sexually transmissible agents. Such cofactors likely contribute to HPV persistent infection through diverse mechanisms related to immune control, efficiency of HPV infection, and influences on tumor initiation and progression. Conversely, HPV co-infection with other factors may also harbor anti-tumor effects. Here, we review epidemiological and experimental studies investigating human immunodeficiency virus (HIV), herpes simplex virus (HSV) 1 and 2, human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), BK virus (BKV), JC virus (JCV), and adeno-associated virus (AAV) as viral cofactors in or therapeutic factors against the development of genital and oral HPV-associated carcinomas.

Enhanced binding of antibodies generated during chronic HIV infection to mucus component MUC16

Transmission of HIV across mucosal barriers accounts for the majority of HIV infections worldwide. Thus, efforts aimed at enhancing protective immunity at these sites are a top priority, including increasing virus-specific antibodies (Abs) and antiviral activity at mucosal sites. Mucin proteins, including the largest cell-associated mucin, mucin 16 (MUC16), help form mucus to provide a physical barrier to incoming pathogens. Here, we describe a natural interaction between Abs and MUC16 that is enhanced in specific disease settings such as chronic HIV infection. Binding to MUC16 was independent of IgG subclass, but strongly associated with shorter Ab glycan profiles, with agalactosylated (G0) Abs demonstrating the highest binding to MUC16. Binding of Abs to epithelial cells was diminished following MUC16 knockdown, and the MUC16 N-linked glycans were critical for binding. Further, agalactosylated VRC01 captured HIV more efficiently in MUC16. These data point to a novel opportunity to enrich Abs at mucosal sites by targeting Abs to MUC16 through changes in Fc glycosylation, potentially blocking viral movement and sequestering the virus far from the epithelial border. Thus, next-generation vaccines or monoclonal therapeutics may enhance protective immunity by tuning Ab glycosylation to promote the enrichment of Abs at mucosal barriers.

Monocytes but Not Lymphocytes Carrying HIV-1 on Their Surface Transmit Infection to Human Tissue Ex Vivo

Unprotected sexual intercourse with HIV-infected men is the major cause of new infections. HIV virions are released into semen by various cells of the male genital tract, as well as by infected monocytes and lymphocytes present in semen. Some of these virions may attach to the surfaces of cells, infected or uninfected. We investigated whether cells carrying attached HIV on their surfaces can transmit infection. We addressed this question in a model system of human tissue exposed ex vivo to monocytes and lymphocytes carrying HIV on their surfaces. We gamma irradiated the cells to prevent their productive infection. In spite of comparable amounts of HIV attached to monocytes and lymphocytes, only monocytes were capable of transmitting infection and triggering productive infection in tissue. This HIV-1 transmission was mediated by cell-cell contacts. Our experiments suggest that in vivo, HIV attached to infected or uninfected monocytes, which far outnumber lymphocytes in HIV-infected semen, may contribute to sexual transmission of HIV from men to their partners.

IMPORTANCE

The vast majority of new HIV infections occur through sexual transmission, in which HIV is transferred from the semen of an infected male to an uninfected partner. In semen, HIV-1 particles may exist as free-floating virions; inside infected cells; or attached to the surfaces of cells, whether they are infected or not. Here, we investigated whether HIV attached to the surfaces of monocytes or lymphocytes could transmit infection to human tissue. Incubation of human tissue with monocyte-attached HIV resulted in productive tissue infection. In contrast, there was no infection of tissues when they were incubated with lymphocyte-attached HIV-1. Our results highlight the important role that seminal monocytes may play in HIV transmission in vivo, especially since monocytes far outnumber lymphocytes in the semen of HIV-infected individuals.

PolyICLC Exerts Pro- and Anti-HIV Effects on the DC-T Cell Milieu In Vitro and In Vivo

Myeloid dendritic cells (mDCs) contribute to both HIV pathogenesis and elicitation of antiviral immunity. Understanding how mDC responses to stimuli shape HIV infection outcomes will inform HIV prevention and treatment strategies. The long double-stranded RNA (dsRNA) viral mimic, polyinosinic polycytidylic acid (polyIC, PIC) potently stimulates DCs to focus Th1 responses, triggers direct antiviral activity in vitro, and boosts anti-HIV responses in vivo. Stabilized polyICLC (PICLC) is being developed for vaccine adjuvant applications in humans, making it critical to understand how mDC sensing of PICLC influences HIV infection. Using the monocyte-derived DC (moDC) model, we sought to describe how PICLC (vs. other dsRNAs) impacts HIV infection within DCs and DC-T cell mixtures. We extended this work to in vivo macaque rectal transmission studies by administering PICLC with or before rectal SIVmac239 (SIVwt) or SIVmac239ΔNef (SIVΔNef) challenge. Like PIC, PICLC activated DCs and T cells, increased expression of α4β7 and CD169, and induced type I IFN responses in vitro. The type of dsRNA and timing of dsRNA exposure differentially impacted in vitro DC-driven HIV infection. Rectal PICLC treatment similarly induced DC and T cell activation and pro- and anti-HIV factors locally and systemically. Importantly, this did not enhance SIV transmission in vivo. Instead, SIV acquisition was marginally reduced after a single high dose challenge. Interestingly, in the PICLC-treated, SIVΔNef-infected animals, SIVΔNef viremia was higher, in line with the importance of DC and T cell activation in SIVΔNef replication. In the right combination anti-HIV strategy, PICLC has the potential to limit HIV infection and boost HIV immunity.