Elevated elafin/trappin-2 in the female genital tract is associated with protection against HIV acquisition

Natural Resistance to HIV Infection: Role of Immune Activation

INTRODUCTION

Although repeated exposure to HIV-1 can result in infection, some individuals remain seronegative without clinical or serologic evidence of infection; these individuals are known as HIV-1-exposed seronegative individuals. This population has been extensively studied to understand the mechanisms associated with natural resistance to HIV infection. Two main hypotheses have been proposed to explain this resistance: some researchers associated resistance with a low activation phenotype characterized by a decrease in the activation and proliferation of immune system cells linked with infection control and decreased production of cytokines and pro-inflammatory molecules, whereas others suggest that resistance is related to immune system activation and the expression of high levels of chemokines, pro-inflammatory cytokines and antiviral molecules.

AIMS

Our study aims to review and analyze the most relevant evidence supporting the role of the activation level of the immune system during natural resistance to HIV-1 infection.

METHODS

A search was conducted via the PubMed, SciELO and ScienceDirect databases. The literature search was performed in a nonsystematic manner. Articles published in the last five decades addressing immune activation mechanisms in natural resistance to HIV were reviewed.

RESULTS

A low-activation phenotype, characterized by a high frequency of Treg cells; reduced expression of CD25, CD38, and HLA-DR; and lower production of pro-inflammatory cytokines in peripheral and mucosal tissues, plays a key role in reducing the number of activated cells susceptible to infection, but it minimizes chronic inflammation, facilitating viral entry and spread. In contrast, the activation phenotype is associated with high expression of markers such as CD25, CD38, and HLA-DR, along with elevated high levels of interferon-stimulated genes and pro-inflammatory cytokines. This profile could promote infection control while increasing the number of virus-susceptible cells.

CONCLUSION

The complexity of the immune response during HIV exposure, reflected in the conflicting evidence concerning whether low or high immune activation offers protection against infection, suggests that there may be multiple pathways to HIV-1 resistance, influenced by factors such as the type of viral exposure, the immune environment, and individual genetics. Further research is needed to determine which immune states are protective and how these responses can be modulated to prevent infection.

Versatile whey acidic protein four-disulfide core domain proteins: biology and role in diseases

The Whey acidic protein four-disulfide core (WFDC) protein family consists of proteins with one or more WFDC domains which are ubiquitously expressed throughout the body of human and perform a wide range of functions, including antiprotease, antibacterial, and immunomodulatory functions. Aberrant expression of WFDC proteins is associated with human diseases. However, review on the WFDC protein family is limited and insufficient. Furthermore, a systematic summary of the underlying mechanisms of WFDC protein activity is lacking. In this review, we give a summary of the structural basis and molecular function of these proteins and review the immune regulatory mechanisms and signaling pathways of WFDC proteins in the development of certain diseases. Furthermore, we discuss the diagnostic and prognostic potential of multiple WFDC proteins in the aforementioned conditions, as well as their prospective use. At last, we also discuss the progress of WFDC protein in clinical trials and put forward some research difficulties and the directions of follow-up research. Our review highlights the functional diversity and clinical significance of WFDC proteins family, while providing potential targets for drug development and innovative therapeutic strategies, this review lays the foundation and direction for future research on WFDC proteins.

The initial interplay between HIV and mucosal innate immunity

Human Immunodeficiency Virus (HIV) is still one of the major global health issues, and despite significant efforts that have been put into studying the pathogenesis of HIV infection, several aspects need to be clarified, including how innate immunity acts in different anatomical compartments. Given the nature of HIV as a sexually transmitted disease, one of the aspects that demands particular attention is the mucosal innate immune response. Given this scenario, we focused our attention on the interplay between HIV and mucosal innate response: the different mucosae act as a physical barrier, whose integrity can be compromised by the infection, and the virus-cell interaction induces the innate immune response. In addition, we explored the role of the mucosal microbiota in facilitating or preventing HIV infection and highlighted how its changes could influence the development of several opportunistic infections. Although recent progress, a proper characterization of mucosal innate immune response and microbiota is still missing, and further studies are needed to understand how they can be helpful for the formulation of an effective vaccine.

Natural Immunity against HIV-1: Progression of Understanding after Association Studies

Natural immunity against HIV has been observed in many individuals in the world. Among them, a group of female sex workers enrolled in the Pumwani sex worker cohort remained HIV uninfected for more than 30 years despite high-risk sex work. Many studies have been carried out to understand this natural immunity to HIV in the hope to develop effective vaccines and preventions. This review focuses on two such examples. These studies started from identifying immunogenetic or genetic associations with resistance to HIV acquisition, and followed up with an in-depth investigation to understand the biological relevance of the correlations of protection, and to develop and test novel vaccines and preventions.

The Potential Role of FREM1 and Its Isoform TILRR in HIV-1 Acquisition through Mediating Inflammation

FREM1 (Fras-related extracellular matrix 1) and its splice variant TILRR (Toll-like interleukin-1 receptor regulator) have been identified as integral components of innate immune systems. The potential involvement of FREM1 in HIV-1 (human immunodeficiency virus 1) acquisition was suggested by a genome-wide SNP (single nucleotide polymorphism) analysis of HIV-1 resistant and susceptible sex workers enrolled in the Pumwani sex worker cohort (PSWC) in Nairobi, Kenya. The studies showed that the minor allele of a FREM1 SNP rs1552896 is highly enriched in the HIV-1 resistant female sex workers. Subsequent studies showed that FREM1 mRNA is highly expressed in tissues relevant to mucosal HIV-1 infection, including cervical epithelial tissues, and TILRR is a major modulator of many genes in the NF-κB signal transduction pathway. In this article, we review the role of FREM1 and TILRR in modulating inflammatory responses and inflammation, and how their influence on inflammatory responses of cervicovaginal tissue could enhance the risk of vaginal HIV-1 acquisition.

Microbial mismanagement: how inadequate treatments for vaginal dysbiosis drive the HIV epidemic in women

Women and girls represent a key population driving new HIV infections and persistence of the HIV pandemic. A key determinant of HIV susceptibility is the composition of the vaginal microbiome, which can influence the local immune cell population, inflammation status, and HIV prevention drug levels. While a low-diversity composition dominated by Lactobacillus crispatus is associated with a decreased risk of HIV acquisition, high diversity environments associated with bacterial vaginosis increase risk of HIV. Given the important role of the vaginal microbiome in determining HIV susceptibility, altering the microbiome towards a Lactobacillus-dominated state is an attractive complementary strategy to reduce HIV incidence rates. Here, we provide an overview of the mechanisms by which the vaginal microbiome may contribute to HIV acquisition risk. Furthermore, we address the advantages and limitations of historical treatments and emerging technologies under investigation to modify the vaginal microbiome, including: antibiotics, bacteriophages, probiotics, topicals, and engineered bacteria. By addressing the current state of vaginal microbiome knowledge and strategies for manipulation, we hope to amplify the growing calls for increased resources and research into vaginal microbial health, which will be essential to accelerating preventative efforts amongst the world's most vulnerable populations.

Transglutaminase 2 as a Marker for Inflammation and Therapeutic Target in Sepsis

Sepsis results in lethal organ malfunction due to dysregulated host response to infection, which is a condition with increasing prevalence worldwide. Transglutaminase 2 (TG2) is a crosslinking enzyme that forms a covalent bond between lysine and glutamine. TG2 plays important roles in diverse cellular processes, including extracellular matrix stabilization, cytoskeletal function, cell motility, adhesion, signal transduction, apoptosis, and cell survival. We have shown that the co-culture of Candida albicans and hepatocytes activates and induces the translocation of TG2 into the nucleus. In addition, the expression and activation of TG2 in liver macrophages was dramatically induced in the lipopolysaccharide-injected and cecal ligation puncture-operated mouse models of sepsis. Based on these findings and recently published research, we have reviewed the current understanding of the relationship between TG2 and sepsis. Following the genetic and pharmacological inhibition of TG2, we also assessed the evidence regarding the use of TG2 as a potential marker and therapeutic target in inflammation and sepsis.

Inflammation, HIV, and Immune Quiescence: Leveraging on Immunomodulatory Products to Reduce HIV Susceptibility

The relationship between inflammation and HIV has been a focus of research over the last decade. In HIV-infected individuals, increased HIV-associated immune activation significantly correlated to disease progression. While genital inflammation (GI) has been shown to significantly increase the risk of HIV acquisition and transmission, immune correlates for reduced risk remain limited. In certain HIV-exposed seronegative individuals, an immune quiescent phenotype characterized reduced risk. Immune quiescence is defined by specific, targeted, highly regulated immune responses that hinder overt inflammation or immune activation. Targeted management of inflammation, therefore, is a plausible strategy to mitigate HIV risk and slow disease progression. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as hydroxychloroquine and aspirin have shown encouraging preliminary results in low-risk women by reducing systemic and genital immune activation. A topical NSAID, containing ibuprofen, is effective in treating vulvovaginal inflammation. Additionally, the glucocorticoids (GCs), prednisolone, and dexamethasone are used to treat HIV-associated immune activation. Collectively, these data inform on immune-modulating drugs to reduce HIV risk. However, the prolonged use of these pharmaceutical drugs is associated with adverse effects, both systemically and to a lesser extent topically. Natural products with their reduced side effects coupled with anti-inflammatory properties render them viable options. Lactic acid (LA) has immunomodulatory properties. LA regulates the genital microbiome by facilitating the growth of Lactobacillus species, while simultaneously limiting bacterial species that cause microbial dysbiosis and GI. Glycerol monolaurate, besides being anti-inflammatory, also inhibited SIV infections in rhesus macaques. The proposed pharmaceutical and natural products could be used in combination with either antiretrovirals for treatment or preexposure prophylaxis for HIV prevention. This review provides a summary on the associations between inflammation, HIV risk, and disease progression. Furthermore, we use the knowledge from immune quiescence to exploit the use of pharmaceutical and natural products as strategic interventions to manage inflammation, toward mitigating HIV infections.

Matrix Metalloproteinases Expressed in Response to Bacterial Vaginosis Disrupt the Endocervical Epithelium, Increasing Transmigration of HIV

Bacterial vaginosis (BV), a disorder of the female reproductive tract (FRT) in which a healthy Lactobacillus-dominant microflora is replaced by BV-associated bacteria (BVAB), can significantly increase the incidence of human immunodeficiency virus (HIV) acquisition. Discerning the effect of BV on the mucosal epithelium of the FRT may yield novel preventatives and therapeutics for HIV infection. Here, we investigated barrier dysfunction of the endocervix by host-derived factors, secreted in response to BV, as a potential cause of HIV infection. Using a polarized endocervical cell culture system, we determined that conditioned media (CM) from endocervical cells cocultured with BVAB (endocervical+BVAB CM), as well as cervicovaginal fluid (CVF) from women with BV, disrupted epithelial polarization. We assessed host matrix metalloproteinases (MMPs) as the BV-associated secreted factors which disrupt the endocervical epithelium. MMPs were overexpressed in endocervical+BVAB CM and CVF from women with BV and were capable of disrupting endocervical epithelial polarization. When we cocultured polarized endocervical cells with HIV-1-infected lymphocyte-derived cells, we discovered endocervical+BVAB CM and MMPs significantly increased the transmigration of virus through the epithelium, and treatment with an MMP inhibitor decreased these effects. When we examined the effect of CVF on HIV-1 transmigration through endocervical epithelium, we demonstrated that CVF samples with greater concentrations of BV-associated MMPs increased viral transmigration. Our results suggest MMPs increase HIV-1 infection by disrupting the endocervical epithelium, permitting transmigration of virus through the epithelium to infect underlying target cells.

Antimicrobial peptides of the vaginal innate immunity and their role in the fight against sexually transmitted diseases

Some antimicrobial peptides (AMPs) are produced in the vaginal innate immune system and play an important role in protecting this organ against pathogenic agents. Moreover, sexually transmitted diseases have become a major problem in human societies and are rapidly spreading. The emergence of antibiotic-resistant microbes (superbugs) can pose a major threat to human societies and cause rapid spread of these diseases. Finding new antimicrobial compounds to fight superbugs is therefore essential. It has been shown that AMPs have good potential to become new antibiotics. The most important AMPs in the vaginal innate immune system are defensins, secretory leucocyte protease inhibitors, calprotectin, lysozyme, lactoferrin and elafin, which play an important role in host defence against sexually transmitted infections, modulation of immune responses and anticancer activities. Some AMPs, such as LL-37, magainin 2 and nisin, show both spermicidal and antimicrobial effects in the vagina. In this summary, we will discuss vaginal AMPs and continue to address some of the challenges of using peptides to control pathogens that are effective in sexually transmitted diseases.

Human Antimicrobial Peptides as Therapeutics for Viral Infections

Successful in vivo infection following pathogen entry requires the evasion and subversion of multiple immunological barriers. Antimicrobial peptides (AMPs) are one of the first immune pathways upregulated during infection by multiple pathogens, in multiple organs in vivo. In humans, there are many classes of AMPs exhibiting broad antimicrobial activities, with defensins and the human cathelicidin LL-37 being the best studied examples. Whereas historically the efficacy and therapeutic potential of AMPs against bacterial infection has been the primary focus of research, recent studies have begun to elucidate the antiviral properties of AMPs as well as their role in regulation of inflammation and chemoattraction. AMPs as therapeutic tools seem especially promising against emerging infectious viral pathogens for which no approved vaccines or treatments are currently available, such as dengue virus (DENV) and Zika virus (ZIKV). In this review, we summarize recent studies elucidating the efficacy and diverse mechanisms of action of various classes of AMPs against multiple viral pathogens, as well as the potential use of human AMPs in novel antiviral therapeutic strategies.

An interferon-like small chemical compound CDM-3008 suppresses hepatitis B virus through induction of interferon-stimulated genes

Oral administration of nucleotide analogues and injection of interferon-α (IFNα) are used to achieve immediate suppression in replication of hepatitis B virus (HBV). Nucleotide analogs and IFNα inhibit viral polymerase activity and cause long-term eradication of the virus at least in part through removing covalently closed circular DNA (cccDNA) via induction of the APOBEC3 deaminases family of molecules, respectively. This study aimed to explore whether the orally administrable low molecular weight agent CDM-3008 (RO8191), which mimics IFNα through the binding to IFNα/β receptor 2 (IFNAR2) and the activation of the JAK/STAT pathway, can suppress HBV replication and reduce cccDNA levels. In primary cultured human hepatocytes, HBV DNA levels were decreased after CDM-3008-treatment in a dose-dependent manner with a half-maximal inhibitory concentration (IC₅₀) value of 0.1 μM, and this was accompanied by significant reductions in cellular cccDNA levels, both HBeAg and HBsAg levels in the cell culture medium. Using a microarray we comprehensively analyzed and compared changes in gene (mRNA) expression in CDM-3008- and IFNα-treated primary cultured human hepatocytes. As reported previously, CDM-3008 mimicked the induction of genes that participate in the interferon signaling pathway. OAS1 and ISG20 mRNA expression was similarly enhanced by both CDM-3008 and IFNα. Thus, CDM-3008 could suppress pgRNA expression to show anti-HBV activity. APOBEC3F and 3G mRNA expression was also induced by CDM-3008 and IFNα treatments, suggesting that cccDNA could be degraded through induced APOBEC3 family proteins. We identified the genes whose expression was specifically enhanced in CDM-3008-treated cells compared to IFNα-treated cells. The expression of SOCS1, SOCS2, SOCS3, and CISH, which inhibit STAT activation, was enhanced in CDM-3008-treated cells suggesting that a feedback inhibition of the JAK/STAT pathway was enhanced in CDM-3008-treated cells compared to IFNα-treated cells. In addition, CDM-3008 showed an additive effect with a clinically-used nucleoside entecavir on inhibition of HBV replication. In summary, CDM-3008 showed anti-HBV activity through activation of the JAK/STAT pathway, inducing the expression of interferon-stimulated genes (ISGs), with greater feedback inhibition than IFNα.

Genetic associations of the vitamin D and antiviral pathways with natural resistance to HIV-1 infection are influenced by interpopulation variability

Vitamin D (VitD) may modulate anti-HIV-1 responses modifying the risk to acquire the HIV-1-infection. We performed a nested case-control exploratory study involving 413 individuals; HIV-1-exposed seropositives (cases) and seronegatives (HESN) (controls) from three cohorts: sexually-exposed from Colombia and Italy and parenterally-exposed from Spain. The association and interactions of 139 variants in 9 VitD pathway genes, and in 14 antiviral genes with resistance/susceptibility (R/S) to HIV-1 infection was evaluated. Associations between variants and mRNA levels were also analyzed in the Colombian samples. Variants and haplotypes in genes of VitD and antiviral pathways were associated with R/S, but specific associations were not reproduced in all cohorts. Allelic heterogeneity could explain such inconsistency since the associations found in all cohorts were consistently in the same genes: VDR and RXRA of the VitD pathway genes and in TLR2 and RNASE4. Remarkably, the multi-locus genotypes (interacting variants) observed in genes of VitD and antiviral pathways were present in most HESNs of all cohorts. Finally, HESNs carrying resistance-associated variants had higher levels of VitD in plasma, of VDR mRNA in blood cells, and of ELAFIN and defensins mRNA in the oral mucosa. In conclusion, despite allelic heterogeneity, most likely due to differences in the genetic history of the populations, the associations were locus dependent suggesting that genes of the VitD pathway might act in concert with antiviral genes modulating the resistance phenotype of the HESNs. Although these associations were significant after permutation test, only haplotype results remained statistically significant after Bonferroni test, requiring further replications in larger cohorts and functional analyzes to validate these conclusions.

Surfactant Protein D Reverses the Gene Signature of Transepithelial HIV-1 Passage and Restricts the Viral Transfer Across the Vaginal Barrier

Effective prophylactic strategy against the current epidemic of sexually transmitted HIV-1 infection requires understanding of the innate gatekeeping mechanisms at the genital mucosa. Surfactant protein D (SP-D), a member of the collectin family of proteins naturally present in the vaginal tract, is a potential HIV-1 entry inhibitor at the cellular level. Human EpiVaginal tissues compartmentalized in culture inserts were apically exposed to HIV-1 and/or a recombinant fragment of human SP-D (rfhSP-D) and viral passage was assessed in the basal chamber containing mononuclear leukocytes. To map the gene signature facilitating or resisting the transepithelial viral transfer, microarray analysis of the HIV-1 challenged EpiVaginal tissues was performed in the absence or presence of rfhSP-D. Mucosal biocompatibility of rfhSP-D was assessed ex vivo and in the standard rabbit vaginal irritation model. The passage of virus through the EpiVaginal tissues toward the underlying target cells was associated with a global epithelial gene signature including differential regulation of genes primarily involved in inflammation, tight junctions and cytoskeletal framework. RfhSP-D significantly inhibited HIV-1 transfer across the vaginal tissues and was associated with a significant reversal of virus induced epithelial gene signature. Pro-inflammatory NF-κB and mTOR transcripts were significantly downregulated, while expression of the tight junctions and cytoskeletal genes was upheld. In the absence of virus, rfhSP-D directly interacted with the EpiVaginal tissues and upregulated expression of genes related to structural stability of the cell and epithelial integrity. There was no increment in the viral acquisition by the PBMCs present in basal chambers wherein, the EpiVaginal tissues in apical chambers were treated with rfhSP-D. The effective concentrations of rfhSP-D had no effect on lactobacilli, epithelial barrier integrity and were safe on repeated applications onto the rabbit vaginal mucosa. This pre-clinical safety data, coupled with its efficacy of restricting viral passage via reversal of virus-induced gene expression of the vaginal barrier, make a strong argument for clinical trials of rfhSP-D as a topical anti-HIV microbicide.

A High-throughput Bead-based Affinity Assay Enables Analysis of Genital Protein Signatures in Women At Risk of HIV Infection

Women at high risk of HIV infection, including sex workers and those with active genital inflammation, have molecular signatures of immune activation and epithelial barrier remodeling in samples of their genital mucosa. These alterations in the local immunological milieu are likely to impact HIV susceptibility. We here analyze host genital protein signatures in HIV uninfected women, with high frequency of condom use, living in HIV-serodiscordant relationships. Cervicovaginal secretions from women living in HIV-serodiscordant relationships (n = 62) were collected at three time points over 12 months. Women living in HIV-negative seroconcordant relationships (controls, n = 25) were sampled at one time point. All study subjects were examined for demographic parameters associated with susceptibility to HIV infection. The cervicovaginal samples were analyzed using a high-throughput bead-based affinity assay. Proteins involved in epithelial barrier function and inflammation were increased in HIV-serodiscordant women. By combining several methods of analysis, a total of five proteins (CAPG, KLK10, SPRR3, elafin/PI3, CSTB) were consistently associated with this study group. Proteins analyzed using the affinity set-up were further validated by label-free tandem mass spectrometry in a partially overlapping cohort with concordant results. Women living in HIV-serodiscordant relationships thus had elevated levels of proteins involved in epithelial barrier function and inflammation despite low prevalence of sexually transmitted infections and a high frequency of safe sex practices. The identified proteins are important markers to follow during assessment of mucosal HIV susceptibility factors and a high-throughput bead-based affinity set-up could be a suitable method for such evaluation.

Impact of chronic sexual abuse and depression on inflammation and wound healing in the female reproductive tract of HIV-uninfected and HIV-infected women

Sexual violence is associated with increased risk of HIV acquisition/transmission in women. Forced sex can result in physical trauma to the reproductive tract as well as severe psychological distress. However, immuno-biological mechanisms linking sexual violence and HIV susceptibility are incompletely understood. Using the Women’s Interagency HIV Study repository, a total of 77 women were selected to form 4 groups, stratified by HIV serostatus, in the following categories: 1) no sexual abuse history and low depressive symptom score (below clinically significant cut-off, scores <16) (Control); 2) no sexual abuse history but high depressive symptom score, ≥16 (Depression); 3) chronic sexual abuse exposure and low depressive symptom score (Abuse); 4) chronic sexual abuse exposure and high depressive symptom score (Abuse+Depression). Inflammation-associated cytokines/chemokines/proteases (TNF-α, IL-6, IL-1α, IL-1β, TGF-β MIP-3α, IP-10, MCP-1, Cathepsin B), anti-inflammatory/anti-HIV mediators (Secretory leukocyte protease inhibitor (SLPI), Elafin, beta defensin 2 (HBD2), alpha defensins (HNP 1–3), Thrombospondin (TSP-1), Serpin A1, A5, Cystatin A, B), and wound-healing mediators (Gro-α, VEGF, PDGF, EGF, FGF, IGF), were measured in cervical-vaginal lavage (CVL) using ELISA. Linear regression was used to model association of biomarkers with depression and abuse as predictor variables; the interaction between depression and abuse was also tested. Anti-HIV activity in CVL was tested using TZM-bl indicator cell line. In HIV-uninfected women, median levels of IL-6 (p = 0.04), IL-1α (p<0.01), TGF-β (p = 0.01), IP-10 (p = <0.01), PDGF (p<0.01) and FGF (p<0.01), differed significantly between groups. Specifically, an association was found between chronic sexual abuse and increased IL-1α (p<0.01), MIP-3α (p = 0.04), IP-10 (p<0.01), Serpin B1 (p = 0.01), FGF (p = 0.04) and decreased TGF-β (p<0.01), MCP-1 (p = 0.02), PDGF (p<0.01). Further, there was evidence of significant interactions between chronic sexual abuse and current depression for IL-1α, IP-10, Serpin A1, Cystatin B, and FGF. In HIV-infected women, median levels of TNF-α (p<0.01), IL-6 (p = 0.05), MIP-3α (p<0.01), and MCP-1 (p = 0.01), differed significantly between groups. Specifically, an association was found between chronic sexual abuse and increased MCP-1 (p = 0.03), Gro-α (p = 0.01) and decreased TNF-α (p<0.01), IL-1α (p = 0.02), MIP-3α (p<0.01) and Cathepsin B (p = 0.03). Current depressive symptoms were associated with significantly decreased MIP-3α (p<0.01). There was evidence of significant interactions between chronic sexual abuse and current depression for MCP-1 and FGF. No significant differences were observed in anti-HIV activity among all eight groups. Heat-map analyses revealed distinct immune network patterns, particularly in the Abuse groups for both HIV-infected and uninfected women. Our data indicates a complex relationship between chronic sexual abuse exposure, depressive symptoms, and FRT immune mediators that are also affected by HIV status. Association of chronic sexual abuse with increase in inflammation-associated cytokine/chemokine expression, along with impaired wound-healing associated growth-factors can create a microenvironment that can facilitate HIV infection. Evaluation of longitudinal changes in exposures and biomarkers are needed to untangle the immuno-biological mechanisms that may put women who endure life-long sexual abuse at increased risk for HIV.

Gender proteomics I. Which proteins in non-sexual organs

Differences related to gender have long been neglected but recent investigations show that they are widespread and may be recognized with all types of omics approaches, both in tissues and in biological fluids. Our review compiles evidence collected with proteomics techniques in our species, mainly focusing on baseline parameters in non-sexual organs in healthy men and women. Data from human specimens had to be replaced with information from other mammals every time invasive procedures of sample procurement were involved.

SIGNIFICANCE

As our knowledge, and the methods to build it, get refined, gender differences need to receive more and more attention, as they influence the outcome of all aspects in lifestyle, including diet, exercise and environmental factors. In turn this background modulates a differential susceptibility to some disease, or a different pathogenetic mechanism, depending on gender, and a different response to pharmacological therapy. Preparing this review we meant to raise awareness about the gender issue. We anticipate that more and more often, in the future, separate evaluations will be carried out on male and female subjects as an alternative - and an upgrade - to the current approach of reference and test groups being 'matched for age and sex'.

Highly Human Immunodeficiency Virus-Exposed Seronegative Men Have Lower Mucosal Innate Immune Reactivity

Risk of HIV acquisition varies, and some individuals are highly HIV-1-exposed, yet, persistently seronegative (HESN). The immunologic mechanisms contributing to this phenomenon are an area of intense interest. As immune activation and inflammation facilitate disease progression in HIV-1-infected persons and gastrointestinal-associated lymphoid tissue is a highly susceptible site for transmission, we hypothesized that reduced gut mucosal immune reactivity may contribute to reduced HIV-1 susceptibility in HESN men with a history of numerous rectal sexual exposures. To test this, we used ex vivo mucosal explants from freshly acquired colorectal biopsies from healthy control and HESN subjects who were stimulated with specific innate immune ligands and inactivated whole pathogens. Immune reactivity was then assessed via cytokine arrays and proteomic analysis. Mucosal immune cell compositions were quantified via immunohistochemistry. We found that explants from HESN subjects produced less proinflammatory cytokines compared with controls following innate immune stimulation; while noninflammatory cytokines were similar between groups. Proteomic analysis identified several immune response proteins to be differentially expressed between HIV-1-stimulated HESN and control explants. Immunohistochemical examination of colorectal mucosa showed similar amounts of T cells, macrophages, and dendritic cells between groups. The results of this pilot study suggest that mucosal innate immune reactivity is dampened in HESN versus control groups, despite presence of similar densities of immune cells in the colorectal mucosa. This observed modulation of the rectal mucosal immune response may contribute to lower risk of mucosal HIV-1 transmission in these individuals.

Comparison of Mucosal Markers of Human Immunodeficiency Virus Susceptibility in Healthy Premenopausal Versus Postmenopausal Women

The objective of this study was to characterize cervicovaginal (CV) mucosal factors modulating susceptibility to human immunodeficiency virus (HIV) acquisition in healthy premenopausal (PRE) and postmenopausal (POST) women before and after treatment with estradiol (E2). We compared CV mucosal epithelial histology and immune cells, vaginal microbiota, antimicrobial activity of and soluble mucosal protein concentrations in the CV fluid lavage (CVL), and p24 antigen production after ex vivo infection of ectocervical tissues with HIV-1_BaL among PRE women (n = 20) in the follicular and luteal phases of the menstrual cycle and POST women (n = 17) at baseline and after ∼1 month of treatment with 0.01% vaginal E2 cream. Compared to PRE women, we measured higher levels of p24 antigen after ex vivo infection in tissues from POST women. POST women had a significantly thinner vaginal epithelium with decreased tight junction proteins and a higher density of mucosal immune T cells and lower levels of CD1a antigen-presenting cells, antimicrobial peptides, and inflammatory cytokines in the CVL (p values <.05). POST women had higher vaginal pH and lower vaginal Lactobacilli (p values <.05) than PRE women. After vaginal E2 therapy, CV endpoints and ex vivo HIV replication in POST tissues were similar to those observed in PRE tissues. The CV mucosa in POST women is thinned and compromised, with increased HIV-target immune cells and decreased antimicrobial factors, being more susceptible to HIV infection. After POST women receive topical E2 treatment, mucosal endpoints are similar to PRE levels.

Precursor Forms of Vitamin D Reduce HIV-1 Infection In Vitro

BACKGROUND

Although the anti-HIV-1 effects of vitamin D (VitD) have been reported, mechanisms behind such protection remain largely unexplored.

METHODS

The effects of two precursor forms (cholecalciferol/calciol at 0.01, 1 and 100 nM and calcidiol at 100 and 250 nM) on HIV-1 infection, immune activation, and gene expression were analyzed in vitro in cells of Colombian and Italian healthy donors. We quantified levels of released p24 by enzyme-linked immunosorbent assay, of intracellular p24 and cell-surface expression of CD38 and HLA-DR by flow cytometry, and mRNA expression of antiviral and immunoregulatory genes by real-time reverse transcription-polymerase chain reaction.

RESULTS

Cholecalciferol decreased the frequency of HIV-1-infected p24CD4 T cells and levels of p24 in supernatants in a dose-dependent manner. Moreover, the CD4CD38HLA-DR and CD4CD38HLA-DR subpopulations were more susceptible to infection but displayed the greatest cholecalciferol-induced decreases in infection rate by an X4-tropic strain. Likewise, cholecalciferol at its highest concentration decreased the frequency of CD38HLA-DR but not of CD38HLA-DR T-cell subsets. Analyzing the effects of calcidiol, the main VitD source for immune cells and an R5-tropic strain as the most frequently transmitted virus, a reduction in HIV-1 productive infection was also observed. In addition, an increase in mRNA expression of APOBEC3G and PI3 and a reduction of TRIM22 and CCR5 expression, this latter positively correlated with p24 levels, was noted.

CONCLUSIONS

VitD reduces HIV-1 infection in T cells possibly by inducing antiviral gene expression, reducing the viral co-receptor CCR5 and, at least at the highest cholecalciferol concentration, by promoting an HIV-1-restrictive CD38HLA-DR immunophenotype.

High Expression of Antiviral and Vitamin D Pathway Genes Are a Natural Characteristic of a Small Cohort of HIV-1-Exposed Seronegative Individuals

Natural resistance to HIV-1 infection is influenced by genetics, viral-exposure, and endogenous immunomodulators such as vitamin D (VitD), being a multifactorial phenomenon that characterizes HIV-1-exposed seronegative individuals (HESNs). We compared mRNA expression of 10 antivirals, 5 immunoregulators, and 3 VitD pathway genes by qRT-PCR in cells of a small cohort of 11 HESNs, 16 healthy-controls (HCs), and 11 seropositives (SPs) at baseline, in response to calcidiol (VitD precursor) and/or aldithriol-2-(AT2)-inactivated HIV-1. In addition, the expression of TIM-3 on T and NK cells of six HCs after calcidiol and calcitriol (active VitD) treatments was evaluated by flow cytometry. Calcidiol increased the mRNA expression of HAVCR2 (TIM-3; Th1-cells inhibitor) in HCs and HESNs. AT2-HIV-1 increased the mRNA expression of the activating VitD enzyme CYP27B1, of the endogenous antiviral proteins MX2, TRIM22, APOBEC3G, and of immunoregulators ERAP2 and HAVCR2, but reduced the mRNA expression of VitD receptor (VDR) and antiviral peptides PI3 and CAMP in all groups. Remarkably, higher mRNA levels of VDR, CYP27B1, PI3, CAMP, SLPI, and of ERAP2 were found in HESNs compared to HCs either at baseline or after stimuli. Furthermore, calcitriol increases the percentage of CD4+ T cells expressing TIM-3 protein compared to EtOH controls. These results suggest that high mRNA expression of antiviral and VitD pathway genes could be genetically determined in HESNs more than viral-induced at least in peripheral blood mononuclear cells. Moreover, the virus could potentiate bio-activation and use of VitD, maintaining the homeostasis of the immune system. Interestingly, VitD-induced TIM-3 on T cells, a T cell inhibitory and anti-HIV-1 molecule, requires further studies to analyze the functional outcomes during HIV-1 infection.

Neither vaginal nor buccal administration of 800 μg misoprostol alters mucosal and systemic immune activation or the cervicovaginal microbiome: a pilot study

OBJECTIVES

The aim of the study was to assess the extent to which misoprostol alters mucosal or systemic immune responses following either buccal or vaginal administration.

METHODS

This was a prospective, crossover pilot study of 15 healthy, reproductive-age women. Women first received 800 μg misoprostol either via buccal or vaginal administration and were crossed over 1 month later to receive the drug via the other route. Cervicovaginal lavage samples, cervical Cytobrush samples, cervicovaginal swabs, urine and blood were obtained immediately prior to drug administration and the following day. Parameters assessed included urine and cervicovaginal misoprostol levels, whole blood cytokine responses (by ELISA) to immune stimulation with lipopolysaccharide, peripheral blood and cervical lymphocyte phenotyping by flow cytometry, cervicovaginal antimicrobial peptide measurement by ELISA and vaginal microbial ecology assessment by 16S rRNA sequencing.

RESULTS

Neither buccal nor vaginal misoprostol significantly altered local or systemic immune and microbiological parameters.

CONCLUSION

In this pilot study, we did not observe significant alteration of mucosal or systemic immunology or vaginal microbial ecology 1 day after drug administration following either the buccal or vaginal route.

HIV-1-negative female sex workers sustain high cervical IFNɛ, low immune activation, and low expression of HIV-1-required host genes

Sex workers practicing in high HIV endemic areas have been extensively targeted to test anti-HIV prophylactic strategies. We hypothesize that in women with high levels of genital exposure to semen changes in cervico-vaginal mucosal and/or systemic immune activation will contribute to a decreased susceptibility to HIV-1 infection. To address this question, we assessed sexual activity and immune activation status (in peripheral blood), as well as cellular infiltrates and gene expression in ectocervical mucosa biopsies in female sex workers (FSWs; n=50), as compared with control women (CG; n=32). FSWs had low-to-absent HIV-1-specific immune responses with significantly lower CD38 expression on circulating CD4(+) or CD8(+) T-cells (both: P<0.001) together with lower cervical gene expression of genes associated with leukocyte homing and chemotaxis. FSWs also had increased levels of interferon-ɛ (IFNɛ) gene and protein expression in the cervical epithelium together with reduced expression of genes associated with HIV-1 integration and replication. A correlative relationship between semen exposure and elevated type-1 IFN expression in FSWs was also established. Overall, our data suggest that long-term condomless sex work can result in multiple changes within the cervico-vaginal compartment that would contribute to sustaining a lower susceptibility for HIV-1 infection in the absence of HIV-specific responses.

Antiviral molecules correlate with vitamin D pathway genes and are associated with natural resistance to HIV-1 infection

The relationship between the immunomodulatory effects of Vitamin D (VitD) and the expression of anti-HIV-1 molecules has not been explored in HIV-1-exposed seronegative individuals (HESNs). Higher mRNA levels of cathelicidin and HAD-4 in oral-mucosa and peripheral-blood, along with higher CYP24A1 mRNA in vaginal-mucosa and lower TLR2 mRNA in endocervical-mucosa were found in HESNs compared to non-exposed controls. Furthermore, the mRNA of anti-HIV molecules Elafin, TRIM5, Cathelicidin, HAD-4 and RNase7, previously associated with natural resistance to HIV-1 infection, positively correlated with the mRNA expression of VDR in HESNs, suggesting the potential participation of VitD in natural resistance to HIV-1.

Molecular Signatures of Immune Activation and Epithelial Barrier Remodeling Are Enhanced during the Luteal Phase of the Menstrual Cycle: Implications for HIV Susceptibility

The variable infectivity and transmissibility of HIV/SHIV has been recently associated with the menstrual cycle, with particular susceptibility observed during the luteal phase in nonhuman primate models and ex vivo human explant cultures, but the mechanism is poorly understood. Here, we performed an unbiased, mass spectrometry-based proteomic analysis to better understand the mucosal immunological processes underpinning this observed susceptibility to HIV infection. Cervicovaginal lavage samples (n = 19) were collected, characterized as follicular or luteal phase using days since last menstrual period, and analyzed by tandem mass spectrometry. Biological insights from these data were gained using a spectrum of computational methods, including hierarchical clustering, pathway analysis, gene set enrichment analysis, and partial least-squares discriminant analysis with LASSO feature selection. Of the 384 proteins identified, 43 were differentially abundant between phases (P < 0.05, ≥2-fold change). Cell-cell adhesion proteins and antiproteases were reduced, and leukocyte recruitment (interleukin-8 pathway, P = 1.41E-5) and extravasation proteins (P = 5.62E-4) were elevated during the luteal phase. LASSO/PLSDA identified a minimal profile of 18 proteins that best distinguished the luteal phase. This profile included cytoskeletal elements and proteases known to be involved in cellular movement. Gene set enrichment analysis associated CD4(+) T cell and neutrophil gene set signatures with the luteal phase (P < 0.05). Taken together, our findings indicate a strong association between proteins involved in tissue remodeling and leukocyte infiltration with the luteal phase, which may represent potential hormone-associated mechanisms of increased susceptibility to HIV.

IMPORTANCE

Recent studies have discovered an enhanced susceptibility to HIV infection during the progesterone-dominant luteal phase of the menstrual cycle. However, the mechanism responsible for this enhanced susceptibility has not yet been determined. Understanding the source of this vulnerability will be important for designing efficacious HIV prevention technologies for women. Furthermore, these findings may also be extrapolated to better understand the impact of exogenous hormone application, such as the use of hormonal contraceptives, on HIV acquisition risk. Hormonal contraceptives are the most widely used contraceptive method in sub-Saharan Africa, the most HIV-burdened area of the world. For this reason, research conducted to better understand how hormones impact host immunity and susceptibility factors important for HIV infection is a global health priority.

Non-Cationic Proteins Are Associated with HIV Neutralizing Activity in Genital Secretions of Female Sex Workers

Objective

Cationic proteins found in cervicovaginal secretions (CVS) are known to contribute to the early antiviral immune response against HIV-infection in vitro. We here aimed to define additional antiviral factors that are over-expressed in CVS from female sex workers at high risk of infection.

Methods

CVS were collected from Kenyan HIV-seronegative (n = 34) and HIV-seropositive (n = 12) female sex workers, and were compared with those from HIV-seronegative low-risk women (n = 12). The highly exposed seronegative (HESN) sex workers were further divided into those with less (n = 22) or more (n = 12) than three years of documented sex work. Cationic protein-depleted CVS were assessed for HIV-neutralizing activity by a PBMC-based HIV-neutralizing assay, and then characterized by proteomics.

Results

HIV neutralizing activity was detected in all unprocessed CVS, however only CVS from the female sex worker groups maintained its HIV neutralizing activity after cationic protein-depletion. Differentially abundant proteins were identified in the cationic protein-depleted secretions including 26, 42, and 11 in the HESN>3yr, HESN<3yr, and HIV-positive groups, respectively. Gene ontology placed these proteins into functional categories including proteolysis, oxidation-reduction, and epidermal development. The proteins identified in this study include proteins previously associated with the HESN phenotype in other cohorts as well as novel proteins not yet associated with anti-HIV activities.

Conclusion

While cationic proteins appear to contribute to the majority of the intrinsic HIV neutralizing activity in the CVS of low-risk women, a broader range of non-cationic proteins were associated with HIV neutralizing activity in HESN and HIV-positive female sex workers. These results indicate that novel protein factors found in CVS of women with high-risk sexual practices may have inherent antiviral activity, or are involved in other aspects of anti-HIV host defense, and warrant further exploration into their mode of action.

Factores solubles con actividad antiviral: en búsqueda de nuevos blancos terapéuticos para la infección por el VIH-1

Los mecanismos innatos antivirales han resultado de gran interés debido a su uso potencial para la prevención y tratamiento de la infección por el VIH. En particular, los factores solubles antivirales han sido objeto de múltiples investigaciones por su capacidad de inhibir diferentes pasos del ciclo replicativo viral y de potenciar la respuesta inmune del hospedero. Entre estos factores solubles se destacan TRIM-5α, APOBEC3G, SAMHD1, ELAFIN, SERPINA1 y SLPI, que actúan directamente sobre la partícula viral o la célula, o promueven la producción de moléculas involucradas en la respuesta inmune contra el virus. Algunos de ellos se han correlacionado con un bajo riesgo de adquirir la infección por el VIH o con una lenta progresión a sida. La exploración de los mecanismos antivirales de estas proteínas es requisito para el desarrollo de nuevas alternativas terapéuticas.

Short communication: genital tumor growth factor-β1 levels in HIV-infected Indian women are associated with reduced levels of innate antimicrobial products and increased HIV shedding

Tumor growth factor (TGF)-β1 is a cytokine with potent immunoinhibitory functions and is known to be secreted by vaginal epithelial cells. The present study was designed to determine the association of cervicovaginal levels of TGF- β1 with various innate immune secretions such as cytokines and antimicrobial polypeptides [Trappin-2/Elafin and secretory leukocyte protease inhibitor (SLPI)] and cervical HIV shedding in HIV-infected Indian women. TGF- β1, antimicrobial polypeptides, and cytokine levels were estimated in the cervicovaginal lavages (CVLs) of 36 age-matched HIV-infected and 31 HIV-uninfected asymptomatic Indian women using an ELISA and Bio-Plex Assay, respectively. The nonparametric Mann-Whitney test and Spearman's test were used to compare the levels from both the groups and to determine the association of the TGF-β1 levels with cervical viral shedding and antimicrobial peptides. The levels of Trappin-2/Elafin and SLPI were similar in the CVLs of HIV-infected and HIV-uninfected women, but were significantly associated with a low cervical viral load (r=-0.501, p=0.005 for Trappin-2/Elafin and r=-0.488, p=0.007 for SLPI). Eleven (30.5%) of the 36 HIV-infected women showed 5- to 30-fold higher levels of TGF-β1 as compared to the levels in uninfected women. The TGF-β1 levels were significantly associated with higher cervical viral load (r=0.425, p=0.03) and with lower levels of Trappin-2/Elafin (r=-0.407, p=0.03) and SLPI (r=-0.405, p=0.04). The findings indicate a possible interdependent mechanism driving the identified higher TGF-β1 and lower antimicrobial peptide (Trappin-2/Elafin and SLPI) levels at the genital mucosa surface in HIV-infected women. We postulate that a combination of increased TGF-β1 secretion and altered levels of Trappin-2/Elafin and SLPI contributes to increased HIV shedding. The observation warrants further studies to identify the underlying mechanisms linking increased mucosal TGF-β1 levels and genital HIV shedding. Considering the known association of HIV and cervical cancers, it will also be important to assess the predictive capacity of TGF-β1 levels in HIV-associated cervical malignancies.

Increased Serpin A5 levels in the cervicovaginal fluid of HIV-1 exposed seronegatives suggest that a subtle balance between serine proteases and their inhibitors may determine susceptibility to HIV-1 infection

HIV-exposed seronegative individuals (HESNs) are persons who remain seronegative despite repeated exposure to HIV, suggesting an in vivo resistance mechanism to HIV. Elucidation of endogenous factors responsible for this phenomenon may aid in the development of new classes of microbicides and therapeutics. We compared cervicovaginal protein abundance profiles between high-risk HESN and two control groups: low-risk HESN and HIV-positives. Four iTRAQ-based quantitative experiments were performed using samples classified based on presence/absence of particular gynaecological conditions. After statistical analysis, two proteins were shown to be differentially abundant between high-risk HESNs and control groups. Serpin A5, a serine proteinase inhibitor and Myeloblastin, a serine protease, were up- and downregulated, respectively. Commercially available ELISA assays were used to confirm differential Serpin A5 levels. These results suggest that HIV resistance in CVF of HESNs is the result of a delicate balance between two complementary mechanisms: downregulation of serine proteinases and upregulation of their inhibitors.

Immune correlates of HIV exposure without infection in foreskins of men from Rakai, Uganda

Human immunodeficiency virus (HIV) susceptibility is heterogenous, with some HIV-exposed but seronegative (HESN) individuals remaining uninfected despite repeated exposure. Previous studies in the cervix have shown that reduced HIV susceptibility may be mediated by immune alterations in the genital mucosa. However, immune correlates of HIV exposure without infection have not been investigated in the foreskin. We collected sub-preputial swabs and foreskin tissue from HESN (n=20) and unexposed control (n=57) men undergoing elective circumcision. Blinded investigators assayed swabs for HIV-neutralizing IgA, innate antimicrobial peptides, and cytokine levels. Functional T-cell subsets from foreskin tissue were assessed by flow cytometry. HESN foreskins had elevated α-defensins (3,027 vs. 1,795 pg ml(-1), P=0.011) and HIV-neutralizing IgA (50.0 vs. 13.5% of men, P=0.019). Foreskin tissue from HESN men contained a higher density of CD3 T cells (151.9 vs. 69.9 cells mm(-2), P=0.018), but a lower proportion of these was Th17 cells (6.12 vs. 8.04% of CD4 T cells, P=0.007), and fewer produced tumor necrosis factor α (TNFα) (34.3 vs. 41.8% of CD4 T cells, P=0.037; 36.9 vs. 45.7% of CD8 T cells, P=0.004). A decrease in the relative abundance of susceptible CD4 T cells and local TNFα production, in combination with HIV-neutralizing IgA and α-defensins, may represent a protective immune milieu at a site of HIV exposure.

Secreted mucosal antimicrobials in the female reproductive tract that are important to consider for HIV prevention

The mucosal microenvironment of the female reproductive tract (FRT) is rich in secreted endogenous antimicrobials that provide the first line of defense against pathogens. This review focuses on the spectrum of secreted antimicrobials found in the FRT that have anti-HIV functions and are regulated by the natural hormonal changes in women's life cycle. Understanding the complex nature of FRT, mucosal microenvironment will enable us to better design therapeutic interventions for women against sexually transmitted pathogens.

Acting locally: innate mucosal immunity in resistance to HIV-1 infection in Kenyan commercial sex workers

Cohort studies of female commercial sex workers (CSWs) in Kenya were among the first to identify highly HIV-1-exposed seronegative (HESN) individuals. As natural resistance is usually mediated by innate immune mechanisms, we focused on determining whether expression and function of innate signaling pathways were altered locally in the genital mucosa of HESN CSWs. Our results demonstrated that selected pattern-recognition receptors (PRRs) were significantly reduced in expression in cervical mononuclear cells (CMCs) from HESN compared with the new HIV-negative (HIV-N) and HIV-positive (HIV-P) groups. Although baseline levels of secreted cytokines were reduced in CMCs of HESN, they were highly stimulated following exposure to ssRNA40 in vitro. Importantly, cervical epithelial cells from HESN also expressed reduced levels of PRRs, but Toll-like receptor 3 (TLR3) and TLR7 as well as nuclear factor-κB and activator protein 1 were highly expressed and activated. Lastly, inflammatory cytokines interleukin (IL)-1β, IL-8, and RANTES (regulated and normal T cell expressed and secreted) were detected at lower levels in cervicovaginal lavage of HESN compared with the HIV-N and HIV-P groups. Overall, our study reveals a local microenvironment of HIV resistance in the genital mucosa consisting of a finely controlled balance of basal immune quiescence with a focused and potent innate anti-viral response critical to resistance to sexual transmission of HIV-1.

Mucosal correlates of protection in HIV-1-exposed sero-negative persons

Resistance to HIV-1 infection in HIV-1-exposed sero-negative (HESN) persons offers a promising opportunity to identify mechanisms of 'natural' protection. Unique features of the mucosa in particular may contribute to this protection. Here, we highlight several key issues pertaining to the mucosal correlates of protection in HESN persons, including humoral immune responses, mechanisms of mucosal HIV-1 neutralization, immune cell activation, and role of the microbiota in mucosal responses. We also discuss mucosal model systems that can be used to investigate the mechanisms of resistance in HESN subjects. A clear understanding of the mucosal correlates of protection against HIV-1 in HESN persons will provide critical new insights for the development of effective vaccine and microbicide strategies for the prevention of HIV-1 transmission.

Role of the innate immunity in female reproductive tract

The mucosal immune system in the female reproductive tract (FRT) is well equipped to meet the sexually transmitted pathogens, allogeneic sperm, and the immunologically distinct fetus. Analysis of the FRT indicates that epithelial cells provide a physical barrier against pathogens and microbial infections as well as secretions containing anti-microbial peptides, cytokines, and chemokines which recruit and activate immune cells. Epithelial and immune cells confer protection in part through Toll-like receptors. The aim of this literature is to review the diverse components of the innate immune system, contributing to an exclusive protection system throughout the FRT.

Immune quiescence: a model of protection against HIV infection

Aberrant immune activation is a strong correlate of HIV disease progression, but little is known about how immune activation alters susceptibility to HIV infection. Susceptibility to HIV infection varies between individuals, but the immunological determinants of HIV transmission are not well understood. Here, we present evidence from studies of HIV transmission in the context of clinical trials and HIV-exposed seronegative (HESN) cohorts that implicates elevated immune activation as a risk factor for acquiring HIV. We propose a model of protection from infection based on a phenotype of low baseline immune activation referred to as immune quiescence. Immune quiescence is evidenced by reduced expression of T cell activation markers, low levels of generalized gene transcription and low levels of proinflammatory cytokine and chemokine production in the periphery and genital mucosa of HESN. Since HIV preferentially replicates in activated CD4+ T cells, immune quiescence may protect against infection by limiting HIV target cell availability. Although the determinants of immune quiescence are unclear, several potential factors have been identified that may be involved in driving this phenotype. HESN were shown to have elevated proportions of regulatory T cells (Tregs), which are known to suppress T cell activation. Likewise, proteins involved in controlling inflammation in the genital tract have been found to be elevated in HESN. Furthermore, expression of interferon regulatory factor 1 (IRF-1) is reduced in HESN as a consequence of genetic polymorphisms and differential epigenetic regulation. Since IRF-1 is an important regulator of immune responses, it may play a role in maintaining immune quiescence. Based on this model, we propose a novel avenue for HIV prevention targeted based on reducing host mucosal immune activation.

Unbiased proteomics analysis demonstrates significant variability in mucosal immune factor expression depending on the site and method of collection

Female genital tract secretions are commonly sampled by lavage of the ectocervix and vaginal vault or via a sponge inserted into the endocervix for evaluating inflammation status and immune factors critical for HIV microbicide and vaccine studies. This study uses a proteomics approach to comprehensively compare the efficacy of these methods, which sample from different compartments of the female genital tract, for the collection of immune factors. Matching sponge and lavage samples were collected from 10 healthy women and were analyzed by tandem mass spectrometry. Data was analyzed by a combination of differential protein expression analysis, hierarchical clustering and pathway analysis. Of the 385 proteins identified, endocervical sponge samples collected nearly twice as many unique proteins as cervicovaginal lavage (111 vs. 61) with 55% of proteins common to both (213). Each method/site identified 73 unique proteins that have roles in host immunity according to their gene ontology. Sponge samples enriched for specific inflammation pathways including acute phase response proteins (p = 3.37×10⁻²⁴) and LXR/RXR immune activation pathways (p = 8.82×10⁻²²) while the role IL-17A in psoriasis pathway (p = 5.98×10⁻⁴) and the complement system pathway (p = 3.91×10⁻³) were enriched in lavage samples. Many host defense factors were differentially enriched (p<0.05) between sites including known/potential antimicrobial factors (n = 21), S100 proteins (n = 9), and immune regulatory factors such as serpins (n = 7). Immunoglobulins (n = 6) were collected at comparable levels in abundance in each site although 25% of those identified were unique to sponge samples. This study demonstrates significant differences in types and quantities of immune factors and inflammation pathways collected by each sampling technique. Therefore, clinical studies that measure mucosal immune activation or factors assessing HIV transmission should utilize both collection methods to obtain the greatest representation of immune factors secreted into the female genital tract.

Proteomics as a novel HIV immune monitoring tool

PURPOSE OF REVIEW

There is still a fundamental lack of understanding of what protected vaccinee's in the moderately successful RV144 Thailand trial. It is clear that better tools are needed to identify and study correlates of protection and immune responses to vaccine challenge. Quantitative mass spectrometry (MS) has evolved considerably to become a useful tool in biomarker discovery; however, until recently it has been scarcely used to define host responses to HIV exposure and/or viral infection. In this review we discuss current quantitative MS techniques, their application in current HIV studies as well as novel approaches that could be used to better examine innate or adaptive immune responses in HIV vaccine or microbicide trials.

RECENT FINDINGS

Several recently published studies have allowed researchers to utilize quantitative MS as part of a systems biology approach to better understand the HIV-affected host's interaction with HIV and/or vaccine challenge. Proteomics has shown it can play a major role in studies to demonstrate insight into HIV replication, early stages of pathogenesis, and identify potential correlates of mucosal protection.

SUMMARY

Novel advances in quantitative proteomic techniques are allowing the opportunity to profile and evaluate HIV specific innate and adaptive immune responses, and will increase our understanding of HIV pathogenesis.

Antiviral activity of trappin-2 and elafin in vitro and in vivo against genital herpes

Serine protease inhibitor elafin (E) and its precursor, trappin-2 (Tr), have been associated with mucosal resistance to HIV-1 infection. We recently showed that Tr/E are among principal anti-HIV-1 molecules in cervicovaginal lavage (CVL) fluid, that E is ∼130 times more potent than Tr against HIV-1, and that Tr/E inhibited HIV-1 attachment and transcytosis across human genital epithelial cells (ECs). Since herpes simplex virus 2 (HSV-2) is a major sexually transmitted infection and risk factor for HIV-1 infection and transmission, we assessed Tr/E contribution to defense against HSV-2. Our in vitro studies demonstrated that pretreatment of endometrial (HEC-1A) and endocervical (End1/E6E7) ECs with human Tr-expressing adenovirus (Ad/Tr) or recombinant Tr/E proteins before or after HSV-2 infection resulted in significantly reduced virus titers compared to those of controls. Interestingly, E was ∼7 times more potent against HSV-2 infection than Tr. Conversely, knockdown of endogenous Tr/E by small interfering RNA (siRNA) significantly increased HSV-2 replication in genital ECs. Recombinant Tr and E reduced viral attachment to genital ECs by acting indirectly on cells. Further, lower viral replication was associated with reduced secretion of proinflammatory interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-α) and decreased NF-κB nuclear translocation. Additionally, protected Ad/Tr-treated ECs demonstrated enhanced interferon regulatory factor 3 (IRF3) nuclear translocation and increased antiviral IFN-β in response to HSV-2. Lastly, in vivo studies of intravaginal HSV-2 infection in Tr-transgenic mice (Etg) showed that despite similar virus replication in the genital tract, Etg mice had reduced viral load and TNF-α in the central nervous system compared to controls. Collectively, this is the first experimental evidence highlighting anti-HSV-2 activity of Tr/E in female genital mucosa.

Human rElafin Inhibits HIV-1 Replication in Its Natural Target Cells

Trappin-2/elafin is a novel innate immune factor that belongs to the serine protease inhibitor family and has known antibacterial, antifungal, and antiviral properties. In this study, we further investigated the anti-HIV activity of elafin using different cellular models and both X4– and R5–HIV-1 laboratory strains. We compared the antiviral activity of human recombinant elafin (rElafin) with three well-known antiretroviral drugs, AZT, tenofovir, and enfuvirtide. We have found that when the virus is pre-incubated with rElafin prior to the infection of the cells, HIV-1 replication is significantly inhibited. In target T cells and human peripheral blood mononuclear cells, maximal inhibition was achieved using submicromolar concentrations, and rElafin was found to be as potent as enfuvirtide, showing its potential for therapeutic application. We also show data on the mechanism of the antiviral activity of rElafin. We have demonstrated that rElafin neither binds to CD4, CXCR4, or CCR5 host cell receptors, nor to the viral glycoproteins gp120 and gp41. Furthermore, in our cell-to-cell fusion assays, in contrast to enfuvirtide, rElafin failed to block cell fusion. Altogether our results indicate that rElafin interferes with HIV replication at the early steps of its cycle but with a different mechanism of action than enfuvirtide. This study provides the first experimental evidence that elafin inhibits HIV replication in its natural target cells; therefore, elafin might have potential for its development as a new anti-HIV drug or microbicide.

A systems biology examination of the human female genital tract shows compartmentalization of immune factor expression

Many mucosal factors in the female genital tract (FGT) have been associated with HIV susceptibility, but little is known about their anatomical distribution in the FGT compartments. This study comprehensively characterized global immune factor expression in different tissue sites of the lower and upper FGT by using a systems biology approach. Tissue sections from the ectocervix, endocervix, and endometrium from seven women who underwent hysterectomy were analyzed by a combination of quantitative mass spectrometry and immunohistochemical staining. Of the >1,000 proteins identified, 281 were found to be differentially abundant in different tissue sites. Hierarchical clustering identified four major functional pathways distinguishing compartments, including innate immune pathways (acute-phase response, LXR/RXR) and development (RhoA signaling, gluconeogenesis), which were enriched in the ectocervix/endocervix and endometrium, respectively. Immune factors important for HIV susceptibility, including antiproteases, immunoglobulins, complement components, and antimicrobial factors, were most abundant in the ectocervix/endocervix, while the endometrium had a greater abundance of certain factors that promote HIV replication. Immune factor abundance is heterogeneous throughout the FGT and shows unique immune microenvironments for HIV based on the exposure site. This may have important implications for early events in HIV transmission and site-specific susceptibility to HIV in the FGT.

Innate immunity in the vagina (part I): estradiol inhibits HBD2 and elafin secretion by human vaginal epithelial cells

PROBLEM

Vaginal epithelial cells (VEC) are the first line of defense against incoming pathogens in the female reproductive tract. Their ability to produce the anti-HIV molecules elafin and HBD2 under hormonal stimulation is unknown.

METHOD OF STUDY

Vaginal epithelial cells were recovered using a menstrual cup and cultured overnight prior to treatment with estradiol (E₂), progesterone (P₄) or a panel of selective estrogen response modulators (SERMs). Conditioned media were recovered and analyzed for protein concentration and anti-HIV activity.

RESULTS

E₂ significantly decreased the secretion of HBD2 and elafin by VEC over 48 hrs, while P4 and the SERMs (tamoxifen, PHTTP, ICI or Y134) had no effect. VEC conditioned media from E₂ -treated cells had no anti-HIV activity, while that from E₂ /P₄ -treated cells significantly inhibited HIV-BaL infection.

CONCLUSION

The menstrual cup allows for effective recovery of primary VEC. Their production of HBD2 and elafin is sensitive to E₂, suggesting that innate immune protection varies in the vagina across the menstrual cycle.

Anti-HIV-1 activity of elafin depends on its nuclear localization and altered innate immune activation in female genital epithelial cells

Elafin (E) and its precursor trappin-2 (Tr) are alarm antiproteases with antimicrobial and immunomodulatory activities. Tr and E (Tr/E) have been associated with HIV-1 resistance. We recently showed that Tr/E reduced IL-8 secretion and NF-κB activation in response to a mimic of viral dsRNA and contributed to anti-HIV activity of cervicovaginal lavage fluid (CVL) of HIV-resistant (HIV-R) commercial sex workers (CSWs). Additionally, Tr, and more so E, were found to inhibit attachment/entry and transcytosis of HIV-1 in human endometrial HEC-1A cells, acting through virus or cells. Given their immunomodulatory activity, we hypothesized that Tr/E could exert anti-HIV-1 activity at multiple levels. Here, using tagged and untagged Tr/E proteins, we comparatively evaluated their protease inhibitory, anti-HIV-1, and immunomodulatory activities, and cellular distribution. E appeared to function as an autocrine/paracrine factor in HEC-1A cells, and anti-HIV-1 activity of E depended on its unmodified N-terminus and altered cellular innate activation, but not its antiprotease activity. Specifically, exogenously added N-terminus-unmodified E was able to enter the nucleus and to reduce viral attachment/entry and transcytosis, preferentially affecting R5-HIV-1(ADA), but not X4-HIV-1(IIIB). Further, anti-HIV-1 activity of E was associated with significantly decreased HIV-1-triggered IL-8 release, attenuated NF-κB/p65 nuclear translocation, and significantly modulated mRNA expression of innate sensors TLR3 and RIG-I in HEC-1A cells. Most importantly, we found that elevated Tr/E in CVLs of HIV-R CSWs were associated with lower mRNA levels of TLRs 2, 3, 4 and RIG-I in the genital ECs from this cohort, suggesting a link between Tr/E, HIV-1 resistance and modulated innate viral recognition in the female genital mucosa. Collectively, our data indicate that unmodified N-terminus is critical for intranuclear localization and anti-HIV-1 activity of E. We also propose that E-mediated altered cellular innate activation most likely contributes to the HIV-R phenotype of these subjects.

Genital tract viral load in HIV Type 1-positive women correlates with specific cytokine levels in cervical-vaginal secretions but is not a determinant of infectious virus or anti-HIV activity

As the AIDS epidemic continues with women being disproportionately affected, it is crucial to understand factors that predict the risk of heterosexual HIV-1 transmission. We investigated whether genital tract viral load (GTVL) in cervical-vaginal lavages (CVL) from HIV-1-positive women with moderately low CD4 T cell counts correlates with cytokine levels, antimicrobial concentrations, and intrinsic anti-HIV activity. CVL were collected from 19 HIV-1-positive women with moderately low CD4 T cell counts [mean 381 cells/mm(3) (227-536 cells/mm(3))]. None of the women was on antiretroviral therapy. The women were categorized into those with detectable GTVL or those with undetectable GTVL (detectable GTVL RNA levels > 400 copies/ml). Women were also categorized according to bacterial vaginosis (BV) status irrespective of GTVL. The TZM-bl assay was used to determine the presence of infectious virus and anti-HIV activity. Significantly higher levels of RANTES, Eotaxin, Fractalkine, IL-1α, IL-6, MCP-1, MIP1β, MIP1α, TNF-α, and GM-CSF were observed in women with detectable GTVL compared to women with undetectable GTVL. No significant differences were observed in the following cytokines and chemokines: G-CSF, IL-1RA, IL-8, and IP-10. GTVL did not correlate either with antimicrobials known to have anti-HIV activity or with the presence of infectious virus. BV status did not have a significant effect on anti-HIV activity. These findings further our understanding of the role of GTVL in determining the cytokine and chemokine milieu in the female reproductive tract.

Salivary basic proline-rich proteins are elevated in HIV-exposed seronegative men who have sex with men

OBJECTIVE

Innate mucosal factors are associated with protection in HIV-exposed seronegative (HESN) individuals, but studies of MSM have been very limited. We performed proteomic analysis of saliva from a cohort of HESN MSM who have regular unprotected oral receptive intercourse with their HIV-infected partner.

METHODS

Saliva samples from HESN (n = 25) and non-exposed male controls (n = 22) were analyzed by 2D-LC mass spectrometry. An overexpressed innate protein factor was further characterized by immunoblot, and compared with CC-chemokine expression, HIV-neutralizing activity, clinical factors, and sexual behavior.

RESULTS

Of 337 total proteins, seven were identified as differentially abundant in the HESN group. The five overabundant proteins (Basic salivary proline-rich proteins (bPRP) 2 and 3, Histatin-3, Lysozyme C, and SLPI) have known antimicrobial activity. bPRP2 showed the highest overabundance (>six-fold) in HESN individuals compared with controls (P = 0.009), including multiple isoforms. Salivary bPRP2 correlated with CC-chemokine levels in HESN individuals including RANTES (P = 0.02), MIP-1-alpha (P = 0.01), MIP-1-beta (P = 0.0002), MCP-1 (P = 0.005) and Eotaxin (P = 0.003) but not with frequency of HIV neutralizing activity, oral sexual practices, or viral load of the sexual partner.

CONCLUSION

This study identifies salivary bPRP2 as a novel soluble factor elevated in the oral compartment of HIV-exposed MSM.

A genetic polymorphism of FREM1 is associated with resistance against HIV infection in the Pumwani sex worker cohort

A subgroup of women enrolled in the Pumwani sex worker cohort remain seronegative and PCR negative for human immunodeficiency virus type 1 despite repeated exposure through high-risk sex work. Studies have shown that polymorphisms of genes involved in antigen presentation and viral restriction factors are associated with resistance to HIV infection. To discover other possible genetic factors underlying this HIV-resistant phenotype, we conducted an exploratory nonbiased, low-resolution, genome-wide single-nucleotide polymorphism (SNP) analysis comparing 60 HIV-resistant women to 48 HIV-infected controls. The SNP minor allele rs1552896, in an intron of FREM1, was significantly associated with the resistant phenotype (P = 1.68 × 10(-5); adjusted P = 2.37 × 10(-4); odds ratio [OR], 9.51; 95% confidence interval [CI], 2.82 to 32.05). We expanded the sample size by genotyping rs1552896 in the Pumwani cohort and comparing 114 HIV-resistant women to 609 HIV-infected controls and confirmed the association (P = 1.7 × 10(-4); OR, 2.67; 95% CI, 1.47 to 4.84). To validate the association in a second cohort, we genotyped 783 women enrolled in a mother-child health study and observed the minor allele of rs1552896 enriched in HIV-uninfected women (n = 488) compared to HIV-infected enrollees (n = 295) (P = 0.036; OR, 1.69; 95% CI, 0.98 to 2.93). Quantitative reverse transcription-PCR showed that FREM1 mRNA was highly expressed in tissues relevant for HIV-1 infection, and immunohistochemical analysis revealed that FREM1 protein is expressed in the ectocervical mucosa of HIV-resistant women. The significant association of rs1552896 with an HIV-resistant phenotype, together with the expression profile of FREM1 in tissues relevant to HIV infection, suggests that FREM1 is a potentially novel candidate gene for resistance to HIV infection.