HIV gp120 induced gene expression signatures in vaginal epithelial cells

Transcriptional response of vaginal epithelial cells to medroxyprogesterone acetate treatment results in decreased barrier integrity

Medroxyprogesterone acetate (MPA) is a frequently used hormonal contraceptive that has been shown to significantly increase HIV-1 susceptibility by approximately 40 %. However, the underlying mechanism by which this occurs remains unknown. Here, we examined the biological response to MPA by vaginal epithelial cells, the first cells to encounter HIV-1 during sexual transmission, in order to understand the potential mechanism(s) of MPA-mediated increase of HIV-1 infection. Using microarray analysis and in vitro assays, we characterized the response of vaginal epithelial cells, grown in biologically relevant air-liquid interface (ALI) cultures, to physiological levels of female sex hormones, estradiol (E2), progesterone (P4), or MPA. Transcriptional profiling of E2, P4 or MPA-treated vaginal epithelial cells indicated unique transcriptional profiles associated with each hormone. MPA treatment increased transcripts of genes related to cholesterol/sterol synthesis and decreased transcripts related to cell division and cell-cell adhesion, results not seen with E2 or P4 treatments. MPA treatment also resulted in unique gene expression indicative of decreased barrier integrity. Functional assays confirmed that MPA, but not E2 or P4 treatments, resulted in increased epithelial barrier permeability and inhibited cell cycle progression. The effects of MPA on vaginal epithelial cells seen in this study may help explain the increase of HIV-1 infection in women who use MPA as a hormonal contraceptive.

IFI44L expression is regulated by IRF-1 and HIV-1

Interferon (IFN)‐inducible 44 like (IFI44L) is an IFN‐stimulated gene (ISG), which is located on the same chromosome as the known antiviral ISG IFI44. Expression of IFI44L is induced by IFN and HIV‐1 infection. However, the mechanism by which IFN‐I induces IFI44L production has not yet been determined. In this study, we analyzed transcriptional regulation of IFI44L via cloning of the IFI44L promoter. We found that IFI44L has two IFN‐stimulated response elements (ISRE), which are necessary for the basal level of IFI44L transcription. IFN‐I and IFN‐II can activate the IFI44L promoter through one of the two ISREs. IFN regulatory factor (IRF)‐1 can activate transcription of IFI44L by binding to one of the ISREs. Additionally, co‐transfection of the IFI44L promoter with an HIV‐1 infectious clone or HIV‐1 infection activated IFI44L promoter transcription, but did not upregulate IFI44L expression via ISREs. These findings will help to understand the interaction between IFI44L and HIV‐1, and aid in elucidation of the role of IFI44L in the antiviral innate immune response.

Novel association of genetic variants in non-coding regulatory regions with HIV-1 infection

Host genetic variability interplays with the environment and variegating viral factors to determine the outcome in HIV-1/AIDS. Several GWAS studies have reported that genetic heterogeneity of individuals leads to differential HIV susceptibility. Proxy SNPs that are in Linkage Disequilibrium to the GWAS SNPs could be important targets in HIV pathogenesis and need to be analyzed further for their potential regulatory role. Current study thus aimed to identify novel proxy SNPs that may play a critical role in HIV susceptibility and disease progression. 372 SNPs, associated with HIV-1/AIDS pathogenesis, were retrieved via GWAS catalogue. 1854 proxy SNPs, in Linkage Disequilibrium (r² = 0.8) to the GWAS reported SNPs, were identified using the SNAP web tool. Regulatory functions of aforementioned 1854 polymorphic sites (GWAS SNPs and their proxy SNPs) were acquired from RegulomeDB. 178 of the proxy SNPs showed evidence of strong regulatory potential returning a score of ≤3. Among these regulatory SNPs, 22 had already been reported for their association with HIV/AIDS while 156 SNPs showed novel association. Three of these novel SNPs (g.rs6457282T>C, g.rs17064977C>T and g.rs3130350G>T) were validated using sequence specific PCR (SSP-PCR) on HIV-infected patients. For g.rs6457282T>C and rs17064977C>T, CT genotype was determined to be significantly associated with increased risk of HIV-1 infection (rs6457282T>C: OR = 9.5, 95% CI = 3.0792-29.3099, p = 0.0001; rs17064977C>T: OR = 8.1077, 95% CI = 3.1125-21.119, p = 0.0001). Moreover, the association of interacting protein partners of affected genes with HIV-1 elucidates the significance of corresponding SNPs in HIV disease outcome that further needs to be functionally deciphered.

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.

Hormonal influence on HIV-1 transmission in the female genital tract: New insights from systems biology

Although anti-retroviral treatments have significantly slowed down the spread of the HIV-1 pandemic, approximately 2 million new infections occur every year. The majority of new infections are in sub-Saharan Africa where rates of infection are much higher in women than men. Young women are disproportionately affected and have higher susceptibility to HIV-1. The complex interactions between HIV-1 and the female genital tract (FGT) and the mechanisms regulating susceptibility in women remain incompletely understood. In this review, we focus on the current understanding of the acute events that occur in the FGT following HIV-1 exposure with a particular focus on the effect of endogenous and exogenous sex hormones on HIV-1 susceptibility. We highlight the contribution of the recent transcriptomic and proteomic studies in providing new insights.

Transcriptional profiling of primary endometrial epithelial cells following acute HIV-1 exposure reveals gene signatures related to innate immunity

PROBLEM

Genital epithelial cells (GECs) line the mucosal surface of the female genital tract (FGT) and are the first cells that interface with both commensal microbiota and sexually transmitted pathogens. Despite the protective barrier formed by GECs, the FGT is a major site of HIV-1 infection. This highlights the importance of studying the interaction of HIV-1 and GECs.

METHOD OF STUDY

Using microarray analysis, we characterized the transcriptional profile of primary endometrial GECs grown in the presence or absence of physiological levels of E2 (10^-9  mol/L) or P4 (10^-7  mol/L) following acute exposure to HIV-1 for 6 hours.

RESULTS

Acute exposure of primary endometrial GECs to HIV-1 resulted in the expression of genes related to inflammation, plasminogen activation, adhesion and diapedesis and interferon response. Interestingly, exposure to HIV-1 in the presence of E2 and P4 resulted in differential transcriptional profiles, suggesting that the response of primary endometrial GECs to HIV-1 exposure is modulated by female sex hormones.

CONCLUSION

The gene expression signature of endometrial GECs indicates that the response of these cells may be key to determining host susceptibility to HIV-1 and that sex hormones modulate these interactions. This study allows us to explore possible mechanisms that explain the hormone-mediated fluctuation of HIV-1 susceptibility 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.

Characterization of host immunity during persistent vaginal colonization by Group B Streptococcus

Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterium, which colonizes the vaginal tract in 10-30% of women. Colonization is transient in nature, and little is known about the host and bacterial factors controlling GBS persistence. Gaining insight into these factors is essential for developing therapeutics to limit maternal GBS carriage and prevent transmission to the susceptible newborn. In this work, we have used human cervical and vaginal epithelial cells, and our established mouse model of GBS vaginal colonization, to characterize key host factors that respond during GBS colonization. We identify a GBS strain that persists beyond a month in the murine vagina, whereas other strains are more readily cleared. Correspondingly, we have detected differential cytokine production in human cell lines after challenge with the persistent strain vs. other GBS strains. We also demonstrate that the persistent strain more readily invades cervical cells compared with vaginal cells, suggesting that GBS may potentially use the cervix as a reservoir to establish long-term colonization. Furthermore, we have identified interleukin-17 production in response to long-term colonization, which is associated with eventual clearance of GBS. We conclude that both GBS strain differences and concurrent host immune responses are crucial in modulating vaginal colonization.

HIV-1 gp120 induces TLR2- and TLR4-mediated innate immune activation in human female genital epithelium

Although women constitute half of all HIV-1-infected people worldwide (UNAIDS World AIDS Day Report, 2011), the earliest events in the female reproductive tract (FRT) during heterosexual HIV-1 transmission are poorly understood. Recently, we demonstrated that HIV-1 could directly impair the mucosal epithelial barrier in the FRT. This suggested that the HIV-1 envelope glycoprotein gp120 was being recognized by a membrane receptor on genital epithelial cells, leading to innate immune activation. In this study, we report that pattern-recognition receptors TLR2 and -4 bind to HIV-1 gp120 and trigger proinflammatory cytokine production via activation of NF-κB. The gp120-TLR interaction also required the presence of heparan sulfate (HS). Bead-binding assays showed that gp120 can bind to HS, TLR2, and TLR4, and studies in transfected HEK293 cells demonstrated that HS and TLR2 and -4 were necessary to mediate downstream signaling. Exposure to seminal plasma from HIV-1-infected and uninfected men with gp120 added to it induced a significant proinflammatory cytokine response from genital epithelial cells and disruption of tight junctions, indicating a role for gp120 in mucosal barrier disruption during HIV-1 heterosexual transmission. These studies provide, for the first time to our knowledge, a possible mechanism by which HIV-1 gp120 could directly initiate innate immune activation in the FRT during heterosexual transmission.