Correction: Estradiol Enhances CD4+ T-Cell Anti-Viral Immunity by Priming Vaginal DCs to Induce Th17 Responses via an IL-1-Dependent Pathway.

[This corrects the article DOI: 10.1371/journal.ppat.1005589.].

Estradiol Enhances CD4+ T-Cell Anti-Viral Immunity by Priming Vaginal DCs to Induce Th17 Responses via an IL-1-Dependent Pathway.

Clinical and experimental studies have shown that estradiol (E2) confers protection against HIV and other sexually transmitted infections. Here, we investigated the underlying mechanism. Better protection in E2-treated mice, immunized against genital HSV-2, coincided with earlier recruitment and higher proportions of Th1 and Th17 effector cells in the vagina post-challenge, compared to placebo-treated controls. Vaginal APCs isolated from E2-treated mice induced 10-fold higher Th17 and Th1 responses, compared to APCs from progesterone-treated, placebo-treated, and estradiol-receptor knockout mice in APC-T cell co-cultures. CD11c+ DCs in the vagina were the predominant APC population responsible for priming these Th17 responses, and a potent source of IL-6 and IL-1ß, important factors for Th17 differentiation. Th17 responses were abrogated in APC-T cell co-cultures containing IL-1ß KO, but not IL-6 KO vaginal DCs, showing that IL-1ß is a critical factor for Th17 induction in the genital tract. E2 treatment in vivo directly induced high expression of IL-1ß in vaginal DCs, and addition of IL-1ß restored Th17 induction by IL-1ß KO APCs in co-cultures. Finally, we examined the role of IL-17 in anti-HSV-2 memory T cell responses. IL-17 KO mice were more susceptible to intravaginal HSV-2 challenge, compared to WT controls, and vaginal DCs from these mice were defective at priming efficient Th1 responses in vitro, indicating that IL-17 is important for the generation of efficient anti-viral memory responses. We conclude that the genital mucosa has a unique microenvironment whereby E2 enhances CD4+ T cell anti-viral immunity by priming vaginal DCs to induce Th17 responses through an IL-1-dependent pathway.

Persistence of Suspected Probiotic Organisms in Preterm Infant Gut Microbiota Weeks After Probiotic Supplementation in the NICU.

Probiotics are becoming a prevalent supplement to prevent necrotizing enterocolitis in infants born preterm. However, little is known about the ability of these live bacterial supplements to colonize the gut or how they affect endogenous bacterial strains and the overall gut community. We capitalized on a natural experiment resulting from a policy change that introduced the use of probiotics to preterm infants in a single Neonatal Intensive Care Unit. We used amplicon sequence variants (ASVs) derived from the v3 region of the 16S rRNA gene to compare the prevalence and abundance of Bifidobacterium and Lactobacillus in the gut of preterm infants who were and were not exposed to a probiotic supplement in-hospital. Infants were followed to 5 months corrected age. In the probiotic-exposed infants, ASVs belonging to species of Bifidobacterium appeared at high relative abundance during probiotic supplementation and persisted for up to 5 months. In regression models that controlled for the confounding effects of age and antibiotic exposure, probiotic-exposed infants had a higher abundance of the suspected probiotic bifidobacteria than unexposed infants. Conversely, the relative abundance of Lactobacillus was similar between preterm groups over time. Lactobacillus abundance was inversely related to antibiotic exposure. Furthermore, the overall gut microbial community of the probiotic-exposed preterm infants at term corrected age clustered more closely to samples collected from 10-day old full-term infants than to samples from unexposed preterm infants at term age. In conclusion, routine in-hospital administration of probiotics to preterm infants resulted in the potential for colonization of the gut with probiotic organisms post-discharge and effects on the gut microbiome as a whole. Further research is needed to fully discriminate probiotic bacterial strains from endogenous strains and to explore their functional role in the gut microbiome and in infant health.

IL-17 Production by γδ+ T Cells Is Critical for Inducing Th17 Responses in the Female Genital Tract and Regulated by Estradiol and Microbiota.

IL-17 can be produced by adaptive immune cells such as Th17 cells and by immune cells that produce IL-17 without prior priming. This latter category, which we will refer to as "innate," includes innate cells such as NK cells and innate lymphoid cells and innate-like T cell populations such as NKT cells and γδ+ T cells. Studies in mucosal tissues have shown that the induction of Th17 immunity is amplified by innate IL-17 produced within those tissues. However, the role of innate IL-17 and its effect on Th17 induction in the female genital tract (FGT) is largely unknown. In this study, we characterize the primary source of IL-17-secreting vaginal cells and show that innate IL-17 plays a critical role in priming adaptive Th17 responses in the FGT. Under homeostatic conditions, γδ+ T cells were the predominant source of innate IL-17 in the murine FGT, and this population was modulated by both the sex hormone estradiol and the presence of commensal microbiota. Compared with wild-type C57BL/6 mice, vaginal APCs isolated from IL-17A-deficient (IL-17A-/- ) mice were severely impaired at priming Th17 responses in APC-T cell cocultures. Furthermore, the defect in Th17 induction in the absence of innate IL-17 was associated with impairment of IL-1ß production by vaginal CD11c+ dendritic cells. Overall, our study describes a novel role for IL-17 in the FGT and further demonstrates the importance of factors in the vaginal microenvironment that can influence adaptive immune responses.

Effects of Female Sex Hormones on Susceptibility to HSV-2 in Vaginal Cells Grown in Air-Liquid Interface.

The lower female reproductive tract (FRT) is comprised of the cervix and vagina, surfaces that are continuously exposed to a variety of commensal and pathogenic organisms. Sexually transmitted viruses, such as herpes simplex virus type 2 (HSV-2), have to traverse the mucosal epithelial lining of the FRT to establish infection. The majority of current culture systems that model the host-pathogen interactions in the mucosal epithelium have limitations in simulating physiological conditions as they employ a liquid-liquid interface (LLI), in which both apical and basolateral surfaces are submerged in growth medium. We designed the current study to simulate in vivo conditions by growing an immortalized vaginal epithelial cell line (Vk2/E6E7) in culture with an air-liquid interface (ALI) and examined the effects of female sex hormones on their growth, differentiation, and susceptibility to HSV-2 under these conditions, in comparison to LLI cultures. ALI conditions induced Vk2/E6E7 cells to grow into multi-layered cultures compared to the monolayers present in LLI conditions. Vk2 cells in ALI showed higher production of cytokeratin in the presence of estradiol (E2), compared to cells grown in progesterone (P4). Cells grown under ALI conditions were exposed to HSV-2-green fluorescent protein (GFP) and the highest infection and replication was observed in the presence of P4. Altogether, this study suggests that ALI cultures more closely simulate the in vivo conditions of the FRT compared to the conventional LLI cultures. Furthermore, under these conditions P4 was found to confer higher susceptibility to HSV-2 infection in vaginal cells. The vaginal ALI culture system offers a better alternative to study host-pathogen interactions.

The anti-inflammatory activity of curcumin protects the genital mucosal epithelial barrier from disruption and blocks replication of HIV-1 and HSV-2.

Inflammation is a known mechanism that facilitates HIV acquisition and the spread of infection. In this study, we evaluated whether curcumin, a potent and safe anti-inflammatory compound, could be used to abrogate inflammatory processes that facilitate HIV-1 acquisition in the female genital tract (FGT) and contribute to HIV amplification. Primary, human genital epithelial cells (GECs) were pretreated with curcumin and exposed to HIV-1 or HIV glycoprotein 120 (gp120), both of which have been shown to disrupt epithelial tight junction proteins, including ZO-1 and occludin. Pre-treatment with curcumin prevented disruption of the mucosal barrier by maintaining ZO-1 and occludin expression and maintained trans-epithelial electric resistance across the genital epithelium. Curcumin pre-treatment also abrogated the gp120-mediated upregulation of the proinflammatory cytokines tumor necrosis factor-α and interleukin (IL)-6, which mediate barrier disruption, as well as the chemokines IL-8, RANTES and interferon gamma-induced protein-10 (IP-10), which are capable of recruiting HIV target cells to the FGT. GECs treated with curcumin and exposed to the sexually transmitted co-infecting microbes HSV-1, HSV-2 and Neisseria gonorrhoeae were unable to elicit innate inflammatory responses that indirectly induced activation of the HIV promoter and curcumin blocked Toll-like receptor (TLR)-mediated induction of HIV replication in chronically infected T-cells. Finally, curcumin treatment resulted in significantly decreased HIV-1 and HSV-2 replication in chronically infected T-cells and primary GECs, respectively. All together, our results suggest that the use of anti-inflammatory compounds such as curcumin may offer a viable alternative for the prevention and/or control of HIV replication in the FGT.