C. genital tract mucosa is thus the primary site of HIV replication, and discerning the nature of HIV-specific immune responses in this compartment is crucial. The role of the innate immune system at the mucosal level in exposed seronegative individuals and other HIV controllers remains largely unexplored. This understanding can provide valuable insights to improve vaccine design. We investigated mucosal T follicular helper (Tfh) cells, CXCR5+ CD8+ T cells, natural killer (NK) cells subsets, soluble immune markers, and microbiome diversity in HIV-exposed seronegative (HESN) women. We found a significantly higher level of mucosal CXCR5+ CD8+ T cells, CD4+ Tfh cells, activated NK cell subsets, and antiviral immune cell mediators in HESN women. We also found a higher abundance of spp., microbiome dysbiosis, and decreased levels of inflammatory markers to be associated with reduced susceptibility to HIV infection. Our findings indicate that increased distribution of mucosal NK cells, CXCR5+ CD8+ T cells, Tfh cells, and soluble markers in HIV controllers with a highly diverse cervicovaginal microbiome could contribute effectively to protection against HIV infection. Overall, our findings imply that future vaccine design should emphasize inducing these highly functional cell types at the mucosal sites. KEYWORDS: cytobrush, cervicovaginal lavage, HESN, NK cells, TSCM cells, Tfh cells, CXCR5+ CD8+ cells, B cells, CBA, cervicovaginal microbiota, memory B cells INTRODUCTION Mucosal surfaces are primarily protected by innate immune mechanisms, but adaptive immune mechanisms also operate (1). The natural barriers present in the female genital tract (FGT) are insufficient to protect against all infections, although the FGT is a site of immunological balance (2). Innate immune cells play a vital role in the nonspecific destruction of foreign organisms. Natural killer (NK) cells recognize infected host cells via surface receptors and use various mechanisms to kill them (3). Increased NK cell activity is reflected by the higher cytotoxic capacity of NK cells and increased production of AZD1152 NK cell-specific cytokines and chemokines associated with control of infection (4,C6). Perturbations in the NK cell receptor repertoire, including cells expressing natural cytotoxicity receptors (NCRs) and killer inhibitory receptors (KIRs), have been reported in human immunodeficiency virus (HIV) and other viral infections (7). Elevated NK cell activity has been correlated with protection against infection in several high-risk cohorts of HIV-exposed seronegative (HESN) subjects, including intravenous drug users, HIV-1-discordant couples, and perinatally exposed infants (8). Studying the role of KIR- and NCR-expressing NK cell subsets may help us understand NK cell-mediated control of early HIV infection. Neutralization has long been viewed as the primary effector function of humoral immunity and is considered to be the primary correlate of antibody-mediated protection in HIV infection (9). However, the role of mucosal antibodies in HIV infection continues to be controversial (10). Soderlund et al. (2007) detected HIV-1-specific neutralizing IgA antibodies in some infected persons, but these antibodies were unable to block the transfer of the virus from dendritic cells (DC) to susceptible target cells (11). However, Nag et al. found that HIV-1 gp120-specific IgGs in the cervical fluid could mediate antibody-dependent cellular cytotoxicity (ADCC) activity and that their levels correlated inversely with genital viral load (12). Antibody responses are dependent mainly on CD4+ T cell help, and the significant subset that provides this help is the T follicular helper (Tfh) cell. These cells help in B cell affinity maturation, isotype switching, and the development of long-lived plasma cells (13). A high frequency of peripheral blood Tfh cells has been reported to correlate with high titers of broadly neutralizing antibodies (bNAb) and reduced viral load in HIV-infected individuals (14). Similarly, infiltration of CD8+ T cells into the B cell follicle AZD1152 area has been reported in HIV-infected individuals. More recently, Shen et al. demonstrated that CXCR5+ CD8+ T cells residing in the germinal center follicular area play an essential Rabbit Polyclonal to DDX3Y role in neutralizing virus-infected target cells (15). However, the role of CXCR5+ CD8+ T cells or Tfh cells in disease control in highly AZD1152 exposed uninfected individuals and the correlation of these cell types with HIV-specific antibody titers is yet to AZD1152 be assessed. The cervicovaginal microbiome is a complex ecosystem with a preponderance of spp. Vaginal lactobacilli prevent.