Mucosal transmission accounts for significant proportion of new HIV infections, and women are at particular risk of infection with HIV. Further, chronic inflammation within the female genital tract caused by bacterial vaginosis (BV) and other sexually transmitted infections (STIs) is associated with increased risk of HIV acquisition; thus, there is a great need to enhance protection within the female reproductive tract (FRT). Mucus at mucosal barriers provides protection to the underlying epithelium, and the heavily glycosylated mucin proteins within the mucus have a critical role in mucosal protection. Both soluble and membrane-tethered mucin proteins contribute to protection by capturing and trapping pathogens in the mucus. Preliminary data from our laboratory indicate that antibodies (Abs) isolated from HIV+ patients bind specifically to mucin 16 (MUC16), a mucin present within the FRT. Importantly, binding of Abs to MUC16 resulted in both trapping of HIV, suggesting that Abs may help prevent HIV infection by locking virus in MUC16. Moreover, Ab/MUC16 interactions resulted in rapid release of MUC16 from the surface of epithelial cells, further suggesting that beyond trapping, this Ab/MUC16 interaction may help slough and rapidly clear HIV virions from the mucosa in an effort to protect the vulnerable epithelial border. However, as MUC16 ectodomain release is regulated in part by inflammation and inflammatory cytokines, chronic inflammation in the FRT caused by BV and STIs may affect trapping of HIV through spontaneous release of MUC16 or decreased binding of Abs. We believe that by characterizing the mechanism by which Ab/MUC16 interactions occur, and how these may change under inflammatory conditions, will provide critical information to guide the development of vaccine strategies able to harness the antiviral activity of mucus. The goal of this proposal is to define the mechanism underlying the potentially protective role of MUC16 against HIV by defining the specific characteristics of MUC16 binding Abs, the mechanism by which epithelial cells sense Ab-binding, and finally the role of inflammation on modulating the protective activity of Ab/MUC16 interactions.
Aim 1 will define the mechanism of MUC16 ectodomain release following binding of HIV-Ab complexes by determining composition and size of HIV-Ab complexes that contribute to MUC16 ectodomain release. Further, we will define antiviral signaling pathways initiated following HIV-Ab binding to MUC16 to define the signal that promotes release and potential cascade that may trigger the activation of a broader antiviral immune response.
Aim 2 will determine the impact of inflammation on HIV trapping by MUC16 by determining if the inflammatory profile associated with increased risk of HIV infection induces spontaneous MUC16 release, alterations in MUC16 expression or glycosylation potentially contributing to reduced MUC16 trapping of HIV and therefore reduced protection against HIV. Ultimately, we believe that defining the mechanism of MUC16/Ab trapping of HIV, and how it is altered by inflammation, will allow for the design of vaccines that may effectively harness the anti-microbial and antiviral properties of mucus.
Transmission of HIV through mucosal barriers is a significant cause of HIV infection, and disproportionately affects women. The goal of this proposal is to define mechanisms of mucosal protection against HIV as an approach to reducing HIV transmission across mucosal barriers.
