Biological Consequences of HIV‐1 Interactions with Bacteria

Abstract

Microbiota dysbiosis due to bacterial vaginosis and other venereal diseases has been associated with an increased risk of HIV‐1 transmission and acquisition. The prevalent idea is that microbial perturbations compromise the mucosal integrity and create inflammatory conditions in the mucosa which results in the recruitment and stimulation of immune cells that harbor or are targeted by HIV‐1. However, it is also possible that HIV‐1 virions bind bacteria or bacterial products in a manner that impacts virus infectivity and transmissibility. This study aims to examine direct interactions between HIV‐1 and bacteria and to better understand the biological consequences of such interactions. Specifically, we focus on HIV‐1 interactions via glycan‐binding proteins, or lectins, expressed on bacterial surfaces. We investigated multiple lectins expressed by bacteria: FimH from uropathogenic Escherichia coli, MsL from vaginal and oral non‐pathogenic Lactobacillus plantarum, and three Siglec‐like adhesins (SLBR‐B, SLBR‐H, and SLBR‐N) from oral Streptococcus gordonii. FimH and MsL bind high mannose N‐glycans while the SLBRs bind different α‐2,3 sialylated O‐glycan structures. N‐ and O‐glycans have been identified on the surface of HIV‐1 on Env or host‐derived glycoproteins. Both FimH and MsL had no impact on HIV‐1 infectivity, while SLBR‐N increased HIV‐1 infection by up to 3‐fold. The observed effects of SLBR‐N were recapitulated by plant lectins specific for similar glycan epitopes, further validating these findings. We hypothesize that this enhancement effect could be due to accumulation of viral particles and/or bridging effects between the cell surface and HIV‐1 virions. Studies are in progress to decipher the molecular mechanisms for this enhancement effect. This data will help us better understand the importance of direct interactions between viral particles and bacteria in HIV‐1 acquisition.