Poster Presentation 14th Lorne Infection and Immunity 2024

A key Lactobacillus metabolite reduces HIV internalisation and migration through the cervicovaginal epithelial barrier (#153)

Brianna Jesaveluk 1 2 , David Delgado Diaz 1 , Anna Hearps 1 3 , Gilda Tachedjian 1 2 4
  1. Disease Elimination Program and Life Sciences Discipline, Burnet Institute, Melbourne, VIC, Australia
  2. Department of Microbiology, Monash University, Clayton, VIC, Australia
  3. Department of Infectious Diseases, Monash University, Clayton, VIC, Australia
  4. Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia

Introduction: Young women in sub-Saharan Africa are disproportionately affected by HIV. A Lactobacillus-dominated cervicovaginal microbiome reduces the risk of HIV acquisition by decreasing genital inflammation, which disrupts the female reproductive tract (FRT) epithelial barrier and enables the virus to infect target cells in the submucosa. We have discovered that lactic acid (LA), a key metabolite of optimal Lactobacillus spp. strengthens the cervicovaginal epithelial barrier. However, LA’s ability to inhibit passage of cell-free virus in between epithelial cells (transmigration) or HIV uptake (internalisation) and transcellular migration through epithelial cells (transcytosis) via LFA/ICAM-1 interactions are unknown.

Methods: Immortalised ectocervical (Ect1) and vaginal (VK2) cell lines were cultured in a transwell system, treated apically for 1h with 0.3% LA (pH 3.9), lactate (pH 7.0), or acidified media (pH 3.9, HCl adjusted). At 24h post-treatment, cells were thoroughly washed, and HIV (HIVBa-L, 10ng p24) was added apically for 24h, after which p24 was quantified in basolateral supernatant and cell lysates. Antibodies against ICAM-1 and LFA-1 were added prior to HIV addition to block binding.

Results: LA treatment (pH 3.9), but not HCl or lactate (neutral pH) reduced HIV migration to the basolateral supernatant by 72±5.8% in Ect1 (mean ± SEM) and 89±6.8% in VK2 cells relative to untreated cells and reduced internalised virus in cell lysates by 49±7.3% in Ect1 and 67±10% in VK2 cells (p<0.05, n=5-11). This reduction was abrogated in the presence of antibodies to ICAM-1 and LFA-1. LA treatment reduced ICAM-1 expression in the presence of inflammatory mediators, indicating a potential protective mechanism for LA against HIV.

Conclusions: This study is the first to demonstrate a direct effect of LA on HIV migration through epithelial cells and provides novel insights into its potential mechanism of action.  These findings have implications for developing novel strategies to prevent HIV transmission in women.