Landon G. vom Steeg ^1* Zheng Shen ¹ Jane Collins ¹ Mickey V. Patel ¹ Fiona D. Barr ¹ Daniel C. Hopkins ¹ Christina Ochsenbauer ² Charles R. Wira ^1*

• ¹ Geisel School of Medicine, Dartmouth College, Hanover, United States
• ² Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States

Epidemiological evidence suggests that post-menopausal women are more susceptible to HIV infection following sexual intercourse than are younger cohorts for reasons that remain unclear. Here, we evaluated how menopause-associated changes in CD4 + T cell numbers and subsets as well as HIV coreceptor expression, particularly CCR5, in the endometrium (EM), endocervix (CX), and ectocervix (ECX) may alter HIV infection susceptibility. Using a tissuespecific mixed cell infection model, we demonstrate that while no changes in CD14 + macrophage infection susceptibility were observed, CD4 + T cell HIV-1 infection frequency increases following menopause in the EM, but not CX nor ECX. Unexpectedly, the CD4 + T cell expression of two known correlates of HIV infection susceptibly, CCR5 and integrin-α4β7, increased following menopause across all three tissues despite only being associated with increased infection frequency in EM derived CD4 + T cells. After controlling for changes in the expression of either receptor, both CCR5 and α4β7 expressing CD4 + T cells isolated from the EM of post-menopausal women remained more susceptible to HIV-1 infection than those isolated from pre-menopausal women.and Treg frequency were also observed in the EM only following menopause, but did not correlate with increased infection frequency. Treatment of EM derived CD4 + T cells with 17β-estradiol (E2) prior to viral infection, reduced infection frequency independent of changes in either CCR5 or α4β7 expression frequency. Our results demonstrate that the susceptibility of EM derived CD4 + T cells to HIV-1 infection increases post menopause but is unlikely to be driven by increased expression frequency of either CCR5 or integrin-α4β7. These findings contribute to our understanding of how advanced age alters HIV infection risk which will become increasingly important as the human population continues to age.