Estradiol inhibits HIV-1_BaL infection and induces CFL1 expression in peripheral blood mononuclear cells and endocervical mucosa

An inhibitory effect of estradiol (E2) on HIV-1 infection was suggested by several reports. We previously identified increased gene expression of actin-binding protein cofilin 1 (CFL1) in endocervix in the E2-dominated proliferative phase of the menstrual cycle. Actin cytoskeleton has an integral role in establishing and spreading HIV-1 infection. Herein, we studied in vitro effects of E2 on HIV-1 infection and on CFL1 expression to gain insight into the mechanism of HIV-1 inhibition by E2. E2 dose-dependently inhibited HIV-1_BaL infection in peripheral blood mononuclear cells (PBMCs) and endocervix. In PBMCs and endocervix, E2 increased protein expression of total CFL1 and phosphorylated CFL1 (pCFL1) and pCFL1/CFL1 ratios. LIMKi3, a LIM kinase 1 and 2 inhibitor, abrogated the phenotype and restored infection in both PBMCs and endocervix; inhibited E2-induced expression of total CFL1, pCFL1; and decreased pCFL1/CFL1 ratios. Knockdown of CFL1 in PBMCs also abrogated the phenotype and partially restored infection. Additional analysis of soluble mediators revealed decreased concentrations of pro-inflammatory chemokines CXCL10 and CCL5 in infected tissues incubated with E2. Our results suggest a link between E2-mediated anti-HIV-1 activity and expression of CFL1 in PBMCs and endocervical mucosa. The data support exploration of cytoskeletal signaling pathway targets for the development of prevention strategies against HIV-1.