To determine if healthy, young women in sub-Saharan Africa have a more activated immune milieu in the genital tract (i.e. activated CD4+ T-cells) than a similar population in the US.
Cross-sectional study nested in a phase 1 microbicide trial.
Cervical cytobrushes were collected from 18–24 year old women in San Francisco, CA (n=18) and Kisumu, Kenya (n=36) at enrollment into a phase 1 microbicide trial. All participants tested negative for HIV, HSV-2, gonorrhea, chlamydia and trichomonas, and had abstained from sex for at least seven days prior to enrollment. Cryopreserved T-cell populations were assayed by flow cytometry in a central laboratory. SLPI levels were assayed in cervicovaginal lavage samples. The Wilcoxon rank-sum test was used to compare immune parameters between sites.
The total number of endocervical CD4+ T-cells was slightly higher in San Francisco, but participants from Kisumu had a substantially higher number and proportion of CD4+ T-cells expressing the early activation marker CD69, with and without the HIV-coreceptor CCR5, and a greater proportion of activated CD8+ T-cells. Median [interquartile] genital levels of SLPI were lower in participants from Kisumu compared to those from San Francisco (190 pg/mL [96, 519] vs. 474 pg/mL [206, 817]; p<0.03).
Activated mucosal T-cells were increased in the genital tract of young, STI/HIV-free Kenyan women, independent of common genital co-infections, and SLPI levels were reduced. The cause of these mucosal immune differences is not known, but could partly explain the high HIV incidence in young women from sub-Saharan Africa.
Keywords: HIV transmission, mucosal immunology, female genital tract, sub-Saharan Africa, CD4+ T-cells, SLPI