Background: Commercial sex workers are at high risk of HIV acquisition especially in countries
with high HIV prevalence. In Kenya, over 10% of all new HIV infections have been attributed to sex
workers and their clients. Unprotected sex results in exposure of the female genital tract to sexderived
antigens present in semen. Studies have reported a post-coital inflammatory response to these
antigens in animals and humans. In vivo, such inflammatory response leads to recruitment of
activated leukocytes including T cells from the peripheral circulation to the genital mucosa where
they can be infected by HIV. There is need to explore the impact of sex work on the activation of the
immune system and its role in the transmission of HIV. HIV-exposed seronegative (HESN) female
sex workers have been shown to have lower peripheral and mucosal immune activation than their
HIV-positive counterparts or HIV-uninfected low risk women. This reduced immune activation state
is thought to be protective against HIV infection. It is, therefore, thought that HESN sex workers are
able to down regulate sex-work-induced immune activation by a yet unknown mechanism.
Hypothesis: This study hypothesized that sex work results in exposure to very strong immune
stimulants which can drive systemic immune activation and that HESN women are able to down
regulate this sex work-driven immune activation more efficiently than HIV susceptible controls.
Objective: The study was designed to characterize the impact of sex work on activation and
phenotype of peripheral T cells, among female sex workers at the Pumwani Clinic, Nairobi.
Methods: Thirty female sex workers were recruited; 10 in each arm of HESN, HIV-positive, and
New Negatives. Blood samples were obtained from them when in active sex work, during a sex
break and upon return to sex work. PBMCs were extracted from the blood and stained with a 10-
colour monoclonal antibody panel for phenotypic (CD3, CD4, CD8, CD45RA, CD161), trafficking
(CCR7, CCR5) and activation markers (CD69, HLA-DR, CD95) of T cells. Expression of these
markers was then evaluated by flow cytometry. Statistical analyses were done to compare the
expression of T cell activation markers and memory phenotypes within each group during sex work,
sex break and upon return to sex work. The difference in response to interruption of sex work was
also assessed across groups.
Results: A reduction in CCR5 expression on CD8+ T cells in HIV-positive sex workers was
observed upon taking a break from sex work. A trend toward increased expression of CD161 on
10
CD4+ T cells was also observed in the HIV-positive. In New Negatives, we observed a trend towards
decreased naïve CD8+ T cells during the sex break and upon return to sex work. It was also observed
that there is no difference in the pattern of response to the interruption of sex work between HESN
female sex workers and their HIV-positive and New Negative counterparts. Overall, HIV-positive
women had higher frequency of effector memory T cells and CD95 expressing CD8+ T cells and a
lower frequency of naïve CD8+ T cells than HESN and New Negatives.
Conclusion: Sex work had a subtle effect on the expression of T cell activation markers and memory
phenotypes in the peripheral compartment. Interruption of commercial sexual activity had a greater
impact on T cell activation in HIV-positives. In HESN and New Negatives, sex work had no
discernible effect on peripheral immune activation. No apparent difference in the way HESN, HIVpositive
and New Negative sex workers respond to interruption of sex work was observed, which
may be due to various limitations of this study. Therefore, the impact of sex work could be confined
to the FGT mucosa and not be reflected in the peripheral compartment.