Around have of those infected by HIV around the world are women.
Commercial sex workers, who are seen to have a higher risk of getting the virus, have been studied for a long time in order to find ways of decreasing the number of HIV infections. There are some areas in the world where, even though there is a high prevalence of HIV, continued sexual activity, and less condom use, some of the female
sex workers are still devoid of the virus. However, the reason as to why these women have continued resistance to HIV is still not known, as these women do not show any of the known immune responses against HIV.
In a study published in the journal Mucosal Immunology by researchers from The Wistar Institute, data
revealed that the continued exposure of sex workers to semen causes changes in the microenvironment
of the cervix and vagina in such a way that HIV resistance is increased. This data may be used in the future
to develop strategies to prevent the transmission of HIV.
Luis J. Montaner, DVM, DPhil, who is the Herbert Kean, MD Family Professor at the Wistar Institute and
the lead author of the study, says that creating the link between sex work, changes in the immune system
and semen exposure gives us a good look as to whether the continued exposure to semen and its effect
on the female reproductive tract actually contributes to HIV resistance and is the reason why some sex
workers are still uninfected even if they don't use condoms. It also clearly indicates that women are
equipped to activate mechanisms of resistance due to sex itself, which we did not expect to find at the
start of this research, he adds.
The study was in collaboration with researchers from the University of Puerto Rico Maternal Infant Studies
Center and analyzed a set of female sex workers in San Juan who were not infected with the virus,
comparing them to women who had self-reported low semen exposure in the same area. The median age
was 35.50 years old, and most were working in the industry for a minimum of three years. Both groups
were also compared on the basis of unprotected sex, whether or not they used contraceptives and what
types the used. Sex workers who had other infections such as syphilis or chlamydia were excluded from
Three mechanisms were formulated by the researchers that may explain the resistance of the sex workers
to HIV. The first one was the observed lower rates of immune activation in the blood and mucosal tissue
of these women. This is very important, as HIV needs an active immune system to thrive and reproduce.
Second, these women had high levels of interferon e, which is a signaling protein that serves to protect
the female reproductive tract from bacterial and viral infections. Lastly, factors such as CD4 and
Nucleoporin 153, which are critical for HIV to survive, had low expression levels.
Carmen D. Zorrilla, MD, professor of obstetrics and gynecology at the University of Puerto Rico, who is
also one of the authors of the study, states that this work could provide insight into why cohorts of
women at risk recruited for preventive trials in the United States have demonstrated lower sero-
conversion rates than expected on community prevalence.