Seroconversion in Kenyan sex-workers linked with reduced HIV-specific immune response

HIV-specific CD8+ T cells play an important role in controlling viraemia, the authors explain, but maintenance of such a circulating cytotoxic T lymphocyte (CTL) presence may require ongoing antigenic stimulus.

Dr Rupert Kaul, and colleagues, from the University of Nairobi in Kenya, examined 11 late seroconverters, who had previously met criteria for HIV-1 resistance, for evidence of HIV-1 – specific CD8+ responses. Dr Kaul’s findings follow the preliminary description of 6 highly exposed, previously uninfected sex workers who had seroconverted after they stopped continual exposure to HIV-1. Pre-seroconversion data were available for 6 of the 11 women. Four of the 6 women had HIV-1 – specific CTL responses ranging from 5 months to 18 months before seroconversion, the authors report.

Seroconversion was not associated with contraceptive method or occurrence of sexually transmitted diseases over the preceding year, the researchers note, but overall reduction in sex workÑtaking a break or reducing the number of daily clientsÑwas significantly associated with late seroconversion. Only 2 of the 11 late seroconverters had not experienced a decrease in sex work. While there was no decrease in the number of daily clients, 1 of the 2 women reported increased condom use in the year preceding seroconversion, followed by decreased condom use at the time of seroconversion.

In 6 of 7 women who took at least a 2-month break from sex work, HIV-1 – specific responses were no longer seen in peripheral blood mononuclear cells, the report indicates, and 3 of 4 women who retired from sex work experienced a loss of such responses. Three such women who returned to sex work redeveloped HIV-1 – specific responses after a lag of 12.4 months on average, according to the results.

“The association of HIV-1 seroconversion with reduced sex work seems initially counterintuitive, but it might be compatible with a loss or diminution of HIV-1 – specific CTL in the absence of ongoing antigenic stimulation,” the authors conclude.