Resistance to HIV-1 infection among persistently seronegative prostitutes in Nairobi, Kenya
Fowke, K.R.; Nagelkerke, N.J.; Kimani, J.; Simonsen, J.N.; Anzala, A.O.; Bwayo, J.J.; MacDonald, K.S.; Ngugi, E.N.; Plummer, F.A.
Lancet 348(9038): 1347-1351
1996
ISSN/ISBN: 0140-6736 PMID: 8918278 DOI: 10.1016/s0140-6736(95)12269-2Document Number: 301379
A cohort study conducted in 1985-94 among 424 prostitutes from Nairobi, Kenya, who were initially human immunodeficiency virus (HIV)-1 seronegative, tended to provide support for the observation that some individuals in highly exposed populations may be resistant to infection. During the 10-year study period, 239 of these women seroconverted. The overall HIV-1 incidence was 42/100 person-years. After the first 2 years of follow up, in which the majority of seroconversions occurred, HIV-1 prevalence reached a plateau and then began a steep decline. To determine whether the risk of HIV-1 infection declined over time as a result of the selection of resistance, incidence rates among women with less than 3 years' versus more than 3 years' duration of prostitution were compared for 1989-93. An increasing protective effect for each seronegative year of exposure was observed. The estimated cumulative protective effect for women practicing prostitution from 1984-93 and remaining seronegative, compared to women who entered prostitution in 1994, was over 100-fold. To rule out the possibility that the decrease in seroconversion with duration of exposure reflected differences in sexual behavior or immunity to sexually transmitted diseases that facilitate HIV transmission, Cox proportional hazards modelling was performed. The weighted duration of prostitution was independently associated with a decreased risk of seroconversion. Each weighted year of exposure resulted in a 1.2-fold decrease in risk. Women who seroconverted were more likely to report 1 or more regular partners and to use condoms with these partners than their counterparts who remained seronegative. Elucidation of the protective mechanisms and the factors mediating the development of immunity against HIV-1 could be important to HIV-1 vaccine research.
Document emailed within 0-6 h
