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Late Seroconversion in HIV ‘Resistant’ Nairobi Prostitutes Is Associated with a Preceding Decrease in HIV Exposure R. KAUL*1,2, J. KIMANI1, T. DONG2, H. YANG2, J. BWAYO1, K. MACDONALD3, F. PLUMMER4, and S. ROWLAND-JONES2.
1Univ. of Nairobi, Kenya; 2Inst. of Molecular Med., Oxford, UK; 3Univ. of Toronto, Canada; and 4Univ. of Manitoba, Winnipeg, Canada Background: Despite intense HIV-1 exposure, a minority of Nairobi prostitutes remain HIV uninfected, as determined by serology and PCR, and have been defined as HIV resistant. Since 1996 six of these women have seroconverted, prompting this immuno-epidemiologic investigation.
Methods: Pre-conversion PBMC were tested for HIV-specific CTL using an interferon-g ELISpot. Relevant CTL epitopes were cloned from infecting viral isolates, and sequenced. Epidemiologic associations of seroconversion were examined in seroconverters and persistently uninfected prostitute controls, matched for time of clinic enrollment.
Results: CTL recognizing 1–2 HIV epitopes were present in 4/6 cases, from 5–18 months prior to seroconversion. Epitope sequence analysis showed no evidence of viral escape mutations. All seroconverters either had taken a recent break from sex work of >2 months, or had reduced their number of daily clients, but this was not the case for persistently uninfected controls (P=0.006).
Conclusion: Late seroconversion in HIV ‘resistant’ prostitutes may occur despite pre-existing HIV-specific CTL. Seroconversion occurs in the absence of viral escape mutations and may be related to waning of CTL via reduced antigenic exposure. This finding has significant implications for HIV vaccine design and implementation strategies.
Key Words: Cytotoxic T-Lymphocytes, HIV Resistance, Seroconversion
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