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256 Survival in HIV-1 and HIV-2 Dual Infections in West Africa: Implications for an Effective HIV Vaccine
S. A. Alabi*1, T. Blanchard1, J. Shabbar2, S. Sabally1, T. Corrah1, M. Schim van der Loeff1, K. Ariyoshi1, N, Berry4, and H. Whittle1
1MRC Labs., Banjul, Gambia; 2LSTMH, London, UK; 3NIH, Tokyo, Japan; and 4NIBSC, London, UK
Background: HIV-1 and HIV-2 dual infection is increasing in West Africa, with implications for the development and implementation of effective HIV vaccines. Furthermore, the effect of HIV dual infection on pathogenesis and how this might be related to patients' survival remain unknown. Since previous studies have shown plasma viraemia to be an excellent maker of prognosis in HIV-infected persons, we compare baseline plasma viraemia with survival in patients infected with HIV-1, HIV-2, or both in our clinic.
Methods: Baseline plasma viraemia (RNA copies/ml) was measured in a total of 256 (119 HIV-1 and 137 HIV-2) singly infected and 81 dually infected individuals, using an in-house quantitative RT-PCR assay. Percentage CD4 cell count (CD4%) was measured by FACScan. Subjects were part of a clinical cohort of HIV-infected patients seen at the MRC Clinic, Fajara, The Gambia. They were enrolled into the study between 1991 and 1997, and followed-up through 2000. Main outcome variable was survival after 3(7 years of follow-up.
Results: HIV-1 plasma viraemia among singly infected individuals were similar to that in dually infected (p = 0.5), and similar trend for HIV-2 (p = 0.7). Mean CD4% was significantly lower in dual infections than in either HIV-1 or HIV-2-infected subjects. Death rates of dually infected subjects were significantly higher than that in HIV-2 but similar to that in HIV-1 with hazard ratios (95% CI) of 1.54 (1.08, 2.19; p = 0.02) and 1.25 (0.88, 1.77; p = 0.2), respectively. Both CD4% and plasma viraemia were associated with survival.
Conclusions: In this study, dually infected individuals had the worst survival outcome compared with those infected with either HIV-1 or HIV-2, even after controlling for virus load and CD4%. An effective HIV vaccine may have to offer broad protection against both HIV-1 and HIV-2.
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