15th International AIDS Conference Bangkok, Thailand - July 11-16, 2004

Int Conf AIDS 2004 Jul 11-16; 15:(abstract no. ThOrA1361)

Sankale JL, Hamel DJ, Thakore S, Gueye-Ndiaye A, Eisen G, Olaleye DO, Odaibo G, Langevin S, Mani I, Essex M, Mboup S, Kanki P
Harvard University, Boston, MA, United States

BACKGROUND: CRF02_AG is the most common form of HIV-1 in West and Central Africa. It is important to determine the emergence of this recombinant virus from its parental subtypes (A and G) and the rate of diversification in the population since its emergence.

METHODS: We sequenced the C2-V3 region of the envelope glycoprotein from 154 individuals infected by CRF02_AG in Senegal and 12 individuals recently infected in Nigeria. Additional sequencing of the gp120 and the gag p17/p24 was performed on a subset of individuals. Phylogenetic analysis was performed using ClustalX and Phylip3.6. Ancestral sequences reconstruction for the CRF02 virus were implemented in PAUP*4.0b10 and MrBayes2.01. Distances were calculated using MEGA2.0 and Phylip3.6.

RESULTS: We used data from our sero-incident cohort in Senegal where we have evaluated the relative importance and the temporal distribution of various subtypes between 1987 and 2003 to do a first calibration of the rate of diversification of the virus overtime. Additionally sequences from the literature and current sequences obtained from Senegal and Nigeria were further used in the calibration. Our data indicate that CRF02, as a recombinant virus, may have emerged as recently as the 70s-early 80s. Epidemiological data from West Africa support such findings. The diversification rate of CRF02, in the region sequenced, is on the order of 0.7 to 0.9% per year, in line with our previous findings for the subtype A radiation in West Africa. Reconstructed ancestral sequences, consensus sequences and currently circulating strains were compared to further assess viral evolution.

CONCLUSIONS: In West and West Central Africa, the predominance of CRF02_AG/IbNG suggests that this virus has an advantage with respect to transmission. Design of an efficient HIV vaccine for CRF02_AG/IbNG is an utmost priority. Reconstruction of ancestral sequences and careful analysis of diversification will help in the choice of an optimal immunogen.

040711
ThOrA1361

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