Estimation of the year of introduction of subtype-F HIV in America that

D. DILERNIA; L.R. JONES; M. GOMEZ-CARRILLO; H. SALOMON

Ciudad del Cabo

Conferencia; 5TH IAS Conference on HIV Pathogenesis , Treatment and Prevention; 2009

International AIDS Society (IAS) in partnership with South African registered not for profit organization Dira Sengwe

Background: In South America, recombinant strains between the subytpes B and F circulate in a similar proportion as subtype B strains. However, a very low proportion of subtype-F strains were found to circulate in the region. In the present study by using phylogenetic approaches and Markov-modeling of the natural course of HIV-infection we figured out the origin of the HIV-BF epidemic in South America.In South America, recombinant strains between the subytpes B and F circulate in a similar proportion as subtype B strains. However, a very low proportion of subtype-F strains were found to circulate in the region. In the present study by using phylogenetic approaches and Markov-modeling of the natural course of HIV-infection we figured out the origin of the HIV-BF epidemic in South America. Methods: A data set of 90 complete genomes and 169 partial sequences of gag gene of BF-recombinant HIV strains was analyzed. The phylogenetic relationships were reconstructed by using the maximum parsimony method for large data set analysis with TNT. The TMRCAs were estimated by using the Bayesian approach as implemented in BEAST v1.4.8. The time to disease progression was estimated with a time-dependent Markov model of infection, progression and survival.A data set of 90 complete genomes and 169 partial sequences of gag gene of BF-recombinant HIV strains was analyzed. The phylogenetic relationships were reconstructed by using the maximum parsimony method for large data set analysis with TNT. The TMRCAs were estimated by using the Bayesian approach as implemented in BEAST v1.4.8. The time to disease progression was estimated with a time-dependent Markov model of infection, progression and survival. Results: The analysis of the F-regions of BF recombinants showed a monophyletic origin with an estimated TMRCA for the South American strains at 1971.6 (95%HPD 1962.9-1978.7). The same analysis over the Bregions showed also a monophyletic origin with an estimated TMRCA at 1966.7 (95%HPD 1948.7-1980.3). By using the probability density function for the TMRCA as input for the Markov Model we estimated the first case of AIDS with a BF-recombinant strain to have occurred around 1981 (q25:1978; q75:1985). The analysis of the F-regions of BF recombinants showed a monophyletic origin with an estimated TMRCA for the South American strains at 1971.6 (95%HPD 1962.9-1978.7). The same analysis over the Bregions showed also a monophyletic origin with an estimated TMRCA at 1966.7 (95%HPD 1948.7-1980.3). By using the probability density function for the TMRCA as input for the Markov Model we estimated the first case of AIDS with a BF-recombinant strain to have occurred around 1981 (q25:1978; q75:1985). Conclusions: The accordance of the estimated TMRCA for the American subtype-F strains and the TMRCA of the subtype-B strain that lead to the BF-recombinant strains suggest that an event of recombination occurred in the very first years of the arrival of subtype F to America. This could explain the low proportions of subtype-F strains circulating in the region. Our estimations are also consistent with the fact that the first cases of AIDS started to be detected at the beginning of the 1980´s.The accordance of the estimated TMRCA for the American subtype-F strains and the TMRCA of the subtype-B strain that lead to the BF-recombinant strains suggest that an event of recombination occurred in the very first years of the arrival of subtype F to America. This could explain the low proportions of subtype-F strains circulating in the region. Our estimations are also consistent with the fact that the first cases of AIDS started to be detected at the beginning of the 1980´s.