17th International AIDS Conference Mexico City, Mexico - August 13 - 18, 2008

TEMPORAL TRENDS AND EVOLUTIONARY HISTORY OF HIV-1 CRF31_BC IN PORTO ALEGRE, BRAZIL FROM 1998 TO 2006

Int Conf AIDS. 2008 Aug 13-18;17 Abstract No. MOAA0203

M. Guimarães ¹, C. Passaes¹, G. Bello¹, R. Lorete¹, S. Almeida², R. Medeiros², P.R. Alencastro³, M. Morgado^1
1Oswaldo Cruz Institue, Rio de Janeiro, Brazil, ²Fundação Estadual de Produção e Pesquisa em Saúde, Centro de Desenvolvimento Científico e Tecnológico, Porto Alegre, Brazil, ³Hospital Sanatório Partenon, Porto Alegre, Brazil

BACKGROUND: CRF31_BC was recently described to circulate at a high frequency in the state of Rio Grande do Sul, Brazil, nevertheless none study concerning an extensive number of temporal samples was performed until now.

METHODS: In order to investigate a temporal trend of CRF31_BC and URF_BC in South Brazil, we screened 84 HIV-1 samples from Porto Alegre, Brazil isolated between 1998 and 2006, previously typed as subtype C in pol region. Three genomic regions high related to recombinant events were investigated (pr/rt, int, env) by direct sequencing of PBMC-associated proviral DNA. Alignment and phylogenetic trees (NJ) were constructed using Mega 3.1. Simplot program was used to verify intragenic recombination and breakpoints. Eighteen samples sequenced at both env and pol regions were used to estimate the time of the most recent common ancestor (Tmrca, years) of CRF31_BF using BEAST v.1.5.

RESULTS: Thirty out of 84 (35.7%) samples analyzed were recombinants. Twenty-four (28.6%) samples could be confirmed as CRF31_BC (CRF31pol/Cint/Cenv) and eight (9.5%) samples were identified as URF_BC (four CBpol/Cint/Cenv, one CBpol/CBint/CBenv, one CBpol/Cint/NDenv, two Cpol/CBint/Cenv, and one CRF31pol/CBint/Cenv). The frequency of CRF31_BC in heterosexual population varied from 50% in 1998 to 14.3% in 2005-2006. Phylogenetic analysis revealed that CRF31_BC strains form a monophyletic group in pol gene; however, were intermixed among pure subtype C sequences in the other regions analyzed. The Tmrca of CRF31_BF was estimated to be around 1986 (1981-1991) and 1983 (1974-1991) using env and pol dataset, respectively.

CONCLUSIONS: These results suggest that CRF31_BC emerged around middle 1980s, immediately after subtype C introduction in South Brazil, which could explain the high prevalence of this form and the intermixing with pure subtype C sequences at non-recombinant regions (int/env). These results also suggest a trend of diminishing of CRF31_BC in a heterosexual population in South Brazil over time.

Financial support: FIOCRUZ/FAPERJ

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2008-08-13
MOAA0203

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