The rapid replacement of M184V/I mutations is consistent with known fitness costs. The long-term persistence of NNRTI and protease inhibitor mutations suggests a risk for person-to-person propagation. Host and/or viral factors not accounted for by viral load or mutation class are likely influencing mutation replacement and warrant further study.

Use of antiretrovirals is widespread in Brazil, where more than 200,000 individuals are under treatment. Although general prevalence of primary antiretroviral resistance in Brazil is low, systematic sampling in large metropolitan areas has not being performed.The HIV Threshold Survey methodology (HIV-THS, WHO) was utilized, targeting Brazil's four major regions and selecting the six most populated state capitals: Sao Paulo, Rio de Janeiro, Salvador, Porto Alegre, Brasilia and Belem. We were able to sequence samples from 210 individuals with recent HIV diagnosis, 17 of them (8.1%) carrying HIV isolates with primary antiretroviral resistance mutations. Five, nine and four isolates showed mutations related to resistance to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs), respectively. Using HIV-THS, we could find an intermediate level of transmitted resistance (5% to 15%) in Belem/Brasilia, Sao Paulo and Rio de Janeiro. Lower level of transmitted resistance (<5%) were observed in the other areas. Despite the extensive antiretroviral exposure and high rates of virologic antiretroviral failure in Brazil, the general prevalence of primary resistance is still low. However, an intermediate level of primary resistance was found in the four major Brazilian cities, confirming the critical need to start larger sampling surveys to better define the risk factors associated with transmission of resistant HIV.

This study characterized HIV-1 among antiretroviral-naïve populations presenting recent infection (RI) or long-standing infection (LSI). Sera collected from January 1999 to December 2001 at an anonymous HIV testing site in Santos, Brazil, were submitted to serologic testing algorithm for recent HIV seroconversion (STARHS). The STARHS methodology uses a combination of a sensitive and a less sensitive version of an anti-HIV enzyme immunoassay (EIA), and specimens found to be positive on the sensitive EIA and negative on the less sensitive EIA are considered to represent RI. HIV-1 V3 and pol regions of those with RI and LSI were compared. Antiretroviral resistance was defined solely by genotypic analysis. Ninety samples were evaluated representing those taken from an original cohort of 345 individuals, for whom adequate samples were available. Of 90 HIV-positive individuals, 25 presented RI. Cumulatively, 36.8% of those with RI and 25% of those with LSI presented resistance to at least one antiretroviral class. In the pol and V3 regions, 47% and 53% of those with RI presented clade B viruses and B/F recombinant viruses, respectively, whereas 56.2%, 41.7%, and 2.1% of those with LSI harbored clades B, B/F, and clade C viruses, respectively. Primary resistance and the prevalence of B/F recombinants was high in this population. Monitoring HIV-1 genetic diversity is important for developing vaccines and treatment strategies.

Recombination is an important way to generate genetic diversity. Accumulation of HIV-1 full-length genomes in databases demonstrated that recombination is pervasive in viral strains collected globally. Recombinant forms achieving epidemiological relevance are termed circulating recombinant forms (CRFs). CRF12_BF was up to now the only CRF described in South America. The objective was to identify the first CRF in Brazil conducting full genome analysis of samples sharing the same partial genome recombinant structure. Ten samples obtained from individuals residing in Santos, Brazil, sharing the same recombination pattern based on partial genome sequence data, were selected from a larger group to undergo full length genome analysis. Near full length genomes were assembled from overlapping fragments. Mosaic genomes were evaluated by Bootscan, alignment inspection, and phylogenetic analysis using neighbor joining and maximum likelihood. Full genomes were also analyzed by split decomposition. We were able to identify five mosaic genomes. Two of these structures were represented by at least three samples derived from epidemiologically unlinked individuals. These structures were named CRF28_BF and CRF29_BF and are the second and third CRFs composed exclusively by subtypes B and F as well as the second and third CRFs encountered in South America. Other recombinant forms studied here resembled CRF28_BF and CRF29_BF. Our results suggest that a diverse population of related recombinants, including CRFs may play an important part in the Brazilian and South American epidemic.

BackgroundThe results of previous studies elsewhere have indicated that GB virus C (GBV-C) infection is frequent in patients infected with the human immunodeficiency virus type 1 (HIV-1) due to similar transmission routes of both viruses. The aim of this study was to determine the prevalence, incidence density and genotypic characteristics of GBV-C in this population.Methodology/Principal FindingsThe study population included 233 patients from a cohort primarily comprised of homosexual men recently infected with HIV-1 in São Paulo, Brazil. The presence of GBV-C RNA was determined in plasma samples by reverse transcriptase-nested polymerase chain reaction and quantified by real-time PCR. GBV-C genotypes were determined by direct sequencing. HIV viral load, CD4+ T lymphocyte and CD8+ T lymphocyte count were also tested in all patients. The overall prevalence of GBV-C infection was 0.23 (95% CI: 0.18 to 0.29) in the study group. There was no significant difference between patients with and without GBV-C infection and Glycoprotein E2 antibody presence regarding age, sex, HIV-1 viral load, CD4+ and CD8+T cell counts and treatment with antiretroviral drugs. An inverse correlation was observed between GBV-C and HIV-1 loads at enrollment and after one year. Also, a positive but not significant correlation was observed between GBV-C load and CD4+ T lymphocyte. Phylogenetic analysis of the GBV-C isolates revealed the presence of genotype 1 and genotype 2, these sub classified into subtype 2a and 2b.Conclusion/SignificanceGBV-C infection is common in recently HIV -1 infected patients in Sao Paulo, Brazil and the predominant genotype is 2b. This study provides the first report of the GBV-C prevalence at the time of diagnosis of HIV-1 and the incidence density of GBV-C infection in one year.