Viruses Previously Classified as CRF146BC, a Circulating Recombinant Form of HIV-1 Recently Reported in Brazil, Represent Different Recombinant Forms, One of Which Is Circulating in Spain

Circulating recombinant forms (CRFs) are important components of the HIV-1 pandemic. Previous studies have reported the propagation of diverse HIV-1 CRFs of South American origin in Europe. Here, through protease-reverse transcriptase (Pr-RT) and integrase sequence analyses, we identify a Spanish cluster (BC3) branching with a Brazilian virus (10BRRJ009) previously classified as CRF146BC. In Pr-RT, BC3 comprised 14 viruses and was nested within a larger cluster, comprising 22 Brazilian viruses and 1 Spanish virus branching outside of BC3. Near full-length genome analyses of five BC3 viruses revealed mosaic structures identical to 10BRRJ009, with two breakpoints delimiting a ~0. 3 kb subtype B fragment within an otherwise subtype C genome. Two other Brazilian viruses previously classified as CRF146BC (10BRRJ039 and 01BRRGS69) had one and two additional short subtype B fragments, respectively, and failed to group with the 10BRRJ009/BC3 cluster in subtype C fragments. Based on these results, we contend that 10BRRJ009 and BC3 viruses, but not 10BRRJ039 and 01BRRGS69, should be classified as CRF146BC. Bayesian analyses estimated the CRF146BC emergence in Brazil to be around 1999 and its introduction in Europe around 2011. CRF146BC is the 10th CRF of South American origin reported to circulate in Europe, reflecting the relationship between South American and European HIV-1 epidemics.