# Viruses Previously Classified as CRF146_BC, a Circulating Recombinant Form of HIV-1 Recently Reported in Brazil, Represent Different Recombinant Forms, One of Which Is Circulating in Spain

## TL;DR

This study clarifies the classification of HIV-1 recombinant forms previously labeled as CRF146_BC, finding that only some viruses should be grouped together based on genetic analysis.

## Contribution

The study redefines which viruses belong to CRF146_BC by analyzing genetic sequences and proposes a revised classification.

## Key findings

- Genetic analysis revealed that only 10BR_RJ009 and BC3 viruses should be classified as CRF146_BC.
- CRF146_BC is estimated to have emerged in Brazil around 1999 and spread to Europe by 2011.
- This is the 10th South American HIV-1 recombinant form reported in Europe.

## Abstract

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 (10BR_RJ009) previously classified as CRF146_BC. 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 10BR_RJ009, with two breakpoints delimiting a ~0.3 kb subtype B fragment within an otherwise subtype C genome. Two other Brazilian viruses previously classified as CRF146_BC (10BR_RJ039 and 01_BR_RGS69) had one and two additional short subtype B fragments, respectively, and failed to group with the 10BR_RJ009/BC3 cluster in subtype C fragments. Based on these results, we contend that 10BR_RJ009 and BC3 viruses, but not 10BR_RJ039 and 01_BR_RGS69, should be classified as CRF146_BC. Bayesian analyses estimated the CRF146_BC emergence in Brazil to be around 1999 and its introduction in Europe around 2011. CRF146_BC is the 10th CRF of South American origin reported to circulate in Europe, reflecting the relationship between South American and European HIV-1 epidemics.