Identification of a new HIV-1 BC circulating recombinant form (CRF60_BC) in Italian young men having sex with men

- An outbreak of BC recombinants was recently described involving young Italian MSM.
- Full length analysis of three HIV-1 BC recombinants with no epidemiological link.
- Identification of the first Italian circulating recombinant form, CRF60_BC.

HIV-1 recombination, reverse transcriptase (RT) low fidelity and high replication rate are the drivers of variability and evolution on the global scale. Only few of these HIV-1 chimeric forms have been characterized in Europe, despite 20% of infections are due to unique or circulating recombinant forms worldwide. An outbreak of BC recombinants has been recently described in a southern region of Italy, Apulia, in men having sex with men (MSM) seeking sexual partners on-line.We analyzed the full length genome of HIV-1 BC recombinants harbored by three recently infected subjects, two MSM and a heterosexual woman, with no evidence of epidemiological link. The recombination analysis showed a unique recombination pattern of a subtype C genome with 3 subtype B fragments corresponding to HXB2 positions: [1-463] in the 5′LTR , [2804-3037] in RT and [8662-9548] corresponding to the C-terminal segment of gp41, nef and most of 3′LTR.Phylogenetic analysis revealed the South American origin of the C subtype parental strain. A research conducted in an Italian nationwide database provided six additional similar sequences from other Italian regions with identical recombination pattern in pol gene; a further BLAST search retrieved one full length genome isolated in France with the same mosaic pattern, except an additional B subtype short fragment in the integrase region. These recombinant isolates, designated CRF60_BC, led to the identification of the first Italian circulating recombinant form, which gave rise to an epidemic burst mainly involving MSM.