Circulation of HIV-1 CRF02_AG among MSM population in central Italy: a molecular epidemiology-based study

The evolutionary and demographic history of the circular recombinant form CRF02 AG in a selected retrospective group of HIV-1 infected men who have sex with men (MSM) resident in Central Italy was investigated. Methods. A total of 55 HIV-1 subtype CRF02 AG pol sequences were analyzed using Bayesian methods and a relaxed molecular clock to reconstruct their dated phylogeny and estimate population dynamics. Results. Dated phylogeny indicated that the HIV-1 CRF02 AG strains currently circulating in Central Italy originated in the early 90’s. Bayesian phylogenetic analysis revealed the existence of a main HIV-1 CRF02 AG clade, introduced in the area of Rome before 2000 and subsequently differentiated in two different subclades with a different date of introduction (2000 versus 2005). All the sequences within clusters were interspersed, indicating that the MSM analyzed form a close and restricted network where the individuals, also moving within different clinical centers, attend the same places to meet and exchange sex. Conclusions. It was suggested that the HIV-1 CRF02 AG epidemic entered central Italy in the early 1990s, with a similar trend observed in western Europe