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

Abstract

Introduction: 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.

Figure 1

Bayesian time-scaled tree of the 55 HIV-1 CRF 02_AG pol sequences from MSM. The numbers at the root and at the internal nodes represent the estimated date of the origin and the uncertainty indicated by 95% highest posterior density (95% HPD) intervals. The asterisks (∗) along a branch represent significant statistical support for the clade subtending that branch (posterior probability >98%). Non-Italian sequences are in bold. The line at the bottom represents time (in years).

Figure 2

Bayesian skyline plot (BSP) of the 55 HIV-1 CRF 02_AG pol sequences from MSM. The effective number of infections is reported on the Y-axis. Time is reported in the X-axis. The colored area corresponds to the credibility interval based on 95% highest posterior density interval (HPD).