Recent HIV-1 infection contributes to the viral diffusion over the French territory with a recent increasing frequency

Abstract

Objective: To analyse the contribution of primary human immunodeficiency virus type 1 (HIV-1) infection (PHI) to the French viral epidemic.

Methods: HIV-1 pol sequences included 987 PHI from the French ANRS PRIMO cohort between 1999 and 2010 and were analysed using a population-based phylogenetic approach. Clinical features, risk factors, sexual behaviour and drug resistance for clustered and nonclustered transmission events were ascertained.

Results: Viruses from 125 (12.7%) of PHI cosegregated into 56 transmission chains, with increasing frequency during the last years (10.2% before 2006 versus 15.2% of clusters in 2006-2010, p = 0.02). The mean number of patients per cluster was 2.44. Compared to unique PHI, clusters involved more often men, infected through homosexual intercourse, of young age, with a high number of casual sexual partnerships and frequent previous HIV serological tests. Resistant strains were found in 16.0% and 11.1% of clusters and unique PHI, respectively (p = 0.11). Overall, 34% (n = 9) clusters included patients followed in French regions far apart, involving 13 clusters with at least one Parisian patient.

Conclusions: PHIs are a significant source of onward transmission, especially in the MSM population. Recently infected people contribute to the spread of the viral epidemic throughout the French territory. Survey of transmitted drug resistance and behavioural characteristics of patients involved into clustered PHI may help to guide prevention and treatment interventions.

Figure 1. Evolutionary relationships of the 125 HIV-1 reverse transcriptase genes involved into cluster transmissions.

The evolutionary history was inferred using the neighbour-joining method . The optimal tree with the sum of branch length = 1.69802916 is shown. The tree is drawn to scale, with branch length in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site. Codon positions included were 1^st+2^nd+3^rd+noncoding. All positions containing gaps and missing data were eliminated from the dataset. There were a total of 408 positions in the final dataset. Phylogenetic analyses were conducted in MEGA4 . Viruses isolated in women (○), male infected through heterosexual intercourse (▪) and patients (all were men) infected through unknown intercourse (▾) were represented.