title: Changing patterns in HIV-1 non-B clade prevalence and diversity in Italy over three decades.
abstract: BACKGROUND
  HIV-1 non-B subtypes have recently entered Western Europe following immigration from other regions. The distribution of non-B clades and their association with demographic factors, over the entire course of the HIV-1 epidemic, have not been fully investigated in Italy.
  
  
  METHODS
  We carried out a phylogenetic analysis of HIV-1 pol sequences derived from 3670 patients followed at 50 Italian clinical centres over nearly three decades.
  
  
  RESULTS
  Overall, 417 patients (11.4%) carried non-B subtypes. The prevalence of non-B strains increased from 2.6% in 1980-1992 to 18.9% in 1993-2008 (P<0.0001) in a subset of 2479 subjects with a known year of diagnosis. A multivariate analysis on a subset of 1364 patients for whom relevant demographic data were available indicated that African ethnicity, heterosexual route of infection and year of diagnosis were independently associated with non-B HIV-1 infection (P ≤ 0.0001). All pure subtypes, except for clade K, and seven circulating recombinant forms were detected, accounting for 56.6 and 34.1% of the non-B infections, respectively. The F1 subtype was the most prevalent non-B clade among Europeans and was acquired heterosexually in half of this patient population. Unique recombinant forms accounted for 9.4% of the non-B sequences and showed a B/F1 recombination pattern in one-third of cases.
  
  
  CONCLUSIONS
  The circulation of non-B clades has significantly increased in Italy in association with demographic changes. Spread of the F1 subtype and B/F recombinants appears to predominate, which may result in a redistribution of the relative proportions of the different strains, and this could lead to overlapping epidemics. Thus, the HIV-1 landscape in Italy may in future be distinct from that of the rest of Europe.
authors.affiliation: Section of Infectious Diseases and Immunopathology, Department of Clinical Sciences, L Sacco Hospital, University of Milan, Milan, Italy. alessia.lai@unimi.it
authors.forename: A
authors.initials: A
authors.lastname: Lai
authors.forename: C
authors.initials: C
authors.lastname: Riva
authors.forename: A
authors.initials: A
authors.lastname: Marconi
authors.forename: M
authors.initials: M
authors.lastname: Balestrieri
authors.forename: F
authors.initials: F
authors.lastname: Razzolini
authors.forename: G
authors.initials: G
authors.lastname: Meini
authors.forename: I
authors.initials: I
authors.lastname: Vicenti
authors.forename: A
authors.initials: A
authors.lastname: Rosi
authors.forename: F
authors.initials: F
authors.lastname: Saladini
authors.forename: I
authors.initials: I
authors.lastname: Caramma
authors.forename: M
authors.initials: M
authors.lastname: Franzetti
authors.forename: V
authors.initials: V
authors.lastname: Rossini
authors.forename: A
authors.initials: A
authors.lastname: Galli
authors.forename: M
authors.initials: M
authors.lastname: Galli
authors.forename: M
authors.initials: M
authors.lastname: Violin
authors.forename: M
authors.initials: M
authors.lastname: Zazzi
authors.forename: C
authors.initials: C
authors.lastname: Balotta
mesh_terms: D000328:Adult; D003710:Demography; D004812:Epidemiologic Methods; D005260:Female; D015751:Genes, pol / Q000235:genetics*; D005838:Genotype; D015658:HIV Infections / Q000453:epidemiology* / Q000821:virology; D015497:HIV-1 / Q000145:classification* / Q000235:genetics*; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D044469:Racial Groups / Q000706:statistics & numerical data; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D017678:Sex Distribution; D012725:Sexual Behavior; D013997:Time Factors