HIV-1 recombinant forms in immigrants regularly residing in Milan, northern Italy.

To assess the HIV -1subtypes distribution in HIV-1 positive migrants living in Milan we studied 77 HIV-1 patients followed at the San Raffaele Hospital of Milan. Twenty subjects were born in Europe, 43 in the Americas, 10 in Africa and 4 in Asia. Unsafe heterosexual activity prevailed in migrants born in Africa and male homosexuality in those born in European, American and Asian countries (p = 0.05). The phylogeny showed that 38/77 (49.3%) subjects carried HIV-B subtype while the remaining strains were classified as not pure HIV-1 B subtypes 13/77 (16.9%) or recombinant forms 26/77 (33.8%). Female gender more frequently showed HIV-1 non-B strains and rarely HIV-1 B subtypes (12/39, 30.8% vs. 3/38, 7.9%, p = 0.02). Transmitted drug resistance was identified in 10/77 (13%) patients predominately with B subtype. Our data underscore a large heterogeneity in HIV-1 subtypes and a large proportion of recombinant forms.