THE MOLECULAR EPIDEMIOLOGY OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 IN EDINBURGH

Human immunodeficiency virus (HIV) type I sequences obtained from HIV- infected persons in different risk groups in Edinburgh were studied to determine the number and origin of virus variants and patterns of vir us transmission. Phylogenetic analysis revealed that 12 of 14 hemophil iac patients who had been exposed to a single common batch of factor V III had closely related gag gene sequences. Sequences from intravenous drug users and patients infected through heterosexual contact formed another distinct group, and 2 other hemophiliacs formed a third group. However, epidemiologic relationships inferred from analysis of the V3 region of the env gene were less conclusive, especially when the V3 l oop was taken in isolation. This appears to be due to the length of ti me since infection and the action of selection, which has favored the independent appearance of similar V3 loop variants.