Genetic analysis of HIV-1 isolates from Brazil reveals presence of two distinct genetic subtypes

Abstract

The spread of the human immunodeficiency virus type 1 (HIV-1) is by now virtually worldwide. An understanding of the genetic, biological, and immunological differences among isolates collected in different geographic locales is crucial for the development of globally effective vaccines. Here we report the genetic characteristics of 21 HIV-1 isolates from Brazil. The isolates were initially characterized using a heteroduplex mobility assay. The majority (17 of 21) were related to North American/European reference isolates of genetic subtype B. Four isolates belonged to a more recently identified genotype, termed subtype F. The subtype F sequences from Brazil are distinguishable in both gag and env from five other genetic subtypes of HIV-1 currently recognized. Like many locales, Brazil harbors more than one HIV-1 subtype.

PIP: The spread of the human immunodeficiency virus type 1 (HIV-1) is by now virtually worldwide. An understanding of the genetic, biological, and immunological differences among isolates collected in different geographic locales is crucial for the development of globally effective vaccines. The genetic characteristics of HIV-1 isolates from whole blood samples of 21 HIV-1-seropositive Brazilian patients collected during 1989 and 1990 are reported. Virus was isolated by cocultivation of patient peripheral blood mononuclear cells (PBMCs) with phytohemagglutinin (PHA)-stimulated donor PBMCs. The isolates were initially characterized using a heteroduplex mobility assay, which estimates the DNA sequence homology of a selected genomic region from different HIV-1 isolated from the migration of heteroduplexes in polyacrylamide gels. Five distinct HIV-1 envelope subtypes were identified, and a sixth subtype, termed F, was identified using isolates from Brazil and Romania. One Brazilian isolate was identified as subtype B by the more rapid relative migration of heteroduplexes. The majority (17 of 21) were related to North American/European reference isolates of genetic subtype B, whereas 4 isolates belonged to subtype F, a more recently identified genotype. The gag and env genes of several Brazilian isolates belonging to subtypes B and F were cloned and sequenced to allow a detailed analysis of their phylogenic relationships. This further established the existence of two distinct and well-separated genetic subtypes among Brazilian HIV-1 isolates. The subtype F sequences from Brazil are distinguishable in both gag and env from 5 other genetic subtypes of HIV-1 currently recognized. Like many locales, Brazil harbors more than one HIV-1 subtype.