Abstract
A laboratory network has been established by the World Health Organization (WHO) to systematically isolate and characterize HIV strains from different parts of the world, and to obtain information and reagents that would facilitate HIV vaccine development. Sixty-three HIV-1 isolates obtained from 224 specimens collected during 1992-1993 in Brazil, Rwanda, Thailand, and Uganda were characterized in this initial study. Virus strains were first genetically subtyped using three different screening methodologies: PCR-gag fingerprinting, RNase A mismatch, and heteroduplex mobility assay (HMA). In addition, selected viruses were sequenced in V3 (52 strains), C2-V3 (42 strains), gp120 (15 strains), and/or gp160 (8 strains) regions of their envelope genes. These studies identified viruses belonging to different sequence subtypes in the four countries: 16 subtype B and 1 subtype C strains in Brazil, 13 subtype A strains in Rwanda, 15 subtype E and 2 subtype B strains in Thailand, and 3 subtype A and 13 subtype D strains in Uganda. Comparison of sequence data with results from the genetic screening efforts identified the HMA as a rapid and reliable method for sequence subtype determinations. The majority of strains were collected from persons documented to have recently seroconverted to HIV-1 positivity, and most strains were found to have slow replication and low cytopathic characteristics and to be non-syncytium-inducing (slow/low-NSI phenotypes) in vitro, which, in many cases, correlated with the corresponding genotype and charge of the V3 loop amino acid sequences. This collection of HIV strains is presently being characterized immunologically and serologically, including neutralization assays, to define whether there are immunological correlates of the sequence subtypes. Identification of potential immunotypes would be of considerable importance for the further development of HIV vaccines.
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