V3 sequence analysis and biological characterization of HIV-1 isolates from asymptomatic and early symptomatic Tanzanian individuals

The aim of this study was to determine HIV-1 V3 sequences, in vitro biologi cal characteristics and co-receptor usage of virus isolates from Tanzania. Virus was isolated from 14 of 17 samples investigated. Four of the isolates induced syncytia in MT-2 cells and used the CXCR4 co-receptor, while the r emaining 10 isolates used the CCR5 co-receptor characteristic of non-MT-2 t ropic viruses. One of the four MT-2 tropic isolates also used the CCR5 and CCR3 co-receptors. Proviral DNA was detected in all 14 isolates and PCR pro ducts were subjected to DNA sequencing. Unambiguous V3 amino acid sequences were obtained from 11 amplificates. Phylogenetic analysis indicated that t hese sequences were divergent and clustered in HIV-I subtypes A, C or D. Se quences from the viruses that induced syncytia in MT-2 cells presented char acteristic V3 phenotype-associated amino acids. Results of co-receptor anal ysis are in concordance with the isolate phenotype as determined by replica tion and induction of syncytia in MT-2 cells. The considerable diversity il lustrated by a limited number of isolates from Tanzania is in accordance wi th reports from other regions of Africa.