Biological characterization and chemokine receptor usage of HIV type 1 isolates prevalent in Brazil

The human immunodeficiency virus type 1 (HIV-1), the etiological agent of t he acquired immunodeficiency syndrome (AIDS), shows a variety of biological properties, which may constitute an obstacle to development of effective v accines or antiretroviral therapy. To characterize Brazilian strains of HIV -1, we studied 24 viruses isolated from blood samples of HIV-1-positive pat ients from different regions of the country. To examine the cell tropism an d the virus ability to form syncytia, primary macrophages and the CD4(+) T cell line MT-2 were infected with these viruses. We found that 22 isolates replicated well in macrophages (macrophage-tropic isolates), 2 infected onl y MT-2 cells (T cell line tropic variants), while 6 of them grew in both ce lls. We found 8 syncytium-inducing (SI) and 16 non-SI (NSI) isolates. Conti nuous cultures of 18 isolates were established in the CCR5(+)/CXCR4(+) cell line PM-1, and SI/NSI features of these viruses were confirmed by cell fus ion assay with uninfected CD4(+) T cell lines (PM-1, MT-2, H9, and SUP-T1). The coreceptor usage of 18 isolates was investigated by infecting U87 cell s transfected with CD4 and chemokine receptors, and we found that 11 isolat es infected only CCR5(+) cells, 3 only CXCR4(+) cells, whereas 4 used both coreceptors. We also observed that X4 isolates were more sensitive to neutr alization by dextran sulfate than R5 or R5X4 viruses. Our findings show tha t the Brazilian isolates are phenotypically similar to those prevalent in o ther regions, which could mean that therapeutic strategies based on HIV-1 p henotypic properties would be efficient in Brazil, as in other countries.