Phenotypic characterization of HIV-1 isolates recovered from patients in Riruta health centre, Nairobi
Muriuki, Joseph Kimiru
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Kenya displays a wide genetic diversity of HIV-1 group M subtypes with subtype A being the most dominant followed by D, C, recombinants A/D and the circulating recombinant forms CRF10 - CD and CRF02-AG. While some information is available on Kenyan HIV-1 strains genotype, limited information is available on their biological phenotype. HIV-1 shows a variety of biological properties which may constitute an obstacle in the development of effective vaccines and antiretroviral therapy. Two distinct biological phenotypes have been described on the basis of their ability or inability to produce cytopathic effects in MT-2 cells: the syncytia inducing (SI) and non syncytia inducing (NSI) phenotypes. Previous reports demonstrated that progression to AIDS is associated with increasing viral load, deterioration of immunological status, and emergence of drug-resistant strains with more cytopathic viral phenotypes. In vitro methods to determine phenotype from HIV-1 clinical isolates are therefore of prognostic value and provide an important tool to study HIV pathogenesis. Phenotype also determines cell tropism. Macrophage (M) tropic viruses will infect cells expressing Cystein linked chemokine receptor-5 (CCR5) whereas T cell line tropic and dual tropic viruses will infect cells expressing CXC chemokine receptor -4 (CXCR4). Currently new drugs based on chemokine inhibition are being developed. To evaluate their efficacy, there is need to have local virus isolates that are well characterized. The objective of this study was to obtain HIV-1 primary isolates and characterize them phenotypically. HIV-1 was isolated using the traditional co-culture technique. Viral load was determined using nuclisense Easy Q assay (Biomereaux, France) and the Cluster of differentiation-4 (CD4+) count by cyflow counter (Partec, Germany). The P24 antigen enzyme linked immunosorbent assay (ELISA) was used to determine HIV-1 isolation success. The primary isolates obtained were used to infect MT2 cells to determine virus phenotype and coreceptor usage. Indirect immunofluorescence assay was then used to check the antigen expression on the cells and confirm infectivity. Overall isolation success rate for both drug experienced and naive patients was 30%. HIV-1 was successfully isolated from 70% (7/10) and 20% (2/20) of naive and drug experienced patients respectively. A correlation between virus isolation success and viral load was established. This study showed no correlation between CD4 count and HIV-1 isolation success. Majority of the viral isolates obtained (6/9) were of SI phenotype. These means upcoming drugs which are CCR5 inhibitors (Inhibitors against NSI HIV-1 strains) may not work for the majority of the Kenyan HIV/AIDS patients. Once these drugs are available in Kenya, both CCR5 and CXCR4 chemokine inhibitors should be included in the national HIV/AIDS management programme.