Genotype analysis of HIV-1 isolates from various risk groups in Metro Manila.

This research project consisted of two aspects: a seroprevalence study on HIV antibody positivity among high-risk groups in Metro Manila and genotyping of HIV-1 isolates from the seroprevalence study and known HIV(+) individuals. A total of 2084 individuals were tested for HIV antibodies of which 2 were found to be HIV(+) by enzyme linked immunosorbent assay and confirmed positive by Western blot. This gives a prevalence of 1/1000 among this high-risk group of individuals. For the genotyping study a total of 36 HIV(+) samples were collected. Polymerase chain reaction (PCR) and heteroduplex mobility assays (HMA) were performed. The most common subtype identified by PCR and HMA was type B found in 52.77% followed by subtype E in 30.55%. About 16% of the samples could not be amplified by HMA but were positive by PCR. These findings presumably reflect the modes by which the virus strain was transmitted and the exposure of the patients to certain risk groups like sex workers or overseas contract workers. Subtype B is acquired more via the parenteral route whereas subtype E has a higher heterosexual transmission efficiency. These subtype differences have implications for transmission sensitivity to antiretroviral therapy and vaccine development efforts. (authors)