Evaluation of a new fourth-generation microwell enzyme-linked immunosorbent assay for detection of HIV-1 subtype B and E antibodies.

The recent fourth-generation enzyme-immunoassays have been used to increase the sensitivity for detecting HIV-1 antibodies and reduce the window period of HIV infection. The HIV antigens utilized in those assays were prepared from HIV-1 clade B which is different from HIV-1 subtypes circulating in Thailand. We evaluated 323 HIV-1 seropositives either B or E subtype to determine whether they were detected with the new combined anti-HIV and the p24 Ag assay. Under evaluation we found that this enzyme immunoassay manufactured by Organon Teknika showed the high sensitivity and specificity with a greater delta (delta) value with B than E subtypes samples (+15.29 vs +5.73).

HIV-2 infection in Thailand.

Neither the seroprevalence of HIV-2 nor the sensitivity of enzyme immunoassays for the detection of antibodies to this retrovirus have been defined in Thailand. We, therefore, Investigated these enigmas using banked sera previously screened for HIV-1 by a test that did not distinguish between HIV-1 and HIV-2. All 1,013 HIV-seroreactive specimens were positive to HIV-1 on retesting, and 740 (73%) were reactive to both HIV-1 and HIV-2. The thirty-six samples that reacted with HIV-2 at a titer of > or = 1:4,096 were further tested to discriminate between HIV-1 and HIV-2 by immunoblot assays incorporating HIV-2 recombinant proteins. One specimen was untypeable, but all others were determined to be HIV-1. Seventy-three percent of sera from Thai HIV-1 infected subjects cross-reacted with HIV-2, but not a single case of HIV-2 infection could be confirmed. The finding suggests low prevalence of HIV-2 infection in Thailand and that current testing for HIV-2 antibody is not necessary in Thai population.