Enzyme immunoassays for the demonstration of antibodies to HIV-2SBL-6669 and HTLV-IV (SIVmac).

Enzyme-linked immunosorbent assays (ELISA) were developed for the demonstration of antibodies to HIV-2 using disrupted virions of the SBL-6669 isolate of HIV-2 and the so-called human T-lymphotropic virus type 4 (HTLV-4) recently found to be identical with the simian immunodeficiency virus (SIVmac) as antigens. 300 sera from West African subjects attending an outward clinic in Bissau for examination of suspected tuberculosis were tested by these 2 assays as well as by a commercially available anti-HIV-2 ELISA (ELAVIA 2). 50 of these sera were positive in all 3 ELISAs as well as in Western blot tests against HTLV-4. 38 of these positive sera were also tested by an anti-HIV-2 Western blot kit (LAV-Blot 2) with positive results. The ELISAs based on SBL-6669 and HTLV-4 antigens had a specificity of 99.6% (1 false positive among 250 negative sera) whereas the specificity of ELAVIA 2 was 94.6% using the recommended cutoff value and 98.4% using a higher cutoff value. Another 58 sera from West African patients clinically suspected of having AIDS or HIV-related disease were tested for HIV-2/HTLV-4 antibodies by Western blot and by ELISA against SBL-6669 and HTLV-4 antigens; all of the 30 sera which were positive by Western blot were found to be positive in both ELISAs. Testing of 100 HIV-1 positive sera (50 from East Africa and 50 from Sweden) in the SBL-6669 and HTLV-4 ELISAs showed a higher degree of cross-reactivity among the East African sera (76 and 74% respectively) compared to the Swedish sera (30 and 32% respectively). Thus the SBL-6669 and the HTLV-4 ELISAs had a high sensitivity (100%) for detection of HIV-2 antibodies and a high specificity for HIV antibodies. (authors)