Site-directed enzyme-linked immunosorbent assay with a synthetic simian immunodeficiency virus SIVmac peptide identifying antibodies against the HIV-2 transmembrane glycoprotein

A 23-amino-acid-long peptide (AIEKYLEDQAQLNAWGCAFRQVC) representing the transmembranous protein gp32 in SIVmac was used in site-directed enzyme-linked immunosorbent assay (ELISA) for detection of HIV-2-specific antibodies in 567 sera from Bissau, Guinea Bissau. Ninety out of the 567 sera were identified to contain HIV-2 antibodies by whole antigen ELISA and Western blot assays. The peptide ELISA correctly identified 89 out of these 90 seropositives (sensitivity 98.9%). Three sera falsely interpreted to be positive were encountered (specificity 99.4%). The HIV-2 peptide was also used for testing of 93 HIV-1-positive Swedish sera. None of these sera reacted. Site-directed serology employing synthetic peptides should be considered for application as a screening assay.HIV-1 is predominant in Central and East Africa, while HIV-2 is predominant in West Africa. The HIV-2 virus, originally described as human T-lymphotropic virus type IV, is identical to the simian immunodeficiency virus SIV-mac. Whole-antigen enzyme-linked immunosorbent assay (ELISA) can detect heterotypic antigens in 80% of sera, but separate tests are required for detecting HIV-1 and HIV-2. Site-directed ELISA using amino acids 586-620 of the synthetic transmembranous protein gp41 as antigen has been used for type-specific antibody determination in HIV-1. The homologous site on the 23-amino-acid-long peptide AIEKYLEDQAQLNAWGCAFRQVC representing the transmembranous protein gp32 in the simian immunodeficiency virus SIV-mac is WGCAFR, which can be used in site-directed serology of HIV-2. This approach was tested on sera from 567 Africans in Guinea-Bissau and 49 suspected AIDS patients. None of these sera had HIV-1 antibodies. 93 HIV-1-positive sera from Sweden were used as controls. The HIV-2 peptide ELISA correctly identified 89 of the 90 HIV-2 seropositives out of the sample of 567. The peptide ELISA also correctly identified all of the 93 HIV-1-positive sera as HIV-2-negative. Use of HIV-2-specific ELISA in combination with an HIV-1-specific ELISA can efficiently screen blood for both types of HIV.