Immunofluorescence assay for detection of antibodies to human immunodeficiency virus type 2

A total of 215 serum samples were tested for antibodies against human immunodeficiency virus type 2 (HIV-2) with an immunofluorescence assay (IFA). Some samples originated from Denmark and some originated from Guinea-Bissau. The IFA results were compared with enzyme-linked immunosorbent assay (ELISA) and Western (immuno-) blot (WB) results. Twenty-nine serum samples were found to be true positive for HIV-2 antibodies as judged from WB and radioimmunoprecipitation results; all of these were also found to be positive in the HIV-2 IFA. Of 80 serum samples originating from HIV-1-infected persons, 60% showed reactivity in the HIV-2 ELISA, and 51% cross-reacted with at least one band in the HIV-2 WB. None of the sera cross-reacted in the HIV-2 IFA. A total of five serum samples (three African and two Danish) gave unspecific results in the HIV-2 IFA. It is concluded that the HIV-2 IFA is more specific and at least as sensitive as a first-generation ELISA and that IFA is superior to WB in discriminating between HIV-1 and HIV-2 infections.