Detection of antibodies to human immunodeficiency virus type 2 (HIV-2) in blood donor sera using United States assay methods for anti-HIV type 1

Twelve serum samples from French blood donors that were uniformly reactive in tests for antibody to human immunodeficiency virus type 2 (anti-HIV-2) also were reactive in 92 to 100 percent of tests with three anti-HIV type 1 (anti-HIV-1) enzyme-linked immunoassays currently in widespread use for donor screening in the United States. Supplemental tests for anti-HIV-1 on these anti-HIV-2-reactive samples differed in their responses. All samples reacted in a licensed anti-HIV-1 Western blot, but there was an atypical band near the p41 position, which could be a clue to the fact that this result was a cross-reaction with anti-HIV-2. A recombinant immunoblot gave an indeterminate result for anti-HIV-1 in all 12 samples. A local immunofluorescence assay for anti-HIV-1 reacted with 92 percent of the samples, but a commercial one detected only 58 percent.