[Evidence of infection by HIV-2 in Madrid (1991)]

Results are presented of a study undertaken in Madrid to determine the prevalence of HIV-2 antibodies in serum samples indeterminate for HIV-1. The similarity of HIV-1 and HIV-2 has caused great difficulty in their differential diagnosis. The similarity is especially strong for the nuclear proteins and to a lesser extent for the proteins of the envelope. The World Health Organization (WHO) recently proposed that at least 2 bands be present on the envelope in order to consider a Western Blot positive. Tests using synthetic peptides exclusive for each virus have also been developed. 842 serum samples from individuals at high risk for HIV-1 infection were collected at the Center for Clinical Research a referral hospital for infectious diseases in Madrid during October 1990-May 1991. The samples were screened for presence of HIV-1 and HIV-2 using a 3rd generation solid-phase enzyme immunoassay (EIA) test designed to detect antibodies against either virus. Samples with absorbencies in the positive or threshold range were analyzed with HIV-1 Western Blot. Samples with threshold absorbencies in the mixed EIA and those that were indeterminate with the HIV-1 Western Blot were analyzed using a Western Blot specific for HIV-2 and a test with synthetic peptides for each virus (Pepti-lav Pasteur). Western Blot results were interpreted using WHO criteria. All samples from African immigrants with positive EIA results were also analyzed with the HIV-2 Western Blot and the Pepti-lav regardless of the result of the Western Blot for HIV-1. 334 (40%) of the 842 samples analyzed presented absorbencies in the positive range in the EIA and another 16 had threshold values. The HIV-1 Western Blot was positive for 324 of the 334 positive samples and indeterminate for the other 10. The HIV-1 Western Blot was indeterminate in 5 of the 16 with threshold values and negative in the rest. 3 of the 10 samples with indeterminate HIV-1 Western Blot results and positive EIA were positive in the HIV-2 Western Blot. 2 of the 16 samples with threshold EIA values gave indeterminate results with the HIV-2 Western Blot and the rest were negative. The Pepti-lav confirmed the HIV-2 positivity in the 3 samples positive for HIV-2 on Western Blot. The 3 samples positive for HIV-2 were from asymptomatic individuals from Guinea-Bissau Cameroon and South Africa. The remaining samples with indeterminate or discordant HIV-1 serology were analyzed with the Pepti-lav. No sample negative in the HIV-1 Western Blot was positive with the Pepti-lav but 8 samples with indeterminate HIV-1 Western Blot results were positive with the Pepti-lav.