Occurrence of false positives in tests with synthetic peptides for the analysis of antibodies against the human immunodeficiency virus type 2 (HIV-2) in Brazilian patients infected with the human immunodeficiency virus type 1 (HIV-1)

Abstract

At the present time two distinct viruses are known to cause AIDS the HIV-1 type virus and the HIV-2 type virus. The former was primarily isolated in Europe and the latter was initially restricted to western Africa. In Brazil data on infections caused by HIV-2 are conflicting having been derived from metropolitan and port-city populations. Some authors deny the existence of HIV-2 in the country. In the interior in the city of Ribeirao Preto with a population of 500000 the rate of HIV incidence was 273.5/100000 population during the period 1980-95. Most seropositive patients and AIDS patients are cared for at the Hospital of Clinics of the Medical School of Ribeirao Preto where routine HIV-2 antibody tests are not administered. Therefore the presence of HIV-2 was investigated in 88 patients (72 men and 16 women) carrying HIV-1 during March-April 1992. The HIV-2 antibody test utilized the recombinant antigens of HIV-1 and HIV-2 containing latex particles the Recombigen HIV-1/HIV-2 Rapid Test Device (Cambridge Biotech Corp.). 26 of the 88 sera analyzed were positive for both HIV-1 and HIV-2 yielding a 29.5% (26/88) positivity for both viruses. Subsequently the 88 sera were processed by the Pepti-Lav 1-2 test (Diagnostics Pasteur) which is an immunoenzymatic test detecting reactivity against gp41 and gp36. The result was 88 positive findings for HIV-1 and 2 positive HIV-2 antibody findings for both HIV-1 and HIV-2 yielding a 2.3% positivity for the sample analyzed. Discrepancies between different tests are not rare. The Recombigen use instructions warn that if protein recombinants are used a 25-30% rate of false positives can occur. The Pepti-Lav which detects more specific proteins is more sensitive and specific. The 2 positive HIV-2 sera were also examined by PCR (partition chromatography?) which did not show positivity. This indicates that caution should be exercised when interpreting test results.