Cross-reactivity on Western blots in HIV-1 and HIV-2 infections

To examine cross-reactivity of antibodies to heterologous antigens on HIV-1 and HIV-2 Western blots the authors tested sera from 1362 consecutive tuberculosis (TB) patients and 2127 consecutive blood donors. Specimens positive on enzyme-linked immunosorbent assay (ELISA) for HIV-1 and HIV-2 were further characterized by synthetic peptide-based tests and tested by HIV-1 and HIV-2 specific Western blots. Dual serological reactivity on synthetic peptide tests was proportionately more frequent in HIV-positive TB patients than in blood donors and HIV-2 reactivity less frequent. Positive HIV-1 Western blots were seen in 73-83% of specimens specifically characterized as positive for HIV-2 on synthetic peptide tests. Cross-reactivity to HIV-2 Western blots by HIV-1 positive specimens was significantly more frequent in TB patients (35%) than in asymptomatic donors (9%; p<0.001). Using recently recommended criteria for HIV-2 Western blot interpretation (presence of 2 env bands) reduced the overall proportion of HIV-1 positive specimens having a positive HIV-2 Western blot from 27.5 to 16.4% suggesting minimal effect on sensitivity in the diagnosis of HIV-2 reactivity on specimens positive on synthetic peptide tests. (authors)