Strategies for diagnosing HIV-1 infection in atypical Western blots.

The Western blot (WB) has long been used to confirm positive ELISAs for diagnosing HIV-1 infections. However, some WB patterns may result in "indeterminate" or controversial reports thus impeding early diagnoses or accurate diagnoses. The interpretation of HIV-1 WB has no "gold standard" criterion. Incomplete antibody profiles on WB strips can be interpreted as positive or indeterminate according to different criteria. The possibility of HIV-2 infection was further checked in these serum samples. However, no reactivity to synthetic peptide of HIV-2 gp36 had been found. Serial WB analyses are important for attaining early diagnoses of HIV-1 infections as well as for evaluating clinical stages. Temporal changes on WB patterns of serial serum samples provide the evidence of seroconversion in individuals with risk behaviours and indeterminate WB. In late stage of HIV-1 infection, the reactivity to gag, pol and env antigen groups may decrease and result in indeterminate WB. We propose to diagnose HIV-1 infection and to differentiate the infection of HIV-1 from HIV-2 in these cases by using nested polymerase chain reaction (PCR) to demonstrate the presence of HIV-1 specific vpu gene.