Detection of serum antibodies to three different recombinant antigens of human herpesvirus 8 by immunoblotting: Seroprevalence studies in Taiwan

Background: Human herpesvirus 8 (HHV-8), a γ-herpesvirus, is associated with Kaposi's sarcoma (KS). A variety of assays for the diagnosis HHV-8 infection have been developed. However, the accuracy of current HHV-8 antibody testing is uncertain, mainly in patients with asymptomatic HHV-8 infection. Methods: We utilized a new immunoblot assay, comprised of three recombinant HHV-8 encoded proteins (ORF16, ORF57, and ORF71) to determine the seroprevalence of HHV-8 in Taiwan. ORF16 encodes a Bcl-2 homologue and is expressed only in the lytic cycle. ORF57 is an immediate-early gene product and can activate gene expression by a post-transcriptional mechanism. ORF71 encodes a viral FLICE inhibitory protein and is a latently expressed protein. We collected 6 KS(+)/HIV(-) patients, 10 KS(-)/HIV(+) individuals, 174 blood donors, and 62 non-KS cancer patients in this study. Results: Among the different populations, ORF57 showed highest reactivities. The frequency of positive results for KS(+)/HIV(-), KS(-)/HIV(+), blood donors, and non-KS cancer patients were 83.3%, 40%, 23%, and 12.9%, respectively. Compared to the widely used lytic immunofluorescence assay, our immunoblotting assay using ORF57 showed higher reactivities among the blood donors. Conclusions: ORF57 is useful for the detection of HHV-8 infection, especially during the asyptomatic infections.