Detection of antibodies to human herpesvirus-6 using immunofluorescence assay

A serological study of human herpesvirus-6 (HHV-6) infection was performed by means of immunofluorescence assay on fixed HHV-6-infected cells. Comparison between indirect immunofluorescence assay (IFA) and anticomplement immunofluorescence assay (ACIF) showed that the latter test was the most appropriate for HHV-6 serology, although both methods exhibited identical sensitivity. ACIF, which was performed on HSB2 cells infected with the HBLV strain (provided by S.Z. Salahuddin), was then used to determine the titre of HHV-6 antibodies in serum by end-point dilution. The sera from 115 healthy subjects and 99 patients with presumed viral infection were tested. A similar distribution of HHV-6 titres was evidenced in both cases and the rate of individuals exhibiting a positive titre of 20 and above was about 30% of the whole population studied. No serological cross-reactivity was observed between HHV-6 and other herpesviruses, suggesting that the HHV-6 ACIF test was quite specific.