Antigenic analysis of human herpesvirus 7 (HHV-7) and HHV-6 using immune sera and monoclonal antibodies against HHV-7.

Using polyclonal and monoclonal (MAbs) antibodies to human herpesvirus 7 (HHV-7), we have studied HHV-7-specific polypeptides. Human sera were obtained during the convalescent phase from patients with exanthem subitum due to HHV-7, and at least 16 HHV-7-specific polypeptides with apparent molecular masses of 26-210 kDa were immuno-precipitated. Sera prepared in mice also precipitated at least 17 HHV-7-specific polypeptides with molecular masses of 26-210 kDa. Among them, the most commonly observed antigenic protein had an apparent molecular mass of 52 kDa. Forty-two clones secreting MAbs against HHV-7-specific proteins, as determined by immunofluorescence assays, were established from BALB/c mice immunized with HHV-7-infected cell extracts. Seven MAbs which immunoprecipitated HHV-7-specific polypeptides were further characterized. Two of these, MAbs 5E12 and 5F12, reacted predominantly with glyco-proteins of 78 kDa and 85 kDa, respectively, and possessed neutralizing activity. This suggests that there are at least two neutralization-inducing proteins in HHV-7. MAb 16B4 reacted with the major immunogenic protein of 52 kDa. Five of the 42 MAbs also reacted in immunofluorescence assays with HHV-6 antigens to the same degree as to HHV-7. Two other MAbs, 7C10 and 10F1, recognized an HHV-7 protein of 40 kDa, and only 7C10 cross-reacted with an HHV-6 protein of 45 kDa.