Sensitive solid-phase radioimmunoassay for detection of human immunoglobulin G antibodies to varicella-zoster virus

A sensitive solid-phase radioimmunoassay for detection of antibodies to varicella-zoster virus (VZV) is described. The antigen consisted of a sonically disrupted extract of VZV-infected human embryo cells. ¹²⁵I-labelled rabbit anti-human immunoglobulin G (IgG) specific for the Fc portion of human IgG was used to detect human IgG bound to viral antigen. With this technique, 193 human sera were evaluated for their IgG antibody titer against VZV. Subjects included 62 healthy adults, 33 young children (12 healthy), and 49 patients. Titers obtained by the radioimmunoassay were compared with those obtained by indirect fluorescence antibody staining of membrane antigen. The radioimmunoassay technique described gave titers approximately 5 x 10⁴ times higher than those shown by indirect fluorescence. It can be used for routine diagnosis, but is especially suited for determining immune status to VZV, as defined by presence or absence of antibodies to the virus; for epidemiological studies; or for determining patients at risk who are exposed to the virus. No heterotypic titer rises to VZV were observed in sera with fourfold or greater rises to Epstein-Barr virus or cytomegalovirus. Sera of eight subjects with fourfold or greater titer rises to herpes simplex virus reacted in various ways: in six cases no significant change occurred in titer to VZV; one had a significant decrease in titer by the radioimmunoassay; and one had a significant increase. Possible reasons for these titer changes are discussed.