SUMMARYThe indirect immunofluorescence technique has been used to titrate the specific immunoglobulins in 200 sera from 64 patients with varicella, and 195 sera from 67 patients with herpes zoster. IgG and IgM antibodies were detected in all patients with varicella, and IgA in 59 (92 %). All three classes of antibody appeared 2-5 days after the onset of the rash, increased virtually simultaneously and reached maximum titres during the second and third weeks. IgG then declined slowly, but never became undetectable and was still present in five subjects who were retested after 2-4 years; it was present in 88 out of 100 healthy young adults and probably persists indefinitely after varicella. IgA and IgM antibodies declined more rapidly and were not detected in specimens taken more than a year after the illness. IgA, however, may possibly persist in some cases since low titres were found in 8 out of 88 young adults who possessed IgG antibody and had presumably had varicella in the past. IgA responses were significantly weaker in children under the age of 6 years than in older children and adults.Six out of 67 patients with zoster were tested at various times before the onset of the rash: IgG antibody was detected in all. IgG was present in all sera taken after the onset of the rash, increased rapidly after 2-5 days, reached maximum titres during the second and third weeks and then declined slowly. IgA antibody was detected in 66 patients (99 %) and IgM in 52 (78 %); both types of antibody followed transient courses, as in varicella.Maximum titres of IgG and complement-fixing antibodies were greater after zoster than after varicella, but the differences were not significant. IgA and IgM titres in young adults with zoster were significantly lower than in older patients, and also lower than in young adults with varicella.Increases in varicella-zoster antibody in patients with herpes simplex virus infections consisted mainly of IgG, sometimes IgA, but never IgM.

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A simple and sensitive M antibody-capture radioimmunoassay (MACRIA) is described which utilizes crude commercial VZV antigen and a single monoclonal anti-VZV antibody. This was compared to the immunofluorescence (IF) test for IgM antibody and was used to study IgM responses in sera from 261 patients with varicella and 220 patients with herpes zoster. With MACRIA, IgM antibodies were detected in all patients with varicella. The IgM antibodies appeared shortly after onset of rash, reached peak levels between 1 and 4 weeks after onset and then declined to low or undetectable levels in most, though not all, patients after 3 months. IgM antibodies were also detected in 98.2% of patients with herpes zoster, but the levels of IgM were significantly lower than after varicella and there was wider individual variation both in magnitude and duration of the IgM responses, in some cases only lasting 2-3 weeks. Comparison between MACRIA and IF showed good agreement in the detection of IgM antibodies following varicella. Discordant results were obtained with 13% of sera, of which 81% were taken either early or late after onset of rash and contained very low IgM levels. In contrast, 62 (28%) of the 220 sera from patients with zoster gave discordant results in the two tests, all except five being MACRIA-positive but IF-negative. The largest proportion of discordant results were obtained with sera taken more than 3 months after onset of rash, but 18 (29%) contained high IgM levels and were taken during the period of peak IgM responses. The diagnostic applications of the VZV MACRIA are discussed.

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