1008 SUBCLINICAL ZOSTER: IDENTIFICATION BY SERUM IgM TO VARICELLA-ZOSTER (VZ) VIRUS

It has been postulated that reactivation of VZ virus occurs if immunity to VZ wanes, from aging or disease. However, our studies with fluorescent antibody to VZ membrane antigen (FAMA) indicate that antibody does not decrease with age. Of 100 persons, geometric mean titers of VZ antibody were: 1:15 between ages 41-60, 1:19 between 61-70, and 1:27 above age 71. In an attempt to detect subclinical zoster in older persons, we measured VZ- IgM by FAMA and immune adherence on IgM fractions from sucrose density gradients. VZ-IgM was detected in 8/16 zoster patients (50%), and in the following persons without zoster: 5/10 immunocompromised (50%), 6/28 over age 60 (21%), and 4/18 young adults (20%). Rheumatoid factor was present in 14% of VZ-IgM positive sera. A leukemic child had 3 episodes of clinical zoster. VZ-IgM was present 2/2 times tested, and at 3 other times when the child had no zoster. One infant with intrauterine varicella had a VZ-IgM titer of 1:32 at 9 mos. These data show the instability of latent VZ virus in man, and suggest that subclinical zoster occurs. VZ-IgM may be a marker for latent VZ infection.