Complement-enhanced neutralizing antibody response to varicella-zoster virus.

Humoral immunity following infection with varicella-zoster virus (VZV) was evaluated by a complement-enhanced neutralization test. The specificity of the test was examined and its sensitivity compared with that of the assay which measures antibody to VZV-induced membrane antigen (FAMA). Generally, the titer of neurtalizing antibody was two- to fourfold higher than the FAMA titer. The absence of neutralizing activity at a serum dilution of 1:4 indicated susceptibility of the donor to VZV infection and correlated with an absence of FAMA (titer, less than 1:2). A survey of susceptible leukemic children exposed to chicken pox revealed that several recipients of zoster immune globulin had a subclinical infection, as manifested by seroconversion and persistence of neutralizing antibody to VZV. Results of these studies indicate that the complement-enhanced neutralization test is a sensitive and specific assay for determination of humoral immune status with regard to VZV in healthy and immunosuppressed individuals.