Comparative assay of varicella skin test antigens by the ELISA and RPHA tests

The antigenic potency of the varicella skin test antigens was assayed by reversed passive haemagglutination (RPHA) test using sheep red blood cells coated with zoster convalescent serum and by enzyme linked immunosorbent assay (ELISA) using anti-VZV sera or monoclonal antibody to gpI followed by an anti-IgG beta-galactosidase conjugate. Three kinds of varicella skin test antigens were compared: a soluble varicella skin test antigen, a modified soluble varicella skin test antigen, and a crude varicella skin test antigen. The RPHA test was suitable for the soluble and for modified soluble varicella skin test antigens but it was not suitable for the crude varicella skin test antigen. ELISA was applicable for all the three antigen types. It was possible to assess quantitatively the content of viral antigens in the same type of the skin test antigen, but not by comparing the different skin test antigen types. ELISA was more efficient in the quantitative assay of the amount of viral antigens than the RPHA test.