Determination of specific cytomegalovirus IgM antibodies using infected air dried cells and isolated nuclei by immunoperoxidase assay

A simple immunoperoxidase assay (IPA), adapted for detection of serum IgM antibodies to cytomegalovirus (CMV) is described. The antigen consisted of CMV infected human embryonic fibroblasts or isolated nuclei. The sera were absorbed with aggregated gamma-globulins prior to testing. Rabbit anti-human IgM peroxidase conjugate was used to detect IgM bound to viral antigen. In parallel the enzyme linked immunosorbent assay (ELISA) technique was used to determine IgG and IgM antibodies to CMV, respectively. All patients with acute CMV infections who were tested had CMV-specific IgM antibodies by IPA, both whole cell and nuclei antigen. The maximal IgM titers were higher by ELISA than by IPA but in 3 of the CMV patients IgM was detected earlier by IPA (with both types of antigens) than by ELISA. In 3 of 5 transplant patients with recurrent CMV infection IgM was demonstrated by immunoperoxidase techniques, while by ELISA IgM was demonstrated in only 2 of them. No cross reactivity with other herpes viruses was observed. The described IPA is simple, rapid and has the potential for widespread use in routine laboratories.