Immunoperoxidase technique for detection of antibodies to human cytomegalovirus

The indirect immunoperoxidase antibody technique (IPA) has been applied to determine immunoglobulin (Ig)G to human cytomegalovirus (CMV) antibodies in 114 blood donor sera, four cases of congenital cytomegalic inclusion disease, and four cases of acquired CMV infection. The results have been compared with those obtained with the CMV complement fixation (CF) test and indirect fluorescent antibody technique (IFA) for broad spectrum CMV antibody (sigmaAb) detection. IgG antibody has been detected by both CF and IPA. In healthy adult people IPA titers are usually higher than CF titers. In addition, IFA sigmaAb titers are generally higher than CF titers. Some sera negative by CF and IPA are positive at low dilutions of IFA sigmaAb antibody determination, due to the detection of small amounts of IgA or noncomplement fixing IgG. Nonspecific results seem unlikely, since only nuclear inclusion fluorescence was interpreted as specific, as demonstrated by blocking tests. In acute CMV infection, the IFA sigma Ab and IPA IgG titers are essentially the same, except during the first weeks of infection, when IFA titers are higher and IgM is detectable. No cross reactivity with other herpes group viruses, herpes simplex and varicella zoster, was observed. Although some problems of nonspecific staining of cytoplasmic inclusions are shared by both methods, the IPA technique seems to possess the same degree of sensitivity and specificity as the IFA technique, but interpretation is easier and various procedural steps can be delayed without the technical problems associated with fluorescence microscopy.