Analysis of antibody assay methods and classes of viral antibodies in serodiagnosis of cytomegalovirus infection

Abstract
Forty-nine serum pairs with antibody to cytomegalovirus (CMV) were evaluated for rises in antibody titer (.gtoreq. 4-fold) by indirect hemagglutination (IHA) and complement fixation (CF), using a freeze-thaw antigen (FT) and a glycine extract antigen (GE). In this sample CF-FT detected more rises in antibody titer than did CF-GE. IHA detected the least number. The apparent reason for stationary antibody titers with CF-GE and IHA was the presence of high antibody titers in the 1st serum specimen. Separation of immunoglobulin classes of 20 serum pairs by sucrose gradient centrifugation indicated that these antibodies with IHA were of the immunoglobulin M (IgM) class and those with CF-GE were of the IgG class. By separation of immunoglobulin classes, rises in IgG CMV antibody titers were seen with IHA, rises not observed in the whole serum because of high IgM antibody titers in the 1st serum specimen. Absence of rises in antibody titers with CF-FT was due in part to too early sampling of the 2nd serum specimen (< 21 days) and in part to an apparent inability of some individuals to respond with antibody reactive with FT antigen. CF-GE and CF-FT antibodies of the IgM class were detected in some sera, usually in specimens collected more than 10 days after the onset of symptoms. Although reactive with CMV antigen, the specificity of these IgM antibodies in relation to rheumatoid factor requires clarification.