Immunoglobulin responses to echovirus type 11 by enzyme linked immunosorbent assay: single-serum diagnosis of acute infection by specific IgM antibody.

An indirect solid-phase enzyme-linked immunosorbent assay (ELISA) for the determination of specific IgM and IgG antibodies to echovirus type 11 in a single dilution of serum was developed using partially purified echovirus type 11 bound to microplates. Whole serum was used for IgG antibody but prior to assaying for IgM antibody interfering IgG was removed by ion exchange chromatography. The ELISA for echovirus type 11 IgG antibody was a more sensitive, rapid, technically easier and less costly alternative to the neutralisation test. With the IgG ELISA 12 of 132 sera (10.6%) known to contain enterovirus antibodies other than echovirus type 11 were positive but it could not be determined to what extent this was due to the greater sensitivity of the ELISA or cross-reactions. The IgM ELISA was even more sensitive than the IgG ELISA with acute sera, and showed a reactivity in 4 of 36 sera (11.1%) with no detectable echovirus type 11 neutralising antibodies. Echovirus type 11 IgM antibody was detected in all sera collected after the first week of infection and up to 30 days after infection. However, it was only detected in 58% of sera collected during the first week after onset thus limiting its use for rapid diagnosis. The echovirus type 11 IgM ELISA appears to have considerable laboratory diagnostic potential when a rising antibody level cannot be demonstrated in paired sera or when virus is not cultured.