Development of Measles Immunoglobulin M Detecting Enzyme-Linked Immunosorbent Assay (IgM ELISA) Using Recombinant Nucleoprotein of Measles Virus

ABSTRACT

Rapid and reliable diagnosis of measles is important to establish an appropriate therapy and to monitor the epidemic. However, classical ELISA methods using purified virus or virus-infected cells as antigens are not only difficult to determine optimal condition for diagnosis but also highly expensive to establish routine and appropriate diagnostic systems. Nucleoprotein of measles virus is one of the major antigens of measles virus that evoke initial IgM responses. It can be used as an attractive antigen for sero-diagnosis of measles during early infection. To develop simple and inexpensive diagnostic method for measles, we expressed a recombinant nucleoprotein (60-kDa) and a fragmented portion of the nucleoprotein (50-kDa) in E. coli and evaluated their appropriateness as diagnostic antigens. The proteins strongly reacted with sera from measles patients but not with normal control sera. Efficiency of recombinant nucleoprotein-ELISA (rN-ELISA) to detect IgM was compared that of whole measles virus-ELISA (MV-ELISA) on the basis of a clinical diagnosis. In rN-ELISA, sensitivity was 73.8% and agreement was above 76.4%. In MV-ELISA, sensitivity was 76.9% and agreement was 79.2%. Therefore, efficacy of rN-ELISA seemed to be similar to that of MV-ELISA. In addition, we compared with Edmonston rN-ELISA and Korean isolate rN-ELISA on the basis of commercial MV-ELISA. In Edmonston rN-ELISA, sensitivity was 94.0% and agreement was 98.4%. In the case of Korean isolate rN-ELISA, sensitivity was 96.0% and agreement was 96.9%. Thus, there was no significant difference in the efficacy between Edmonston rN-ELISA and Korean isolate rN-ELISA. Furthermore, the correlation coefficient (R2) between Edmonston rN-ELISA and Korean isolate rN-ELISA was 0.9925. These results suggest both Edmonston and Korean isolate rN-ELISA may be useful to diagnose measles.