Correlation between the results of two analytical methods for measuring measles virus neutralizing antibodies in source plasma and therapeutic immunoglobulin products

Patients with primary immunodeficiency disorders are vulnerable to infectious diseases. Intravenous immunoglobulin (IVIG) therapeutic products manufactured from human plasma are employed widely to protect patients from pathogens such as measles virus, which causes a potentially fatal and contagious disease. Therefore, health authorities stipulate a minimum titer of measles neutralizing antibodies (mnAbs) in IVIG products to ensure efficient protection. In general, mnAb titers are measured in a cell-based neutralization assay; however, this assay is labor intensive and time consuming, and the results are variable. Here, we compared a cell-based neutralizing assay with several ELISA tests to evaluate whether ELISAs can overcome the limitations of cell-based assays. The mnAb concentrations measured by the ELISAs showed a strong and significant positive correlation with those measured in a cell-based assay. Also, strong positive correlations were identified for measurement of individual source plasmas, which are used as raw materials for manufacturing IVIG products. Measurement by ELISA revealed that about 80% of 198 source plasmas had mnAb concentrations of <500 mIU/mL. These results suggest that quantitative ELISAs based on relevant antigens allow reliable and comprehensive measurement of mnAb concentrations in source plasmas and drug product; these ELISAs are also faster and more accurate than cell-based assay.