Potency test to discriminate between differentially over-inactivated rabies vaccines: Agreement between the NIH assay and a G-protein based ELISA.

The NIH assay is used to assess the potency of rabies vaccine and is currently a key measure required for vaccine release. As this test involves immunization of mice and subsequent viral challenge, efforts are being made to develop alternative analytical methods that do not rely on animal testing. Sanofi Pasteur has reported the development of a G-protein specific ELISA assay that has shown agreement with the NIH test. In this study we have generated several non-conform vaccine lots by an excessive inactivation with ß-propiolactone (BPL) and assessed the capacity of both tests to detect the corresponding consequences. Excessive BPL inactivation causes G-protein unfolding, altering in turn viral morphology and the continuity of the G-protein layer in the viral particle. Both the NIH and the ELISA tests were able to monitor the consequences of excessive inactivation in a similar manner. Of note, the experimental error of the ELISA test was well below that of the NIH test. These results increase the prospect that the ELISA test could be considered a suitable candidate for the replacement of the NIH test.