Evaluation of the focus reduction neutralization and ELISA tests compared to the plaque reduction neutralization test for the detection of antibodies against measles virus

Abstract Measles is an infectious febrile sickness. Despite the existence of effective vaccination, eradicating measles remains a global priority. It is required to set up a sensitive and specific test to identify measles-specific antibodies in order to estimate the level of community protection against measles. Although the plaque reduction neutralization test (PRNT), the gold standard test, is technically challenging, it is not suitable for routine use. The enzyme-linked immunosorbent assay (ELISA) was also unable to detect weak antibody responses in people vaccinated against measles. As a result, the FRNT (focus reduction neutralization test) was established and validated. In eight assay runs, the samples were analyzed in triplicate by PRNT, FRNT, and ELISA. In a total of 50 samples analyzed, 38/50 samples were positive by standard PRNT, 37/50 samples by FRNT, and 19/50 samples were positive by ELISA. The results showed that ELISA was not sensitive enough to identify low levels of anti-measles antibodies, and that ELISA and both neutralization assays had a weak agreement. The two neutralization assays, on the other hand, had a perfect correlation. Finally, the PRNT and FRNT have similar sensitivity. For characterizing the immunological response to measles and vaccination efficacy trials, FRNT seems to be a good alternative to PRNT. Therefore, it will be very important to validate the negative and equivocal ELISA results with this standard test in the final stages of eradication.