Vaccinated students with negative enzyme immunoassay results show positive measles virus-specific antibody levels by immunofluorescence and plaque neutralisation tests

Calibration and Evaluation of Quantitative Antibody Titers for Measles Virus by Using the BioPlex 2200

“…In this study, the correlation of the quantitative result of the BioPlex 2200 MMRV IgG assay and the reference method (PRNT) is higher for "nonequivocal" specimens (Ͼ192 mIU/ml) and specimens with low concentrations of neutralizing antibody do not correlate well. This observation has been previously reported for other EIA methods and is attributed to the fact that PRNT only measures neutralizing IgG, whereas EIA-based tests measure total anti-measles IgG (14,15,20,26,29). This lack of sensitivity may lead to an underestimation of the number of protected individuals in seroepidemiological studies.…”

“…5). The considerable variance between the titers measured by BioPlex 2200 MMRV IgG assay and PRNT is due to low correlation between the titer of neutralizing antibodies measured by PRNT and the titer of total antibodies measured by EIA methods, especially at lower values (14,15,26).…”

“…PRNT measures with greater sensitivity neutralizing antibodies, directed at specific epitopes of the surface hemagglutinin and fusion proteins (24,30,32). These differences make direct comparison of the two assays problematic, especially at low antibody titers (14,15,26). A study examining sera from health care workers in the Netherlands found that the seropositivity rates of four different qualitative EIAs compared to PRNT ranged from 89 to 97%, with the greatest variation in the cohort born in from 1975 to 1985, suggesting waning immunity in individuals with antibodies generated from a single MMR vaccine rather than natural exposure.…”

“…The method of screening samples by EIA and confirming them by PRNT on select specimens is not a new concept (15,26). In a serological study of infants at 4 weeks postimmunization, 27% of the specimens with an EIA result below a predetermined cutoff to maximize sensitivity and specificity required PRNT to ensure that all seroconversions were detected (15).…”

Building an Immunity Fence against Measles

“…Chen et al have shown that 8 of 9 college students with titers Ͻ1:120 (Ͻ200 mIU/mL) immediately preceding a measles outbreak developed disease, compared with 0 of 71 with titers 1:120 [13]. Studies using some commercial EIAs have shown the tests to be less sensitive than PRNT but highly specific [14,15]. It is unclear how well antibody levels measured by the EIA used in the McQuillan et al study correlate with protective levels of antibody as they are defined by the PRNT.…”