Assessment of Mumps Virus-Specific Antibodies: Comparison of Plaque Reduction Neutralization Test and Enzyme-Linked Immunosorbent Assay Estimates

Abstract

Background: The plaque reduction neutralization test (PRNT), which measures a subset of immunoglobulin antibodies (functional neutralizing antibodies), and the enzyme-linked immunosorbent assay (ELISA), which measures total immunoglobulin (neutralizing and nonneutralizing antibodies), characterize different aspects of the anti-mumps virus antibody response after vaccination.

Methods: Data from a recent phase 3 clinical trial (NCT01681992) of 2 measles-mumps-rubella vaccines were used to compare anti-mumps antibody responses measured using an unenhanced PRNT (GSK; seropositivity cutoff and threshold, 2.5 and 4 times the 50% end-point dilution, respectively) with those estimated using an ELISA (thresholds, 5 and 10 ELISA units/mL, respectively).

Results: Of 3990 initially seronegative samples, 3284 (82.3%) were seropositive after vaccination for anti-mumps antibodies in both assays. The Pearson correlation coefficient for double-positive samples was 0.57, indicative of a moderate correlation. Receiver operating characteristic curve analysis showed that an ELISA threshold of 51.7 ELISA units/mL best corresponded to the PRNT seroresponse threshold. There was no obvious vaccine brand effect on the correlation between assays.

Conclusions: The moderate correlation between the anti-mumps antibody measurements obtained with PRNT and ELISA reflects different aspects of the serological response. In the absence of a well-defined protective serological threshold, PRNT provides complementary information on the antibody response, whereas ELISA remains a critically useful measurement of vaccine immunogenicity.

Keywords: enzyme-linked immunosorbent assay; mumps; plaque reduction neutralization test; seropositive; seroresponse; vaccine.

Figure 1.

Scatterplot of mumps antibody values (log-transformed enzyme-linked immunosorbent assay [ELISA] concentrations versus log-transformed plaque reduction neutralization test [PRNT] titers), with Deming regression line and 80% prediction interval (PI) limits, in 3284 double-seropositive postvaccination serum samples. Abbreviations: CI, confidence interval; MMR, measles-mumps-rubella.

Figure 2.

Scatterplot of mumps antibody values (log-transformed enzyme-linked immunosorbent assay [ELISA] concentrations vs log-transformed plaque reduction neutralization test [PRNT] titers), with Deming regression line and 80% prediction interval (PI) limits, in double-seropositive postvaccination serum samples, according to measles-mumps-rubella (MMR) vaccine received (MMR-RIT for 2107 serum samples; MMR II for 1177 serum samples). Abbreviation: CI, confidence interval.

Figure 3.

Receiver operating characteristic (ROC) curve of sensitivity (calculated as the number of double-positive samples divided by the total number of plaque reduction neutralization test [PRNT]–positive samples) versus “1 − specificity” (specificity calculated as the number of double-negative samples divided by the total number of PRNT-negative samples), using a PRNT seroresponse threshold of 4 times the 50% end-point dilution (ED₅₀). Asterisk denotes the enzyme-linked immunosorbent assay (ELISA) threshold (in ELISA units per milliliter) best corresponding to the PRNT seroresponse threshold of 4 ED₅₀.