High concentrations of measles neutralizing antibodies and high avidity measles IgG accurately identify measles reinfection cases.

Tuesday, 5th of July 2016

Clin Vaccine Immunol. 2016 Jun 22. pii: CVI.00268-16. [Epub ahead of print]

High concentrations of measles neutralizing antibodies and high avidity measles IgG accurately identify measles reinfection cases.

Sowers SB¹ Rota JS² Hickman CJ² Mercader S² Redd S² McNall RJ² Williams N² McGrew M²Walls ML² Rota PA² Bellini WJ².

Author information

Abstract

In the United States approximately 9% of measles cases reported from 2012-2014 occurred in vaccinated individuals. Laboratory confirmation of measles in vaccinated individuals is challenging since IgM assays can give inconclusive results. Although a positive RT-PCR result from an appropriately-timed specimen can provide confirmation negative results may not rule out a highly suspicious case. Detection of high avidity measles IgG in serum samples provides laboratory evidence of a past immunologic response to measles from natural infection or immunization. High concentrations of measles neutralizing antibody have been observed by plaque reduction neutralization (PRN) assays among confirmed measles cases with high avidity IgG referred to here as reinfection cases (RICs). In this study we evaluated the utility of measuring levels of measles neutralizing antibody to distinguish RICs from non-cases by receiver operating characteristic curve analysis. Single and paired serum samples with high avidity measles IgG from suspected measles cases submitted to CDC for routine surveillance were used for the analysis. The RICs were confirmed by a fourfold rise in PRN titer or by RT-qPCR while the non-cases were negative by both assays. Discrimination accuracy was high using serum samples collected at ≥3 days post rash onset (area under the curve: 0.953; 95% confidence interval (CI): 0.854 to 0.993). Measles neutralizing antibody concentrations ≥40000 mIU/mL identified RICs with 90% sensitivity (95% CI: 74%-98%) and 100% specificity (95% CI: 82%-100%). Therefore when serological or RT-qPCR results are unavailable or inconclusive suspected measles cases with high avidity measles IgG can be confirmed as RICs by measles neutralizing antibody concentrations ≥40000 mIU/mL.

Copyright © 2016 Sowers et al.