A simplified and standardized neutralization enzyme immunoassay for the quantification of measles neutralizing antibody.
A simplified and standardized neutralization enzyme immunoassay (Nt-EIA) was developed to detect measles virus growth in Vero cells and to quantify measles neutralizing antibody. Heat-inactivated sera were diluted serially 4-fold and tested in duplicate. The 50% reduction point (50%RP) of virus growth was calculated using the Reed-Muench formula and the neutralizing antibody titre of test sera was converted into mIU/ml by comparing their 50%RP with that of the international standard serum. The optimal virus input and incubation time were found to be 50-100 plaque forming unit (PFU)/well and 64-72 h, respectively. The simplified Nt-EIA had a good reproducibility with only 3.7-4.2% of duplicate tests having a ratio > 4 in an evaluation of intra assay variation and the coefficients of variance were 2-9% in an evaluation of inter assay variation. In addition, the simplified Nt-EIA had a high sensitivity(98.6%), specificity (100%) and agreement (98.8%) in qualitative comparison with plaque reduction neutralization test (PRNT). In quantitative comparison, the correlation coefficient between Nt-EIA and PRNT was 0.83 without log transformation or 0.77 after log transformation and 90% of 61 positive sera had a ratio < 4 between antibody titre tested by the two methods. The simplified Nt-EIA is thus a suitable alternative to the PRNT for the quantification of measles neutralizing antibody.
Lee
M S
MS
Wellcome Centre for the Epidemiology of Infectious Disease, Oxford University, UK. min-shi.lee@zoo.ox.ac.uk
Cohen
B
B
Hand
J
J
Nokes
D J
DJ
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D002522:Chlorocebus aethiops; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D008457:Measles / Q000175:diagnosis*; D008459:Measles virus / Q000254:growth & development / Q000276:immunology*; D009500:Neutralization Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014709:Vero Cells; D010948:Viral Plaque Assay
D000914:Antibodies, Viral