Laboratory Evaluation of Method for Determination of Neutralizing Antibody against Human Enterovirus 71

Objective To evaluate the method for determination of neutralizing antibody against human enterovirus 71 (EV71)in laboratory and provide a basis for standardization of the method. Methods The neutralizing antibody titers against EV71 in 10 human immunoglobulin, 20 healthy adult plasma and 15 high titer animal immune serum specimens were determined with 10 EV71 strains of genotypes A, B and C by 5 laboratories according to the SOP for EV71 neutralizing antibody, based on which the intra-and inter-reproducibility of the method as well as effect of various EV71 strains on determination of neutralizing antibody were analyzed. Results The fold differences in maximum and minimum(Max-Min)of determination results of neutralizing antibody titers with various EV71 strains by the same laboratory were less than 4, and the results of 3 repeat tests showed no significant difference (P 0. 05). The fold differences in determination results with the same EV71 strain by various laboratories were also less than 4. The determination results with various EV71 strains by various laboratories were as follows: the fold differences of the Max-Min of neutralizing antibody titers of EV71 strain genotype A with other genotypes were not more than 192, while those of subtypes B3 with C4 were not more than 64, and those of subtype C4 with other strains were not more than 16. Conclusion By operation according to the unitary SOP, the method for determination of neutralizing antibody against EV71 showed satisfactory intra- and inter-reproducibility. However, various EV71 strains showed significant effect on the determination result.