Cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with Enterovirus 71 and Coxsackievirus A 16.

To evaluate the cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with EV71 and CA16. Real-time RT-PCR, virus isolation, ELISA and neutralization test were used to detect enteroviruses from clinical specimens and series sera of 79 HFMD patients. 27 EV71, 37 CA16, and 11 other enterovirus-infected patients were identified by RT-PCR. Among EV71 infected patients, anti-EV71 IgM positive ratios were 87.5% during 1-3 days after onset and 100% over 4 days after onset. In CA16 infected patients, the positive ratios were 7.4%, 26.4%, and 62.5% during 1-3 days, 4-6 days, and over 6 days after onset, respectively. Meanwhile, the results of neutralization test showed 18.9% of CA16 infected patients and 11.1% of EV71 infected patients present high cross-neutralization antibody against each other. Cross-reactivity of anti-EV71 IgM in patients infected with EV71 and CA16 becomes stronger with the progress of disease. Moreover, high cross-neutralization antibody existing in part of patients suggests that the immune reactivity to EV71 infection can be recalled by CA16, and the immune reactivity to CA16 infection can be recalled by EV71. Therefore, identifying enteroviruses by neutralization test may not be an ideal selection.