Establishment of an indirect-blocking ELISA for detection of antibodies against NS1 proetin of avian influenza virus.

An indirect-blocking ELISA was established using a recombinant avian influenza virus(AIV) NS1 protein as the diagnostic antigen,and rabbit antiserum against the NS1 protein as the blocking antibody.The optimal concentration of the coating antigen was 0.6μg/mL,the optimal dilution of the blocking antibody was 1∶10 000,and the optimal dilution of the serum was 1∶10.Forty-two AIV-infected samples and 50 vaccinated samples were detected by the established indirect-blocking ELISA,indicating that the sensitivity of the method was 95.2%,and the specificity was 90.0%.Cross-reaction detection showed no cross-reaction to the other avian positive sera.The clinical detections showed that the negative rates of 186 antiserum samples against the inactivated vaccine,20 antiserum samples against the recombinant live vaccine and 42 serum samples from healthy avians without vaccination were 89.2%,95.0% and 100% respectively.The results indicated that this method could be used for differentiating naturally-infected poultry from vaccinated chickens.