An enzyme-linked immunosorbent assay for detection of avian influenza virus subtypes H5 and H7 antibodies

Abstract

Background: Avian influenza virus (AIV) subtypes H5 and H7 attracts particular attention because of the risk of their potential pathogenicity in poultry. The haemagglutination inhibition (HI) test is widely used as subtype specific test for serological diagnostics despite the laborious nature of this method. However, enzyme-linked immunosorbent assays (ELISAs) are being explored as an alternative test method.H5 and H7 specific monoclonal antibodies were experimentally raised and used in the development of inhibition ELISAs for detection of serological response specifically directed against AIV subtypes H5 and H7. The ELISAs were evaluated with polyclonal chicken anti-AIV antibodies against AIV subtypes: H1N2, H5N2, H5N7, H7N1, H7N7, H9N9, H10N4 and H16N3.

Results: Both the H5 and H7 ELISA proved to have a high sensitivity and specificity and the ELISAs detected H5 and H7 antibodies earlier during experimental infection than the HI test did. The reproducibility of the ELISA's performed at different times was high with Pearson correlation coefficients of 0.96-0.98.

Conclusions: The ELISAs are a potential alternative to the HI test for screening of large amounts of avian sera, although only experimental sera were tested in this study.

Figure 1

ROC curves for inhibition ELISAs. A) H5 ELISA and B) H7 ELISA. The lowest of the inhibition% (inh-%) given by each successive ELISA using H5N7ag/H5N2ag for H5, H7N1ag/H7N7ag for H7, is taken into account, Sens: sensitivity, spec: specificity, their percentage is shown in y-axis.

Figure 2

Correlation between repeated ELISA testing on different days. (A) H5N7 antigen and (B) and H7N1 antigen, Inh%: Inhibition%.