Comparative study of haemagglutination inhibition, Agar gel precipitation test, Serum neutralization and Enzyme linked immunosorbent assay for detection to avian influenza viruses

Abstract

The sensitivity, specificity and reproducibility of the serological tests for detection of avian in-fluenza viruses were carried-out by using Ham- agglutination inhibition (HI), Agar gel precipita-tion test (AGPT), and Enzyme linked immu-nosorbent assay (ELISA) and Serum neutraliza-tion test. The geometric mean titre (GMT) of hae- magglutination inhibition antibodies recor- ded as log2 indicated that the post vaccination titres in the field were on higher side i.e., 7.9 for H7 and 5.9 for H9. The correlation between HI titre and AGPT affirmed that for the AGPT test need high antibody titre for positive reaction. The pooled sera were also used to correlate the se-rum neutralization test and enzyme linked im- muno-sorbent assay. The serial two fold dilute- ons were tested for the serum neutralization ac- tivity and concluded that the HI titre log2 4 pro-vided 100% protection, than 52% and 45% pro-tection in 1:2 and 1:4 dilution was recorded, respectively. Similarly, the ELISA test showed positive results up to 1:16 HI titre, i.e. log2 4 and confirmed the linear relation between these two serological tests. In HI test, the concentration of antigen can influence the result. It also needs careful preparation of concentration of eryth-rocyte suspension. Agar Gel immuno-diffusion is basically a qualitative test as it can not de-termine the quantity of antigen or antibody with the help of this test. It lacks the level of sensi-tivity as offered by other test. If serum neutrali-zation test is performed on a pooled serum sam- ples, then it could lead to a false conclusion on antibodies status. ELISA is most sensitive, spe-cific and accurate as compare to all other sero-logical tests.