Assessment of Haemagglutination Inhibition Assay as a True Measure of Neutralization Titre in Newcastle Disease Virus
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Date
2004
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TANUVAS, Chennai
Abstract
The present study was aimed to assess the influence of three lentogenic
Newcastle disease virus (NDV) strains viz B1, LaSota and ‘F’ in haemagglutination
inhibition (HI) test. One hundred number day-old Babcock male chicks were divided
into four groups of 25 chicks each for B1, LaSota and ‘F’ strains and unvaccinated
control. Before vaccination, the maternal antibody titre was assessed. After the
maternal antibody titre reached low level, the groups of chicks were vaccinated with
respective NDV vaccine strains. The serum samples were collected on 14 and 21 days
after homologous booster vaccination and the post vaccinal immune response was
assessed by HI test and virus neutralization test (VNT). The HI test was carried out in
a manner that each serum sample was titrated against all the three sources of
haemagglutinins viz B1, LaSota and ‘F’. Similarly, the VNT was also carried out for
pooled serum samples of respective vaccine strains, using the above three antigens.
In this study, the maternal antibody mean log2 titre was 5.5 on day one and
declined at the rate of one log2 in four days. A protective HI and virus neutralization
(VN) titres were observed in all the vaccinated groups and both HI and VN titres were
maximum at 21 days post vaccination. There was no significant difference in HI titres
using the homologous and heterologous antigens except in the serum samples of the
LaSota vaccinated group, a significantly higher titres were observed, when LaSota
strain was used as an antigen in HI test. Similarly, no significant difference was
observed in VN titres using homologous and heterologous antigens. But, in the
LaSota vaccinated group, significantly higher VN titres were observed, while using
LaSota as an antigen in VNT.
It is concluded that the use of homologous virus in the HI assay after
vaccination with LaSota strain lead to an overestimation of protective serum antibody
titres. Hence, NDV strains B1 or ‘F’ can be preferred as an antigen in HI assay to
measure the serum antibody titre.
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Keywords
Veterinary Science, Veterinary Microbiology