Fowlpox virus structural protein immunogens and characterization of single band polypeptide.

A fowlpox virus isolate obtained from an outbreak of disease in a vaccinated poultry flock was propagated in chicken embryo fibroblast cell culture. Analysis of purified virus polypeptide on 7.5-15% gradient polyacrylamide gel revealed 45 structural polypeptides after Coomassie blue staining. The mol.wt. of polypeptides ranged between 225.53 and 10.50 kDa with total mol.wt. of 2650 kDa. Variable numbers of immunogenic virion polypeptides were detected in immunoblot with fowlpox virus infected chicken sera collected at different time intervals. A total of 29 polypeptides reacted with sera collected at 1st week post-infection and the number gradually declined to 27, 26, 20, 17 and 15 when reacted with 2nd, 3rd, 4th, 5th and 6th week post-infection sera, respectively. Reaction with fowlpox virus hyperimmune sera revealed 35 immunogenic polypeptides. A number of major and minor immunogens were detected. Antisera against seven major single band polypeptides including one double band polypeptide showed very low reactivity both in ELISA and serum neutralization test. Involvement of multigenic components in virus neutralization is indicated.

Structural proteins of fowlpox virus vaccine strain and field isolates.

Structural polypeptides of IVRI vaccine strain and two field isoaltes of Fowlpox virus (Bareilly isolate and Panchmahal isolate) were analysed on SDS-PAGE and by immunoblotting technique. In 5%-20% gradient acrylamide gel 31, 29 and 31 polypeptide bands and in 7.5%-15% gradient gel 45, 37 and 39 polypeptide bands were detected after Coomassie blue staining respectively for Bareilly isolate, Panchmahal isolate and IVRI vaccine strain. The molecular weight (MW) of the polypeptides ranged from 226.10 to 10.30 kDa with total MW of 2650.12, 2259.50, and 2378.68 kDa respectively for the three viruses. The immunoblot revealed 35, 29 and 30 immunogenic polypeptides indicating most virion polypeptides to be immunogenic in nature. Although most polypeptides had similar electrophoretic pattern both in SDS-PAGE and immunoblotting, still the three viruses could be differentiated. The viruses were found to be antigenically different with Panchmahal isolate lacking the polypeptides 81.15, 76.33, 39.30, 37.50 and 29.35 kDa and the vaccine strain lacking 76.33, 37.50 and 29.35 kDa polypeptides as were present in Bareilly isolate.