Restriction fragment analysis of fowlpox virus using Bgl I, Bam HI, Hha I and Sma I restriction endonucleases.

Fowlpox virus vaccine strain and two field isolates collected from out breaks of disease were purified from cell culture using sucrose gradient ultracentrifugation. The viral DNAs were digested with Bgl I, Bam HI, Hha I and Sma I restriction endonucleases and the fragment pattern was analysed on 0.7% agarose gel. Bgl I digestion produced 54 fragments of size ranging from 31.50 to 0.60 kb, having similar electrophoretic mobilities in both the vaccine strain and two field isolates. Only 9 well resolved and one unresolved or partially digested fragment were obtained after Bam HI digestion. A total number of 29 and 41 fragments were obtained with Hha I and Sma I respectively. Almost similar restriction fragment pattern was observed in vaccine strain and the field isolates. The total genomic size was calculated to be between 265.00 and 302.91 kb. The three viruses were found to be genetically similar.

Comparative immunological and genomic characterization of fowlpox virus isolates.

Chickens infected with fowlpox virus (FPV) IVRI vaccine strain and two field isolates collected from clinical cases of disease (Bareilly isolate and Panchmahal isolate) produced humoral antibody response after 2nd week post-infection, with a noticeable variation in degree of immune response. Serum antibody titre peaked at 4th week post-infection with a titre of 25,600, 25,600 and 51,200 being detected in ELISA and neutralization index of 2.75, 2.43 and 3.12 in serum neutralization test (SNT) with IVRI vaccine strain, Panchmahal isolate and Bareilly isolate, respectively. Cellular immune response was detected as early as 1st week post-infection by leukocyte migration inhibition test (LMIT). Per cent migration inhibition too peaked at 4th week with a value of 40.30 +/- 3.45, 36.93 +/- 4.11 and 45.45 +/- 3.66 being detected with the three viruses respectively. The Hind III and Hae III restriction fragment profile of viral DNA showed almost similar pattern both in vaccine strain and two field isolates. Hind III digestion produced 47 well resolved fragments of sizes between 24.30 and 1.20 kb and the total genomic size was estimated to be between 305.81 and 306.06 kb. Hae III digestion revealed 34 well resolved fragments of sizes between 27.55 and 1.32 kb. The three viruses could not be differentiated on the basis of their genomic restriction pattern. However immunogenic and antigenic differences were noticed by ELISA and SNT tests.