Newcastle disease vaccines hitherto in vogue are produced from
embryonated chicken eggs. Egg-adapted mesogenic vaccines possess several drawbacks
such as paralysis and mortality in 2-week-old chicks and reduced egg production in
the egg-laying flock. Owing to these possible drawbacks, we attempted to reduce the
vaccine virulence for safe vaccination by adapting the virus in a chicken embryo
fibroblast cell culture (CEFCC) system. Eighteen passages were carried out by CEFCC,
and the pathogenicity was assessed on the basis of the mean death time, intracerebral
pathogenicity index, and intravenous pathogenicity index, at equal passage intervals.
Although the reduction in virulence demonstrated with increasing passage levels in
CEFCC was encouraging, 20% of the 2-week-old birds showed paralytic symptoms with the
virus vaccine from the 18th(final) passage. Thus, a tissue-culture-adapted
vaccine would demand a few more passages by CEFCC in order to achieve a complete
reduction in virulence for use as a safe and effective vaccine, especially among
younger chicks. Moreover, it can be safely administered even to unprimed 8-week-old
birds.
Microrhizomes were produced from leaf disc derived callus of a threatened endemic medicinal plantDecalepis hamiltonii. Murashige and Skoog (MS) medium supplemented with 2 M 6-benzyleaminopurine (BAP) and 6 M 1-napthaleneacetic (NAA) acid was found to be optimum for rapid callus induction and establishment from leaf disc explants. Further differentiation of callus into microrhizome was conquered in MS medium supplemented with 4 M indole-3-butyric acid (IBA) and 8 M NAA. A maximum of 20 microrhizomes in a cluster was produced within 90 days. Yeast extract (0.05%) and polyvinylpyrrolidone (0.05%) further enhanced the microrhizome formation when supplemented along with plant growth regulators (PGRs).
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