Abstract
Six commercially available monovalent Newcastle disease virus (NDV) live-vaccines were examined for their biological and genomic stability in comparison to their stated parent virus. Thermostability of the hemagglutinin at 56° C for 5 min was consistently observed among the majority of the vaccine viruses. One exception was a recently developed NDV vaccine isolated from turkeys that had a thermostability of 15 min. Neuraminidase activity, as measured by elution rate of agglutinated red blood cells, varied among vaccine viruses and correlated with that of the parent isolate. Virulence as measured by intracerebral pathogenicity index ranged from 0 to 0.39 among NDV vaccine-type viruses, well within the range of avirulent lentogens. Sequence of the fusion protein cleavage site from all the NDV vaccine isolates examined was consistent with that for lentogens. The entire hemagglutinin-neuraminidase gene sequence was 98% similar among all the NDV vaccine viruses examined and phylogenetic classification of commercial vaccine types correlated with their respective parent virus. Consequently, the commercially produced NDV vaccines reported here appear relatively stable when mass produced in avian embryonated eggs.
Published Version
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