Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 1995
Publication Date: N/A
Interpretive Summary: Highly virulent Newcastle disease virus (NDV) can cause severe respiratory and digestive disease in commercially produced poultry. To avoid this viral disease, poultry are vaccinated almost universally with NDV strains that do not cause disease. These vaccines are produced on a large scale commercially for use during poultry production. It is known that during replication, viruses like NDV may undergo genetic changes that could affect their ability to protect against disease. To test if these commercially produced vaccines have changed in their biologic or genetic properties six NDV vaccines were examined using several methods. All the commercial vaccines examined had biologic properties and a genetic makeup that was the same as the viruses originally used for vaccination against NDV. Consequently, even though these NDV vaccines are produced on a large scale they appear to be very stable under current production conditions.
Technical Abstract: Six commercially available Newcastle disease virus (NDV) vaccines were examined for their biological and genomic stability in comparison to their stated parent virus. Thermostability of the hemagglutinin at 56 degrees C for five minutes 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 minutes. 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 (ICPI) 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 (HN) gene e sequence was 98 percent similar among all the NDV vaccine viruses examine and phylogenetic classification of commercial vaccine types correlated with their respective parent virus. Consequently, these commercially produced NDV vaccines appear relatively stable when mass produced in avian embryonated eggs.