Title: Recombinant Newcastle disease vaccines: risk for reversion to virulence and spread in non-target species Authors
Submitted to: International Poultry Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 30, 2012
Publication Date: January 22, 2013
Citation: Krishna, H., Diel, D.G., Afonso, C.L., Suarez, D.L., Miller, P.J. 2013. Recombinant Newcastle disease vaccines: risk for reversion to virulence and spread in non-target species. International Poultry Forum Proceedings. CDROM. Interpretive Summary: In this study we investigated the risk associated with the use of live recombinant Newcastle disease virus (rNDV) vaccines in to control the disease in the field. Our objectives are: 1) determine the risk of rNDV vaccines attenuated by changes in the virus fusion protein cleavage site to revert to their highly pathogenic type; and 2) determine the abilityof rNDV vaccines to infect and transmit in pigeons. Inoculation of 14-day-old embryonating chicken eggs (ECSs) with field NDV strains LaSota and Australia or with rNDV Lasota or ZJ1 (rZJ1*lento) (900 eggs/virus) caused the death of 65 (7.2%), 10 (1.1%), 23 (2.5%) and 6 (0.6%) embryos, respectively within 72 h post inoculation. The sequence of the fusion protein cleavage site demonstrated that under these experimental conditions, all recombinant viruses were stable and did not revert to a virulent phenotype to become pathogenic. When NDV rLaSota and rLaSota/Avian-Influenza-H5 were inoculated in pigeons we observed that these viruses are able to infect this species and also spread between infected and non-infected contact birds. All birds that were inoculated with these viruses excreted virus in oral and/or cloacal secretions, and at least one of four contact birds excreted virus for two or more days. These results suggest that our system can be used to assess the risk associated with recombinant NDV vaccines.
Technical Abstract: The present study is being conducted to determine the risk associated with using live recombinant NDV(rNDV) vaccines in the field. The goals of this study are to 1) determine the risk of rNDV vaccines, containing an attenuated fusion (F) protein cleavage site, to revert back to a virulent virus phenotype; and 2) to assess the ability of rNDV vaccines to infect and spread in non-target species. Infection of 14-day-old embryonating chicken eggs (ECEs) with wild type NDV strains LaSota and Australia or with rNDV strains LaSota (rLaSota), or ZJ1 (rZJ1*Lento) (900 eggs/virus), resulted in the death of 65 (7.2%), 10 (1.1%), 23 (2.5%), and 6 (0.6%) embryos, respectively within 72 h pi. Sequencing of the F gene cleavage site revealed that, under our experimental conditions, all recombinant viruses are stable and did not revert to a virulent phenotype. Experiments to assess the ability of recombinant NDV vaccines to infect and spread in pigeons have shown that rLaSota and rLaSota/AIV-H5 are able to infect and spread in this species. All virus-inoculated birds shed the virus in oral and/or cloacal secretions and at least one out of four contact birds shed the virus for two or more days. These findings suggest that our system is suitable to assess the risk associated with rNDV vaccines.