الفهرس 
Complete genome sequences and development of recombinant newcastle disease virus-vectored vaccines
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Abstract
In this study, we report the first record of complete genome sequences of two Egyptian IBV strains, CU/1/2014 and CU/4/2014, belonging to IBV genotypes GI-1 lineage and GI-23 lineage, respectively. Both strains have a common genome organization in the order of 5{u2032}-UTR-1a-1b-S-3a- 3b-E-M-4b-4c-5a-5b-N-6b-UTR-poly(A) tail-3{u2032}. The genome of strain CU/1/2014 is closely related to vaccine strain H120 but showed genome-wide point mutations in addition to novel 15-nt deletion in the 4b-4c gene junction region, suggesting that strain CU/1/2014 is probably a revertant of the vaccine strain H120. Recombination analysis of strain CU/4/2014 showed evidence for recombination involving at least three different IBV strains, namely, IT/90254/2005, 4/91, and H120. These results indicate continuous evolution of IBV field strains by genetic drift and by genetic recombination between field and vaccine strains. In order to overcome this issue, and to develop a vaccine that is more relevant to Egypt, a recombinant Newcastle disease virus (rNDV) strain LaSota was constructed to express the S glycoprotein of the Egyptian IBV variant strain CU/4/2014. A wildtype and two modified versions of the IBV S protein were expressed individually by rNDV. Singledose vaccination of 1-day-old chicks with the rNDVs expressing IBV S protein provided significant protection against the clinical disease after IBV challenge but did not show a reduction in tracheal viral shedding. Single-dose vaccination also provided complete protection against virulent NDV challenge. However, prime-boost vaccination using rNDV expressing the wild-type IBV S protein provided better protection against clinical signs and significantly reduced tracheal viral shedding. These results indicate that the NDV-vectored IBV vaccines are promising bivalent vaccine candidates to control both infectious bronchitis and Newcastle disease in Egypt