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Title: In vivo selection of CVI988 based vaccine, pCVI988-699-2: characterization of its efficacy and safety

item MCDOWELL, ERIN - University Of Delaware
item DONG, HUIMIN - University Of Delaware
item KATNENI, UPENDRA - University Of Delaware
item GADDAMANUGU, SYAMSUNDAR - University Of Delaware
item TAVLARIDES-HONTZ, PHAEDRA - University Of Delaware
item PARCELLS, MARK - University Of Delaware
item SHAIKH, SHIREEN - University Of Delaware
item Spatz, Stephen

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2014
Publication Date: 7/20/2014
Citation: McDowell, E., Dong, H., Katneni, U., Gaddamanugu, S., Tavlarides-Hontz, P., Parcells, M.S., Shaikh, S.R., Spatz, S.J. 2014. In vivo selection of CVI988 based vaccine, pCVI988-699-2: characterization of its efficacy and safety. In: Proceedings of the 10th International Symposium on Marek's Disease and Avian Herpesviruses, July 20-23, 2014, East Lansing, Michigan. p. 65.

Interpretive Summary:

Technical Abstract: In order to increase the efficacy of current vaccines, we have constructed a bacterial artificial chromosome (BAC),id-based infectious clone of CVI 988 (Rispens) of low passage (p23), using deoxyribonucleic acid (DNA) provided from Merial, Inc., and obtained from the Central Veterinary Institute, Lelystad, the Netherlands. We used a mix of CVI 988-BAC clones to vaccinate commercial broiler chickens challenged in a TK-strain-based shedder trial. One day prior to study termination, 6 healthy chickens were selected and peripheral blood mononuclear cells (PBMC’s) in spleen cells were collected for virus isolation. We isolated several BAC-containing viruses from spleen cells:-culture, but not from PBMC’s. One isolate, 699 clone number 2 was examined for Marek's disease protection and safety. In several industrial-sponsored shedder trials, CVI 988 – 699 – 2 DEL (the vaccine from which the BAC sequences were derived), showed superior efficacy to several commercial CVI 988 (Rispens) vaccines. CVI 988-699-2 DEL showed a reversion to virulence, however, upon serial back passage in specific pathogen free (SPF) leghorn chickens, indicating that despite efficacy and commercial broilers, CVI 988 – 699 – 2 DEL retains some pathogenicity serial in vitro back passage was capable of selecting for a reversion to virulence.