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Abstract The fusion protein (F) gene of Newcastle disease virus was amplified by polymerase chain reaction (PCR) from the recombinant eukaryotic expression plasmid pVAX1-F, and subcloned into the plasmid pTR-C3d3 containing three copies of C3d. The F-C3d3 gene was identified by sequencing and cloned into eukaryotic expression vector pVAX1. The recombinant plasmid pVAX1-F-C3d3 was transformed into attenuated Salmonella typhimurium SL7207, and the recombinant was designated as SL7207(pVAX1-F-C3d3). One-day-old SPF chickens were immunized orally with SL7207(pVAX1-F-C3d3) at the dosage of 1×109 CFU and boosted two weeks later with the same dose. The serum antibodies responses specific to NDV were observed in chickens immunized with SL7207(pVAX1-F-C3d3) on day 14 and 28, and their levels were significantly higher than that of SL7207(pVAX1-F) (P < 0.05). Intestinal mucosal immune response were observed in chickens immunized with recombinant bacteria on day 28, and their levels were significantly higher than that of negative and positive control (P < 0.05), but there was not significance between the groups SL7207(pVAX1-F-C3d3) and SL7207(pVAX1-F). These results indicated that three copies C3d could enhance humoral immune response against NDV induced by attenuated Salmonella typhimurium harbouring DNA vaccine. A novel mucosal DNA vaccine was developed and could be useful for controlling the infection and epidemic of Newcastle disease in the poultry.
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Received: 12 November 2008
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