The use of transgenic tobacco as a production and delivery system for a vaccine against hemorrhagic enteritis virus of turkeys.
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Hemorrhagic enteritis virus (HEV) causes an acute viral disease in turkeys characterized by bloody diarrhea and death. Current live HEV virus vaccines are immunosuppressive and predispose turkeys to secondary bacterial infections. Data indicates that the capsid proteins (fiber, penton base, hexon) of HEV are capable of stimulating protective antibodies against an HEV challenge. Using tobacco as a model, we sought to determine if a plant could be used to synthesize the HEV fiber protein and produce sufficient antigen to stimulate protective antibodies. To introduce the fiber gene into plants, the coding region of the HEV fiber gene was fused to either a constitutive plant promoter (35S) or a wound inducible promoter (hmg2) on plasmids adapted for Agrobacterium-mediated transformation. Approximately sixty transgenic plants of each construct were generated and determined to contain the HEV fiber gene based on amplification of specific HEV DNA sequences by the polymerase chain reaction. Plants were screened by Northern dot blot to identify lines expressing high levels of fiber mRNA. Expression of fiber protein was observed in selected lines of transgenic tobacco by Western blot analysis using turkey anti-HEV serum. The accumulation of fiber protein in leaves of tobacco transformants was quantified by Sandwich ELISA. Fiber protein from these plants has undergoing large-scale purification and concentration for a turkey immunization trials to determine if plant expressed fiber antigen is capable of inducing protective antibodies against HEV in turkeys.
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