Production of Bovine Rotavirus VP6 Subunit Vaccine in a Transgenic Fodder Crop, Egyptian Clover (Berseem, Trifolium alexandrinum) that Elicits Immune Responses in Rabbit

Group A rotavirus causes acute gastroenteritis in young ones of animals worldwide and is responsible for a high rate of their morbidity and mortality leading to huge economic losses. Developing affordable and safer vaccine on large scale is imperative to reach cattle population worldwide for the long-term control of diarrhea. Rotavirus middle capsid protein layer, VP6, is the most immunogenic and highly conserved protein that induces immune responses against rotavirus. In the present study, bovine group A rotavirus VP6 protein has been expressed for the first time in a highly nutritious and palatable forage crop, Trifolium alexandrinum, using Agrobacterium tumefaciens-mediated stable nuclear transformation. Transgenic nature of the shoots regenerated from cotyledon explants and rooted on hygromycin-containing medium was confirmed by polymerase chain reaction (PCR), Southern blot hybridization, reverse transcription-PCR (RT-PCR) and quantitative real-time PCR (qPCR), and protein expression and quantification by Western blot and enzyme-linked immune-sorbent assay (ELISA), respectively. The transformation efficiency of 2.10% was obtained. The highest amount of VP6 protein produced in a transgenic line was 402 ng/g fresh weights (0.03% of total soluble protein). Oral feeding of transgenic leafy shoots expressing VP6 protein stimulated systemic immunity by inducing significantly higher titers of anti-VP6 serum IgG antibodies in rabbit to reduce rotavirus infection. These transgenic fodder plants offer safer vaccine produced on large scale at low cost with reduced regulatory issues to improve livestock's health and wealth. These plants would be used as alternative to the current live attenuated vaccines to protect young calves against rotavirus infection.