Cloning and expression of recombinant shrimp PmRab7 (a virus-binding protein) in Pichia pastoris

Shrimp protected from a virus by feed containing yeast with a surface-displayed viral binding protein

Recombinant Pichia pastoris biomass surface-expressing the viral binding protein PmRab7 (YSD-PmRab7) was prepared by fed-batch, aerobic fermentation with methanol induction for 48 h. By cell based ELISA assay, immunofluorescence and flow cytometry, 45% of the YSD-PmRab7 cells were positive for PmRab7. Freeze dried YSD-PmRab7 cells were added to formulated shrimp feed pellets at 0.25 g and 0.5 g per g feed and fed to 2 shrimp groups for 7 days prior to challenge with white spot syndrome virus (WSSV). Controls consisted of 1 shrimp group fed normal pellets and one fed pellets containing P. pastoris carrying an empty gene cassette. At 10 days post challenge, survival in the two control groups was 6.7 ± 6.6%, while it was 26.7 ± 6.6% in the 0.25 g YSD-PmRab7 group and significantly higher (p < 0.05) in the 0.5 g YSD-PmRab7 group at 46.7 ± 10.1%. Nested PCR assays and histopathological analysis revealed significantly lower WSSV replication levels in the 0.5 g YSD-PmRab7 group. The results indicated potential for development of YSD-PmRab7 cells as an oral prophylactic against WSSV in shrimp.

Arabidopsis-derived shrimp viral-binding protein, PmRab7 can protect white spot syndrome virus infection in shrimp

White spot syndrome virus is currently the leading cause of production losses in the shrimp industry. Penaeus monodon Rab7 protein has been recognized as a viral-binding protein with an efficient protective effect against white spot syndrome infection. Plant-derived recombinant PmRab7 might serve as an alternative source for in-feed vaccination, considering the remarkable abilities of plant expression systems. PmRab7 was introduced into the Arabidopsis thaliana T87 genome. Arabidopsis-derived recombinant PmRab7 showed high binding activity against white spot syndrome virus and a viral envelope, VP28. The growth profile of Arabidopsis suspension culture expressing PmRab7 (ECR21# 35) resembled that of its counterpart. PmRab7 expression in ECR21# 35 reached its maximum level at 5 mg g(-1) dry weight in 12 days, which was higher than those previously reported in Escherichia coli and in Pichia. Co-injection of white spot syndrome virus and Arabidopsis crude extract containing PmRab7 in Litopenaeus vannamei showed an 87% increase in shrimp survival rate at 5 day after injection. In this study, we propose an alternative PmRab7 source with higher production yield, and cheaper culture media costs, that might serve the industry's need for an in-feed supplement against white spot syndrome infection.