Identification And Evaluation On An Outer Membrane Protein OmpU From A Pathogenic Vibrio Harveyi Isolated As Vaccine Candiadate In Turbot (Scophthalmus Maxiumus)

Vibrio harveyi is a Gram-negative bacterium. The bacterium has been reported as major causal agent of luminous vibriosis, which affected a diverse range of marine invertebrates. Mass mortalities of shrimp larvae due to V. harveyi infection have been reported from a number of countries. V. harveyi has also been associated with fish diseases in China and South Asian countries.The main aims of this study were cloning and expression of a new outer membrane protein OmpU from a pathogenic V. harveyi SF-1 and investigate its immune efficiency as a vaccine candidate against V. harveyi infection in turbot (Scophthalmus maximus). In this study, a new outer membrane protein gene, ompU was cloned from the genomic DNA of pathogenic V. harveyi SF-1. The ompU gene encoded a 35 kDa protein, which was purified by Ni-NTA metal affinity chromatography. A DNA vaccine was constructed by inserting ompU gene into pEGFP-N1 plasmid. Turbot were injected intramuscularly with the purified OmpU protein and the recombinant pEGFP-N1/ompU plasmid, respectively. The fish vaccinated with the purified OmpU protein were completely protected with a RPS of 100 % against pathogenic V. harveyi challenge. Efficient protection was also found in the pEGFP-N1/ ompU vaccinated group, with a RPS of 51.4%. Significant specific antibody responses were detected in the vaccinated turbot by indirect ELISA.In conclusion, a new outer membrane protein OmpU was cloned and expressed. Both OmpU protein and DNA vaccine showed good immune protections in turbot. The ompU was identified to be a new effective vaccine candidate and could be used as subunit vaccine and DNA vaccine design for disease control caused by pathogenic V. harveyi.