Construction and immunological evaluation of live vector vaccine based on attenuated Listeria monocytogenes vector against Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is considered to be one of the most threatening aquatic pathogens in aquaculture. Therefore, the development of an effective vaccine is crucial to prevent and control it. In this report, we iden-tified the target antigen VP2309 with strong immunogenicity from four outer membrane proteins of V. parahaemolyticus. Furthermore, the live vector vaccine strain EGD-e delta actA/inlB-VP2309 based on attenuated Listeria monocytogenes (Lm) was successfully constructed, consisting of secretory signal peptide of P60 protein, strong promoter Plmo2196 of Lm, and VP2309. It was able to express and secrete VP2309 efficiently. However, its expression retarded the growth of the host strain. The results of immune protection evaluation showed that both EGD-e delta actA/inlB and EGD-e delta actA/inlB-VP2309 strains reduced the mortality of zebrafish infected with V. parahaemolyticus. However, the vaccine strain carrying the VP2309 did not show better immune protection than the empty vector. Thus, we found that the attenuated Lm vector could offer a certain immune protection to zebrafish infected with V. parahaemolyticus, and is a potential vaccine vector that can be used in fish vaccine.