Protective effects of inactivated SPIV vaccine in sea perch (Lateolabrax japonicas) by intraperitoneal injection and immersion immunization.

Sea perch is one of the most important fish species farmed in China. However, the frequent outbreak of viral diseases induced by sea perch iridovirus (SPIV) always caused high mortality and heavy economic losses in sea perch aquaculture. Up to now, no effective countermeasures against SPIV infection have been established. Here, the inactivated SPIV combined with ISA 763B VG (SPIV/763B) or IMS 1312 VG (SPIV/1312) were used for injection and immersion immunization, respectively. The potential immunoprotective effects of vaccines against SPIV infection were evaluated after the safety test of vaccines. Following challenge with SPIV, fish vaccinated with SPIV/763B or SPIV/1312 by injection or immersion exhibited high protection efficacy against SPIV compared to PBS group, with a relative percent survival (RPS) of 81.7 % and 63.7 %, respectively. The vaccinated groups also showed a significant reduction in both viral load and mRNA levels of viral genes in different tissues. Additionally, the number of basophilic hypertrophied cells induced by SPIV was dramatically decreased in the vaccinated groups. Moreover, the specific serum antibody was detected from 7 days post-vaccination and the transcription levels of innate immune-related genes (IRF3, IRF7, ISG15, Mx-2, MyD88) and adaptive immune-related gene (IgM) were differently up-regulated in SPIV/763B or SPIV/1312 vaccinated groups compared to the control group. Taken together, our results indicated that the combination of inactivated SPIV with different adjuvants could provide effective protection against SPIV infection in sea perch via activation of both humoral and cell-mediated immune responses.