Study Of Immune Response After Vaccine Trials Using Formalin-Killed Cells Of Streptococcus Agalactiae And Streptococcus Iniae In Oreochromis Niloticus

Streptococcal spp.is one of the most important pathogens in aquaculture.Streptococcus agalactiae(S.agalactiae)and Streptococcus iniae(S.iniae)disease caused by the widespread in the world aquaculture industry,which has brought huge economic losses.Currently,disinfectants,antibiotics and other chemicals are still main way to prevent and treat bacterial disease caused by Streptococcal,but there are many problems happen such as drug residues,bacterial resistance in aquaculture food.Bacterial inactivated vaccine is a biological product prepared by killing pathogens from formalin.Streptococcus formalin-killed vaccine could make tilapia produce antibodies toxicity neutralization,remove pathogenic microorganisms and the immune response,and bring about the humoral immunity,infection of extracellular Streptococcus has a better immune protection.This work were to determine whether specific antibodies play an important role in immunity against streptococcal and provide cross-protection.The vaccines were prepared from formalin-killed cells(FKC)and via intraperitoneal(IP)injection.We evaluated Immune protection via to detecting serum antibody levels and important cytokines,for example,interleukin-1(IL-1),Caspase-3(C-3),Tumor Necrosis Factor(TNF),Interferon(IFN),and non-specific immunity parameters like acid phosphatase(ACP),alkaline phosphatase(AKP),Superoxide Dismutase(SOD),Lysozyme(LZM).Our results indicated that vaccine groups had significantly increased(P<0.05)specific antibody levels over control at 14 days postsecondary vaccination(PSV).We found that vaccine groups had significantly(P<0.05)increased specific antibody levels over control at 7 days post-challenge(PC).A significant(P<0.05)up-regulation of mRNA expression for C-3,TNF,IFN in head kidney and IL-1,TNF,IFN in post kidney.C-3 and IFN expression in the vaccine trials group was significantly(P<0.05)increased in spleen.A highly significant(P<0.05)of mRNA expression for IL-1,C-3,IFN in head kidney and C-3?TNF in spleen.In this study,S.iniae and S.agalactiae FKC vaccine groups ACP,SOD,and LZM were significantly higher(P<0.05)than control.The vaccine trials group showed significantly higher(P<0.05)than control in survival rate.Our study suggested that S.agalactiae and S.iniae FKC vaccine provided excellent protection in Oreochromis niloticus with the relative percent survival(RPS)93.3%and 92.9%,respectively,and provided cross-protection against bacterium infection.Moreover,S.agalactiae FKC vaccine provided higher cross-protection against S.iniae infection(P<0.05).