尼罗罗非鱼IgM抗体免疫应答水平与抗病能力的关联性及遗传力评估OACHSSCD

[Objective]This study aims to elucidate the correlation between specific IgM antibody levels and resistance to Streptococcus agalactiae infection in tilapia(Oreochromis niloticus)after immunization,and estimate the genetic parameters of this disease resistance trait,and evaluate its poten-tial as an indicator for disease-resistant breeding.[Method]Three populations of tilapia(Huadu,Panyu,and Hainan populations)were immunized by immersion with an inactivated S.agalactiae vac-cine,followed by a booster immunization at 15 days post-initial immunization(dpi).The levels of serum-specific IgM antibody were detected prior to immunization(0 d)and at 7,14,21,28,60,and 90 dpi to reveal its temporal dynamics.The correlations between the peak levels of serum-specific IgM antibody and relative percent survival(RPS),survival status and blood bacterial load following artifi-cial challenge with S.agalactiae were analyzed.Multiple full-sib families were constructed,and serum-specific IgM antibody levels of offspring from each family after immunization were measured.The vari-ance components and heritability were estimated using restricted maximum likelihood(REML),and the individual breeding values were predicted by best linear unbiased prediction(BLUP).[Result]The serum-specific IgM antibody levels in tilapia peaked(from 68.07 to 91.73 μg/mL)at 7 days after the second immunization and persisted at a high mass concentration(>54.99 μg/mL)for 28 days.Tilapia populations with higher post-immunization IgM antibody levels exhibited higher relative percent sur-vival(RPS).Surviving individuals after the bacterial challenge showed significantly higher IgM anti-body response levels than those that died(P<0.05),and individuals with higher IgM antibody response levels had a longer survival time after the challenge.In non-immunized tilapia subjected to bacterial challenge,serum-specific IgM levels were extremely significantly negatively correlated with blood S.agalactiae load(P<0.01).Genetic analysis based on 24 full-sib families revealed that the heritability of the IgM antibody immune response trait in tilapia was 0.44.[Conclusion]IgM antibody immune response level in tilapia is positively correlated with its resistance to S.agalactiae infection and repre-sents a highly heritable trait.The IgM antibody immune response level can serve as an important candi-date trait for disease-resistant breeding in tilapia,providing a theoretical foundation for developing new strains with enhanced immunocompetence and disease resistance.