The immune response of Caspase-3 gene in infectious hypodermal and hematopoietic necrosis virus (IHHNV) infection of Litopenaeus vannamei

Abstract

The pathogenicity of infectious hypodermal and hematopoietic necrosis virus (IHHNV) in litopenaeus vannamei (L. vannamei) is closely related to the age and size of the host, with juveniles being more susceptible to IHHNV infection and exhibiting higher pathogenicity. In our previous research, transcriptome sequencing results revealed a significant downregulation of the Caspase-3 (LvCAP-3) gene in juveniles compared to adults. Based on these findings, we hypothesize that the LvCAP-3 gene plays an immunological role in the defense against IHHNV in L. vannamei. To validate this hypothesis, we analyzed the differential expression of the LvCAP-3 gene in various tissues (pleopods, muscles, gills, intestine, hepatopancreas) of L. vannamei using Real-time quantitative PCR (qPCR), and investigated the impact of LvCAP-3 gene interference using RNA interference (RNAi) technology on IHHNV viral load. The research findings indicated that the LvCAP-3 gene was expressed in all 5 tissues mentioned above, with the highest expression in hepatopancreas and the lowest expression in pleopods. L. vannamei injected with IHHNV showed an increasing viral load from 24 to 120 h, accompanied by an upregulation of LvCAP-3 gene expression. Furthermore, the interference of the LvCAP-3 gene resulted in a higher IHHNV viral load in L. vannamei injected with IHHNV compared to the control group. In conclusion, interference with the LvCAP-3 gene makes L. vannamei more susceptible to IHHNV infection. It can be deduced that the higher susceptibility of juvenile shrimp to IHHNV associated with lower expression levels of the LvCAP-3 gene.