The 14-3-3 epsilon (14-3-3ε) is a member of the 14-3-3-protein family claimed to play important roles in many biological processes. In this study, two alternative 14-3-3 epsilon mRNAs, designated as 14-3-3EL and 14-3-3ES were identified from the shrimp L. vannamei. The 14-3-3EL isoform contains an insertion of 48 nucleotides by intron retention in the pre-mRNA of 14-3-3ε. While the 14-3-3ES occurred after being fully spliced. Using the yeast two hybrid method, the pattern of dimer formation by the two alternative 14-3-3ε isoforms revealed that the shrimp 14-3-3ε formed both homodimers and heterodimers. Both 14-3-3ε transcript variants were constitutively expressed in all shrimp tissues tested but the level of the 14-3-3ES isoform was always lower. However, after white spot syndrome virus (WSSV) infection, the expression level of the two transcript variants changed. At 48 h after infection, expression of 14-3-3EL mRNA increased significantly in the gill and muscle tissue whereas the expression 14-3-3ES increased only in muscle. It was of interest that in the lymphoid organ, there was a significant down-expression of both transcript variants. From these results we suggest that 14-3-3EL and 14-3-3ES might be related to different cellular processes that are modulated during virus infection.

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is involved in the adaptive immune response via its effects on major histocompatibility complex (MHC)-restricted antigen presentation. In addition to antigen presentation, GILT exerts its antiviral activity by reducing disulfide bonds in proteins involved in viral infection and assembly, thereby inhibiting viral envelope-mediated infection and viral progeny production. In black tiger shrimp, Penaeus monodon GILT (PmGILT) was cloned and characterized, and found to be involved in the shrimp innate immune response and to exert neutralizing activity against white spot syndrome virus (WSSV) infection. However, the anti-WSSV mechanism of PmGILT in the shrimp innate immune response has not been defined. To explore the anti-WSSV activity of PmGILT, a yeast 2-hybrid (Y2H) assay was performed to identify WSSV proteins targeted by PmGILT. The assay revealed 4 potential PmGILT-interacting WSSV proteins: WSSV002, WSSV164, WSSV189, and WSSV471. Three of these 4 WSSV proteins (WSSV002, WSSV164 and WSSV189) were successfully produced and confirmed to interact with PmGILT in in vitro pull-down assays. WSSV189 and WSSV471 were previously identified as structural proteins, whereas WSSV164 is an immediate -early protein which has anti-melanization activity, and WSSV002 is an unknown. Because of the thiol reductase activity of PmGILT, WSSV164 and WSSV189, both of which are cysteine-containing WSSV proteins, were chosen for disulfide bond reduction assays. PmGILT reduced intrachain disulfide bonds in both WSSV proteins, suggesting that PmGILT exerts its anti-WSSV activity via its thiol reductase activity to disrupt the WSSV protein complex and restore the melanization activity of PmproPO1 and PmproPO2.