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Apoptosis inducing factor (AIF) and cytochrome c (CYC) are two mitochondrial apoptogenic factors. In the present study, the cDNA sequences of AIF ( Lv AIF) and CYC ( Lv CYC) were cloned from Pacific white shrimp, Litopenaeus vannamei . The Lv AIF was 1664 bp, including a 5’-terminal untranslated region (UTR) of 154 bp, an open reading frame (ORF) of 1323 bp encoding a polypeptide of 440 amino acids (aa) and a 3′ UTR of 187 bp. The Lv CYC was 582 bp, including a 50 bp 5′ UTR, a 315 bp ORF encoding for 104 aa, and a 217 bp 3′ UTR. The deduced protein of Lv AIF contained a conserved Pyr_redox and AIF_C domain at the N-terminal and the predicted Lv CYC included a conservative cytochrome_C domain, respectively. Phylogenetic analysis revealed that Lv AIF belonged to AIF1 subfamily and showed a close relationship with AIF1 from vertebrates and Lv CYC showed the closest relationship with its counterparts from shrimp Marsupenaeus japonicus . Tissue expression profiles showed that both Lv AIF and Lv CYC existed in most tissues, with the most predominant expression of Lv AIF in intestine, then followed muscle and the weakest expression in gill. The highest expression of Lv CYC was detected in muscle, and the weakest expression was in hemocytes. Additionally, after white spot syndrome virus (WSSV) infection, the significant up-regulation of Lv AIF, Lv CYC and caspase 3 transcripts and the increase of pro-caspase 3 and active-caspase 3 protein were detected at most time points ( P < 0.05). However, all of the three genes down-regulated in hemocytes in the early stage after WSSV infection. WSSV proliferation and shrimp mortality showed a time-dependent manner and the production of ROS in hemocytes were significantly increased at 6 and 24 h after infection. Our results showed that the apoptotic genes AIF, CYC and caspase 3 might play crucial roles in hepatopancreas, however, the production of ROS in hemocytes might be important in shrimp defense against WSSV infection. [ABSTRACT FROM AUTHOR]

Envelope protein VP28 has been suggested as a candidate vaccine component to evoke a better protection against white spot syndrome virus ( WSSV). We have reported that Bacillus subtilis spores harbouring VP28 (rVP28-bs) can specifically protect shrimp against WSSV. However, the mechanism that supports the production of unique molecules induced by rVP28-bs to trigger specific immunity is originally unknown. It has recently been suggested that Dscam (Down syndrome cell adhesion molecule) plays an essential role in the alternative adaptive immunity of invertebrates. In this study, we compared the diversity of Litopenaeus vannamei Dscam (LvDscam) variable regions by different antigens immunization. A total of 13, 15 and 11 expressed alternative sequences were identified for N-terminal Ig2, N-terminal Ig3 and the entire Ig7 domain, respectively. More than half of the unique variants (16 out of 22) were found in the Ig2/Ig3 domains. Further analysis of the interaction between VP28 and unique Ig2/Ig3 variants was confirmed by both yeast two-hybrid and GST pull-down approach. We also found that the percentage of haemocytes phagocytosing WSSV was significantly higher ( P < 0.001) in the shrimp injected with control-siRNA (43.8 ± 2.2) than those with Dscam-siRNA (11.3 ± 5.4) in the rVP28-bs groups. With Dscam-siRNA injection, survivorship significantly decreased ( P < 0.001) in the rVP28-bs group after WSSV challenge. Our data suggested that LvDscam-mediated pathway may be involved in the specific immune response of shrimp against WSSV induced by rVP28-bs. [ABSTRACT FROM AUTHOR]