The protection of CpG ODNs and Yarrowia lipolytica harboring VP28 for shrimp Litopenaeus vannamei against White spot syndrome virus infection

The white spot syndrome is one of the most serious disease which has caused high mortalities and huge economic losses to shrimp culture. In the present study, the oral administrations with CpG ODNs and Yarrowia lipolytica harboring VP28 (rVP28-yl) as dietary supplement for shrimp Litopenaeus vannamei were conducted to evaluate their protective effects against WSSV. After feeding for 15 days, the cumulative mortality and the copy number of WSSV in CpG and rVP28-yl feeding shrimps were significantly lower when they were challenged by WSSV, compared with those in control shrimps (p < 0.05). The caspase-3 activity was suppressed in rVP28-yl feeding shrimps but ascended in CpG feeding shrimps after WSSV challenge. Besides, the PO activity in CpG feeding shrimps was significantly increased after feeding trial, and kept increasing post WSSV challenge (p < 0.05). While the increased NO production was observed both in CpG and rVP28-yl feeding shrimps after feeding trial and WSSV challenge. In addition, increased mRNA expression levels of STAT and Dicer were observed in CpG group post WSSV challenge. These results together indicated that oral feeding of CpG ODNs and rVP28-yl could enhance the innate non-specific immune responses especially antiviral immunity of shrimps in varying degrees, and increase their resistance against WSSV infection.