Oral Administration of CpG ODNs and Yarrowia lipolytica Harboring VP28 in Farm Ponds to Protect Shrimp From White Spot Syndrome Virus Infection

Abstract:

Frequent outbreaks of viral and bacterial diseases have caused severe economic loss in shrimp farming that has been an important part in aquaculture. The white spot syndrome is one of the most harmful diseases in shrimp culture. It is crucial to develop novel strategies that efficiently protect shrimp against WSSV. In this study, we performed oral administration of diet supplemented with CpG ODNs prepared with large-scale fermentation and Yarrowia lipolytica harboring VP28 (VP28-yl) to farmed Litopenaeus vannamei. After 30-day feeding we challenged the shrimp with WSSV to evaluate the protective effects of CpG ODN and VP28-yl. Shrimp fed with CpG ODN displayed a relative weight gain of (65.8±7.8)% (P<0.05), indicating that CpG ODN might promote the growth of shrimp. After the WSSV challenge, the copies of WSSV in shrimp fed with CpG ODN and VP28-yl were both significantly less compared to the control (P<0.05), and the RPS were 26.7% and 36.7% respectively. The respiratory burst level of shrimp fed with CpG ODN was increased after feeding trial and WSSV challenge. After the WSSV challenge, there was a gradual increase in the apoptosis of haemocytes in the control shrimp. In the contrast, the apoptosis of haemocytes in shrimp fed with VP28-yl was significantly suppressed. Moreover, the expression of STAT mRNA in shrimp fed with CpG ODN and VP28-yl was significantly increased post the WSSV challenge (P<0.05), and there was an opposite trend in the control group (P<0.05). These results suggested that oral administration of CpG ODN and VP28-yl could enhance the antiviral immunity against WSSV, and thus help control viral diseases. These two immunoactive substances could be potentially new therapies in shrimp aquaculture industry.