Adjuvant effects of poly I:C and imiquimod on the immunization of kuruma shrimp (Marsupenaeus japonicus) with a recombinant protein, VP28 against white spot syndrome virus

The adjuvant effects of poly I:C and imiquimod during immunization with a recombinant protein, rVP28 derived from white spot syndrome virus (WSSV) was investigated in kuruma shrimp (Marsupenaeus japonicus). Shrimps were injected intramuscularly with different doses of rVP28, poly I:C and imiquimod, and combined rVP28 + poly I:C or imiquimod, and challenged with WSSV. Expression of innate immune-related genes was examined in the heart and lymphoid organ of combined rVP28 + poly I:C or imiquimod immunized shrimps at 1, 3 and 7 days after WSSV challenge. Shrimps which received rVP28 + poly I:C and rVP28 + imiquimod had significantly higher survivals of 52 and 58%, respectively compared to the rVP28 alone or PBS injected control groups (P < 0.05). A significant up-regulation of innate immune-related genes, such as Rab7, lysozyme, penaeidin, crustin, Toll and TNF was noticed in combined rVP28 + poly I:C or imiquimod immunized shrimps. Our results indicate that injection administration of poly I:C or imiquimod + sub-unit protein (rVP28) provides a significant protection and induces immune response in kuruma shrimps against WSSV. Therefore, poly I:C and imiquimod have potentials to be used as adjuvants or immunostimulants in shrimp immunization. Statement of relevance: Major contributors to economic losses in shrimp aquaculture are viral diseases, of which white spot syndrome virus (WSSV) is the most important one due to its rapid spread and economic impact. In this paper, we present an immunization method towards prevention of WSSV disease in kuruma shrimp using adjuvants such as poly I:C or imiquimod along with a sub-unit protein (rVP28). (C) 2015 Elsevier B.V. All rights reserved.