[Influence of white spot syndrome virus envelope protein Vp28 expressed in silkworm (Bombyx mori) pupae on immune response in Procambarus clarkii].

Silkworm (Bombyx mori) pupae infected with recombinant baculovirus HyNPV-Vp28 were made vaccine,which was mixed with feed at a ratio of 2% (w/w). Procambarus clarkii were orally administered. The results of immune analysis showed that the phagocytic percent and phagocytic index of hemocytes increased significantly when compared the rVp28 treatment with control treatments (P < 0.05). Compared with control groups,the antibiotic activity, bacteriolytic activity and activities of phenoloxidase, superoxide peroxidation in serum in the rVp28 group were greatly increased (P < 0.05). The activities of acid phosphatase and alkaline phosphatase in serum and hepatopancrease tissues in rVp28 treatment were significantly higher than control treatments (P < 0.05). Vaccination with rVp28 showed that the cumulative survival,compared with control treatments, was significantly higher (P < 0.05). An oral challenge on the 35th day post-vaccination was followed,PRP values were then 64.29% and 58.33%, respectively. The epidermal cells of stomach, midgut, hepatopancreas, gill and epithelial tissue of moribund crayfishes were histologically characterized by hypertrophied nuclei and highly stained cells, but there was normal structure in the survivors-vaccinated after WSSV challenge. WSSV DNA was detected by PCR and Dot-blot with DIG-labeled DNA probe. The positive results were observed in stomach, hepatopancreas and gut of the moribund crayfishes and survivors in control groups, while negative reaction was observed in the tissues of survivors in rVp28 group. Vp28 expressed in silkworm (Bombyx mori) pupae played a role in improving the immune function of crayfish.