Expression kinetics of β-integrin in Chinese shrimp (Fenneropenaeus chinensis) hemocytes following infection with white spot syndrome virus

Our previous study has demonstrated that an integrin β subunit of Chinese shrimp (Fenneropenaeus chinensis) (FcβInt) involved in WSSV infection. In order to further elucidate the potential role of the FcβInt in the WSSV infection, expression response of FcβInt to WSSV infection in shrimp hemocytes was investigated after intra-muscular injection with the virus. Following time-course hemocytes sampling, the expression variation of FcβInt in hemocytes was examined by flow cytometric immunofluorescence assay (FCIFA) and enzyme linked immunosorbent assay (ELISA) using the monoclonal antibody (Mab) 2C5 against FcβInt, which was successfully produced with recombinant partial FcβInt and exhibited binding to a 120 kDa hemocyte protein. Meanwhile, the dynamic state of FcβInt mRNA level and WSSV copies in hemocytes were determined by quantitative real-time PCR. The result of FCIFA showed that FcβInt was mainly expressed on the semi-granular and granular cells, which was down-regulated at 6 h post infection (p.i.), and significantly increased to the peak level at 12 h p.i., then decreased to the control level by 24 h. However, FcβInt on the hyaline cells was lowly expressed and didn't show active response to the viral infection. The variation of FcβInt concentrations in total hemocytes determined by ELISA was roughly in accordance with the changing tendency of FcβInt expressed on the semi-granular and granular cells. FcβInt mRNA level in total hemocytes was significantly up-regulated to the peak level at 12 h p.i. Moreover, the number of WSSV copies in hemocytes began to exhibit a significant increase at 24 h p.i. The present study demonstrated that WSSV infection would induce a differential regulation of FcβInt expression in different type hemocytes, which provided valuable evidences for the close correlation between FcβInt and WSSV infection.