IL22 and infection: The results showed that three cytokines, including the Fas receptor (Fas), platelet factor 4 (PF4) and interleukin-22 (IL-22), were significantly upregulated in WSSV-infected shrimp at 6 h post-infection compared with the control (PBS) (Fig 1B), suggesting that these cytokines might play positive regulatory roles in the shrimp immune response against the WSSV infection.