Abstract
During viral infection in vertebrates, cytokines play important roles in the host defense against the virus. However, the function of cytokines in invertebrates has not been well characterized. In this study, shrimp cytokines involved in viral infection were screened using a cytokine antibody microarray. The results showed that three cytokines, the Fas receptor (Fas), platelet factor 4 (PF4) and interleukin-22 (IL-22), were significantly upregulated in the white spot syndrome virus (WSSV)-challenged shrimp, suggesting that these cytokines played positive regulatory roles in the immune response of shrimp against the virus. Further experiments revealed that PF4 had positive effects on the antiviral immunity of shrimp by enhancing the shrimp phagocytic activity and inhibiting the apoptotic activity of virus-infected hemocytes. Therefore, our study presented a novel mechanism of cytokines in the innate immunity of invertebrates.
Highlights
Shrimp, one of the most important species in aquaculture, is affected worldwide by diseases, notably those caused by white spot syndrome virus (WSSV)
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
The results showed that the WSSV levels were significantly decreased by PF4 at different concentrations in shrimp infected with WSSV at 12 h to 24 h post-infection compared with the controls (Fig 2A)
Summary
One of the most important species in aquaculture, is affected worldwide by diseases, notably those caused by white spot syndrome virus (WSSV). It is well known that the disease resistance of shrimp, as an invertebrate, is entirely dependent on the innate immune system, including cellular and humoral responses [1]. The innate immune system is the first line of inducible host defense against bacterial, fungal and viral pathogens [2]. Most of shrimp die because of the WSSV infection, some of the WSSV-infected shrimp survive, indicating that shrimp possess immune factors responsible for the shrimp resistance against the virus invasion. Small interfering RNAs (siRNAs) and microRNAs (miRNAs) have been found to mediate the antiviral defense in shrimp [8,9,10,11]. Up to PLOS ONE | DOI:10.1371/journal.pone.0162954 September 15, 2016
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