Inhibiting viral replication and prolonging survival of hosts by attenuating stress responses to viral infection.

Viruses are obligate intracellular parasites relying on host cells to obtain biosynthetic precursors and energy to successfully infect the host. The metabolic profile of the host cell is known to be altered in response to viral infection to satisfy the resources demanded during viral replication. Previous data of ours showed that white spot syndrome virus (WSSV) elicited in a crustacean host (Procambarus clarkii) a rapid and long-lasting release of crustacean hyperglycemic hormone (CHH), a well-known carbohydrate-regulating and stress response-mediating endocrine hormone. Therefore, the WSSV-enhanced release of CHH could be responsible at least in part for the metabolic alterations in the WSSV-challenged host. To investigate the possible metabolic roles of CHH in the host-parasite interaction, we studied whether silencing CHH gene expression could inhibit WSSV propagation in tissues and reduce the mortality of the WSSV-infected animals. Data presented in this study showed that CHH gene silencing indeed resists the WSSV infection. Injection of CHH dsRNA at the dosage of 140 μg/g BW caused significant decreases of viral copy number in tissues of WSSV-infected host, particularly showing a pronounced effect in the endodermal tissues (including hepatopancreas and gastrolith disk). Furthermore, results from the cumulative mortality showed that the treatment of CHH dsRNA delayed death from WSSV. Injection of CHH dsRNA at the dosages of 70, 17, and 10 μg/ g BW significantly extended the mean survival time. Together, this study concludes that the silencing of the CHH gene does have an inhibitory effect on the replication of the white spot syndrome virus and can assist the host to mitigate the invasion of WSSV, through attenuating CHH-mediated stress responses.