Resistance to white spot syndrome virus in the European shore crab is associated with suppressed virion trafficking and heightened immune responses

Abstract

IntroductionAll decapod crustaceans are considered potentially susceptible to White Spot Syndrome Virus (WSSV) infection, but the degree of White Spot Disease (WSD) susceptibility varies widely between species. The European shore crab Carcinus maenas can be infected with the virus for long periods of time without signs of disease. Given the high mortality rate of susceptible species, the differential susceptibility of these resistant hosts offers an opportunity to investigate mechanisms of disease resistance.MethodsHere, the temporal transcriptional responses (mRNA and miRNA) of C. maenas following WSSV injection were analysed and compared to a previously published dataset for the highly WSSV susceptible Penaeus vannamei to identify key genes, processes and pathways contributing to increased WSD resistance.ResultsWe show that, in contrast to P. vannamei, the transcriptional response during the first 2 days following WSSV injection in C. maenas is limited. During the later time points (7 days onwards), two groups of crabs were identified, a recalcitrant group where no replication of the virus occurred, and a group where significant viral replication occurred, with the transcriptional profiles of the latter group resembling those of WSSV-susceptible species. We identify key differences in the molecular responses of these groups to WSSV injection.DiscussionWe propose that increased WSD resistance in C. maenas may result from impaired WSSV endocytosis due to the inhibition of internal vesicle budding by dynamin-1, and a delay in movement to the nucleus caused by the downregulation of cytoskeletal transcripts required for WSSV cytoskeleton docking, during early stages of the infection. This response allows resistant hosts greater time to fine-tune immune responses associated with miRNA expression, apoptosis and the melanisation cascade to defend against, and clear, invading WSSV. These findings suggest that the initial stages of infection are key to resistance to WSSV in the crab and highlight possible pathways that could be targeted in farmed crustacean to enhance resistance to WSD.

Experimental Infection Models and Their Usefulness for White Spot Syndrome Virus (WSSV) Research in Shrimp

“…WSSV's reported host range currently includes seventy-three species of shrimps, crabs, lobsters, freshwater shrimp and crayfish, brine shrimp, copepods, and polychaetes [93,152,[185][186][187][188][189][190][191][192][193][194][195][196][197][198][199], but the degree of species susceptibility to WSSV varies widely [200]. Penaeid shrimp species are highly susceptible and WSSV infection often results in high mortality.…”

Macroalgae Improve the Growth and Physiological Health of White Shrimp (Litopenaeus vannamei)

“…Phagocytosis is regarded as a requisite part of innate immunity, which is initiated by recognizing the target particle and binding it to the phagocyte, then the immunerelated genes such as dynamin involved in the control of endocytosis via clathrin-mediated endocytosis [26,[52][53][54]. It is reported that the phagocytic activity of Fenneropenaeus indicus was higher in seawater containing brown algae (Sargassum glaucescens) [55].…”