Involvement of Microplastics in the Conflict Between Host Immunity Defense and Viral Virulence: Promoting the Susceptibility of Shrimp to WSSV Infection

Microplastics impact epidemics and outbreaksof viral diseasesand show an immunosuppressive effect on crustaceans. Polyvinyl chloridemicrospheres (PVC-MPs) as a potential viral vector enhance WSSV infectionvia inhibition of the innate immune response in shrimp. As the concentration of microplastics/microspheres (MPs)in coastaland estuarine regions increases, the likelihood of disease outbreaksand epidemics also rises. Our study investigated the impact of polyvinylchloride MPs (PVC-MPs) on white spot syndrome virus (WSSV) infectionin shrimp. The results revealed that PVC-MPs obviously increased WSSVreplication in vivo, leading to a high mortality rate among the larvaeand facilitating the horizontal transmission of WSSV. Furthermore,the data of WSSV loads detected together with qPCR, agarose gel electrophoresis,and flow cytometry approaches indicated that PVC-MPs could interactwith the virus to prolong survival and maintain the virulence of WSSVat different temperatures and pH values. In terms of host resistance,metabolomics and transcriptomics analysis demonstrated that exposureto PVC-MPs upregulated metabolic concentrations and gene expressionsassociated with phospholipid metabolism that were associated withinnate immunity responses. Particularly, PVC-MPs stimulated the synthesisof phosphatidylcholine (PC) and induced lipid peroxidation. The inhibitionof PC on Stimulator of Interferon Genes (STING) translocation fromthe endoplasmic reticulum to the Golgi apparatus reduces expressionof the innate immunity genes (IFN-like genes Vago4 and Vago5) regulatedby STING signaling pathways, resulting in a significant decrease inthe shrimp's resistance to WSSV infection. Notably, a recoveryoperation in which the exposed larvae were transferred to a MPs-freeaquatic environment led to decreased WSSV infectivity over time, indicatingthe restoration of antiviral properties in shrimp. Overall, thesefindings highlight that MPs promote shrimp susceptibility to WSSVin two aspects: host immune defense and viral virulence.