Binding of Infectious Hypodermal and Haematopoietic Necrosis Virus-Like Particles to Mannose Receptor Stimulates Antimicrobial Responses in Immune-Related Tissues of Peneaus vannamei.

Mannose receptor (MR) is a transmembrane protein and a type of pattern-recognition receptor (PRR) that plays a critical role in the immunity of mammals and fish. In this study, we examined the role of MR in binding with infectious hypodermal and haematopoietic necrosis virus-like particle (IHHN-VLP) and the downstream immune pathway that it triggers in the shrimp Peneaus vannamei. Upon IHHN-VLP challenge, transcripts of MR in P. vannamei (PvMR) increased significantly in all examined tissues, particularly those related to shrimp immunity, including hemocyte, hepatopancreas and gill tissues. Specifically, IHHN-VLP bound to the 34-kDa PvMR protein in shrimp-tissue extracts. Immunohistochemistry results of hemocytes showed that PvMR was initially localised on the plasma membrane but later internalised and dispersed throughout the cytoplasm after IHHN-VLP administration. Binding between IHHN-VLP and PvMR also induced significant upregulation of genes for the antimicrobial peptides (AMPs) penaeidin 3 and crustin, presumably to protect the shrimp against the viral infection. However, knocking down PvMR resulted in down-regulation of all immune-related genes examined. Overall, as an immune-related PRR, PvMR serves as a receptor for invading viruses, which then trigger the expression of AMPs. Strategic designs using PvMR could be developed to either block the interaction of native virus with the host cells or provoke its up-regulation to enhance shrimp immunity, which could open up opportunities to fight against IHHNV infection in shrimp.