Cellular and Proteomic Characterization of the Innate Immune Response in Bat Stars (Patiria miniata)

Abstract

Bat star populations on the west coast have been declining due to the Sea Star Wasting Syndrome. This tissue‐decaying epidemic involves a viral infection and skin lesions leading to disintegration in sea stars. The mechanisms causing decay in the symptomatic individuals are still unknown. We considered the immune response in bat stars after the appearance of skin lesions to determine how immune cells react and which proteins are expressed throughout the viral infection and tissue disintegration. We hypothesized that the viral infection is met with an increase in immune cell concentration and phagocytic activity, and an increase in the secretion of immune‐ and stress‐response related proteins into the coelomic fluid in activated defensive pathways. The morphology, behavior, and concentration of the immune cells per mL of coelomic fluid in healthy and wasting bat stars were compared by extracting coelomic fluid and staining nuclei, photographing the cells, and counting them. Immune cells were extracted at healthy and middle time points with no visible lesions, and at an endpoint once visible lesions were present; the cells were counted and incubated with fluorescent bacteria. Phagocytes, cells that engulf invading pathogenic cells, were found in higher cell concentrations after viral infection and the appearance of lesions, showing higher levels of activity and consuming more fluorescent bacteria. The reactions of the cells to these pathogens were observed in coelomic fluid from healthy and wasting sea stars. From the coelomic fluid samples taken throughout the progression of the disease in several individual sea stars, LC/MS/MS analysis and NCBI BLAST characterization of the proteins present showed dynamic abundance patterns in secreted proteins related to cell signaling, stress, and immune response. We are attempting a more thorough characterization of the proteins involved in the immune reaction to better define the defense mechanisms occurring in the bat stars during the response to the viral challenge. The changes in abundance of certain proteins may give clues about the patterns of disintegration occurring at the cellular level and the pathways involved in the tissue disintegration. We may also be able to identify novel antimicrobial or anti‐viral molecules of pathways, with potential for future use in tissue preservation.Support or Funding InformationCOAST Grant, CSULB 2015 Graduate Summer Research Fellowship.