Fish mass immunization against virus with recombinant "spiny" bacterins.

Area of Science:

• Veterinary Immunology
• Fish Vaccinology
• Molecular Biology

Background:

• Recombinant bacterins displaying viral antigens are explored for fish vaccination.
• Prokaryotic expression systems offer potential environmental advantages over eukaryotic systems.
• Surface display of viral fragments on bacteria can enhance immunogenicity.

Purpose of the Study:

• To evaluate the immunogenicity of novel "spiny" bacterins (spinycterins) expressing a Cyprinid herpesvirus 3 fragment (frgII_CyHV3).
• To investigate the role of bacterial membrane anchor-motifs in surface expression and immune response.
• To assess ultrasound as a non-invasive delivery method for spinycterins in fish.

Main Methods:

• Genetic fusion of five bacterial membrane anchor-motifs (Nmistic, Mistic, NTD, YAIN, YBEL) to frgII_CyHV3.
• Expression and surface enrichment analysis of recombinant proteins in *E. coli* using ELISA, immunofluorescence, and flow cytometry.
• Immunization of carp and zebrafish with spinycterins, followed by antibody detection via ELISA and assessment of ultrasound delivery.

Main Results:

• Fusion of anchor-motifs, particularly YBEL, enhanced *E. coli* outer membrane expression of frgII_CyHV3.
• Spinycterins induced detectable anti-frgII_CyHV3 specific antibodies in immunized carp and zebrafish.
• The YBEL construct demonstrated the highest immunogenicity in both fish species.
• Ultrasound facilitated non-invasive delivery of spinycterins.

Conclusions:

• Spinycterins utilizing prokaryotic expression plasmids are effective in presenting viral antigens for fish immunization.
• The YBEL anchor-motif fusion is a promising strategy for developing potent fish vaccines.
• Ultrasound-mediated delivery offers a practical, non-invasive method for mass fish vaccination.
• Spinycterins represent a safer, environmentally conscious alternative to DNA vaccination.