Elsevier

Fish & Shellfish Immunology

Volume 85, February 2019, Pages 66-77
Fish & Shellfish Immunology

Full length article
Vaccination of carp against SVCV with an oral DNA vaccine or an insect cells-based subunit vaccine

https://doi.org/10.1016/j.fsi.2018.03.028Get rights and content
Under a Creative Commons license
open access

Highlights

  • Alginate encapsulation effectively delivers intact plasmid and protein antigens to the intestine.

  • Oral DNA vaccination of carp, even at high plasmid doses, is not yet effective against SVCV infection.

  • Addition of the mucosal adjuvant LTB does not improve efficacy of oral DNA vaccination against SVCV.

  • Transmembrane SVCV-G protein is expressed at high levels on the surface of insect cells.

  • An SVCV-G-based subunit vaccine is not yet effective when administered orally or by injection.

Abstract

We recently reported on a successful vaccine for carp against SVCV based on the intramuscular injection of a DNA plasmid encoding the SVCV glycoprotein (SVCV-G). This shows that the intramuscular (i.m.) route of vaccination is suitable to trigger protective responses against SVCV, and that the SVCV G-protein is a suitable vaccine antigen. Yet, despite the general success of DNA vaccines, especially against fish rhabdoviruses, their practical implementation still faces legislative as well as consumer's acceptance concerns. Furthermore, the i.m. route of plasmid administration is not easily combined with most of the current vaccination regimes largely based on intraperitoneal or immersion vaccination. For this reason, in the current study we evaluated possible alternatives to a DNA-based i.m. injectable vaccine using the SVCV-G protein as the vaccine antigen. To this end, we tested two parallel approaches: the first based on the optimization of an alginate encapsulation method for oral delivery of DNA and protein antigens; the second based on the baculovirus recombinant expression of transmembrane SVCV-G protein in insect cells, administered as whole-cell subunit vaccine through the oral and injection route. In addition, in the case of the oral DNA vaccine, we also investigated the potential benefits of the mucosal adjuvants Escherichia coli lymphotoxin subunit B (LTB). Despite the use of various vaccine types, doses, regimes, and administration routes, no protection was observed, contrary to the full protection obtained with our reference i.m. DNA vaccine. The limited protection observed under the various conditions used in this study, the nature of the host, of the pathogen, the type of vaccine and encapsulation method, will therefore be discussed in details to provide an outlook for future vaccination strategies against SVCV.

Keywords

SVCV glycoprotein
Alginate encapsulation
Insect cells
Baculovirus
DNA vaccine

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