title: A novel "in-feed" delivery platform applied for oral DNA vaccination against IPNV enables high protection in Atlantic salmon (Salmon salar).
abstract: DNA vaccination has emerged as a promising tool against infectious diseases of farmed fish. Oral delivery allows stress-free administration that is ideal for mass immunization and of paramount importance for infectious pancreatic necrosis (IPN) and other viral disease that affect young salmonids and cause economic losses in aquaculture worldwide.
  
  
  
  We describe the development and in vivo assessment of an "in-feed" formulation strategy for oral immunization with liposomal DNA vaccines, by delivering a vaccine construct coding for an immunogenic region of the VP2 capsid protein. A challenge against IPNV was carried out to determine the vaccine efficacy, by comparing the mortality of pre-smolt Atlantic salmons immunized and non-immunized with the oral vaccine. The antibody response (ELISA) and hematological parameters after immunization were examined, as well as the vaccine effect on the growth and internal structures of fry salmons (histological analysis). The vaccine distribution in the experimental tank after oral administration was investigated by HPLC and PCR amplification.
  
  
  
  The oral vaccine induced detectable levels of VP2-specific antibodies and conferred significant protection following IPNV challenge, with relative percent survivals (RPS) of 58.2%, for single dose (1mgpDNA/kgfish⋅d), and 66% for double dose (2mgpDNA/kgfish⋅d). We further provide evidence in favour of the vaccine safety to fish and demonstrated absence of pDNA in the tank water, but presence of vaccine residues in faeces and unconsumed feed sediments (solid wastes).
  
  
  
  The delivery platform for liposomal DNA vaccination via feed was successfully proved against IPNV in Atlantic salmon, showing the oral vaccine to be immunogenic and safe for fish, and providing significant protection after oral administration. The "in-feed" technology for oral DNA vaccination holds potential to be applied against IPNV and other pathogens that currently threaten the aquaculture worldwide.
authors.affiliation: Bioinnovation Ltd, Providencia, Santiago 7501265, Chile.
authors.forename: Miguel
authors.initials: M
authors.lastname: Reyes
authors.affiliation: Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Lientur 1457, Concepción 4080871, Chile.
authors.forename: Cesar
authors.initials: C
authors.lastname: Ramírez
authors.affiliation: Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Lientur 1457, Concepción 4080871, Chile.
authors.forename: Ivan
authors.initials: I
authors.lastname: Ñancucheo
authors.affiliation: Bioinnovation Ltd, Providencia, Santiago 7501265, Chile.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Villegas
authors.affiliation: Facultad de Ingeniería, Universidad Autónoma de Chile, Av. Pedro de Valdivia 425, Providencia, Santiago 7500000, Chile.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Schaffeld
authors.affiliation: Bioinnovation Ltd, Providencia, Santiago 7501265, Chile.
authors.forename: Luis
authors.initials: L
authors.lastname: Kriman
authors.affiliation: Cargill Innovation Center, Camino a Pargua, Km 57, Colaco Km. 5, Calbuco, Chile.
authors.forename: Javier
authors.initials: J
authors.lastname: Gonzalez
authors.affiliation: Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Lientur 1457, Concepción 4080871, Chile. Electronic address: patricio.oyarzun@uss.cl.
authors.forename: Patricio
authors.initials: P
authors.lastname: Oyarzun
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000284:Administration, Oral; D000825:Animal Structures / Q000473:pathology; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D018175:Birnaviridae Infections / Q000473:pathology / Q000517:prevention & control / Q000662:veterinary*; D004337:Drug Carriers / Q000008:administration & dosage; D004797:Enzyme-Linked Immunosorbent Assay; D005393:Fish Diseases / Q000473:pathology / Q000517:prevention & control*; D018061:Infectious pancreatic necrosis virus / Q000276:immunology*; D008081:Liposomes / Q000008:administration & dosage; D020317:Salmo salar; D016019:Survival Analysis; D016896:Treatment Outcome; D019444:Vaccines, DNA / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D004337:Drug Carriers; D008081:Liposomes; D019444:Vaccines, DNA
keywords: Atlantic salmon; DNA vaccine; DOTAP; Feed; IPNV; Liposome; Oral delivery; Salmon salar