title: Oral antigen exposure in newborn piglets circumvents induction of oral tolerance in response to intraperitoneal vaccination in later life.
abstract: BACKGROUND
  We previously determined that newborn piglets orally gavaged with Ovalbumin (OVA) responded to systemic OVA re-exposure with tolerance; if adjuvants were included in oral vaccine, piglets responded with antibody-mediated immunity (Vet Immunol Immunopathol 161(3-4):211-21, 2014). Here, we will investigate whether newborn piglets gavaged with a vaccine comprised of OVA plus unmethylated CpG oligodeoxynucleotides (CpG; soluble component; OVA/CpG) combined with OVA plus CpG encapsulated within polyphosphazene microparticles (MP; particulate component) responded with systemic and mucosal immunity. To monitor the response to systemic antigen re-exposure, piglets were i.p.-immunized with OVA plus Incomplete Freund's Adjuvant (IFA) one month later.
  
  
  RESULTS
  Newborn piglets (n = 5/group) were gavaged with a combined soluble and particulate vaccine consisting of OVA (0.5-0.05 mg) plus 50 μg CpG and 0.5 mg OVA plus 50 μg CpG encapsulated within a polyphosphazene MP (0.5 mg) referred to as OVA/CpG + MP. Control piglets were gavaged with saline alone. Piglets were i.p. immunized with 10 mg OVA (or saline) in IFA at four weeks of age and then euthanized at eight weeks of age. We observed significantly higher titres of serum anti-OVA immunoglobulin (Ig) IgM, IgA, IgG, IgG1, IgG2 and IgG in piglets immunized with 0.05 mg OVA/CpG + MP relative to saline control animals. Thus, a single oral exposure at birth to a combined soluble and particulate OVA vaccine including adjuvants can circumvent induction of oral tolerance which impacts response to i.p. vaccination in later life. Further, piglets gavaged with 0.05 mg OVA/CpG + MP generated significant anti-OVA IgG and IgG1 titres in lung compared to saline control piglets but results were comparable to titres measured in parenteral control piglets. Peripheral blood mononuclear cells (PBMCs) ex vivo-stimulated with OVA showed markedly decreased production of IL-10 cytokine after 72 hours relative to animal-matched cells incubated with media alone. No production of IFN-γ was observed from any groups.
  
  
  CONCLUSIONS
  Newborn piglets gavaged with low dose soluble and particulate OVA plus CpG ODN and polyphosphazene adjuvants produced antigen-specific antibodies in serum and lung after systemic re-exposure in later life. These data indicate circumvention of oral tolerance but not induction of oral immunity.
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. alex.pasternak@usask.ca.
authors.forename: J Alex
authors.initials: JA
authors.lastname: Pasternak
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. sin630@mail.usask.ca.
authors.forename: Siew Hon
authors.initials: SH
authors.lastname: Ng
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. rachelle.buchanan@usask.ca.
authors.forename: Rachelle M
authors.initials: RM
authors.lastname: Buchanan
authors.affiliation: Current address: Klinikum der Universität zu Köln, Institut für Medizinische Mikrobiologie, Immunologie und Hygiene, Goldenfelsstraße 19-21, 50935, Köln, Germany. sonja.mertins@t-online.de.
authors.forename: Sonja
authors.initials: S
authors.lastname: Mertins
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. george.mutwiri@usask.ca.
authors.forename: George K
authors.initials: GK
authors.lastname: Mutwiri
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. volker.gerdts@usask.ca.
authors.forename: Volker
authors.initials: V
authors.lastname: Gerdts
authors.affiliation: Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK, S7N 5E3, Canada. heather.wilson@usask.ca.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Wilson
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000831:Animals, Newborn / Q000276:immunology*; D005620:Freund's Adjuvant / Q000008:administration & dosage; D007111:Immunity, Cellular / Q000276:immunology; D056724:Immunity, Humoral / Q000276:immunology; D007274:Injections, Intraperitoneal / Q000662:veterinary; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage / Q000276:immunology; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D013552:Swine / Q000276:immunology*; D014611:Vaccination / Q000379:methods / Q000662:veterinary*
chemical_list: C516146:CpG ODN-OVA; D009838:Oligodeoxyribonucleotides; D010047:Ovalbumin; D005620:Freund's Adjuvant