Denaturation of Ovalbumin Abrogates Oral Induction of Airway Hyperreactivity and IgG1, IgG2 Antibody Responses in Guinea Pigs

Abstract

Background: The effects of denaturation of ovalbumin (OVA) on the induction of oral sensitization in guinea pigs were examined. Methods: Guinea pig antibody and airway responses were assessed after 10 feedings of chemically or heat–denatured OVA or egg white (EW). Results: Their specific IgG, IgG1 and IgG2 antibody responses were orally sensitized by OVA or EW, but not by chemically or heat–denatured OVA or EW. When further exposed to 0.1% OVA or conalbumin aerosol, those fed OVA or EW, but not denatured OVA or EW, had increased pulmonary resistance and decreased tidal volume. On the other hand, in those fed denatured OVA, boiled EW or saline only, a second sensitization with 1% OVA aerosol generated antibody responses and airway hyperreactivity. Using a sandwich ELISA, guinea pig serum OVA was detected after feeding EW, but not chemically denatured or boiled EW. Conclusions: It is likely that guinea pig gut absorption of OVA may result in oral sensitization. Chemical or heat denaturation of proteins may minimize their intestinal uptake and thus abrogates the induction of oral sensitization in guinea pigs.

Effect of Neonatal Sublingual Vaccination with Native or Denatured Ovalbumin and Adjuvant CpG or Cholera Toxin on Systemic and Mucosal Immunity in Mice

“…Ovalbumin (OVA; grade V) was obtained from Sigma (St. Louis, MO, USA). Chemical denaturation of OVA was performed as described previously [11]. In brief, it was first denatured by reduction of disulphide bonds after stirring overnight under vacuum suction with 8.0 M urea and 0.2 M 2-mercaptoethanol (Merck, Darmastadt, Germany).…”

“…Assessment of antibody responses by ELISA. Serum anti‐OVA antibody and total saliva antibody responses were assessed by enzyme‐linked immunosorbent assay (ELISA) as previously described [11]. Briefly, 96‐well plates (Nunc, Kamstrup, Roskilde, Denmark) were coated with 100 μ g/ml OVA, 10 μ g/ml goat anti‐mouse IgA (Sigma) or 4 μ g/ml affinity‐purified rat anti‐mouse IgE (Clone 23G3; SBA, Birmingham, AL, USA) in 0.05 m carbonate buffer, pH 9.6 (100 μ l/well), overnight at 4 °C.…”