Comparison of adjuvant and adjuvant‐free murine experimental asthma models

Abstract

IntroductionThe most widely used protocol for the induction of experimental allergic airway inflammation in mice involves sensitization by intraperitoneal (i.p.) injections of the antigen ovalbumin (OVA) used in conjunction with the adjuvant aluminium hydroxide (alum). Although adjuvants are frequently used, there are questions regarding the necessity of alum for murine asthma studies due to the non-physiological nature of this chemical.ObjectiveThe objective of this study was to compare experimental asthma phenotypes between adjuvant and adjuvant-free protocols of murine allergic airway inflammation in an attempt to develop a standardized alternative to adjuvant use.MethodAn adjuvant-free OVA model of experimental asthma was investigated in BALB/c mice using i.p. or subcutaneous (s.c.) sensitization routes. For the s.c. sensitization, β-galactosidase (β-gal) was also tested as an antigen. In addition, OVA adjuvant and adjuvant-free sensitization protocols were compared in BALB/c and C57BL/6 mice. Open-field testing was performed to assess the effect of alum on mouse behaviour.ResultsComparison of adjuvant vs. adjuvant-free and i.p. vs. s.c. protocols revealed that both adjuvant use and route of antigen application significantly influenced OVA-specific antibody production. Comparison of adjuvant and adjuvant-free protocols in this study clearly demonstrated the non-requirement of alum for the induction of acute allergic airway inflammation, as both protocols induce a similar disease phenotype. BALB/c mice were significantly more susceptible than C57BL/6 mice to sensitization. Using the improved s.c. adjuvant-free protocol, it was demonstrated that alternative antigens such as β-gal can also be utilized. Behavioural studies indicated severe distress in mice treated with alum.ConclusionThe OVA s.c. adjuvant-free protocol used in this study generates a phenotype comparable to the benchmark adjuvant protocol widely used in the literature. The adjuvant-free alternative avoids the added complication of non-physiological adjuvants that may interfere with asthma treatment or prevention strategies.

Clara cells drive eosinophil accumulation in allergic asthma

“…Examination of the differential cell types showed a specific reduction in the number of eosinophils ( fig. 2b), which are the predominant inflammatory cell infiltrate in this model [23]. In contrast, the moderate increase seen in the numbers of lymphocytes and neutrophils in the BALF following allergen challenges was not affected by NA treatment ( fig.…”

“…Assessment of leukocyte distribution in bronchoalveolar lavage fluid 48 h after the last challenge, mice were sacrificed and bronchoalveolar lavage fluid (BALF) was generated as described previously [23]. The total number of leukocytes was determined using a Casy TT Cell Counter (Schärfe System GmbH, Reutlingen, Germany).…”

“…Lung tissues were embedded into paraffin and 3-mm sections were stained with haematoxylin and eosin (H&E) or Periodic acid-Schiff (PAS) for light microscopy, as described elsewhere [23]. Immuno-histochemical staining was performed on paraffin-embedded lung tissue.…”

Proposta de um modelo murino de curta duração de resposta pulmonar alérgica aguda sem utilização de adjuvante

“…(15,16) In addition, alum has been shown to cause major stress in animals up to 4 h after exposure. (6) Studies in which alum was not used demonstrated that this substance is not necessary for the induction of an allergic response in the lungs of mice and that there is no difference between subcutaneous sensitization without the use of adjuvants and intraperitoneal sensitization with alum. Those studies, involving protocols without the use of adjuvants, demonstrated different levels of in BAL fluid or in terms of EPO levels in lung tissue.…”

“…(6,7) The results of that study allow the exclusion of the use of adjuvants in murine models of asthma in future studies; the artificial way in which asthma is currently studied in animal models, with the use of adjuvants, has been justifiably criticized. However, in that study, there were three sensitizations, 7 disposed of in accordance with the norms of the institution.…”