Animal models to assess the effects of air pollutants on allergic lung disease

Animal models for protein respiratory sensitizers

Protein induced respiratory hypersensitivity, particularly atopic disease in general, and allergic asthma in particular, has increased dramatically over the last several decades in the US and other industrialized nations as a result of ill-defined changes in living conditions in modern western society. In addition, work-related asthma has become the most frequently diagnosed occupational respiratory illness. Animal models have demonstrated great utility in developing an understanding of the etiology and mechanisms of many diseases. A few models been developed as predictive models to identify a protein as an allergen or to characterize its potency. Here we describe animal models that have been used to investigate and identify protein respiratory sensitizers. In addition to prototypical experimental design, methods for exposure route, sample collection, and endpoint assessment are described. Some of the most relevant endpoints in assessing the potential for a given protein to induce atopic or allergic asthma respiratory hypersensitivity are the development of cytotropic antibodies (IgE, IgG1), eosinophil influx into the lung, and airway hyperresponsiveness to the sensitizing protein and/or to non-antigenic stimuli (Mch). The utility of technologies such as PCR and multiplexing assay systems is also described. These models and methods have been used to elucidate the potential for protein sources to induce allergy, identify environmental conditions (pollutants) to impact allergy responsiveness, and establish safe exposure limits. As an example, data are presented from an experiment designed to compare the allergenicity of a fungal biopesticide Metarhizium anisopliae (MACA) crude extract with the one of its components, conidia (CON) extract.

Genetic susceptibility to ozone-induced lung inflammation in animal models of asthma

PURPOSE OF REVIEW

Epidemiological associations between ozone exposure and allergic responsiveness are well-documented and have been corroborated in animal studies. The complex interaction between ozone and allergen has genetic and environmental components that affect atopic individuals and may increase the incidence of allergy in susceptible individuals. This review describes the advances that have been made in understanding mechanisms of genetic susceptibility to ozone-induced inflammation, and the interaction between ozone and allergen exposure in mice and a non-human primate model.

RECENT FINDINGS

Antioxidant and innate immune defense genes contribute to ozone-induced inflammation and hyperpermeability in mice and humans. Ozone exposure during the allergic challenge phase induces greater enhancement of allergic responsiveness than the sensitization stage. Ovalbumin-pulsed dendritic cells injected into naïve mice successfully sensitize the mouse to ovalbumin in the absence of adjuvant. Debate continues over the role of T helper 1-T helper 2 immune profile development in mediating the ozone-allergen interaction, and the potential confounding influence of the predominant T helper 2 system most commonly used to study these responses.

SUMMARY

The role of genetic background in susceptibility to ozone-induced lung inflammation has been confirmed, and promising candidate genes have been identified. Descriptive studies confirm that ozone exacerbates allergic responsiveness. Ozone administered during the challenge phase of ovalbumin allergen exposure induces greater responsiveness than during the sensitization phase. Allergen-induced responses enhanced by concurrent ozone exposure warrant further mechanistic research, particularly regarding the influence of susceptibility genes.