Comparative gene expression profiling in two congenic mouse strains following Bordetella pertussis infection

Non-primate animal models for pertussis: back to the drawing board?

Despite considerable progress in the understanding of clinical pertussis, the contemporary emergence of antimicrobial resistance for Bordetella pertussis and an evolution of concerns with acellular component vaccination have both sparked a renewed interest. Although simian models of infection best correlate with the observed attributes of human infection, several animal models have been used for decades and have positively contributed in many ways to the related science. Nevertheless, there is yet the lack of a reliable small animal model system that mimics the combination of infection genesis, variable upper and lower respiratory infection, systemic effects, infection resolution, and vaccine responses. This narrative review examines the history and attributes of non-primate animal models for pertussis and places context with the current use and needs. Emerging from the latter is the necessity for further such study to better create the optimal model of infection and vaccination with use of current molecular tools and a broader range of animal systems. KEY POINTS: • Currently used and past non-primate animal models of B. pertussis infection often have unique and focused applications. • A non-primate animal model that consistently mimics human pertussis for the majority of key infection characteristics is lacking. • There remains ample opportunity for an improved non-primate animal model of pertussis with the use of current molecular biology tools and with further exploration of species not previously considered.

A comparison of two distinct murine macrophage gene expression profiles in response to Leishmania amazonensis infection

Background

The experimental murine model of leishmaniasis has been widely used to characterize the immune response against Leishmania. CBA mice develop severe lesions, while C57BL/6 present small chronic lesions under L. amazonensis infection. Employing a transcriptomic approach combined with biological network analysis, the gene expression profiles of C57BL/6 and CBA macrophages, before and after L. amazonensis infection in vitro, were compared. These strains were selected due to their different degrees of susceptibility to this parasite.

Results

The genes expressed by C57BL/6 and CBA macrophages, before and after infection, differ greatly, both with respect to absolute number as well as cell function. Uninfected C57BL/6 macrophages express genes involved in the deactivation pathway of macrophages at lower levels, while genes related to the activation of the host immune inflammatory response, including apoptosis and phagocytosis, have elevated expression levels. Several genes that participate in the apoptosis process were also observed to be up-regulated in C57BL/6 macrophages infected with L. amazonensis, which is very likely related to the capacity of these cells to control parasite infection. By contrast, genes involved in lipid metabolism were found to be up-regulated in CBA macrophages in response to infection, which supports the notion that L. amazonensis probably modulates parasitophorous vacuoles in order to survive and multiply in host cells.

Conclusion

The transcriptomic profiles of C57BL/6 macrophages, before and after infection, were shown to be involved in the macrophage pathway of activation, which may aid in the control of L. amazonensis infection, in contrast to the profiles of CBA cells.

Identification of the Mhc region as an asthma susceptibility locus in recombinant congenic mice

Mouse models of allergic asthma are characterized by airway hyperreactivity (AHR), Th2-driven eosinophilic airway inflammation, high allergen-specific IgE (anti-OVA IgE) levels in serum, and airway remodeling. Because asthma susceptibility has a strong genetic component, we aimed to identify new asthma susceptibility genes in the mouse by analyzing the asthma phenotypes of the Leishmania major resistant (lmr) recombinant congenic (RC) strains. The lmr RC strains are derived from C57BL/6 and BALB/c intercrosses and carry congenic loci on chromosome 17 (lmr1) and 9 (lmr2) in both backgrounds. Whereas the lmr2 locus on chromosome 9 contributes to a small background-specific effect on anti-OVA IgE and AHR, the lmr1 locus on chromosome 17 mediates a strong effect on Th2-driven eosinophilic airway inflammation and background-specific effects on anti-OVA IgE and AHR. The lmr1 locus contains almost 600 polymorphic genes. To narrow down this number of candidate genes, we performed genome-wide transcriptional profiling on lung tissue from C.lmr1 RC mice and BALB/c control mice. We identified a small number of differentially expressed genes located within the congenic fragment, including a number of Mhc genes, polymorphic between BALB/c and C57Bl/6. The analysis of asthma phenotypes in the C.B10-H2b RC strain, carrying the C57Bl/6 haplotype of the Mhc locus in a BALB/c genetic background, reveals a strikingly similar asthma phenotype compared with C.lmr1, indicating that the differentially expressed genes located within the C.B10-H2b congenic fragment are the most likely candidate genes to contribute to the reduced asthma phenotypes associated with the C57Bl/6 allele of lmr1.

Identification of a common gene expression response in different lung inflammatory diseases in rodents and macaques

To identify gene expression responses common to multiple pulmonary diseases we collected microarray data for acute lung inflammation models from 12 studies and used these in a meta-analysis. The data used include exposures to air pollutants; bacterial, viral, and parasitic infections; and allergic asthma models. Hierarchical clustering revealed a cluster of 383 up-regulated genes with a common response. This cluster contained five subsets, each characterized by more specific functions such as inflammatory response, interferon-induced genes, immune signaling, or cell proliferation. Of these subsets, the inflammatory response was common to all models, interferon-induced responses were more pronounced in bacterial and viral models, and a cell division response was more prominent in parasitic and allergic models. A common cluster containing 157 moderately down-regulated genes was associated with the effects of tissue damage. Responses to influenza in macaques were weaker than in mice, reflecting differences in the degree of lung inflammation and/or virus replication. The existence of a common cluster shows that in vivo lung inflammation in response to various pathogens or exposures proceeds through shared molecular mechanisms.