Larson, Kirsten A.

Abstract The mouse eosinophil peroxidase (mEPO) gene was cloned by screening a random-primed bone marrow cDNA library at reduced criteria using a hEPO cDNA. An mEPO cDNA was subsequently used to isolate the mEPO gene from a λ-genomic library. The mEPO gene displays a high degree of conservation with its human homologue: the transcription units are approximately the same size, conserve the relative size and position of the 12 exons associated with each gene, and at a nucleotide level the mouse and human EPO genes are 86% identical in the protein coding regions and 66% identical in the 3'-untranslated trailer regions. This strong conservation extends to the encoded proteins which show ~90% amino acid identity. Expression of the mEPO gene is restricted to tissues containing eosinophil progenitor cells (e.g., bone marrow and spleen), a pattern similar to the expression of another murine eosinophil granule protein, major basic protein.

Abstract We have identified a new eosinophil major basic protein gene family member in the mouse and have given it the designation murine major basic protein-2 (mMBP-2). The gene was initially characterized as a unique expressed sequence tag (EST) clone having significant identity to the previously recognized member of this gene family, mMBP-1. The EST was used to screen and isolate mMBP-2 from a bone marrow cDNA library. In addition, a genomic clone of mMBP-2 was isolated and this gene was shown to be physically linked to within 100 kb of mMBP-1 on the central region of mouse chromosome 2. Progressive similarity alignment of the deduced mMBP-2 open reading frame demonstrates the apparent conservation of the “pre-pro-mature” protein structure found in the other known mammalian MBPs. Mature mMBP-2 maintains the cationic nature associated with these proteins with a predicted pI of 9.95. However, unlike the human MBPs, which display a three orders of magnitude charge difference [hMBP-1 (pI11.4) vs. hMBP-2 (pI8.7)], mMBP-2 is only slightly less cationic than mMBP-1 (pI 10.5). Expression studies demonstrate that transcription of the mMBP-2 gene parallels mMBP-1 and is confined to hematopoietic compartments engaged in eosinophilopoiesis. Moreover, using mMBP-1 knockout mice and immunohistochemistry with an antisera that recognizes both mMBP-1 and -2, we demonstrate that mMBP-2 protein expression is restricted to eosinophil lineage-committed cells. J. Leukoc. Biol. 67: 567–576; 2000.

Abstract The relationship between eosinophils and the development of Ag-induced pulmonary pathologies, including airway hyper-responsiveness, was investigated using mice deficient for the secondary granule component, major basic protein-1 (mMBP-1). The loss of mMBP-1 had no effect on OVA-induced airway histopathologies or inflammatory cell recruitment. Lung function measurements of knockout mice demonstrated a generalized hyporeactivity to methacholine-induced airflow changes (relative to wild type); however, this baseline phenotype was observable only with methacholine; no relative airflow changes were observed in response to another nonspecific stimulus (serotonin). Moreover, OVA sensitization/aerosol challenge of wild-type and mMBP-1−/− mice resulted in identical dose-response changes to either methacholine or serotonin. Thus, the airway hyper-responsiveness in murine models of asthma occurs in the absence of mMBP-1.

Abstract The temporal association between airway inflammation and airway hyperresponsiveness (AHR) has been analyzed in BALB/c mice sensitized to, and subsequently exposed to, a single intranasal challenge of ovalbumin (OVA). In OVA-sensitized/challenged animals only a small increase in responsiveness to methacholine (MCh) was seen at 8 h, peaked at 24 to 48 h, and resolved by 96 h. An early bronchoalveolar lavage fluid (BALF) neutrophil infiltrate (peaking at 8 h postchallenge; ∼ 72% total cells was observed) that returned to baseline by 48 h. BALF eosinophil numbers did not increase until 48 h (∼ 32% of total cells), peaked at 96 h (∼ 38% total cells), and remained elevated at 8 d (∼ 27% total cells). Airway tissue eosinophilia preceded changes in BALF. Eosinophil peroxidase (EPO) levels in BALF were elevated in OVA-sensitized/challenged mice at 48 h only. BALF TNF- α levels peaked at 8 h, whereas IL-5 and IL-4 levels peaked at 24 h. IL-13 levels were increased at both 24 and 48 h. Mucus-positive cells were not observed in the airway epithelium until 48 h. Administration of IL-5 or VLA-4 antibody prior to OVA challenge prevented the development of AHR in sensitized mice as well as BALF and tissue eosinophilia. These data identify a temporal association between Th2 cytokine production, tissue eosinophil infiltration and activation, and, importantly, both the development and resolution kinetics of AHR. Moreover, the antibody studies further support the association of eosinophilia with the pathogenesis of AHR.

We have generated transgenic mice that constitutively express murine interleukin (IL)-5 in the lung epithelium. Airway expression of this cytokine resulted in a dramatic accumulation of peribronchial eosinophils and striking pathologic changes including the expansion of bronchusassociated lymphoid tissue (BALT), goblet cell hyperplasia, epithelial hypertrophy, and focal collagen deposition. These changes were also accompanied by eosinophil infiltration of the airway lumen. In addition, transgenic animals displayed airway hyperresponsiveness to methacholine in the absence of aerosolized antigen challenge. These findings demonstrate that lung-specific IL-5 expression can induce pathologic changes characteristic of asthma and may provide useful models to evaluate the efficacy of potential respiratory disease therapies or pharmaceuticals.