Viral infections were the dominant risk factor for wheezing among children hospitalized before 3 years of age. By comparison, a large majority of the wheezing children age 3 to 18 years had striking atopic characteristics that may be critical as a risk factor for hospitalization and an adverse response to viral infections, especially infections caused by rhinovirus.

Most, but not all, patients with EE are highly atopic individuals with frequent allergic sensitivities. Thus, serum IgE measurement of low-titer IgE antibody may be useful in identifying relevant food sensitivities and in distinguishing subgroups of patients with EE, making a more directed approach to food avoidance possible.

Fluid condensed from the breath of patients with acute asthma is acidic. Several features of asthma pathophysiology can be initiated by exposure of the airway to acid. In renal tubular epithelium, glutaminase produces ammonia to buffer urinary acid excretion. We hypothesized that human airway epithelium could also express glutaminase. Here, we demonstrate that human airway epithelial cells in vitro have biochemical evidence for glutaminase activity and express mRNA for two glutaminase isoforms (KGA and GAC). Glutaminase activity increased in response to acidic stress (media pH 5.8) and was associated with both increased culture medium pH and improved cell survival. In contrast, activity was inhibited by interferon-gamma and tumor necrosis factor-alpha. Glutaminase protein was expressed in the human airway in vivo. Further, ammonia levels in the breath condensate of subjects with acute asthma were low (30 microM [range: 0-233], n = 18, age 23 +/- 2.5 yr) compared with control subjects (327 microM [14-1,220], n = 24, age 24 +/- 2.4 yr, p < 0.001), and correlated with condensate pH (r = 0.58, p < 0.001). These data demonstrate that glutaminase is expressed and active in the human airway epithelium and may be relevant both to the regulation of airway pH and to the pathophysiology of acute asthmatic airway inflammation.