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Objective: To study the importance of ongoing allergen exposure and TH1/TH2 genetic background in augmented bacterial and inflammatory responses in allergic and infected mice., Design: BALB/c and C57BL/6 mice were made allergic to ovalbumin. After 1 day of intranasal allergen exposure, they were inoculated intranasally with Streptococcus pneumoniae. The numbers of bacteria and inflammatory cells in the sinuses were determined, and nasal responsiveness to histamine was assessed., Results: Infected BALB/c and C57BL/6 mice that received ongoing ovalbumin challenge following intraperitoneal sensitization showed significantly greater bacterial load and phagocyte level compared with the infected-only mice. Differences were diminished after the allergen challenge was stopped. Allergic and infected C57BL/6 mice showed fewer bacteria and phagocytes compared with the allergic and infected BALB/c mice. Surprisingly, in contrast to the nonallergenic C57BL/6 mice, the infected BALB/c mice showed a larger number of bacteria 28 days after infection., Conclusions: Ongoing allergic reaction augments bacterial load in both BALB/c and C57BL/6 mice and induces nasal hyperreactivity to histamine. Allergic and infected C57BL/6 mice show less allergic inflammation and bacterial load compared with allergic and infected BALB/c mice. Stopping allergen exposure reduces the response. Infected BALB/c mice, which favor a TH2 response, were less able to clear infection than C57BL/6 mice, which favor a TH1 response. Inflammation and bacterial load are affected by genetic background of mice and ongoing allergen stimulation.

Objectives: To develop a physiologic test of nasal responsiveness in mice and to evaluate whether mice with acute bacterial sinusitis develop nasal hyperresponsiveness., Design: Several experimental studies will be described. The first was a titration pilot study. The second was a randomized, placebo-controlled study. The remainder were before-and-after trials. SPECIES: BALB/c or C57BL/6 mice., Interventions: For these experiments, we exposed mice to histamine intranasally, then counted the number of sneezes and nose rubs as the primary outcome measure of nasal responsiveness. First, we constructed a dose-response curve. Second, we treated the mice with desloratadine, a histamine 1 receptor antagonist, prior to histamine exposure. Third, we challenged, with intranasal histamine, mice made allergic using 2 techniques. Fourth, we infected mice with Streptococcus pneumoniae to determine whether acute sinusitis causes nasal hyperresponsiveness to histamine exposure., Results: Nasal histamine challenge led to a reproducible, dose-dependent increase in sneezing and nose rubs. The response to histamine exposure was blocked by desloratadine (P < or = .05). Allergic mice had a significant increase in responsiveness (P < or = .05) over baseline after exposure to antigen. Mice with acute sinusitis had a sustained increase in responsiveness, although less severe than after allergy, compared with baseline values that lasted 12 days after infection (P < or = .05)., Conclusions: Nasal challenge with histamine is a physiologic test of nasal responsiveness. The hyperresponsiveness of allergic mice to histamine exposure parallels the response to nonspecific stimuli during the human allergic reaction. In addition, we showed that acute bacterial sinusitis causes nasal hyperresponsiveness in mice.