Objective—To assess IgE response and cytokine gene expressions in pulmonary lymph collected from bovine respiratory syncytial virus (BRSV)-infected calves after ovalbumin inhalation.
Animals—Thirteen 7- to 8-week-old calves.
Procedures—The efferent lymphatic duct of the caudal mediastinal lymph node of each calf was cannulated 3 or 4 days before experiment commencement. Calves were inoculated (day 0) with BRSV (n = 7) or BRSV-free tissue culture medium (mock exposure; 6) via aerosolization and exposed to aerosolized ovalbumin on days 1 through 6 and day 15. An efferent lymph sample was collected daily from each calf on days −1 through 16; CD4+ and CD8+ T lymphocyte subsets in lymph samples were enumerated with a fluorescence-activated cell scanner. Expressions of several cytokines by efferent lymphocytes and lymph ovalbumin-specific IgE concentration were measured. Each calf was euthanized on day 16 and then necropsied for evaluation of lungs.
Results—Mean fold increase in ovalbumin-specific IgE concentration was greater in BRSV-infected calves than in mock-infected calves. At various time points from days 4 through 10, percentages of T lymphocyte subsets and CD4+:CD8+ T lymphocyte ratios differed between BRSV-infected calves and day −1 values or from values in mock-infected calves. On days 3 through 5, IL-4 and IL-13 gene expressions in BRSV-infected calves were increased, compared with expressions in mock-infected calves. Lung lesions were consistent with antigen exposure.
Conclusions and Clinical Relevance—In response to the inhalation of aerosolized ovalbumin, BRSV infection in calves appeared to facilitate induction of a T helper 2 cell response and ovalbumin-specific IgE production.