Immunologic responses of calves to aerosolized antigen: humoral response to ovalbumin.

The humoral response of cattle to ovalbumin (OA), a nonenvironmental well-defined antigen, was studied. During 9 weeks of aerosolization, weekly serum and nasal secretion concentrations of immunoglobulin (Ig)G1, IgG2, IgM, IgA, and IgE were determined by enzyme-linked immunosorbent assay (ELISA) for OA specific antibody. Data from 3 calves given aerosol OA were compared and contrasted with data from 3 calves given aerosol saline solution and 1 calf given parenteral OA. The presence of cytotropic (skin sensitizing) antibody was evaluated during weeks 6 and 9 by direct skin testing with OA. A humoral response was induced in all 3 calves given aerosol OA. Serum IgG1 and IgG2 titers reached a maximum of 64,000 and 2,000, respectively, in calves given aerosol OA compared with 521,000 and 16,000, respectively, in the calf given parenteral OA. The ELISA did not detect an OA-specific IgM response. In contrast, all 3 calves given aerosol OA had serum IgA concentrations that increased to a peak by week 9. The mean IgA absorbance value for the 3 calves given aerosol OA was slightly greater than 5 times that of the calf given parenteral OA. Similarly, nasal secretions from calves given aerosolized OA had absorbance values that were 15-fold greater than that from the calf given parenteral OA. Calves given aerosol OA had antigen-specific IgE responses during weeks 6 to 8. The ELISA results were compared with results of passive cutaneous anaphylaxis tests. The presence of skin-sensitizing antibody was indicated by positive skin tests in the calves given aerosol OA and the calf given parenteral OA by week 9.