Experimental sensitization to subtilisin. II. Production of specific antibodies following inhalation exposure of guinea pigs.

We have previously reported the development of pulmonary sensitivity in guinea pigs exposed for 5 consecutive days to bacterial subtilisin in concentrations ranging from 1.9 to 15.0 mg proteolytic enzyme/m3. Animals exposed to lesser concentrations of 0.0083 and 0.041 mg/m3 failed to demonstrate this sensitivity. In the same study, animals exposed for 11 weeks to a subtilisin concentration of 0.00068 mg/m3 followed by 6 weeks to 0.0051 mg/m3 failed to demonstrate pulmonary sensitivity. We report here the antibody response in these animals. Both an enzyme-linked immunosorbent assay and a latex agglutination assay were developed for antibody detection. A concentration-related antibody response was detected in animals which had received acute subtilisin exposures of 0.0083 to 1.9 mg/m3. Antibody titers were not increased further upon exposure to higher subtilisin concentrations. A single 3-hr exposure to 1.9 mg/m3 resulted in the same antibody response as that produced following 5 days of exposure to the same concentration. The cumulative 17-week exposure of 1.12 mg/m3 X hr subtilisin resulted in 36% (9 of 25) of the animals producing significant levels of IgG or IgM antibodies. None of these animals demonstrated pulmonary sensitivity. These results indicate that the circulating antibody titer reflected antigen exposure levels and occurred at exposures below those necessary for production of pulmonary sensitivity.