Detection of long-term cellular immunity to Coxiella burneti as assayed by lymphocyte transformation.

Delayed hypersensitivity to the antigens of Coxiella burneti, Nine Mile strain, was demonstrated in human subjects with various past histories of exposure to the organism by using lymphocyte transformation assays. Individuals with histories indicating exposure to C. burneti up to 8 years before the study demonstrated marked lymphocyte transformation in vitro to whole-cell antigens consisting of formalin-killed C. burneti phase I and phase II. These individuals also demonstrated a marked lymphocyte response to the trichloracetic acid-soluable phase I antigen. One individual who acquired Q fever during the study and one individual who received an experimental Q fever vaccine 4 years earlier were also evaluated by the lymphocyte transformation assay. It was also found that phase I trichloroacetic acid-soluble material was capable of acting as an antigen in the assay, whereas the phase II trichloroacetic acid-soluble material did not contain any antigenic material capable of causing lymphocyte transformation. The complete phase I trichloroacetic acid-soluble antigen, which was found to consist of protein and carbohydrate, was chemically fractionated into monospecific fractions. The fraction treated to eliminate carbohydrate was the only fraction found to elicit an in vitro response.