Characterization of Human Serum and Nasal Hemagglutinating Antibody to Francisella Tularensis

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Abstract
Summary: The presence of specific antibody associated with the γA-immunoglobulins in nasal secretions was studied during the course of human respiratory tularemia in volunteers. Subjects immunized percutaneously with an attenuated tularemia vaccine 3 months previously, possessed detectable hemagglutinating antibody in both secretions and serum at the time of aerosol challenge with virulent organisms; nonimmunized subjects had none. Following aerosol challenge with 2500 virulent organisms, three of four previously immunized men withstood the challenge; all of the nonimmunized subjects and immunized individuals challenged with 25,000 organisms developed overt illness. Serum and nasal antibody persisted without significant change in titer in the immunized and became detectable in serum and nasal secretions of the nonimmunized subjects within 14 days after challenge. In both groups, serum antibody was associated primarily with the γM-immunoglobulins. Antibody in nasal secretions was found exclusively with the γA-immunoglobulins even though γG-immunoglobulins were detected in some secretions in both groups. Respiratory antibody activity to F. tularensis thus is found in the same immunoglobulin fraction which has been shown previously to possess antiviral activity.