The Specificity of Antibody Response in Typhus Fever. Its Alteration during Murine Typhus Infection as a Result of Previous Exposure to Epidemic Typhus Antigen

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Abstract
Summary: A previously described fluorescent antibody procedure that makes use of antibody absorption was used for the study of the sera of human volunteers in the strain E typhus vaccination experiments. These individuals had been vaccinated with either living strain E epidemic typhus rickettsiae or commercial killed epidemic typhus vaccine. They and several unvaccinated controls were subsequently challenged with living virulent rickettsiae of either epidemic typhus or murine typhus. In response to infection the unvaccinated controls formed specific (noncross-reacting) antibody that was directed toward the infecting rickettsiae. Similar results were seen in those (epidemic) vaccinated individuals who were infected with epidemic rickettsiae. Contrasting results were seen in the eight persons who received (epidemic) vaccine and were then infected with murine typhus rickettsiae. Five of these formed during their infection specific antibodies directed toward epidemic rickettsiae, two had mixed responses, and only one formed specific antibody for the infecting (murine) rickettsiae. These results indicate that the specificity of the antibody response is usually not a reliable indicator of the infecting type of typhus rickettsiae in persons who have had earlier immunologic experience with typhus antigen. In the United States this would include vaccinated members of the armed forces, and former inhabitants of eastern Europe. The latter group contains the individuals in whom recrudescent epidemic typhus, or Brill's disease, might be suspected.