Experimental Observations on the Antigenic Potency of H. Pertussis Extracts

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Abstract
Summary: An attempt was made to compare the antigenic potency of extracts of H. pertussis with standard pertusis vaccine. The titer of complement fixing antibodies in rabbits after the injection of these agents was the index used. Observations on a small number of animals suggest the following possibilities. Fresh extracts of recently isolated strains produce a more rapid rise in titer than does vaccine. The addition of formalin, chinosol and tricresol to these extracts delays the response. Filtration of the extract through a Berkefeld L2 filter removes the antigen. A more rapid response occurs with the small quantity of extract prepared from the given amount of concentrated bacterial suspension than with the large quantity of standard vaccine prepared from the same amount of concentrated bacterial suspension. Therefore the greater concentration of the antigen in the extract is not the factor responsible for the rapid rise obtained. The unfixed and extracellular state of the antigen is the factor responsible. The antigenic component of H. pertussis endotoxin is relatively thermostabile whereas the toxic component is inactivated by temperatures of 37° and higher.

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