Detection by Hemagglutination of Antibodies to Group A and Group E Streptococci by the Use of O -Stearoyl Derivatives of Their Cell Wall Carbohydrate-grouping Antigens

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Abstract
The streptococcal group A and group E cell wall polysaccharide antigens were extracted with tri-chloroacetic acid from the cell or cell wall and esterified with stearic acid. The stearoyl derivatives contained 5-8% (by weight) of the ester. Sheep or human red blood cells sensitized with the esterified antigens agglutinate in the presence of specific rabbit antisera. Sera from children hospitalized with group A streptococcal respiratory disease and swine possessing group E streptococcal lymphadenitis possess antibody titers significantly higher than the controls. The use of the 2 esterified antigens as controls for each other established the specificity of the reaction in each case. The general shape of the antigen-antibody pre-cipitin curves was not changed when the stearoyl antigens were used; however, the quantitative aspects differed markedly. Oligosaccharides which inhibit the normal antigen-antibody precipitin reaction did not inhibit the hemagglutination reaction. The adsorption of antisera with whole streptococcal cells reduced the hemagglutination titer in relation to the quantity of cells employed. Data are given on the optimal concentration of stearoyl antigen for sensitization, time of adsorption of antigen to red cells, use of albumin as diluting fluid and condition of red cells. Properties of the esterified antigens and the mechanism of the agglutination reaction are discussed. Polysaccharide antigens of other bacteria may be esterified and employed in a similar manner.