Abstract
Representatives of all genera within the Family Enterobacteriaceae share a common antigen (CA) which was described by Kunin, Beard and Halmagyi in 1962 (1) and which could be demonstrated by the indirect hemagglutination test. It is difficult to correlate these initial findings with some of the work which followed, for in their attempts to purify and characterize chemically this CA, the final product obtained failed to modify erythrocytes for hemagglutination. Subsequent work by Whang and Neter (2) showed that antigenic material in the heat-killed supernatant material derived from various enteric bacteria could be attached to erythrocytes which there-by became agglutinable in the presence of homologous as well as heterologous anti-CA sera. Furthermore, hemolysis could be demonstrated in the presence of complement, but neither bacterial agglutination nor precipitation could be shown in the presence of antibodies versus CA. Additional studies showed that the O antigen interfered with the antigenicity of CA and this led to ethanol fractionation to separate O from CA, which renders CA antigenic (3).
Studies on the biological significance of this complex antigen-antibody system via phagocytic experimentation revealed that CA antibodies opsonize enteric bacteria and also modified latex particles coated with this antigen (4, 5), suggesting that antibodies against CA might play a role in protection. Gorzyn-ski, Ambrus and Neter (6) showed that passive immunization resulted in slight transient protection of mice against experimental Salmonella infection. Domingue et al. (7) reported that immunization with the heat-killed supernatant CA followed by ethanol-soluble CA protected rabbits against experimental hematogenous and retrograde pyelonephritis. Although specificity of protective activity was shown in the pyelonephritic experiments, the vaccine (heat-killed supernatant) contained endotoxin. Because of the nonspecific protective action of endotoxin, it was therefore deemed necessary to evaluate the role of immunization with the ethanol-soluble fraction CA only, and unrelated to priming with the supernatant material derived from boiling bacterial cells for 1 hr.
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