[Listeria antigens and their isolated protein fractions].

Antigens have been obtained from standard Listeria strains 1 and 4a by alcohol precipitation, sonication and multiple freezing and thawing. From these antigens protein fractions, immunologically identical as shown by the precipitation test and immunoelectrophoresis and similar in their chemical composition, have been isolated. The immunogenic properties of the fractions are determined by the polysaccharide-protein complex represented by amino acids (proline, histidine, lysine) and monosaccharides (ribose, glucose, arabinose), common for the fractions of three antigens. In experimental studies on mice and rabbits the protein fraction has been shown to produce a protective effect. After receiving this fraction in three injections and the subsequent challenge with the suspension of Listeria culture in a dose of 500 million cells, the animals have been found to develop no Listeria infection. After autoclaving the protein fraction looses its immunogenic properties, but retains the specificity of chemical groups and produces an allergenic effect as shown in experiments on guinea pigs and rabbits.