Titration of Cholera Antitoxin Levels by Passive Hemagglutination Tests Using Fresh and Formalinized Sheep Erythrocytes

Abstract

Hemagglutination titers of cholera antitoxin (rabbit sera) determined with sheep erythrocytes sensitized with crude or purified cholera toxin correlated with the antitoxin levels as determined by the rabbit skin permeability factor neutralization test. Tannic acid treatment of erythrocytes was unnecessary. Both fresh and formalinized erythrocytes were satisfactory, and the latter, sensitized with toxin, could be stored without loss of sensitivity for at least 60 days. The presence of “somatic” antigen in crude toxin did not interfere with the specificity of the test.