The passive cutaneous anaphylaxis (PCA) test in Cryptococcosis

Summary The PCA test appeared to be a useful indicator of past infection due toCryptococcus neoformans when the extracellular starch antigen was used. The whole cell antigen, crude cell wall antigen, ruptured cell antigen, crude carbohydrate antigen and the crude capsular polysaccharide antigen were not found to be effective.Serums from the nine rabbits injected withC. neoformans showed some degree of reactivity in the PCA test with the homologous extracellular starch antigen. Serums from rabbits injected withC. diffluens andC. laurentii gave no response.None of the rabbits exhibited evidence of previous sensitization and none were obviously infected. Six rabbits injected withC. neoformans were skin tested 4 weeks later with all of the antigens. Positive tests were obtained in four rabbits but only with the cell wall antigen or the ruptured cell antigen. PCA activity was not observed in the serums of mice injected with strains ofC. neoformans although some came from mice showing lesions and some came from fatally infected mice.Of the 500 human serums tested for PCA activity using the extracellular starch antigen, only one reacted strongly and with a sufficiently high titer to suggest previous infection. Serums from three cases of cryptococcosis failed to react.This investigation was supported by Communicable Disease Center grant CC 00151-01.The material in this paper is taken in part from a dissertation presented to the Graduate School of The University of Arizona in partial fullfilment of the requirements for the Ph.D. degree.