DEGRADATION OF HUMORAL HOST-DEFENSE BY CANDIDA-ALBICANS PROTEINASE

The effect of an extracellular proteinase from the pathogenic yeast Ca ndida albicans on the bactericidal and opsonizing activities of human serum was studied. The ability of human polymorphonuclear leukocytes t o kill Staphylococcus aureus was greatly reduced when the bacteria wer e opsonized with human serum treated with the proteinase. The reductio n in the opsonizing activity of human serum was attributed to degradat ion of the Pc portion of immunoglobulin G by the action of C. albicans proteinase as determined by immunoprecipitation reaction. However, th e Fab portion of immunoglobulin G was resistant to proteolysis by the proteinase. A clear reduction in the bactericidal activity of human se rum against Escherichia coli was observed when the serum was treated w ith C. albicans proteinase. The reduction of serum bactericidal activi ty was attributed to the degradation of complement C3 by proteolysis b y the proteinase as determined by sodium dodecyl sulfate-polyacrylamid e gel electrophoresis, while C5 resisted the action of the proteinase. As determined by sodium dodecyl sulfate-polyacrylamide gel electropho resis, the proteinase also degrades endogenous proteinase inhibitors, such as alpha(2) macroglobulin and alpha(1) proteinase inhibitor, whic h are involved in regulating inflammation. These results suggest that destruction of a host's defense-oriented or regulatory proteins facili tates debilitation of the infected host.