In order to investigate a role of
proteinase in the pathogenesis of
Candida infections, invasion of C. albicans strains of different
proteinase activity into the chorioallantoic membrane (CAM) of developing chicks was studied. Eight strains were used after examining the inducible
proteinase activity in the culture containing
bovine serum albumin as the sole source of
nitrogen. Six were
proteinase-producing strains (type I) and two were
proteinase-deficient ones (type II). Type I strains were subdivided into type Ia strains in which the
proteinase activity persisted for a week in the in vitro culture and type Ib ones in which the
enzyme activity was lost by the 7th day after inoculation. By inoculation onto CAM, the type I strains could invade the tissue in which secreted
proteinase was detected on the periphery of the invading Candida cells by immunohistochemical method. At an early stage of the
infection,
proteinase secretion was detected on the surface of the yeast cells before their entry into the tissue. The type II strains remained on the surface of the CAM and did not invade the tissue where the secretion of the
enzyme was not detected. The mortality rate of the chick embryo was not correlated with the degree of
proteinase production of these strains. Two type Ib strains invaded the CAM tissue and elicited some tissue reactions by the host, yielding a low mortality rate of the chick embryos. These results suggested that the secretion of
proteinase was an important factor for the invasion of CAM but other factors were also involved for the pathogenicity of C. albicans.