Production of extracellular proteolytic activity by Histoplasma capsulatum grown in Histoplasma-macrophage medium is limited to restriction fragment length polymorphism class 1 isolates

Abstract

Extracellular proteolytic activity was studied for 28 strains of Histoplasma capsulatum var. capsulatum and 2 strains of H. capsulatum var. duboisii. Secreted protease activity assessed by skim milk agarose clearance was limited solely to H. capsulatum var. capsulatum restriction fragment length polymorphism (RFLP) class 1 strains. There was a difference in proteolytic activity levels among class 1 strains. Extracellular proteolytic activity was further determined during growth of those strains in liquid medium using azodye-impregnated protein substrates. In general, the highest activities were measured when azocollagen was used, whereas azocasein and azoalbumin were cleaved less efficiently. The activity was inhibited by phenylmethylsulfonyl fluoride, 4-(2-aminoethyl) benzenesulfonyl fluoride, antipain, and chymostatin, indicating, thereby, the presence of chymotrypsin-like serine proteases. Chromatographic analyses as well as variable substrate use at different culture times revealed production of at least 2 different enzyme pools of the same serine-like protease family. Our results demonstrate a distinctive ability of RFLP class 1 isolates to produce and secrete serine proteinase-type activity. This peculiarity may be relevant to the biology and pathogenesis of this particular clade of H. capsulatum isolates. Overall, the feature of extracellular proteolytic activity production enables a convenient and unequivocal identification of RFLP class 1 isolates and, thereby, can be used in H. capsulatum strain differentiation and typing.

Investigation of the Efficacy of Micafungin in the Treatment of Histoplasmosis Using Two North American Strains of Histoplasma capsulatum

“…Genotyping using YPS3 (1,9) showed that the 94-255 isolate did not express YPS3 and, thus, was a class 1 strain, whereas the IU-CT isolate expressed YPS3, which is characteristic for class 2 (Fig. 1A), the predominant type in North America (20).…”

Secreted Dipeptidyl Peptidase IV Activity in the Dimorphic Fungal PathogenHistoplasma capsulatum

“…Some of the fungal virulence factors identified to date include proteases, such as the secreted aspartyl proteases from Candida albicans (20,22). Extracellular proteolytic activity has been described previously in H. capsulatum and shown to hydrolyze casein, bovine serum albumin, and collagen (21,23,24,30). However, H. capsulatum protease genes have not been identified.…”

Histoplasma mechanisms of pathogenesis - one portfolio doesn't fit all

“…Chemotype II comprise those strains for which the yeast cell wall contains α-glucan whereas Chemotype I strains lack α-glucan in the yeast cell wall. Follow-up studies using immunogold labeling confirmed the presence of α-glucan in the yeast cell walls of Chemotype II strains G186A (Panamanian class) and UCLA531 (a North American isolate with the same RFLP pattern and fatty acid profile as the Downs NAm1 strain) (Eissenberg , et al , 1997, Zarnowski , et al , 2007). In contrast, the NAm2 strain G217B lacks α-glucan defining it as Chemotype I (Eissenberg , et al , 1991).…”

“…In a survey of cellular lipids, distinct fatty acid compositions of yeast cells were found to exist among the Histoplasma strains (Zarnowski , et al , 2007). The Histoplasma H-antigen (Hag1; β-glucosidase) is produced by all strains, but G217B yeast release over ten times as much β-glucosidase activity (Fisher , et al , 1999).…”