Virulence of an aspergillopepsin-deficient mutant of Aspergillus fumigatus and evidence for another aspartic proteinase linked to the fungal cell wall

J Med Vet Mycol. May-Jun 1997;35(3):189-96. doi: 10.1080/02681219780001131.

Abstract

A gene replacement was performed to produce mutants of Aspergillus fumigatus deficient in the aspergillopepsin PEP (E.C. 3.4.23.18). The correct replacement of the PEP gene was confirmed by PCR and Southern hybridization experiments, whereas the absence of PEP production was demonstrated by Western blots. The culture supernatant of the transformants showed no detectable acid proteinase activity, suggesting that there is only one acid proteinase secreted by the fungus. The wild-type strain and the PEP-deficient mutants invaded tissues to a similar extent and produced comparable mortality in guinea pigs. As PEP represents a third secretory proteinase of A. fumigatus and the other two proteinases also did not show significant influence on fungal invasiveness, it is probable that secreted proteinases do not contribute decisively to tissue invasion in the pathogenesis of systemic aspergillosis. However, immunofluorescence on A. fumigatus colonies using polyclonal antibodies to PEP showed a similar pattern for the wild-type and for the mutants, with a bright fluorescence on young conidiophores, on submerged mycelium and on the tips of growing aerial mycelium. Conidia and mature aerial hyphae were not fluorescent. This pattern could reflect the existence of another crossreacting aspartic proteinase (PEP2) which was found to be sensitive to pepstatin but tightly linked to the fungal cell wall.

Publication types

  • Case Reports

MeSH terms

  • Animals
  • Aspartic Acid Endopeptidases / analysis
  • Aspartic Acid Endopeptidases / genetics*
  • Aspartic Acid Endopeptidases / metabolism
  • Aspergillosis / microbiology*
  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / isolation & purification
  • Aspergillus fumigatus / pathogenicity*
  • Cell Wall / enzymology
  • Fluorescent Antibody Technique
  • Genes, Fungal*
  • Guinea Pigs
  • Humans
  • Male
  • Mice
  • Mice, Inbred Strains
  • Middle Aged
  • Mutation*
  • Pepstatins / pharmacology
  • Plasmids
  • Polymerase Chain Reaction
  • Protease Inhibitors / pharmacology
  • Virulence / genetics

Substances

  • Pepstatins
  • Protease Inhibitors
  • Streptomyces pepsin inhibitor
  • Aspartic Acid Endopeptidases
  • aspergillopepsin I
  • pepstatin