A Metalloproteinase of Coccidioides posadasii Contributes to Evasion of Host Detection

Abstract

Coccidioides posadasii is a fungal respiratory pathogen of humans that can cause disease in immunocompetent individuals. Coccidioidomycosis ranges from a mild to a severe infection. It is frequently characterized either as a persistent disease that requires months to resolve or as an essentially asymptomatic infection that can reactivate several years after the original insult. In this report we describe a mechanism by which the pathogen evades host detection during the pivotal reproductive (endosporulation) phase of the parasitic cycle. A metalloproteinase (Mep1) secreted during endospore differentiation digests an immunodominant cell surface antigen (SOWgp) and prevents host recognition of endospores during the phase of development when these fungal cells are most vulnerable to phagocytic cell defenses. C57BL/6 mice were immunized with recombinant SOWgp and then challenged with a mutant strain of C. posadasii in which the MEP1 gene was disrupted. The animals showed a significant increase in percent survival compared to SOWgp-immune mice challenged with the parental strain. To explain these results, we proposed that retention of SOWgp on the surfaces of endospores of the mutant strain in the presence of high titers of antibody to the immunodominant antigen contributes to opsonization, increased phagocytosis, and killing of the fungal cells. In vitro studies of the interaction between a murine alveolar macrophage cell line and parasitic cells coated with SOWgp showed that the addition of anti-SOWgp antibody could enhance phagocytosis and killing of Coccidioides. We suggest that Mep1 plays a pivotal role as a pathogenicity determinant during coccidioidal infections and contributes to the ability of the pathogen to persist within the mammalian host.

A Recombinant Aspartyl Protease ofCoccidioides posadasiiInduces Protection against Pulmonary Coccidioidomycosis in Mice

“…A 43-kDa, Coomassie blue-stained gel band was selected for further examination on the basis of its seroreactivity, prominence, and apparent electrophoretic separation from other protein components in the SDS-PAGE gel. The selected band was excised, destained, and subjected to in-gel digestion with sequencing-grade trypsin (Promega, Madison, Wis.) at 37°C overnight as reported previously (18). Peptides were extracted from the gel with 60% acetonitrile:0.1% trifluoroacetic acid and concentrated using an SPD1010 SpeedVac system (ThermoSavant, Holbrook, N.Y.).…”

“…Peptides were extracted from the gel with 60% acetonitrile:0.1% trifluoroacetic acid and concentrated using an SPD1010 SpeedVac system (ThermoSavant, Holbrook, N.Y.). The peptides were applied to a reverse-phase high-pressure liquid chromatography column (Aquasil C 18 Picofit column, 75-m inside diameter by 5 cm, tapered to 15-m inside diameter; New Objective, Woburn, Mass. ), eluted using a binary gradient of 1% acetic acidacetonitrile (5 to 95% acetonitrile in 35 min), and then introduced into an ion-trap mass spectrometer equipped with a nanospray source (LCQ Deca XP plus; Finnigan Corp., San Jose, Calif.).…”

Synthesis, experimental evaluation and molecular modelling of hydroxamate derivatives as zinc metalloproteinase inhibitors

“…Inhibitors of pseudolysin and thermolysin may weaken the pathogen and be a putative strategy in the fight against bacterial infections [5][6][7][8][9]. In order to have therapeutic potentials, bacterial M4 enzyme inhibitors should not interfere with the substrate degradation of endogenous zinc metalloproteinases of the infected host, like the matrix metalloproteinases (MMPs) and the adamalysins (ADAMs).…”

Update on Fungal Disease: From Establish Infection to Clinical Manifestation

“…However, Sharpton and collaborators (2009) compared the genomes of C. immitis and C. posadasii with the nearest nonpathogenic species Uncinocarpus reesii and with the most distant pathogenic fungus H. capsulatum. Specific genes were identified in the genus Coccidioides that were: related to the spherules; involved in energy metabolism; required for the use of allantoin as a nitrogen source; related to the membrane; and others that may be involved in host-parasite interactions [192,194,195]. Furthermore, it is believed that metalloproteinases such as (Mep1), which are secreted during endosporulation phase, are able to digest the immunodominant cell surface antigen (SOWgp), preventing host recognition of the endospores during the development phase [196].…”