Inactivation of human gamma interferon by Pseudomonas aeruginosa proteases: elastase augments the effects of alkaline protease despite the presence of alpha 2-macroglobulin

Abstract

Pseudomonas aeruginosa alkaline protease (AP) has recently been shown to produce limited proteolysis of human gamma interferon (IFN--y) and thereby destroy the antiviral and macrophage-activating activities of the lymphokine. In the present study we describe some of the characteristics of Pseudomonas elastase (E) with regard to inactivation of human IFN-,y. The inhibitory effect of E on IFN--y bioactivity differed from that of AP in that the direct effects of E were reduced in the presence of human serum. That this property of human serum was in large part attributable to the protease inhibitor a2-macroglobulin (%2-M) was suggested by the following observations: (i) methylamine treatment of serum reduced its effect on E, (ii) E interacted directly with OL2-M to induce a characteristic conformational change in the protease inhibitor, and (iii) preformed E-a2-M complexes lacked IFN-y-degrading activity. Despite these findings, anti-E antiserum partially neutralized the effect that a Pseudomonas filtrate showed on IFN--y, suggesting that E contributes to the activity of bacterial filtrates. Treatment of IFN--y with E in the presence of a suboptimal concentration of AP resulted in an E dose-dependent inactivation of the lymphokine. Preformed E-_2-M complexes, although ineffective by themselves at cleaving IFN-y, degraded the lymphokine, providing AP was also present in the reaction mixture.

Proteolytic inactivation of cytokines by Pseudomonas aeruginosa

“…These results indicate that in vitro cytokine inactivation by Pseudomonas proteases is selective, requires only limited proteolysis, and in certain instances reflects the cooperative effects of both proteases.Pseudomonas aeruginosa is an important pulmonary pathogen in conditions like cystic fibrosis (15,42). It has been suggested that the ability of P. aeruginosa to establish itself in the respiratory tract may be promoted by its suppressive effects on pulmonary immune responses (2,16,40). The mechanisms of this immunosuppression are not entirely understood, but proteolytic enzymes secreted by the bacterium have been shown to degrade surface receptors on hematogenous cells (36, 43) and inactivate interleukin-2 (IL-2) and gamma interferon (IFN--y) (16,17,41).In the case of human IFN--y, cytokine inactivation was caused by either Pseudomonas alkaline protease (AP) (17) or elastase (E) (16).…”

“…It has been suggested that the ability of P. aeruginosa to establish itself in the respiratory tract may be promoted by its suppressive effects on pulmonary immune responses (2,16,40). The mechanisms of this immunosuppression are not entirely understood, but proteolytic enzymes secreted by the bacterium have been shown to degrade surface receptors on hematogenous cells (36, 43) and inactivate interleukin-2 (IL-2) and gamma interferon (IFN--y) (16,17,41).In the case of human IFN--y, cytokine inactivation was caused by either Pseudomonas alkaline protease (AP) (17) or elastase (E) (16). Significant reductions in antiviral and immunomodulatory activities were associated with limited proteolysis of IFN--y.…”

“…In the case of human IFN--y, cytokine inactivation was caused by either Pseudomonas alkaline protease (AP) (17) or elastase (E) (16). Significant reductions in antiviral and immunomodulatory activities were associated with limited proteolysis of IFN--y.…”

Randomized, Double‐Blind, Placebo‐Controlled, Dose‐Escalating Study of Aerosolized Interferon Gamma‐1b in Patients With Mild to Moderate Cystic Fibrosis Lung Disease

“…To our knowledge, there is no evidence that IFN-g1b is vulnerable to the proteolytic activity of human neutrophil elastase, but it is also possible that Pseduomonas proteases may have reduced IFN-g1b bioactivity, since this organism was present in 87% of patients in this study. 41 Similarly, the adverse events observed in patients receiving 1,000 mg IFN-g1b may have been due to other factors, as discussed above.…”

On the proteolytic activity of contact lenses and bacteria

“…Consequently, it may have been an other enzyme than a plasmin-like serine protease. Pseudomonas alkaline protease and metallo elastase (Catanase & Kress 1984;Kress 1986;Horvat et al 1989;Fick et al 1986) could come into question. Exact knowledge of the nature of the tissue destructive properties of each microbe is a prequisite for the prevention of tissue damage and for optimal treatment.…”