Role ofPLB1in Pulmonary Inflammation and Cryptococcal Eicosanoid Production

Abstract

Cryptococcal phospholipase (PLB1) is a secreted enzyme with lysophospholipase hydrolase and lysophospholipase transacylase activities. To investigate the role of PLB1 in the evasion of host immune responses, we characterized pulmonary immune responses to the parental (H99), the plb1 mutant, and the plb1 rec reconstituted mutant strains of Cryptococcus neoformans in mice. PLB1 was required for virulence during infection acquired via the respiratory tract. Mice infected with either H99 or the plb1 rec strain generated a nonprotective inflammatory response with subsequent eosinophilia, while mice infected with the plb1 mutant generated a protective immune response that controlled the infection. Because PLB1 is believed to facilitate virulence through host cell lysis, we examined the interaction of these strains with macrophages. The plb1 rec mutant exhibited decreased survival during coculture with macrophages. One factor which may be involved in the survival of yeast in the presence of macrophages is fungal eicosanoid production. Host eicosanoids have been shown to down-modulate macrophage functions. plb1 exhibited a defect in eicosanoid production derived from exogenous arachidonoyl-phosphatidylcholine, suggesting that PLB1 is required for the release of arachidonic acid from phospholipids. These data suggest that cryptococcal PLB1 may act as a virulence factor by enhancing the ability to survive macrophage antifungal defenses, possibly by facilitating fungal eicosanoid production.

Real-time imaging of trapping and urease-dependent transmigration of Cryptococcus neoformans in mouse brain

“…30, 31), enzymes involved in glucuronoxylomannan synthesis (involved in production of polysaccharide capsule; ref. 12), phospholipase B1 (involved in production of eicosanoid metabolites) (32), and urease (15,27). Undoubtedly, multiple, some as-yet-undiscovered genes, are involved in penetration of the endothelium.…”

Robust Th1 and Th17 Immunity Supports Pulmonary Clearance but Cannot Prevent Systemic Dissemination of Highly Virulent Cryptococcus neoformans H99

“…This was associated with the expression of virulence factors by H99 including urease and PLB1. 8,32 These previous studies have suggested that promoting a shift to a non-protective Th2 immune response could be a mechanism of H99-induced virulence.…”

“…This strain grows in the lungs in an uncontrolled fashion, readily disseminates into CNS, and causes 100% mortality in a variety of immunocompetent mouse strains such as C57BL/6, BALB/c, CB6129F2, and CBA/J mice. 8,13,[31][32][33] The infections with H99 were previously shown to result in upregulation of several hallmarks of Th2 immunity in the lungs. This was associated with the expression of virulence factors by H99 including urease and PLB1.…”

A novel approach for locating mice brain regions of Cryptococcus neoformans CNS invasion

“…The needle was bent and inserted into the trachea, and 30 µL PBS (containing 10 5 CFU Cryptococcus) was delivered. The skin was sutured with a cyanoacrylate adhesive, and the mice recovered with no visible trauma (Noverr et al, 2003).…”