The incidence of bloodstream infections caused by Candida species has increased dramatically, so that these organisms now account for 10% of all bloodstream isolates. During the process of hematogenous dissemination, it is likely that blood-borne organisms must adhere to and penetrate the endothelial lining of the vasculature to invade the tissue parenchyma. Thus, a potential method to prevent or treat hematogenously disseminated candidal infections is to augment the combined response of neutrophils and endothelial cells against this organism while it is within the intravascular compartment. We have shown that adding neutrophils to Candida-infected endothelium prevents endothelial cell injury in vitro. Also, we have found that Candida albicans by itself can stimulate endothelial cells to express leukocyte adhesion molecules and proinflammatory cytokines. The expression of these factors is greatly increased when neutrophils are added to endothelium infected with C. albicans. Together, these results suggest that there is a two-way exchange of signals between endothelial cells and neutrophils during their response to intravascular infection. The experiments outlined in this proposal are designed to elucidate the mechanisms that mediate this neutrophil amplification of the endothelial cell proinflammatory response to C. albicans. The influence of the microbial target (C. albicans) on the neutrophil enhancement of the endothelial cell response will be evaluated first. Based on these results, the immunomodulatory substances that mediate this neutrophil amplification will be identified. The expression of the leukocyte adhesion molecules, E-selectin and VCAM-1, will be used as a marker of endothelial cell activation in these experiments. Next, the activities of the immunomodulatory substances identified by the above experiments will be inhibited to determine if theses substances also influence the ability of neutrophils to kill C. albicans and protect endothelial cells from candidal injury. Finally, the results of these in vitro experiments will be evaluated in vivo. Both immunocompetent and neutropenic mice will be infected with C. albicans and immunohistochemistry will be used to detect the local expression of leukocyte adhesion molecules and cytokines at sites of candidal infection. Investigating the interactions between endothelial cells, neutrophils and C. albicans will enable us to determine the mechanism by which endothelial cells are activated in response to infection. The long-range goal of these studies is to devise endothelial cell-based strategies to enhance the host inflammatory response to blood-borne microbial pathogens.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
1R29AI040636-01
Application #
2005200
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Project Start
1997-04-01
Project End
2002-03-31
Budget Start
1997-04-01
Budget End
1998-03-31
Support Year
1
Fiscal Year
1997
Total Cost
Indirect Cost
City
Torrance
State
CA
Country
United States
Zip Code
90502
Sanchez, Angela A; Johnston, Douglas A; Myers, Carter et al. (2004) Relationship between Candida albicans virulence during experimental hematogenously disseminated infection and endothelial cell damage in vitro. Infect Immun 72:598-601
Spellberg, Brad; Johnston, Douglas; Phan, Quynh Trang et al. (2003) Parenchymal organ, and not splenic, immunity correlates with host survival during disseminated candidiasis. Infect Immun 71:5756-64
Belanger, Paul H; Johnston, Douglas A; Fratti, Rutilio A et al. (2002) Endocytosis of Candida albicans by vascular endothelial cells is associated with tyrosine phosphorylation of specific host cell proteins. Cell Microbiol 4:805-12
Fu, Yue; Ibrahim, Ashraf S; Sheppard, Donald C et al. (2002) Candida albicans Als1p: an adhesin that is a downstream effector of the EFG1 filamentation pathway. Mol Microbiol 44:61-72
Tsuchimori, N; Sharkey, L L; Fonzi, W A et al. (2000) Reduced virulence of HWP1-deficient mutants of Candida albicans and their interactions with host cells. Infect Immun 68:1997-2002
Clemons, K V; Calich, V L; Burger, E et al. (2000) Pathogenesis I: interactions of host cells and fungi. Med Mycol 38 Suppl 1:99-111
Phan, Q T; Belanger, P H; Filler, S G (2000) Role of hyphal formation in interactions of Candida albicans with endothelial cells. Infect Immun 68:3485-90
Rieg, G; Fu, Y; Ibrahim, A S et al. (1999) Unanticipated heterogeneity in growth rate and virulence among Candida albicans AAF1 null mutants. Infect Immun 67:3193-8
Kupferwasser, L I; Yeaman, M R; Shapiro, S M et al. (1999) Acetylsalicylic acid reduces vegetation bacterial density, hematogenous bacterial dissemination, and frequency of embolic events in experimental Staphylococcus aureus endocarditis through antiplatelet and antibacterial effects. Circulation 99:2791-7
Fu, Y; Filler, S G; Spellberg, B J et al. (1998) Cloning and characterization of CAD1/AAF1, a gene from Candida albicans that induces adherence to endothelial cells after expression in Saccharomyces cerevisiae. Infect Immun 66:2078-84

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