Pathogenicity of Cryptococcus neoformans: an Evolutionary Perspective

Oscar Zaragoza; Susana Frasés; Arturo Casadevall

doi:10.1128/9781555815639.ch48

Chapter 48 : Pathogenicity of Cryptococcus neoformans: an Evolutionary Perspective

Authors: Oscar Zaragoza¹, Susana Frasés², Arturo Casadevall³

VIEW AFFILIATIONS HIDE AFFILIATIONS

Affiliations: 1: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461; 2: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461; 3: Department of Medicine and Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461

Content Type: Monograph

Publication Year: 2008

Category: Fungi and Fungal Pathogenesis; Bacterial Pathogenesis

Book DOI: 10.1128/9781555815639

Chapter DOI: 10.1128/9781555815639.ch48

MyBook is a cheap paperback edition of the original book and will be sold at uniform, low price.

Preview this chapter:

Pathogenicity of Cryptococcus neoformans: an Evolutionary Perspective, Page 1 of 2

< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815639/9781555814144_Chap48-1.gif /docserver/preview/fulltext/10.1128/9781555815639/9781555814144_Chap48-2.gif

Abstract:

Cryptococcus neoformans has several well-established virulence factors: a polysaccharide capsule that surrounds the cell body, melanin production, urease, phospholypase, and growth at 37°C. Among these factors, the best characterized are the capsule and melanin. The fact that the size of the capsule increases after infection suggests that it is required for survival in the host, and mutants unable to undergo this process are less virulent. The ability of C. neoformans to grow at 37°C and in slightly alkaline pH, which are conditions that the yeast encounters during infection in mammalian hosts, is a main feature that allows this yeast to be a pathogenic fungus. Furthermore, the interaction of C. neoformans with some of other hosts such as bacteria, protozoa and slime molds can enhance virulence by affecting what we consider to be the virulence factors of this yeast and the ability to kill mice. This chapter reviews the interactions and discusses how they may influence the virulence of the organism during evolution. Other virulence factors, such as phospholipase, are important for survival of the yeast cells. The chapter reviews how C. neoformans can infect and interact with many different hosts, including amoebas, nematodes, insects, and many mammals. At the same time, C. neoformans increased virulence by exploiting some of the features that this fungus uses for survival in the environment, such as the capsule and melanin production.

Citation: Zaragoza O, Frasés S, Casadevall A. 2008. Pathogenicity of Cryptococcus neoformans: an Evolutionary Perspective, p 602-590. In Baquero F, Nombela C, Cassell G, Gutiérrez-Fuentes J (ed), Evolutionary Biology of Bacterial and Fungal Pathogens. ASM Press, Washington, DC. doi: 10.1128/9781555815639.ch48

Highlighted Text: Show | Hide

Full text loading...

References

/content/book/10.1128/9781555815639.ch48

1. Alvarez, M., and, A. Casadevall. 2006. Phagosome extrusion and host-cell survival after Cryptococcus neoformans phagocytosis by macrophages. Curr. Biol. 16: 2161– 2165.

2. Apidianakis, Y.,, L. G. Rahme,, J. Heitman,, F. M. Ausubel,, S. B. Calderwood, and, E. Mylonakis. 2004. Challenge of Drosophila melanogaster with Cryptococcus neoformans and role of the innate immune response. Eukaryot. Cell 3: 413– 419.

3. Bacon, B. E.,, R. Cherniak,, K. J. Kwon-Chung, and, E. S. Jacobson. 1996. Structure of the O-deacetylated glucuronoxylomannan from Cryptococcus neoformans Cap70 as determined by 2D NMR spectroscopy. Carbohydr. Res. 283: 95– 110.

4. Bacon, B. E., and, R. Cherniak. 1995. Structure of the O-deacetylated glucuronoxylomannan from Cryptococcus neoformans serotype C as determined by 2D 1H NMR spectroscopy. Carbohydr. Res. 276: 365– 386.

5. Bava, A. J.,, J. Afeltra,, R. Negroni, and, R. A. Diez. 1995. Interferon gamma increases survival in murine experimental cryptococcosis. Rev. Inst. Med. Trop. Sao Paulo 37: 391– 396.

6. Bergman, F. 1965. Studies on capsule synthesis of Cryptococcus neoformans. Sabouraudia 4: 23– 31.

7. Bulmer, G. S., and, J. R. Tacker. 1975. Phagocytosis of Cryptococcus neoformans by alveolar macrophages. Infect. Immun. 11: 73– 79.

8. Bunting, L. A.,, J. B. Neilson, and, G. S. Bulmer. 1979. Cryptococcus neoformans: gastronomic delight of a soil ameba. Sabouraudia 17: 225– 232.

9. Casadevall, A.,, W. Cleare,, M. Feldmesser,, A. Glatman-Freedman,, D. L. Goldman,, T. R. Kozel, et al. 1998. Characterization of a murine monoclonal antibody to Cryptococcus neoformans polysaccharide that is a candidate for human therapeutic studies. Antimicrob. Agents Chemother. 42: 1437– 1446.

10. Casadevall, A., and, J. R. Perfect. 1998. Cryptococcus neoformans. ASM Press, Washington, DC.

11. Casadevall, A., and, L. Pirofski. 2005. Insights into mechanisms of antibody-mediated immunity from studies with Cryptococcus neoformans. Curr. Mol. Med. 5: 421– 433.

12. Casadevall, A., and, L. A. Pirofski. 2003. The damage-response framework of microbial pathogenesis. Nat. Rev. Microbiol. 1: 17– 24.

13. Casadevall, A.,, J. N. Steenbergen, and, J. D. Nosanchuk. 2003. ‘Ready made’ virulence and ‘dual use’ virulence factors in pathogenic environmental fungi—the Cryptococcus neoformans paradigm. Curr. Opin. Microbiol. 6: 332– 337.

14. Castellani, A. Phagocytic and destructive action of Hartmanella castellanii ( Amoeba castellanii) on pathogenic encapsulated yeast-like fungi Torulopsis neoformans ( Cryptococcus neoformans). Ann. Inst. Pasteur. 89: 1– 7.

15. Chang, Y. C., and, K. J. Kwon-Chung. 1994. Complementation of a capsule-deficient mutation of Cryptococcus neoformans restores its virulence. Mol. Cell Biol. 14: 4912– 4919.

16. Chang, Y. C., and, K. J. Kwon-Chung. 1998. Isolation of the third capsule-associated gene, CAP60, required for virulence in Cryptococcus neoformans. Infect. Immun. 66: 2230– 2236.

17. Chang, Y. C., and, K. J. Kwon-Chung. 1999. Isolation, characterization, and localization of a capsule-associated gene, CAP10, of Cryptococcus neoformans. J. Bacteriol. 181: 5636– 5643.

18. Chang, Y. C.,, L. A. Penoyer, and, K. J. Kwon-Chung. 1996. The second capsule gene of cryptococcus neoformans, CAP64, is essential for virulence. Infect. Immun. 64: 1977– 1983.

19. Chen, S. C.,, M. Muller,, J. Z. Zhou,, L. C. Wright, and, T. C. Sorrell. 1997. Phospholipase activity in Cryptococcus neoformans: a new virulence factor? J. Infect. Dis. 175: 414– 420.

20. Chikamori, M., and, K. Fukushima. 2005. A new hexose transporter from Cryptococcus neoformans: molecular cloning and structural and functional characterization. Fungal Genet. Biol. 42: 646– 655.

21. Chung, S.,, P. Mondon,, Y. C. Chang, and, K. J. Kwon-Chung. 2003. Cryptococcus neoformans with a mutation in the tetratricopeptide repeat-containing gene, CCN1, causes subcutaneous lesions but fails to cause systemic infection. Infect. Immun. 71: 1988– 1994.

22. Clemons, K. V.,, J. E. Lutz, and, D. A. Stevens. 2001. Efficacy of recombinant gamma interferon for treatment of systemic cryptococcosis in SCID mice. Antimicrob. Agents Chemother. 45: 686– 689.

23. Cox, G. M.,, H. C. McDade,, S. C. Chen,, S. C. Tucker,, M. Gottfredsson,, L. C. Wright, et al. 2001. Extracellular phospholipase activity is a virulence factor for Cryptococcus neoformans. Mol. Microbiol. 39: 166– 175.

24. Cox, G. M.,, J. Mukherjee,, G. T. Cole,, A. Casadevall, and, J. R. Perfect. 2000. Urease as a virulence factor in experimental cryptococcosis. Infect. Immun. 68: 443– 448.

25. Cruickshank, J. G.,, R. Cavill, and, M. Jelbert. 1973. Cryptococcus neoformans of unusual morphology. Appl. Microbiol. 25: 309– 312.

26. Currie, B.,, H. Sanati,, A. S. Ibrahim,, J. E. Edwards, Jr.,, A. Casadevall, and, M. A. Ghannoum. 1995. Sterol compositions and susceptibilities to amphotericin B of environmental Cryptococcus neoformans isolates are changed by murine passage. Antimicrob. Agents Chemother. 39: 1934– 1937.

27. Dadachova, E.,, R. A. Bryan,, X. Huang,, T. Moadel,, A. D. Schweitzer,, P. Aisen,, J. D. Nosanchuk, and, A. Casadevall. 2007. Ionizing radiation changes the electronic properties of melanin and enhances the growth of melanized fungi. PLoS ONE 2: e457.

28. Davidson, R. C.,, M. C. Cruz,, R. A. Sia,, B. Allen,, J. A. Alspaugh, and, J. Heitman. 2000. Gene disruption by biolistic transformation in serotype D strains of Cryptococcus neoformans. Fungal Genet. Biol. 29: 38– 48.

29. Diamond, R. D., and, J. E. Bennett. 1973. Growth of Cryptococcus neoformans within human macrophages in vitro. Infect. Immun. 7: 231– 236.

30. Dong, Z. M., and, J. W. Murphy. 1995. Effects of the two varieties of Cryptococcus neoformans cells and culture filtrate antigens on neutrophil locomotion. Infect. Immun. 63: 2632– 2644.

31. Eisenman, H. C.,, J. D. Nosanchuk,, J. B. Webber,, R. J. Emerson,, T. A. Camesano, and, A. Casadevall. 2005. Microstructure of cell wall-associated melanin in the human pathogenic fungus Cryptococcus neoformans. Biochemistry 44: 3683– 3693.

32. Ellis, D. H., and, T. J. Pfeiffer. 1990a. Ecology, life cycle, and infectious propagule of Cryptococcus neoformans. Lancet 336: 923– 925.

33. Ellis, D. H., and, T. J. Pfeiffer. 1990b. Natural habitat of Cryptococcus neoformans var. gattii. J. Clin. Microbiol. 28: 1642– 1644.

34. Feldmesser, M.,, Y. Kress, and, A. Casadevall. 2001. Dynamic changes in the morphology of Cryptococcus neoformans during murine pulmonary infection. Microbiology 147: 2355– 2365.

35. Feldmesser, M.,, Y. Kress,, P. Novikoff, and, A. Casadevall. 2000. Cryptococcus neoformans is a facultative intracellular pathogen in murine pulmonary infection. Infect. Immun. 68: 4225– 4237.

36. Frases, S.,, S. Chaskes,, E. Dadachova, and, A. Casadevall. 2006. Induction by Klebsiella aerogenes of a melanin-like pigment in Cryptococcus neoformans. Appl. Environ. Microbiol. 72: 1542– 1550.

37. Frases, S.,, A. Salazar,, E. Dadachova, and, A. Casadevall. 2007. Cryptococcus neoformans can utilize the bacterial melanin precursor homogentisic acid for fungal melanogenesis. Appl. Environ. Microbiol. 73: 615– 621.

38. Fries, B. C.,, F. Chen,, B. P. Currie, and, A. Casadevall. 1996. Karyotype instability in Cryptococcus neoformans infection. J. Clin. Microbiol. 34: 1531– 1534.

39. Fries, B. C.,, D. L. Goldman, and, A. Casadevall. 2002. Phenotypic switching in Cryptococcus neoformans. Microbes Infect. 4: 1345– 1352.

40. García-Rivera, J., and, A. Casadevall. 2001. Melanization of Cryptococcus neoformans reduces its susceptibility to the antimicrobial effects of silver nitrate. Med. Mycol. 39: 353– 357.

41. García-Rivera, J.,, Y. C. Chang,, K. J. Kwon-Chung, and, A. Casadevall. 2004. Cryptococcus neoformans CAP59 (or Cap59p) is involved in the extracellular trafficking of capsular glucuronoxylomannan. Eukaryot. Cell 3: 385– 392.

42. García-Rivera, J.,, H. C. Eisenman,, J. D. Nosanchuk,, P. Aisen,, O. Zaragoza,, T. Moadel, et al. 2005. Comparative analysis of Cryptococcus neoformans acid-resistant particles generated from pigmented cells grown in different laccase substrates. Fungal Genet. Biol. 42: 989– 998.

43. Gates, M. A.,, P. Thorkildson, and, T. R. Kozel. 2004. Molecular architecture of the Cryptococcus neoformans capsule. Mol. Microbiol. 52: 13.

44. Goldman, D.,, S. C. Lee, and, A. Casadevall. 1994. Pathogenesis of pulmonary Cryptococcus neoformans infection in the rat. Infect. Immun. 62: 4755– 4761.

45. Goldman, D. L.,, A. Casadevall,, Y. Cho, and, S. C. Lee. 1996. Cryptococcus neoformans meningitis in the rat. Lab. Invest. 75: 759– 770.

46. Goldman, D. L.,, S. C. Lee,, A. J. Mednick,, L. Montella, and, A. Casadevall. 2000. Persistent Cryptococcus neoformans pulmonary infection in the rat is associated with intracellular parasitism, decreased inducible nitric oxide synthase expression, and altered antibody responsiveness to cryptococcal polysaccharide. Infect. Immun. 68: 832– 838.

47. Granados, D. P., and, E. Castañeda. 2005. Influence of free-living amoeba on capsular size of Cryptococcus neoformans complex in environmental samples, p. 133. In S. M. Levitz (ed.), 6th International Conference of Cryptococcus and Cryptococcosis, 2005, Boston, Mass.

48. Granger, D. L.,, J. R. Perfect, and, D. T. Durack. 1985. Virulence of Cryptococcus neoformans. Regulation of capsule synthesis by carbon dioxide. J. Clin. Invest. 76: 508– 516.

49. Greub, G., and, D. Raoult. 2004. Microorganisms resistant to free-living amoebae. Clin. Microbiol. Rev. 17: 413– 433.

50. Heitman, J.,, B. Allen,, J. A. Alspaugh, and, K. J. Kwon-Chung. 1999. On the origins of congenic MATalpha and MATa strains of the pathogenic yeast Cryptococcus neoformans. Fungal Genet. Biol. 28: 1– 5.

51. Idnurm, A.,, J. L. Reedy,, J. C. Nussbaum, and, J. Heitman. 2004. Cryptococcus neoformans virulence gene discovery through insertional mutagenesis. Eukaryot. Cell 3: 420– 429.

52. Ikeda, R.,, T. Shinoda,, Y. Fukazawa, and, L. Kaufman. 1982. Antigenic characterization of Cryptococcus neoformans serotypes and its application to serotyping of clinical isolates. J. Clin. Microbiol. 16: 22– 29.

53. Ikeda, R.,, T. Sugita,, E. S. Jacobson, and, T. Shinoda. 2003. Effects of melanin upon susceptibility of Cryptococcus to antifungals. Microbiol. Immunol. 47: 271– 277.

54. Jacobson, E. S., and, H. S. Emery. 1991. Temperature regulation of the cryptococcal phenoloxidase. J. Med. Vet. Mycol. 29: 121– 124.

55. Jacobson, E. S., and, S. B. Tinnell. 1993. Antioxidant function of fungal melanin. J. Bacteriol. 175: 7102– 7104.

56. Kurtzman, C. P., and, J. W. Fell. 1997. The Yeasts: A Taxonomical Study. Elsevier, Amsterdam, The Netherlands.

57. Kwon-Chung, K. J., and, J. E. Bennett. 1984. High prevalence of Cryptococcus neoformans var. gattii in tropical and subtropical regions. Zentralbl. Bakteriol. Mikrobiol. Hyg. A 257: 213– 218.

58. Kwon-Chung, K. J.,, T. Boekhout,, J. W. Fell, and, M. Diaz. 2002. Proposal to conserve the name Cryptococcus gattii against C. hondurianus and C. bacillisporus ( Basidiomycota, Hymenomycetes, Tremellomycetidae). Taxon 51: 804– 806.

59. Kwon-Chung, K. J.,, I. Polacheck, and, T. J. Popkin. 1982. Melanin-lacking mutants of Cryptococcus neoformans and their virulence for mice. J. Bacteriol. 150: 1414– 1421.

60. Land, K. M. 2002. Soil amoebae help to unravel fungal pathogenesis. Trends Microbiol. 10: 116.

61. Larsen, R. A.,, P. G. Pappas,, J. Perfect,, J. A. Aberg,, A. Casadevall,, G. A. Cloud, et al. 2005. Phase I evaluation of the safety and pharmacokinetics of murine-derived anticryptococcal antibody 18B7 in subjects with treated cryptococcal meningitis. Antimicrob. Agents Chemother. 49: 952– 958.

62. Lazera, M. S.,, F. D. Pires,, L. Camillo-Coura,, M. M. Nishikawa,, C. C. Bezerra,, L. Trilles, and, B. Wanke. 1996. Natural habitat of Cryptococcus neoformans var. neoformans in decaying wood forming hollows in living trees. J. Med. Vet. Mycol. 34: 127– 131.

63. Levitz, S. M. 2001. Does amoeboid reasoning explain the evolution and maintenance of virulence factors in Cryptococcus neoformans? Proc. Natl. Acad. Sci. USA 98: 14760– 14762.

64. Lipovsky, M. M.,, L. Tsenova,, F. E. Coenjaerts,, G. Kaplan,, R. Cherniak, and, A. I. Hoepelman. 2000. Cryptococcal glucuronoxylomannan delays translocation of leukocytes across the blood-brain barrier in an animal model of acute bacterial meningitis. J. Neuroimmunol. 111: 10– 14.

65. Littman, M. L., and, R. Borok. 1968. Relation of the pigeon to cryptococcosis: natural carrier state, heat resistance and survival of Cryptococcus neoformans. Mycopathol. Mycol. Appl. 35: 329– 345.

66. Liu, H.,, T. R. Cottrell,, L. M. Pierini,, W. E. Goldman, and, T. L. Doering. 2002. RNA interference in the pathogenic fungus Cryptococcus neoformans. Genetics 160: 463– 470.

67. Liu, L.,, R. P. Tewari, and, P. R. Williamson. 1999. Laccase protects Cryptococcus neoformans from antifungal activity of alveolar macrophages. Infect. Immun. 67: 6034– 6039.

68. Loftus, B. J.,, E. Fung,, P. Roncaglia,, D. Rowley,, P. Amedeo,, D. Bruno, et al. 2005. The genome of the basidiomycetous yeast and human pathogen Cryptococcus neoformans. Science 307: 1321– 1324.

69. Love, G. L.,, G. D. Boyd, and, D. L. Greer. 1985. Large Cryptococcus neoformans isolated from brain abscess. J. Clin. Microbiol. 22: 1068– 1070.

70. Lutz, J. E.,, K. V. Clemons, and, D. A. Stevens. 2000. Enhancement of antifungal chemotherapy by interferon-gamma in experimental systemic cryptococcosis. J. Antimicrob. Chemother. 46: 437– 442.

71. Malliaris, S. D.,, J. N. Steenbergen, and, A. Casadevall. 2004. Cryptococcus neoformans var. gattii can exploit Acanthamoeba castellanii for growth. Med. Mycol. 42: 149– 158.

72. Maxson, M. E.,, E. Dadachova,, A. Casadevall, and, O. Zaragoza. 2007. Radial mass density, charge, and epitope distribution in the Cryptococcus neoformans capsule. Eukaryot. Cell 6: 95– 109.

73. McClelland, E. E.,, F. R. Adler,, D. L. Granger, and, W. K. Potts. 2004. Major histocompatibility complex controls the trajectory but not host-specific adaptation during virulence evolution of the pathogenic fungus Cryptococcus neoformans. Proc. Biol. Sci. 271: 1557– 1564.

74. McFadden, D. C.,, M. De Jesus, and, A. Casadevall. 2006. The physical properties of the capsular polysaccharides from cryptococcus neoformans suggest features for capsule construction. J. Biol. Chem. 281: 1868– 1875.

75. Mednick, A. J.,, J. D. Nosanchuk, and, A. Casadevall. 2005. Melanization of Cryptococcus neoformans affects lung inflammatory responses during cryptococcal infection. Infect. Immun. 73: 2012– 2019.

76. Monari, C.,, E. Pericolini,, G. Bistoni,, A. Casadevall,, T. R. Kozel, and, A. Vecchiarelli. 2005. Cryptococcus neoformans capsular glucuronoxylomannan induces expression of fas ligand in macrophages. J. Immunol. 174: 3461– 3468.

77. Mukherjee, J.,, L. A. Pirofski,, M. D. Scharff, and, A. Casadevall. 1993. Antibody-mediated protection in mice with lethal intracerebral Cryptococcus neoformans infection. Proc. Natl. Acad. Sci. USA 90: 3636– 3640.

78. Mukherjee, J.,, M. D. Scharff, and, A. Casadevall. 1992. Protective murine monoclonal antibodies to Cryptococcus neoformans. Infect. Immun. 60: 4534– 4541.

79. Mylonakis, E.,, F. M. Ausubel,, J. R. Perfect,, J. Heitman, and, S. B. Calderwood. 2002. Killing of Caenorhabditis elegans by Cryptococcus neoformans as a model of yeast pathogenesis. Proc. Natl. Acad. Sci. USA 99: 15675– 15680.

80. Mylonakis, E.,, A. Idnurm,, R. Moreno,, J. El Khoury,, J. B. Rottman,, F. M. Ausubel, et al. 2004. Cryptococcus neoformans Kin1 protein kinase homologue, identified through a Caenorhabditis elegans screen, promotes virulence in mammals. Mol. Microbiol. 54: 407– 419.

81. Mylonakis, E.,, R. Moreno,, J. B. El Khoury,, A. Idnurm,, J. Heitman,, S. B. Calderwood, et al. Galleria mellonella as a model system to study Cryptococcus neoformans pathogenesis. Infect. Immun. 73: 3842– 3850.

82. Neilson, J. B.,, M. H. Ivey, and, G. S. Bulmer. 1978. Cryptococcus neoformans: pseudohyphal forms surviving culture with Acanthamoeba polyphaga. Infect. Immun. 20: 262– 266.

83. Nimrichter, L.,, S. Frases,, L. P. Cinelli,, N. B. Viana,, A. Nakouzi,, L. R. Travassos,, A. Casadevall, and, M. L. Rodrigues. 2007. Self-aggregation of Cryptococcus neoformans capsular glucuronoxylomannan is dependent on divalent cations. Eukaryotic Cell, in press.

84. Nosanchuk, J. D.,, A. L. Rosas,, S. C. Lee, and, A. Casadevall. 2000. Melanisation of Cryptococcus neoformans in human brain tissue. Lancet 355: 2049– 2050.

85. Nosanchuk, J. D.,, P. Valadon,, M. Feldmesser, and, A. Casadevall. 1999. Melanization of Cryptococcus neoformans in murine infection. Mol. Cell Biol. 19: 745– 750.

86. Nurudeen, T. A., and, D. G. Ahearn. 1979. Regulation of melanin production by Cryptococcus neoformans. J. Clin. Microbiol. 10: 724– 729.

87. Pierini, L. M., and, T. L. Doering. 2001. Spatial and temporal sequence of capsule construction in Cryptococcus neoformans. Mol. Microbiol. 41: 105– 115.

88. Polacheck, I.,, V. J. Hearing, and, K. J. Kwon-Chung. 1982. Biochemical studies of phenoloxidase and utilization of catecholamines in Cryptococcus neoformans. J. Bacteriol. 150: 1212– 1220.

89. Polacheck, I., and, K. J. Kwon-Chung. 1988. Melanogenesis in Cryptococcus neoformans. J. Gen. Microbiol. 134: 1037– 1041.

90. Polonelli, L.,, A. Casadevall,, Y. Han,, F. Bernardis,, T. N. Kirkland,, R. C. Matthews, et al. 2000. The efficacy of acquired humoral and cellular immunity in the prevention and therapy of experimental fungal infections. Med. Mycol. 38 (Suppl. 1): 281– 292.

91. Reese, A. J., and, T. L. Doering. 2003. Cell wall alpha-1,3-glucan is required to anchor the Cryptococcus neoformans capsule. Mol. Microbiol. 50: 1401– 1409.

92. Reiss, E.,, M. Huppert, and, R. Cherniak. 1985. Characterization of protein and mannan polysaccharide antigens of yeasts, moulds, and actinomycetes. Curr. Top. Med. Mycol. 1: 172– 207.

93. Retini, C.,, A. Vecchiarelli,, C. Monari,, C. Tascini,, F. Bistoni, and, T. R. Kozel. 1996. Capsular polysaccharide of Cryptococcus neoformans induces proinflammatory cytokine release by human neutrophils. Infect. Immun. 64: 2897– 2903.

94. Rhodes, J. C., and, D. H. Howard. 1980. Isolation and characterization of arginine auxotrophs of Cryptococcus neoformans. Infect. Immun. 27: 910– 914.

95. Rivera, J.,, M. Feldmesser,, M. Cammer, and, A. Casadevall. 1998. Organ-dependent variation of capsule thickness in Cryptococcus neoformans during experimental murine infection. Infect. Immun. 66: 5027– 5030.

96. Rodriguez, M. L.,, L. Nimrichter,, D. L. Oliveira,, S. Frases,, K. Miranda,, O. Zaragoza,, M. Alvarez,, A. Nakouzi,, M. Feldmesser, and, A. Casadevall. 2007. Vesicular polysaccharide export in Cryptococcus neoformans is a eukaryotic solution to the problem of fungal trans-cell wall transport. Eukaryot. Cell 6: 48-59.

97. Rodriguez-Zaragoza, S. 1994. Ecology of free-living amoebae. Crit. Rev. Microbiol. 20: 225– 241.

98. Rosas, A. L., and, A. Casadevall. 1997. Melanization affects susceptibility of Cryptococcus neoformans to heat and cold. FEMS Microbiol. Lett. 153: 265– 272.

99. Rosas, A. L., and, A. Casadevall. 2001. Melanization decreases the susceptibility of Cryptococcus neoformans to enzymatic degradation. Mycopathologia 151: 53– 56.

100. Rosas, A. L.,, J. D. Nosanchuk,, M. Feldmesser,, G. M. Cox,, H. C. Mc-Dade, and, A. Casadevall. 2000. Synthesis of polymerized melanin by Cryptococcus neoformans in infected rodents. Infect. Immun. 68: 2845– 2853.

101. Ruiz, A.,, J. B. Neilson, and, G. S. Bulmer. 1982. Control of Cryptococcus neoformans in nature by biotic factors. Sabouraudia 20: 21– 29.

102. Saito, F., and, R. Ikeda. 2005. Killing of cryptococcus neoformans by Staphylococcus aureus: the role of cryptococcal capsular polysaccharide in the fungal-bacteria interaction. Med. Mycol. 43: 603– 612.

103. Shao, X.,, A. Mednick,, M. Alvarez,, N. van Rooijen,, A. Casadevall, and, D. L. Goldman. 2005. An innate immune system cell is a major determinant of species-related susceptibility differences to fungal pneumonia. J. Immunol. 175: 3244– 3251.

104. Shaw, C. E., and, L. Kapica. 1972. Production of diagnostic pigment by phenoloxidase activity of cryptococcus neoformans. Appl. Microbiol. 24: 824– 830.

105. Sheng, S., and, R. Cherniak. 1997. Structure of the 13C-enriched O-deacetylated glucuronoxylomannan of Cryptococcus neoformans serotype A determined by NMR spectroscopy. Carbohydr. Res. 301: 33– 40.

106. Steenbergen, J. N., and, A. Casadevall. 2003. The origin and maintenance of virulence for the human pathogenic fungus Cryptococcus neoformans. Microbes. Infect. 5: 667– 675.

107. Steenbergen, J. N.,, J. D. Nosanchuk,, S. D. Malliaris, and, A. Casadevall. 2003. Cryptococcus neoformans virulence is enhanced after growth in the genetically malleable host Dictyostelium discoideum. Infect. Immun. 71: 4862– 4872.

108. Steenbergen, J. N.,, H. A. Shuman, and, A. Casadevall. 2001. Cryptococcus neoformans interactions with amoebae suggest an explanation for its virulence and intracellular pathogenic strategy in macrophages. Proc. Natl. Acad. Sci. USA 98: 15245– 15250.

109. Steinert, M., and, K. Heuner. 2005. Dictyostelium as host model for pathogenesis. Cell Microbiol. 7: 307– 314.

110. Tang, R. J.,, J. Breger,, A. Idnurm,, K. J. Gerik,, J. K. Lodge,, J. Heitman, et al. 2005. Cryptococcus neoformans gene involved in mammalian pathogenesis identified by a Caenorhabditis elegans progeny-based approach. Infect. Immun. 73: 8219– 8225.

111. Tucker, S. C., and, A. Casadevall. 2002. Replication of Cryptococcus neoformans in macrophages is accompanied by phagosomal permeabilization and accumulation of vesicles containing polysaccharide in the cytoplasm. Proc. Natl. Acad. Sci. USA 99: 3165– 3170.

112. Turner, S. H.,, R. Cherniak,, E. Reiss, and, K. J. Kwon-Chung. 1992. Structural variability in the glucuronoxylomannan of Cryptococcus neoformans serotype A isolates determined by 13C NMR spectroscopy. Carbohydr. Res. 233: 205– 218.

113. van Duin, D.,, A. Casadevall, and, J. D. Nosanchuk. 2002. Melanization of Cryptococcus neoformans and Histoplasma capsulatum reduces their susceptibilities to amphotericin B and caspofungin. Antimicrob. Agents Chemother. 46: 3394– 3400.

114. Vartivarian, S. E.,, E. J. Anaissie,, R. E. Cowart,, H. A. Sprigg,, M. J. Tingler, and, E. S. Jacobson. 1993. Regulation of cryptococcal capsular polysaccharide by iron. J. Infect. Dis. 167: 186– 190.

115. Wang, Y.,, P. Aisen, and, A. Casadevall. 1996. Melanin, melanin “ghosts,” and melanin composition in Cryptococcus neoformans. Infect. Immun. 64: 2420– 2424.

116. Wang, Y., and, A. Casadevall. 1994a. Decreased susceptibility of melanized Cryptococcus neoformans to UV light. Appl. Environ. Microbiol. 60: 3864– 3866.

117. Wang, Y.,, A. Casadevall. 1994b. Growth of Cryptococcus neoformans in presence of L-dopa decreases its susceptibility to amphotericin B. Antimicrob. Agents Chemother. 38: 2648– 2650.

118. Wang, Y., and, A. Casadevall. 1994c. Susceptibility of melanized and nonmelanized Cryptococcus neoformans to nitrogen- and oxygen-derived oxidants. Infect. Immun. 62: 3004– 3007.

119. Williamson, P. R.,, K. Wakamatsu, and, S. Ito. 1998. Melanin biosynthesis in Cryptococcus neoformans. J. Bacteriol. 180: 1570– 1572.

120. Williamson, P. R. 1994. Biochemical and molecular characterization of the diphenol oxidase of Cryptococcus neoformans: identification as a laccase. J. Bacteriol. 176: 656– 664.

121. Winiecka-Krusnell, J., and, E. Linder. 2001. Bacterial infections of free-living amoebae. Res. Microbiol. 152: 613– 619.

122. Zaragoza, O., and, A. Casadevall. 2004. Experimental modulation of capsule size in Cryptococcus neoformans. Biol. Proc. Online. 6: 10– 15.

123. Zaragoza, O.,, B. C. Fries, and, A. Casadevall. 2003a. Induction of capsule growth in Cryptococcus neoformans by mammalian serum and CO(2). Infect. Immun. 71: 6155– 6164.

124. Zaragoza, O.,, C. P. Taborda, and, A. Casadevall. 2003b. The efficacy of complement-mediated phagocytosis of Cryptococcus neoformans is dependent on the location of C3 in the polysaccharide capsule and involves both direct and indirect C3-mediated interactions. Eur. J. Immnunol. 33: 1957– 1967.

125. Zhu, X.,, J. Gibbons,, J. García-Rivera, and, A. Casadevall, and, P. R. Williamson. 2001. Laccase of Cryptococcus neoformans is a cell wall-associated virulence factor. Infect. Immun. 69: 5589– 5596.