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Experimental modulation of capsule size in Cryptococcus neoformans


Experimental modulation of capsule size is an important technique for the study of the virulence of the encapsulated pathogen Cryptococcus neoformans. In this paper, we summarize the techniques available for experimental modulation of capsule size in this yeast and describe improved methods to induce capsule size changes. The response of the yeast to the various stimuli is highly dependent on the cryptococcal strain. A high CO2 atmosphere and a low iron concentration have been used classically to increase capsule size. Unfortunately, these stimuli are not reliable for inducing capsular enlargement in all strains. Recently we have identified new and simpler conditions for inducing capsule enlargement that consistently elicited this effect. Specifically, we noted that mammalian serum or diluted Sabouraud broth in MOPS buffer pH 7.3 efficiently induced capsule growth. Media that slowed the growth rate of the yeast correlated with an increase in capsule size. Finally, we summarize the most commonly used media that induce capsule growth in C. neoformans.


  1. Casadevall A, Perfect JR. Cryptococcus neoformans (Press A, Ed.), ASM Press, Washington DC, 1998.

    Google Scholar 

  2. Cherniak R, Sundstrom JB. Polysaccharide antigens of the capsule of Cryptocccus neoformans. Infect Immun 1994; 62:1507–1512.

    PubMed  CAS  Google Scholar 

  3. Macher AM, Bennett JE, Gadek JE, Frank MM. Complement depletion in cryptococcal sepsis. J Immunol 1978; 120:1686–1690.

    PubMed  CAS  Google Scholar 

  4. Murphy JW, Cozad GC. Immunological unresponsiveness induced by cryptococcal capsular polysaccharide assayed by the hemolytic plaque technique. Infect Immun 1972; 5:896–901.

    PubMed  CAS  Google Scholar 

  5. Kozel TR, Gulley WF, Cazin J Jr. Immune response to Cryptococcus neoformans soluble polysaccharide: immunological unresponsiveness. Infect Immun 1977; 18:701–707.

    PubMed  CAS  Google Scholar 

  6. Dong ZM, Murphy JW. Effects of the two varieties of Cryptococcus neoformans cells and culture filtrate antigens on neutrophil locomotion. Infect Immun 1995; 63:2632–2644.

    PubMed  CAS  Google Scholar 

  7. Kozel TR, Pfrommer GS, Guerlain AS, Highison BA, Highison GJ. Strain variation in phagocytosis of Cryptococcus neoformans: dissociation of susceptibility to phagocytosis from activation and binding of opsonic fragments of C3. Infect Immun 1988; 56:2794–2800.

    PubMed  CAS  Google Scholar 

  8. Bolaños B, Mitchell TG. Killing of Cryptococcus neoformans by rat alveolar macrophages. J Med Vet Mycol 1989; 27:219–228.

    Article  PubMed  Google Scholar 

  9. Zaragoza O, Taborda CP, Casadevall A. 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. Euro J Immnunol 2003; 33:1957–1967.

    Article  CAS  Google Scholar 

  10. Littman M. Capsule synthesis by Cryptococcus neoformans. Trans NY Acad Sci 1958; 20:623–648.

    CAS  Google Scholar 

  11. Granger DL, Perfect JR, Durack DT. Virulence of Cryptococcus neoformans. Regulation of capsule synthesis by carbon dioxide. J Clin Invest 1985; 76:508–516.

    Article  PubMed  CAS  Google Scholar 

  12. Vartivarian SE, Anaissie EJ, Cowart RE, Sprigg HA, Tingler MJ, Jacobson ES. Regulation of cryptococcal capsular polysaccharide by iron. J Infect Dis 1993; 167:186–190.

    PubMed  CAS  Google Scholar 

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

    PubMed  CAS  Google Scholar 

  14. Cruickshank JG, Cavill R, Jelbert M. Cryptococcus neoformans of unusual morphology. Appl Microbiol 1973; 25:309–312.

    PubMed  CAS  Google Scholar 

  15. Love GL, Boyd GD, Greer DL. Large Cryptococcus neoformans isolated from brain abscess. J Clin Microbiol 1985; 22:1068–1070.

    PubMed  CAS  Google Scholar 

  16. Rivera J, Feldmesser M, Cammer M, Casadevall A. Organdependent variation of capsule thickness in Cryptococcus neoformans during experimental murine infection. Infect Immun 1998; 66:5027–5030.

    PubMed  CAS  Google Scholar 

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

    PubMed  CAS  Google Scholar 

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

    Article  PubMed  CAS  Google Scholar 

  19. Tripp C, Ruiz A, Bulmer GS. Culture of Cryptococcus neoformans in the nonencapsulated state. Mycopathologia 1981; 76:129–131.

    Article  PubMed  CAS  Google Scholar 

  20. Farhi F, Bulmer GS, Tacker JR. Cryptococcus neoformans: The not-so-encapsulated yeast. Infect Immun 1970; 1:526–531.

    PubMed  CAS  Google Scholar 

  21. Dykstra MA, Friedman L, Murphy JW. Capsule size of Cryptococcus neoformans: control and relationship to virulence. Infect Immun 1977; 16:129–135.

    PubMed  CAS  Google Scholar 

  22. Jacobson ES, Tingler MJ, Quynn PL. Effect of hypertonic solutes upon the polysaccharide capsule in Cryptococcus neoformans. Mycoses 1989; 32:14–23.

    Article  PubMed  CAS  Google Scholar 

  23. Jacobson ES, Compton GM. Discordant regulation of phenoloxidase and capsular polysaccharide in Cryptococcus neoformans. J Med Vet Mycol 1996; 34:289–291.

    Article  PubMed  CAS  Google Scholar 

  24. D’Souza CA, Alspaugh JA, Yue C, Harashima T, Cox GM, Perfect JR, Heitman J. Cyclic AMP-dependent protein kinase controls virulence of the fungal pathogen Cryptococcus neoformans. Mol Cell Biol 2001; 21:3179–3191.

    Article  PubMed  CAS  Google Scholar 

  25. Alspaugh JA, Pukkila-Worley R, Harashima T, Cavallo LM, Funnell D, Cox GM, Perfect JR, Kronstad JW, Heitman J. Adenylyl cyclase functions downstream of the Galpha protein Gpa1 and controls mating and pathogenicity of Cryptococcus neoformans. Eukaryot Cell 2002; 1:75–84.

    Article  PubMed  CAS  Google Scholar 

  26. Anna EJ. Rapid in vitro capsule production by cryptococci. Am J Med Technol 1979; 45:585–588.

    PubMed  CAS  Google Scholar 

  27. Weinstein DL, Holmes RK, O’Brien AD. Effects of iron and temperature on Shiga-like toxin I production by Escherichia coli. Infect Immun 1988; 56:106–111.

    PubMed  CAS  Google Scholar 

  28. Bjorn MJ, Iglewski BH, Ives SK, Sadoff JC, Vasil ML. Effect of iron on yields of exotoxin A in cultures of Pseudomonas aeruginosa PA-103. Infect Immun 1978; 19:785–791.

    PubMed  CAS  Google Scholar 

  29. Nyhus KJ, Jacobson ES. Genetic and physiologic characterization of ferric/cupric reductase constitutive mutants of Cryptococcus neoformans. Infect Immun 1999; 67:2357–2365.

    PubMed  CAS  Google Scholar 

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Correspondence to Oscar Zaragoza.

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Published: March 3, 2004

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Zaragoza, O., Casadevall, A. Experimental modulation of capsule size in Cryptococcus neoformans . Biol. Proced. Online 6, 10–15 (2004).

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Indexing terms

  • Cryptococcus neoformans
  • Infection
  • Virulence Factor