Cryptococcus neoformans survive and replicate in human microglia

S. C. Lee, Y. Kress, M. L. Zhao, D. W. Dickson, Arturo Casadevall

Research output: Contribution to journalArticle

Abstract

BACKGROUND: Cryptococcus neoformans (CN) is an opportunistic pathogen that can cause fatal meningoencephalitis in patients with immune deficiency. Among the central nervous system (CNS) cells that are infected by CN are perivascular microglia and macrophages. Little is known about the interaction of CN and CNS phagocytes at the cellular level. EXPERIMENTAL DESIGN: To better understand the fate of CN in microglia, we followed Ab-opsonized CN in human fetal microglial culture by phase-contrast microscopy, combined light microscopy and transmission electron microscopy of plastic-embedded monolayers, and immunocytochemistry for localization of capsular Ag. RESULTS: Phase-contrast microscopy revealed that microglia initially internalized and contained Ab-opsonized yeast cells within phagolysosomes. However, CN escaped from microglia and resumed extracellular growth 16 to 24 hours after being phagocytosed. Transmission electron microscopy/1-μ epoxy sections revealed that intracellular CN were localized in two types of phagosomes in microglia: spacious phagosomes (SP) and close-fitting phagosomes (CP). Three lines of evidence indicate that SP are the primary sites for intracellular CN survival and replication: (a) SP contained multiple, budding yeast cells, whereas CP contained only single yeast cells within a tightly bound phagosomal membrane; (b) the number of SP and the number of CN within SP increased considerably at 24 hours compared with at 2 hours; and (c) microglial cultures challenged with heat- or amphotericin B-treated CN had significantly fewer SP than those challenged with live CN. Both SP and CP phagosomes fused with lysosomes, suggesting that CN survival in SP was not due to failure of phagolysosomal fusion. In SP, there was attenuation and diffusion of capsular polysaccharide within the phagosome, whereas in CP the fungal capsules remained compact and homogeneous. Immunocytochemistry with an mAb directed to capsular glucuronoxylomannan supported continued synthesis of polysaccharide within SP. CONCLUSIONS: The results suggest that, in human microglia, CN survive and replicate within SP. Modification of CN capsular polysaccharide within SP may be a contributing factor to this aberrant microglial-CN interaction.

Original languageEnglish (US)
Pages (from-to)871-879
Number of pages9
JournalLaboratory Investigation
Volume73
Issue number6
StatePublished - 1995
Externally publishedYes

Fingerprint

Phagosomes
Cryptococcus neoformans
Microglia
Polysaccharides
Phase-Contrast Microscopy
Fungal Capsules
Transmission Electron Microscopy
Central Nervous System
Yeasts
Immunohistochemistry

Keywords

  • AIDS
  • Capsular polysaccharide
  • Electron microscopy
  • mAb
  • Phagosome

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

Cite this

Lee, S. C., Kress, Y., Zhao, M. L., Dickson, D. W., & Casadevall, A. (1995). Cryptococcus neoformans survive and replicate in human microglia. Laboratory Investigation, 73(6), 871-879.

Cryptococcus neoformans survive and replicate in human microglia. / Lee, S. C.; Kress, Y.; Zhao, M. L.; Dickson, D. W.; Casadevall, Arturo.

In: Laboratory Investigation, Vol. 73, No. 6, 1995, p. 871-879.

Research output: Contribution to journalArticle

Lee, SC, Kress, Y, Zhao, ML, Dickson, DW & Casadevall, A 1995, 'Cryptococcus neoformans survive and replicate in human microglia', Laboratory Investigation, vol. 73, no. 6, pp. 871-879.
Lee, S. C. ; Kress, Y. ; Zhao, M. L. ; Dickson, D. W. ; Casadevall, Arturo. / Cryptococcus neoformans survive and replicate in human microglia. In: Laboratory Investigation. 1995 ; Vol. 73, No. 6. pp. 871-879.
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T1 - Cryptococcus neoformans survive and replicate in human microglia

AU - Lee, S. C.

AU - Kress, Y.

AU - Zhao, M. L.

AU - Dickson, D. W.

AU - Casadevall, Arturo

PY - 1995

Y1 - 1995

N2 - BACKGROUND: Cryptococcus neoformans (CN) is an opportunistic pathogen that can cause fatal meningoencephalitis in patients with immune deficiency. Among the central nervous system (CNS) cells that are infected by CN are perivascular microglia and macrophages. Little is known about the interaction of CN and CNS phagocytes at the cellular level. EXPERIMENTAL DESIGN: To better understand the fate of CN in microglia, we followed Ab-opsonized CN in human fetal microglial culture by phase-contrast microscopy, combined light microscopy and transmission electron microscopy of plastic-embedded monolayers, and immunocytochemistry for localization of capsular Ag. RESULTS: Phase-contrast microscopy revealed that microglia initially internalized and contained Ab-opsonized yeast cells within phagolysosomes. However, CN escaped from microglia and resumed extracellular growth 16 to 24 hours after being phagocytosed. Transmission electron microscopy/1-μ epoxy sections revealed that intracellular CN were localized in two types of phagosomes in microglia: spacious phagosomes (SP) and close-fitting phagosomes (CP). Three lines of evidence indicate that SP are the primary sites for intracellular CN survival and replication: (a) SP contained multiple, budding yeast cells, whereas CP contained only single yeast cells within a tightly bound phagosomal membrane; (b) the number of SP and the number of CN within SP increased considerably at 24 hours compared with at 2 hours; and (c) microglial cultures challenged with heat- or amphotericin B-treated CN had significantly fewer SP than those challenged with live CN. Both SP and CP phagosomes fused with lysosomes, suggesting that CN survival in SP was not due to failure of phagolysosomal fusion. In SP, there was attenuation and diffusion of capsular polysaccharide within the phagosome, whereas in CP the fungal capsules remained compact and homogeneous. Immunocytochemistry with an mAb directed to capsular glucuronoxylomannan supported continued synthesis of polysaccharide within SP. CONCLUSIONS: The results suggest that, in human microglia, CN survive and replicate within SP. Modification of CN capsular polysaccharide within SP may be a contributing factor to this aberrant microglial-CN interaction.

AB - BACKGROUND: Cryptococcus neoformans (CN) is an opportunistic pathogen that can cause fatal meningoencephalitis in patients with immune deficiency. Among the central nervous system (CNS) cells that are infected by CN are perivascular microglia and macrophages. Little is known about the interaction of CN and CNS phagocytes at the cellular level. EXPERIMENTAL DESIGN: To better understand the fate of CN in microglia, we followed Ab-opsonized CN in human fetal microglial culture by phase-contrast microscopy, combined light microscopy and transmission electron microscopy of plastic-embedded monolayers, and immunocytochemistry for localization of capsular Ag. RESULTS: Phase-contrast microscopy revealed that microglia initially internalized and contained Ab-opsonized yeast cells within phagolysosomes. However, CN escaped from microglia and resumed extracellular growth 16 to 24 hours after being phagocytosed. Transmission electron microscopy/1-μ epoxy sections revealed that intracellular CN were localized in two types of phagosomes in microglia: spacious phagosomes (SP) and close-fitting phagosomes (CP). Three lines of evidence indicate that SP are the primary sites for intracellular CN survival and replication: (a) SP contained multiple, budding yeast cells, whereas CP contained only single yeast cells within a tightly bound phagosomal membrane; (b) the number of SP and the number of CN within SP increased considerably at 24 hours compared with at 2 hours; and (c) microglial cultures challenged with heat- or amphotericin B-treated CN had significantly fewer SP than those challenged with live CN. Both SP and CP phagosomes fused with lysosomes, suggesting that CN survival in SP was not due to failure of phagolysosomal fusion. In SP, there was attenuation and diffusion of capsular polysaccharide within the phagosome, whereas in CP the fungal capsules remained compact and homogeneous. Immunocytochemistry with an mAb directed to capsular glucuronoxylomannan supported continued synthesis of polysaccharide within SP. CONCLUSIONS: The results suggest that, in human microglia, CN survive and replicate within SP. Modification of CN capsular polysaccharide within SP may be a contributing factor to this aberrant microglial-CN interaction.

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