Impact of surfactant protein D, interleukin-5, and eosinophilia on Cryptococcosis

Infect Immun. 2014 Feb;82(2):683-93. doi: 10.1128/IAI.00855-13. Epub 2013 Nov 25.

Abstract

Cryptococcus neoformans is an opportunistic fungal pathogen that initiates infection following inhalation. As a result, the pulmonary immune response provides a first line of defense against C. neoformans. Surfactant protein D (SP-D) is an important regulator of pulmonary immune responses and is typically host protective against bacterial and viral respiratory infections. However, SP-D is not protective against C. neoformans. This is evidenced by previous work from our laboratory demonstrating that SP-D-deficient mice infected with C. neoformans have a lower fungal burden and live longer than wild-type (WT) control animals. We hypothesized that SP-D alters susceptibility to C. neoformans by dysregulating the innate pulmonary immune response following infection. Thus, inflammatory cells and cytokines were compared in the bronchoalveolar lavage fluid from WT and SP-D(-/-) mice after C. neoformans infection. Postinfection, mice lacking SP-D have reduced eosinophil infiltration and interleukin-5 (IL-5) in lung lavage fluid. To further explore the interplay of SP-D, eosinophils, and IL-5, mice expressing altered levels of eosinophils and/or IL-5 were infected with C. neoformans to assess the role of these innate immune mediators. IL-5-overexpressing mice have increased pulmonary eosinophilia and are more susceptible to C. neoformans infection than WT mice. Furthermore, susceptibility of SP-D(-/-) mice to C. neoformans infection could be restored to the level of WT mice by increasing IL-5 and eosinophils by crossing the IL-5-overexpressing mice with SP-D(-/-) mice. Together, these studies support the conclusion that SP-D increases susceptibility to C. neoformans infection by promoting C. neoformans-driven pulmonary IL-5 and eosinophil infiltration.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bronchoalveolar Lavage Fluid / cytology
  • Cryptococcosis / immunology*
  • Cryptococcosis / pathology*
  • Cryptococcus neoformans / immunology*
  • Disease Models, Animal
  • Eosinophilia / immunology*
  • Female
  • Interleukin-5 / immunology*
  • Lung / immunology
  • Lung / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Pulmonary Surfactant-Associated Protein D / deficiency
  • Pulmonary Surfactant-Associated Protein D / immunology*

Substances

  • Interleukin-5
  • Pulmonary Surfactant-Associated Protein D