Surfactant Protein D Binds to Coxiella burnetii and Results in a Decrease in Interactions with Murine Alveolar Macrophages

PLoS One. 2015 Sep 14;10(9):e0136699. doi: 10.1371/journal.pone.0136699. eCollection 2015.

Abstract

Coxiella burnetii is a Gram-negative, obligate intracellular bacterium and the causative agent of Q fever. Infections are usually acquired after inhalation of contaminated particles, where C. burnetii infects its cellular target cells, alveolar macrophages. Respiratory pathogens encounter the C-type lectin surfactant protein D (SP-D) during the course of natural infection. SP-D is a component of the innate immune response in the lungs and other mucosal surfaces. Many Gram-negative pulmonary pathogens interact with SP-D, which can cause aggregation, bactericidal effects and aid in bacterial clearance. Here we show that SP-D binds to C. burnetii in a calcium-dependent manner with no detectable bacterial aggregation or bactericidal effects. Since SP-D interactions with bacteria often alter macrophage interactions, it was determined that SP-D treatment resulted in a significant decrease in C. burnetii interactions to a mouse alveolar macrophage model cell line MH-S indicating SP-D causes a significant decrease in phagocytosis. The ability of SP-D to modulate macrophage activation by C. burnetii was tested and it was determined that SP-D does not alter the correlates measured for macrophage activation. Taken together these studies support those demonstrating limited activation of alveolar macrophages with C. burnetii and demonstrate interactions with SP-D participate in reduction of phagocyte attachment and phagocytosis.

Publication types

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

MeSH terms

  • Animals
  • Anti-Infective Agents / pharmacology*
  • Cell Line
  • Coxiella burnetii / drug effects*
  • Coxiella burnetii / pathogenicity
  • Macrophages / immunology
  • Macrophages / microbiology*
  • Mice
  • Phagocytosis
  • Pulmonary Surfactant-Associated Protein D / pharmacology*

Substances

  • Anti-Infective Agents
  • Pulmonary Surfactant-Associated Protein D