title: Physiologic cold shock of Moraxella catarrhalis affects the expression of genes involved in the iron acquisition, serum resistance and immune evasion.
abstract: BACKGROUND
  Moraxella catarrhalis, a major nasopharyngeal pathogen of the human respiratory tract, is exposed to rapid downshifts of environmental temperature when humans breathe cold air. It was previously shown that the prevalence of pharyngeal colonization and respiratory tract infections caused by M. catarrhalis are greatest in winter. The aim of this study was to investigate how M. catarrhalis uses the physiologic exposure to cold air to upregulate pivotal survival systems in the pharynx that may contribute to M. catarrhalis virulence.
  
  
  RESULTS
  A 26°C cold shock induces the expression of genes involved in transferrin and lactoferrin acquisition, and enhances binding of these proteins on the surface of M. catarrhalis. Exposure of M. catarrhalis to 26°C upregulates the expression of UspA2, a major outer membrane protein involved in serum resistance, leading to improved binding of vitronectin which neutralizes the lethal effect of human complement. In contrast, cold shock decreases the expression of Hemagglutinin, a major adhesin, which mediates B cell response, and reduces immunoglobulin D-binding on the surface of M. catarrhalis.
  
  
  CONCLUSIONS
  Cold shock of M. catarrhalis induces the expression of genes involved in iron acquisition, serum resistance and immune evasion. Thus, cold shock at a physiologically relevant temperature of 26°C induces in M. catarrhalis a complex of adaptive mechanisms that enables the bacterium to target their host cellular receptors or soluble effectors and may contribute to enhanced growth, colonization and virulence.
authors.affiliation: Institute for Infectious Diseases, University of Bern, CH-3010 Bern, Switzerland.
authors.forename: Violeta
authors.initials: V
authors.lastname: Spaniol
authors.forename: Rolf
authors.initials: R
authors.lastname: Troller
authors.forename: André
authors.initials: A
authors.lastname: Schaller
authors.forename: Christoph
authors.initials: C
authors.lastname: Aebi
mesh_terms: D001770:Blood Bactericidal Activity; D003080:Cold Temperature; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D057131:Immune Evasion; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000096:biosynthesis; D001936:Moraxella catarrhalis / Q000472:pathogenicity / Q000502:physiology / Q000528:radiation effects*; D013312:Stress, Physiological; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D037521:Virulence Factors; D007501:Iron