title: Bone marrow immunosuppression in Salmonella-infected mice is prolonged following influenza virus infection.
abstract: OBJECTIVE
  It has been shown previously that infection with diverse viruses induces alterations in bone marrow lineage-specific progenitor cells. As complications arising from secondary bacterial infections can adversely affect the host, we investigated whether virally induced hematological alterations could contribute to the enhanced illness observed in such cases.
  
  
  METHODS
  Mice were infected with influenza virus alone or influenza virus followed by a vaccine strain of Salmonella typhimurium. The effects on hematopoiesis were analyzed by fluorescein-activated cell sorting analysis and immunohistology.
  
  
  RESULTS
  Systemic Salmonella typhimurium infection induces depletion of bone marrow erythroid and lymphoid cells. The depletion lasted longer in mice that had been previously infected with influenza virus, compared with mice that had been previously treated with allantoic fluid. Although an increase in splenic lymphoid cells was apparent in the spleens of Salmonella-infected mice, the majority of cells in the enlarged spleens were found to be both immature and mature erythrocytes.
  
  
  CONCLUSIONS
  These results show that bone marrow progenitor cell depletion induced by bacterial infection is prolonged following a viral infection. It is possible that hematological alterations may contribute to the enhanced clinical illness observed in consecutive viral:bacterial infections.
authors.affiliation: The Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire, UK. lisa.hyland@jenner.ac.uk
authors.forename: Lisa
authors.initials: L
authors.lastname: Hyland
authors.forename: Bernardo
authors.initials: B
authors.lastname: Villarreal-Ramos
authors.forename: Ben
authors.initials: B
authors.lastname: Clarke
authors.forename: Bas
authors.initials: B
authors.lastname: Baaten
authors.forename: Sam
authors.initials: S
authors.lastname: Hou
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000473:pathology; D001853:Bone Marrow / Q000473:pathology*; D002452:Cell Count; D041905:Erythroid Cells / Q000473:pathology; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000382:microbiology / Q000473:pathology; D007107:Immune System / Q000382:microbiology* / Q000473:pathology / Q000821:virology; D051379:Mice; D009976:Orthomyxoviridae Infections / Q000209:etiology / Q000276:immunology / Q000473:pathology*; D012481:Salmonella Infections, Animal / Q000150:complications / Q000473:pathology*; D013154:Spleen / Q000473:pathology; D013163:Splenomegaly / Q000209:etiology; D013997:Time Factors