title: Aged mice display an altered pulmonary host response to Francisella tularensis live vaccine strain (LVS) infections.
abstract: Aging is a complex phenomenon that has been shown to affect many organ systems including the innate and adaptive immune systems. The current study was designed to examine the potential effect of immunosenescence on the pulmonary immune response using a Francisella tularensis live vaccine strain (LVS) inhalation infection model. F. tularensis is a Gram-negative intracellular pathogen that can cause a severe pneumonia. In this study both young (8-12 week old) and aged (20-24 month old) mice were infected intranasally with LVS. Lung tissues from young and aged mice were used to assess pathology, recruitment of immune cell types and cytokine expression levels at various times post infection. Bacterial burdens were also assessed. Interestingly, the lungs of aged animals harbored fewer organisms at early time points of infection (day 1, day 3) compared with their younger counterparts. In addition, only aged animals displayed small perivascular aggregates at these early time points that appeared mostly mononuclear in nature. However, the kinetics of infiltrating polymorphonuclear neutrophils (PMNs) and increased cytokine levels measured in the bronchial alveolar lavage fluid (BALF) were delayed in infected aged animals relative to young infected animals with neutrophils appearing at day 5 post infection (PI) in the aged animals as opposed to day 3 PI in the young infected animals. Also evident were alterations in the ratios of mononuclear to PMNs at distinct post infection times. The above evidence indicates that aged mice elicit an altered immune response in the lung to respiratory F. tularensis LVS infections compared to their younger counterparts.
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Mares
authors.forename: S S
authors.initials: SS
authors.lastname: Ojeda
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: E G
authors.initials: EG
authors.lastname: Morris
authors.forename: J J
authors.initials: JJ
authors.lastname: Coalson
authors.forename: J M
authors.initials: JM
authors.lastname: Teale
mesh_terms: D000375:Aging / Q000276:immunology*; D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology*; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology / Q000382:microbiology; D016207:Cytokines / Q000276:immunology; D005604:Francisella tularensis / Q000276:immunology*; D008168:Lung / Q000276:immunology / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D018410:Pneumonia, Bacterial / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D014406:Tularemia / Q000276:immunology* / Q000473:pathology
chemical_list: D001428:Bacterial Vaccines; D016207:Cytokines