151
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Abdul-Careem MF, Firoz Mian M, Gillgrass AE, Chenoweth MJ, Barra NG, Chan T, Al-Garawi AA, Chew MV, Yue G, Roojen NV, Xing Z, Ashkar AA. FimH, a TLR4 ligand, induces innate antiviral responses in the lung leading to protection against lethal influenza infection in mice. Antiviral Res 2011; 92:346-55. [DOI: 10.1016/j.antiviral.2011.09.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 09/03/2011] [Accepted: 09/07/2011] [Indexed: 10/17/2022]
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152
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Parker D, Prince A. Immunopathogenesis of Staphylococcus aureus pulmonary infection. Semin Immunopathol 2011; 34:281-97. [PMID: 22037948 DOI: 10.1007/s00281-011-0291-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 10/14/2011] [Indexed: 01/23/2023]
Abstract
Staphylococcus aureus is a common human pathogen highly evolved as both a component of the commensal flora and as a major cause of invasive infection. Severe respiratory infection due to staphylococci has been increasing due to the prevalence of more virulent USA300 CA-MRSA strains in the general population. The ability of S. aureus to adapt to the milieu of the respiratory tract has facilitated its emergence as a respiratory pathogen. Its metabolic versatility, the ability to scavenge iron, coordinate gene expression, and the horizontal acquisition of useful genetic elements have all contributed to its success as a component of the respiratory flora, in hospitalized patients, as a complication of influenza and in normal hosts. The expression of surface adhesins facilitates its persistence in the airways. In addition, the highly sophisticated interactions of the multiple S. aureus virulence factors, particularly the α-hemolysin and protein A, with diverse immune effectors in the lung such as ADAM10, TNFR1, EGFR, immunoglobulin, and complement all contribute to the pathogenesis of staphylococcal pneumonia.
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Affiliation(s)
- Dane Parker
- Department of Pediatrics, Columbia University, New York, NY, USA
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153
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Damjanovic D, Divangahi M, Kugathasan K, Small CL, Zganiacz A, Brown EG, Hogaboam CM, Gauldie J, Xing Z. Negative regulation of lung inflammation and immunopathology by TNF-α during acute influenza infection. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 179:2963-76. [PMID: 22001698 DOI: 10.1016/j.ajpath.2011.09.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 08/22/2011] [Accepted: 09/01/2011] [Indexed: 02/06/2023]
Abstract
Lung immunopathology is the main cause of influenza-mediated morbidity and death, and much of its molecular mechanisms remain unclear. Whereas tumor necrosis factor-α (TNF-α) is traditionally considered a proinflammatory cytokine, its role in influenza immunopathology is unresolved. We have investigated this issue by using a model of acute H1N1 influenza infection established in wild-type and TNF-α-deficient mice and evaluated lung viral clearance, inflammatory responses, and immunopathology. Whereas TNF-α was up-regulated in the lung after influenza infection, it was not required for normal influenza viral clearance. However, TNF-α deficiency led not only to a greater extent of illness but also to heightened lung immunopathology and tissue remodeling. The severe lung immunopathology was associated with increased inflammatory cell infiltration, anti-influenza adaptive immune responses, and expression of cytokines such as monocyte chemoattractant protein-1 (MCP-1) and fibrotic growth factor, TGF-β1. Thus, in vivo neutralization of MCP-1 markedly attenuated lung immunopathology and blunted TGF-β1 production following influenza infection in these hosts. On the other hand, in vivo transgenic expression of MCP-1 worsened lung immunopathology following influenza infection in wild-type hosts. Thus, TNF-α is dispensable for influenza clearance; however, different from the traditional belief, this cytokine is critically required for negatively regulating the extent of lung immunopathology during acute influenza infection.
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Affiliation(s)
- Daniela Damjanovic
- Department of Pathology and Molecular Medicine & McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada
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154
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Eisele NA, Anderson DM. Host Defense and the Airway Epithelium: Frontline Responses That Protect against Bacterial Invasion and Pneumonia. J Pathog 2011; 2011:249802. [PMID: 22567325 PMCID: PMC3335569 DOI: 10.4061/2011/249802] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 07/18/2011] [Accepted: 07/21/2011] [Indexed: 01/31/2023] Open
Abstract
Airway epithelial cells are the first line of defense against invading microbes, and they protect themselves through the production of carbohydrate and protein matrices concentrated with antimicrobial products. In addition, they act as sentinels, expressing pattern recognition receptors that become activated upon sensing bacterial products and stimulate downstream recruitment and activation of immune cells which clear invading microbes. Bacterial pathogens that successfully colonize the lungs must resist these mechanisms or inhibit their production, penetrate the epithelial barrier, and be prepared to resist a barrage of inflammation. Despite the enormous task at hand, relatively few virulence factors coordinate the battle with the epithelium while simultaneously providing resistance to inflammatory cells and causing injury to the lung. Here we review mechanisms whereby airway epithelial cells recognize pathogens and activate a program of antibacterial pathways to prevent colonization of the lung, along with a few examples of how bacteria disrupt these responses to cause pneumonia.
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Affiliation(s)
- Nicholas A. Eisele
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO 65211, USA
- The Laboratory for Infectious Disease Research, University of Missouri, Columbia, MO 65211, USA
| | - Deborah M. Anderson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
- The Laboratory for Infectious Disease Research, University of Missouri, Columbia, MO 65211, USA
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155
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Listeria monocytogenes Meningitis With Unilateral Abducens Palsy Complicating Novel H1N1 Influenza in a Toddler. INFECTIOUS DISEASES IN CLINICAL PRACTICE 2011. [DOI: 10.1097/ipc.0b013e3182041ff2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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156
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Acuna-Soto R, Viboud C, Chowell G. Influenza and pneumonia mortality in 66 large cities in the United States in years surrounding the 1918 pandemic. PLoS One 2011; 6:e23467. [PMID: 21886792 PMCID: PMC3158768 DOI: 10.1371/journal.pone.0023467] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 07/18/2011] [Indexed: 11/18/2022] Open
Abstract
The 1918 influenza pandemic was a major epidemiological event of the twentieth century resulting in at least twenty million deaths worldwide; however, despite its historical, epidemiological, and biological relevance, it remains poorly understood. Here we examine the relationship between annual pneumonia and influenza death rates in the pre-pandemic (1910-17) and pandemic (1918-20) periods and the scaling of mortality with latitude, longitude and population size, using data from 66 large cities of the United States. The mean pre-pandemic pneumonia death rates were highly associated with pneumonia death rates during the pandemic period (Spearman ρ = 0.64-0.72; P<0.001). By contrast, there was a weak correlation between pre-pandemic and pandemic influenza mortality rates. Pneumonia mortality rates partially explained influenza mortality rates in 1918 (ρ = 0.34, P = 0.005) but not during any other year. Pneumonia death counts followed a linear relationship with population size in all study years, suggesting that pneumonia death rates were homogeneous across the range of population sizes studied. By contrast, influenza death counts followed a power law relationship with a scaling exponent of ∼0.81 (95%CI: 0.71, 0.91) in 1918, suggesting that smaller cities experienced worst outcomes during the pandemic. A linear relationship was observed for all other years. Our study suggests that mortality associated with the 1918-20 influenza pandemic was in part predetermined by pre-pandemic pneumonia death rates in 66 large US cities, perhaps through the impact of the physical and social structure of each city. Smaller cities suffered a disproportionately high per capita influenza mortality burden than larger ones in 1918, while city size did not affect pneumonia mortality rates in the pre-pandemic and pandemic periods.
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Affiliation(s)
- Rodolfo Acuna-Soto
- Departamento de Microbiologia y Parasitologia, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México.
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157
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Wu Y, Mao H, Ling MT, Chow KH, Ho PL, Tu W, Lau YL. Successive influenza virus infection and Streptococcus pneumoniae stimulation alter human dendritic cell function. BMC Infect Dis 2011; 11:201. [PMID: 21771345 PMCID: PMC3146832 DOI: 10.1186/1471-2334-11-201] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 07/20/2011] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Influenza virus is a major cause of respiratory disease worldwide and Streptococcus pneumoniae infection associated with influenza often leads to severe complications. Dendritic cells are key antigen presenting cells but its role in such co-infection is unclear. METHODS In this study, human monocyte derived-dentritic cells were either concurrently or successively challenged with the combination of live influenza virus and heat killed pneumococcus to mimic the viral pneumococcal infection. Dendritic cell viability, phenotypic maturation and cytokine production were then examined. RESULTS The challenge of influenza virus and pneumococcus altered dendritic cell functions dependent on the time interval between the successive challenge of influenza virus and pneumococcus, as well as the doses of pneumococcus. When dendritic cells were exposed to pneumococcus at 6 hr, but not 0 hr nor 24 hr after influenza virus infection, both virus and pneumococcus treated dendritic cells had greater cell apoptosis and expressed higher CD83 and CD86 than dendritic cells infected with influenza virus alone. Dendritic cells produced pro-inflammatory cytokines: TNF-α, IL-12 and IFN-γ synergistically to the successive viral and pneumococcal challenge. Whereas prior influenza virus infection suppressed the IL-10 response independent of the timing of the subsequent pneumococcal stimulation. CONCLUSIONS Our results demonstrated that successive challenge of dendritic cells with influenza virus and pneumococcus resulted in synergistic up-regulation of pro-inflammatory cytokines with simultaneous down-regulation of anti-inflammatory cytokine, which may explain the immuno-pathogenesis of this important co-infection.
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Affiliation(s)
- Yuet Wu
- Department of Paediatrics, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China
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158
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Snelgrove RJ, Godlee A, Hussell T. Airway immune homeostasis and implications for influenza-induced inflammation. Trends Immunol 2011; 32:328-34. [PMID: 21612981 DOI: 10.1016/j.it.2011.04.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 04/15/2011] [Accepted: 04/18/2011] [Indexed: 10/18/2022]
Abstract
The lung is exposed to a myriad of innocuous antigens on a daily basis and must maintain a state of immune ignorance or tolerance to these harmless stimuli to retain pulmonary homeostasis and to prevent potentially fatal immunopathology. Here, we examine how, in the lower airways, resident cell populations contribute to the immune regulatory strategies that restrain inflammation. During influenza infection, these suppressive signals must be overcome to elicit a protective immune response that eliminates the virus. We also discuss how, after resolution of infection, the lung does not return to the original homeostatic state, and how the induced altered state can persist for long periods, which leaves the lung more susceptible to other infectious insults.
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Affiliation(s)
- Robert J Snelgrove
- Imperial College London, Leukocyte Biology Section, National Heart and Lung Institute, London, SW7 2AZ, UK
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159
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Ballinger MN, Standiford TJ. Postinfluenza bacterial pneumonia: host defenses gone awry. J Interferon Cytokine Res 2011; 30:643-52. [PMID: 20726789 DOI: 10.1089/jir.2010.0049] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Influenza is a common respiratory pathogen causing both seasonal and pandemic disease. Influenza infection predisposes the host to secondary bacterial infection of the respiratory tract, which is a major cause of both morbidity and mortality in flu-related disease. In this review, we will discuss innate and adaptive antiviral responses during influenza infection, and review how these responses modulate protective immunity against secondary bacterial pathogens of the lung. Specific emphasis will be placed on implications of bacterial superinfection and mechanisms involved.
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Affiliation(s)
- Megan N Ballinger
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, The University of Michigan Medical School, Ann Arbor, Michigan, USA
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160
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Birck MM, Pesonen E, Odermarsky M, Hansen AK, Persson K, Frikke-Schmidt H, Heegaard PMH, Liuba P. Infection-induced coronary dysfunction and systemic inflammation in piglets are dampened in hypercholesterolemic milieu. Am J Physiol Heart Circ Physiol 2011; 300:H1595-601. [DOI: 10.1152/ajpheart.01253.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The synergism of infection with conventional cardiovascular risk factors in atherosclerosis is much debated. We hypothesized that coronary arterial injury correlates with infection recurrence and pathogen burden and is further aggravated by hypercholesterolemia. Forty-two Göttingen minipigs were assigned to repeated intratracheal inoculation of PBS, Chlamydia pneumoniae (Cpn), or both Cpn and influenza virus at 8, 11, and 14 wk of age. Animals were fed either standard or 2% cholesterol diet (chol-diet). At 19 wk of age coronary vasomotor responses to acetylcholine (ACh) and adenosine were assessed in vivo and blood and tissue samples were collected. Nonparametric tests were used to compare the groups. In cholesterol-fed animals, total cholesterol/HDL was significantly increased in infected animals compared with noninfected animals [3.13 (2.17–3.38) vs. 2.03 (1.53–2.41), respectively; P = 0.01]. C-reactive protein (CRP) rose in infected animals [10.60 (4.96–18.00) vs. 2.47 (1.44–3.01) μg/ml in noninfected; P < 0.01] without significant difference between the mono- and coinfected groups. Among coinfected animals, both CRP and haptoglobin were lower in those fed chol-diet than in those fed standard diet ( P < 0.05). The vasoconstricting response to ACh was most prominent in coinfected animals {769.3 (594–1,129) cm; P = 0.03 vs. noninfected [342 (309–455) cm] and P = 0.07 vs. monoinfected [415 (252.5–971.8) cm]}. Among monoinfected animals, similar to CRP, a trend for less vasoconstriction was observed in those fed chol-diet ( P = 0.08). Coinfection of piglets appears to be associated with more pronounced coronary muscarinic vasomotor dysfunction. In monoinfected animals, use of chol-diet seems to dampen both coronary dysfunction and systemic inflammation induced by infection.
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Affiliation(s)
- Malene M. Birck
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Erkki Pesonen
- Division of Pediatric Cardiology, Department of Pediatrics, Skåne University Hospital, Lund and
| | - Michal Odermarsky
- Division of Pediatric Cardiology, Department of Pediatrics, Skåne University Hospital, Lund and
| | - Axel K. Hansen
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Kenneth Persson
- Department of Microbiology, Skåne University Hospital, Malmö, Sweden; and
| | - Henriette Frikke-Schmidt
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Peter M. H. Heegaard
- Innate Immunology Group, National Veterinary Institute, Technical University of Denmark, Copenhagen, Denmark
| | - Petru Liuba
- Division of Pediatric Cardiology, Department of Pediatrics, Skåne University Hospital, Lund and
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161
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Analysis of murine genetic predisposition to pneumococcal infection reveals a critical role of alveolar macrophages in maintaining the sterility of the lower respiratory tract. Infect Immun 2011; 79:1842-7. [PMID: 21321074 DOI: 10.1128/iai.01143-10] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The study of pathogenic mechanisms of disease can be greatly facilitated by studying genetic differences in susceptibility to infection. In the present study, we compared the severity of pneumococcal infection in C57BL/6 (B6) and 129Sv mice. The results showed that 129Sv mice were remarkably more susceptible to pneumococcal infection than B6 mice. Bacterial clearance, proinflammatory mediators, leukocyte recruitment, and phagocyte activities were measured to examine potential immune factors associated with differences in susceptibility to pneumococcal infection. The greater susceptibility of 129Sv mice was associated only with inadequate alveolar macrophage bacterial killing, as indicated by significantly decreased initial bacterial clearance from the respiratory tract. Effective pneumococcal clearance was not dependent upon Toll-like receptor 2 (TLR2) expression, oxidative stress, or matrix metallopeptidase 12 (MMP-12) expression. Furthermore, phagocytosis analysis suggested that the deficiency found in 129Sv alveolar macrophages was not due to a lack of bacterial recognition but, rather, to reduced bacterial uptake. In conclusion, our findings indicate a crucial role of alveolar macrophage phagocytosis during innate defense against pneumococcal infection, which may explain the association of host genetic risk factors with predisposition to pneumococcal infection.
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162
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Kudva A, Scheller EV, Robinson KM, Crowe CR, Choi SM, Slight SR, Khader SA, Dubin PJ, Enelow RI, Kolls JK, Alcorn JF. Influenza A inhibits Th17-mediated host defense against bacterial pneumonia in mice. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2011; 186:1666-1674. [PMID: 21178015 PMCID: PMC4275066 DOI: 10.4049/jimmunol.1002194] [Citation(s) in RCA: 277] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Staphylococcus aureus is a significant cause of hospital and community acquired pneumonia and causes secondary infection after influenza A. Recently, patients with hyper-IgE syndrome, who often present with S. aureus infections of the lung and skin, were found to have mutations in STAT3, required for Th17 immunity, suggesting a potential critical role for Th17 cells in S. aureus pneumonia. Indeed, IL-17R(-/-) and IL-22(-/-) mice displayed impaired bacterial clearance of S. aureus compared with that of wild-type mice. Mice challenged with influenza A PR/8/34 H1N1 and subsequently with S. aureus had increased inflammation and decreased clearance of both virus and bacteria. Coinfection resulted in greater type I and II IFN production in the lung compared with that with virus infection alone. Importantly, influenza A coinfection resulted in substantially decreased IL-17, IL-22, and IL-23 production after S. aureus infection. The decrease in S. aureus-induced IL-17, IL-22, and IL-23 was independent of type II IFN but required type I IFN production in influenza A-infected mice. Furthermore, overexpression of IL-23 in influenza A, S. aureus-coinfected mice rescued the induction of IL-17 and IL-22 and markedly improved bacterial clearance. These data indicate a novel mechanism by which influenza A-induced type I IFNs inhibit Th17 immunity and increase susceptibility to secondary bacterial pneumonia.
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MESH Headings
- Animals
- Cells, Cultured
- Genetic Predisposition to Disease
- Humans
- Influenza A Virus, H1N1 Subtype/immunology
- Interferon Type I/administration & dosage
- Interferon Type I/biosynthesis
- Interleukin-17/antagonists & inhibitors
- Interleukin-17/deficiency
- Interleukin-17/physiology
- Interleukin-23/antagonists & inhibitors
- Interleukins/antagonists & inhibitors
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Orthomyxoviridae Infections/genetics
- Orthomyxoviridae Infections/immunology
- Orthomyxoviridae Infections/microbiology
- Pneumonia, Bacterial/genetics
- Pneumonia, Bacterial/immunology
- Pneumonia, Bacterial/virology
- Signal Transduction/genetics
- Signal Transduction/immunology
- Staphylococcal Infections/genetics
- Staphylococcal Infections/immunology
- Staphylococcal Infections/virology
- Staphylococcus aureus/immunology
- T-Lymphocytes, Helper-Inducer/immunology
- T-Lymphocytes, Helper-Inducer/metabolism
- T-Lymphocytes, Helper-Inducer/virology
- Interleukin-22
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Affiliation(s)
- Anupa Kudva
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Erich V. Scheller
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Keven M. Robinson
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Chris R. Crowe
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Sun Mi Choi
- Department of Genetics, Lousiana State University Health Sciences Center, New Orleans, LA 70112
| | - Samantha R. Slight
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Shabaana A. Khader
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | - Patricia J. Dubin
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
| | | | - Jay K. Kolls
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
- Department of Genetics, Lousiana State University Health Sciences Center, New Orleans, LA 70112
| | - John F. Alcorn
- Department of Pediatrics, Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224
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163
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Iverson AR, Boyd KL, McAuley JL, Plano LR, Hart ME, McCullers JA. Influenza virus primes mice for pneumonia from Staphylococcus aureus. J Infect Dis 2011; 203:880-8. [PMID: 21278211 DOI: 10.1093/infdis/jiq113] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Superinfections from Staphylococcus aureus following influenza are an increasing concern. We assessed several laboratory and clinical strains in a mouse coinfection model with influenza virus. A methicillin-resistant USA300 clone and several recent clinical strains from patients with necrotizing pneumonia caused high mortality following influenza virus infection in mice. Both viral and bacterial lung titers were enhanced during coinfections compared with single infections. However, differences in titers did not correspond with differences in disease outcomes in a comparison of superinfections from a highly pathogenic strain with those from a poorly pathogenic strain. These strains did differ, however, in expression of Panton-Valentine leukocidin and in the degree of inflammatory lung damage each engendered. The viral cytotoxin PB1-F2 contributed to the negative outcomes. These data suggest that additional study of specific bacterial virulence factors involved in the pathogenesis of inflammation and lung damage during coinfections is needed.
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Affiliation(s)
- Amy R Iverson
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN 38105, USA
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164
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Abstract
Bacterial super-infections contribute to the significant morbidity and mortality associated with influenza and other respiratory virus infections. There are robust animal model data, but only limited clinical information on the effectiveness of licensed antiviral agents for the treatment of bacterial complications of influenza. The association of secondary bacterial pathogens with fatal pneumonia during the recent H1N1 influenza pandemic highlights the need for new development in this area. Basic and clinical research into viral-bacterial interactions over the past decade has revealed several mechanisms that underlie this synergism. By applying these insights to antiviral drug development, the potential exists to improve outcomes by means other than direct inhibition of the virus.
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Affiliation(s)
- Jonathan A McCullers
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA.
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