Staphylococcus aureus Elicits Marked Alterations in the Airway Proteome during Early Pneumonia

Division of Infectious Diseases, Center for Childhood Infections and Prematurity Research, University of Washington School of Medicine, Seattle, Washington, USA.
Infection and immunity (Impact Factor: 3.73). 11/2008; 76(12):5862-72. DOI: 10.1128/IAI.00865-08
Source: PubMed


Pneumonia caused by Staphylococcus aureus is a growing concern in the health care community. We hypothesized that characterization of the early innate immune response
to bacteria in the lungs would provide insight into the mechanisms used by the host to protect itself from infection. An adult
mouse model of Staphylococcus aureus pneumonia was utilized to define the early events in the innate immune response and to assess the changes in the airway proteome
during the first 6 h of pneumonia. S. aureus actively replicated in the lungs of mice inoculated intranasally under anesthesia to cause significant morbidity and mortality.
By 6 h postinoculation, the release of proinflammatory cytokines caused effective recruitment of neutrophils to the airway.
Neutrophil influx, loss of alveolar architecture, and consolidated pneumonia were observed histologically 6 h postinoculation.
Bronchoalveolar lavage fluids from mice inoculated with phosphate-buffered saline (PBS) or S. aureus were depleted of overabundant proteins and subjected to strong cation exchange fractionation followed by liquid chromatography
and tandem mass spectrometry to identify the proteins present in the airway. No significant changes in response to PBS inoculation
or 30 min following S. aureus inoculation were observed. However, a dramatic increase in extracellular proteins was observed 6 h postinoculation with S. aureus, with the increase dominated by inflammatory and coagulation proteins. The data presented here provide a comprehensive evaluation
of the rapid and vigorous innate immune response mounted in the host airway during the earliest stages of S. aureus pneumonia.

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Available from: Shawn J Skerrett, Sep 11, 2014
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    • "In the skin, a robust inflammatory response is necessary and desirable to wall off and control an infection [15], [16]. However, during a lung infection, a similarly robust inflammatory response is deleterious leading to many of the hallmarks of pneumonia [44], [45]. The exact mechanism that leads to the differential immune response to AT depending on the site of infection has not been elucidated. "
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    ABSTRACT: An optimal host response against Staphylococcus aureus skin and soft tissue infections (SSTI) is dependent on IL-1β and IL-17 mediated abscess formation. Alpha toxin (AT), an essential virulence factor for SSTI, has been reported to damage tissue integrity; however its effect on the immune response has not been investigated. Here, we demonstrate that infection with USA300 AT isogenic mutant (Δhla), or passive immunization with an AT neutralizing mAb, 2A3, 24 h prior to infection with wild type USA300 (WT), resulted in dermonecrotic lesion size reduction, and robust neutrophil infiltration. Infiltration correlates with increase in proinflammatory cytokines and chemokines, as well as enhanced bacterial clearance relative to immunization with a negative control mAb. In addition, infection with Δhla, or with WT +2A3, resulted in an early influx of innate IL-17(+)γδT cells and a more rapid induction of an adaptive immune response as measured by Th1 and Th17 cell recruitment at the site of infection. These results are the first direct evidence of a role for AT in subverting the innate and adaptive immune responses during a S. aureus SSTI. Further, these effects of AT can be overcome with a high affinity anti-AT mAb resulting in a reduction in disease severity.
    Full-text · Article · Oct 2013 · PLoS ONE
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    • "Montgomery et al. (2009) employed a rat necrotizing MRSA-mediated pneumonia model to study the transcription of 84 genes mediating the early inflammatory response in the lung [5]. Ventura et al. (2008) utilized a mouse model of MRSA pneumonia to define the early events in the innate immune response and assess the changes in the airway proteome during the first 6 hours (h) of pneumonia [6]. In both rats [5] and mice [6], the expression of cytokines and chemokines was greatest 6 h after inoculation of MRSA and decreased thereafter. "
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    ABSTRACT: Community associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging threat to human health throughout the world. Rodent MRSA pneumonia models mainly focus on the early innate immune responses to MRSA lung infection. However, the molecular pattern and mechanisms of recovery from MRSA lung infection are largely unknown. In this study, a sublethal mouse MRSA pneumonia model was employed to investigate late events during the recovery from MRSA lung infection. We compared lung bacterial clearance, bronchoalveolar lavage fluid (BALF) characterization, lung histology, lung cell proliferation, lung vascular permeability and lung gene expression profiling between days 1 and 3 post MRSA lung infection. Compared to day 1 post infection, bacterial colony counts, BALF total cell number and BALF protein concentration significantly decreased at day 3 post infection. Lung cDNA microarray analysis identified 47 significantly up-regulated and 35 down-regulated genes (p<0.01, 1.5 fold change [up and down]). The pattern of gene expression suggests that lung recovery is characterized by enhanced cell division, vascularization, wound healing and adjustment of host adaptive immune responses. Proliferation assay by PCNA staining further confirmed that at day 3 lungs have significantly higher cell proliferation than at day 1. Furthermore, at day 3 lungs displayed significantly lower levels of vascular permeability to albumin, compared to day 1. Collectively, this data helps us elucidate the molecular mechanisms of the recovery after MRSA lung infection.
    Full-text · Article · Aug 2013 · PLoS ONE
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    • "To our knowledge, this study was the first to show the genome-wide lung gene expression profile changes at Day 1 and Day 3 post MRSA infection. Previously it was shown that inflammatory and blood coagulation components dominated the early response to MRSA in the lungs or airways [5,27]. Our microarray data not only confirmed inflammatory and blood components were significantly modulated by MRSA infection, but also revealed more transcriptional events during MRSA pneumonia. "
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    ABSTRACT: Linezolid (LZD) is beneficial to patients with MRSA pneumonia, but whether and how LZD influences global host lung immune responses at the mRNA level during MRSA-mediated pneumonia is still unknown. A lethal mouse model of MRSA pneumonia mediated by USA300 was employed to study the influence of LZD on survival, while the sublethal mouse model was used to examine the effect of LZD on bacterial clearance and lung gene expression during MRSA pneumonia. LZD (100mg/kg/day, IP) was given to C57Bl6 mice for three days. On Day 1 and Day 3 post infection, bronchoalveolar lavage fluid (BALF) protein concentration and levels of cytokines including IL6, TNFα, IL1β, Interferon-γ and IL17 were measured. In the sublethal model, left lungs were used to determine bacterial clearance and right lungs for whole-genome transcriptional profiling of lung immune responses. LZD therapy significantly improved survival and bacterial clearance. It also significantly decreased BALF protein concentration and levels of cytokines including IL6, IL1β, Interferon-γ and IL17. No significant gene expression changes in the mouse lungs were associated with LZD therapy. LZD is beneficial to MRSA pneumonia, but it does not modulate host lung immune responses at the transcriptional level.
    Full-text · Article · Jun 2013 · PLoS ONE
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