Browsing publications of the research group immunology of infection ([HZI]INI) by Subjects
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Age-related susceptibility to Streptococcus pyogenes infection in mice: underlying immune dysfunction and strategy to enhance immunity.Epidemiological studies have shown that the elderly are at higher risk of severe Streptococcus pyogenes infections. In this study, we used a mouse model that displays the age-related loss of resistance to S. pyogenes infection seen in humans to investigate the impaired immune mechanism underlying the age-associated susceptibility to this pathogen. Young (2-3 months old) and aged (>20 months old) BALB/c mice were subcutaneously or intravenously inoculated with S. pyogenes and their capacity to control infection was compared. Aged mice showed faster progression of disease, earlier morbidity, and increased mortality when compared with young animals. Since macrophages are critical for host defence against S. pyogenes, we investigated whether susceptibility of aged mice may be due to an age-associated decline in the functionality of these cells. Our results showed that macrophages from aged mice were as capable as those from young animals to uptake and kill S. pyogenes, but the number of resident tissue macrophages was significantly reduced in the aged host. Treatment of aged mice with macrophage colony-stimulating factor (M-CSF) significantly increased the number of resident macrophages and improved their response to infection. Our results indicate that treatment with M-CSF can restore, at least in part, the mechanisms affected by immunosenescence and enhance the natural resistance of aged mice to infection with S. pyogenes.
Subcutaneous infection with S. aureus in mice reveals association of resistance with influx of neutrophils and Th2 response.Staphylococcus aureus is the leading cause of bacterial skin infection. Once it overcomes the epithelial barrier, it either remains locally controlled or spreads in the dermis causing soft tissue infection. These different courses depend not only on its virulence factors, but also on the immune response of the infected individual. The goal of this study was to identify host factors that influence different outcomes. We, therefore, established comparative analysis of subcutaneous footpad infection with S. aureus (SH1000) in different inbred mouse strains. We found that C57BL/6 mice are more susceptible than BALB/c and DBA/2 mice, reflected by significantly higher footpad swelling and bacterial load, as well as increased dissemination of bacteria into inguinal lymph nodes and kidneys. This susceptibility was associated with lower influx of polymorphonuclear leukocytes (PMNs), but higher secretion of CXCL-2. Remarkably, resistance correlated with S. aureus-specific Th2-cell response in BALB/c and DBA/2 mice, whereas susceptible C57BL/6 mice generated a Th1-cell response. As Th1 cells are able to induce release of CXCL-2, and as CXCL-2 is able to increase the survival of S. aureus within PMNs, interactions between PMNs and Th1 or Th2 cells need to be considered as important mechanisms of resistance in murine soft tissue infection with S. aureus.