[Infection and asthma].

Area of Science:

• Immunology
• Pulmonology
• Infectious Diseases

Background:

• Infections are common in all asthma stages and a major cause of exacerbations.
• Bacterial and viral infections significantly impact asthma, particularly in children.
• Understanding infection's role in asthma pathogenesis is crucial for management.

Purpose of the Study:

• To explore the mechanisms by which bacterial and viral infections induce or worsen bronchial hyperreactivity (HRB) in asthma.
• To elucidate the role of respiratory viral infections in the natural history of asthma, especially in pediatric populations.
• To investigate the multi-factorial pathogenic mechanisms linking viral infections to HRB and asthma exacerbations.

Main Methods:

• Review of existing literature on infection-induced asthma exacerbations and bronchial hyperreactivity.
• Analysis of proposed specific and non-specific mechanisms of bacterial infection in causing HRB.
• Examination of viral pathogenic mechanisms, including cytopathic effects, inflammation, and immune responses.

Main Results:

• Bacterial infections can cause HRB via specific (e.g., hypersensitivity) and non-specific (e.g., inflammation, mediator release) pathways.
• Respiratory viral infections are key in pediatric asthma, inducing or amplifying HRB and causing transient small airway obstruction.
• Viral HRB mechanisms are multi-factorial, involving epithelial damage, inflammation, autonomic nervous system imbalance, and IgE-mediated immune responses.

Conclusions:

• Infections are a significant trigger for asthma exacerbations, with distinct mechanisms for bacterial and viral pathogens.
• Viral infections, particularly in early life, play a critical role in asthma development and progression by inducing persistent HRB.
• Effective asthma management requires addressing the complex interplay between infections, immune responses, and airway hyperreactivity.