Respiratory syncytial virus replication is prolonged by a concomitant allergic response

Area of Science:

• Immunology
• Respiratory Medicine
• Virology

Background:

• Epidemiological studies suggest a link between early respiratory syncytial virus (RSV) exposure and asthma development or exacerbation.
• Mouse models show that allergen exposure worsens airway hyper-reactivity (AHR) in RSV-infected animals.

Purpose of the Study:

• To investigate the effect of allergen exposure on RSV disease pathogenesis.
• To explore the reciprocal interactions between allergic responses and RSV infection in a relevant animal model.

Main Methods:

• Cotton rats were sensitized to Aspergillus fumigatus (Af) allergen.
• Animals were infected with RSV before allergen challenge.
• Immune responses, viral load, and airway reactivity were assessed.
• Interferon-gamma (IFN-gamma) treatment was administered to evaluate its impact.

Main Results:

• RSV infection prior to allergen challenge exacerbated inflammation and airway responsiveness to methacholine.
• Allergic responses prolonged RSV persistence in the nasal passages by delaying viral clearance.
• Recombinant IFN-gamma treatment reduced allergic inflammation and cytokine mRNA but did not improve airway reactivity.
• Pathologic and physiologic measures of disease exacerbation were found to be independent.

Conclusions:

• Allergic responses can exacerbate RSV disease, characterized by increased inflammation and AHR.
• Allergic responses may impair viral clearance by downregulating Th1-type immune responses.
• The findings suggest a complex interplay where allergic responses influence viral immunity and vice versa.
• Understanding these interactions may offer insights into managing RSV-associated respiratory conditions.