Antibody and CD8+ T cell memory response to influenza A/PR/8/34 infection is reduced in treadmill-exercised mice, yet still protective.

Moderate exercise may decrease the severity of influenza infection and reduce lung viral load. The possibility that an exercise-associated reduction in lung viral load early in infection could contribute to decreased serum antibody and reduced memory response were investigated. BALB/c mice exercised for 8 wk and were then infected with influenza A/PR/8/34 (intranasal route). Influenza-specific serum antibody was assessed for 6 mo post primary infection, at which time mice were infected again with influenza A/PR/8/34. After primary infection, exercise reduced morbidity/mortality, attenuated lung cytokines, and decreased serum anti-influenza IgG and IgG2a from day 14 to day 180 post primary infection. After secondary infectious challenge, exercised mice did not show any signs of illness, but had reduced serum anti-influenza IgG and IgG2a, increased IgG1, and reduced influenza-specific recruited and resident CD8+ granzyme B+ T cells within the lungs. When influenza virus was administered by an intraperitoneal route during primary infection, exercise did not alter serum anti-influenza IgG, IgG1, or IgG2a, suggesting the exercise effect was specific to the lung environment. Exercise-induced enhancement of respiratory host defense to primary influenza infection results in decreased serum antibody and lung CD8+ T cell memory response, but does not compromise resistance to secondary infectious challenge.