Fish oil feeding delays influenza virus clearance and impairs production of interferon-gamma and virus-specific immunoglobulin A in the lungs of mice

Ingestion of fish oil can suppress the inflammatory response to injury and may impair host resistance to infection. To investigate the effect of a die t containing fish oil on immunity to viral infection, 148 BALB/c mice were fed diets containing 3 g/100 g of sunflower oil with either 17 g/100 g of f ish oil or beef tallow for 14 d before intranasal challenge with live influ enza virus. At d 1 and d 5 after infection, the mice fed fish oil had highe r lung viral load and lower body weight (P < 0.05). In addition to the grea ter viral load and weight loss at d 5 after infection, the fish oil group c onsumed less food (P < 0.05) while the beef tallow group was clearing the v irus, had regained their preinfection weights and was returning to their pr einfection food consumption. The fish oil group had impaired production of lung interferon-gamma (IFN-gamma), serum immunoglobulin (Ig) G and lung IgA -specific antibodies (all P < 0.05) although lung IFN-alpha/beta and the re lative proportions of bronchial lymph node CD4+ and CD8+ T lymphocytes did not differ between groups after infection. The present study demonstrates a delay in virus clearance in mice fed fish oil associated with reduced IFN- gamma and antibody production and a greater weight loss and suppression of appetite following influenza virus infection. However, differences observed during the course of infection did not affect the ultimate outcome as both groups cleared the virus and returned to preinfection food consumption and body weight by d 7.