Fish Oil Feeding Delays Influenza Virus Clearance and Impairs Production of Interferon-γ and Virus-Specific Immunoglobulin A in the Lungs of Mice

Abstract

Ingestion of fish oil can suppress the inflammatory response to injury and may impair host resistance to infection. To investigate the effect of a diet 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 fish oil or beef tallow for 14 d before intranasal challenge with live influenza virus. At d 1 and d 5 after infection, the mice fed fish oil had higher lung viral load and lower body weight (P < 0.05). In addition to the greater viral load and weight loss at d 5 after infection, the fish oil group consumed less food (P < 0.05) while the beef tallow group was clearing the virus, had regained their preinfection weights and was returning to their preinfection 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 relative 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.

Fish oil feeding enhances lymphocyte proliferation but impairs virus-specific T lymphocyte cytotoxicity in mice following challenge with influenza virus

“…The beef tallow diet contained 0´355 g/kg all-rac-a-tocopherol, while the ®sh oil diet contained 0´534 g/kg [12]. The fatty acid composition of the diets has been previously reported [12]. The mice were housed individually and fed 5 g food/ day.…”

“…Mice on experimental diets for 14 days were infected with log 10 5 plaque-forming units (PFU) of A/Queensland/6/72 (H3N2) in¯u-enza virus [12]. Lung macrophage, NK cell and virus-speci®c T cell cytotoxicity was determined at day 5 after infection.…”

“…Lymph node cells and spleen cells were isolated as previously described [12]. Cells (5´10 6 /ml) were suspended in RPMI 1640 medium supplemented with fetal calf serum (FCS; 100 ml/l), HEPES buffer 0´02 M, NaHCO 3 1´5 g/l, penicillin/streptomycin 50 mg/l, 2-mercaptoethanol (2-ME; 5´10 À5 M) and L-glutamine 1 mg/l (Trace Biosciences, Sydney, Australia).…”

“…The samples, suspended in methanol and toluene, were directly transesteri®ed by the addition of acetyl chloride (200 ml) while vortex mixing and then heated for 1 h at 1008C. The fatty acid composition was then determined by gas chromatography as previously described [12].…”

“…We have previously reported higher virus loads and delayed clearance following in¯uenza virus infection in naive mice fed a diet rich in ®sh oil [12]. The delayed virus clearance was associated with impaired lung immunoglobulin IgA antibody and interferongamma (IFN-g) responses.…”