Effect of short term supplementation with Lactobacillus acidophilus LAFTI® L10 on resistance to influenza infection in young and old mice.

Impairment of the immune function in the aged animals contributes to a decreased ability to clear pathogens when infection occurs. Probiotics have been shown to improve the immune response in animal models. We, therefore, determined the effect of 8 wks of dietary supplementation with Lactobacillus acidophilus (LBA) LAFTI® L10 on lung viral titer and selected peripheral immune responses in young and old C57BL mice infected with influenza virus. Young (2–4 mo) and old (20–22 mo) male C57BL mice were fed an AIN 93 diet supplemented with or without 1 x 109 per day of L10 for 8 wks. Animals were intra‐nasally infected with influenza virus and euthanized at 2, 5, 7 days post infection to determine viral titer and immune response. NK activity significantly increased while lymphocyte proliferation decreased following influenza infection. Young animals had significantly higher NK activity, and lymphocyte proliferation and lower lung viral titers compared to the old mice. LAFTI® L10 supplementation resulted in a significantly higher production of IFN‐gamma in the non‐infected old animals. There was no significant effect of LAFTI® L10 supplementation on viral titer, INF‐gamma, and NK activity in the infected mice. In conclusion, 8 wks of LAFTI® L10 supplementation increased INF‐gamma production in non‐infected old mice, but had no effect on influenza viral infection. Supported by DSM Nutritional Products, Inc. and USDA (Contract #58‐1950‐7‐707).