Influence of immunoenhancement by dietary vitamin E supplementation on the development of Listeria monocytogenes infection in aged and young guinea pigs

L. monocytogenes is a facultative intracellular pathogen of humans and animals. Although L. monocytogenes is responsible for approximately 2500 cases of foodborne illnesses in the United States, it results in 88-92 % of hospitalizations attributed to foodborne pathogens and causes an associated high mortality rate of 25-40 %. Due to the natural decline of the immune system, infectious disease is one of the major causes of mortality in the elderly. Orthomolecular levels of vitamin E have been shown to promote T cell proliferation in healthy aged animals and human. We investigated the impact of immunomodulation on the development of listerial infection within an aged and young population after low dose challenge with L. monocytogenes. Animals were immunoenhanced with daily supplementation of vitamin E for a period of 21 days. An untreated control group was included. Blood samples were immunostained, and changes in the level of CD8+ and CD3+ T cells were determined using flow cytometry analysis. Animals were orally challenged with 100 CFU of L. monocytogenes . Daily supplementation with vitamin E increased the level of total (CD3+) T cells and cytotoxic (CD8+) T cells significantly in young but not old animals. Results showed that 8 % and 15 % of young and aged control animals respectively, became infected; whereas, 0 % and 13 % of young and aged animals, respectively, receiving orthomolecular doses of vitamin E became infected. During post-challenge period, vitamin E treated aged animals showed a faster CD8+ T cell proliferation response than control aged animals. Results also showed that dietary vitamin E supplementation boosted a pool of T cells. In conclusion, experiments demonstrate the effect of vitamin E in mitigating listerial infection in young animals; and stimulating immune response in young and aged animals.