Effect of two feeding formulas on immune responses and mortality in mice challenged with Listeria monocytogenes

Cell-mediated immunity and natural killer cells play an important role against facultative intracellular organisms. The effect of two commercially available tube feeding formulas used for patients with acute or chronic debilitating and life-threatening illnesses was studied in mice challenged with Listeria monocytogenes. C57BL/6 X DBA/2 F1 hybrid mice were given ad libitum access to one of two formulas or to chow. Sixty mice in each of the feeding groups were challenged with 4.8 X 10(3) organisms intraperitoneally. Mortality was significantly less in animals fed Impact, a formula enriched with arginine, RNA and selected fatty acids. This was associated with reduced number of viable organisms in the spleen on day 7 after challenge. There was no difference in the spleen/body weight index between the different groups. Delayed cutaneous hypersensitivity was slightly higher in the Impact group but this was not statistically significant. Natural killer cell activity was significantly higher in the Impact group compared with the other two feeding regimens. These observations suggest that selective manipulation of the composition of tube feeding formulas may have a significant impact on immune responses and on morbidity and mortality following infectious challenge.