Interaction of protein and zinc malnutrition with the murine response to infection

Malnutrition increases the host's susceptibility to infection. However, the mechanisms are not well understood. This study examined the interaction of protein and zinc underfeeding in mice before challenge with an intracellular pathogen, Salmonella typhimurium. C3H/HeN mice (n = 68) were weighted and placed on one of four diets: 20% ovalbumin with adequate zinc (20% NL), 20% ovalbumin without zinc (20% LO), 1% ovalbumin with zinc (1% NL), and 1% ovalbumin without zinc (1% LO). At the end of 6 weeks they were again weighed and then challenged with 10(4) S. typhimurium intraperitoneally. Mortality was recorded over the next 2 weeks. Although weight loss was markedly affected by protein malnutrition (two-way analysis of variance: p = .0001), there was no independent effect by zinc (p = .3459). Similarly, protein malnutrition alone affected mortality rates (chi 2: p = .0001), whereas zinc had no independent effect (p = .7166). However, both protein and zinc underfeeding shortened the length of survival (Mann-Whitney U test: p less than .001). We conclude that protein malnutrition is the dominant factor influencing weight loss and mortality in this model. However, zinc malnutrition does shorten the length of survival and may contribute to the global immunosuppression noted in malnourished subjects.