Carole L. Mintzer

Micronutrient status and immune function in tuberculosis.

Both macro- and micronutrients have been shown to affect resistance to tuberculosis, which is mediated by macrophages activated by T lymphocytes. Others have demonstrated inhibition of mycobacterial replication in macrophage cultures treated with vitamin D or retinoic acid. We examined the influence of dietary zinc and vitamin D on resistance to tuberculosis. Guinea pigs were fed diets containing varying levels of zinc or vitamin D, and infected 6 weeks later by the respiratory route with virulent Mycobacterium tuberculosis. Zinc-deficient guinea pigs had fewer circulating T cells and reduced tuberculin (PPD) hypersensitivity. The response of peritoneal exudate macrophages to the lymphokine MIF was impaired. Zinc deprivation did not influence disease resistance in BCG-vaccinated or nonvaccinated animals. Vitamin D deficiency adversely affected the tuberculin reaction and ability to control the infection. Lymphocytes from vitamin D-deprived animals did not proliferate normally when cultured with PPD. A diet supplemented with vitamin D enhanced T cell responses to PPD in vivo. These results suggest that zinc and vitamin D status affect immunity to tuberculosis.

The influence of dietary protein on the protective effect of BCG in guinea pigs

Specific pathogen-free, Hartley guinea pigs were vaccinated with viable Bacille Calmette-Guerin (BCG) and given isocaloric diets identical in every nutrient except protein (control = 30%; low protein = 10%). A non-vaccinated group was maintained on the control diet. Five weeks later, all animals were infected with an aerosol containing virulent M. tuberculosis H37Rv. On the same day, half of the protein-deficient guinea pigs were transferred to the control diet, while the remainder were maintained on the low protein (10%) diet. Animals from each diet treatment were tuberculin tested and sacrificed 1,2,3 and 4 weeks post-challenge. Protein-deficient guinea pigs exhibited diminished tuberculin reactions and loss of BCG-induced protection against virulent challenge as measured by the number of viable M. tuberculosis recovered from the lung and spleen. Renourished animals expressed normal levels of delayed hypersensitivity within 1 week of initiating the normal diet and were protected as well as vaccinated control guinea pigs against virulent respiratory challenge.

Differential effect of protein and zinc deficiencies on lymphokine activity in BCG-vaccinated guinea pigs

Abstract Pathogen-free guinea pigs maintained on isocaloric, purified low protein (LP), low zinc (LZ) and control (C) diets and commercial chow (Ch) were vaccinated with viable Mycobacterium bovis BCG and sacrificed 4, 5, and 6 weeks later. Both groups of malnourished animals showed weight loss and zinc-deficient guinea pigs had reduced plasma zinc levels. Serum proteins and albumin levels were reduced in LP guinea pigs. Animals on LP and LZ diets showed significantly impaired delayed hypersensitivity to dinitrochlorobenzene and tuberculin when compared to animals consuming the C and the CH regimen. The ability of peritoneal exudate cells to produce macrophage migration inhibition factor (MIF) when stimulated with PPD in vitro was diminished in animals maintained on the LZ diet for more than 5 weeks, but was unaffected by protein deficiency. Reduced capacity to produce functional lymphokines may contribute to skin test anergy in chronic zinc deficiency, but does not explain loss of delayed hypersensitivity in protein-deprived guinea pigs.

Effect of dietary protein and zinc on anti-mycobacterial antibody responses in guinea pigs

Abstract An enzyme immunoassay was developed to quantify the levels of antibodies reactive with purified protein derivative (PPD) at 3, 4, 5 and 6 wks following vaccination with Mycobacterium bovis BCG and initiation of diets deficient in either protein (LP) or zinc (LZ). Significant antibody levels were detected in all groups as early as 3 wks post-vaccination compared to non-vaccinated animals. Both LP and LZ guinea pigs had higher levels of antibody than animals consuming an adequate diet at 3 and 4 wks, respectively. By 6 wks post-vaccination, animals on the low protein diet had the highest antibody titers, followed by control, chow and LZ guinea pigs in order of decreasing titers. A highly significant positive correlation was detected between the levels of anti-mycobacterial antibodies and the number of viable BCG recovered from the lymph nodes draining the vaccination site. A significant inverse correlation was seen between antibody levels and PPD skin reactions. High-titer sera from protein-deficient, but not zinc-deficient, BCG-vaccinated pigs significantly suppressed the tuberculin reactions when passively transferred into normal, PPD-positive recipients.

Effect of diet on non-specific antimicrobial resistance in Mycobacterium bovis BCG-vaccinated guinea pigs

Abstract Specific pathogen-free guinea pigs were maintained on purifieddiets low in protein (LP-10% ovalbumin; 50 ppm Zn); low in zinc (LZ-30% ovalbumin; Mycobacterium bovis BCG. Four and five weeks post-vaccination and diet initiation, guinea pigs from each of the 6 diet × vaccination groups were challenged with 10 3 viable Listeria monocytogenes per animal by the respiratory route and sacrificed four days later. Low protein guinea pigs demonstrated weight loss and reduced serum albumin levels. Low zinc animals were growth-retarded and had reduced plasma Zn levels. Neither LZ nor LP guinea pigs developed significant tuberculin reactions post-vaccination at either sacrifice interval. Non-specific acquired resistance against L. monocytogenes was enhanced in LP and LZ animals at 4 wks post- M. bovis BCG vaccination but not at the 5 wk interval. The anti-listeria resistance was most pronounced in the liver and spleen. While M. bovis BCG-vaccinated LP and LZ guinea pigs were incapable of expressing tuberculin hypersensitivity, they did develop a significant non-specific anti-listeria resistance.

Influence of the timing of nutritional insult on alterations of cell-mediated immunity in guinea pigs infected with Mycobacterium bovis BCG by the respiratory route

Abstract Alterations of cell-mediated immunity in nutrient-deficient humans and animals are influenced by the severity and chronicity of the nutritional insult. Previously we have shown that initiation of deficient diets at the time of vaccination with Mycobacterium bovis BCG alters the immunologic status of guinea pigs several weeks later. In the present study, guinea pigs were infected by the respiratory route with M. bovis BCG simultaneously with, or two weeks or four weeks prior to placing groups on either low protein (LP), low zinc (LZ) or control (C) diets. Six weeks post-infection, all guinea pigs were skin tested with tuberculin and sacrificed. Splenocyte suspensions were stimulated in vitro with three doses each of two polyclonal T cell mitogens, phytohemagglutinin (PHA) and concanavalin A (Con A). Tuberculin reactions were completely suppressed in both LP and LZ groups maintained for the entire vaccination interval (6 weeks) and partially impaired in the protein-deficient animals after 4 weeks or 2 weeks on the LP diet. Reduced lymphoproliferative responses to both PHA and Con A were seen in acutely malnourished LP and LZ guinea pigs after 2 weeks on the diet. After 6 weeks on the deficient diets, lymphocytes from LZ animals were hyporesponsive to low concentrations of both mitogens.