2009 Annual Report
1a.Objectives (from AD-416)
This project proposes rodent models to provide molecular, genetic, and functional information to address the effects of nutrient requirements on mucosal immune responses to infectious pathogens, and pig models to provide physiologically relevant comparisons to human allergy and responses to probiotic bacteria. Common features are the use of targeted gene expression probes to elucidate innate and acquired immunity to both probiotic and pathogenic bacteria that activate Th1 responses, and allergies and worm infections that activate Th2 responses. The goal is to reveal interactions between dietary micronutrients and food components that modulate immune responses to food allergens, micro and macrobiotic organisms, and their products. Objective 1: To elucidate the role of vitamin A (VA) on the phenotype and function of alternatively activated macrophages and T regulatory cells, and identify macrophage-mediated modulation of localized nutrient delivery/partitioning in porcine models of allergy. Objective 2: To elucidate the mechanisms used by probiotic bacteria to improve respiratory and intestinal mucosal responses to allergens, and correlate intestinal microflora composition of pigs and humans with biomarkers of allergic and intestinal disease. Objective 3: To elucidate the mechanisms by which micronutrients affect gut physiology and immune competence in response to food-borne illness due to viruses, bacteria, and gastrointestinal parasites.
1b.Approach (from AD-416)
Studies will evaluate if pigs can be sensitized to peanut (PN) allergens by different routes of mucosal exposure without cholera toxin and orally challenge with over-the-counter unsalted dry-roasted PN; if Vitamin A (VA) via all-trans retinoic acid (ATRA) can exacerbate allergic disease via stimulation of Th2 dependent pathways at low doses of antigen; if alternatively activated macrophages (AAM) express retinal and retinol dehydrogenases leading to increased ATRA generation in vitro and in vivo; and if CD209 is a receptor for PN and parasite antigens that mediates functional polarization of AAM accompanied by generation of ATRA. Additional work will test if probiotic bacteria protect against allergy, and if changes in intestinal microflora in children affect the incidence of allergy and intestinal disorders such as chronic diarrhea. Finally, it will be determined if selenium (Se) deficiency impairs AAM function in a helminth-parasite infection model in mice, if chronic Se deficiency or genetic deficiencies in selenoprotein expression in immune cells or intestinal tissue alter immunity and pathology associated with Citrobacter rodentium; and if vitamin A status will alter gastrointestinal immunity to C. rodentium and Heligmosomoides polygyrus in mice.
Notice was received in April 2009 that this project was approved and thus was in place for about five months during FY2009. This is a collaborative research project conducted by five scientists that focuses on elaborating the role of dietary constituents in infectious and allergic disease. Both T regulatory cells and the alternatively activated macrophage are important cells regulating responses to allergic disease. The current project plan characterizes the role of these cells at the molecular, cellular, and whole animal level during response to peanut hypersensitivity and will provide information on local tissue changes at mucosal surfaces. It also focuses on treating sows with probiotics during the last trimester of pregnancy through weaning, and following their piglets from birth to emulate mother and child clinical studies in Finland not yet conducted in the U.S. This provides an opportunity to evaluate localized tissue and systemic clinical parameters in a peanut-induced allergy in pigs treated with probiotics as an immune modulating strategy to control allergic disease.
A third focus area evaluates the effect of micronutrient deficiencies on infection and immune response. When mice were fed selenium or vitamin E deficient diets and also infected with a mouse nematode, Heligmosomoides polygyrus, their ability to clear this secondary infection was decreased: both selenium and vitamin E caused delayed worm clearance and increased egg production. Selenium and vitamin E thus play important roles in the control of infection levels and intensity of the host mucosal response to both microbial and metazoan pathogens in the intestine. Study of alternatively activated macrophage function and the role of T regulatory cells using molecular and functional studies in the pig can be used for more definitive studies in the mouse. The availability of tissue specific selenoprotein knock-out mice will facilitate these objectives.