Immunology & Infectious Diseases
Non Technical Summary
We recently determined that several common plant-derived products with anecdotal health benefits stimulate cells that function early in protection from disease, or in innate immunity. We sought products that specifically stimulated gamma delta T cells, which are an enigmatic cell with innate immune properties. Unlike in humans and rodents, gamma delta T cells are predominant cells in cattle and likely serve important roles in disease protection, particularly in very young animals. We identified one dietary supplement called Yamoa that contained bioactive components comprised of complex polysaccharides (carbohydrates) that stimulate aspects of innate immune function and, potentially, protect from Salmonella enterica serotype Typhimurium (ST) infection, a common cause of intestinal disease, in mice and cattle. Thus, Yamoa and similar dietary supplements have potential to be effective for disease amelioration, but their modes of action and appropriate application in veterinary medicine are unknown. The experiments in this proposal are designed to begin to determine the utility of compounds derived from dietary supplements to enhance innate immunity in bovine calves. We hypothesize that ingestion of polysaccharides increases resistance of calves to ST infection. Given that enhancement of innate immunity could potentially protect against a wide range of agents that cause disease, identification of new methods to enhance immunity are critical to animal protection and biosecurity. Characterization of compounds derived from dietary supplements (such as polysaccharides) may lead to a formulation that could be combined with standard mineral supplements and used to enhance the immunological health of newborn to six month old calves, shipped animals, and feedlot cattle.
Animal Health Component
Research Effort Categories
Goals / Objectives
We recently determined that several common plant-derived products with anecdotal immune benefits stimulate innate immunity by affecting the innate lymphocytes, gamma delta T cells. Yamoa (ground bark of Funtumia elastica tree) has distinct priming effects, very similar to that of lipopolysaccharide (LPS), on bovine, mouse and human gamma delta T cells. Unlike in humans and rodents, gamma delta T cells are a major subset in cattle and likely serve important roles in the innate immunity, particularly in neonates. Gene expression patterns in bovine cells induced by Yamoa are very similar to those induced by LPS, but the agonists in Yamoa signal through a distinct pathway without toxic negative effects. The bioactive component of Yamoa is comprised of complex polysaccharides that stimulate human cells to produce innate cytokines, and in animal models induce rapid increases in circulating neutrophils, expansion of gamma delta T cells in the intestinal mucosa, and, potentially, protect from Salmonella enterica serotype Typhimurium (ST) infection in bovine calves and mice. Yamoa has potential to be a potent innate immunostimulant, for which mechanisms and appropriate application in veterinary medicine are unknown. The experiments in this proposal are designed to begin to determine the utility of polysaccharides derived from Yamoa to enhance innate immunity in bovine calves. We hypothesize that ingestion of polysaccharides in Yamoa increase innate resistance of calves to ST infection. Given that enhancement of innate immunity could potentially protect against a wide range of pathogens, identification of novel innate adjuvants are critical to animal protection and biosecurity. Characterization of immunostimulatory polysaccharides in Yamoa may lead to a formulation that could be combined with standard mineral supplements and used to enhance the immunological health of newborn to six month old calves, shipped animals, and feedlot cattle. Three Specific Aims are proposed: Specific Aim 1. Optimize oral dose of Yamoa-derived polysaccharides (Yam-I). a. Identify the optimal oral dose of Yamoa-derived polysaccharides in calves. b. Monitor changes in peripheral blood leukocytes in response to the optimal oral dose. Specific Aim 2. Analyze in vivo target tissue response to the optimal oral dose of Yam-I. a. Determine effect of oral Yam-I on innate immune cells in mucosal derived lymphatic fluid. b. Determine effect of Yam-I on tissue cells at the target site. Specific Aim 3. Evaluate effect of orally delivered Yam-I in ST challenge in calves. a. Assess the capacity of prophylactic use of Yam-I to protect from ST challenge. b. Determine if Yam-I can be effective therapeutically after ST infection.
We propose to better characterize the action of Yamoa in an effort to stimulate the innate immune system for protection against a broad range of pathogens in bovine calves. We will confirm the in vivo effect of oral delivery of the polysaccharide fraction derived from Yamoa (Yam-I) by analysis of innate cell population changes and Salmonella challenge experiments. We will first determine the optimal oral dose of Yam-I. Calves will be given various doses of Yam-I daily and markers of innate immune activation will be measured following standard flow cytometry protocols, and temperatures will be taken daily. Sera will be collected and haptoglobin, an acute phase protein elevated in cattle as a result of infection, will be measured. In response to oral doses of Yam-I we expect to observe little change in temperature, similar to i.v. delivery of Yamoa, slight increases in serum haptoglobin, as was observed after CpG treatment in cattle and changes in other innate immune populations. An ideal treatment regimen is one that leads to the maximum innate immune stimulation in the absence of overt signs of toxicity. We expect to identify an optimal maximal, non-toxic dose of Yam-I for use in calves. We will then better characterize the specific action of Yam-I on lymphocyte subsets derived from target tissue and immunohistological analyses of changes in the tissue. Using our cannulation protocol that allows collection of mesenteric efferent lymphatic fluid, we will monitor changes in percentage, number, protein and gene expression in mucosal derived lymphocytes as we have previously described (Hedges et al. 2007). We will also investigate intestinal mucosal tissue sections from calves fed Yam-I and Yamoa using standard histochemical techniques. We expect that ingestion of Yam-I will mediate changes in gene and protein expression in cells in the gut mucosa detectable either in mesenteric derived lymphocytes found in lymphatic fluid or in the tissue directly. It is of interest to determine if oral delivery can result in protection from Salmonella infection, either by prophylactic or therapeutic use of Yam-I. To assess prophylactic Yam-I use, calves will be fed the optimal dose of Yam-I or vehicle, and closely monitored, then infected with a stock calf isolate of ST. Calves will be closely monitored and blood collected daily for flow cytometric and haptoglobin evaluation. Daily fecal samples will be tested for the input strain of ST and for other infectious agents. We will also assess therapeutic treatment of calves with the optimal does of Yam-I, providing it after infection. We expect to detect delayed or diminished fever responses and disease as measured by diarrhea and shed bacteria, and/or accelerated recovery in calves fed Yam-I, compared to those fed vehicle only.