Role of the bovine immune system and genome in resistance to gastrointestinal nematodes

Abstract

Gastrointestinal nematode infections of cattle remain a constraint on the efficient raising of cattle on pasture throughout the world. Most of the common genera of parasites found in cattle stimulate an effective level of protective immunity in most animals within the herd after the animals have been on pasture for several months. In contrast, cattle remain susceptible to infection by Ostertagia for many months, and immunity that actually reduces the development of newly acquired larvae is usually not evident until the animals are more than 2 years old. This prolonged susceptibility to reinfection is a major reason that this parasite remains the most economically important GI nematode in temperate regions of the world. Although, animals remain susceptible to reinfection for a prolonged period of time, there are a number of manifestations of the immune response that result in an enhanced level of herd immunity. These include a delay in the development time of the parasites, an increase in the number of larvae that undergo an inhibition in development, morphological changes in the worms, stunting of newly acquired worms, and most importantly a reduction in the number of eggs produced by the female worms. The overall result of these manifestations of immunity is a reduction in parasite transmission within the cattle herd. The immune mechanisms responsible for these different types of functional immunity remain to be defined. In general, GI nematode infections in mammals elicit very strong Th2-like responses characterized by high levels of Interleukin 4 (IL4), high levels of IgG1 and IgE antibodies, and large numbers of mast cells. In cattle, the most extensively studied GI nematode, in regards to host immune responses, is Ostertagia ostertagi. In Ostertagia infections, antigens are presented to the host in the draining lymph nodes very soon after infection, and within the first 3-4 days of infection these cells have left the nodes, entered the peripheral circulation, and have homed to tissues immediately surrounding the parasite where they become established. The immune response seen in the abomasum is in many ways are similar to that seen other mammalian hosts, with high levels of expression of IL4 in the draining lymph nodes and in lymphocytes isolated from the mucosa. But unlike a number of other systems, lymphocyte populations taken from Ostertagia infected cattle seem to be up-regulated for a number of other cytokines, most notably Interferon (IFN, implying that in Ostertagia infections, the immune response elicit is not simply a stereotypic Th2 response. In addition, effector cell populations in the tissues surrounding the parasites, are not typical, inferring the Ostertagia has evolved means to suppress or evade protective immune mechanisms. Studies have also demonstrated that the number of nematode eggs/gram (EPG) in feces of pastured cattle is strongly influenced by host genetics and that the heritability of this trait is approximately 0.30. In addition, EPG values are not "normally" distributed and a small...

Increased Expression of Interleukin-5 (IL-5), IL-13, and Tumor Necrosis Factor Alpha Genes in Intestinal Lymph Cells of Sheep Selected for Enhanced Resistance to Nematodes during Infection withTrichostrongylus colubriformis

“…Cytokine profiles associated with nematode resistance vary in detail depending on the particular hostparasite combination, but there is typically a dominant secretion of Th2 type cytokines (3,16,19,23,24,26,32,33,53). Similar tendencies toward Th2 cytokine responses have been observed in cattle (2,20,21) and sheep (22,39,43,48) although the polarization of the response has been less pronounced. In most of these studies, however, observations were made on cells taken from an animal at only one or a few time points and then cultured in vitro with specific stimuli, leaving uncertainties about how accurately they reflect the dynamic changes that occur over extended time periods in vivo.…”

Gene expression in the digestive tissues of ruminants and their relationships with feeding and digestive processes

“…Our laboratory has also evaluated gene expression in two recent studies in resistant v. susceptible beef cattle for GI nematode infection based on selection for low or high fecal egg count in response to Ostertagia and Cooperia challenge (Gasbarre et al, 2001). First, Araujo et al (2009) used an immune pathway-focused cDNA array to compare gene expression in mesenteric lymph node and small intestinal mucosa of the selected groups after an exposure to Ostertagia, Cooperia and Nematodirus spp.…”

Anthelmintic resistance in a dairy cattle farm in the State of Minas Gerais

“…The use of animals genetically resistant to intestinal nematodes is extremely important in areas where anthelmintic resistance is established (GASBARRE et al, 2001). As expected, animals gained more weight after the rainy months (October 2002to May 2003.…”

“…In June 2003, animals were about 18.4 months old, which is the age when cattle usually develop immune resistance to intestinal nematodes and are able to fight infection leading to lower egg production by females and thus lower EPG counts (GASBARRE et al, 2001;LIMA, 1998). The Pearson's correlation coefficient between EPG counts and age was 0.58, but only when the last 11 months of the experimental period was considered, which corresponds to 14.4 to 24.4 months of age and consequently to the main period of immunity development by the animals, when the correlation coefficient was very high (r = 0.93).…”