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Type of publication: Doctoral Thesis
Type of document:

Year: 2008

Authors: Buggelsheim, M

Title: Interaktionen von Isospora suis mit dem Immunsystem des Schweins: Auswirkungen der Infektion auf die lokale Immunantwort im D√ľnndarm.

Source: Dissertation, Vet. Med. Univ. Wien, pp. 79.


Advisor(s):

Joachim Anja
Schmidt Peter


Abstract:
Isospora suis, the causative agent of neonatal coccidiosis, is a widespread pathogen in piglet production worldwide. Various aspects of this disease, including pathology and histopathology, epidemiology, and control, have been described previously. In contrast, the immunological reaction this parasite provokes in the host remains largely unclear. The objective of the present investigation was to characterise local leukocyte populations in the intestine involved in the immune reaction and to describe changes in their composition in relation to the infection with I. suis. The information gathered should help to develop a general idea of the local antigen-specific immune reactions in the intestine on a cellular level. Furthermore it was of interest how the metaphylactic use of the anticoccidial compound Toltrazuril affects the immune response. Twenty-four piglets were infected with I. suis on the third day of life, while 12 piglets had no contact with the pathogen and served as negative controls. On the fifth day of life half of the infected and half of the uninfected animals were treated with toltrazuril (20 mg/kg of body weight). Oocyst shedding of and the consistency of the faeces were documented continuously between the 7th and the 20th day of life, while body weight was controlled weekly. Animals were sacrificed between the 7th and the 42nd day of life to extract tissue samples of the jejunum and blood. Tissue samples were screened by immunohistochemistry for the presence of CD3-, CD79-, SWC3- and TcR-[gamma][delta]-positive cells using a Computer-Assisted Stereological Toolbox (C.A.S.T.) software. The collected blood was used to make a leukogram. CD3- and TcR-[gamma][delta]-positive cells could be detected in the Lamina propria as well as the Lamina epithelialis, while CD79- and SWC3-positive cells were exclusively found in the Lamina propria. The infection with I. suis mainly affected CD3- and TcR-[gamma][delta]-positive cells. An increase of these populations was found in infected animals in the Lamina epithelialis and the Lamina propria. The ratio of CD3- to TcR-[gamma][delta]-positive cells remained constant in the Lamina epithelialis of infected animals compared to not infected animals, while in the Lamina propria the number of CD3-positive cells was proportionally higher. Besides CD3- and TcR-[gamma][delta]-positive cells, a slight increase of SWC3-positive cells was detected in the Lamina epithelialis. No statistically significant increase could be detected for CD79-positive cells in the Lamina propria after infection. The use of the anticoccidial compound toltrazuril did not affect the composition of the leukocyte populations. This is true for infected as well as uninfected animals. Therefore it can be concluded that in cellular mechanisms are specifically involved in warding off I. suis. In this connection CD3-positive cells appear to play a major role, which seems to be especially true for the subpopulation of TcR-[gamma][delta]-positive cells. In the course of infection adaptive as well as innate components of the immune system are stimulated, though it is likely that the immune response is closely connected to adaptive mechanisms. The metaphylactic use of toltrazuril does not affect the investigated cell populations.

Keywords:
coccidiosis , swine , Isospora , immunology , lymphocytes , in situ hybridization , intestine , Lamina epithelialis , Lamina propria


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