Live attenuated <i>Salmonella </i>that express heterologous antigens are attractive vehicles for the presentation of antigens for systemic and mucosal immunity. It is hypothesised that this requires uptake and interaction with DCs although this has yet to be studied in large animal models. This study has used pseudoafferent cannulated sheep to provide physiologically relevant DCs. However, in many other systems <i>in vitro</i> derived DCs are used in studies with <i>Salmonella</i>. Therefore we have cloned and expressed ovine IL-4 and developed protocols for derivation of <i>in vitro</i> generated DCs from comparison with this data. Cannulation of pseudoafferent and efferent lymphatics further allows monitoring of the earliest events of an <i>in vivo</i> <i>Salmonella</i> infection. Following <i>in vitro</i> infection with <i>S. abortus</i> <i>ovis</i> (a sheep specific <i>Salmonella </i>serotype) very few DCs were found to contain intracellular <i>Salmonella</i>. Avirulent <i>Salmonella</i> mutants were rapidly cleared from afferent lymph DCs <i>in vitro</i> unlike their virulent parental strains, which were found to survive and replicate intracellularly. Despite the rapid clearance of attenuated <i>S. abortus</i> <i>ovis</i> mutants from DCs, Maedi Visna virus (MVV) <i>gag</i> antigens expressed in these <i>Salmonella </i>were found to be presented to T cells. Following subcutaneous injection of <i>aroA<sup>-</sup></i> <i>S. abortus</i> <i>ovis</i> expressing MVV gag p25, <i>Salmonella</i> were found in the afferent lymph and cells draining the infection site. However, no bacteria were detected in the efferent lymph or cells. Phenotypic changes indicative of enhanced DC maturation in afferent lymph as well as lymphocyte activation in afferent and efferent lymph were also observed. Functional anti-<i>Salmonella</i> immune responses in efferent lymph were also studied. This study has established that <i>Salmonella </i>can infect afferent lymph dendritic cells of a large animal model. Such cells migrate to the lymph node where they initiate immune responses and can influence the cells' activation and the immune mechanisms invoked.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597422 |
| Date | January 2002 |
| Creators | Chan, S. S. M. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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