| Summary: | The pathogenesis of <i>C. jejuni</i> in broiler chickens is still poorly understood despite the importance of poultry meat as a source of infection in humans. The overall objective of this project was to understand the role of flagella and Campylobacter invasion antigens in mucosal and systemic colonization, and to evaluate the vaccine potential of <i>C. jejuni</i> paralyzed flagella mutants. As a first step to track <i>C. jejuni in vivo</i>, a Green Fluorescent Protein (GFP) reporter system that is constitutively expressed was constructed. The system was transformed into different <i>C. jejuni</i> strains and isolates, and their mucosal and systemic spreading was studied over the period of 7 days. <i>C. jejuni</i> NCTC11168V1 and V26 share the same background but differ in their ability to colonize chickens. <i>C. jejuni</i> 81-176 and K2-55 share the same genetic background but K2-55 has an insertion mutation in <i>pflA</i> gene that produced paralyzed flagella. Although the K2-55 flagella remained intact structurally, it did not secret <i>Campylobacter</i> invasion antigens (Cia). The reporter system was stable in all of these strains both <i>in vitro</i> and <i>in vivo</i>. Fluorescent bacteria were visualized successfully using fluorescent and confocal microscopes. C. jejuni NCTC11168V1 and 81-176 were detected in the intestinal tract and in the liver and spleen of more than 30% of the challenged birds, while V26 and K2-55 were only detected in the intestinal tract. <i>C. jejuni</i> 81-176 and K2-55 did not spread systemically to the spleen and liver of BALB/c mice challenged using the same approach, although they colonized the ceca.<p>
A live attenuated vaccine based on <i>C. jejuni</i> K2-55 protected broiler chickens from <i>C. jejuni</i> 81-176 challenge in chickens following streptomycin treatment of drinking water. The same vaccine had no significant protection against a heterolgous <i>C. jejuni</i> NCTC11168V1 strain challenge. The vaccine was a poor stimulator of secretory IgA.<p>
Macrophage-like HD11 cells inflammatory response to the presence of <i>C. jejuni</i> K2-55 was not significantly different from their response to wild-type 81-176 when measured by qRT-PCR. The lack of Cia secretion and motility had no effect on expression of IL-1â, IL-2, IL-6, IL-8, IL, IL-10, IL-12â, or TLR5. A <i>flgK</i> mutant expressing the flagella up to the hook had a significantly lower expression of these genes.
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