Campylobacter jejuni is a gram-negative bacteria which is widely distributed in poultry, cattle and pigs. Chicken is a major reservoir harbouring high numbers of C. jejuni in their gut. The main route of transmission to humans is generally believed to be foodborne, via undercooked meat and meat products. C. jejuni is a commensal organism in chickens and colonises to very high numbers. Contamination of carcasses during processing is almost inevitable. A vaccine against C. jejuni in chickens is highly desirable, however, to date none have been developed. As C. jejuni avoids the chicken immune system, identifying the mechanisms by which it does is the first step in identifying suitable antigens for a vaccine.
An in-silico workflow was set up for the proteins of C. jejuni NCTC11168, integrating various tools which helped identify three putative secreted virulence proteins (Protein 1, 2 and 3) which could play a role in campylobacteriosis. The proteins identified were expressed, purified and analysed by in-vitro assays using Chicken Macrophage HD11 cells and the structure predicted using AlphaFold. A machine learning algorithm-based tool was also developed to determine which proteins may confer virulence and it has the highest accuracy in comparison with the current available tools.
Based on the structural and functional studies of the proteins, Protein 1 was found to possibly have a role in negatively impacting the cell wall biochemistry of C. jejuni. Protein 2 showed a significant reduction in the viability of the HD11 cells. Further research and animal trials will be required to confirm the significance of these two proteins as potential vaccine candidates. A vaccine would help to reduce the colonisation of C. jejuni in chickens, thus reducing level of transmission to people.