Using genotype-to-phenotype analyses to identify the genetic determinants of gastroenteritis caused by the food-borne pathogen Campylobacter jejuni.

空肠弯曲杆菌是整个欧洲食源性胃肠炎的主要病原体。受污染的鸡肉是感染的主要来源，因此控制这种病原体对家禽业的食品安全至关重要。空肠梭菌的三个主要毒力决定因素是荚膜、低脂糖和鞭毛。这些结构对弯曲杆菌的生存和定植很重要。因此，逃避免疫系统是至关重要的，因为这些结构具有潜在的免疫显性表位，否则将导致空肠梭菌的早期识别和随后的清除。免疫逃避的一种机制是用各种糖分子（聚糖）修饰蛋白质结构。在空肠C.鞭毛蛋白上被TLR-5识别的保守表位已经丢失。失去这一抗原表位会使其他细菌，如沙门氏菌，失去活性。然而，通过TLR-5表位突变引入鞭毛的结构不稳定性已被鞭毛蛋白亚基外结构域的糖基化所补偿（Kreutzberger等人，2020）。这突出了聚糖在弯曲杆菌的生存和免疫逃避中所起的作用。此外，由于基因含量、等位基因变异和相变异的差异，这些聚糖在菌株之间变化很大。相变化是一种可逆机制，可导致与均聚束相关的偶发位点基因表达的ON/OFF开关。这导致不同的表型通过不同的基因表达，无论他们是开/关，什么组合被表达。在我们的实验室中，与重组FlaA蛋白相比，在糖基化FlaA蛋白攻毒的鸟类中观察到延迟的抗体反应。因此，我们的研究旨在进一步探讨引入表型变异的遗传因子对弯曲杆菌病和弯曲杆菌存活的贡献。

Campylobacter jejuni is the major causative agent of foodborne gastroenteritis across Europe. Contaminated chicken meat is the main source of infections and hence control of this pathogen is critical to food security in the poultry industry.The three major virulence determinants of C. jejuni are capsule, lipooligosaccharide and flagella. These structures are important for survival and colonisation of Campylobacter. Consequently, evasion of the immune system is paramount as these structures possess potential immunodominant epitopes that would otherwise result in early recognition of C. jejuni and its subsequent clearance.One mechanism of immune evasion is the decoration of protein structures with a variety of sugar molecules (glycans). A conserved epitope recognised by TLR-5 on the flagellin protein has been lost in C. jejuni. Loss of this epitope renders other bacteria, such as Salmonella, non-motile. However, the structural instability introduced into the flagella through mutations in the TLR-5 epitope has been compensated for by glycosylation of outer domains of the flagellin subunits (Kreutzberger et al., 2020). This highlights the degree to which glycans can play in the survival and immune evasion of Campylobacter. Further, these glycans are highly variable between strains due to differences in gene content, allelic variation and phase variation. Phase variation is a reversible mechanism that leads to ON/OFF switching of gene expression for contingency loci associated with homopolymeric tracts. This leads to different phenotypes through varied expression of genes, whether they are ON/OFF, and what combination is expressed. In our lab, it was shown that a delayed antibody response was observed in birds challenged with glycosylated FlaA when compared to recombinant FlaA protein. Therefore, our research aims to further investigate the contribution of genetic elements that introduce phenotypic variation towards Campylobacteriosis and the survival of Campylobacter.