Integrated genomic and proteomic characterisation of autotransporter proteins of obligate intracellular bacteria C. abortus and L. intracellularis

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Many infectious diseases affect livestock and impact not only on the health and welfare of animals but also on the economic sustainability of our agriculture industry. Among important animal pathogens are some bacteria that live within and are entirely dependent upon host cells. These so-called 'obligate intracellular' bacteria are very difficult to work with hence gaining understanding to aid in improving animal health is very problematic. Since this type of pathogen must infect a host animal to survive they typically develop mechanisms to very efficiently enter and take over host cells and evade the host's defences. Among the obligate intracellular bacteria, Chlamydophila abortus and Lawsonia intracellularis are very highly prevalent in sheep and pigs, respectively. Since such a high proportion of animals are affected, these infections have a considerable effect on animal health, quality of life and productivity. Although vaccines to these pathogens are available these have shortcomings so ultimately, we would like to develop efficient methods to very effectively reduce the effects of these diseases. Since these bacteria are difficult to work with, use of high-technology genomic methods can be very cost-effective and productive ways to improve the understanding of components with important roles in infection and make new developments in controlling disease. Genome sequences provide a wealth of information about pathogens and from this information we have identified a family of components - so-called Type V secretion proteins - which are likely to be involved in causing disease. Analysis of genomes is very informative however this is of greatest value when combined with an understanding of the function of the protein products of genes. We intend to study this family of proteins using computer-based approaches and laboratory methodologies to gain comprehension of these Type V proteins. These proteins are present on the surface of bacteria and, typically, are recognised by host defences and can result in the host activating defences that protect against infection. The ability to vary these proteins can be an important way to 'camouflage' pathogens allowing them to escape from host defences. Both C. abortus and L. intracellularis have many members of these Type V proteins thus we consider it is very likely that the members of this family present on the bacteria surface will vary. By gaining an understanding of how the presence of these proteins varies in each of these species we will be in a position to define the family members that are most important to infection and therefore lead to improved detection, treatment or prevention of these important livestock diseases.