Salmonella enterica infection affects a wide range of animals including humans. The avian specific serotype S. Pullorum infection produces systemic disease followed by a persistent carrier state in convalescence birds. Vaccination and other control strategies require an improved understanding of the immunity in response to S. Pullorum infection. This study compared the different immune dynamics following infection with (persistent) S. Pullorum and related (non-persistent) serovars S. Enteritidis and S. Gallinarum using co-culture of Salmonella-infected macrophages and CD4+ T lymphocytes in vitro and 2-day-old chickens in vivo. In comparison with S. Enteritidis, macrophages infected with S. Pullorum had a reduced gene expression of pro-inflammatory cytokines CXCLi2, IL-6, iNOS, IFN-γ, IL-12α and IL-18 and lower level of nitrite production. S. Pullorum-infected macrophages were found to be less effective than S. Enteritidis in stimulating the CD4+ lymphocytes to proliferate in vitro. CD4+ lymphocytes in co-culture with Salmonella-infected macrophages also produced lower levels of IFN-γ and IL-17F mRNA in response to S. Pullorum compared with S. Enteritidis. S. Pullorum infection in 2-day-old chickens stimulated proliferation of Th2-like lymphocytes with reduced IFN-γ and IL-17F but increased IL-4, IL-13 and IL-10 in the caecal tonsils and spleens when compared to S. Enteritidis. However, the modulation by S. Pullorum is not likely to be related to its large virulence plasmid, although the virulence plasmid of S. Gallinarum was shown to reduce nitrite production and gene expression of IL-1β and iNOS in infected HD11 cells. Our data showed no evidence of clonal anergy or immune suppression induced by S. Pullorum in vitro. The experimental work thus shows that the response to S. Pullorum infection was characterised by a modulation on host immunity from a dominant IFN-γ-producing Th17 response towards a Th2-like response which may promote persistent infection in chickens. This study provides insights into mechanisms by which S. Pullorum evades host immunity and produces the persistent carrier state. This opens the possibility for therapeutic application of cytokines to restore the host protective immune response to eliminate infection.

The detection and control of microorganisms such as bacteria is important in a wide range of industries and clinical settings. Detection, binding and removal of such pathogenic contaminants can be achieved through judicious consideration of the targets which are available at or in the bacterial cell. Polymers have the ability to present a number of binding ligands for cell targeting on one macromolecule and so avidity of interaction can be greatly increased. The goal of the project was to test whether polymers generated with bacteria in situ would have their composition significantly altered to determine if a templating process was occurring. It was also anticipated that the templated polymers would have better re-binding properties than those produced in the absence of bacteria. A series of chemical functionalities were analysed for their binding properties to bacteria. The functionalities were chosen with consideration to the cell surface characteristics. Further to identification of the most binding and least binding functionalities the polymers were tested for their cytotoxicity against bacteria and human epithelial cells. Concentration ranges were determined which could facilitate bacterial binding and templating yet minimise the lethality of the processes. Templated polymers of the bacteria were generated using a novel method of atom transfer radical polymerisation (ATRP) which we have termed bacterial activated atom transfer radical polymerisation (b-ATRP). This polymerisation method has maximised the potential for templating processes to occur during the polymerisation. Templated polymers differed in both their composition and their binding behaviour to non-templated polymers. The bacterial organic reduction process has also been demonstrated to have greater scope for use within the organic chemistry field as demonstrated by the use of this system to enable in "click-chemistry" via the reduction of copper.