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Salmonella enterica abortusovis is able during the infection to hide itself to the host immune system using unknown mechanisms

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Salmonella infection and innate immunity

Salmonella (S) are gram-negative bacteria that invade the intestine, stimulating the innate immune system and causing a massive intestinal inflammatory response called gastroenteritis. However, a few S species variants cause systemic infections that differ dramatically in their clinical presentation and do not cause inflammation.

Health

Abortion can occur in sheep due to infection from S enterica subspecies Abortusovis. This is an animal health problem that needs to be addressed, particularly in areas, where the sheep industry has a significant economic impact. This pathogen is able to evade detection by the host's innate immune system but the underlying evasive mechanisms are currently unknown. The long-term goal of EU-funded SALMONELLA project is to elucidate mechanisms involved in the pathogenesis of S. Abortusovis infection. Comparison between different S varieties suggests that persistence of S.Abortusovis can be based on circumvention of immune protective response. Translocation of bacteria from the intestinal lumen is detected by the immune system through pattern-recognition receptors, including so-called toll-like receptors (TLRs). These pattern-recognition receptors are able to recognise microbe-associated molecular patterns that distinguish bacteria from viral or parasitic agents. A comparison of the symptoms caused by S. Abortusovis and S. Typhimurium revealed striking differences. Intestinal inflammation and diarrhoea were absent from the intestine of animals infected with S. Abortusovis. However, S. Abortusovis was able to chronically persist at the sites of infection, resulting in abortion. Thus, the central hypothesis of the project was that direct contact of S. Abortusovis with the cell does not trigger an innate immune response to control infection. For the first time ever, the interaction between S. Abortusovis and TLRs was studied. Experiments with a cell line transfected with human TLRs show reduced production of inflammation factors in response to S. Abortusovis in contrast to S. Typhimurium. These results were confirmed using cells transfected with the ovine TLRs. This data will be used soon for eventual publication. The results of the SALMONELLA project provide an important mechanistic insight into how S. Abortusovis is able to modulate host responses and evade detection. This could lead to the development of novel pathogen detection and treatment options for such diseases with important implications for the sheep industry.

Keywords

Salmonella infection, inflammation, abortion, toll-like receptors, pathogen

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