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Infection and Immunity, August 2005, p. 5173-5182, Vol. 73, No. 8
0019-9567/05/$08.00+0 doi:10.1128/IAI.73.8.5173-5182.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Paul Wigley,2*
Pete Kaiser,2
Pietro Mastroeni,1
Heather Brooks,1
Claire Powers,2
Richard Beal,2
Paul Barrow,2
Duncan Maskell,1 and
Ian McConnell1
Centre for Veterinary Science, Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom,1 Institute for Animal Health, Compton, Berkshire RG20 7NN, United Kingdom2
Received 15 February 2005/ Returned for modification 14 March 2005/ Accepted 18 March 2005
Infection of poultry with Salmonella enterica serovar Typhimurium poses a significant risk to public health through contamination of meat from infected animals. Vaccination has been proposed to control infections in chickens. However, the vaccines are currently largely empirical, and our understanding of the mechanisms that underpin immune clearance and protection in avian salmonellosis is not complete. In this study we describe the cytokine, chemokine, and antibody responses and cellular changes in primary and secondary infections of chickens with Salmonella serovar Typhimurium. Infection of 1-week-old chickens induced early expression of a macrophage inflammatory protein (MIP) family chemokine in the spleen and liver, followed by increased expression of gamma interferon accompanied by increased numbers of both CD4+ and CD8+ T cells and the formation of granuloma-like follicular lesions. This response correlated with a Th1-mediated clearance of the systemic infection. Primary infection also induced specific immunoglobulin M (IgM), IgG, and IgA antibody responses. In contrast to previously published studies performed with newly hatched chicks, the expression levels of proinflammatory cytokines in the gastrointestinal tract were not greatly increased following infection. However, significant expression of the anti-inflammatory cytokine transforming growth factor ß4 was detected in the gut early in infection. Following secondary challenge, the birds were fully protected against systemic infection and showed a high level of protection against gastrointestinal colonization. Rapid expression of the MIP family chemokine and interleukin-6 was detected in the guts of these birds and was accompanied by an influx of lymphocytes. Increased levels of serum IgA-specific antibodies were also found following rechallenge. These findings suggest that cellular responses, particularly Th1 responses, play a crucial role in immune clearance in avian salmonellosis and that protection against rechallenge involves the rapid recruitment of cells to the gastrointestinal tract. Additionally, the high levels of inflammatory response found following Salmonella serovar Typhimurium infection of newly hatched chicks were not observed following infection of older birds (1 week old), in which the expression of regulatory cytokines appeared to limit inflammation.
Present address: Schering-Plough Animal Health, Herefield, Uxbridge, Middlesex UB9 6LS, United Kingdom.
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