published_or_final_version / abstract / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) have been shown to stimulate the innate immune system against a variety of bacterial, viral, and protozoan infections in a variety of vertebrate species. The objectives of this study were to investigate the immunostimulatory effect of CpG-ODN against Salmonella Typhimurium infection and the formulation and delivery of CpG-ODN by the in ovo route. Day-old broiler chicks or embryonated eggs (day 18th of incubation) received either 50 g of CpG-ODN, 50 g of non-CpG-ODN, or saline. At day four-post hatch, all birds were subcutaneously inoculated by Salmonella Typhimurium. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for ten days following challenge. The survival rate of the birds that received CpG-ODN via in ovo or in vivo treatments was significantly higher than the control group. Salmonella Typhimurium level in the peripheral blood and pathology were significantly lower (p < 0.001) in CpG-ODN group compared to the control group. In order to investigate the effect of formulation of CpG-ODN, embryonated eggs (day 18th of incubation) were inoculated with either 50 g of CpG-ODN alone or CpG-ODN formulated with polyphosphazene, liposome, or Emulsigen®. Four days after administration of CpG-ODN formulations, the birds were challenged with E. coli by subcutaneous injection. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for seven days following challenge. The birds that received either CpG-ODN or CpG-ODN formulated with polyphosphazene had significantly higher survival rates (30 and 60%) compared to the birds in groups receiving either non-CpG-ODN or saline. Bacterial loads in the air sacs were lower in groups treated with formulated CpG-ODN compared to the CpG-ODN alone or control groups. However, formulation of CpG-ODN with liposomes or Emulsigen® did not increase the immunoprotective effect against E. coli infection. We showed that treatment with CpG-ODN protects neonatal chickens against an intracellular bacterial infection and that co-treatment of CpG-ODN with polyphosphazene enhances the immunoprotective effect of CpG-ODN.

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) have been shown to stimulate the innate immune system against a variety of bacterial, viral, and protozoan infections in a variety of vertebrate species. The objectives of this study were to investigate the immunostimulatory effect of CpG-ODN against Salmonella Typhimurium infection and the formulation and delivery of CpG-ODN by the in ovo route. Day-old broiler chicks or embryonated eggs (day 18th of incubation) received either 50 g of CpG-ODN, 50 g of non-CpG-ODN, or saline. At day four-post hatch, all birds were subcutaneously inoculated by Salmonella Typhimurium. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for ten days following challenge. The survival rate of the birds that received CpG-ODN via in ovo or in vivo treatments was significantly higher than the control group. Salmonella Typhimurium level in the peripheral blood and pathology were significantly lower (p < 0.001) in CpG-ODN group compared to the control group. In order to investigate the effect of formulation of CpG-ODN, embryonated eggs (day 18th of incubation) were inoculated with either 50 g of CpG-ODN alone or CpG-ODN formulated with polyphosphazene, liposome, or Emulsigen®. Four days after administration of CpG-ODN formulations, the birds were challenged with E. coli by subcutaneous injection. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for seven days following challenge. The birds that received either CpG-ODN or CpG-ODN formulated with polyphosphazene had significantly higher survival rates (30 and 60%) compared to the birds in groups receiving either non-CpG-ODN or saline. Bacterial loads in the air sacs were lower in groups treated with formulated CpG-ODN compared to the CpG-ODN alone or control groups. However, formulation of CpG-ODN with liposomes or Emulsigen® did not increase the immunoprotective effect against E. coli infection. We showed that treatment with CpG-ODN protects neonatal chickens against an intracellular bacterial infection and that co-treatment of CpG-ODN with polyphosphazene enhances the immunoprotective effect of CpG-ODN.

Ph.d.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 114-127).

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Julia Babensee ; Committee Members: Barbara Boyan, John Brash, Andres Garcia, and Niren Murthy. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 114-127). Also available in print.

Thesis (Ph. D.)--Duke University, 2007. / Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

This study investigated the use of non-specific immunostimulants to alleviate stress-mediated suppression of defence mechanisms and subsequent susceptibility to bacterial pathogens in rainbow trout (Oncorhynchus mykiss). One yeast (1-3),)1-6)-β-glucan and a bacterial peptidoglycan were selected as immunostimulants from a panel of test substances on the basis of enhanced intracellular superoxide generation by kidney macrophages stimulated in vitro. Kidney macrophage effector activity was not affected after 1, 2, 3 or 4 weeks of in-feed treatment with 0.05% or 5% of glucan or peptidoglycan. However, production of bactericidal superoxide by inflammatory peritoneal macrophages did increase significantly after four weeks of oral treatment with 0.05% peptidoglycan. Although a single confinement of fish (93% reduction of water volume for five minutes) caused a physiological stress response, as indicated by hyperglycaemia in plasma, kidney and inflammatory macrophage activities were only affected after six daily confinements. Phagocytosis, intracellular superoxide production and killing of Aeromonas salmonicida in vitro by kidney macrophages were significantly reduced. Conversely, production of extracellular superoxide, which may be associated with damage to self, was enhanced. Peritoneal macrophages displayed a similar but less marked respiratory burst response after repeated confinement. Some of the alterations in macrophage function caused by daily confinement were prevented by feeding 0.05% peptidoglycan four weeks before the first confinement. The increase in kidney macrophage extracellular superoxide production caused by repeated confinement was significantly alleviated by in-feed peptidoglycan. Similarly, the decrease in intracellular production by peritoneal macrophages caused by repeated confinement was prevented by in-feed treatment with peptidoglycan. Neither peptidoglycan nor repetitive confinement had any effect on complement lytic activity. These results indicate that dietary peptidoglycan was able to reduce, by regulating macrophage function, the impact of stress on certain bactericidal defences and potential damage to self. However, there was no significant difference in the persistence of viable A. salmonicida in the spleen or blood of infected fish in any of the experimental treatments.