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The role of reactive oxygen and nitrogen intermediates in the immune response of rainbow trout to R.s. was investigated. The early events occurring when the pathogen interacted with trout macrophages were assessed in terms of the respiratory burst elicited. Live R.s. elicited a respiratory burst, which was enhanced by heat-killed microorganism. This phenomenon, though, was not observed using UV-killed bacteria. Both responses were enhanced when a combination of LPS and TNF was used to activate the macrophages prior to contact R.s. Further studies demonstrated that both compounds synergised to enhance superoxide (O2) production, and that this was correlated with the ability to kill the pathogen. Opsonisation of R.s. with serum factors also increased the respiratory burst, but no difference was found between normal serum and heat-inactivated serum. The role of NO in the immune response of rainbow trout is also studied. Though no evidence of NO production was found in vitro, i.p. injection of live R.s. produced higher NO levels in serum as compared to controls. Fish injected with a virulent strain showed higher levels of NO than controls and than fish injected with an avirulent strain and other strains of unknown virulence. Fish vaccinated with killed R.s. and FIA also showed a significant increase in NO levels, but only four days after vaccination, decreasing thereafter, at both doses of vaccine tested. Injected of Brivax II, an attenuated strain of Aeromonas salmonicida, did not produce a significant increase of NO. RT-PCR was used to detect the expression of the iNOS in different tissues of rainbow trout. iNOS expression was seen only in gill and kidney after i.p. injection. iNOS was detected in the gills 6 h after injecting live R.s. and the expression was still present at day 5. iNOS was detected in the kidney 24 h after injection but was switched off at day 3. After bath challenge with the bacterium, iNOS was expressed in gill, gut and kidney, but the expression varied in each fish. No iNOS expression was found in macrophages isolated from challenged fish.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 158-169).

Renibacterium salmoninarum, the etiological agent of bacterial kidney disease (BKD) of salmonid fish, is a pathogen of great concern among fisheries and the aquaculture industry worldwide. Previous investigations have indicated the pathogenesis of BKD is complex. It is a chronic, multisystemic, granulomatous disease with a number of potential immunomodulatory effects on the host. Given the current limitations for treatment and control of BKD, it is imperative that the pursuit of development of methods of prevention, namely management strategies and vaccination, be continued. To do so, the immunology of BKD must be elucidated in order to better understand and manipulate the associated immune responses to our advantage. This dissertation is composed of four chapters which relate to BKD and the associated immune responses of three species of susceptible salmonid fish as follows: Exogenous stress factors, through stress-induced immunosuppression, have been shown to influence BKD development in cultured salmonids. Chapter 1 examines the effects of two environmental stressors common to fish culture, overcrowding and overfeeding, as they affect BKD development and R. salmoninarumantigen prevalence among juvenile chinook salmon (Oncorhynchus tshawytscha) Immunomodulatory interaction between pathogen and host in BKD is widely reported and merits further investigation. Particularly, the immunological parameters affected and the role of the extracellular protein (ECP) of R. salmoninarum are of interest. Chapter 2 examines the in vivo immune response of rainbow trout (Oncorhynchus mykiss) following exposure to the ECP in terms of both humoral and cell-mediated immunological parameters, including the immune response against another bacterial pathogen. Chapter 3 addresses the in vitro effects of the ECP upon specific splenic immunocyte functions, phagocytosis and respiratory burst activity, in brook trout (Salvelinus fontinalis). The immune-complex mediated hypersensitivity reported to occur with BKD has considerable ramifications for control measures involving immunostimulation via antigen exposure. Further investigation is warranted to discern the significance and consistency of immunological hypersensivity in BKD pathogenesis. Chapter 4 examines the renal lesions, including immunopathologic changes and indications of immune-mediated disease, of brook trout exposed to R. salmoninarum. / Ph. D.

Thesis (Ph. D.)--University of Washington, 1986. / Vita. Bibliography: leaves [173]-183.