Development of Vaccines Against Nocardiosis in Fishes
Nocardiosis, one of the most systemic and devastating diseases, is currently emerging as an important disease of cultured marine and freshwater fishes. The causative agent of this disease is Nocardia seriolae, a Gram-positive acid-fast bacterium. An effec
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Introduction Nocardiosis is one of the most systemic and devastating disease which is currently affecting a wide range of fish species. It is caused by a Gram-positive, acid-fast bacterium, Nocardia seriolae, which is thought to progressively invade and multiply inside various types of fish host cells. Fish species such as Japanese flounder, sea bass, striped mullet, yellowtail, tiger fish, large yellow croaker, and snakehead are frequently affected by this pathogen in many Asian countries including Japan, Malaysia, Taiwan, Indonesia, and China [1–5]. Although N. seriolae infection often causes considerable economic loss for fish farms, there are no suitable prophylactic measures against this pathogen [6]. While routine and abundant use of antibiotics lead to increase in antibiotic resistance among the N. seriolae isolates and/or ineffective in controlling the nocardiosis [5, 7], the development of a successful vaccine would be greatly welcomed. Immunization/vaccination is an important disease management strategy and is used to protect human and animal worldwide and fish is no exception and its success depends upon the ability of antigen to ensure significant immune response that could best protect the host against that particular pathogen or disease. As N. seriolae infection causes substantial mortality and morbidity in fishes, an effective vaccine against this pathogen is necessary to control the disease. An understanding of the immune mechanisms in fishes would facilitate protective immunity. Though several attempts have been made to develop live attenuated and inactivated vaccine against Nocardia, most attempts either failed or marginally succeeded [8–12]. Detailed understanding of immune response triggered by the pathogen and/or its inactive form is therefore extremely important to adopt appropriate measures to protect the animals from nocardiosis.
Sunil Thomas (ed.), Vaccine Design: Methods and Protocols, Volume 2: Vaccines for Veterinary Diseases, Methods in Molecular Biology, vol. 1404, DOI 10.1007/978-1-4939-3389-1_13, © Springer Science+Business Media New York 2016
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Sukanta K. Nayak and Teruyuki Nakanishi
Recently, we have analyzed both cellular and humoral immune responses to study the nature of immunity which is crucial against nocardiosis. Itano et al. [12] suggest the use of a low virulence N. seriolae isolate as a potential vaccine (strain) and demonstrated protection following virulent challenge. Modified live vaccines often stimulate long lasting humoral and cellular immune responses [13]. Nayak et al. [14] demonstrated that various immune parameters in the live sublethal immunized, though not at significant level were higher as compared with inactivated form of N. seriolae. They have also observed detectable antibodies after 15 days post immunization but the level decreased with subsequent sampling which is contrary to the findings of Shimahara et al. [6] who had recorded significantly high antibody which persisted throughout the experiment in largemouth bass following primary immu
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