DAO 37:121-126 (1999) - doi:10.3354/dao037121
The protective immune response of yellowtail Seriola quinqueradiata to the bacterial fish pathogen Lactococcus garvieae
Tsuyoshi Ooyama1, Akio Kera1, Toshiaki Okada2, Valerie Inglis3, Terutoyo Yoshida2,*
ABSTRACT: Yellowtail Seriola quinqueradiata were immunized with 2 different Lactococcus garvieae bacterin, formalin-killed KG- phenotype cells (capsulated phenotype) and formalin-killed KG+ phenotype cells (unencapsulated phenotype). These 2 injected vaccines conferred long-term protection to yellowtail against an artificial infection of an encapsulated Lactococcus garvieae strain with long-lasting agglutinating titres against KG+ phenotype cells. However, no agglutinating titres or low agglutinating titres against KG- phenotype cells were detected in fish given each of these bacterin. These results suggested that a capsule in KG- phenotype cells apparently affects their immunogenicity, but the antigens which conferred protection to fish against lactococcal infection may be located on the surface of KG+ phenotype cells, and are not cell capsules in KG- phenotype cells. The protection offered by a formalin-killed KG+ phenotype cell vaccine would not appear to be strain specific. Encapsulated L. garvieae cells were well phagocytosed, and fimbrie-like appendages were seen in KG- phenotype cells after treatment with yellowtail immune serum.
KEY WORDS: Vaccines · Lactococcus garvieae · Seriola quinqueradiata · Phenotypic variation · Immune response
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