Immunization of rainbow trout Oncorhynchus mykiss against Discocotyle sagittata (Monogenea)

Miguel Rubio-Godoy*, Jens Sigh, Kurt Buchmann, Richard C. Tinsley

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)

Abstract

Rainbow trout Oncorhynchus mykiss were injected intraperitoneally with 2 different Discocotyle sagittata extracts dissolved in PBS and subsequently exposed to controlled infection. Immunization resulted in significantly reduced (p < 0.0001) worm intensities in > 50% of vaccinated fish (response arbitrarily defined as parasite burdens < mean control intensity - 1 SD), irrespective of the immunization regime (different parasite extracts, dosing and application schedules) employed. The protective effect of worm extract applied in Freund's complete adjuvant (FCA) did not differ significantly from extract given in PBS. Vaccination with embryonated parasite eggs extract and with FCA alone did not result in partial immunity, suggesting the observed protective effect is specific. Immunized fish had significantly higher specific antibody titres at the time of dissection (as determined by ELISA) than both naive and control fish. Overall, a significant negative correlation was found between antibody titres and worm burdens, suggesting immunoglobulins are implicated in mediating partial immunity. Western blot tests indicated the 2 different worm extracts used to immunize fish share antigens, but each one primarily induced recognition of a distinct band (30 and 38 kDa). Immunization seems to promote a shift between 2 equilibria, rather than progressively increasing protection. This would explain why boosting did not increase immunity, and why 2 different extracts primarily inducing recognition of 2 distinct antigens provide similar degrees of protection. Although several other non-specific and cellular factors are likely to be involved in controlling parasite numbers, it cannot be excluded that antibodies could be involved in mediating the observed partial immunity.

Original languageEnglish
Pages (from-to)23-30
Number of pages8
JournalDiseases of Aquatic Organisms
Volume55
Issue number1
DOIs
Publication statusPublished - 20 Jun 2003

Keywords

  • Antibodies
  • Discocotyle sagittata
  • Immunization
  • Monogenea
  • Oncorhynchus mykiss
  • Trout

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