ARS | Publication request: Brood stock immunization: does maternal transfer of specific antibodies protect rainbow trout alevins

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 11, 2010
Publication Date: April 7, 2010
Citation: Lapatra, S.E., Lafrentz, B.R., Cain, K.D. 2010. Brood stock immunization: does maternal transfer of specific antibodies protect rainbow trout alevins [abstract]. 2010 DAFINET Workshop: Vaccination of Early Life Stages of Fish. p.14-15.

Technical Abstract: Vaccination of young fish may be a possible means of reducing the occurrence of disease. However, mortality due to disease can occur at a life stage when vaccination is not possible either because the animal is not fully immunocompetent or an efficient delivery method of the vaccine is unavailable. Antibodies can be elicited and are detectable in adult rainbow trout (Oncorhynchus mykiss) against a variety of pathogens. Vaccination of broodstock could potentially enhance incorporation of specific antibodies into developing ova and may protect very young life stages of fish. One of the important functions of antibody in higher vertebrates is to provide immune protection to developing embryos. In mammals, immune antibody function is provided by the selective transfer of maternal antibody across the placental membrane. In birds, antibody is provided to the developing embryo within the yolk of the egg. Two studies were initiated to determine 1) if immunization of adult rainbow trout broodstock stimulates transfer of specific maternal antibodies to fry through the egg, 2) if these antibodies are detectable in laboratory assays, and 3) if an enhanced level of protection after pathogen challenge was observed in newly hatched fry obtained from vaccinated broodstock. Adult rainbow trout were tagged, bled, and immunized by intraperitoneal injection with a vaccine either against infectious hematopoietic necrosis virus (IHNV) or Flavobacterium psychrophilum, the etiological agent of bacterial coldwater disease (CWD) and rainbow trout fry syndrome (RTFS). Fish were booster vaccinated at 6 to 8 week intervals and monitored for the presence and titer of specific antibodies. Additional fish were mock immunized as controls. At spawning select crosses were made based on the antibody status of the adult fish. Fertilized eggs from each cross were incubated separately in specific-pathogen-free constant temperature spring water. Eggs and fry at different developmental stages were sampled for the presence of specific antibodies. Progeny from select crosses were challenged with a virulent strain of IHNV or F. psychrophilum at very early time points post-hatch. The results demonstrated elevated levels of antibody in the sera, eggs and sac-fry from vaccinated adults when compared to the mock immunized controls. Maternally transferred antibody appeared to decrease from the time of fertilization to baseline levels in very young post hatch sac-fry. Although specific antibody was shown to be maternally transferred to fry, this antibody did not result in protection from pathogen challenge. However, since there is evidence that some pathogens can be vertically transmitted, eliciting specific antibodies by vaccinating broodstock that enhances antibody transfer to eggs and sac-fry could reduce the potential of intra-ovum transfer of pathogens and manifestation of disease in very early and susceptible life stages of fish.