Development of an oral vaccine for immunisation of rainbow trout (Oncorhynchus mykiss) against viral haemorrhagic septicaemia.
In the European Union Viral Haemorrhagic Septicaemia (VHS) eradication is still based on stamping out. Due to the lack of effective low cost vaccines immune prophylaxis is currently not used to combat VHS. This paper describes a new oral delivery method for immunisation of trout with attenuated virus. The vaccine consists of lyophilised virus surrounded by polyethylene glycol (PEG) and was extruded under low temperature. In the stomach of trout, the use of additional neutralising and adsorbing bases resulted in a neutral pH around the vaccine pellets, thus protecting the antigen against gastric acid. The in vivo efficacy of this delivery method was examined in three animal challenge experiments using an attenuated VHS virus (VHSV) strain as a vaccine. After vaccination, VHSV mRNA in gut, heart, kidney, spleen and blood was amplified by semi-nested PCR after RT-PCR. Indirect immune fluorescence test detected VHS vaccine virus in the gut. The expression of MHC class II, CD4 and CD8alpha mRNAs after oral vaccination was measured in gut using real-time RT-PCR. Antibody levels were measured by ELISA one week before vaccination and five weeks after vaccination. Animals were challenged six weeks after vaccination with highly virulent VHSV and mortality was recorded. The experiments showed that orally delivered vaccine virus was released from the vaccine preparation, penetrated the gut mucosa and led to higher expression levels of MHC class II and CD4 mRNAs when compared to control guts. VHSV antibodies were detected after oral vaccination. Immunisation with this new vaccine formulation was followed by a significant protection against VHSV. While the cumulative mortality in the non-vaccinated control group reached 70%, more than 75% of the orally vaccinated fish were protected upon challenge.
Adelmann
Malte
M
Friedrich-Loeffler-Institute, 17493 Greifswald-Insel Riems, Germany.
Köllner
Bernd
B
Bergmann
Sven M
SM
Fischer
Uwe
U
Lange
Bodo
B
Weitschies
Werner
W
Enzmann
Peter-Joachim
PJ
Fichtner
Dieter
D
D000284:Administration, Oral; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D000918:Antibody Specificity; D015704:CD4 Antigens / Q000235:genetics / Q000378:metabolism; D016827:CD8 Antigens / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005612:Freeze Drying; D041981:Gastrointestinal Tract / Q000276:immunology; D031941:Hemorrhagic Septicemia, Viral / Q000097:blood / Q000276:immunology* / Q000517:prevention & control*; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000378:metabolism; D029141:Novirhabdovirus / Q000276:immunology*; D017686:Oncorhynchus mykiss; D011092:Polyethylene Glycols; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014611:Vaccination / Q000662:veterinary*; D014765:Viral Vaccines / Q000008:administration & dosage*
D000914:Antibodies, Viral; D015704:CD4 Antigens; D016827:CD8 Antigens; C409469:CD8 antigen, alpha chain; D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D014765:Viral Vaccines; D011092:Polyethylene Glycols