title: Rainbow trout surviving infections of viral haemorrhagic septicemia virus (VHSV) show lasting antibodies to recombinant G protein fragments.
abstract: Rainbow trout antibodies (Abs) binding to recombinant fragments (frgs) derived from the protein G of the viral haemorrhagic septicemia virus (VHSV)-07.71 strain, could be detected by ELISA (frg-ELISA) in sera from trout surviving laboratory-controlled infections. Abs were detected not only by using sera from trout infected with the homologous VHSV isolate but also with the VHSV-DK-201433 heterologous isolate, which had 13 amino acid changes. Sera from healthy trout and/or from trout surviving infectious haematopoietic necrosis virus (IHNV) infection, were used to calculate cut-off absorbances to differentiate negative from positive sera. Specific anti-VHSV Abs could then be detected by using any of the following frgs: frg11 (56-110), frg15 (65-250), frg16 (252-450) or G21-465. While high correlations were found among the ELISA values obtained with the different frgs, no correlations between any frg-ELISA and complement-dependent 50% plaque neutralization test (PNT) titres could be demonstrated. Between 4 and 10 weeks after VHSV infection, more trout sera were detected as positives by using heterologous frg-ELISA rather than homologous PNT. Furthermore, the percentage of positive sera detected by frg11-ELISA increased with time after infection to reach 100%, while those detected by complement-dependent PNT decreased to 29.4%, thus confirming that the lack of neutralizing Abs does not mean the lack of any anti-VHSV Abs in survivor trout sera. Preliminary results with sera from field samples suggest that further refinements of the frg-ELISA could allow detection of anti-VHSV trout Abs in natural outbreaks caused by different heterologous VHSV isolates. The homologous frg-ELISA method could be useful to follow G immunization attempts during vaccine development and/or to best understand the fish Ab response during VHSV infections. The viral frgs approach might also be used with other fish species and/or viruses.
authors.affiliation: INIA, SGIT - Dept Biotecnología Crt, Coruña Km 7, 28040 Madrid, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Encinas
authors.forename: E
authors.initials: E
authors.lastname: Gomez-Casado
authors.lastname: Fregeneda-Grandes
authors.forename: N J
authors.initials: NJ
authors.lastname: Olesen
authors.forename: N
authors.initials: N
authors.lastname: Lorenzen
authors.forename: A
authors.initials: A
authors.lastname: Estepa
authors.forename: J M
authors.initials: JM
authors.lastname: Coll
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D005393:Fish Diseases / Q000276:immunology* / Q000401:mortality; D019204:GTP-Binding Proteins / Q000276:immunology*; D029141:Novirhabdovirus / Q000276:immunology*; D017686:Oncorhynchus mykiss / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology*; D018353:Rhabdoviridae Infections / Q000276:immunology / Q000401:mortality / Q000662:veterinary*
chemical_list: D000914:Antibodies, Viral; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins