Variants of infectious hematopoietic necrosis virus selected with glycoprotein-specific monoclonal antibodies

Graduation date: 1988The development of an effective infectious\ud hematopoietic necrosis virus (IHNV) vaccine depends on a\ud better understanding of the antigenic structure and\ud variation among isolates. Three objectives to elucidate\ud this were: (1) to generate a panel of antigenic\ud derivatives of the IHNV glycoprotein by monoclonal\ud antibody-mediated selection of neutralization-resistant\ud variant viruses, (2) to determine if mutation in a\ud critical site for viral neutralization affects viral\ud virulence in vivo and characteristics in vitro, and (3) to\ud establish an antigenic relationship between the Round\ud Butte (RB) and 193-110 strains of IHNV.\ud A single anti-glycoprotein monoclonal antibody,\ud RB/B5, was used to select neutralization-resistant\ud variants of the RB and 193-110 strains of IHNV. The\ud virulence of the battery of IHNV variants was tested in\ud rainbow trout by waterborne challenge. Two of these\ud variants, RB-1 and 193-110-4. exhibited decreased\ud virulence for the host. Vaccination with RB-1 and 193-\ud 110-4 conferred protection to rainbow trout challenged\ud with wild-type virus. Interference did not appear to be\ud the mechanism for protection.\ud In vitro, variants RB-1 and 193-110-4 retained\ud several wild-type characteristics. Titers were normal.\ud differences among the structural proteins were not\ud detected. variants were not temperature-sensitive mutants.\ud and variants were neutralized by hyperimmune serum.\ud However, variant replication was slower than wild-type\ud virus at permissive temperatures and as a result viral\ud plaque size was smaller. Experiments with neutralizing\ud and nonneutralizing monoclonal antibodies indicated that\ud the RB and 193-110 strains have overlapping neutralization\ud epitopes and share conserved sequences at a similar region\ud on the IHNV glycoprotein