Neutralizing-enhancing monoclonal antibody recognizes the denatured glycoprotein of viral haemorrhagic septicaemia virus.

Two monoclonal antibodies (MAbs), 1H10 and 1F10, have been selected against the denatured glycoprotein of the viral haemorrhagic septicaemia virus (VHSV) of salmonids by immunoblotting. Three reference VHSV serotypes (F1, F2, 23.75) and five VHSV isolates from either different host species (trout, salmon, barbel) or geographical locations in Spain reacted with both MAbs by ELISA. In vitro neutralization of all VHSV serotypes but not infectious haematopoietic necrosis virus (IHNV) was obtained only with MAb 1H10. However, when the MAb 1H10 (but not the non-neutralizing Mab 1F10) concentration was below 100 micrograms/ml rather than neutralizing VHSV infectivity, plaque counts increased 2-3-fold. MAb 1H10 is unique in that it has both, an in vitro enhancing infectivity effect (not described yet for VHSV) and it recognizes denatured G protein in contrast to other previously described neutralizing MAbs against VHSV.