Characteristics of monoclonal antibodies to the lactate dehydrogenase-elevating virus.

Spleen cells, from BALB/c mice that had been infected with lactate dehydrogenase-elevating virus (LDV) for 6 days and that had or had not been previously immunized with glutaraldehyde-inactivated LDV, were fused with NS-1 myeloma cells. The fusion frequency was at least 10 times higher than with spleen cells of normal or chronically infected mice. Only 1 of 297 wells containing hybridomas prepared with spleens from unprimed 6-day-infected mice produced LDV-specific monoclonal antibodies (mAb). In contrast, when mice were immunized with inactivated LDV before infection, 33 of 73 hybridoma-containing wells screened were LDV-specific. The mAbs produced were mainly of IgG2a, IgM, and IgG1 subclasses and exhibited an identical characteristic staining pattern of LDV-infected cultured macrophages. A single mAb of IgG2b isotype yielded a different staining pattern. Western blotting showed that all of 12 mAbs analyzed in more detail were specific for the LDV glycoprotein, VP-3, but none of these neutralized the infectivity of the homologous strain of LDV. They also did not significantly protect immunosuppressed 10-month-old C58 mice against LDV-induced paralytic poliomyelitis, as does passive immunization with polyclonal mouse anti-LDV IgG.