Dugbe virus susceptibility to neutralization by monoclonal antibodies as a marker of virulence in mice

A panel of monoclonal antibodies (MAb), reactive with the nairovirus Dugbe, was prepared and characterized. When used to compare seven strains of Dugbe virus by indirect immunofluorescence, they were antigenically indistinguishable. On the basis of in vitro plaque reduction neutralization and in vivo mouse protection tests by passive immunization, these strains could be divided into two groups. Five of the seven strains were neutralized by most or all of the neutralizing MAb and mice were protected from lethal infection by these viruses in the presence of passively administered MAb. The other two strains were not neutralized by most of the MAb and most of the MAb failed to protect mice from lethal infection by them. The binding capacity of the antibodies with these viruses in ELISA tests showed no correlation with their neutralization or protective capacity, therefore differences in avidity of antibody binding did not account for the differences in neutralization or protection. On the other hand, there was a direct relationship between neurovirulence of these strains for mice and their readiness to be neutralized or protected.