Synergistic interactions of anti-NS1 monoclonal antibodies protect passively immunized mice from lethal challenge with dengue 2 virus.

Non-neutralizing, serotype-specific anti-NS1 monoclonal antibodies partially protected passively immunized mice from lethal dengue 2 virus intracerebral challenge. There was no apparent correlation between complement-fixing activity and protective capacity among individual anti-NS1 monoclonal antibodies. Immunization with specific combinations of non-protective or partially protective antibodies resulted in prolonged survival or reduced mortality. Solid protection, equal to that achieved after immunization with neutralizing polyclonal antibody, was achieved only with an antibody pair which individually fixed complement to high titre with homologous virus. Some groups of mice had increased morbidity after immunization with combinations of protective monoclonal antibodies that bind to overlapping epitopes. These results may affect the design of recombinant dengue vaccines which may require the inclusion of serotype-specific antigenic domains.