Abstract
Soluble complement-fixing (SCF) antigens were prepared to dengue viruses, types 1 to 4, from infected suckling mouse brain. While these non-structural proteins previously had been shown to have group- and type-specific antigenic determinants and to circulate in infected mice, their participation in human dengue infection was never established. Human acute and convalescent sera from primary and secondary dengue infections were tested for antibody to SCF antigens. At two antigen units, one of nine primary convalescent samples had antibody to a single type of dengue SCF, none of 11 secondary acute-phase sera had SCF antibody while all of 22 convalescent-phase samples had relatively high titers to two or more SCF antigens. With higher antigen concentrations, none of eight primary convalescent samples and only one of nine secondary acute-phase sera had antibody to dengue 2 SCF antigen. Sucrose gradient ultracentrifugation showed the antibody activity in the secondary convalescent-phase sera to be of the IgG class, suggesting prior antigenic exposure in these hosts. The inability to detect anti-SCF in the primary convalescent and secondary acute samples was not due to IgM interference as demonstrated with ethanethiol reduction experiments. This study has demonstrated that SCF antibody is produced in humans allowing for the possibility, as postulated, that these antigens participate in dengue immunopathogenesis. The inability to detect antibody during the acute phase of secondary dengue infections and in the convalescent sera from primarily infected humans requires further study.
