Antibody response to dengue-2 vaccine measured by two different radioimmunoassay methods

Abstract

Two different radioimmunoassays were used to detect virus-specific antibodies in series from human volunteers inoculated with an attenuated dengue type 2 (DEN-2) vaccine (PR-159/S-1). An indirect radioimmunoassay required purified DEN-2 virions for optimal reactivity but was 10-500 times more sensitive than neutralization or hemagglutination inhibition tests. An antibody capture radioimmunoassay utilized crude antigens from DEN-infected mouse brains or Aedes albopictus cell culture supernatants. When the 2 radioimmunoassay techniques were compared, the indirect method appeared to the best assay for IgG; the antibody capture method was more sensitive for IgM detection. Selected human sera were examined for IgG, IgM and IgA responses by using both techniques at various intervals after immunization. Although there were differences in magnitude, yellow fever immune and flavivirus nonimmune volunteers responded to DEN-2 vaccination by demonstrating IgG, IgM and IgA antibody responses. In the nonimmune group,the predominant post-DEN-2 vaccine Ig was IgG. The preponderance of DEN-2-specific neutralizing antibodies were associated with IgM or IgG according to the immune status of the volunteer. All classes of Ig attained maximum levels 21-60 days postvaccination. In the majority of volunteers, IgM responses were relatively transient and could not be detected 6 mo. after immunization; IgG and IgA antibodies were still detectable after this period.