LONG-TERM HIGH IMMUNE-RESPONSE TO DIPHTHERIA TOXOID IN RODENTS WITH DIPHTHERIA TOXOID CONJUGATED TO DEXTRAN AS A SINGLE CONTACT POINT DELIVERY SYSTEM

Cross-linked dextran beads were used as a carrier for-development of a 'single-contact' vaccine delivery system. Diphtheria toroid (DT) was covalently coupled to dextran beads (DEX-DT conjugate). The conjugate was immunoreactive with antibodies raised against native DT Immunizati on of mts with DEX-DT conjugate generated on average 24 times higher a ntibody titres against diphtheria toroid than immunization with the co nventional DT absorbed on alum. The immune response was sustained for 9 months, with gradual decline of antibody titres thereafter. Signific ant antibody titres were measurable in rats after 1 year of immunizati on. DEX-DT had neither acute nor long-term adverse effects on the heal th of animals, as evidenced by local reactions, general behaviour, foo d intake, body weight gain and survival compared with controls. (C) 19 97 Elsevier Science Ltd.