THE IMMUNOSTIMULATING COMPLEX (ISCOM) IS AN EFFICIENT MUCOSAL DELIVERY SYSTEM FOR RESPIRATORY SYNCYTIAL VIRUS (RSV) ENVELOPE ANTIGENS INDUCING HIGH LOCAL AND SYSTEMIC ANTIBODY-RESPONSES

ISCOM is an efficient mucosal delivery system for RSV ens elope protei ns as measured by antibody responses in respiratory tract secretions a nd in sera of mice following two intranasal (i.n.) administrations. In tranasally administered RSV ISCOMs induced high levels of IgA antibodi es both in the upper respiratory tract and in the lungs. In the lungs, a prominent and long-lasting IgA response was recorded, which still p ersisted 22 weeks after the second i.n. immunization when the experime nt ended. Subcutaneous (s.c.) immunization only induced low IgA titres in the upper respiratory tract and no measurable response to RSV was found in the lungs. Differences were also noticed in serum between the i.n. and s.c. modes of immunization. ISCOMs given intranasally induce d earlier, higher and longer lasting IgM and IgG1 serum anti-RSV antib ody responses than those induced by the s.c. mode of administration. A low serum IgE response was only detectable at 2 weeks after i.n. immu nization with ISCOMs and after s.c. immunization with an inactivated v irus, but no IgE response was detectable after s.c. injection of ISCOM s. The serum IEA response was more pronounced following s.c. injection of inactivated virus than after i.n. application of ISCOMs, and a cle ar-cut booster effect was obtained with a second immunization. Virtual ly no serum IgA response was detected after the s.c. administration of ISCOMs. In conclusion, the high immune responses induced by RSV ISCOM s in the respiratory tract and serum after i.n. administration indicat e prominent mucosal delivery and adjuvant properties of the ISCOMs, wa rranting further studies.