The iscom: an immunostimulating system.

To make purified antigens highly immunogenic, they have to be presented in several copies in the form of a microscopic or submicroscopic particle. This is the case, regardless of whether the antigens are obtained by isolation from conventional microorganisms, or from gene-manipulated cells, or synthesized. In the iscom, the antigens are attached as multimers to a 40-nm cage-like particle with a built-in adjuvant. The antigens in iscoms are rapidly transported from the injection site to the draining lymphatic organ. Iscom-borne antigens induced a 10-fold higher antibody response than the same amount of antigen in micelle form. One intranasal immunization with influenza virus iscoms induced protection to intranasal challenge infection in mice. Besides a strong antibody response in all Ig classes and isotypes, cytotoxic T cells were induced. With iscoms containing gp160 of HIV-1, cytotoxic T cells (CD8+ CD4-) were induced under restriction of class I MHC antigen. Iscoms containing the fusion protein of measles virus induced T cell clones in mice whereof one, after adoptive transfer, protected mice against intracerebral challenge infection. Protective immunity against Epstein-Barr virus (EBV)-induced tumor formation by iscoms containing gp350 of EBV has been elicited in cotton-top Tamerin monkeys. Protective immunity has also been induced against several virus infections including feline leukemia virus and against parasites, i.e., Trypanosoma cruzi, in mice.