Current status of immunological adjuvants.

Sixty years ago Ramon demonstrated that it was possible to augment the antitoxin response to diphtheria and tetanus by administering vaccines with pyogenic bacteria or with various additional compounds (1). Since that time, clinicians and immunologists have sought to potentiate the immune response with adjuvants while attempting to minimize the often present side effects. An explosion of information concerning the complexity and sophisti­ cation of immune regulation has occurred in the past decade. Coupled with presently available biosynthetic and recombinant DNA technology, this knowledge is permitting development of vaccines possessing antigenic epitopes that were previously impossible to produce. Current vaccine candidates, for example, include synthetic peptides mimicking streptococ­ cal (2), gonococcal (3), and malarial antigens (4). However, these purified antigens are generally weak immunogens that will require adjuvants to evoke protective immunity. Thus, a corresponding surge of interest has arisen in the development of potent nontoxic adjuvants that will enhance the immunogenicity of haptenic epitopes. An adjuvant may also be needed for conventional vaccines in order to elicit an earlier, more potent, or more