Immunostimulation by bacterial components: I. Activation Of macrophages and enhancement of genetic immunization by the lipopeptide P3CSK4.

Synthetic lipopeptides derived from the N-terminus of bacterial lipoprotein constitute potent macrophage activators and polyclonal B-lymphocyte stimulators. They are also efficient immunoadjuvants in parenteral, oral and nasal immunization either in combination with or after covalent linkage to an antigen. Here we show how alterations in the molecular structure influence their biological properties indicating P3CSK4 as one of the most active members of a lipopentapeptide fatty acid library. This compound resulted in a most pronounced macrophage stimulation as indicated by NO release, activation of NFkappaB translocation, and enhancement of tyrosine protein phosphorylation. Furthermore, P3CSK4 activates/represses an array of at least 140 genes partly involved in signal transduction and regulation of the immune response. Finally we have evidence that P3CSK4 constitutes an effective adjuvant for DNA immunizations, especially increasing weak humoral immune responses. Our findings are of importance for further optimizing both conventional and genetic immunization, and for the development of novel synthetic vaccines.

Bacterial lipopeptides constitute efficient novel immunogens and adjuvants in parenteral and oral immunization.

Synthetic lipopeptide analogues derived from the N-terminus of bacterial lipoprotein constitute potent B-lymphocyte and macrophage/monocyte activators in vitro. In vivo they act as immunoadjuvants in parenteral and oral immunization when administered in combination with antigens. When added to bacterial or viral vaccines, lipopeptides markedly enhance the vaccine effect. After the coupling of lipopeptides to haptens or non immunogenic low molecular mass antigens, a specific antibody response is induced often after only one application of the conjugate. The response can be further enhanced by introducing haplotype specific T helper cell epitopes into the conjugate. Lipopeptide antigen conjugates can also be applied as synthetic vaccines that give protection e.g. against foot-and-mouth-disease. The novel chemically well defined lipopeptides described here can be synthesized in gram amounts with high purity and reproducibility; they are non-toxic and can be stored for long time even at room temperature. For veterinary application, by replacing Freund's adjuvant, side reactions and inflammatory processes are avoided.