In vitro activation of antigen-presenting cells (APC) by defined composition of Quillaja saponaria Molina triterpenoids

Abstract

SUMMARYThe capacity of adjuvants to stimulate cytokine production by APC is important for the initiation of the immune response. Novel adjuvant formulations based on the iscom technology have been developed using selected triterpenoid components from Quillaja saponaria Molina. Five of these new Quillaja formulations were used to prepare matrix (an antigen-free particle) and tested for their capacity to stimulate IL-1 secretion by murine peritoneal cells in vitro. The formulation denominated QH 7.0.3 was superior to the other matrix formulations, including the original spikoside matrix. The QH 7.0.3 formulation in iscoms containing influenza virus envelope antigens induced IL-1 secretion more efficiently than the antigen-free matrix, or a mixture of matrix and viral antigens, or the free Quillaja components of similar composition. Compared with adjuvants known as IL-1 inducers, QH 7.0.3 fluiscoms were as efficient as the most prominent IL-1 inducer, i.e. lipopolysaccaride (LPS) and superior to cholera toxin (CT) and muramyl dipeptide (MDP). These results indicate that the composition per se of triterpenoids included in iscoms or matrix has a prominent influence on the level of APC activation which may result in qualitatively different immune responses in vivo.

ISCOMs: an adjuvant with multiple functions

“…ISCOMs containing purified Quillaia fractions also induce cytokine secretion in vitro. Influenza-ISCOMs prepared with ISCOPREP 703 stimulated peritoneal cells to produce IL-6 and induced levels of soluble IL-1 comparable to those obtained with E. coli lipopolysaccharide, a potent IL-1 inducer [74,75]. Immunization of mice with influenza-ISCOMs resulted in increased serum levels of IL-6 and IL-12 [75,76].…”

Quillaja Saponin Formulations that Stimulate Proinflammatory Cytokines Elicit a Potent Acquired Cell‐Mediated Immunity

“…In¯uenza virus micelles (in¯uenza-micelles) were prepared from the envelope proteins of in¯uenza A/PR/8/34 (H1N1) virus by the dialysis method, as described previously [8], and characterized by sedimentation through a sucrose gradient as well as by electron microscopy, while their protein content was determined by amino acid analyses. Iscom-matrix was prepared as previously described [8,20] with semipuri®ed Quillaja saponin, i.e. Spikoside (Advet AB, Lulea Ê, Sweden), QH-A, QH-C or QH-7.0.3 (QH-A 70%, QH-B 0% and QH-C 30%) (Iscotec AB, Uppsala, Sweden).…”

“…QS7, QS17, QS18, QS21, QH-A and QH-C fractions [8,9,28,29]. QS-21 [28,29], QH-A and QH-C [8,9] are presently undergoing investigation as candidates for human vaccines. It is therefore essential to characterize the mode of action of these adjuvants.…”

“…Free QH-B was found to have comparatively high toxicity coupled with potent adjuvant activity, while free QH-C had considerably lower toxicity than QH-B while retaining potent adjuvant activity, as measured by the secondary total antibody response [7]. However, later studies showed that iscom-matrix with a higher QH-A/QH-C ratio stimulated antigen presenting cells (APC) to produce interleukin (IL)-1 and IL-6 [8,9] more ef®ciently than the QH-C iscom-matrix. In addition, the particulate forms of QH-A (iscom-matrix and iscom) are more potent inducers of proin¯ammatory cytokines than free QH-A [8,9].…”

“…However, later studies showed that iscom-matrix with a higher QH-A/QH-C ratio stimulated antigen presenting cells (APC) to produce interleukin (IL)-1 and IL-6 [8,9] more ef®ciently than the QH-C iscom-matrix. In addition, the particulate forms of QH-A (iscom-matrix and iscom) are more potent inducers of proin¯ammatory cytokines than free QH-A [8,9]. The activation of APC to produce proin¯ammatory cytokines, such as IL-1 and IL-6, is pivotal for the stimulation of B-and T-cell responses [10±14].…”