Influence of Quillaja saponaria Triterpenoid Content on the Immunomodulatory Capacity of Epstein–Barr Virus Iscoms

Abstract

The immune responses to immunostimulating complexes (iscoms) containing recombinant Epstein-Barr virus (EBV) gp340 envelope protein was evaluated in BALB/c (H-2 d ) and CBA (H-2 k ) mice. Gp340-iscoms were used either with a low content of Quillaja triterpenoid adjuvant (L-iscoms) or supplemented with additional Quillaja adjuvant in the form of iscomatrix (S-iscoms). Class and subclass distribution of antigp340 antibodies, EBV-neutralizing antibodies, antigen-specific T cell proliferation and cytokine production were determined and these results compared to those obtained by immunization with non-adjuvated gp340. The H-2 d and H-2 k mice were characterized as low or high responders in respect to the level of specific antigp340 antibodies, secretion of IgG2a isotype, antigen-specific lymphoproliferative capacity, interferon-g (IFN-g) and interleukin-10 (IL-10) production in the basic immunizations with gp340. While presentation of the antigen in iscom formulations with low levels of Quillaja triterpenoids induces a moderate enhancement of the immune responses in the low responder H-2 d mice, supplementation with high levels of iscomatrix immunomodulator was required to enhance the immune responses in the high responder H-2 k mice. In both mouse strains subcutaneous immunization with S-iscoms resulted in a significant increase of IgG1-and IgG2a-specific antibodies, as well as in strong antigen-specific proliferative response confirmed by the simultaneous cytokine production. The enhanced antigen-specific secretion of IL-2 and IFN-g together with the abrogation of IL-10 and the absence of IL-4 indicates that the responses were driven towards a Th1-type rather than Th2-type immune response. The S-iscom formulations minimized the differences in immune responses between the two mouse strains, but the capacity of immune sera to neutralize EBV transformation in vitro remained completely strain-dependent. These data indicate that immune responses generated by iscoms can be manipulated by altering the triterpenoid composition of the iscoms and that the levels of triterpenoids can determine whether or not a Th1-type response is made.

Vaccine Design

“…In this system, the capacity to secrete IL-4 was similar for splenocytes from mice primed either with iscoms or with protein micelIes , whereas the IL-I0 response was clearly downregulated in mice primed with iscoms (Villacres-Eriksson, 1995) (Table 4). For recombinant EBV gp340 incorporated into iscoms, the IL-2 and IFNy responses were enhanced, IL-lO was downregulated and IL-4 was undetectable (Dotsika et al, 1997). It was shown in this study that the cytokine response correlated with the dose of Quillaja adjuvant used for immunization.…”

ISCOMs: an adjuvant with multiple functions

“…Production of IL-2 was first observed in a study by Fossum et al [86] and has been demonstrated after immunization with several antigens in ISCOMs, including influenza antigen [77,80,82,86,87], OVA [88,89], HSV type 1 glycoproteins [90], and EBV gp340 [91]. Immunization with ISCOMs containing these antigens [77,80,82,[87][88][89][90][91], or antigens from the parasites L. major [28,92,93] [76].…”

“…Immunization with OVA-ISCOMs or PSA-2-ISCOMs induced T cells producing significant amounts of IL-5 [28,88], whereas administration of antigens in ISCOMs has been reported to both increase [89,90,92] and decrease the production of IL-10 [77,91]. The results from several studies suggest that activation of IL-4-producing T cells by ISCOMs is low or absent, when assessed by measuring the cytokine secretion into cell culture supernatants after antigen stimulation in vitro [77,80,82,88,91,92]. However, when the ELISPOT technique was used to analyze T cell responses to PSA-2-ISCOMs, high numbers of cells secreting IL-4 were detected despite the fact that the corresponding culture supernatants only contained trace amounts of IL-4 [28].…”

“…Two observations of particular interest are the ability of ISCOMs to induce high levels of antibodies at lower doses of antigen than used with most adjuvants and the isotype pattern of such responses. Subcutaneous immunization of mice with influenzaISCOMs have been demonstrated to induce good antibody responses at antigen doses as low as 0.01 µg of influenza protein [14] and ISCOMs containing OVA, L. major PSA-2, EBV gp340, or HSV-1 antigen were highly immunogenic at doses ranging from 1 to 5 µg of protein [28,89,91,122]. It is not clear why such low amounts of these, and other antigens in ISCOMs, are able to induce potent antibody responses, but it is likely that the co-incorporation of adjuvant-active Quillaia saponins and antigen in the same ISCOM particle plays a crucial role, possibly by targeting antigen and adjuvant to the same APC.…”

Effectiveness of a cytolysin-enriched vaccine for protection of cattle against infectious bovine keratoconjunctivitis

“…The ISCOMs increase major histocompatibility complex class II expression on antigen presenting cells; increase the expression of interleukin-1, interleukin-6, and interleukin-12 39 ; and increase cellular, humoral, and local responses in immunized calves. [40][41][42][43][44] The method used in our study has been previously described for tachyzoite preparations of Toxoplasma gondii, 32,33 but unlike those investigations, our procedure did not result in the formation of ISCOMs. In our vaccine, neither phosphatidyl choline nor cholesterol was added exogenously.…”