Differential regulation of human T cell cytokine patterns and IgE and IgG4 responses by conformational antigen variants

Abstract

Bee venom phospholipase A2 (PLA) represents the major allergen and antigen in allergic and non-allergic individuals sensitized to bee sting. We have studied specific activation of peripheral T cells by different structural and conformational variants of PLA and secretion of cytokines regulating IgE and IgG4 antibody (Ab) formation. PLA molecules expressing the correctly folded tertiary structure, which show high affinity to membrane phospholipids and were recognized by Ab from bee sting allergic patients, induced high IL-4, IL-5 and IL-13 production in peripheral blood mononuclear cell cultures. In contrast, non-refolded recombinant PLA (rPLA) and reduced and alkylated native PLA (nPLA) induced more IFN-gamma and IL-2 and higher proliferative responses. Differences in proliferation and cytokine patterns among correctly folded and non-refolded PLA resulted from conformation-dependent involvement of different antigen-presenting cell (APC) types. Antigen (Ag)-presenting B cells recognized PLA only in its natural conformation, stimulated Th2 type cytokines and induced IgE Ab. Non-refolded PLA was recognized, processed and presented exclusively by monocytes and induced a Th1 dominant cytokine profile leading to IgG4 production by B cells. The possibility that production of particular cytokine patterns and Ig isotype was influenced by the enzymatic activity of PLA was excluded by using enzymatically inactive H34Q point-mutated, refolded rPLA. These findings demonstrate the decisive role of specific Ag recognition by different APC, depending on structural features, membrane phospholipid binding property and the existence of conformational B cell epitopes, in the differential regulation of memory IgE and IgG4 Ab. Furthermore, they show that a change from IgE-mediated allergy to normal immunity against a major allergen can be induced by rPLA variants that are not recognized by specific Ab and B cells but still carry the T cell epitopes. These features may enable new applications for safer immunotherapy.

T Cell Epitope-Containing Hypoallergenic Recombinant Fragments of the Major Birch Pollen Allergen, Bet v 1, Induce Blocking Antibodies

“…The strong lymphoproliferative responses induced by the rBet v 1 fragments can be explained by the fact that both fragments together resemble the T cell epitope repertoire of complete rBet v 1 and the fact that they were engineered by selecting the breakpoint between the fragments outside known Bet v 1-specific T cell epitopes (26,44). Our finding that rBet v 1 fragments were potent inducers of T cell responses are in line with a previous study demonstrating that changes in antigenic conformation to a non-IgE binding structure increases the T cell stimulation capacity and induces higher proliferation and IFN-␥ production leading to decreased IL-4/IFN-␥ and IgE/IgG ratios (45).…”

Redirecting the Humoral Immune Response againstStreptococcus mutansAntigen P1 with Monoclonal Antibodies

“…Investigators have shown that presentation of particular antigen-specific T-cell determinants can be enhanced or suppressed as a direct consequence of antibody modulation of antigen processing (6,48,67,78), and changes in the specificity of T-cell epitopes modulate the fine specificity of an antibody response (42,49). In addition, Milch et al (52) and Akdis et al (1) have reported that conformational variants of antigens can result in differences in cytokine expression by helper T cells, a factor in determination of murine Ig isotype (1,72,79). We speculate that changes in the susceptibility of P1 to proteolysis as a result of binding of anti-P1 MAbs would result in a different spectrum of peptides that interact with the antigen-specific T-cell repertoire and influence the spectrum of antibodies elicited during a polyclonal response.…”

C8/119S Mutation of Major Mite Allergen Derf-2 Leads to Degenerate Secondary Structure and Molecular Polymerization and Induces Potent and Exclusive Th1 Cell Differentiation

“…For instance, it was reported that the denatured form of recombinant bee venom PlA 2 allergen, which failed to bind to the specific Ab, tended to favor the induction of Th 1 cells in vitro, and that the effect was attributed to the absence of B cell-mediated Ag presentation (29). Because B cells specific for the Ags are expected to have much higher affinity for the Ag than other APCs, the preferential generation of Th2 cells with limited concentrations of Derf-2 may be ascribed partly to the difference in the APC.…”