Rudolf Valenta

Profilin: A Novel Pan-Allergen and Actin-Binding Protein in Plants

Using serum-IgE from a pollen-allergic patient we isolated a cDNA from a birch pollen expression library (Valenta et al., 1991a). The deduced amino acid sequence of this cDNA clone showed significant homology with sequences from other eukaryotic profilins. Profilins function as actin-binding proteins (Isenberg et al., 1980) and interact with phosphatidylinositol 4,5 bisphosphate (PIP2) (Goldschmidt-Clermont et al., 1990). In addition a role of profilins in the signal transduction cascade via CAP was proposed (Vojtek et al., 1991). These data indicate that profilins are essential components of eukaryotic cells. This chapter concerning the biological functions of plant profilins illustrates that these proteins are ubiquitously distributed in plants and are structurally similar. For this reason plant profilins can function as targets for cross-reactive IgE antibodies of allergic patients and represent a novel class of pan-allergens.

Expression of a Human IgG4 Antibody, BAB2, with Specificity for the Major Birch Pollen Allergen, Bet v 1 in Escherichia coli: Recombinant BAB2 Fabs Enhance the Allergic Reaction

Background: Antigen recognition by antibodies of different isotypes can result in completely different effects as exemplified by Type I allergy. While the IgE–antibody–mediated release of biological mediators constitutes the immunopathological basis for the immediate symptoms observed in allergic patients, allergen–specific IgG antibodies are thought to have protective effects. Methods: Cell lines secreting five human monoclonal IgG antibodies (BAB1–BAB5) with specificity for the major birch pollen allergen Bet v 1 were established from a birch–pollen–allergic patient who had received birch– pollen–specific immunotherapy. The influence of the Bet v 1–specific IgG antibodies on IgE binding to Bet v 1 was investigated. BAB2 was expressed in Escherichia coli as recombinant Fab, purified and tested for its ability to modulate Bet v 1–induced immediate–type skin reactions. Results: The BAB antibodies belonged to different IgG subclasses (BAB1: IgG1; BAB2, BAB3, BAB5: IgG4; and BAB4: IgG2) reflecting a tendency towards Th2. BAB1 represented the only antibody which strongly blocked IgE binding to Bet v 1, whereas BAB 3–BAB5 had little effect on IgE binding. Surprisingly, natural BAB2 antibodies as well as recombinant BAB2 Fabs strongly enhanced IgE binding to Bet v 1 and Bet v 1–induced immediate–type skin reactions and thus represent ‘enhancing antibodies’. Conclusion: The demonstration that anti–allergen IgG antibodies can also enhance IgE binding to a given allergen explains the unpredictability of specific immunotherapy as well as the controversy on the role of IgG in atopy.

VVX001: A promising novel hepatitis B vaccine candidate

C trachomatis is a bacterial agent that causes sexually transmitted infections worldwide. The regulatory functions of dendritic cells (DCs) play a major role in protective immunity against chlamydia infections. The mechanisms underlying this immunomodulation are not fully understood. The inflammasome adaptor protein, apoptosis-associated speck-like protein containing a CARD (ASC) regulates the direction of immunity against such bacterial infections. Here, we investigate whether ASC, the critical components of inflammasome activation, participate in regulation of DC activation and function and the possible mechanisms during chlamydia infection. We observed that following chlamydia stimulation, the maturation and antigen presenting task of ASC-/DCs were impaired compare to wild type DC (WT DC). Also, ASC deficiency induces a tolerogenic phenotype in chlamydia stimulated DCs, which may induce immune pathological response in infected host. We observed that following chlamydia stimulation of ASC/DCs prevented the chlamydia-induced increase in aerobic glycolysis, measured as extracellular acidification rates (ECARs) and had significantly reduced pyruvate production from the metabolism of glucose during glycolysis. To determine the effect of this reduction in pyruvate production in cellular respiration, we determined the morphology of the mitochondria. The results revealed that the mitochondria of infected ASC-/-DCs had their cristae disrupted compared to the normal narrow pleomorphic cristae found in un-stimulated WT, ASC-/and stimulated WT DCs. In conclusion, the results suggest that ASC deficiency interrupts DC function through reprogramming of DC metabolism starting from glycolysis to the electron transport chain which occurs within the mitochondria, which controls the actions and functions of DCs during chlamydia infection. The interface between ACS and metabolism in innate immunity is of great interest. It may be possible for small molecules to reprogram the metabolism of immune cells to enhance vaccine efficacy against infectious diseases and tumors.