Research Report 2010 - MDC

Sebastian GüntherTechnical AssistantsSabrina KleißleJörg ContzenSecretariatSonja Gieringpyrogen’ as it acts as key-factor in igniting the immuneresponse. We have recently shown that Treg cells expresswith CD39 a surface ATPase, able to degrade extracellularATP to ADP and AMP. Studies in the animal model ofmultiple sclerosis (MS) as well as in human MS indicatethat CD39+ T REM cells play indeed a major role in controllingthe disease. CD39-/- mice are susceptible to EAEand MS patients have strikingly reduced numbers ofCD39+ Treg cells in the blood (Fig. 1). Thus the control ofextracellular ATP-levels by these cells seems tom be crucialin suppressing the autoimmune disease.Notably, the individual variations in the cell numberseem to have genetic causes. Recent studies inSingapore indicate that the CD39-Treg phenotype ismuch more frequent in the Asian population. Given itsapparent importance of this polymorphism for inflammatoryimmune responses a study has been launchedin Singapore to determine whether a ‘single nucleotidepolymorphism’ (SNP) can be identified that and can beused as a diagnostic indicator explains the underlyingmechanism.The impact of ‘MHC-loading enhancer’ (MLE) onthe immune responseCooperation with the BMBF network project‘MHCenhancer’ and the European MC-RTN ‘Drugs forTherapy’Class II MHC molecules are receptor molecule presentingantigens in the form of short peptides for the surveillanceby CD4+ T cells. Cell surface MHC moleculesthat have lost their ligand rapidly inactivate. Theyacquire a ‘non-receptive state’, presumably to preventthe ‘accidental’ exchange of peptide ligands on the cellsurface. While this safe guard mechanism minimizesthe uncontrolled loading of MHC molecules, it alsoinhibits the effective antigen-loading needed for peptidevaccinations. During the past years the group hadidentified a number of small molecular compoundstermed ‘MHC-loading enhancer’ (MLE) that can bypassthis safety mechanism. By acting directly on cell surfaceMHC molecules they can reconstitute the non-receptiveMHC molecule in a catalytic fashion.In cooperation with partners from the ‘Leibnitz Instituteof Molecular Pharmacology’ (FMP) and other membersof the ‘MHCenhancer’ network MLE were found to targeta defined pocket of the class II MHC molecule. Thetransient occupation of this pocket stabilizes the peptide-receptivestate in a similar way as the natural catalystHLA-DM. Several structural and computationalstudies have been carried out to describe the mechanismof this transition on the molecular level. Moreover,in vivo studies in experimental cancer models demonstratedthat the addition of MLE compound to the adjuvantgreatly improves the antigen-specific CD4+ T cellresponse. MLE compounds may therefore be usefulmolecular tools to amplify immune responses duringvaccination or therapy.Selected publications (2006 to present)Kleinewietfeld, M., Starke, M., Di Mitri, D., Borsellino, G., Battistini, L.,Rotzschke, O., and Falk, K. (2009). CD49d provides access to “untouched”human Foxp3+ Treg free of contaminating effector cells. Blood 113, 827-836.Gupta, S., Hopner, S., Rupp, B., Gunther, S., Dickhaut, K., Agarwal, N.,Cardoso, M. C., Kuhne, R., Wiesmuller, K. H., Jung, G., et al. (2008). Anchorside chains of short peptide fragments trigger ligand-exchange of class IIMHC molecules. PLoS ONE 3, e1814.Piaggio, E., Mars, L. T., Cassan, C., Cabarrocas, J., Hofstatter, M., Desbois, S.,Bergereau, E., Rotzschke, O., Falk, K., and Liblau, R. S. (2007). Multimerized Tcell epitopes protect from experimental autoimmune diabetes by inducingdominant tolerance. Proc Natl Acad Sci U S A 104, 9393-9398.Borsellino, G., Kleinewietfeld, M., Di Mitri, D., Sternjak, A., Diamantini, A.,Giometto, R., Hopner, S., Centonze, D., Bernardi, G., Dell’Acqua, M. L., et al.(2007). Expression of ectonucleotidase CD39 by Foxp3+ Treg cells: hydrolysisof extracellular ATP and immune suppression. Blood 110, 1225-1232.Hopner, S., Dickhaut, K., Hofstatter, M., Kramer, H., Ruckerl, D., Soderhall, J.A., Gupta, S., Marin-Esteban, V., Kuhne, R., Freund, C., et al. (2006). Smallorganic compounds enhance antigen loading of class II major histocompatibilitycomplex proteins by targeting the polymorphic P1 pocket. J BiolChem 281, 38535-38542.Patents (2005 to present)PCT/EP2005/010008 - „Änderung des Beladungszustands von MHCMolekülen“PCT/EP2008/008599 – “Method and kit for the rapid isolation of humanFoxp3+ Treg cells”PCT/EP2008/008660 - “Fusion protein comprising S-antigen repeatunits“Invention disclosure (07.05.2007): “Use of peptide derivates as MHCloading enhancers (MLE)”Cancer Research 135