title: Selective blockade of CD28 and not CTLA-4 with a single-chain Fv-alpha1-antitrypsin fusion antibody.
abstract: B7-1 and B7-2 are costimulatory molecules expressed on antigen-presenting cells. The CD28/B7 costimulation pathway is critical for T-cell activation, proliferation, and Th polarization. Blocking both cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and CD28 interactions with a CTLA-4/Ig fusion protein inhibits various immune-mediated processes in vivo, such as allograft rejection and autoimmunity. However, selective blockade of CD28 may represent a better strategy for immunosuppression than B7 blockade, because CTLA-4/B7 interactions have been shown to participate in the extinction of the T-cell receptor-mediated activation signal and to be required for the induction of immunologic tolerance. In addition, selective CD28 inhibition specifically decreases the activation of alloreactive and autoreactive T cells, but not the activation of T cells stimulated by exogenous antigens presented in the context of self major histocompatibility complex (MHC) molecules. CD28 blockade cannot be obtained with anti-CD28 dimeric antibodies, which cluster their target and promote T-cell costimulation, whereas monovalent Fab fragments can block CD28 and reduce alloreactivity. In this study, we report the construction of a monovalent single-chain Fv antibody fragment from a high-affinity antihuman CD28 antibody (CD28.3) that blocked adhesion of T cells to cells expressing the CD28 receptor CD80. Genetic fusion with the long-lived serum protein alpha1-antitrypsin led to an extended half-life without altering its binding characteristics. The anti-CD28 fusion molecule showed biologic activity as an immuno-suppressant by inhibiting T-cell activation and proliferation in a mixed lymphocyte reaction.
authors.affiliation: Institut de Transplantation et de Recherche en Transplantation, INSERM U437, CHU Hotel Dieu, 30 Bld Jean Monnet, 44093 Nantes, France. bvanhove@nantes.inserm.fr
authors.forename: Bernard
authors.initials: B
authors.lastname: Vanhove
authors.forename: Geneviève
authors.initials: G
authors.lastname: Laflamme
authors.forename: Flora
authors.initials: F
authors.lastname: Coulon
authors.forename: Marie
authors.initials: M
authors.lastname: Mougin
authors.forename: Patricia
authors.initials: P
authors.lastname: Vusio
authors.forename: Fabienne
authors.initials: F
authors.lastname: Haspot
authors.forename: Jérôme
authors.initials: J
authors.lastname: Tiollier
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Soulillou
mesh_terms: D000069594:Abatacept; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000187:drug effects; D018122:B7-1 Antigen / Q000276:immunology* / Q000378:metabolism; D015374:Biosensing Techniques; D018106:CD28 Antigens / Q000187:drug effects* / Q000276:immunology; D019556:COS Cells; D060908:CTLA-4 Antigen; D002448:Cell Adhesion / Q000187:drug effects; D002522:Chlorocebus aethiops; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006207:Half-Life; D006801:Humans; D018796:Immunoconjugates / Q000276:immunology / Q000494:pharmacology; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007128:Immunoglobulin Fragments / Q000276:immunology*; D007152:Immunologic Capping; D019169:Jurkat Cells; D007739:L Cells; D007959:Lymphocyte Culture Test, Mixed; D008252:Macaca fascicularis; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000493:pharmacokinetics / Q000494:pharmacology; D013329:Structure-Activity Relationship; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D014162:Transfection; D020298:U937 Cells; D000515:alpha 1-Antitrypsin / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments; D011993:Recombinant Fusion Proteins; D000515:alpha 1-Antitrypsin; C055966:immunoglobulin Fv; D000069594:Abatacept