Single domain antibodies from llama effectively and specifically block

KOCH- NOLTE, FRIEDERICH; REYELT, JAN; SCHÖßOW, BRITTA; SCHWARZ, NICOLE; SCHEUPLEIN, FELIX; ROTHENBURG, STEFAN; HAAG, FRIEDERICH; ALZOGARAY, VANINA; CAUERFF, ANA; GOLDBAUM, F.A.

The FASEB Journal

Federation of American Societies for Experimental Biology

Lugar: Bethesda, Maryland, EEUU; Año: 2007 vol. 21 p. 3490 - 3498

The purpose of our study was to develop a tool for blocking the function of a specificleukocyte ecto-enzyme in vivo. ART2.2 is a toxin-related ecto-enzyme that transfers the ADPribosemoiety from NAD onto other cell surface proteins. ART2.2 induces T cell death byactivating the cytolytic P2X7 purinoceptor via ADP-ribosylation. Here we report thegeneration of ART2.2-blocking single domain antibodies from an immunized llama. Thevariable domain of heavy-chain antibodies (VHH domain) represents the smallest knownantigen-binding unit generated by adaptive immune responses. Their long CDR3 endowsVHH domains with the extraordinary capacity to extend into and block molecular clefts.Following intravenous injection, the ART2.2-specific VHH domainss effectively shut-off theenzymatic and cytotoxic activities of ART2.2 in lymphatic organs. This blockade was highlyspecific (blocking ART2.2 but not the related enzymes ART1 or ART2.1), rapid (within 15minutes after injection) and reversible (24 hours after injection). Our findings constitute aproof of principle that opens up a new avenue for targeting leukocyte ecto-enymes in vivo andthat can serve as a model also for developing new antidotes against ADP-ribosylating toxins.