RESUMEN
BACKGROUND: Factor VIIIa (FVIIIa) binds to activated FIX and enhances the activation of FX by several orders of magnitude. Deficiency of FVIII causes the bleeding disorder hemophilia A and is treated by i.v. infusion of FVIII concentrates. OBJECTIVES: To explore whether or not FVIII activity can be supplied by alternative molecules, e.g. molecules with FIXa-binding activity. METHODS: Conventional hybdridoma technology was used to discover antibodies exhibiting FVIII-like activity. RESULTS: We identified a series of antibodies specific for human FIX that mimicked the stimulatory effect of FVIIIa on FIXa. Upon binding to human FIXa, these antibodies enhanced the protease activity of FIXa towards its natural substrate FX about tenfold. A similar enhancement was also achieved with 5 pm FVIIIa (i.e. 16 mU mL(-1) or 1.6% activated FVIII). Procoagulant activity of these anti-FIXa antibodies was observed in model systems containing purified proteins as well as in plasma. CONCLUSION: Our findings show that FVIII can, at least partially, be replaced by an unrelated molecule. Procoagulant antibodies might potentially aid the development of an FVIII substitute for hemophilia A treatment.
Asunto(s)
Anticuerpos Monoclonales/farmacología , Factor IX/inmunología , Factor IXa/agonistas , Animales , Anticuerpos Monoclonales/inmunología , Sistema Libre de Células , Evaluación Preclínica de Medicamentos , Activación Enzimática/efectos de los fármacos , Factor IXa/inmunología , Factor VIIIa/fisiología , Factor X/metabolismo , Hemofilia A/tratamiento farmacológico , Humanos , Hibridomas/inmunología , Masculino , Ratones , Ratones Endogámicos BALB CRESUMEN
A single chain Fv antibody fragment (scFv) was obtained from a synthetic phage-antibody library after four rounds of selection against purified preparations of potato leafroll luteovirus (PLRV). Nucleotide sequence analysis showed that the scFv belongs to the human V(H)3 family. DNA encoding the scFv was sub-cloned into pDAP2 such that a scFv-alkaline phosphatase fusion protein was produced by transformed bacteria following induction by isopropyl-beta-D-thiogalactopyranoside (IPTG). The fusion protein was obtained at concentrations of 10 mg/l of Escherichia coli culture medium and these fusion protein preparations were used directly in ELISA to detect PLRV in sap extracts from infected plants. Our work is the first report of the selection of a scFv specific for a luteovirus from a synthetic phage-display library and the production of a fusion protein with alkaline phosphatase for the detection of PLRV in infected plants. The results demonstrate the potential of scFv and enzyme-scFv fusion proteins in routine testing for plant virus infection.