Monoclonal anti-vasopressin (VP) antibodies penetrate into VP neurons, in vivo.

The fate of monoclonal anti-vasopressin antibodies (VP-MAbs) injected in vivo into the paraventricular nucleus (PVN) of the rat brain was studied by immunocytochemistry. Depending on the post survival time, VP-MAbs contained in an ascites fluid were stained at different levels of the VP neurons: the cytoplasm of the PVN neurons, the fibres of the median eminence and the granular layer of the Gyrus Dentatus. The identification of endogenous peptides synthesized by PVN neurons showed that the VP-MAbs uptake was specific: it did not appear either in the oxytocinergic neurons or in the non immunoreactive neurons of the Brattleboro rat brain, this rat being genetically incapable of synthesizing central VP. Conversely, VP-MAbs only penetrated into the VP neurons: ascites fluid containing monoclonal antibodies prepared against bovine thyroglobulin (the carrier conjugated to VP in our immunizations) was neither stained in magnocellular neurons nor carried in nerve fibres. The neuronal uptake and transport of VP-MAbs occurred in vivo: they were totally inhibited by heating of the ascites fluid at 56 degrees C for 30 min; this treatment did not alter the VP-MAbs themselves but probably destroyed some thermic sensitive component essential to the macromolecule internalization. The biological effects of antibodies injected in vivo have been reported. The results described here suggest that some specific antibodies passively transferred into the brain could act directly on the peptide synthesis recognized by the antibodies.

Comparison of three immunoassays in the screening and characterization of monoclonal antibodies against arginine-vasopressin.

A method for screening monoclonal antibodies (McAbs) to neuropeptides was evaluated using 8-arginine-vasopressin (AVP) as a model. Mice were immunized with AVP-thyroglobulin conjugate and their spleen cells were fused with X 63-Ag8.653 mouse myeloma cells. The resulting hybridoma supernatants were screened for specific antibody production using 3 different assays: solid phase enzyme radioimmunoassay in Terasaki plates (Ter-ELISA), liquid phase radioimmunoassay (LPRIA) and an immunohistochemical technique. From 2 independent fusions, 7 McAbs specific for AVP were obtained. They belonged to the IgG1 subclass and reacted more strongly to the ring part of the nonapeptide. The screening strategy proposed relies upon a crude selection of conjugate-reacting hybridomas, followed by neuropeptide-specific hybridoma identification using both LPRIA (with radioiodinated synthetic peptide) and an immunohistochemical technique (to detect natural neuropeptide). During subcloning steps Ter-ELISA is then chosen, to select for specific clones and to eliminate those reacting with the carrier thyroglobulin.