Polyclonal and monoclonal antibodies to PbTx-2-type brevetoxins using minute amount of hapten-protein conjugates obtained in a reversed micellar medium

Abstract Minute amount of Brevetoxin PbTx-3 (400 μg; 0.446 μmol) was converted into an hemisuccinate derivative (PbTx-3 HS) then covalently linked to bovine serum albumin (BSA) and ovalbumin (OVA) in a reversed micellar medium. According to the efficient cyclic synthetic procedure described, the epitope density of the conjugates was around 10 and 20 for OVA and BSA carriers, respectively. The kinetics of antibody production in sequential sera harvested from a single BALB/c mouse immunised by multiple intraperitoneal (i.p.) injections of PbTx-3-BSA conjugate was performed by enzyme-linked immunosorbent assay (ELISA). Two monoclonal antibodies (MAbs) against PbTx-3 were selected from fusion of the mouse immune splenocytes with the P3-X63-Ag 8.653 myeloma cells. In competitive inhibition ELISA experiments, both polyclonal antibodies and MAbs exhibited strong cross-reactivity (≥100%) to other PbTx-2-type toxins (PbTx-2 and -9) but low or moderate cross-reactivity (6–15%) to a PbTx-1-type toxin (PbTx-1). Moreover, using these two MAbs, a low cross-reactivity with okadaic acid (3%) was noticed but no significant cross-reactivity was observed with two ciguatoxins (CTX-1B and CTX-3C) over the concentration range studied. The apparent dissociation constant ( K D ) for the interaction of these MAbs with free PbTx-2-type toxins was in the 10 −6 –10 −7  M range. The performance of this MAb-based assay (limit of detection ≈5 ng/well; working range=8–150 ng/well) coupled with adequate extraction methods would provide an alternative assay to the mouse i.p. bioassay for routine shellfish monitoring. This production and characterisation of MAbs using small amount of polyether toxins in a reversed micellar medium appear most valuable for the development of immunoassays to other highly potent but poorly available marine polyether toxins like ciguatoxins (CTXs).