Detection and micro-scale isolation of a low molecular mass paralysis toxin from the tick, Argas (Persicargas) walkerae

This study describes the isolation of a 11 kDa paralysis toxin from crude l arval extracts of Argas (Persicargas) walkerae by exploiting the cross-reac tivity of a monoclonal antibody (4B12), directed against the paralysis toxi n of Rhipicephalus evertsi evertsi. This low molecular mass is in contrast to previous findings of a 60-70 kDa toxin for A. (P.) walkerae, but is simi lar to neurotoxins isolated from venomous forms of the class Arachnida, whi ch comprise the orders Araneae (spiders), Scorpionida (Scorpions) and Acari (ticks and mites). Since numerous antigenic bands, ranging between 11 and 115 kDa, were detected by the monoclonal antibody 4B12, the possibility of toxin-complex formation and the effect of pH on the latter were investigate d by means of HPLC and ammonium sulphate precipitation. The results suggest that physiological conditions, with respect to pH and ionic strength, prom ote the formation of heterogeneous toxin-complexes while an acidic pH favou rs the formation of a more homogeneous toxin-containing complex. Furthermor e, the effect of partially purified toxin on neurotransmitter release from crude rat brain synaptosomes was investigated, since tick paralysis toxins are hypothesised to inhibit neurotransmitter release from the presynaptic t erminal. Both calcium-dependent, as well as calcium-independent release was inhibited by the toxin-containing sample.