Tick-paralysis toxoid: an effective immunizing agent against the toxin of Ixodes holocyclus.

Glutaraldehyde treatment of the toxin of the Australian paralysis tick Ixodes holocyclus produced a potent, immunogenic toxoid. Three subcutaneous injections (2 to 4 weeks apart) into rabbits produced very high antitoxin titres in their serum, although circulating antitoxin titres declined in the absence of stimulation. Twenty weeks later, immunized rabbits were unaffected by lethal doses of toxin injected subcutaneously.

Tick (Ixodes holocyclus) paralysis in the dog--induction of immunity by injection of toxin.

Three beagle dogs were immunised against the paralysing effects of holocyclotoxin, using toxic extracts derived from salivary glands of the Australian paralysis tick, Ixodes holocyclus. Upon subsequent challenge with four ED50's of toxin the animals were completely immune, whereas during the early stages 2 of 3 dogs became paralysed after injection with 0.5 ED50. Three immunised beagles, on which 15 I. holocyclus ticks had fed, showed no symptoms but a control beagle became paralysed after 4 I. holocyclus females fed on it. Treatment was instituted immediately upon the onset of clinical signs and the dog recovered uneventfully.

Immunization of rabbits to produce high serum titres of neutralizing antibodies and immunity to the paralyzing toxin of Ixodes holocyclus.

Rabbits have been immunized against the effects of the paralyzing toxin of the Australian paralysis tick Ixodes holocyclus by injecting them with preparations extracted from tick salivary glands. Immunized rabbits were able to withstand doses of toxin known to kill unimmunized rabbits. Neutralizing antibodies were detectable in serum after 2-4 doses of the crude extract or of the relatively pure antigenic fraction. When injections were continued at intervals of from 2-7 weeks, hyperimmunity was retained for at least 68 weeks. Hyperimmune serum, reaching a very high titre of neutralizing antibodies, was obtained after 3-6 injections. Titres tended to decline when boosting ceased, but after a "rest period' high titres were restored by further boosting with normally lethal doses of toxin. No symptoms of tick paralysis developed despite low titres prior to boosting. Thus, once hyperimmunity had been established, high titres of circulating antibodies were not immediately essential for immunity to tick paralysis. An IgG fraction was obtained from rabbit serum using a Protein A-Sepharose method; 33.4 micrograms of IgG protein fully neutralized, and 19.5 micrograms IgG half neutralized, 1 micrograms of crude toxin protein. This procedure with rabbits may permit the production of a purified tick-paralysis antitoxin more suitable for human use than the existing antitoxin based on canine hyperimmune serum.

Norepinephrine as principal catecholamine in a specific neurone of an invertebrate (Boophilus microplus: Acarina).

Norepinephrine has been identified as the principal catecholamine in individual neurons of the synganglion of an arthropod, the cattle tick Boophilus microplus. This suggests that norepinephrine may have a hitherto unsuspected major physiological role in at least one group of invertebrates.