Stimulation of anti-Brucella vaccination in mice by tetramisole, a phenyl-imidothiazole salt

The effect of tetramisole (hydrochloride of racemic 2, 3, 5, 6,-tetrahydro-6-phenyl-imidazo [2, 1-b] thiazole) on immunization was investigated in mice vaccinated by killed Brucella melitensis cells suspended in incomplete adjuvant. Immunity to Brucella abortus challenge was estimated by the reduction in number of B. abortus colonies per gram of spleen in those mice which escaped full immunization and also by calculation of mean infective doses for each group of mice. All tetramisole treatments significantly reduced the number of B. abortus live cells in spleen from infected mice. Tetramisole, injected twice (at the time of vaccination and 48 h later), induced a significant 3.5-fold increase of the protection brought about by Brucella vaccine alone. A single injection of 1.25 mg/kg at the time of vaccination resulted also in a significant increase of the immunity given by vaccination. No modifications of the vaccine potency were observed if tetramisole administration preceded vaccination. In such a mouse assay, tetramisole-induced stimulation was not accompanied by specific antibody increases, although measured by three serological tests.