Effects of anti-cocaine vaccine and viral gene transfer of cocaine hydrolase in mice on cocaine toxicity including motor strength and liver damage

Abstract

In developing an vivo drug-interception therapy to treat cocaine abuse and hinder relapse into drug seeking provoked by re-encounter with cocaine, two promising agents are: (1) a cocaine hydrolase enzyme (CocH) derived from human butyrylcholinesterase and delivered by gene transfer; (2) an anti-cocaine antibody elicited by vaccination. Recent behavioral experiments showed that antibody and enzyme work in a complementary fashion to reduce cocaine-stimulated locomotor activity in rats and mice. Our present goal was to test protection against liver damage and muscle weakness in mice challenged with massive doses of cocaine at or near the LD50 level (100-120 mg/kg, i.p.). We found that, when the interceptor proteins were combined at doses that were only modestly protective in isolation (enzyme, 1mg/kg; antibody, 8 mg/kg), they provided complete protection of liver tissue and motor function. When the enzyme levels were ~400-fold higher, after in vivo transduction by adeno-associated viral vector, similar protection was observed from CocH alone.

Fig. 1

Grip strength after cocaine challenge. Indicated treatments are: control (n = 10, saline, i.p.), CocH (n = 8, enzyme, 1 mg/kg i.p.), vaccine (n = 10, see Methods), and vaccine plus CocH (n = 10). All pretreatments except vaccine were delivered 1 hr before the drug challenge (100 mg/kg i.p.). Four-paw grip strength was determined 20 min after cocaine administration (units are grams). Animals with no pretreatment did not survive. Statistical significance: * (p < 0.01 vs control and vaccine + CocH); ** (p < 0.001 vs control and vaccine + CocH).

Fig. 2

Cocaine-induced liver dysfunction. Plasma ALT activity was determined 24 hr after challenge with 120 mg/kg cocaine, i.p (two 60-mg/kg doses 10 min apart). Pretreatment groups were: saline (n = 5), and (n = 8 for all) antibody (AB, 16 mg/kg), enzyme (CocH, 1 mg/kg), vaccine, enzyme plus antibody (CocH + AB) and enzyme plus vaccine (CocH + vaccine). ALT activity in each of the double-treatment groups (CocH + AB and CocH + vaccine) was significantly lower than in all other groups *** (p < 0.0001).

Fig. 3

Liver Pathology. A) H&E-stained liver sections from control mice (a), and mice given cocaine, 120 mg/kg, after the following pretreatments: b) none; c) anti-cocaine antibody; d) anti-cocaine vaccine; e) CocH; f) CocH + vaccine. Arrows indicate red-stained areas of centrilobular necrosis. B) Quantitative analysis of histological outcomes: cross sectional areas of damaged zones in arbitrary units (mean ± SEM, n = 5-8). Statistical significance: *** p < 0.001 vs all “no-asterisk” groups.