Anti-CTLA4 scFv, a Single—Chain Antibody, Can Prolong Expression of Escherichia. coli. beta-Galactosidase in Immune—Competent Mice

Objectives: To induce immune tolerance in immune-competent animals with a plasmid (p4F10-eB7) expressing a membranebound single-chain antibody against CTLA4. Materials and Methods: Twenty 9-week old immune-competent C57B/L6 mice were divided into 2 groups. Ten mice received an intramuscular injection of 50 μL of endotoxin-free pCBLacZ plasmid at a concentration of 1 mg/mL in phosphate buffer in the left anterior tibialis. The plasmid codes for the potent immunogen, Escherichia coli beta-galactosidase in transduced muscle fibers. Ten mice received a co-injection of p4F10-eB7 with pCBLacZ. Results: We examined the expression of beta-galactosidase in muscle fibers on the 6th and 12th days after the intramuscular injection. The average number of fibers expressing beta-galactosidase was 43.6 in the mice receiving 2 plasmids as compared with 2.2 in the mice receiving only pCBLacZ (p= 0.015, by the Mann-Whitney test). There was no significant difference in the expression of beta-galactosidase between these 2 groups on day 12, at 0.4 Vs 1.4 fibers (p=0.419). Conclusions: Expression of anti-CTLA4 antibody in muscle cells prolonged the expression of a strong immunogen, E. coli beta-galactosidase in transduced muscle fibers of immune-competent mice. The probable mechanism could be anergy of activated cytotoxic T cells induced by activation of CD152 after interaction with the single-chain antibody. (Tzu Chi Med J 2004; 16:25-31)