Neutralization and binding activity of a human single-chain antibody to ricin toxin

Abstract

Ricin toxin (RT), extracted from castor bean, is a type II ribosomeinactivating protein (RIP). As a biothreat agent, there is no effective antidote for RT to date, but recent advances in antibody research may have meet this need. This study aimed to produce human single-chain antibody variable fragments (HuscFvs) that bind to and interfere with RT activity for further clinical use. The purified RT component was used in phage biopanning to select ricin-bound HuscFv-displayed phage clones from synthetic (Tomlinson I + J) phage display libraries. The selected HuscFv, named JE11, showed an almost 100% protective effect to HeLa cells by mixing with RT at a 1:1000 ratio in vitro. The antibody showed an 83% protection against injection of 2 × LD 50 RT dose mice within 72 h. This research has therapeutic potential for the diagnosis and treatment of RT poisoning.

Preparation of Equine Immunoglobulin F(ab′)2 against Smallpox and Evaluation of its Immunoprotective Effect

“…The experimental groups comprised a normal cell control (without virus, without F(ab′) 2 ); virus control (with virus, without F(ab′) 2 ); and normal horse immunoglobulin control (with virus, with normal horse immunoglobulin). When cells in the virus control group were dead, MTT (0.25 mg/mL) was added at 200 mL/well for 4 h. The MTT was then aspirated, and termination solution (10% SDS + 0.01 mol/L HCl) at 200 ml/well was added and incubated for 8 h. The OD value was detected at 570 nm [15].…”