An explanation on the limited efficacy of detoxication against VX toxicity by purified specific antibodies.

Studies on the mechanism of detoxication against VX toxicity by purified rabbit anti-VX antibodies were carried out in mice. VX (25 micrograms/kg) was injected subcutaneously immediately following intravenous injection of purified anti-VX antibodies. Blood concentration of free VX declined linearly as the antibody dose increased. Free VX concentration in brain was far lower than that in blood. When the dose of purified anti-VX antibodies was 8 and 6 mg/kg, respectively, free VX concentration in brain and blood approached 0. At the same time, the cholinesterase (ChE) activity in brain increased along with increasing antibody dose, with 70% of normal control value detected when 8 mg/kg antibodies were administered. On the other hand, anti-VX antibodies were not able to protect blood ChE unless the VX dose was lower than 10 micrograms/kg. The studies suggest that the protective action of purified rabbit anti-VX antibodies is from VX antibodies combining with the free VX in blood and extravascular tissue to reduce the amount of VX entering into the brain.