PROTECTION OF MICE FROM INHALED RICIN BY VACCINATION WITH RICIN OR BYPASSIVE TREATMENT WITH HETEROLOGOUS ANTIBODY

Mice were vaccinated subcutaneously with 25 mug kg-1 of ricin in the p resence of Freund's complete adjuvant or Ribi(TM) adjuvant, followed b y a boost 14 days later with 50 mug kg-1 ricin in Freund's incomplete adjuvant or Ribi adjuvant, respectively. Three subsequent boosts at 28 -day intervals with 25 mug kg-1 ricin yielded high anti-ricin antibody titres as determined by ELISA. Vaccinated animals were exposed to an aerosolized LD99 dose of ricin. With the exception of one death not at tributable to ricin intoxication, all vaccinated mice survived the let hal aerosol exposure. In addition, a passive protection regimen was ev aluated in mice pretreated with 100 mug purified goat anti-ricin IgG a dministered intravenously, and then challenged with ricin intravenousl y. All were resistant to 125 mug kg-1 of ricin, a dose greater than 25 times the intravenous lethal dose. Mice injected intravenously with 5 mg of the same IgG were protected from a lethal aerosol challenge. Th ese results indicated that it is possible to protect animals from inha led ricin by vaccination or passive administration of specific antibod ies.