Protection against ricin intoxication in vivo by anti-idiotype vaccination.

A BALB/c murine anti-ricin monoclonal antibody (mAb BG11-G2, IgG1K), was recently isolated and shown to passively protect syngeneic mice against ricin intoxication in vivo. New Zealand White rabbit polyclonal anti-idiotype (anti-Id) antibodies were raised to BG11-G2 anti-ricin mAb, and rendered specific by repeated absorption over agarose normal mouse immunoglobulin (Ig). The absorbed rabbit anti-Id antibodies lost reactivity to normal mouse Ig and to a BALB/c anti-T-2 mycotoxin IgG1K mAb (HD11), but remained reactive with BG11-G2 anti-ricin mAb. The rabbit anti-Id inhibited the binding of BG11-G2 mAb to ricin-coated wells, and elicited a specific and protective anti-ricin antibody response in naive BALB/c mice. Whereas all mice vaccinated with a control rabbit anti-Id antibody preparation died from in vivo ricin challenges, mice immunized with the rabbit anti-Id specific for BG11-G2 mAb were protected to various degrees. All mice vaccinated with rabbit anti-Id to BG11-G2 and challenged with ricin doses of 35 and 50 micrograms kg-1 body weight died from the challenge; however, a delay in the elapsed time between ricin administration and death was observed in these mice as compared to that of the control anti-Id-immune mice. Five of seven mice vaccinated with the rabbit anti-Id to BG11-G2 and subsequently challenged in vivo with a ricin dose of 20 micrograms kg-1 body weight survived the lethal in vivo ricin challenge, whereas all the control mice died.(ABSTRACT TRUNCATED AT 250 WORDS)