Suppression and treatment of experimental allergic encephalitis in guinea-pigs with the bovine spinal cord protein (BSCP).

Experimental allergic encephalitis (EAE) was suppressed in guinea-pigs that had been sensitized with 50 micrograms of bovine myelin basic protein (MyBP) in Freund's complete adjuvant (FCA) by daily injections of 500 micrograms of the bovine spinal cord protein (BSCP) in saline between day 8 (D 8) and D 23 after sensitization. Injections of 500 micrograms of bovine serum albumin in saline, or saline alone, did not suppress disease. Reversal of clinical disease was achieved with doses of 750 micrograms of BSCP in saline when treatment was begun within a day after the first sign of disease was observed. Six injections of 500 micrograms of BSCP in Freund's incomplete adjuvant (FIA) were required to suppress EAE whether BSCP-FIA injections were begun on D 0 or as late as D 8 when T cells sensitized to MyBP had invaded the central nervous system. When administration of BSCP-FIA was withheld until after disease onset, only three or four injections were needed to reverse clinical signs. BSCP appeared to be as effective quantitatively as MyBP in the suppression or treatment of disease. Because there is no cross-reaction between BSCP and MyBP at the antibody level, the present results raise the possibility that the suppressive activity of BSCP may be due to an amino acid sequence in BSCP and MyBP that is recognized only by T cells. When antigens were injected in FIA at 4 day intervals after sensitization, the onset of disease was delayed up to 5 days. Moreover, even bovine gamma-globulin appeared to have suppressive activity when injected three or four times in FIA. The findings suggest that assessments of the suppressive capacity of an antigen may be inaccurate if the antigen is injected in FIA frequently during the interval between sensitization and onset of disease.