N-terminal amino acids of MBP—produces a more efficient MHC binder, enhanced immune phenomena, and a more efficient immunotherapeutic.
More importantly, substituted peptides also worked at a later and more clinically relevant stage of the disease, i.e., during remission after the onset of clinical symptoms. When researchers took mice that had progressed to stage 2 of EAE and tolerized them with the 4-tyrosine-substituted peptide, the mice did not get worse; in fact, they got better and stayed better for a long time. The peptide did not cause a relapse, and seemed to block a relapse—in short, it appeared to induce remission in clinically ill animals. Obviously, this result suggests a more realistic and clinically relevant way to administer the vaccine, namely when patients present with clinical disease. This model would be particularly important in diseases marked by a similar exacerbation-and-remission cycle, including rheumatoid arthritis, systemic lupus erythematosus, and MS.
To address concerns about the “innocent bystander” effects that this approach might cause, researchers tolerized mice with a single determinant of MBP and then induced them with spinal cord homogenate containing the entire gamut of proteins from the myelin sheath. The mice were protected. And in a related experiment, separate T-cell clones recognizing determinants A and B of myelin were transferred to naive mice, but when they were then tolerized with a single determinant, it turned off both clones. Something other than the apoptosis or anergy of that single T-cell clone was occurring. Whatever the mechanism, however, the results were dramatic: sick mice looked and acted normal after 24 hours, and their large inflammatory lesions had disappeared.
Researchers speculate that the peptide was not just killing cells but also turning off the inflammatory milieu through some unknown counter-regulatory mechanism. This has important implications for vaccine development strategies: instead of identifying the autoantigens, and hence the regulatory peptide, it might be possible to understand the counterinflammatory mechanisms and thereby bypass peptide immunotherapy entirely. One candidate involves not only the recognition of the antigen but also the regulation of T-cells themselves. Research currently underway suggests that this T-cell immunoregulatory circuit is very active in the exacerbating-remitting characteristics of EAE and may have a role to play in immunotherapy.
The idea would be to enhance this regulatory role, possibly by using peptides of T-cell receptors, but at present researchers do not know which T-cell receptors to pursue. In the clonal transfer experiment cited above, peptide A administered when disease has progressed to stage 2 will turn the disease off; but if anti-IL-4 is administered at the same time, it completely blocks the therapeutic effect of the peptide. This suggests, but by no means proves, that regulatory cytokines might be a central focus in efforts to bypass peptide vaccination immunotherapy and treat autoimmune diseases more directly.
T-Cell Hybridoma Cytokine Regulation. Researchers have investigated this question in a line of retroviral gene products that make it possible to transduce or infect cells with selected genes. For example, researchers “tag” retroviruses with green fluorescent protein to tell which cells are infected, or