Many proteins work in concert during the immune response which, in aplastic anemia, results in the destruction of blood stem and progenitor cells in the bone marrow. One subset of these cells, CD4 T cells, requires the actions of a specific protein known as Protein Kinase C-theta, or PKC-theta. Without PKC-theta, CD4 T cells are not able to drive the pathology associated with aplastic anemia. Using a pharmacological inhibitor of PKC-theta in our mouse model of aplastic anemia, we have previously found that turning this protein off at the peak of disease can rescue mice from lethal bone marrow failure.
In our current project, we are exploring a new way to turn off PKC-theta. We are using a small synthetic molecule (cell penetrating peptide) linked to an antibody raised against PKC-theta to interrupt its ability to activate CD4 T cells. The progress we have made during our first year shows that we can deliver the antibody (which binds to PKC-theta very tightly and with high specificity) into human cells much more efficiently than other delivery reagents that are commercially designed to do this. Furthermore, we see that once we deliver the anti-PKC-theta to human CD4 T cells, it has the predicted and desired effect of dampening those immune responses that are required for the progression of aplastic anemia. We have looked at certain other proteins that are highly expressed during disease, and found that all of these are diminished in their expression when we deliver anti-PKC-theta into human CD4 T cells. We have also begun experiments to determine how this novel approach affects disease progression in a humanized model of aplastic anemia.
During the second year of our award, we will continue to define the mechanisms by which our cell penetrating anti-PKC-theta acts to prevent CD4 T cells from becoming pathogenic, autoreactive cells and how effective this approach is in lessening the symptoms of aplastic anemia, using our humanized mouse model.
Many proteins work in concert during an abnormal immune response which, in aplastic anemia, results in the destruction of blood stem and progenitor cells in the bone marrow. One subset of these cells, T cells, requires the actions of a specific protein known as Protein Kinase C-theta, or PKC-theta. Without PKC-theta, T cells are not able to drive the pathology associated with aplastic anemia. Using a pharmacological inhibitor of PKC-theta in our mouse model of aplastic anemia, we have previously found that turning this protein off at the peak of disease can significantly prolong the lifespan of mice with aplastic anemia.
In our current project, we explored a new way to turn off PKC-theta. We used a small synthetic molecule (cell penetrating peptide) linked to an antibody that recognizes PKC-theta to interrupt its ability to activate T cells. With funding provided by the AA&MDS International Foundation, Inc., we have developed synthetic molecules capable of delivering the antibody (which binds to PKC-theta very tightly and with high specificity) into human cells much more efficiently than other commercial delivery reagents that are designed to do this. Furthermore, we observed that once we delivered the anti-PKC-theta to human T cells, it had the predicted and desired effect of dampening those immune responses that are required for the progression of aplastic anemia. We have looked at certain other proteins that are highly expressed during disease, and found that all of these are diminished in their expression when we deliver anti-PKC-theta into human T cells.
Our experiments further showed that when we delivered the PKC-theta antibody into human T cells, then transferred these cells into a special strain of mice to create a bone marrow failure that is very similar to human aplastic anemia, we found that the mice lived significantly longer than mice that received human T cells that were not treated the antibody to PKC-theta.
Altogether, the results we have generated suggest that delivering an antibody to PKC-theta into human T cells decreases the activity of PKC-theta and may lay the foundation for a novel therapeutic approach to treating aplastic anemia.
Dr. Minter is currently researching how notch signaling contributes to pathology and disease progression during immune-mediated bone marrow failure.