Alyssa Klee '18
Title: The Mutagenesis of the PD-L1 Inhibitory Ligand to Identify the Binding Site of the Novel PD-L1/B7-1 Pathway
Many antibodies in current immunotherapies block more than one inhibitory “pathway”. This results in the increased activation of T cells, and therefore increased side effects for the patient. Although this may occur in many common treatments, the identification of the unknown binding site between two proteins, PD-L1 and B7-1, would benefit the countless weaker patients who cannot handle these side effects.
Activities & Interests:
Founder and President of Somers Cancer Research, Founder and President of Math National Honor Society, SHS Varsity Volleyball, Downstate Juniors Volleyball, Chem Club Vice President, National Honor Society, Spanish National Honor Society, Spanish Club, Leo's Club, Netflix, Puppies, Founder of "Maelwhale".
I hypothesized that one or few of seven different amino acids on PD-L1 (a protein on the cancer cell) constitute the location of the binding site between PD-L1 and B7-1.
In order to determine the binding site, I mutated all seven of the suspected amino acids and expressed the mutants in COS cells, which are a line of monkey cells. I then found the binding rates of these mutants to proteins that the unmutated form usually binds, such as proteins PD-1 and B7-1. This was done in order to tell if the mutation I made in the protein was on the binding site or not. If the mutation was on the binding site, it would have a low binding rate. If it was not on the binding site, there would be a high binding rate.
Through the use of a flow cytometer (a machine that can detect binding rates of proteins by using fluorescence), I observed extremely low binding rates between PD-L1 and B7-1 when the following amino acids were mutated: M115, D49, K124 and R113. This means that these amino acids make up the binding site of PD-L1 and B7-1.
With the identification of the binding site of this novel pathway, pharma companies can begin to build new antibodies that block specifically the PD-1 pathway or the B7-1 pathway instead of blocking to both. Blocking only one pathway will decrease the side effects for many patients, so they can still receive the benefits of immunotherapy while having lower side effects.