Sydney Scott

Sydney, a sophomore studying Biochemistry at Spelman College, built a user-defined peptide-MHC library in E.coli.

The major histocompatibility complex (MHC) is a cell surface protein that plays an essential role in the adaptive immune response by presenting foreign peptides to T cells. Prediction of immunogenic MHC-binding peptides is an important aspect of immunotherapy, which capitalizes on the interaction between immune cells and peptide-MHC (pMHC) on tumor cells. When I first stepped into the Broad, I was slightly intimidated by the scientific excellence around me. However, walking out at the end of a transformative nine weeks, there is no question that I belong in that environment. Because of my experience in BSRP, I am inspired and invigorated to pursue a career in science, and I will forever look upon my time at the Broad with gratitude. Current predictive models do not account for many of the MHC alleles that exist in the human population, which bind different peptide motifs. In addition, presentation prediction models learned from pMHC affinity data provide incomplete insight on whether the peptide will be immunogenic, i.e., elicit a functional T cell response. Therefore, this project suggests a method for large-scale multi-allelic pMHC library production with the addition of thermostability profiling. Rather than using cell lines to isolate MHC-bound peptides, this model uses E. coli to express the desired MHC alleles and peptide library. This allows the user to define the library content, thus increasing the genetic diversity and scale of pMHC binding data. Additionally, thermostability profiling by subjecting the pMHC to varying amounts of heat is hypothesized to provide more insight into overall immunogenicity. This method has produced significant peptide binding content with the most commonly tested MHC allele, HLA-A*02:01. Therefore, the next step executed in this project was testing an allele that has little available data, in this instance HLA-C*04:01. Preliminary results show that it is possible to accomplish the soluble expression of HLA-C*04:01 in E.coli as well as detect HLA-C*04:01 bound peptides through mass spectrometry. These results confirm that a multi-allelic pMHC library is possible. Increasing the genetic diversity of the peptide-MHC library and profiling the peptide thermostability can improve upon existing MHC predictive models and help design more effective and personalized immunotherapy treatments.

Project: Thermostability profiling of a user-defined peptide-MHC library

Mentors: Kasidet Manakongtreecheep & Beck Holden

PI: Hacohen Lab