Authors
M Mugnier1; 1 John Hopkins, United States Discussion
Trypanosoma brucei, the causative agent of human and animal African trypanosomiasis, lives an entirely extracellular life cycle in its mammalian host. Despite constant exposure to host antibody, this parasite manages to maintain chronic infections that can last for years. T. brucei manages to sustain such long infection through antigenic variation of its dense variant surface glycoprotein (VSG) coat. Using an enormous repertoire of VSG-encoding genes, the parasite continually “switches” expression to new VSGs, escaping recognition by host antibody. Work from our lab using high-throughput sequencing to characterize the repertoire of VSGs expressed during chronic infections in humans has revealed that the VSG repertoire is quickly evolving, and parts of the VSG protein that are suspected to be targeted by host antibody appear most likely to mutate. Thus, the host antibody response is critical for shaping this parasite’s antigenic repertoire. Despite its importance, the principles governing antibody recognition of VSG remain poorly understood. Here, we present the development of VSG Phage Immunoprecipitation Sequencing (PhIP-seq), an approach for high-throughput epitope mapping of VSGs. Using a phage display library containing peptides from 13,171 VSGs, we are able to track the specificity and dynamics of the antibody response to VSG in high resolution, in both experimental and natural infections. In addition to informing the design of serodiagnostics for trypanosomiasis, this experimental system is likely to reveal fundamental insight into the co-evolution of the host-pathogen interface over time 
