PT - JOURNAL ARTICLE AU - Michael J. Pereira AU - Beau Wager AU - Ryan J. Garrigues AU - Eva Gerlach AU - Joshua D. Quinn AU - Alex Dowdell AU - Marcia S. Osburne AU - Wolfram R. Zückert AU - Peter Kraiczy AU - Brandon L. Garcia AU - John M. Leong TI - Lipoproteome screening of the Lyme disease agent identifies novel inhibitors of antibody-mediated complement killing AID - 10.1101/2021.09.23.461563 DP - 2021 Jan 01 TA - bioRxiv PG - 2021.09.23.461563 4099 - http://biorxiv.org/content/early/2021/09/23/2021.09.23.461563.short 4100 - http://biorxiv.org/content/early/2021/09/23/2021.09.23.461563.full AB - Spirochetal pathogens such as the causative agent of Lyme disease, Borrelia burgdorferi sensu lato, encode an abundance of lipoproteins; however, due in part to their evolutionary distance from more well-studied bacteria such as Proteobacteria and Firmicutes, very few spirochetal lipoproteins have assigned functions. Indeed, B. burgdorferi devotes almost 8% of its genome to lipoprotein genes and interacts with its environment primarily through the production of at least eighty surface-exposed lipoproteins throughout its tick vector-vertebrate host lifecycle (57). Several B. burgdorferi lipoproteins have been shown to serve diverse roles, such as cellular adherence or immune evasion, but the functions for most B. burgdorferi surface lipoproteins remain unknown. In this study, we developed a B. burgdorferi lipoproteome screening platform utilizing intact spirochetes that enables the identification of previously unrecognized host interactions. As spirochetal survival in the bloodstream is essential for dissemination, we targeted our screen to C1, the first component of the classical (antibody-mediated) complement pathway. We identified two high-affinity C1 interactions by the paralogous lipoproteins, ErpB and ErpQ. Using biochemical, microbiological, and biophysical approaches, we demonstrated that ErpB and ErpQ inhibit the activated forms of the C1 proteases, C1r and C1s, and represent a new mechanistic class of C1 inhibitors that protect the spirochete from antibody-mediated complement killing by allosteric regulation. In addition to identifying a novel mode of complement inhibition, our study establishes a lipoproteome screening methodology as a discovery platform for identifying direct host-pathogen interactions that are central to the pathogenesis of spirochetes, such as the Lyme disease agent.Significance Statement Spirochetal pathogens encode an abundance of lipoproteins that can provide a critical interface with the host environment. For example, Borrelia burgdorferi, the model species for spirochetal biology, must survive an enzootic life cycle defined by fluctuations between vector (tick) and vertebrate host. While B. burgdorferi expresses over eighty surface lipoproteins— many of which likely contribute to host survival—the B. burgdorferi lipoproteome is poorly characterized. Here, we generated a platform to rapidly identify targets of B. burgdorferi surface lipoproteins and identified two orthologs that allosterically inhibit complement C1 subcomponents, conferring resistance to classical complement killing. This work expands our understanding of complement evasion mechanisms and points towards a discovery approach for identifying host-pathogen interactions that are central to spirochete pathogenesis.Competing Interest StatementThe authors have declared no competing interest.