UC San Diego

Antibiotic-resistant bacteria such as methicillin- resistant Staphylococcus aureus (MRSA) and multi-drug resistant Pseudomonas aeruginosa present a growing concern for global health and safety. Because infections caused by such pathogens are often difficult to treat with standard antibiotics, the development of novel therapies is urgently needed. We are proposing an entirely novel approach to anti-infective therapy mediated by aptamers, an emerging therapeutics class, conjugated with the "alpha -Gal" epitope of galactosyl-alpha-l,3-galactosyl-beta-l,4- N-acetylglucosamine. The conjugated aptamer, or "alphamer, " could theoretically immunize the host and lead to bacterial clearance through complement activation and phagocytosis by redirecting preexisting antibodies against the target pathogen. The main goal of the thesis project, conducted in collaboration with Altermune Technologies, LLC, was to establish proof-of-concept (POC) for the proposed alphamer-mediated therapy utilizing a published group A Streptococcus (GAS) specific DNA aptamer, 20A24P. Firstly, the binding of 20A24P to multiple GAS serotypes was confirmed. Truncating 20A24P enhanced the binding affinity to GAS, and the target antigen of 20A24P was determined to be the M1 protein. A 5'-alpha-Gal alphamer conjugate of 20A24P, named [alpha]20A24P, was synthesized and binding to GAS strains observed. In addition, [alpha]20A24P was capable of recruiting mouse IgG and IgM antibodies, promoting phagocytosis of GAS by purified human neutrophils and inhibiting the outgrowth of a hypervirulent GAS strain in human blood. To further determine the potential of alphamers as novel anti- bacterial drugs, ongoing experiments explore the activity of [alpha]20A24P in GAS killing assays with phagocytes and in a mouse model of necrotizing fasciitis that were established in this project