{"doi":"10.1128/mbio.01804-24","title":"Exploiting the Affimer platform against influenza A virus","abstract":"ABSTRACT Influenza A virus (IAV) is well known for its pandemic potential. While current surveillance and vaccination strategies are highly effective, therapeutic approaches are often short-lived due to the high mutation rates of IAV. Recently, monoclonal antibodies (mAbs) have emerged as a promising therapeutic approach, both against current strains and future IAV pandemics. In addition to mAbs, several antibody-like alternatives exist, which aim to improve upon mAbs. Among these, Affimers stand out for their short development time, high expression levels in Escherichia coli , and animal-free production. In this study, we utilized the Affimer platform to isolate and produce specific and potent inhibitors of IAV. Using a monomeric version of the IAV trimeric hemagglutinin (HA) fusion protein, we isolated 12 Affimers that inhibit IAV infection in vitro . Two of these Affimers were characterized in detail and exhibited nanomolar-binding affinities to the target H3 HA protein, specifically binding to the HA1 head domain. Cryo-electron microscopy (cryo-EM), employing a novel spray approach to prepare cryo-grids, allowed us to image HA-Affimer complexes. Combined with functional assays, we determined that these Affimers inhibit IAV by blocking the interaction of HA with the host-cell receptor, sialic acid. Furthermore, these Affimers inhibited IAV strains closely related to the one used for their isolation. Overall, our results support the use of Affimers as a viable alternative to existing targeted therapies for IAV and highlight their potential as diagnostic reagents. IMPORTANCE Influenza A virus is one of the few viruses that can cause devastating pandemics. Due to the high mutation rates of this virus, annual vaccination is required, and antivirals are short-lived. Monoclonal antibodies present a promising approach to tackle influenza virus infections but are associated with some limitations. To improve on this strategy, we explored the Affimer platform, which are antibody-like proteins made in bacteria. By performing phage-display against a monomeric version of influenza virus fusion protein, an established viral target, we were able to isolate Affimers that inhibit influenza virus infection in vitro . We characterized the mechanism of inhibition of the Affimers by using assays targeting different stages of the viral replication cycle. We additionally characterized HA-Affimer complex structure, using a novel approach to prepare samples for cryo-electron microscopy. Overall, these results show that Affimers are a promising tool against influenza virus infection.","journal":"mBio","year":2024,"id":465994,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":4,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9564,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1190616,"name":"Alex J. Flynn","orcid":"0000-0002-9370-0879","position":1,"is_corresponding":false},{"id":469510,"name":"David P. Klebl","orcid":"0000-0002-3581-8334","position":2,"is_corresponding":false},{"id":1298252,"name":"Moisés H. Rojas Rechy","orcid":null,"position":3,"is_corresponding":false},{"id":979936,"name":"Christian Tiede","orcid":"0000-0003-0280-4005","position":4,"is_corresponding":false},{"id":105430,"name":"Ian A. Wilson","orcid":"0000-0002-6469-2419","position":5,"is_corresponding":false},{"id":469515,"name":"Stephen P. Muench","orcid":"0000-0001-6869-4414","position":6,"is_corresponding":false},{"id":979938,"name":"Darren C. Tomlinson","orcid":"0000-0003-4134-7484","position":7,"is_corresponding":false},{"id":1190617,"name":"Juan Fontana","orcid":"0000-0002-9084-2927","position":8,"is_corresponding":false},{"id":1190615,"name":"Oliver Debski-Antoniak","orcid":"0000-0001-8239-2738","position":0,"is_corresponding":true}],"reference_count":70,"raw_metadata":null,"created_at":"2026-07-19T02:04:54.606394Z","pmid":"39037231","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}