{"doi":"10.1101/2024.11.28.625832","title":"The TLR7/8 agonist INI-4001 enhances the immunogenicity of a Powassan virus-like-particle vaccine","abstract":"Abstract Powassan virus (POWV) is a pathogenic tick-borne flavivirus that causes fatal neuroinvasive disease in humans. There are currently no approved therapies or vaccines for POWV infection. Here, we develop a POW virus-like-particle (POW-VLP) based vaccine adjuvanted with the novel synthetic Toll-like receptor 7/8 agonist INI-4001. We demonstrate that INI-4001 outperforms both alum and the Toll-like receptor 4 agonist INI-2002 in enhancing the immunogenicity of a dose-sparing POW-VLP vaccine in mice. INI-4001 increases the magnitude and breadth of the antibody response as measured by whole-virus ELISA, induces neutralizing antibodies measured by FRNT, reduces viral burden in the brain of infected mice measured by RT qPCR, and confers 100% protection from lethal challenge with both lineages of POWV. We show that the antibody response induced by INI-4001 is more durable than standard alum, and 80% of mice remain protected from lethal challenge 9-months post-vaccination. Lastly, we show that the protection elicited by INI-4001 adjuvanted POW-VLP vaccine is unaffected by either CD4 + or CD8 + T cell depletion and can be passively transferred to unvaccinated mice indicating that protection is mediated through humoral immunity. This study highlights the utility of novel synthetic adjuvants in VLP-based vaccines. Author summary Powassan virus (POWV) is an emerging pathogenic tick-borne flavivirus for which there is no vaccine. Current tick-borne flavivirus vaccines are less than ideal and use formalin-inactivated virus adjuvanted with alum. These vaccines require thorough inactivation of the antigen and frequent boosting to maintain immunity. In this study, we describe the development of a POWV vaccine using Powassan virus-like-particles (POW-VLPs) adjuvanted with either of two novel Toll-like receptor (TLR) agonists, the TLR4 agonist INI-2002 or the TLR7/8 agonist INI-4001. We show that INI-4001 enhances the antibody response, reduces POWV neuroinvasion, and elicits full protection from lethal POWV infection in mice prime-boost vaccinated with low doses of POW-VLP. We further show that this protection is mediated by a humoral immune response which is both broader and more durable than a POW-VLP vaccine formulated with alum. These findings demonstrate the effectiveness of the novel synthetic TLR7/8 agonist INI-4001 as an adjuvant for low-dose VLP-based vaccines and the ability of this vaccine platform to improve upon current tick-borne flavivirus vaccine methodology.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2024,"id":489341,"datarank":0.16479184330021646,"base_score":1.0986122886681096,"endowment":1.0986122886681096,"self_citation_contribution":0.16479184330021646,"citation_network_contribution":0.0,"self_endowment_contribution":0.16479184330021646,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":2,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9522,"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":383288,"name":"Walid Abdelwahab","orcid":"0000-0003-4258-0026","position":1,"is_corresponding":false},{"id":896105,"name":"Karthik Siram","orcid":"0000-0002-7669-3945","position":2,"is_corresponding":false},{"id":464584,"name":"Christopher J. Parkins","orcid":null,"position":3,"is_corresponding":false},{"id":465011,"name":"Henry F. Harrison","orcid":"0000-0001-6999-2034","position":4,"is_corresponding":false},{"id":274980,"name":"Samantha R. Osman","orcid":"0000-0002-5011-3869","position":5,"is_corresponding":false},{"id":1334684,"name":"Dillon Schweitzer","orcid":null,"position":6,"is_corresponding":false},{"id":383292,"name":"Jay T. Evans","orcid":"0000-0001-6602-0272","position":7,"is_corresponding":false},{"id":383293,"name":"David J. Burkhart","orcid":"0000-0001-6508-6296","position":8,"is_corresponding":false},{"id":290891,"name":"Amelia K. Pinto","orcid":"0000-0002-7147-3978","position":9,"is_corresponding":false},{"id":282037,"name":"James D. Brien","orcid":"0000-0002-1670-8041","position":10,"is_corresponding":false},{"id":1083460,"name":"Jessica L. Smith","orcid":"0000-0002-2381-861X","position":11,"is_corresponding":false},{"id":463506,"name":"Alec J. Hirsch","orcid":"0000-0002-8613-0740","position":12,"is_corresponding":false},{"id":1116162,"name":"Michael Crawford","orcid":"0000-0001-7779-4636","position":0,"is_corresponding":true}],"reference_count":61,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T02:08:23.929823Z","pmid":"39677812","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":[]}