Nanoparticle-delivered TLR4 and RIG-I agonists enhance immune response to SARS-CoV-2 subunit vaccine

• Type of Material: Article
• Authors: Alexandra Atalis, Georgia Institute of Technology; Mark C. Keenum, Georgia Institute of Technology; Bhawana Pandey, Georgia Institute of Technology; Alexander Beach, Georgia Institute of Technology; Pallab Pradhan, Georgia Institute of Technology; Casey Vantucci, Georgia Institute of Technology; Laura O'Farrell, Georgia Institute of Technology; Richard Noel, Georgia Institute of Technology; Ritika Jain, Georgia Institute of Technology; Justin Hosten, Georgia Institute of Technology; Clinton Smith, Georgia Institute of Technology; Liana Kramer, Georgia Institute of Technology; Angela Jimenez, Georgia Institute of Technology; Miquel Ochoa, Georgia Institute of Technology; David Frey, Georgia Institute of Technology; Krishnendu Roy, Emory University
• Language: English
• Date: 2022-07-01
• Publisher: Elsevier
• Publication Version: Final Published Version
• Copyright Statement: © 2022 Elsevier B.V. All rights reserved.
• Final Published Version (URL): http://dx.doi.org/10.1016/j.jconrel.2022.05.023
• Title of Journal or Parent Work: Journal of Controlled Release
• Volume: 347
• Start Page: 476
• End Page: 488
• Grant/Funding Information: Research reported in this publication was supported in part by the Pediatrics/Winship Flow Cytometry Core of Winship Cancer Institute of Emory University, Children's Healthcare of Atlanta and National Institutes of Health - National Cancer Institute (NIH/NCI) under award number P30CA138292.; This work was partially funded by National Institutes of Health - National Institute of Allergy and Infectious Disease (NIH/NIAID) grant U01-AI124270-02 to KR, funds from the Georgia Tech Foundation to KR, the National Science Foundation Graduate Research Fellowship to AA, the NIH T32 Cellular and Tissue Engineering training fellowship (National Institutes of Health (NIH) T32 Cellular and Tissue Engineering Training Fellowship grant T32-GM0843) to AA and AB, and the Robert A. Milton Chaired Professorship to KR.
• Keywords: Signal transduction; Activation; Intranasal versus intramuscular vaccination; Science & Technology; Pharmacology & Pharmacy; Recognition; Cell subsets; Coronavirus; SARS-CoV-2 spike protein; Adjuvants; Antibody response; Chemistry, Multidisciplinary; Monophosphoryl lipid A; Adaptive immune response; RNA viruses; Chemistry; COVID-19 protein subunit vaccine; Physical Sciences; Combination adjuvant; Life Sciences & Biomedicine; Stranded RNA
• Research Categories: Engineering, Biomedical; Biology, Cell; Health Sciences, Public Health; Health Sciences, Epidemiology; Health Sciences, Immunology

Abstract

Despite success in vaccinating populations against SARS-CoV-2, concerns about immunity duration, continued efficacy against emerging variants, protection from infection and transmission, and worldwide vaccine availability remain. Molecular adjuvants targeting pattern recognition receptors (PRRs) on antigen-presenting cells (APCs) could improve and broaden the efficacy and durability of vaccine responses. Native SARS-CoV-2 infection stimulates various PRRs, including toll-like receptors (TLRs) and retinoic acid-inducible gene I (RIG-I)-like receptors. We hypothesized that targeting PRRs using molecular adjuvants on nanoparticles (NPs) along with a stabilized spike protein antigen could stimulate broad and efficient immune responses. Adjuvants targeting TLR4 (MPLA), TLR7/8 (R848), TLR9 (CpG), and RIG-I (PUUC) delivered on degradable polymer NPs were combined with the S1 subunit of spike protein and assessed in vitro with isogeneic mixed lymphocyte reactions (isoMLRs). For in vivo studies, the adjuvant-NPs were combined with stabilized spike protein or spike-conjugated NPs and assessed using a two-dose intranasal or intramuscular vaccination model in mice. Combination adjuvant-NPs simultaneously targeting TLR and RIG-I receptors (MPLA+PUUC, CpG+PUUC, and R848+PUUC) differentially induced T cell proliferation and increased proinflammatory cytokine secretion by APCs in vitro. When delivered intranasally, MPLA+PUUC NPs enhanced CD4+CD44+ activated memory T cell responses against spike protein in the lungs while MPLA NPs increased anti-spike IgA in the bronchoalveolar (BAL) fluid and IgG in the blood. Following intramuscular delivery, PUUC NPs induced strong humoral immune responses, characterized by increases in anti-spike IgG in the blood and germinal center B cell populations (GL7+ and BCL6+ B cells) in the draining lymph nodes (dLNs). MPLA+PUUC NPs further boosted spike protein-neutralizing antibody titers and T follicular helper cell populations in the dLNs. These results suggest that protein subunit vaccines with particle-delivered molecular adjuvants targeting TLR4 and RIG-I could lead to robust and unique route-specific adaptive immune responses against SARS-CoV-2.