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bioRxiv · 10.1101/2022.01.31.478507

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

Atalis, A. M.·Keenum, M. C.·Pandey, B.·Beach, A.·Pradhan, P.·Vantucci, C. E.·Jain, R.·Hosten, J.·Smith, C.·Kramer, L. L.·Jimenez, A. C.·Armenta-Ochoa, M. A.·Frey, D. A.·Roy, K.
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Abstract

Despite recent 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. Although mRNA, pDNA, and viral-vector based vaccines are being administered, no protein subunit-based SARS-CoV-2 vaccine is approved. Molecular adjuvants targeting pathogen-recognition receptors (PRRs) on antigen-presenting cells (APCs) could improve and broaden the efficacy and durability of vaccine responses. Native SARS-CoV-2 infection stimulate various PRRs, including toll-like receptors (TLRs) and retinoic-acid-inducible gene I-like receptors (RIG-I). We hypothesized that targeting the same PRRs using adjuvants on nanoparticles along with a stabilized spike (S) protein antigen could provide broad and efficient immune responses. Formulations targeting TLR4 (MPLA), TLR7/8 (R848), TLR9 (CpG), and RIG-I (PUUC) delivered on degradable polymer-nanoparticles (NPs) were combined with the S1 subunit of S protein and assessed in vitro with isogeneic mixed lymphocyte reactions (iso-MLRs). For in vivo studies, the adjuvanted nanoparticles were combined with stabilized S protein and assessed using intranasal and intramuscular prime-boost vaccination models in mice. Combination NP-adjuvants targeting both TLR and RIG-I (MPLA+PUUC, CpG+PUUC, or R848+PUUC) differentially increased proinflammatory cytokine secretion (IL-1{beta}, IL-12p70, IL-27, IFN-{beta}) by APCs cultured in vitro, and induced differential T cell proliferation. When delivered intranasally, MPLA+PUUC NPs enhanced local CD4+CD44+ activated memory T cell responses while MPLA NPs increased anti-S-protein-specific IgG and IgA in the lung. Following intramuscular delivery, PUUC-carrying NPs induced strong humoral immune responses, characterized by increases in anti-S-protein IgG and neutralizing antibody titers and germinal center B cell populations (GL7+ and BCL6+ B cells). MPLA+PUUC NPs further boosted S-protein-neutralizing antibody titers and T follicular helper cell populations in draining lymph nodes. These results suggest that SARS-CoV-2-mimicking adjuvants and subunit vaccines could lead to robust and unique route-specific adaptive immune responses and may provide additional tools against the pandemic. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=58 SRC="FIGDIR/small/478507v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@7b8174org.highwire.dtl.DTLVardef@701721org.highwire.dtl.DTLVardef@feb860org.highwire.dtl.DTLVardef@fae094_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Atalis, A. M., Keenum, M. C., Pandey, B., Beach, A., Pradhan, P., Vantucci, C. E., Jain, R., Hosten, J., Smith, C., Kramer, L. L., Jimenez, A. C., Armenta-Ochoa, M. A., Frey, D. A., Roy, K.. 2022-02-02. Nanoparticle-delivered TLR4 and RIG-I agonists enhance immune response to SARS-CoV-2 subunit vaccine. https://doi.org/10.1101/2022.01.31.478507

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