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.
Keywords: Adaptive immune response; COVID-19 protein subunit vaccine; Combination adjuvant; Intranasal versus intramuscular vaccination; Monophosphoryl lipid A; SARS-CoV-2 spike protein.
【저자키워드】 Adaptive immune response, SARS-CoV-2 spike protein., COVID-19 protein subunit vaccine, Combination adjuvant, Intranasal versus intramuscular vaccination, Monophosphoryl lipid A, 【초록키워드】 COVID-19, SARS-CoV-2, IgG, Efficacy, Immunity, TLR4, SARS-COV-2 infection, Infection, TLR7, B cells, lung, Transmission, TLRs, adjuvants, in vitro, CD4, variants, Toll-like receptor, immune, Population, Spike protein, Polymer, Antigen, B cell, Pattern recognition, BAL, lymphocyte, T cell, anti-Spike IgG, mice, IgA, immune responses, Lungs, SARS-CoV-2 spike protein, Antibody titer, retinoic acid-inducible gene I, RIG-I, Germinal center, Pattern recognition receptors, Subunit vaccine, adjuvant, Toll-like receptors, receptors, receptor, molecular, Adaptive immune response, in vivo, retinoic acid, humoral immune responses, memory T cell, intranasal, Blood, Antibody titers, Anti-spike, protein subunit vaccine, intramuscular, CpG, Monophosphoryl lipid A, PRR, Protein subunit, S1 subunit, antigen-presenting cell, pattern recognition receptor, vaccine responses, Bcl6, lead, helper cell, APCS, Proinflammatory cytokine, antigen-presenting cells, PRRs, reaction, Increases, neutralizing antibody titers, secretion, TLR7/8, MPLA, vaccine availability, DLNs, Protein subunit vaccines, TLR9, memory T, draining lymph nodes, cell population, stabilized spike protein, CD44, intramuscular vaccination, TLR, Cell, spike IgA, bronchoalveolar, PUUC, T cell proliferation, robust, IMPROVE, the S1 subunit, intranasally, characterized, activated, unique, stimulate, responses against, draining lymph node, APC, increases in, follicular, GL7, Native, 【제목키워드】 SARS-CoV-2, Vaccine, immune response, subunit, agonist, ENhance,