ABSTRACT
Despite the success of currently authorized vaccines for the reduction of severe COVID-19 disease risk, rapidly emerging viral variants continue to drive pandemic waves of infection, resulting in numerous global public health challenges. Progress will depend on future advances in prophylactic vaccine activity, including advancement of candidates capable of generating more potent induction of cross-reactive T cells and durable cross-reactive antibody responses. Here we evaluated an Amphiphile (AMP) adjuvant, AMP-CpG, admixed with SARS-CoV-2 Spike receptor binding domain (RBD) immunogen, as a lymph node-targeted protein subunit vaccine (ELI-005) in mice and non-human primates (NHPs). AMP-mediated targeting of CpG DNA to draining lymph nodes resulted in comprehensive local immune activation characterized by extensive transcriptional reprogramming, inflammatory proteomic milieu, and activation of innate immune cells as key orchestrators of antigen-directed adaptive immunity. Prime-boost immunization with AMP-CpG in mice induced potent and durable T cell responses in multiple anatomical sites critical for prophylactic efficacy and prevention of severe disease. Long-lived memory responses were rapidly expanded upon re-exposure to antigen. In parallel, RBD-specific antibodies were long-lived, and exhibited cross-reactive recognition of variant RBD. AMP-CpG-adjuvanted prime-boost immunization in NHPs was safe and well tolerated, while promoting multi-cytokine-producing circulating T cell responses cross-reactive across variants of concern (VOC). Expansion of RBD-specific germinal center (GC) B cells in lymph nodes correlated to rapid seroconversion with variant-specific neutralizing antibody responses exceeding those measured in convalescent human plasma. These results demonstrate the promise of lymph-node adjuvant-targeting to coordinate innate immunity and generate robust adaptive responses critical for vaccine efficacy.
ABSTRACT
Results from the first gating proficiency panel of intracellular cytokine staining (ICS) highlighted the value of using a consensus gating approach to reduce the variability across laboratories in reported %CD8+ or %CD4+ cytokine-positive cells. Based on the data analysis from the first proficiency panel, harmonization guidelines for a consensus gating protocol were proposed. To validate the recommendations from the first panel and to examine factors that were not included in the first panel, a second ICS gating proficiency panel was organized. All participants analyzed the same set of Flow Cytometry Standard (FCS) files using their own gating protocol. An optional learning module was provided to demonstrate how to apply the previously established gating recommendations and harmonization guidelines to actual ICS data files. Eighty-three participants took part in this proficiency panel. The results from this proficiency panel confirmed the harmonization guidelines from the first panel. These recommendations addressed the (1) placement of the cytokine-positive gate, (2) identification of CD4+ CD8+ double-positive T cells, (3) placement of lymphocyte gate, (4) inclusion of dim cells, (5) gate uniformity, and (6) proper adjustment of the biexponential scaling. In addition, based on the results of this proficiency gating panel, two new recommendations were added to expand the harmonization guidelines: (1) inclusion of dump channel marker to gate all live and dump negative cells and (2) backgating to confirm the correct placement of gates across all populations. © 2020 International Society for Advancement of Cytometry.
Subject(s)
Cytokines , Neoplasms , Flow Cytometry , Humans , Immunotherapy , Neoplasms/therapy , Reproducibility of Results , Staining and LabelingABSTRACT
The profound consequences of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mandate urgent development of effective vaccines. Here, we evaluated an Amphiphile (AMP) vaccine adjuvant, AMP-CpG, composed of diacyl lipid-modified CpG, admixed with the SARS-CoV-2 Spike-2 receptor binding domain protein as a candidate vaccine (ELI-005) in mice. AMP modification efficiently delivers CpG to lymph nodes, where innate and adaptive immune responses are generated. Compared to alum, immunization with AMP-CpG induced >25-fold higher antigen-specific T cells that produced multiple T helper 1 (TH1) cytokines and trafficked into lung parenchyma. Antibody responses favored TH1 isotypes (IgG2c and IgG3) and potently neutralized Spike-2-ACE2 receptor binding, with titers 265-fold higher than natural convalescent patient COVID-19 responses; T cell and antibody responses were maintained despite 10-fold dose reduction in Spike antigen. Both cellular and humoral immune responses were preserved in aged mice. These advantages merit clinical translation to SARS-CoV-2 and other protein subunit vaccines.