The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants stresses the continued need for next-generation vaccines that confer broad protection against coronavirus disease 2019. We developed and evaluated an adjuvanted SARS-CoV-2 spike ferritin nanoparticle (SpFN) vaccine in nonhuman primates. High-dose (50-μg) SpFN vaccine, given twice 28 days apart, induced a T helper cell 1 (T _H 1)–biased CD4 T _H response and elicited neutralizing antibodies against SARS-CoV-2 wild type and variants of concern, as well as against SARS-CoV-1. These potent humoral and cell-mediated immune responses translated into rapid elimination of replicating virus in the upper and lower airways and lung parenchyma of nonhuman primates after high-dose SARS-CoV-2 respiratory challenge. The immune response elicited by SpFN vaccination and resulting efficacy in nonhuman primates support the utility of SpFN as a vaccine candidate for SARS-causing betacoronaviruses.

Significance: The emergence of SARS-CoV-2 variants of concern (VOCs) that reduce the efficacy of current COVID-19 vaccines is a major threat to pandemic control. We evaluate a SARS-CoV-2 spike receptor-binding domain ferritin nanoparticle protein vaccine (RFN) in a nonhuman primate challenge model that addresses the need for a next-generation vaccine with increased pan-SARS breadth of coverage. RFN, adjuvanted with a liposomal-QS21 formulation (ALFQ), elicits humoral and cellular immune responses with excellent breadth and potency against SARS-CoV-2 VOCs and SARS-CoV-1, and protects against high-dose respiratory tract challenge with SARS-CoV-2. Our results support consideration of RFN for vaccine development against multiple concerning members of the Sarbecovirus subgenus of Betacoronaviruses .

The COVID-19 pandemic has had a staggering impact on social, economic, and public health systems worldwide. Vaccine development and mobilization against SARS-CoV-2 (the etiologic agent of COVID-19) has been rapid. However, novel strategies are still necessary to slow the pandemic, and this includes new approaches to vaccine development and/or delivery that will improve vaccination compliance and demonstrate efficacy against emerging variants. Here, we report on the immunogenicity and efficacy of a SARS-CoV-2 vaccine comprising stabilized, pre-fusion spike protein trimers displayed on a ferritin nanoparticle (SpFN) adjuvanted with either conventional aluminum hydroxide or the Army Liposomal Formulation QS-21 (ALFQ) in a cynomolgus macaque COVID-19 model. Vaccination resulted in robust cell-mediated and humoral responses and a significant reduction in lung lesions following SARS-CoV-2 infection. The strength of the immune response suggests that dose sparing through reduced or single dosing in primates may be possible with this vaccine. Overall, the data support further evaluation of SpFN as a SARS-CoV-2 protein-based vaccine candidate with attention to fractional dosing and schedule optimization.

Retinoic acid–inducible gene I (RIG-I) is essential for activating host cell innate immunity to regulate the immune response against many RNA viruses. We previously identified that a small molecule compound, KIN1148, led to the activation of IFN regulatory factor 3 (IRF3) and served to enhance protection against influenza A virus (IAV) A/California/04/2009 infection. We have now determined direct binding of KIN1148 to RIG-I to drive expression of IFN regulatory factor 3 and NF-κB target genes, including specific immunomodulatory cytokines and chemokines. Intriguingly, KIN1148 does not lead to ATPase activity or compete with ATP for binding but activates RIG-I to induce antiviral gene expression programs distinct from type I IFN treatment. When administered in combination with a vaccine against IAV, KIN1148 induces both neutralizing Ab and IAV-specific T cell responses compared with vaccination alone, which induces comparatively poor responses. This robust KIN1148-adjuvanted immune response protects mice from lethal A/California/04/2009 and H5N1 IAV challenge. Importantly, KIN1148 also augments human CD8+ T cell activation. Thus, we have identified a small molecule RIG-I agonist that serves as an effective adjuvant in inducing noncanonical RIG-I activation for induction of innate immune programs that enhance adaptive immune protection of antiviral vaccination.

The hallmark of HIV-1 infection is the rapid dysregulation of immune functions. Recent investigations for biomarkers of such dysregulation in people living with HIV (PLWH) reveal a strong correlation between viral rebound and immune activation with an increased abundance of extracellular vesicles (EVs) enriched with microRNA-155. We propose that the activation of peripheral blood mononuclear cells (PBMCs) leads to an increased miR-155 expression and production of miR-155-rich extracellular vesicles (miR-155-rich EVs), which can exacerbate HIV-1 infection by promoting viral replication. PBMCs were incubated with either HIV-1 (NL4.3Balenv), a TLR-7/8 agonist, or TNF. EVs were harvested from the cell culture supernatant by differential centrifugation, and RT-qPCR quantified miR-155 in cells and derived EVs. The effect of miR-155-rich EVs on replication of HIV-1 in incubated PBMCs was then measured by viral RNA and DNA quantification. HIV-1, TLR7/8 agonist, and TNF each induced the release of miR-155-rich EVs by PBMCs. These miR-155-rich EVs increased viral replication in PBMCs infected in vitro. Infection with HIV-1 and inflammation promote the production of miR-155-rich EVs, enhancing viral replication. Such autocrine loops, therefore, could influence the course of HIV-1 infection by promoting viral replication.

Extracellular vesicles (EVs) and their contents (proteins, lipids, messenger RNA, microRNA, and DNA) are viewed as intercellular signals, cell-transforming agents, and shelters for viruses that allow both diagnostic and therapeutic interventions. EVs circulating in the blood of individuals infected with human immunodeficiency virus (HIV-1) may provide insights into pathogenesis, inflammation, and disease progression. However, distinguishing plasma membrane EVs from exosomes, exomeres, apoptotic bodies, virions, and contaminating proteins remains challenging. We aimed at comparing sucrose and iodixanol density and velocity gradients along with commercial kits as a means of separating EVs from HIV particles and contaminating protein like calprotectin; and thereby evaluating the suitability of current plasma EVs analysis techniques for identifying new biomarkers of HIV-1 immune activation. Multiple analysis have been performed on HIV-1 infected cell lines, plasma from HIV-1 patients, or plasma from HIV-negative individuals spiked with HIV-1. Commercial kits, the differential centrifugation and density or velocity gradients to precipitate and separate HIV, EVs, and proteins such as calprotectin, have been used. EVs, virions, and contaminating proteins were characterized using Western blot, ELISA, RT-PCR, hydrodynamic size measurement, and enzymatic assay. Conversely to iodixanol density or velocity gradient, protein and virions co-sedimented in the same fractions of the sucrose density gradient than AChE-positive EVs. Iodixanol velocity gradient provided the optimal separation of EVs from viruses and free proteins in culture supernatants and plasma samples from a person living with HIV (PLWH) or a control and revealed a new population of large EVs enriched in microRNA miR-155 and mitochondrial DNA. Although EVs and their contents provide helpful information about several key events in HIV-1 pathogenesis, their purification and extensive characterization by velocity gradient must be investigated thoroughly before further use as biomarkers. By revealing a new population of EVs enriched in miR-155 and mitochondrial DNA, this study paves a way to increase our understanding of HIV-1 pathogenesis.