Natural selection on floral volatiles and other traits can change with snowmelt timing and summer precipitation.

Climate change is disrupting floral traits that mediate mutualistic and antagonistic species interactions. Plastic responses of these traits to multiple shifting conditions may be adaptive, depending on natural selection in new environments. We manipulated snowmelt date over three seasons (3-11 d earlier) in factorial combination with growing-season precipitation (normal, halved, or doubled) to measure plastic responses of volatile emissions and other floral traits in Ipomopsis aggregata. We quantified how precipitation and early snowmelt affected selection on traits by seed predators and pollinators. Within years, floral emissions did not respond to precipitation treatments but shifted with snowmelt treatment depending on the year. Across 3 yr, emissions correlated with both precipitation and snowmelt date. These effects were driven by changes in soil moisture. Selection on several traits changed with earlier snowmelt or reduced precipitation, in some cases driven by predispersal seed predation. Floral trait plasticity was not generally adaptive. Floral volatile emissions shifted in the face of two effects of climate change, and the new environments modulated selection imposed by interacting species. The complexity of the responses underscores the need for more studies of how climate change will affect floral volatiles and other floral traits.

Nonreciprocity in CHIKV and MAYV Vaccine-Elicited Protection.

Chikungunya virus (CHIKV) is a pathogenic arthritogenic alphavirus responsible for large-scale human epidemics for which a vaccine was recently approved for use. Mayaro virus (MAYV) is a related emerging alphavirus with epidemic potential with circulation overlap potential with CHIKV. We previously reported the ability of a non-replicating human adenovirus (AdV)-vectored vaccine expressing the MAYV structural polyprotein to protect against disease in mice following challenge with MAYV, CHIKV and UNAV. Herein, we evaluated mouse immunity and protective efficacy for an AdV-CHIKV full structural polyprotein vaccine in combination with heterologous AdV-MAYV prime/boost regimens versus vaccine coadministration. Heterologous prime/boost regimens skewed immunity toward the prime vaccine antigen but allowed for a boost of cross-neutralizing antibodies, while vaccine co-administration elicited robust, balanced responses capable of boosting. All immunization strategies protected against disease from homologous virus infection, but reciprocal protective immunity differences were revealed upon challenge with heterologous viruses. In vivo passive transfer experiments reproduced the inequity in reciprocal cross-protection after heterologous MAYV challenge. We detected in vitro antibody-dependent enhancement of MAYV replication, suggesting a potential mechanism for the lack of cross-protection. Our findings provide important insights into rational alphavirus vaccine design that may have important implications for the evolving alphavirus vaccine landscape.

Computationally designed mRNA-launched protein nanoparticle vaccines.

Both protein nanoparticle and mRNA vaccines were clinically de-risked during the COVID-19 pandemic1-6. These vaccine modalities have complementary strengths: antigen display on protein nanoparticles can enhance the magnitude, quality, and durability of antibody responses7-10, while mRNA vaccines can be rapidly manufactured11 and elicit antigen-specific CD4 and CD8 T cells12,13. Here we leverage a computationally designed icosahedral protein nanoparticle that was redesigned for optimal secretion from eukaryotic cells14 to develop an mRNA-launched nanoparticle vaccine for SARS-CoV-2. The nanoparticle, which displays 60 copies of a stabilized variant of the Wuhan-Hu-1 Spike receptor binding domain (RBD)15, formed monodisperse, antigenically intact assemblies upon secretion from transfected cells. An mRNA vaccine encoding the secreted RBD nanoparticle elicited 5- to 28-fold higher levels of neutralizing antibodies than an mRNA vaccine encoding membrane-anchored Spike, induced higher levels of CD8 T cells than the same immunogen when delivered as an adjuvanted protein nanoparticle, and protected mice from vaccine-matched and -mismatched SARS-CoV-2 challenge. Our data establish that delivering protein nanoparticle immunogens via mRNA vaccines can combine the benefits of each modality and, more broadly, highlight the utility of computational protein design in genetic immunization strategies.

Hybrid immunity to SARS-CoV-2 arises from serological recall of IgG antibodies distinctly imprinted by infection or vaccination.

We describe the molecular-level composition of polyclonal immunoglobulin G (IgG) anti-spike antibodies from ancestral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, vaccination, or their combination ("hybrid immunity") at monoclonal resolution. Infection primarily triggers S2/N-terminal domain (NTD)-reactive antibodies, whereas vaccination mainly induces anti-receptor-binding domain (RBD) antibodies. This imprint persists after secondary exposures wherein >60% of ensuing hybrid immunity derives from the original IgG pool. Monoclonal constituents of the original IgG pool can increase breadth, affinity, and prevalence upon secondary exposures, as exemplified by the plasma antibody SC27. Following a breakthrough infection, vaccine-induced SC27 gained neutralization breadth and potency against SARS-CoV-2 variants and zoonotic viruses (half-maximal inhibitory concentration [IC50] ∼0.1-1.75 nM) and increased its binding affinity to the protective RBD class 1/4 epitope (dissociation constant [KD] < 5 pM). According to polyclonal escape analysis, SC27-like binding patterns are common in SARS-CoV-2 hybrid immunity. Our findings provide a detailed molecular definition of immunological imprinting and show that vaccination can produce class 1/4 (SC27-like) IgG antibodies circulating in the blood.

A broadly generalizable stabilization strategy for sarbecovirus fusion machinery vaccines.

Evolution of SARS-CoV-2 alters the antigenicity of the immunodominant spike (S) receptor-binding domain and N-terminal domain, undermining the efficacy of vaccines and antibody therapies. To overcome this challenge, we set out to develop a vaccine focusing antibody responses on the highly conserved but metastable S2 subunit, which folds as a spring-loaded fusion machinery. We describe a strategy for prefusion-stabilization and high yield recombinant production of SARS-CoV-2 S2 trimers with native structure and antigenicity. We demonstrate that our design strategy is broadly generalizable to sarbecoviruses, as exemplified with the SARS-CoV-1 (clade 1a) and PRD-0038 (clade 3) S2 subunits. Immunization of mice with a prefusion-stabilized SARS-CoV-2 S2 trimer elicits broadly reactive sarbecovirus antibodies and neutralizing antibody titers of comparable magnitude against Wuhan-Hu-1 and the immune evasive XBB.1.5 variant. Vaccinated mice were protected from weight loss and disease upon challenge with XBB.1.5, providing proof-of-principle for fusion machinery sarbecovirus vaccines.

Non-neutralizing SARS-CoV-2 N-terminal domain antibodies protect mice against severe disease using Fc-mediated effector functions.

Antibodies perform both neutralizing and non-neutralizing effector functions that protect against certain pathogen-induced diseases. A human antibody directed at the SARS-CoV-2 Spike N-terminal domain (NTD), DH1052, was recently shown to be non-neutralizing, yet it protected mice and cynomolgus macaques from severe disease. The mechanisms of NTD non-neutralizing antibody-mediated protection are unknown. Here we show that Fc effector functions mediate NTD non-neutralizing antibody (non-nAb) protection against SARS-CoV-2 MA10 viral challenge in mice. Though non-nAb prophylactic infusion did not suppress infectious viral titers in the lung as potently as neutralizing antibody (nAb) infusion, disease markers including gross lung discoloration were similar in nAb and non-nAb groups. Fc functional knockout substitutions abolished non-nAb protection and increased viral titers in the nAb group. Fc enhancement increased non-nAb protection relative to WT, supporting a positive association between Fc functionality and degree of protection from SARS-CoV-2 infection. For therapeutic administration of antibodies, non-nAb effector functions contributed to virus suppression and lessening of lung discoloration, but the presence of neutralization was required for optimal protection from disease. This study demonstrates that non-nAbs can utilize Fc-mediated mechanisms to lower viral load and prevent lung damage due to coronavirus infection.

COVID-19 point-of-care tests can identify low-antibody individuals: In-depth immunoanalysis of boosting benefits in a healthy cohort.

The recommended COVID-19 booster vaccine uptake is low. At-home lateral flow assay (LFA) antigen tests are widely accepted for detecting infection during the pandemic. Here, we present the feasibility and potential benefits of using LFA-based antibody tests as a means for individuals to detect inadequate immunity and make informed decisions about COVID-19 booster immunization. In a health care provider cohort, we investigated the changes in the breadth and depth of humoral and T cell immune responses following mRNA vaccination and boosting in LFA-positive and LFA-negative antibody groups. We show that negative LFA antibody tests closely reflect the lack of functional humoral immunity observed in a battery of sophisticated immune assays, while positive results do not necessarily reflect adequate immunity. After booster vaccination, both groups gain depth and breadth of systemic antibodies against evolving SARS-CoV-2 and related viruses. Our findings show that LFA-based antibody tests can alert individuals about inadequate immunity against COVID-19, thereby increasing booster shots and promoting herd immunity.

Adjuvant-dependent impact of inactivated SARS-CoV-2 vaccines during heterologous infection by a SARS-related coronavirus.

Whole virus-based inactivated SARS-CoV-2 vaccines adjuvanted with aluminum hydroxide have been critical to the COVID-19 pandemic response. Although these vaccines are protective against homologous coronavirus infection, the emergence of novel variants and the presence of large zoonotic reservoirs harboring novel heterologous coronaviruses provide significant opportunities for vaccine breakthrough, which raises the risk of adverse outcomes like vaccine-associated enhanced respiratory disease. Here, we use a female mouse model of coronavirus disease to evaluate inactivated vaccine performance against either homologous challenge with SARS-CoV-2 or heterologous challenge with a bat-derived coronavirus that represents a potential emerging disease threat. We show that inactivated SARS-CoV-2 vaccines adjuvanted with aluminum hydroxide can cause enhanced respiratory disease during heterologous infection, while use of an alternative adjuvant does not drive disease and promotes heterologous viral clearance. In this work, we highlight the impact of adjuvant selection on inactivated vaccine safety and efficacy against heterologous coronavirus infection.

A Novel Concept for Developing a Precise and Predictable Post and Core Complex Using the Injectable Resin Technique (Part 2).

Post and core systems have long been used in dentistry for the purposes of replacing missing coronal tooth structure, retaining the core, and providing sufficient retention and resistance form to the final restoration to re-establish original form and function. While Part 1 of this two-part article provided a history of post and core systems and materials and discussed empirical data regarding fiber-reinforced post systems, this second part of the article focuses on an alternative approach for developing a fiber-reinforced post and core system using a monoblock system via the injectable resin technique and a recently developed fiber-optic post. The present article explains the concept of a ferrule effect and demonstrates the novel restorative procedure.

Hybrid immunity to SARS-CoV-2 arises from serological recall of IgG antibodies distinctly imprinted by infection or vaccination.

We used plasma IgG proteomics to study the molecular composition and temporal durability of polyclonal IgG antibodies triggered by ancestral SARS-CoV-2 infection, vaccination, or their combination ("hybrid immunity"). Infection, whether primary or post-vaccination, mainly triggered an anti-spike antibody response to the S2 domain, while vaccination predominantly induced anti-RBD antibodies. Immunological imprinting persisted after a secondary (hybrid) exposure, with >60% of the ensuing serological response originating from the initial antibodies generated during the first exposure. We highlight one instance where hybrid immunity arising from breakthrough infection resulted in a marked increase in the breadth and affinity of a highly abundant vaccination-elicited plasma IgG antibody, SC27. With an intrinsic binding affinity surpassing a theoretical maximum (K D < 5 pM), SC27 demonstrated potent neutralization of various SARS-CoV-2 variants and SARS-like zoonotic viruses (IC 50 ∼0.1-1.75 nM) and provided robust protection in vivo . Cryo-EM structural analysis unveiled that SC27 binds to the RBD class 1/4 epitope, with both VH and VL significantly contributing to the binding interface. These findings suggest that exceptionally broad and potent antibodies can be prevalent in plasma and can largely dictate the nature of serological neutralization. HIGHLIGHTS: ▪ Infection and vaccination elicit unique IgG antibody profiles at the molecular level▪ Immunological imprinting varies between infection (S2/NTD) and vaccination (RBD)▪ Hybrid immunity maintains the imprint of first infection or first vaccination▪ Hybrid immune IgG plasma mAbs have superior neutralization potency and breadth.

Pollinator and habitat-mediated selection as potential contributors to ecological speciation in two closely related species.

In ecological speciation, incipient species diverge due to natural selection that is ecologically based. In flowering plants, different pollinators could mediate that selection (pollinator-mediated divergent selection) or other features of the environment that differ between habitats of 2 species could do so (environment-mediated divergent selection). Although these mechanisms are well understood, they have received little rigorous testing, as few studies of divergent selection across sites of closely related species include both floral traits that influence pollination and vegetative traits that influence survival. This study employed common gardens in sites of the 2 parental species and a hybrid site, each containing advanced generation hybrids along with the parental species, to test these forms of ecological speciation in plants of the genus Ipomopsis. A total of 3 vegetative traits (specific leaf area, leaf trichomes, and photosynthetic water-use efficiency) and 5 floral traits (corolla length and width, anther insertion, petal color, and nectar production) were analyzed for impacts on fitness components (survival to flowering and seeds per flower, respectively). These traits exhibited strong clines across the elevational gradient in the hybrid zone, with narrower clines in theory reflecting stronger selection or higher genetic variance. Plants with long corollas and inserted anthers had higher seeds per flower at the Ipomopsis tenuituba site, whereas selection favored the reverse condition at the Ipomopsis aggregata site, a signature of divergent selection. In contrast, no divergent selection due to variation in survival was detected on any vegetative trait. Selection within the hybrid zone most closely resembled selection within the I. aggregata site. Across traits, the strength of divergent selection was not significantly correlated with width of the cline, which was better predicted by evolvability (standardized genetic variance). These results support the role of pollinator-mediated divergent selection in ecological speciation and illustrate the importance of genetic variance in determining divergence across hybrid zones.

A Novel Concept for Developing a Precise and Predictable Post and Core Complex Using the Injectable Resin Technique.

Post systems have long been used in the roots of teeth to retain dental restorations. The primary objectives of current post and core systems are to replace missing coronal tooth structure, retain the core, and provide sufficient retention and resistance form to the final restoration to restore original form and function. Many varieties of user-friendly post and core systems are available today for different endodontic, restorative, and esthetic requirements. The present article provides a history of post and core usage in dentistry, describes various systems and materials for this purpose, and discusses empirical data regarding fiber-reinforced post systems.

Prefusion-stabilized SARS-CoV-2 S2-only antigen provides protection against SARS-CoV-2 challenge.

Ever-evolving SARS-CoV-2 variants of concern (VOCs) have diminished the effectiveness of therapeutic antibodies and vaccines. Developing a coronavirus vaccine that offers a greater breadth of protection against current and future VOCs would eliminate the need to reformulate COVID-19 vaccines. Here, we rationally engineer the sequence-conserved S2 subunit of the SARS-CoV-2 spike protein and characterize the resulting S2-only antigens. Structural studies demonstrate that the introduction of interprotomer disulfide bonds can lock S2 in prefusion trimers, although the apex samples a continuum of conformations between open and closed states. Immunization with prefusion-stabilized S2 constructs elicits broadly neutralizing responses against several sarbecoviruses and protects female BALB/c mice from mouse-adapted SARS-CoV-2 lethal challenge and partially protects female BALB/c mice from mouse-adapted SARS-CoV lethal challenge. These engineering and immunogenicity results should inform the development of next-generation pan-coronavirus therapeutics and vaccines.

Divergent pathogenetic outcomes in BALB/c mice following Omicron subvariant infection.

Following the emergence of B.1.1.529 Omicron, the SARS-CoV-2 virus evolved into a significant number of sublineage variants that possessed numerous mutations throughout the genome, but particularly within the spike glycoprotein (S) gene. For example, the BQ.1.1 and the XBB.1 and XBB.1.5 subvariants contained 34 and 41 mutations in S, respectively. However, these variants elicited largely replication only or mild disease phenotypes in mice. To better model pathogenic outcomes and measure countermeasure performance, we developed mouse adapted versions (BQ.1.1 MA; XBB.1 MA; XBB.1.5 MA) that reflect more pathogenic acute phase pulmonary disease symptoms of SARS-CoV-2, as well as derivative strains expressing nano-luciferase (nLuc) in place of ORF7 (BQ.1.1 nLuc; XBB.1 nLuc; XBB.1.5 nLuc). Amongst the mouse adapted (MA) viruses, a wide range of disease outcomes were observed including mortality, weight loss, lung dysfunction, and tissue viral loads in the lung and nasal turbinates. Intriguingly, XBB.1 MA and XBB.1.5 MA strains, which contained identical mutations throughout except at position F486S/P in S, exhibited divergent disease outcomes in mice (Ao et al., 2023). XBB.1.5 MA infection was associated with significant weight loss and ∼45 % mortality across two independent studies, while XBB.1 MA infected animals suffered from mild weight loss and only 10 % mortality across the same two independent studies. Additionally, the development and use of nanoluciferase expressing strains provided moderate throughput for live virus neutralization assays. The availability of small animal models for the assessment of Omicron VOC disease potential will enable refined capacity to evaluate the efficacy of on market and pre-clinical therapeutics and interventions.

BCG vaccination stimulates integrated organ immunity by feedback of the adaptive immune response to imprint prolonged innate antiviral resistance.

Bacille Calmette-Guérin (BCG) vaccination can confer nonspecific protection against heterologous pathogens. However, the underlying mechanisms remain mysterious. We show that mice vaccinated intravenously with BCG exhibited reduced weight loss and/or improved viral clearance when challenged with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 B.1.351) or PR8 influenza. Protection was first evident between 14 and 21 d post-vaccination and lasted ∼3 months. Notably, BCG induced a biphasic innate response and robust antigen-specific type 1 helper T cell (TH1 cell) responses in the lungs. MyD88 signaling was essential for innate and TH1 cell responses, and protection against SARS-CoV-2. Depletion of CD4+ T cells or interferon (IFN)-γ activity before infection obliterated innate activation and protection. Single-cell and spatial transcriptomics revealed CD4-dependent expression of IFN-stimulated genes in lung myeloid and epithelial cells. Notably, BCG also induced protection against weight loss after mouse-adapted SARS-CoV-2 BA.5, SARS-CoV and SHC014 coronavirus infections. Thus, BCG elicits integrated organ immunity, where CD4+ T cells feed back on tissue myeloid and epithelial cells to imprint prolonged and broad innate antiviral resistance.

Effects of experimental warming on floral scent, display, and rewards in two subalpine herbs.

BACKGROUND AND AIMS: Floral volatiles, visual traits, and rewards mediate attraction and defense in plant-pollinator and plant-herbivore interactions, but these floral traits may be altered by global warming through direct effects of temperature or longer term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators. METHODS: We used open-top chambers that warmed plants in the field +2-3 °C on average (+6-11 °C increase in daily maxima) for 2-4 weeks across 1-3 years at 3 sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: I. aggregata ssp. aggregata, visited mainly by hummingbirds, and I. tenuituba ssp. tenuituba, often visited by hawkmoths. KEY RESULTS: While warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site, and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species, and no effect on nectar concentration, maximum inflorescence height, or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41%, a response that would attract more hummingbird visits, and reduced oviposition by fly seed predators by at least 72%. CONCLUSIONS: Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviors that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming versus temperature at the time of sampling.

Vaccine-mediated protection against Merbecovirus and Sarbecovirus challenge in mice.

The emergence of three highly pathogenic human coronaviruses-severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003, Middle Eastern respiratory syndrome (MERS)-CoV in 2012, and SARS-CoV-2 in 2019-underlines the need to develop broadly active vaccines against the Merbecovirus and Sarbecovirus betacoronavirus subgenera. While SARS-CoV-2 vaccines protect against severe COVID-19, they do not protect against other sarbecoviruses or merbecoviruses. Here, we vaccinate mice with a trivalent sortase-conjugate nanoparticle (scNP) vaccine containing the SARS-CoV-2, RsSHC014, and MERS-CoV receptor-binding domains (RBDs), which elicited live-virus neutralizing antibody responses. The trivalent RBD scNP elicited serum neutralizing antibodies against bat zoonotic Wuhan Institute of Virology-1 (WIV-1)-CoV, SARS-CoV, SARS-CoV-2 BA.1, SARS-CoV-2 XBB.1.5, and MERS-CoV live viruses. The monovalent SARS-CoV-2 RBD scNP vaccine only protected against Sarbecovirus challenge, whereas the trivalent RBD scNP vaccine protected against both Merbecovirus and Sarbecovirus challenge in highly pathogenic and lethal mouse models. This study demonstrates proof of concept for a single pan-sarbecovirus/pan-merbecovirus vaccine that protects against three highly pathogenic human coronaviruses spanning two betacoronavirus subgenera.

A MERS-CoV antibody neutralizes a pre-emerging group 2c bat coronavirus.

The repeated emergence of zoonotic human betacoronaviruses (ß-CoVs) dictates the need for broad therapeutics and conserved epitope targets for countermeasure design. Middle East respiratory syndrome (MERS)-related coronaviruses (CoVs) remain a pressing concern for global health preparedness. Using metagenomic sequence data and CoV reverse genetics, we recovered a full-length wild-type MERS-like BtCoV/li/GD/2014-422 (BtCoV-422) recombinant virus, as well as two reporter viruses, and evaluated their human emergence potential and susceptibility to currently available countermeasures. Similar to MERS-CoV, BtCoV-422 efficiently used human and other mammalian dipeptidyl peptidase protein 4 (DPP4) proteins as entry receptors and an alternative DPP4-independent infection route in the presence of exogenous proteases. BtCoV-422 also replicated efficiently in primary human airway, lung endothelial, and fibroblast cells, although less efficiently than MERS-CoV. However, BtCoV-422 shows minor signs of infection in 288/330 human DPP4 transgenic mice. Several broad CoV antivirals, including nucleoside analogs and 3C-like/Mpro protease inhibitors, demonstrated potent inhibition against BtCoV-422 in vitro. Serum from mice that received a MERS-CoV mRNA vaccine showed reduced neutralizing activity against BtCoV-422. Although most MERS-CoV-neutralizing monoclonal antibodies (mAbs) had limited activity, one anti-MERS receptor binding domain mAb, JC57-11, neutralized BtCoV-422 potently. A cryo-electron microscopy structure of JC57-11 in complex with BtCoV-422 spike protein revealed the mechanism of cross-neutralization involving occlusion of the DPP4 binding site, highlighting its potential as a broadly neutralizing mAb for group 2c CoVs that use DPP4 as a receptor. These studies provide critical insights into MERS-like CoVs and provide candidates for countermeasure development.

Non-neutralizing SARS-CoV-2 N-terminal domain antibodies protect mice against severe disease using Fc-mediated effector functions.

Antibodies perform both neutralizing and non-neutralizing effector functions that protect against certain pathogen-induced diseases. A human antibody directed at the SARS-CoV-2 Spike N-terminal domain (NTD), DH1052, was recently shown to be non-neutralizing yet it protected mice and cynomolgus macaques from severe disease. The mechanisms of this non-neutralizing antibody-mediated protection are unknown. Here we show that Fc effector functions mediate non-neutralizing antibody (non-nAb) protection against SARS-CoV-2 MA10 viral challenge in mice. Though non-nAb infusion did not suppress infectious viral titers in the lung as potently as NTD neutralizing antibody (nAb) infusion, disease markers including gross lung discoloration were similar in nAb and non-nAb groups. Fc functional knockout substitutions abolished non-nAb protection and increased viral titers in the nAb group. Finally, Fc enhancement increased non-nAb protection relative to WT, supporting a positive association between Fc functionality and degree of protection in SARS-CoV-2 infection. This study demonstrates that non-nAbs can utilize Fc-mediated mechanisms to lower viral load and prevent lung damage due to coronavirus infection.

Vaccine-mediated protection against merbecovirus and sarbecovirus challenge in mice.

The emergence of three distinct highly pathogenic human coronaviruses - SARS-CoV in 2003, MERS-CoV in 2012, and SARS-CoV-2 in 2019 - underlines the need to develop broadly active vaccines against the Merbecovirus and Sarbecovirus betacoronavirus subgenera. While SARS-CoV-2 vaccines are highly protective against severe COVID-19 disease, they do not protect against other sarbecoviruses or merbecoviruses. Here, we vaccinate mice with a trivalent sortase-conjugate nanoparticle (scNP) vaccine containing the SARS-CoV-2, RsSHC014, and MERS-CoV receptor binding domains (RBDs), which elicited live-virus neutralizing antibody responses and broad protection. Specifically, a monovalent SARS-CoV-2 RBD scNP vaccine only protected against sarbecovirus challenge, whereas the trivalent RBD scNP vaccine protected against both merbecovirus and sarbecovirus challenge in highly pathogenic and lethal mouse models. Moreover, the trivalent RBD scNP elicited serum neutralizing antibodies against SARS-CoV, MERS-CoV and SARS-CoV-2 BA.1 live viruses. Our findings show that a trivalent RBD nanoparticle vaccine displaying merbecovirus and sarbecovirus immunogens elicits immunity that broadly protects mice against disease. This study demonstrates proof-of-concept for a single pan-betacoronavirus vaccine to protect against three highly pathogenic human coronaviruses spanning two betacoronavirus subgenera.