A multivalent mRNA monkeypox virus vaccine (BNT166) protects mice and macaques from orthopoxvirus disease.

In response to the 2022 outbreak of mpox driven by unprecedented human-to-human monkeypox virus (MPXV) transmission, we designed BNT166, aiming to create a highly immunogenic, safe, accessible, and scalable next-generation vaccine against MPXV and related orthopoxviruses. To address the multiple viral forms and increase the breadth of immune response, two candidate multivalent mRNA vaccines were evaluated pre-clinically: a quadrivalent vaccine (BNT166a; encoding the MPXV antigens A35, B6, M1, H3) and a trivalent vaccine (BNT166c; without H3). Both candidates induced robust T cell responses and IgG antibodies in mice, including neutralizing antibodies to both MPXV and vaccinia virus. In challenge studies, BNT166a and BNT166c provided complete protection from vaccinia, clade I, and clade IIb MPXV. Furthermore, immunization with BNT166a was 100% effective at preventing death and at suppressing lesions in a lethal clade I MPXV challenge in cynomolgus macaques. These findings support the clinical evaluation of BNT166, now underway (NCT05988203).

Protection from SARS-CoV-2 Delta one year after mRNA-1273 vaccination in rhesus macaques coincides with anamnestic antibody response in the lung.

mRNA-1273 vaccine efficacy against SARS-CoV-2 Delta wanes over time; however, there are limited data on the impact of durability of immune responses on protection. Here, we immunized rhesus macaques and assessed immune responses over 1 year in blood and upper and lower airways. Serum neutralizing titers to Delta were 280 and 34 reciprocal ID50 at weeks 6 (peak) and 48 (challenge), respectively. Antibody-binding titers also decreased in bronchoalveolar lavage (BAL). Four days after Delta challenge, the virus was unculturable in BAL, and subgenomic RNA declined by ∼3-log10 compared with control animals. In nasal swabs, sgRNA was reduced by 1-log10, and the virus remained culturable. Anamnestic antibodies (590-fold increased titer) but not T cell responses were detected in BAL by day 4 post-challenge. mRNA-1273-mediated protection in the lungs is durable but delayed and potentially dependent on anamnestic antibody responses. Rapid and sustained protection in upper and lower airways may eventually require a boost.

mRNA-1273 protects against SARS-CoV-2 beta infection in nonhuman primates.

B.1.351 is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant most resistant to antibody neutralization. We demonstrate how the dose and number of immunizations influence protection. Nonhuman primates received two doses of 30 or 100 µg of Moderna's mRNA-1273 vaccine, a single immunization of 30 µg, or no vaccine. Two doses of 100 µg of mRNA-1273 induced 50% inhibitory reciprocal serum dilution neutralizing antibody titers against live SARS-CoV-2 p.Asp614Gly and B.1.351 of 3,300 and 240, respectively. Higher neutralizing responses against B.1.617.2 were also observed after two doses compared to a single dose. After challenge with B.1.351, there was ~4- to 5-log10 reduction of viral subgenomic RNA and low to undetectable replication in bronchoalveolar lavages in the two-dose vaccine groups, with a 1-log10 reduction in nasal swabs in the 100-µg group. These data establish that a two-dose regimen of mRNA-1273 will be critical for providing upper and lower airway protection against major variants of concern.

Comparative pathogenesis of three Mayaro virus genotypes in the cynomolgus macaque.

Mayaro virus (MAYV), a mosquito-borne alphavirus, is considered an emerging threat to public health with epidemic potential. Phylogenetic studies show the existence of three MAYV genotypes. In this study, we provide a preliminary analysis of the pathogenesis of all three MAYV genotypes in cynomolgus macaques (Macaca facicularis, Mauritian origin). Significant MAYV-specific RNAemia and viremia were detected during acute infection in animals challenged intravenously with the three MAYV genotypes, and strong neutralizing antibody responses were observed. MAYV RNA was detected at high levels in lymphoid tissues, joint muscle and synovia over 1 month after infection, suggesting that this model could serve as a promising tool in studying MAYV-induced chronic arthralgia, which can persist for years. Significant leucopenia was observed across all MAYV genotypes, peaking with RNAemia. Notable differences in the severity of acute RNAemia and composition of cytokine responses were observed among the three MAYV genotypes. Our model showed no outward signs of clinical disease, but several major endpoints for future MAYV pathology and intervention studies are described. Disruptions to normal blood cell counts and cytokine responses were markedly distinct from those observed in macaque models of CHIKV infection, underlining the importance of developing non-human primate models specific to MAYV infection.

Engineered SARS-CoV-2 receptor binding domain improves manufacturability in yeast and immunogenicity in mice.

Global containment of COVID-19 still requires accessible and affordable vaccines for low- and middle-income countries (LMICs). Recently approved vaccines provide needed interventions, albeit at prices that may limit their global access. Subunit vaccines based on recombinant proteins are suited for large-volume microbial manufacturing to yield billions of doses annually, minimizing their manufacturing cost. These types of vaccines are well-established, proven interventions with multiple safe and efficacious commercial examples. Many vaccine candidates of this type for SARS-CoV-2 rely on sequences containing the receptor-binding domain (RBD), which mediates viral entry to cells via ACE2. Here we report an engineered sequence variant of RBD that exhibits high-yield manufacturability, high-affinity binding to ACE2, and enhanced immunogenicity after a single dose in mice compared to the Wuhan-Hu-1 variant used in current vaccines. Antibodies raised against the engineered protein exhibited heterotypic binding to the RBD from two recently reported SARS-CoV-2 variants of concern (501Y.V1/V2). Presentation of the engineered RBD on a designed virus-like particle (VLP) also reduced weight loss in hamsters upon viral challenge.

Reduced SARS-CoV-2 disease outcomes in Syrian hamsters receiving immune sera: Quantitative image analysis in pathologic assessments.

There is a need to standardize pathologic endpoints in animal models of SARS-CoV-2 infection to help benchmark study quality, improve cross-institutional comparison of data, and assess therapeutic efficacy so that potential drugs and vaccines for SARS-CoV-2 can rapidly advance. The Syrian hamster model is a tractable small animal model for COVID-19 that models clinical disease in humans. Using the hamster model, the authors used traditional pathologic assessment with quantitative image analysis to assess disease outcomes in hamsters administered polyclonal immune sera from previously challenged rhesus macaques. The authors then used quantitative image analysis to assess pathologic endpoints across studies performed at different institutions using different tissue processing protocols. The authors detail pathological features of SARS-CoV-2 infection longitudinally and use immunohistochemistry to quantify myeloid cells and T lymphocyte infiltrates during SARS-CoV-2 infection. High-dose immune sera protected hamsters from weight loss and diminished viral replication in tissues and reduced lung lesions. Cumulative pathology scoring correlated with weight loss and was robust in distinguishing IgG efficacy. In formalin-infused lungs, quantitative measurement of percent area affected also correlated with weight loss but was less robust in non-formalin-infused lungs. Longitudinal immunohistochemical assessment of interstitial macrophage infiltrates showed that peak infiltration corresponded to weight loss, yet quantitative assessment of macrophage, neutrophil, and CD3+ T lymphocyte numbers did not distinguish IgG treatment effects. Here, the authors show that quantitative image analysis was a useful adjunct tool for assessing SARS-CoV-2 treatment outcomes in the hamster model.

Distinct Cellular Pathways for Induction of CD4+ T Cell-Dependent Antibody Responses to Antigen Expressed by Intact Bacteria Versus Isolated Soluble Antigen.

Uptake of intact bacteria and soluble Ags by APCs is mediated by phagocytosis and endocytosis or pinocytosis, respectively. Thus, we predicted that injection of clodronate-containing liposomes (CLs), which selectively deplete cells efficient in phagocytosis, would inhibit murine CD4(+) T cell-dependent IgG responses to Ags expressed by intact bacteria but not isolated soluble Ags. Surprisingly, injection of CLs markedly inhibited protein-specific IgG responses to intact, heat-killed Streptococcus pneumoniae, as well as a soluble OVA-polysaccharide conjugate or OVA alone. IgG anti-polysaccharide responses to bacteria and conjugate were also reduced, but more modestly. In both instances, CL-mediated inhibition was associated with a significant reduction in induced germinal centers and CD4(+) germinal center T follicular helper cells. However, CL injection, which largely abrogated the proliferative response of adoptively transferred OVA peptide-specific-transgenic CD4(+) T cells in response to immunization with S. pneumoniae expressing OVA peptide, did not inhibit T cell proliferation in response to OVA-polysaccharide conjugate or OVA. In this regard, monocyte-derived cells, depleted by CLs, internalized S. pneumoniae in vivo, whereas CD11c(low) dendritic cells, unaffected by CL injection, internalized soluble OVA. Ex vivo isolation and coculture of these respective APCs from S. pneumoniae- or OVA-immunized mice with OVA-specific T cells, in the absence of exogenous Ag, demonstrated their selective ability to induce T cell activation. These data suggest that, although distinct APCs initiate CD4(+) T cell activation in response to Ag expressed by intact bacteria versus Ag in soluble form, CL-sensitive cells appear to be necessary for the subsequent IgG responses to both forms of Ag.

Distinct Mechanisms Underlie Boosted Polysaccharide-Specific IgG Responses Following Secondary Challenge with Intact Gram-Negative versus Gram-Positive Extracellular Bacteria.

Priming of mice with intact, heat-killed cells of Gram-negative Neisseria meningitidis, capsular serogroup C (MenC) or Gram-positive group B Streptococcus, capsular type III (GBS-III) bacteria resulted in augmented serum polysaccharide (PS)-specific IgG titers following booster immunization. Induction of memory required CD4(+) T cells during primary immunization. We determined whether PS-specific memory for IgG production was contained within the B cell and/or T cell populations, and whether augmented IgG responses following booster immunization were also dependent on CD4(+) T cells. Adoptive transfer of purified B cells from MenC- or GBS-III-primed, but not naive mice resulted in augmented PS-specific IgG responses following booster immunization. Similar responses were observed when cotransferred CD4(+) T cells were from primed or naive mice. Similarly, primary immunization with unencapsulated MenC or GBS-III, to potentially prime CD4(+) T cells, failed to enhance PS-specific IgG responses following booster immunization with their encapsulated isogenic partners. Furthermore, in contrast to GBS-III, depletion of CD4(+) T cells during secondary immunization with MenC or another Gram-negative bacteria, Acinetobacter baumannii, did not inhibit augmented PS-specific IgG booster responses of mice primed with heat-killed cells. Also, in contrast with GBS-III, booster immunization of MenC-primed mice with isolated MenC-PS, a TI Ag, or a conjugate of MenC-PS and tetanus toxoid elicited an augmented PS-specific IgG response similar to booster immunization with intact MenC. These data demonstrate that memory for augmented PS-specific IgG booster responses to Gram-negative and Gram-positive bacteria is contained solely within the B cell compartment, with a differential requirement for CD4(+) T cells for augmented IgG responses following booster immunization.

Adjuvanted subunit intranasal vaccine prevents SARS-CoV-2 onward transmission in hamsters.

Most COVID-19 vaccine trials have focused on recipient protection, not protection of their contacts, a critical need. As a subunit intranasal COVID-19 vaccine reduced nasopharyngeal virus more than did an intramuscular (IM) vaccine, we hypothesized that this vaccine might reduce onward transmission to others. We vaccinated hamsters with either the IM-administrated Moderna mRNA vaccine twice or one dose of mRNA IM followed by adjuvanted subunit intranasal vaccine. 24 hours after SARS-CoV-2 challenge, these animals were housed with naïve recipients in a contactless chamber that allows airborne transmission. Onward airborne transmission was profoundly blocked: the donor and recipients of the intranasal vaccine-boosted group had lower oral and lung viral loads (VL), which correlated with mucosal ACE2 inhibition activity. These data strongly support the use of the intranasal vaccine as a boost to protect not only the vaccinated person, but also people exposed to the vaccinated person, a key public health goal. Author summary: Natural transmission of SARS-CoV-2 is primarily airborne, through the respiratory mucosal route. However, current licensed COVID-19 vaccines are all intramuscular and induce more systemic than mucosal immunity. Here, we did a head-to-head comparison of COVID-19 booster vaccines on SARS-CoV-2 onward transmission. We found that compared to boosting with a Moderna mRNA systemic vaccine, a nanoparticle intranasal COVID-19 vaccine much more effectively prevents onward airborne transmission to naïve recipient hamsters. The protection was correlated with local mucosal antibody. Thus, a mucosal nanoparticle vaccine should be considered for preventing onward airborne transmission, a key public health necessity that has not been adequately studied.

Synthetic modified vaccinia Ankara vaccines confer cross-reactive and protective immunity against mpox virus.

BACKGROUND: Although the mpox global health emergency caused by mpox virus (MPXV) clade IIb.1 has ended, mpox cases are still reported due to low vaccination coverage and waning immunity. COH04S1 is a clinically evaluated, multiantigen COVID-19 vaccine candidate built on a fully synthetic platform of the highly attenuated modified vaccinia Ankara (MVA) vector, representing the only FDA-approved smallpox/mpox vaccine JYNNEOS. Given the potential threat of MPXV resurgence and need for vaccine alternatives, we aimed to assess the capacity COH04S1 and its synthetic MVA (sMVA) backbone to confer MPXV-specific immunity. METHODS: We evaluated orthopoxvirus-specific and MPXV cross-reactive immune responses in samples collected during a Phase 1 clinical trial of COH04S1 and in non-human primates (NHP) vaccinated with COH04S1 or its sMVA backbone. MPXV cross-reactive immune responses in COH04S1-vaccinated healthy adults were compared to responses measured in healthy subjects vaccinated with JYNNEOS. Additionally, we evaluated the protective efficacy of COH04S1 and sMVA against mpox in mpox-susceptible CAST/EiJ mice. RESULTS: COH04S1-vaccinated individuals develop robust orthopoxvirus-specific humoral and cellular responses, including cross-reactive antibodies to MPXV-specific virion proteins as well as MPXV cross-neutralizing antibodies in 45% of the subjects. In addition, NHP vaccinated with COH04S1 or sMVA show similar MPXV cross-reactive antibody responses. Moreover, MPXV cross-reactive humoral responses elicited by COH04S1 are comparable to those measured in JYNNEOS-vaccinated subjects. Finally, we show that mice vaccinated with COH04S1 or sMVA are protected from lung infection following challenge with MPXV clade IIb.1. CONCLUSIONS: These results demonstrate the capacity of sMVA vaccines to elicit cross-reactive and protective orthopox-specific immunity against MPXV, suggesting that COH04S1 and sMVA could be developed as bivalent or monovalent mpox vaccine alternatives against MPXV.

Mpox is an ilness caused by the mpox virus (MPXV) that belongs to the poxvirus family. The 2022-2023 mpox outbreak highlights the need to develop effective vaccines against MPXV. We have developed a COVID-19 vaccine using as scaffold chemically synthesized genetic material of a highly attenuated and safe poxvirus vector. This scaffold is the same present in a vaccine that has been approved and is given to prevent mpox. Here, we show that healthy human volunteers or monkeys vaccinated with this COVID-19 vaccine generated a robust immune response against MPXV, similar to that generated by the mpox vaccine with the same scaffold. This COVID-19 vaccine is also able to protect mice from infection caused by the MPXV strain isolated from the recent mpox outbreak. This COVID-19 vaccine in a poxvirus scaffold might be an additional tool to curtail mpox outbreaks.

Strong immunogenicity & protection in mice with PlaCCine: A COVID-19 DNA vaccine formulated with a functional polymer.

DNA- based vaccines have demonstrated the potential as a safe and effective modality. PlaCCine, a DNA-based vaccine approach described subsequently relies on a synthetic DNA delivery system and is independent of virus or device. The synthetic functionalized polymer combined with DNA demonstrated stability over 12 months at 4C and for one month at 25C. Transfection efficiency compared to naked DNA increased by 5-15-fold in murine skeletal muscle. Studies of DNA vaccines expressing spike proteins from variants D614G (pVAC15), Delta (pVAC16), or a D614G + Delta combination (pVAC17) were conducted. Mice immunized intramuscular injection (IM) with pVAC15, pVAC16 or pVAC17 formulated with functionalized polymer and adjuvant resulted in induction of spike-specific humoral and cellular responses. Antibody responses were observed after one immunization. And endpoint IgG titers increased to greater than 1x 105 two weeks after the second injection. Neutralizing antibodies as determined by a pseudovirus competition assay were observed following vaccination with pVAC15, pVAC16 or pVAC17. Spike specific T cell immune responses were also observed following vaccination and flow cytometry analysis demonstrated the cellular immune responses included both CD4 and CD8 spike specific T cells. The immune responses in vaccinated mice were maintained for up to 14 months after vaccination. In an immunization and challenge study of K18 hACE2 transgenic mice pVAC15, pVAC16 and pVAC17 induced immune responses lead to decreased lung viral loads by greater than 90 % along with improved clinical score. These findings suggest that PlaCCine DNA vaccines are effective and stable and further development against emerging SARS-CoV-2 variants is warranted.

AZD3152 neutralizes SARS-CoV-2 historical and contemporary variants and is protective in hamsters and well tolerated in adults.

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in variants that can escape neutralization by therapeutic antibodies. Here, we describe AZD3152, a SARS-CoV-2-neutralizing monoclonal antibody designed to provide improved potency and coverage against emerging variants. AZD3152 binds to the back left shoulder of the SARS-CoV-2 spike protein receptor binding domain and prevents interaction with the human angiotensin-converting enzyme 2 receptor. AZD3152 potently neutralized a broad panel of pseudovirus variants, including the currently dominant Omicron variant JN.1 but has reduced potency against XBB subvariants containing F456L. In vitro studies confirmed F456L resistance and additionally identified T415I and K458E as escape mutations. In a Syrian hamster challenge model, prophylactic administration of AZD3152 protected hamsters from weight loss and inflammation-related lung pathologies and reduced lung viral load. In the phase 1 sentinel safety cohort of the ongoing SUPERNOVA study (ClinicalTrials.gov: NCT05648110), a single 600-mg intramuscular injection of AZD5156 (containing 300 mg each of AZD3152 and cilgavimab) was well tolerated in adults through day 91. Observed serum concentrations of AZD3152 through day 91 were similar to those observed with cilgavimab and consistent with predictions for AZD7442, a SARS-CoV-2-neutralizing antibody combination of cilgavimab and tixagevimab, in a population pharmacokinetic model. On the basis of its pharmacokinetic characteristics, AZD3152 is predicted to provide durable protection against symptomatic coronavirus disease 2019 caused by susceptible SARS-CoV-2 variants, such as JN.1, in humans.

Synthetic multiantigen MVA vaccine COH04S1 and variant-specific derivatives protect Syrian hamsters from SARS-CoV-2 Omicron subvariants.

Emerging SARS-CoV-2 Omicron subvariants continue to disrupt COVID-19 vaccine efficacy through multiple immune mechanisms including neutralizing antibody evasion. We developed COH04S1, a synthetic modified vaccinia Ankara vector that co-expresses Wuhan-Hu-1-based spike and nucleocapsid antigens. COH04S1 demonstrated efficacy against ancestral virus and Beta and Delta variants in animal models and was safe and immunogenic in a Phase 1 clinical trial. Here, we report efficacy of COH04S1 and analogous Omicron BA.1- and Beta-specific vaccines to protect Syrian hamsters from Omicron subvariants. Despite eliciting strain-specific antibody responses, all three vaccines protect hamsters from weight loss, lower respiratory tract infection, and lung pathology following challenge with Omicron BA.1 or BA.2.12.1. While the BA.1-specifc vaccine affords consistently improved efficacy compared to COH04S1 to protect against homologous challenge with BA.1, all three vaccines confer similar protection against heterologous challenge with BA.2.12.1. These results demonstrate efficacy of COH04S1 and variant-specific derivatives to confer cross-protective immunity against SARS-CoV-2 Omicron subvariants.

Protection from COVID-19 disease in hamsters vaccinated with subunit SARS-CoV-2 S1 mucosal vaccines adjuvanted with different adjuvants.

Introduction: Adjuvant plays an important role in directing the immune responses induced by vaccines. In previous studies, we have shown that a mucosal SARS-CoV-2 S1 subunit vaccine adjuvanted with a combination of CpG, Poly I:C and IL-15 (named CP15) induced effective mucosal and systemic immunity and conferred nearly sterile protection against SARS-CoV-2 viral replication in macaque models. Methods: In this study, we used a hamster model, which mimics the human scenario and reliably exhibits severe SARS-CoV-2 disease similar to hospitalized patients, to investigate the protection efficacy of the vaccines against COVID-19 disease. We compared the weight loss, viral loads (VLs), and clinical observation scores of three different vaccine regimens. All three regimens consisted of priming/boosting with S1 subunit vaccines, but adjuvanted with alum and/or CP15 administrated by either intramuscular (IM) or intranasal (IN) routes: Group 1 was adjuvanted with alum/alum administrated IM/IM; Group 2 was alum-IM/CP15-IN; and Group 3 was CP15-IM/CP15-IN. Results: After challenge with SARS-CoV-2 WA strain, we found that the alum/CP15 group showed best protection against weight loss, while the CP15 group demonstrated best reduction of oral SARS-CoV-2 VLs, suggesting that the protection profiles were different. Sex differences for VL and clinical scores were observed. Humoral immunity was induced but not correlated with protection. Moreover, S1-specific binding antibody titers against beta, omicron BA.1, and BA.2 variants showed 2.6-, 4.9- and 2.8- fold reduction, respectively, compared to the Wuhan strain. Discussion: Overall, the data suggested that adjuvants in subunit vaccines determine the protection profiles after SARS-CoV-2 infection and that nasal/oral mucosal immunization can protect against systemic COVID-19 disease.

Beta-containing bivalent SARS-CoV-2 protein vaccine elicits durable broad neutralization in macaques and protection in hamsters.

BACKGROUND: Since the beginning of the COVID-19 pandemic, several variants of concern (VOC) have emerged for which there is evidence of an increase in transmissibility, more severe disease, and/or reduced vaccine effectiveness. Effective COVID-19 vaccine strategies are required to achieve broad protective immunity against current and future VOC. METHODS: We conducted immunogenicity and challenge studies in macaques and hamsters using a bivalent recombinant vaccine formulation containing the SARS-CoV-2 prefusion-stabilized Spike trimers of the ancestral D614 and the variant Beta strains with AS03 adjuvant (CoV2 preS dTM-AS03) in a primary immunization setting. RESULTS: We show that a primary immunization with the bivalent CoV2 preS dTM-AS03 elicits broader and durable (1 year) neutralizing antibody responses against VOC including Omicron BA.1 and BA.4/5, and SARS-CoV-1 as compared to the ancestral D614 or Beta variant monovalent vaccines in naïve non-human primates. In addition, the bivalent formulation confers protection against viral challenge with SARS-CoV-2 prototype D614G strain as well as Alpha and Beta variant strains in hamsters. CONCLUSIONS: Our findings demonstrate the potential of a Beta-containing bivalent CoV2 preS dTM-AS03 formulation to provide broad and durable immunogenicity, as well as protection against VOC in naïve populations.

SARS-CoV-2 has changed over time, resulting in different forms of the virus called variants. These variants compromise the protection offered by the COVID-19 vaccines, which trigger an immune response against the viral Spike protein that allows the virus to attach and infect human cells, since their spike proteins are different. Here, we developed and tested a vaccine containing two different Spike proteins, one from the original Wuhan strain and another from the Beta variant. In macaques, the vaccine leads to the production of antibodies able to stop all variants tested from infecting human cells, including Omicron, with stable levels over one year. In hamsters, the vaccine protected against infection with the ancestral virus and the Alpha and Beta variants. Our findings have important implications for vaccine control of existing and future SARS-CoV-2 variants of concern.

Convalescent human IgG, but not IgM, from COVID-19 survivors confers dose-dependent protection against SARS-CoV-2 replication and disease in hamsters.

Introduction: Antibody therapeutic strategies have served an important role during the COVID-19 pandemic, even as their effectiveness has waned with the emergence of escape variants. Here we sought to determine the concentration of convalescent immunoglobulin required to protect against disease from SARS-CoV-2 in a Syrian golden hamster model. Methods: Total IgG and IgM were isolated from plasma of SARS-CoV-2 convalescent donors. Dose titrations of IgG and IgM were infused into hamsters 1 day prior to challenge with SARS-CoV-2 Wuhan-1. Results: The IgM preparation was found to have ~25-fold greater neutralization potency than IgG. IgG infusion protected hamsters from disease in a dose-dependent manner, with detectable serum neutralizing titers correlating with protection. Despite a higher in vitro neutralizing potency, IgM failed to protect against disease when transferred into hamsters. Discussion: This study adds to the growing body of literature that demonstrates neutralizing IgG antibodies are important for protection from SARS-CoV-2 disease, and confirms that polyclonal IgG in sera can be an effective preventative strategy if the neutralizing titers are sufficiently high. In the context of new variants, against which existing vaccines or monoclonal antibodies have reduced efficacy, sera from individuals who have recovered from infection with the emerging variant may potentially remain an efficacious tool.

COH04S1 and beta sequence-modified vaccine protect hamsters from SARS-CoV-2 variants.

COVID-19 vaccine efficacy is threatened by emerging SARS-CoV-2 variants of concern (VOC) with the capacity to evade protective neutralizing antibody responses. We recently developed clinical vaccine candidate COH04S1, a synthetic modified vaccinia Ankara vector (sMVA) co-expressing spike and nucleocapsid antigens based on the Wuhan-Hu-1 reference strain that showed potent efficacy to protect against ancestral SARS-CoV-2 in Syrian hamsters and non-human primates and was safe and immunogenic in healthy volunteers. Here, we demonstrate that intramuscular immunization of Syrian hamsters with COH04S1 and an analogous Beta variant-adapted vaccine candidate (COH04S351) elicits potent cross-reactive antibody responses and protects against weight loss, lower respiratory tract infection, and lung pathology following challenge with major SARS-CoV-2 VOC, including Beta and the highly contagious Delta variant. These results demonstrate efficacy of COH04S1 and a variant-adapted vaccine analog to confer cross-protective immunity against SARS-CoV-2 and its emerging VOC, supporting clinical investigation of these sMVA-based COVID-19 vaccine candidates.

Human-Immune-System (HIS) humanized mouse model (DRAGA: HLA-A2.HLA-DR4.Rag1KO.IL-2RγcKO.NOD) for COVID-19.

We report a Human Immune System (HIS)-humanized mouse model ("DRAGA": HLA-A2.HLA-DR4.Rag1KO.IL-2 RγcKO.NOD) for COVID-19 research. DRAGA mice express transgenically HLA-class I and class-II molecules in the mouse thymus to promote human T cell development and human B cell Ig-class switching. When infused with human hematopoietic stem cells from cord blood reconstitute a functional human immune system, as well as human epi/endothelial cells in lung and upper respiratory airways expressing the human ACE2 receptor for SARS-CoV-2. The DRAGA mice were able to sustain SARS-CoV-2 infection for at least 25 days. Infected mice showed replicating virus in the lungs, deteriorating clinical condition, and human-like lung immunopathology including human lymphocyte infiltrates, microthrombi and pulmonary sequelae. Among the intra-alveolar and peri-bronchiolar lymphocyte infiltrates, human lung-resident (CD103+) CD8+ and CD4+ T cells were sequestered in epithelial (CD326+) lung niches and secreted granzyme B and perforin, suggesting anti-viral cytotoxic activity. Infected mice also mounted human IgG antibody responses to SARS-CoV-2 viral proteins. Hence, HIS-DRAGA mice showed unique advantages as a surrogate in vivo human model for studying SARS-CoV-2 immunopathological mechanisms and testing the safety and efficacy of candidate vaccines and therapeutics.

Synthetic multiantigen MVA vaccine COH04S1 protects against SARS-CoV-2 in Syrian hamsters and non-human primates.

Second-generation COVID-19 vaccines could contribute to establish protective immunity against SARS-CoV-2 and its emerging variants. We developed COH04S1, a synthetic multiantigen modified vaccinia Ankara-based SARS-CoV-2 vaccine that co-expresses spike and nucleocapsid antigens. Here, we report COH04S1 vaccine efficacy in animal models. We demonstrate that intramuscular or intranasal vaccination of Syrian hamsters with COH04S1 induces robust Th1-biased antigen-specific humoral immunity and cross-neutralizing antibodies (NAb) and protects against weight loss, lower respiratory tract infection, and lung injury following intranasal SARS-CoV-2 challenge. Moreover, we demonstrate that single-dose or two-dose vaccination of non-human primates with COH04S1 induces robust antigen-specific binding antibodies, NAb, and Th1-biased T cells, protects against both upper and lower respiratory tract infection following intranasal/intratracheal SARS-CoV-2 challenge, and triggers potent post-challenge anamnestic antiviral responses. These results demonstrate COH04S1-mediated vaccine protection in animal models through different vaccination routes and dose regimens, complementing ongoing investigation of this multiantigen SARS-CoV-2 vaccine in clinical trials.

Rapalogs downmodulate intrinsic immunity and promote cell entry of SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in immunocompromised individuals is associated with prolonged virus shedding and evolution of viral variants. Rapamycin and its analogs (rapalogs, including everolimus, temsirolimus, and ridaforolimus) are FDA approved as mTOR inhibitors for the treatment of human diseases, including cancer and autoimmunity. Rapalog use is commonly associated with an increased susceptibility to infection, which has been traditionally explained by impaired adaptive immunity. Here, we show that exposure to rapalogs increased susceptibility to SARS-CoV-2 infection in tissue culture and in immunologically naive rodents by antagonizing the cell-intrinsic immune response. We identified 1 rapalog (ridaforolimus) that was less potent in this regard and demonstrated that rapalogs promote spike-mediated entry into cells, by triggering the degradation of the antiviral proteins IFITM2 and IFITM3 via an endolysosomal remodeling program called microautophagy. Rapalogs that increased virus entry inhibited mTOR-mediated phosphorylation of the transcription factor TFEB, which facilitated its nuclear translocation and triggered microautophagy. In rodent models of infection, injection of rapamycin prior to and after virus exposure resulted in elevated SARS-CoV-2 replication and exacerbated viral disease, while ridaforolimus had milder effects. Overall, our findings indicate that preexisting use of certain rapalogs may elevate host susceptibility to SARS-CoV-2 infection and disease by activating lysosome-mediated suppression of intrinsic immunity.