Safety and Immunogenicity of an Andes Virus DNA Vaccine by Needle-Free Injection: A Randomized, Controlled Phase 1 Study.

BACKGROUND: Andes virus (ANDV), a rodent-borne hantavirus, causes hantavirus pulmonary syndrome (HPS). The safety and immunogenicity of a novel ANDV DNA vaccine was evaluated. METHODS: Phase 1, double-blind, dose-escalation trial randomly assigned 48 healthy adults to placebo or ANDV DNA vaccine delivered via needle-free jet injection. Cohorts 1 and 2 received 2 mg of DNA or placebo in a 3-dose (days 1, 29, 169) or 4-dose (days 1, 29, 57, 169) schedule, respectively. Cohorts 3 and 4 received 4 mg of DNA or placebo in the 3-dose and 4-dose schedule, respectively. Subjects were monitored for safety and neutralizing antibodies by pseudovirion neutralization assay (PsVNA50) and plaque reduction neutralization test (PRNT50). RESULTS: While 98% and 65% of subjects had at least 1 local or systemic solicited adverse event (AE), respectively, most AEs were mild or moderate; no related serious AEs were detected. Cohorts 2, 3, and 4 had higher seroconversion rates than cohort 1 and seropositivity of at least 80% by day 197, sustained through day 337. PsVNA50 geometric mean titers were highest for cohort 4 on and after day 197. CONCLUSIONS: This first-in-human candidate HPS vaccine trial demonstrated that an ANDV DNA vaccine was safe and induced a robust, durable immune response. Clinical Trials Registration. NCT03682107.

Safety and Immunogenicity of Accelerated Heterologous Two-dose Ebola Vaccine Regimens in Adults With and Without HIV in Africa.

BACKGROUND: Shorter prophylactic vaccine schedules may offer more rapid protection against Ebola in resource-limited settings. METHODS: This randomized, observer-blind, placebo-controlled, phase 2 trial conducted in five sub-Saharan African countries included people without HIV (PWOH, n = 249) and people living with HIV (PLWH, n = 250). Adult participants received one of two accelerated Ebola vaccine regimens (MVA-BN-Filo, Ad26.ZEBOV administered 14 days apart [n = 79] or Ad26.ZEBOV, MVA-BN-Filo administered 28 days apart [n = 322]) or saline/placebo (n = 98). The primary endpoints were safety (adverse events [AEs]) and immunogenicity (Ebola virus [EBOV] glycoprotein-specific binding antibody responses). Binding antibody responders were defined as participants with a > 2.5-fold increase from baseline or the lower limit of quantification if negative at baseline. RESULTS: The mean age was 33.4 years, 52% of participants were female, and among PLWH, the median (interquartile range) CD4+ cell count was 560.0 (418.0-752.0) cells/µL. AEs were generally mild/moderate with no vaccine-related serious AEs or remarkable safety profile differences by HIV status. At 21 days post-dose 2, EBOV glycoprotein-specific binding antibody response rates in vaccine recipients were 99% for the 14-day regimen (geometric mean concentrations [GMCs]: 5168 enzyme-linked immunosorbent assay units (EU)/mL in PWOH; 2509 EU/mL in PLWH), and 98% for the 28-day regimen (GMCs: 6037 EU/mL in PWOH; 2939 EU/mL in PLWH). At 12 months post-dose 2, GMCs in PWOH and PLWH were 635 and 514 EU/mL, respectively, for the 14-day regimen and 331 and 360 EU/mL, respectively, for the 28-day regimen. CONCLUSIONS: Accelerated 14- and 28-day Ebola vaccine regimens were safe and immunogenic in PWOH and PLWH in Africa. TRIAL REGISTRATION: NCT02598388.

A Nucleic Acid-Based Orthopoxvirus Vaccine Targeting the Vaccinia Virus L1, A27, B5, and A33 Proteins Protects Rabbits against Lethal Rabbitpox Virus Aerosol Challenge.

In the age of COVID, nucleic acid vaccines have garnered much attention, at least in part, because of the simplicity of construction, production, and flexibility to adjust and adapt to an evolving outbreak. Orthopoxviruses remain a threat on multiple fronts, especially as emerging zoonoses. In response, we developed a DNA vaccine, termed 4pox, that protected nonhuman primates against monkeypox virus (MPXV)-induced severe disease. Here, we examined the protective efficacy of the 4pox DNA vaccine delivered by intramuscular (i.m.) electroporation (EP) in rabbits challenged with aerosolized rabbitpox virus (RPXV), a model that recapitulates the respiratory route of exposure and low dose associated with natural smallpox exposure in humans. We found that 4pox-vaccinated rabbits developed immunogen-specific antibodies, including neutralizing antibodies, and did not develop any clinical disease, indicating protection against aerosolized RPXV. In contrast, unvaccinated animals developed significant signs of disease, including lesions, and were euthanized. These findings demonstrate that an unformulated, nonadjuvanted DNA vaccine delivered i.m. can protect against an aerosol exposure. IMPORTANCE The eradication of smallpox and subsequent cessation of vaccination have left a majority of the population susceptible to variola virus or other emerging poxviruses. This is exemplified by human monkeypox, as evidenced by the increase in reported endemic and imported cases over the past decades. Therefore, a malleable vaccine technology that can be mass produced and does not require complex conditions for distribution and storage is sought. Herein, we show that a DNA vaccine, in the absence of a specialized formulation or adjuvant, can protect against a lethal aerosol insult of rabbitpox virus.

Human convalescent plasma protects K18-hACE2 mice against severe respiratory disease.

SARS-CoV-2 is the causative agent of COVID-19 and human infections have resulted in a global health emergency. Small animal models that reproduce key elements of SARS-CoV-2 human infections are needed to rigorously screen candidate drugs to mitigate severe disease and prevent the spread of SARS-CoV-2. We and others have reported that transgenic mice expressing the human angiotensin-converting enzyme 2 (hACE2) viral receptor under the control of the Keratin 18 (K18) promoter develop severe and lethal respiratory disease subsequent to SARS-CoV-2 intranasal challenge. Here we report that some infected mice that survive challenge have residual pulmonary damages and persistent brain infection on day 28 post-infection despite the presence of anti-SARS-COV-2 neutralizing antibodies. Because of the hypersensitivity of K18-hACE2 mice to SARS-CoV-2 and the propensity of virus to infect the brain, we sought to determine if anti-infective biologics could protect against disease in this model system. We demonstrate that anti-SARS-CoV-2 human convalescent plasma protects K18-hACE2 against severe disease. All control mice succumbed to disease by day 7; however, all treated mice survived infection without observable signs of disease. In marked contrast to control mice, viral antigen and lesions were reduced or absent from lungs and absent in brains of antibody-treated mice. Our findings support the use of K18-hACE2 mice for protective efficacy studies of anti-SARS-CoV-2 medical countermeasures (MCMs). They also support the use of this system to study SARS-CoV-2 persistence and host recovery.

Disruption of Adaptive Immunity Enhances Disease in SARS-CoV-2-Infected Syrian Hamsters.

Animal models recapitulating human COVID-19 disease, especially severe disease, are urgently needed to understand pathogenesis and to evaluate candidate vaccines and therapeutics. Here, we develop novel severe-disease animal models for COVID-19 involving disruption of adaptive immunity in Syrian hamsters. Cyclophosphamide (CyP) immunosuppressed or RAG2 knockout (KO) hamsters were exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the respiratory route. Both the CyP-treated and RAG2 KO hamsters developed clinical signs of disease that were more severe than those in immunocompetent hamsters, notably weight loss, viral loads, and fatality (RAG2 KO only). Disease was prolonged in transiently immunosuppressed hamsters and was uniformly lethal in RAG2 KO hamsters. We evaluated the protective efficacy of a neutralizing monoclonal antibody and found that pretreatment, even in immunosuppressed animals, limited infection. Our results suggest that functional B and/or T cells are not only important for the clearance of SARS-CoV-2 but also play an early role in protection from acute disease.IMPORTANCE Syrian hamsters are in use as a model of disease caused by SARS-CoV-2. Pathology is pronounced in the upper and lower respiratory tract, and disease signs and endpoints include weight loss and viral RNA and/or infectious virus in swabs and organs (e.g., lungs). However, a high dose of virus is needed to produce disease, and the disease resolves rapidly. Here, we demonstrate that immunosuppressed hamsters are susceptible to low doses of virus and develop more severe and prolonged disease. We demonstrate the efficacy of a novel neutralizing monoclonal antibody using the cyclophosphamide transient suppression model. Furthermore, we demonstrate that RAG2 knockout hamsters develop severe/fatal disease when exposed to SARS-CoV-2. These immunosuppressed hamster models provide researchers with new tools for evaluating therapies and vaccines and understanding COVID-19 pathogenesis.

Randomized, Blinded, Dose-Ranging Trial of an Ebola Virus Glycoprotein Nanoparticle Vaccine With Matrix-M Adjuvant in Healthy Adults.

BACKGROUND: Ebola virus (EBOV) epidemics pose a major public health risk. There currently is no licensed human vaccine against EBOV. The safety and immunogenicity of a recombinant EBOV glycoprotein (GP) nanoparticle vaccine formulated with or without Matrix-M adjuvant were evaluated to support vaccine development. METHODS: A phase 1, placebo-controlled, dose-escalation trial was conducted in 230 healthy adults to evaluate 4 EBOV GP antigen doses as single- or 2-dose regimens with or without adjuvant. Safety and immunogenicity were assessed through 1-year postdosing. RESULTS: All EBOV GP vaccine formulations were well tolerated. Receipt of 2 doses of EBOV GP with adjuvant showed a rapid increase in anti-EBOV GP immunoglobulin G titers with peak titers observed on Day 35 representing 498- to 754-fold increases from baseline; no evidence of an antigen dose response was observed. Serum EBOV-neutralizing and binding antibodies using wild-type Zaire EBOV (ZEBOV) or pseudovirion assays were 3- to 9-fold higher among recipients of 2-dose EBOV GP with adjuvant, compared with placebo on Day 35, which persisted through 1 year. CONCLUSIONS: Ebola virus GP vaccine with Matrix-M adjuvant is well tolerated and elicits a robust and persistent immune response. These data suggest that further development of this candidate vaccine for prevention of EBOV disease is warranted.

A Recombinant Vesicular Stomatitis Virus Ebola Vaccine.

BACKGROUND: The worst Ebola virus disease (EVD) outbreak in history has resulted in more than 28,000 cases and 11,000 deaths. We present the final results of two phase 1 trials of an attenuated, replication-competent, recombinant vesicular stomatitis virus (rVSV)-based vaccine candidate designed to prevent EVD. METHODS: We conducted two phase 1, placebo-controlled, double-blind, dose-escalation trials of an rVSV-based vaccine candidate expressing the glycoprotein of a Zaire strain of Ebola virus (ZEBOV). A total of 39 adults at each site (78 participants in all) were consecutively enrolled into groups of 13. At each site, volunteers received one of three doses of the rVSV-ZEBOV vaccine (3 million plaque-forming units [PFU], 20 million PFU, or 100 million PFU) or placebo. Volunteers at one of the sites received a second dose at day 28. Safety and immunogenicity were assessed. RESULTS: The most common adverse events were injection-site pain, fatigue, myalgia, and headache. Transient rVSV viremia was noted in all the vaccine recipients after dose 1. The rates of adverse events and viremia were lower after the second dose than after the first dose. By day 28, all the vaccine recipients had seroconversion as assessed by an enzyme-linked immunosorbent assay (ELISA) against the glycoprotein of the ZEBOV-Kikwit strain. At day 28, geometric mean titers of antibodies against ZEBOV glycoprotein were higher in the groups that received 20 million PFU or 100 million PFU than in the group that received 3 million PFU, as assessed by ELISA and by pseudovirion neutralization assay. A second dose at 28 days after dose 1 significantly increased antibody titers at day 56, but the effect was diminished at 6 months. CONCLUSIONS: This Ebola vaccine candidate elicited anti-Ebola antibody responses. After vaccination, rVSV viremia occurred frequently but was transient. These results support further evaluation of the vaccine dose of 20 million PFU for preexposure prophylaxis and suggest that a second dose may boost antibody responses. (Funded by the National Institutes of Health and others; rVSV∆G-ZEBOV-GP ClinicalTrials.gov numbers, NCT02269423 and NCT02280408 .).

Characterization of Ebola convalescent plasma donor immune response and psoralen treated plasma in the United States.

BACKGROUND: In 2014, passive immunization by transfusion of Ebola convalescent plasma (ECP) was considered for treating patients with acute Ebola virus disease (EVD). Early Ebola virus (EBOV) seroconversion confers a survival advantage in natural infection, hence transfusion of ECP plasma with high levels of neutralizing EBOV antibodies is a potential passive immune therapy. Techniques to reduce the risk of other transfusion-transmitted infections (TTIs) are warranted as recent ECP survivors are ineligible as routine blood donors. As part of an ongoing clinical trial to evaluate the safety and effectiveness of ECP, the impact of amotosalen/UVA pathogen reduction technology (PRT) on EBOV antibody characteristics was examined. STUDY DESIGN AND METHODS: Serum and plasma samples were collected from EVD-recovered subjects at multiple timepoints and evaluated by ELISA for antibodies to recombinant EBOV glycoprotein (GP) and irradiated whole EBOV antigen, as well as for EBOV microneutralization, classic plaque reduction neutralization test (PRNT) and EBOV pseudovirion neutralization assay (PsVNA) activity. RESULTS: Six subjects donated 40 individual ECP units. Substantial antibody titers and neutralizing activity results were demonstrated but were generally lower for the ACD plasma samples compared to the serum samples. Anti-EBOV titers by all assays remained essentially unchanged after PRT. CONCLUSION: Treatment of ECP with PRT to reduce the risk of TTI did not significantly reduce EBOV IgG antibody titers or neutralizing activity. Although ECP was used in the treatment of repatriated patients, no PRT units from this study were transfused to EVD patients. This inventory of PRT-treated ECP is currently available for future clinical evaluation.

Phase 1 Trials of rVSV Ebola Vaccine in Africa and Europe.

BACKGROUND: The replication-competent recombinant vesicular stomatitis virus (rVSV)-based vaccine expressing a Zaire ebolavirus (ZEBOV) glycoprotein was selected for rapid safety and immunogenicity testing before its use in West Africa. METHODS: We performed three open-label, dose-escalation phase 1 trials and one randomized, double-blind, controlled phase 1 trial to assess the safety, side-effect profile, and immunogenicity of rVSV-ZEBOV at various doses in 158 healthy adults in Europe and Africa. All participants were injected with doses of vaccine ranging from 300,000 to 50 million plaque-forming units (PFU) or placebo. RESULTS: No serious vaccine-related adverse events were reported. Mild-to-moderate early-onset reactogenicity was frequent but transient (median, 1 day). Fever was observed in up to 30% of vaccinees. Vaccine viremia was detected within 3 days in 123 of the 130 participants (95%) receiving 3 million PFU or more; rVSV was not detected in saliva or urine. In the second week after injection, arthritis affecting one to four joints developed in 11 of 51 participants (22%) in Geneva, with pain lasting a median of 8 days (interquartile range, 4 to 87); 2 self-limited cases occurred in 60 participants (3%) in Hamburg, Germany, and Kilifi, Kenya. The virus was identified in one synovial-fluid aspirate and in skin vesicles of 2 other vaccinees, showing peripheral viral replication in the second week after immunization. ZEBOV-glycoprotein-specific antibody responses were detected in all the participants, with similar glycoprotein-binding antibody titers but significantly higher neutralizing antibody titers at higher doses. Glycoprotein-binding antibody titers were sustained through 180 days in all participants. CONCLUSIONS: In these studies, rVSV-ZEBOV was reactogenic but immunogenic after a single dose and warrants further evaluation for safety and efficacy. (Funded by the Wellcome Trust and others; ClinicalTrials.gov numbers, NCT02283099, NCT02287480, and NCT02296983; Pan African Clinical Trials Registry number, PACTR201411000919191.).

Fully Human Immunoglobulin G From Transchromosomic Bovines Treats Nonhuman Primates Infected With Ebola Virus Makona Isolate.

Transchromosomic bovines (Tc-bovines) adaptively produce fully human polyclonal immunoglobulin (Ig)G antibodies after exposure to immunogenic antigen(s). The National Interagency Confederation for Biological Research and collaborators rapidly produced and then evaluated anti-Ebola virus IgG immunoglobulins (collectively termed SAB-139) purified from Tc-bovine plasma after sequential hyperimmunization with an Ebola virus Makona isolate glycoprotein nanoparticle vaccine. SAB-139 was characterized by several in vitro production, research, and clinical level assays using wild-type Makona-C05 or recombinant virus/antigens from different Ebola virus variants. SAB-139 potently activates natural killer cells, monocytes, and peripheral blood mononuclear cells and has high-binding avidity demonstrated by surface plasmon resonance. SAB-139 has similar concentrations of galactose-α-1,3-galactose carbohydrates compared with human-derived intravenous Ig, and the IgG1 subclass antibody is predominant. All rhesus macaques infected with Ebola virus/H.sapiens-tc/GIN/2014/Makona-C05 and treated with sufficient SAB-139 at 1 day (n = 6) or 3 days (n = 6) postinfection survived versus 0% of controls. This study demonstrates that Tc-bovines can produce pathogen-specific human Ig to prevent and/or treat patients when an emerging infectious disease either threatens to or becomes an epidemic.

Innate immune responses elicited by Sin Nombre virus or type I IFN agonists protect hamsters from lethal Andes virus infections.

Sin Nombre virus (SNV) and Andes virus (ANDV) cause hantavirus pulmonary syndrome (HPS) in humans. Both SNV and ANDV infect Syrian hamsters, but only ANDV causes lethal disease. A co-infection study was performed to determine which virus, SNV or ANDV, would dominate the survival outcome in hamsters. Infection of hamsters with SNV 1 day before ANDV challenge did not result in disease characteristic of the latter virus, and all animals survived challenge. Control animals infected solely with ANDV all succumbed by day 14. In contrast, when viruses were injected at the same site concurrently, all hamsters succumbed to HPS disease. Hantaviruses are segmented viruses; therefore we investigated which segment might be responsible for the protective phenotype of SNV by using two SNV/ANDV reassortant viruses, both with reciprocal M-segments from the other virus (denoted ASA and SAS). Both reassortants asymptomatically infect hamsters, similar to SNV. However, unlike SNV, 1 day prior preinfection with the reassortant virus did not prevent ANDV lethality. The ASA reassortant virus, but not SAS, protected hamsters from lethal ANDV infection when administered 3 days prior to ANDV challenge. Similar to SNV preinfection, the potent innate immune stimulator poly I:C administered to hamsters 1 day before ANDV challenge prevented lethal ANDV disease. Combined, these results suggest that the difference in pathogenicity of SNV and ANDV in hamsters involves differences in early host-pathogen interactions and resultant anti-viral immune responses of both the innate and adaptive immune system.

Safety and immunogenicity of rVSVΔG-ZEBOV-GP Ebola vaccine in adults and children in Lambaréné, Gabon: A phase I randomised trial.

BACKGROUND: The rVSVΔG-ZEBOV-GP vaccine prevented Ebola virus disease when used at 2 × 107 plaque-forming units (PFU) in a trial in Guinea. This study provides further safety and immunogenicity data. METHODS AND FINDINGS: A randomised, open-label phase I trial in Lambaréné, Gabon, studied 5 single intramuscular vaccine doses of 3 × 103, 3 × 104, 3 × 105, 3 × 106, or 2 × 107 PFU in 115 adults and a dose of 2 × 107 PFU in 20 adolescents and 20 children. The primary objective was safety and tolerability 28 days post-injection. Immunogenicity, viraemia, and shedding post-vaccination were evaluated as secondary objectives. In adults, mild-to-moderate adverse events were frequent, but there were no serious or severe adverse events related to vaccination. Before vaccination, Zaire Ebola virus (ZEBOV)-glycoprotein (GP)-specific and ZEBOV antibodies were detected in 11% and 27% of adults, respectively. In adults, 74%-100% of individuals who received a dose 3 × 104, 3 × 105, 3 × 106, or 2 × 107 PFU had a ≥4.0-fold increase in geometric mean titres (GMTs) of ZEBOV-GP-specific antibodies at day 28, reaching GMTs of 489 (95% CI: 264-908), 556 (95% CI: 280-1,101), 1,245 (95% CI: 899-1,724), and 1,503 (95% CI: 931-2,426), respectively. Twenty-two percent of adults had a ≥4-fold increase of ZEBOV antibodies, with GMTs at day 28 of 1,015 (647-1,591), 1,887 (1,154-3,085), 1,445 (1,013-2,062), and 3,958 (2,249-6,967) for the same doses, respectively. These antibodies persisted up to day 180 for doses ≥3 × 105 PFU. Adults with antibodies before vaccination had higher GMTs throughout. Neutralising antibodies were detected in more than 50% of participants at doses ≥3 × 105 PFU. As in adults, no serious or severe adverse events related to vaccine occurred in adolescents or children. At day 2, vaccine RNA titres were higher for adolescents and children than adults. At day 7, 78% of adolescents and 35% of children had recombinant vesicular stomatitis virus RNA detectable in saliva. The vaccine induced high GMTs of ZEBOV-GP-specific antibodies at day 28 in adolescents, 1,428 (95% CI: 1,025-1,989), and children, 1,620 (95% CI: 806-3,259), and in both groups antibody titres increased up to day 180. The absence of a control group, lack of stratification for baseline antibody status, and imbalances in male/female ratio are the main limitations of this study. CONCLUSIONS: Our data confirm the acceptable safety and immunogenicity profile of the 2 × 107 PFU dose in adults and support consideration of lower doses for paediatric populations and those who request boosting. TRIAL REGISTRATION: Pan African Clinical Trials Registry PACTR201411000919191.

Glycoprotein-Specific Antibodies Produced by DNA Vaccination Protect Guinea Pigs from Lethal Argentine and Venezuelan Hemorrhagic Fever.

UNLABELLED: Several members of the Arenaviridae can cause acute febrile diseases in humans, often resulting in lethality. The use of convalescent-phase human plasma is an effective treatment in humans infected with arenaviruses, particularly species found in South America. Despite this, little work has focused on developing potent and defined immunotherapeutics against arenaviruses. In the present study, we produced arenavirus neutralizing antibodies by DNA vaccination of rabbits with plasmids encoding the full-length glycoprotein precursors of Junín virus (JUNV), Machupo virus (MACV), and Guanarito virus (GTOV). Geometric mean neutralizing antibody titers, as measured by the 50% plaque reduction neutralization test (PRNT(50)), exceeded 5,000 against homologous viruses. Antisera against each targeted virus exhibited limited cross-species binding and, to a lesser extent, cross-neutralization. Anti-JUNV glycoprotein rabbit antiserum protected Hartley guinea pigs from lethal intraperitoneal infection with JUNV strain Romero when the antiserum was administered 2 days after challenge and provided some protection (∼30%) when administered 4 days after challenge. Treatment starting on day 6 did not protect animals. We further formulated an IgG antibody cocktail by combining anti-JUNV, -MACV, and -GTOV antibodies produced in DNA-vaccinated rabbits. This cocktail protected 100% of guinea pigs against JUNV and GTOV lethal disease. We then expanded on this cocktail approach by simultaneously vaccinating rabbits with a combination of plasmids encoding glycoproteins from JUNV, MACV, GTOV, and Sabia virus (SABV). Sera collected from rabbits vaccinated with the combination vaccine neutralized all four targets. These findings support the concept of using a DNA vaccine approach to generate a potent pan-arenavirus immunotherapeutic. IMPORTANCE: Arenaviruses are an important family of emerging viruses. In infected humans, convalescent-phase plasma containing neutralizing antibodies can mitigate the severity of disease caused by arenaviruses, particularly species found in South America. Because of variations in potency of the human-derived product, limited availability, and safety concerns, this treatment option has essentially been abandoned. Accordingly, despite this approach being an effective postinfection treatment option, research on novel approaches to produce potent polyclonal antibody-based therapies have been deficient. Here we show that DNA-based vaccine technology can be used to make potently neutralizing antibodies in rabbits that exclusively target the glycoproteins of several human-pathogenic arenaviruses found in South America, including JUNV, MACV, GTOV, and SABV. These antibodies protected guinea pigs from lethal disease when given post-virus challenge. We also generated a purified antibody cocktail with antibodies targeting three arenaviruses and demonstrated protective efficacy against all three targets. Our findings demonstrate that use of the DNA vaccine technology could be used to produce candidate antiarenavirus neutralizing antibody-based products.

Depletion of Alveolar Macrophages Does Not Prevent Hantavirus Disease Pathogenesis in Golden Syrian Hamsters.

UNLABELLED: Andes virus (ANDV) is associated with a lethal vascular leak syndrome in humans termed hantavirus pulmonary syndrome (HPS). The mechanism for the massive vascular leakage associated with HPS is poorly understood; however, dysregulation of components of the immune response is often suggested as a possible cause. Alveolar macrophages are found in the alveoli of the lung and represent the first line of defense to many airborne pathogens. To determine whether alveolar macrophages play a role in HPS pathogenesis, alveolar macrophages were depleted in an adult rodent model of HPS that closely resembles human HPS. Syrian hamsters were treated, intratracheally, with clodronate-encapsulated liposomes or control liposomes and were then challenged with ANDV. Treatment with clodronate-encapsulated liposomes resulted in significant reduction in alveolar macrophages, but depletion did not prevent pathogenesis or prolong disease. Depletion also did not significantly reduce the amount of virus in the lung of ANDV-infected hamsters but altered neutrophil recruitment, MIP-1α and MIP-2 chemokine expression, and vascular endothelial growth factor (VEGF) levels in hamster bronchoalveolar lavage (BAL) fluid early after intranasal challenge. These data demonstrate that alveolar macrophages may play a limited protective role early after exposure to aerosolized ANDV but do not directly contribute to hantavirus disease pathogenesis in the hamster model of HPS. IMPORTANCE: Hantaviruses continue to cause disease worldwide for which there are no FDA-licensed vaccines, effective postexposure prophylactics, or therapeutics. Much of this can be attributed to a poor understanding of the mechanism of hantavirus disease pathogenesis. Hantavirus disease has long been considered an immune-mediated disease; however, by directly manipulating the Syrian hamster model, we continue to eliminate individual immune cell types. As the most numerous immune cells present in the respiratory tract, alveolar macrophages are poised to defend against hantavirus infection, but those antiviral responses may also contribute to hantavirus disease. Here, we demonstrate that, like in our prior T and B cell studies, alveolar macrophages neither prevent hantavirus infection nor cause hantavirus disease. While these studies reflect pathogenesis in the hamster model, they should help us rule out specific cell types and prompt us to consider other potential mechanisms of disease in an effort to improve the outcome of human HPS.

Assessing the safety and immunogenicity of recombinant vesicular stomatitis virus Ebola vaccine in healthy adults: a randomized clinical trial.

BACKGROUND: The 2013-2016 Ebola virus outbreak in West Africa was the most widespread in history. In response, alive attenuated recombinant vesicular stomatitis virus (rVSV) vaccine expressing Zaire Ebolavirus glycoprotein (rVSVΔG-ZEBOV-GP) was evaluated in humans. METHODS: In a phase 1, randomized, dose-ranging, observer-blind, placebo-controlled trial, healthy adults aged 18-65 years were randomized into 4 groups of 10 to receive one of 3 vaccine doses or placebo. Follow-up visits spanned 180 days postvaccination for safety monitoring, immunogenicity testing and any rVSV virus shedding. RESULTS: Forty participants were injected with rVSVΔG-ZEBOV-GP vaccine (n = 30) or saline placebo (n = 10). No serious adverse events related to the vaccine or participant withdrawals were reported. Solicited adverse events during the 14-day follow-up period were mild to moderate and self-limited, with the exception of injection-site pain and headache. Viremia following vaccination was transient and no longer detectable after study day 3, with no virus shedding in saliva or urine. All vaccinated participants developed serum immunoglobulin G (IgG), as measured by Ebola virus envelope glycoprotein-based enzyme-linked immunosorbent assay (ELISA). Immunogenicity was comparable across all dose groups, and sustained IgG titers were detectable through to the last visit, at study day 180. INTERPRETATION: In this phase 1 study, there were no safety concerns after a single dose of rVSVΔG-ZEBOV-GP vaccine. IgG ELISA showed persistent high titers at 180 days postimmunization. There was a period of reactogenicity, but in general, the vaccine was well tolerated. This study provides evidence of the safety and immunogenicity of rVSVΔG-ZEBOV-GP vaccine and importance of its further investigation. Trial registration: Clinical-Trials.gov no., NCT02374385.

Preclinical Development of Inactivated Rabies Virus-Based Polyvalent Vaccine Against Rabies and Filoviruses.

We previously described the generation of a novel Ebola virus (EBOV) vaccine based on inactivated rabies virus (RABV) containing EBOV glycoprotein (GP) incorporated in the RABV virion. Our results demonstrated safety, immunogenicity, and protective efficacy in mice and nonhuman primates (NHPs). Protection against viral challenge depended largely on the quality of the humoral immune response against EBOV GP.Here we present the extension and improvement of this vaccine by increasing the amount of GP incorporation into virions via GP codon-optimization as well as the addition of Sudan virus (SUDV) and Marburg virus (MARV) GP containing virions. Immunogenicity studies in mice indicate similar immune responses for both SUDV GP and MARV GP compared to EBOV GP. Immunizing mice with multiple antigens resulted in immune responses similar to immunization with a single antigen. Moreover, immunization of NHP with the new inactivated RABV EBOV vaccine resulted in high titer neutralizing antibody levels and 100% protection against lethal EBOV challenge when applied with adjuvant.Our results indicate that an inactivated polyvalent vaccine against RABV filoviruses is achievable. Finally, the novel vaccines are produced on approved VERO cells and a clinical grade RABV/EBOV vaccine for human trials has been produced.

A lethal disease model for hantavirus pulmonary syndrome in immunosuppressed Syrian hamsters infected with Sin Nombre virus.

Sin Nombre virus (SNV) is a rodent-borne hantavirus that causes hantavirus pulmonary syndrome (HPS) predominantly in North America. SNV infection of immunocompetent hamsters results in an asymptomatic infection; the only lethal disease model for a pathogenic hantavirus is Andes virus (ANDV) infection of Syrian hamsters. Efforts to create a lethal SNV disease model in hamsters by repeatedly passaging virus through the hamster have demonstrated increased dissemination of the virus but no signs of disease. In this study, we demonstrate that immunosuppression of hamsters through the administration of a combination of dexamethasone and cyclophosphamide, followed by infection with SNV, results in a vascular leak syndrome that accurately mimics both HPS disease in humans and ANDV infection of hamsters. Immunosuppressed hamsters infected with SNV have a mean number of days to death of 13 and display clinical signs associated with HPS, including pulmonary edema. Viral antigen was widely detectable throughout the pulmonary endothelium. Histologic analysis of lung sections showed marked inflammation and edema within the alveolar septa of SNV-infected hamsters, results which are similar to what is exhibited by hamsters infected with ANDV. Importantly, SNV-specific neutralizing polyclonal antibody administered 5 days after SNV infection conferred significant protection against disease. This experiment not only demonstrated that the disease was caused by SNV, it also demonstrated the utility of this animal model for testing candidate medical countermeasures. This is the first report of lethal disease caused by SNV in an adult small-animal model.

Glycoprotein-Specific Polyclonal Antibodies Targeting Machupo Virus Protect Guinea Pigs against Lethal Infection.

Convalescent plasma has been shown to be effective at protecting humans against severe diseases caused by New World (NW) arenaviruses, including Junin virus (JUNV) and Machupo virus (MACV). This plasma contains antibodies against the full complement of structural proteins including the nucleocapsid and envelope glycoproteins (GPcs) consisting of GP1 and GP2. To gain insights into the protective and cross-protective properties of anti-GPc-specific polyclonal antibodies, we evaluated the ability of a DNA vaccine-produced anti-GPc rabbit antisera targeting MACV strain Carvallo to provide heterologous protection against another MACV strain termed Chicava in the Hartley guinea pig model. The neutralizing activity of the rabbit antisera against the heterologous MACV strains Chicava and Mallale was found to be 54-fold and 23-fold lower, respectively, compared to the titer against the homologous MACV strain Carvallo in the PRNT50 assay. Despite lower neutralizing activity against the strain Chicava, the rabbit antisera protected 100% of the guinea pigs from this strain when administered up to four days post-infection, whereas all the control animals succumbed to the disease. Using vesicular stomatitis virus (VSV) particles pseudotyped with MACV GPc, we identified a single amino acid difference at position 122 between the strains Chicava and Carvallo GPc that significantly influenced the neutralization activity of the rabbit antisera. These findings indicate that polyclonal antibodies targeting the MACV glycoproteins can protect against lethal infection in a post-challenge setting. These data will help guide future antibody-based therapeutics development against NW arenaviruses.

Safety and Immunogenicity of an Accelerated Ebola Vaccination Schedule in People with and without Human Immunodeficiency Virus: A Randomized Clinical Trial.

The safety and immunogenicity of the two-dose Ebola vaccine regimen MVA-BN-Filo, Ad26.ZEBOV, 14 days apart, was evaluated in people without HIV (PWOH) and living with HIV (PLWH). In this observer-blind, placebo-controlled, phase 2 trial, healthy adults were randomized (4:1) to receive MVA-BN-Filo (dose 1) and Ad26.ZEBOV (dose 2), or two doses of saline/placebo, administered intramuscularly 14 days apart. The primary endpoints were safety (adverse events (AEs)) and immunogenicity (Ebola virus (EBOV) glycoprotein-specific binding antibody responses). Among 75 participants (n = 50 PWOH; n = 25 PLWH), 37% were female, the mean age was 44 years, and 56% were Black/African American. AEs were generally mild/moderate, with no vaccine-related serious AEs. At 21 days post-dose 2, EBOV glycoprotein-specific binding antibody responder rates were 100% among PWOH and 95% among PLWH; geometric mean antibody concentrations were 6286 EU/mL (n = 36) and 2005 EU/mL (n = 19), respectively. A total of 45 neutralizing and other functional antibody responses were frequently observed. Ebola-specific CD4+ and CD8+ T-cell responses were polyfunctional and durable to at least 12 months post-dose 2. The regimen was well tolerated and generated robust, durable immune responses in PWOH and PLWH. Findings support continued evaluation of accelerated vaccine schedules for rapid deployment in populations at immediate risk. Trial registration: NCT02598388 (submitted 14 November 2015).

Humoral immunogenicity of a Coronavirus Disease 2019 (COVID-19) DNA vaccine in rhesus macaques (Macaca mulatta) delivered using needle-free jet injection.

A SARS-CoV-2 DNA vaccine targeting the spike protein and delivered by jet injection, nCOV-S(JET), previously shown to protect wild-type and immunosuppressed Syrian hamsters (Mesocricetus auratus), was evaluated via two needle-free delivery methods in rhesus macaques (Macaca mulatta). The methods included intramuscular delivery of 2 mg per vaccination with the PharmaJet Stratis device and intradermal delivery of 0.4 mg per vaccination with the PharmaJet Tropis device. We hypothesized that the nCOV-S(JET) vaccine would mount detectable neutralizing antibody responses when delivered by needle-free jet injection by either the intradermal or intramuscular route. When delivered intramuscularly, the vaccines elicited neutralizing and variant (Beta, Gamma, and Delta) cross-neutralizing antibodies against SARS-CoV-2 in all six animals after three vaccinations. The neutralizing response to Omicron was lower with only 4 of 6 animals responding. When delivered at a lower dose by the intradermal route, strong neutralizing antibody responses were only detected in two of six animals. This study confirms that a vaccine previously shown to protect in a hamster model can elicit neutralizing and cross-neutralizing antibodies against SARS-CoV-2 in nonhuman primates. We posit that nCOV-S(JET) has the potential for use as booster vaccine in heterologous vaccination strategies against COVID-19.