Biology subjects

Bavari, S.

Publications and source records attributed to Bavari, S..

8 recordsLinked to original sources

bioRxiv2025

Monkeypox Virus Clade IIb Isolate Exhibits Reduced Virulence Relative to Clade IIa Isolates in Multiple Murine Models

Monkeypox virus (MPXV) is the causative agent of mpox disease in humans. The virus is comprised of two clades, Central African clade I and West African clade II with case fatality rates of [~]11 and [~]4%, respectively. Since the discovery of mpox disease in 1970, the virus has been restricted to Africa. However, in 2022, a previously unrecognized subclade IIb caused the largest global outbreak of mpox disease with a case fatality rate of [~]0.2%. The difference in virulence of MPXV subclades in human infection warrants further investigation, however, one critical limitation is the lack of susceptible small animal models. In this study, we investigated the susceptibility of four murine models, including CAST-EiJ and three immunocompromised models (C57BL/6 Ifnar-/-, C57BL/6 Ifngr-/-, and C57BL/6 Ifnar-/-/Ifngr-/-) to MPXV clade IIa (WR 7-61 and US-2003) and IIb (MA-2022) isolates. All four mouse models were susceptible to clade IIa infection, leading to severe disease marked by decreased body temperature, weight loss, and lethality. In contrast, clade IIb infection produced minimal to mild disease at similar doses in all four murine models. The clade IIb isolate produced severe disease (40% lethality) at only the highest dose (8.0 log10 PFU) in the most susceptible immunocompromised mouse model, C57BL/6 Ifnar-/-/Ifngr-/-. This is the first demonstration of lethal disease with clade IIb in a murine model. In addition, these data demonstrate that clade IIa is [~]100- to 100,000-fold more virulent than clade IIb and provide three additional murine models for investigating MPXV infection and pathogenesis. IMPORTANCEMpox is an emerging human disease caused by four distinct MPXV subclades (Ia, Ib, IIa, and IIb). Despite genetic similarities, the case fatality rate varies considerably between the subclades: Ia ([~]11%), Ib and IIa ([~]4%), and IIb ([~]0.2%). Since 2022, multiple mpox outbreaks have occurred due to previously unrecognized subclades, leading to the declaration of two public health emergencies by the World Health Organization. This unprecedented global spread, coupled with the variation in severity of human disease, underscores the importance of research into the pathogenesis of emerging MPXV subclades. However, a critical limitation is the lack of suitable small animal models. This study identifies three additional murine models susceptible to MPXV clade II infection and demonstrates significant virulence differences between clade IIa and IIb. These models will enable rapid characterization of previously unrecognized subclades and will facilitate countermeasure development.

microbiology↗

bioRxiv2023

Recombinant chimeric Horsepox Virus (TNX-801) is attenuated relative to Vaccinia Virus Strains in Human Primary Cell Lines and in Immunocompromised Mice

Recombinant chimeric Horsepox virus (TNX-801) is a preclinical vaccine in development against Monkeypox and smallpox. In this brief report, we investigated the potential phenotypic differences in in vitro and in vivo models between TNX-801 and older VACV-based vaccine strains (VACV-IHD, VACV-Lis, VACV-NYC) used in the eradication of smallpox virus. TNX-801 displayed a small plaque phenotype ([~]1-2 mm) in both BSC-40 and Vero-E6 cells and yielded >10- to 100-fold lower infectious titers than the VACV strains in multiple-step replication kinetics. Growth kinetics in primary human cell lines from two main routes of poxvirus transmission, respiratory and dermal tracts, yielded [~]10- to 119-fold lower infectious titers of TNX-801. Intranasal infection of immunocompromised mice (C56BL/6 Ifnar-/-/Ifngr-/-) with VACV strains at 6.0 and 5.0 log10 PFU produced uniform lethal disease. In contrast, TNX-801 at 8.0 log10 PFU was unable to produce any clinical disease in mice. These data demonstrate that TNX-801 is >10- to 1,000-fold more attenuated than older VACV-based smallpox vaccines in human primary cell lines and immunocompromised mice.

microbiology↗

bioRxiv2023

Immunogenicity and Efficacy of TNX-1800, A Live Virus Recombinant Poxvirus Vaccine Candidate, Against SARS-CoV-2 Challenge in Nonhuman Primates

TNX-1800 is a synthetically derived live chimeric Horsepox Virus (rcHPXV) vaccine expressing Wuhan SARS-CoV-2 spike (S) protein. The primary objective of this study was to evaluate the immunogenicity and efficacy of TNX-1800 in two nonhuman primate species challenged with USA-WA1/2020 SARS-CoV-2. TNX-1800 vaccination was well tolerated, as indicated by the lack of serious adverse events or significant changes in clinical parameters. A single dose of TNX-1800 generated robust humoral responses in African Green Monkeys and Cynomolgus Macaques, as measured by the total binding anti-SARS-CoV-2 S IgG and neutralizing antibody titers against the USA-WA1/2020 strain. In Cynomolgus Macaques, a single dose of TNX-1800 induced a strong interferon-gamma (IFN-{gamma}) mediated T cell response, promoting both pathogen clearance in the upper and lower airways and generation of systemic neutralizing antibody response against WA strain SARS-CoV-2. Future studies will assess the efficacy of TNX-1800 against newly emerging variants and demonstrate its safety in humans.

immunology↗

bioRxiv2023

Immunogenicity and tolerability of a SARS-CoV-2 TNX-1800, a live recombinant poxvirus vaccine candidate, in Syrian Hamsters and New Zealand White Rabbits.

TNX-1800 is a preclinical stage synthetic derived live chimeric horsepox virus vaccine that comprises an engineered SARS-CoV-2 spike (S) gene expression cassette. The objectives of this study were to assess the immunogenicity and tolerability of TNX-1800 administration in Syrian golden hamsters and New Zealand white rabbits. Animals were vaccinated via percutaneous inoculation and evaluated for dose tolerance and immunogenicity at three different dose levels. The 28-day study data showed that the single percutaneous administration of three TNX-1800 vaccine dose levels was well tolerated in both hamsters and rabbits. For all dose levels, rabbits had more dermal observations than hamsters at the same dose levels. Vaccine-induced viral load four weeks post-dosing was below the detection level for both species.

immunology↗

bioRxiv2020

The Utilization of Advance Telemetry to Investigate Important Physiological Parameters Including Electroencephalography in Cynomolgus Macaques Following Aerosol Challenge with Eastern Equine Encephalitis Virus

Most alphaviruses are mosquito-borne and can cause severe disease in humans and domesticated animals. In North America, eastern equine encephalitis virus (EEEV) is an important human pathogen with case fatality rates of 30-90%. Currently, there are no therapeutics or vaccines to treat and/or prevent human infection. One critical impediment in countermeasure development is the lack of insight into clinically relevant parameters in a susceptible animal model. This study examined the disease course of EEEV in a cynomolgus macaque model utilizing advanced telemetry technology to continuously and simultaneously measure temperature, respiration, activity, heart rate, blood pressure, electrocardiogram (ECG), and electroencephalography (EEG) following an aerosol challenge at 7.0 log10 PFU. Following challenge, all parameters were rapidly and substantially altered with peak alterations from baseline ranged as follows: temperature (+3.0-4.2 {degrees}C), respiration rate (+56-128%), activity (+15-76% daytime and +5-22% nighttime), heart rate (+67-190%), systolic (+44-67%) and diastolic blood pressure (+45-80%). Cardiac abnormalities comprised of alterations in QRS and PR duration, QTc Bazett, T wave morphology, amplitude of the QRS complex, and sinoatrial arrest. An unexpected finding of the study was the first documented evidence of a critical cardiac event as an immediate cause of euthanasia in one NHP. All brain waves were rapidly (12-24 hpi) and profoundly altered with increases of up to 6,800% and severe diffuse slowing of all waves with decreases of [~]99%. Lastly, all NHPs exhibited disruption of the circadian rhythm, sleep, and food/fluid intake. Accordingly, all NHPs met the euthanasia criteria by [~]106-140 hpi. This is the first of its kind study utilizing state of the art telemetry to investigate multiple clinical parameters relevant to human EEEV infection in a susceptible cynomolgus macaque model. The study provides critical insights into EEEV pathogenesis and the parameters identified will improve animal model development to facilitate rapid evaluation of vaccines and therapeutics. Author SummaryIn North America, EEEV causes the most severe mosquito-borne disease in humans highlighted by fatal encephalitis and permeant debilitating neurological sequelae in survivors. The first confirmed human cases were reported more than 80 years ago and since then multiple sporadic outbreaks have occurred including one of the largest in 2019. Unfortunately, most human infections are diagnosed at the on-set of severe neurological symptoms and consequently a detailed disease course in humans is lacking. This gap in knowledge is a significant obstacle in the development of appropriate animal models to evaluate countermeasures. Here, we performed a cutting-edge study by utilizing a new telemetry technology to understand the course of EEEV infection in a susceptible macaque model by measuring multiple physiological parameters relevant to human disease. Our study demonstrates that the infection rapidly produces considerable alterations in many critical parameters including the electrical activity of the heart and the brain leading to severe disease. The study also highlights the extraordinary potential of new telemetry technology to develop the next generation of animal models in order to comprehensively investigate pathogenesis as well as evaluate countermeasures to treat and/or prevent EEEV disease.

microbiology↗

bioRxiv2020

Eastern Equine Encephalitis Virus Rapidly Infects and Disseminates in the Brain and Spinal Cord of Infected Cynomolgus Macaques Following Aerosol Challenge

Eastern equine encephalitis virus (EEEV) is mosquito-borne virus that produces fatal encephalitis in humans. We recently conducted a first of its kind study to investigate EEEV clinical disease course following aerosol challenge in a cynomolgus macaque model utilizing the state of the art telemetry to measure critical physiological parameters. Following challenge, all parameters were rapidly and profoundly altered, and all nonhuman primates (NHPs) met the euthanasia criteria. In this study, we performed the first comprehensive pathology investigation of tissues collected at euthanasia to gain insights into EEEV pathogenesis. Viral RNA and proteins as well as microscopic lesions were absent in the visceral organs. In contrast, viral RNA and proteins were readily detected throughout the brain including autonomic nervous system (ANS) control centers and spinal cord. However, despite presence of viral RNA and proteins, majority of the brain and spinal cord tissues exhibited minimal or no microscopic lesions. The virus tropism was restricted primarily to neurons, and virus particles (~61-68 nm) were present within axons of neurons and throughout the extracellular spaces. However, active virus replication was absent or minimal in majority of the brain and was limited to regions proximal to the olfactory tract. These data suggest that EEEV initially replicates in/near the olfactory bulb following aerosol challenge and is rapidly transported to distal regions of the brain by exploiting the neuronal axonal transport system to facilitate neuron-to-neuron spread. Once within the brain, the virus gains access to the ANS control centers likely leading to disruption and/or dysregulation of critical physiological parameters to produce severe disease. Moreover, the absence of microscopic lesions strongly suggests that the underlying mechanism of EEEV pathogenesis is due to neuronal dysfunction rather than neuronal death. This study is the first comprehensive investigation of EEEV clinical disease course and pathogenesis in a NHP model and will provide significant insights into the evaluation of countermeasure. Author SummaryEEEV is an arbovirus endemic in parts of North America and is able to produce fatal encephalitis in humans and domesticated animals. Despite multiple human outbreaks during the last 80 years, there are still no therapeutic or vaccines to treat or prevent human disease. One critical obstacle in the development of effective countermeasure is the lack of insights into EEEV pathogenesis in a susceptible animal host. We recently conducted a study in cynomolgus macaques to investigate the disease course by measuring clinical parameters relevant to humans. Following infection, these parameters were rapidly and profoundly altered leading to severe disease. In this study, we examined the potential mechanisms that underlie pathogenesis to cause severe disease. The virus was present in many parts of the brain and spinal cord, however, little or no pathological lesions as well as active virus replication were observed. Additionally, neurons were the predominant target of EEEV and virus transport was facilitated by axonal transport system to spread neuron-to-neuron throughout the brain and spinal cord. These data show that EEEV likely hijacks host cell transport system to rapidly spread in the brain and local/global neuronal dysfunction rather than death is the principal cause of severe disease.

microbiology↗

bioRxiv2020

The DHODH Inhibitor PTC299 Arrests SARS-CoV-2 Replication and Suppresses Induction of Inflammatory Cytokines

The coronavirus disease 2019 (COVID-19) pandemic has created an urgent need for therapeutics that inhibit the SARS-CoV-2 virus and suppress the fulminant inflammation characteristic of advanced illness. Here, we describe the anti-COVID-19 potential of PTC299, an orally available compound that is a potent inhibitor of dihydroorotate dehydrogenase (DHODH), the rate-limiting enzyme of the de novo pyrimidine biosynthesis pathway. In tissue culture, PTC299 manifests robust, dose-dependent, and DHODH-dependent inhibition of SARS CoV-2 replication (EC50 range, 2.0 to 31.6 nM) with a selectivity index >3,800. PTC299 also blocked replication of other RNA viruses, including Ebola virus. Consistent with known DHODH requirements for immunomodulatory cytokine production, PTC299 inhibited the production of interleukin (IL)-6, IL-17A (also called IL-17), IL-17F, and vascular endothelial growth factor (VEGF) in tissue culture models. The combination of anti-SARS-CoV-2 activity, cytokine inhibitory activity, and previously established favorable pharmacokinetic and human safety profiles render PTC299 a promising therapeutic for COVID-19.

immunology↗

bioRxiv2017

DDX3 is exploited by Arenaviruses to suppress type I interferons and favor their replication

Several arenaviruses cause hemorrhagic fever (HF) diseases that are associated with high morbidity and mortality in humans. Accordingly, HF arenaviruses have been listed as top-priority emerging diseases for which countermeasures are urgently needed. Because arenavirus nucleoprotein (NP) plays critical roles in both virus multiplication and immune-evasion, we used an unbiased proteomic approach to identify NP-interacting proteins in human cells. DDX3, a DEAD-box ATP-dependent-RNA-helicase, interacted with NP in both NP-transfected and virus-infected cells. Importantly, DDX3 deficiency compromised the propagation of both Old and New World arenaviruses, including the HF arenaviruses Lassa and Junin viruses. The DDX3 role in promoting arenavirus multiplication correlated with both a previously un-recognized DDX3 contribution to type I interferon suppression in arenavirus infected cells and a positive effect of DDX3 on viral RNA synthesis. Our results uncover novel mechanisms used by arenavirus to exploit the host machinery and subvert immunity, singling out DDX3 as a potential host target for developing new therapies against highly pathogenic arenaviruses.\n\nAUTHOR SUMMARYArenaviruses include severe clinical pathogens causing hemorrhagic fevers and have been recently incorporated by the World Health Organization in a list of critical emerging diseases for which additional research and identification of clinical targets is urgently required. A better understanding of how viral proteins interact with host cellular factors to favor arenavirus multiplication can illuminate novel pipelines on therapeutic strategies. Here we demonstrated that the ATP-dependent RNA helicase DDX3 interacted with the arenavirus nucleoprotein, which displays fundamental functions in different steps of the viral-cycle. Our work also revealed an unexpected new biology on the role that DDX3 might play during viral infections. In sharp contrast to previous studies showing DDX3 enhancement of IFN-I induction, we demonstrated that DDX3 suppressed IFN-I production at late time points after arenavirus infection, contributing to a DDX3 pro-viral effect. We also showed that early after infection, DDX3 pro-viral role was IFN-I independent and was mediated by DDX3 facilitation of viral RNA synthesis without affecting RNA translation. Altogether, our study established DDX3 as a critical host interacting partner of the arenavirus nucleoprotein and demonstrated two previously unrecognized DDX3-dependent strategies by which these deadly viruses exploit the host cellular machinery and suppress immunity.

microbiology↗