Investigative study into whether an insect repellent has virucidal activity against SARS-CoV-2.

A small-scale study with Mosi-guard Natural spray, an insect repellent containing Citriodiol, was performed to determine if it has virucidal activity against SARS-CoV-2. A liquid test examined the activity of the insect repellent and the individual components for virucidal activity. A surface contact test looked at the activity of the insect repellent when impregnated on a latex surface as a synthetic skin for potential topical prophylactic application. Both Mosi-guard Natural spray and Citriodiol, as well as other components of the repellent, had virucidal activity in the liquid contact test. On a latex surface used to simulate treated skin, the titre of SARS-CoV-2 was less over time on the Mosi-guard Natural-treated surface but virus was still recovered.

Aerosol infection of Balb/c mice with eastern equine encephalitis virus; susceptibility and lethality.

BACKGROUND: Eastern equine encephalitis virus is an alphavirus that naturally cycles between mosquitoes and birds or rodents in Eastern States of the US. Equine infection occurs by being bitten by cross-feeding mosquitoes, with a case fatality rate of up to 75% in humans during epizootic outbreaks. There are no licensed medical countermeasures, and with an anticipated increase in mortality when exposed by the aerosol route based on anecdotal human data and experimental animal data, it is important to understand the pathogenesis of this disease in pursuit of treatment options. This report details the clinical and pathological findings of mice infected with EEEV by the aerosol route, and use as a model for EEEV infection in humans. METHODS: Mice were exposed by the aerosol route to a dose range of EEEV to establish the median lethal dose. A pathogenesis study followed whereby mice were exposed to a defined dose of virus and sacrificed at time-points thereafter for histopathological analysis and virology. RESULTS: Clinical signs of disease appeared within 2 days post challenge, culminating in severe clinical signs within 24 h, neuro-invasion and dose dependent lethality. EEEV was first detected in the lung 1 day post challenge, and by day 3 peak viral titres were observed in the brain, spleen and blood, corresponding with severe meningoencephalitis, indicative of encephalitic disease. Lethality follows severe neurological signs, and may be linked to a threshold level of virus replication in the brain. Effective medical countermeasures for EEEV may necessitate early inoculation to inhibit infection of the brain in zoonotic incidents, and be able to traverse the blood-brain barrier to sufficiently interrupt replication in the brain in cases of aerosol infection. CONCLUSIONS: There is little human data on the hazard posed by aerosol infection with encephalitic alphaviruses, and use of EEEV as a bioweapon may be by the aerosol route. A well characterized model of aerosol exposure that recapitulates some of the most severe human clinical features is necessary to evaluate the efficacy of putative medical countermeasures, and to increase our understanding about how this route of infection induces such rapid neuro-invasion and resulting disease.

Two-Center Evaluation of Disinfectant Efficacy against Ebola Virus in Clinical and Laboratory Matrices.

Ebola virus (EBOV) in body fluids poses risk for virus transmission. However, there are limited experimental data for such matrices on the disinfectant efficacy against EBOV. We evaluated the effectiveness of disinfectants against EBOV in blood on surfaces. Only 5% peracetic acid consistently reduced EBOV titers in dried blood to the assay limit of quantification.

Ebola Virus Makona Shows Reduced Lethality in an Immune-deficient Mouse Model.

Ebola virus Makona (EBOV-Makona; from the 2013-2016 West Africa outbreak) shows decreased virulence in an immune-deficient mouse model, compared with a strain from 1976. Unlike other filoviruses tested, EBOV-Makona may be slightly more virulent by the aerosol route than by the injected route, as 2 mice died following aerosol exposure, compared with no mortality among mice that received intraperitoneal injection of equivalent or higher doses. Although most mice did not succumb to infection, the detection of an immunoglobulin G antibody response along with observed clinical signs suggest that the mice were infected but able to clear the infection and recover. We hypothesize that this may be due to the growth rates and kinetics of the virus, which appear slower than that for other filoviruses and consequently give more time for an immune response that results in clearance of the virus. In this instance, the immune-deficient mouse model is unlikely to be appropriate for testing medical countermeasures against this EBOV-Makona stock but may provide insight into pathogenesis and the immune response to virus.

Experimental Respiratory Infection of Marmosets (Callithrix jacchus) With Ebola Virus Kikwit.

Ebola virus (EBOV) causes a highly infectious and lethal hemorrhagic fever in primates with high fatality rates during outbreaks and EBOV may be exploited as a potential biothreat pathogen. There is therefore a need to develop and license appropriate medical countermeasures against this virus. To determine whether the common marmoset (Callithrix jacchus) would be an appropriate model to assess vaccines or therapies against EBOV disease (EVD), initial susceptibility, lethality and pathogenesis studies were performed. Low doses of EBOV-Kikwit, between 4 and 27 times the 50% tissue culture infectious dose, were sufficient to cause a lethal, reproducible infection. Animals became febrile between days 5 and 6, maintaining a high fever before succumbing to EVD between 6 and 8 days after challenge. Typical signs of EVD were observed. Pathogenesis studies revealed that virus was isolated from the lungs of animals beginning on day 3 after challenge and from the liver, spleen and blood beginning on day 5. The most striking features were observed in animals that succumbed to infection, including high viral titers in all organs, increased levels of liver function enzymes and blood clotting times, decreased levels of platelets, multifocal moderate to severe hepatitis, and perivascular edema.

Buffer AVL Alone Does Not Inactivate Ebola Virus in a Representative Clinical Sample Type.

Rapid inactivation of Ebola virus (EBOV) is crucial for high-throughput testing of clinical samples in low-resource, outbreak scenarios. The EBOV inactivation efficacy of Buffer AVL (Qiagen) was tested against marmoset serum (EBOV concentration of 1 × 10(8) 50% tissue culture infective dose per milliliter [TCID50 · ml(-1)]) and murine blood (EBOV concentration of 1 × 10(7) TCID50 · ml(-1)) at 4:1 vol/vol buffer/sample ratios. Posttreatment cell culture and enzyme-linked immunosorbent assay (ELISA) analysis indicated that treatment with Buffer AVL did not inactivate EBOV in 67% of samples, indicating that Buffer AVL, which is designed for RNA extraction and not virus inactivation, cannot be guaranteed to inactivate EBOV in diagnostic samples. Murine blood samples treated with ethanol (4:1 [vol/vol] ethanol/sample) or heat (60°C for 15 min) also showed no viral inactivation in 67% or 100% of samples, respectively. However, combined Buffer AVL and ethanol or Buffer AVL and heat treatments showed total viral inactivation in 100% of samples tested. The Buffer AVL plus ethanol and Buffer AVL plus heat treatments were also shown not to affect the extraction of PCR quality RNA from EBOV-spiked murine blood samples.

Experimental respiratory Marburg virus haemorrhagic fever infection in the common marmoset (Callithrix jacchus).

Marburg virus causes a highly infectious and lethal haemorrhagic fever in primates and may be exploited as a potential biothreat pathogen. To combat the infection and threat of Marburg haemorrhagic fever, there is a need to develop and license appropriate medical countermeasures. To determine whether the common marmoset (Callithrix jacchus) would be an appropriate model to assess therapies against Marburg haemorrhagic fever, initial susceptibility, lethality and pathogenesis studies were performed. Low doses of virus, between 4 and 28 TCID50 , were sufficient to cause a lethal, reproducible infection. Animals became febrile between days 5 and 6, maintaining a high fever before succumbing to disease between 8 and 11 days postchallenge. Typical signs of Marburg virus infection were observed including haemorrhaging and a transient rash. In pathogenesis studies, virus was isolated from the animals' lungs from day 3 postchallenge and from the liver, spleen and blood from day 5 postchallenge. Early signs of histopathology were apparent in the kidney and liver from day 3. The most striking features were observed in animals exhibiting severe clinical signs, which included high viral titres in all organs, with the highest levels in the blood, increased levels in liver function enzymes and blood clotting times, decreased levels in platelets, multifocal moderate-to-severe hepatitis and perivascular oedema.

Comparison of Aerosol Stability of Different Variants of Ebola Virus and Marburg Virus and Virulence of Aerosolised Ebola Virus in an Immune-Deficient Mouse.

During outbreaks of virus diseases, many variants may appear, some of which may be of concern. Stability in an aerosol of several Ebola virus and Marburg virus variants was investigated. Studies were performed measuring aerosol survival using the Goldberg drum but no significant difference in biological decay rates between variants was observed. In addition, historic data on virulence in a murine model of different Ebola virus variants were compared to newly presented data for Ebola virus Kikwit in the A129 Interferon alpha/beta receptor-deficient mouse model. Ebola virus Kikwit was less virulent than Ebola virus Ecran in our mouse model. The mouse model may be a useful tool for studying differences in virulence associated with different variants whereas aerosol stability studies may not need to be conducted beyond the species level.

Aerosol Survival, Disinfection and Formalin Inactivation of Nipah Virus.

Nipah virus is a relatively newly discovered emerging virus on the WHO list of priority pathogens which has the potential to cause outbreaks with high fatality rates. Whilst progress is being made in the development of animal models for evaluating vaccines and therapies, some of the more fundamental data on Nipah virus are lacking. We performed studies to generate novel information on the aerosol survival of Nipah virus and to look at the efficacy of two common disinfectants. We also performed studies to evaluate the inactivation of Nipah virus by using neutral buffered formalin. Nipah virus was relatively stable in a small particle (1-5 µm) aerosol in the dark, with it having a decay rate of 1.46%min-1. Sodium hypochlorite (at 10%) and ethanol (at 80%) reduced the titre of Nipah virus to undetectable levels. Nipah virus that was in tissue culture medium was also inactivated after 24 h in the presence of 10% formalin.

Histopathological and Immunological Findings in the Common Marmoset Following Exposure to Aerosolized SARS-CoV-2.

There is an enduring requirement to develop animal models of COVID-19 to assess the efficacy of vaccines and therapeutics that can be used to treat the disease in humans. In this study, six marmosets were exposed to a small particle aerosol (1-3 µm) of SARS-CoV-2 VIC01 that delivered the virus directly to the lower respiratory tract. Following the challenge, marmosets did not develop clinical signs, although a disruption to the normal diurnal temperature rhythm was observed in three out of six animals. Early weight loss and changes to respiratory pattern and activity were also observed, yet there was limited evidence of viral replication or lung pathology associated with infection. There was a robust innate immunological response to infection, which included an early increase in circulating neutrophils and monocytes and a reduction in the proportion of circulating T-cells. Expression of the ACE2 receptor in respiratory tissues was almost absent, but there was ubiquitous expression of TMPRSS2. The results of this study indicate that exposure of marmosets to high concentrations of aerosolised SARS-CoV-2 did not result in the development of clear, reproducible signs of COVID-19.

Evaluation of the SARS-CoV-2 Inactivation Efficacy Associated With Buffers From Three Kits Used on High-Throughput RNA Extraction Platforms.

Rapid and demonstrable inactivation of SARS-CoV-2 is crucial to ensure operator safety during high-throughput testing of clinical samples. The inactivation efficacy of SARS-CoV-2 was evaluated using commercially available lysis buffers from three viral RNA extraction kits used on two high-throughput (96-well) RNA extraction platforms (Qiagen QIAcube HT and the Thermo Fisher KingFisher Flex) in combination with thermal treatment. Buffer volumes and sample ratios were chosen for their optimised suitability for RNA extraction rather than inactivation efficacy and tested against a representative sample type: SARS-CoV-2 spiked into viral transport medium (VTM). A lysis buffer mix from the MagMAX Pathogen RNA/DNA kit (Thermo Fisher), used on the KingFisher Flex, which included guanidinium isothiocyanate (GITC), a detergent, and isopropanol, demonstrated a minimum inactivation efficacy of 1 × 105 tissue culture infectious dose (TCID)50/ml. Alternative lysis buffer mixes from the MagMAX Viral/Pathogen Nucleic Acid kit (Thermo Fisher) also used on the KingFisher Flex and from the QIAamp 96 Virus QIAcube HT Kit (Qiagen) used on the QIAcube HT (both of which contained GITC and a detergent) reduced titres by 1 × 104 TCID50/ml but did not completely inactivate the virus. Heat treatment alone (15 min, 68°C) did not completely inactivate the virus, demonstrating a reduction of 1 × 103 TCID50/ml. When inactivation methods included both heat treatment and addition of lysis buffer, all methods were shown to completely inactivate SARS-CoV-2 inactivation against the viral titres tested. Results are discussed in the context of the operation of a high-throughput diagnostic laboratory.

Corrigendum: Evaluation of the SARS-CoV-2 Inactivation Efficacy Associated With Buffers From Three Kits Used on High-Throughput RNA Extraction Platforms.

[This corrects the article DOI: 10.3389/fcimb.2021.716436.].

Experimental aerosol survival of SARS-CoV-2 in artificial saliva and tissue culture media at medium and high humidity.

SARS-CoV-2, the causative agent of the COVID-19 pandemic, may be transmitted via airborne droplets or contact with surfaces onto which droplets have deposited. In this study, the ability of SARS-CoV-2 to survive in the dark, at two different relative humidity values and within artificial saliva, a clinically relevant matrix, was investigated. SARS-CoV-2 was found to be stable, in the dark, in a dynamic small particle aerosol under the four experimental conditions we tested and viable virus could still be detected after 90 minutes. The decay rate and half-life was determined and decay rates ranged from 0.4 to 2.27 % per minute and the half lives ranged from 30 to 177 minutes for the different conditions. This information can be used for advice and modelling and potential mitigation strategies.

Survival of Lassa Virus in Blood and Tissue Culture Media and in a Small Particle Aerosol.

Knowledge of the survival and stability of a pathogen is important for understanding its risk, reducing its transmission, and establishing control measures. Lassa virus is endemic in West Africa, causes severe disease, and is an emerging pathogen of concern. Our study examined the survival of Lassa virus in blood and tissue culture media at two different temperatures. The stability of Lassa virus held within a small particle aerosol was also measured. In liquids, Lassa virus was found to decay more quickly at 30 °C compared to room temperature. Sealed samples protected from environmental desiccation were more stable than samples open to the environment. In a small particle aerosol, the decay rate of Lassa virus was determined at 2.69% per minute. This information can contribute to risk assessments and inform mitigation strategies in the event of an outbreak of Lassa virus.

An Investigation of the Effect of Transfected Defective, Ebola Virus Genomes on Ebola Replication.

As the ongoing outbreak in the Democratic Republic of Congo illustrates, Ebola virus disease continues to pose a significant risk to humankind and this necessitates the continued development of therapeutic options. One option that warrants evaluation is that of defective genomes; these can potentially parasitize resources from the wild-type virus and may even be packaged for repeated co-infection cycles. Deletion and copy-back defective genomes have been identified and reported in the literature. As a crude, mixed preparation these were found to have limiting effects on cytopathology. Here we have used synthetic virology to clone and manufacture two deletion defective genomes. These genomes were tested with Ebola virus using in vitro cell culture and shown to inhibit viral replication; however, and against expectations, the defective genomes were not released in biologically significant numbers. We propose that EBOV might have yet unknown mechanisms to prevent parasitisation by defective interfering particles beyond the known mechanism that prevents sequential infection of the same cell. Understanding this mechanism would be necessary in any development of a defective interfering particle-based therapy.

Survival and persistence of Nipah virus in blood and tissue culture media.

Nipah virus (NiV) infection is a newly emerging zoonosis that causes severe disease in humans. Nipah virus is one of the lesser studied of the WHO emerging pathogens for which research is a priority. Survival and persistence data is important for risk management and understanding the hazard of the virus for laboratory and health care workers that may work with the virus and we present some initial findings on the survival of Nipah virus in blood and tissue culture media under different conditions. The titre of Nipah virus in blood or media at two different temperatures and exposed or sealed to the atmosphere was measured every day for three days and after a week. Nipah virus was very stable in blood in closed tubes held at room temperature with minimal decay over seven days. Decay was observed in all the other conditions tested and was more rapid in samples exposed to the atmosphere. Persistence data is useful for safety planning and risk management.

Susceptibility and Lethality of Western Equine Encephalitis Virus in Balb/c Mice When Infected by the Aerosol Route.

Western equine encephalitis virus (WEEV) naturally cycles between mosquitos and birds or rodents, with a case fatality rate of up to 15% in humans during epizootic outbreaks. There are no medical countermeasures to treat WEEV infection, and accidental aerosol exposure increases the case fatality rate up to 40%. Understanding the pathogenesis of infection is required to develop and assess medical countermeasures. This study describes the clinical and pathological findings of mice infected with WEEV by the aerosol route, and use as a model for WEEV infection in humans. Balb/c mice were infected by the aerosol route with a dose range of high-virulence WEEV strain Fleming to establish the median lethal dose (MLD). The disease course was acute, culminating in severe clinical signs, neuroinvasion, and dose-dependent mortality. Further groups of mice were exposed by the aerosol route, periodically sacrificed, and tissues excised for histopathological examination and virology. Viral titres peaked four days post-challenge in the brain and lungs, corresponding with severe bilateral lesions in rostroventral regions of the encephalon, especially in the olfactory bulb and piriform cortex. Recapitulation of the most serious clinical presentations of human WEEV disease in mice may prove a useful tool in the evaluation of medical countermeasures.

Effectiveness of Four Disinfectants against Ebola Virus on Different Materials.

The West Africa Ebola virus (EBOV) outbreak has highlighted the need for effective disinfectants capable of reducing viral load in a range of sample types, equipment and settings. Although chlorine-based products are widely used, they can also be damaging to equipment or apparatus that needs continuous use such as aircraft use for transportation of infected people. Two aircraft cleaning solutions were assessed alongside two common laboratory disinfectants in a contact kill assay with EBOV on two aircraft relevant materials representative of a porous and non-porous surface. A decimal log reduction of viral titre of 4 is required for a disinfectant to be deemed effective and two of the disinfectants fulfilled this criteria under the conditions tested. One product, Ardrox 6092, was found to perform similarly to sodium hypochlorite, but as it does not have the corrosive properties of sodium hypochlorite, it could be an alternative disinfectant solution to be used for decontamination of EBOV on sensitive apparatus.

CpG-DNA protects against a lethal orthopoxvirus infection in a murine model.

CpG-DNA has been described as a potent activator of the innate immune system, with potential to protect against infection caused by a range of pathogens in a non-specific manner. Here two classes of CpG-DNA (CpG-A and CpG-B) have been investigated for their abilities to protect mice from infection with an orthopoxvirus (vaccinia virus). Dosing with either CpG-A or B by the intraperitonal or intranasal route protected mice against a subsequent intranasal challenge with vaccinia virus. To our knowledge, this is the first time CpG-mediated protection has been demonstrated at the lung surface. The level of protection was greater when CpG-DNA was administered intranasally demonstrating a clear relationship between the route of CpG dosing and infection route. Treatment with CpG-B reduced viral titer in the lung by 10,000-fold at day 3 post-infection. The CC chemokines RANTES and MIP-1beta were elevated in the broncho-alveolar lavage from animals treated intranasally with CpG-B compared to untreated and intraperitoneally dosed controls, and it is possible that these chemokines play a role in the clearance of intranasally delivered vaccinia virus.

Post-exposure efficacy of oral T-705 (Favipiravir) against inhalational Ebola virus infection in a mouse model.

Filoviruses cause disease with high case fatality rates and are considered biological threat agents. Licensed post-exposure therapies that can be administered by the oral route are desired for safe and rapid distribution and uptake in the event of exposure or outbreaks. Favipiravir or T-705 has broad antiviral activity and has already undergone phase II and is undergoing phase III clinical trials for influenza. Here we report the first use of T-705 against Ebola virus. T-705 gave 100% protection against aerosol Ebola virus E718 infection; protection was shown in immune-deficient mice after 14 days of twice-daily dosing. T-705 was also shown to inhibit Ebola virus infection in cell culture. T-705 is likely to be licensed for use against influenza in the near future and could also be used with a new indication for filovirus infection.