Experimental Inoculation of Pigs with Monkeypox Virus Results in Productive Infection and Transmission to Sentinels.

Monkeypox virus (MPXV) is a re-emerging zoonotic poxvirus responsible for producing skin lesions in humans. Endemic in sub-Saharan Africa, the 2022 outbreak with a clade IIb strain has resulted in ongoing sustained transmission of the virus worldwide. MPXV has a relatively wide host range, with infections reported in rodent and non-human primate species. However, the susceptibility of many domestic livestock species remains unknown. Here, we report on a susceptibility/transmission study in domestic pigs that were experimentally inoculated with a 2022 MPXV clade IIb isolate or served as sentinel contact control animals. Several principal-infected and sentinel contact control pigs developed minor lesions near the lips and nose starting at day 12 through 18 days post-challenge (DPC). No virus was isolated or viral DNA was detected from the lesions; however, MPXV antigen was detected by IHC in tissue from a pustule of a principal infected pig. Viral DNA and infectious virus were detected in nasal and oral swabs up to 14 DPC, with peak titers observed at 7 DPC. Viral DNA was also detected in nasal tissues or skin collected from two principal-infected animals at 7 DPC post-mortem. Furthermore, all principal-infected and sentinel control animals enrolled in the study seroconverted. In conclusion, we provide the first evidence that domestic pigs are susceptible to experimental MPXV infection and can transmit the virus to contact animals.

Experimental co-infection of calves with SARS-CoV-2 Delta and Omicron variants of concern.

Since emerging in late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has repeatedly crossed the species barrier with natural infections reported in various domestic and wild animal species. The emergence and global spread of SARS-CoV-2 variants of concern (VOCs) has expanded the range of susceptible host species. Previous experimental infection studies in cattle using Wuhan-like SARS-CoV-2 isolates suggested that cattle were not likely amplifying hosts for SARS-CoV-2. However, SARS-CoV-2 sero- and RNA-positive cattle have since been identified in Europe, India, and Africa. Here, we investigated the susceptibility and transmission of the Delta and Omicron SARS-CoV-2 VOCs in cattle. Eight Holstein calves were co-infected orally and intranasally with a mixed inoculum of SARS-CoV-2 VOCs Delta and Omicron BA.2. Twenty-four hours post-challenge, two sentinel calves were introduced to evaluate virus transmission. The co-infection resulted in a high proportion of calves shedding SARS-CoV-2 RNA at 1- and 2-days post-challenge (DPC). Extensive tissue distribution of SARS-CoV-2 RNA was observed at 3 and 7 DPC and infectious virus was recovered from two calves at 3 DPC. Next-generation sequencing revealed that only the SARS-CoV-2 Delta variant was detected in clinical samples and tissues. Similar to previous experimental infection studies in cattle, we observed only limited seroconversion and no clear evidence of transmission to sentinel calves. Together, our findings suggest that cattle are more permissive to infection with SARS-CoV-2 Delta than Omicron BA.2 and Wuhan-like isolates but, in the absence of horizontal transmission, are not likely to be reservoir hosts for currently circulating SARS-CoV-2 variants.

The roles of XJ13 and XJ44-specific mutations within the Candid #1 GPC in Junin virus attenuation.

Junin virus (JUNV) is a member of the Arenaviridae family of viruses and is the pathogen responsible for causing Argentine hemorrhagic fever, a potentially lethal disease endemic to Argentina. A live attenuated vaccine for human use, called Candid#1, is approved only in Argentina. Candid#1 vaccine strain of Junin virus was obtained through serial passage in mouse brain tissues followed by passage in Fetal Rhesus macaque lung fibroblast (FRhL) cells. Previously, the mutations responsible for attenuation of this virus in Guinea pigs were mapped in the gene encoding for glycoprotein precursor (GPC) protein. The resulting Candid#1 glycoprotein complex has been shown to cause endoplasmic reticulum (ER) stress in vitro resulting in the degradation of the GPC. To evaluate the attenuating properties of specific mutations within GPC, we created recombinant viruses expressing GPC mutations specific to key Candid#1 passages and evaluated their pathogenicity in our outbred Hartley guinea pig model of Argentine hemorrhagic fever. Here, we provide evidence that early mutations in GPC obtained through serial passaging attenuate the visceral disease and increase immunogenicity in guinea pigs. Specific mutations acquired prior to the 13th mouse brain passage (XJ13) are responsible for attenuation of the visceral disease while having no impact on the neurovirulence of Junin virus. Additionally, our findings demonstrate that the mutation within an N-linked glycosylation motif, acquired prior to the 44th mouse brain passage (XJ44), is unstable but necessary for complete attenuation and enhanced immunogenicity of Candid#1 vaccine strain. The highly conserved N-linked glycosylation profiles of arenavirus glycoproteins could therefore be viable targets for designing attenuating viruses for vaccine development against other arenavirus-associated illnesses.

Lassa virus NP DEDDh 3'-5' exoribonuclease activity is required for optimal viral RNA replication and mutation control.

Lassa virus (LASV), a mammarenavirus from Arenaviridae, is the causative agent of Lassa fever (LF) endemic in West Africa. Currently, there are no vaccines or antivirals approved for LF. The RNA-dependent RNA polymerases (RdRp) of RNA viruses are error-prone. As a negative-sense RNA virus, how LASV copes with errors in RNA synthesis and ensures optimal RNA replication are not well elucidated. LASV nucleoprotein (NP) contains a DEDDH 3'-to-5' exoribonuclease motif (ExoN), which is known to be essential for LASV evasion of the interferon response via its ability to degrade virus-derived double-stranded RNA. Herein, we present evidence that LASV NP ExoN has an additional function important for viral RNA replication. We rescued an ExoN-deficient LASV mutant (ExoN- rLASV) by using a reverse genetics system. Our data indicated that abrogation of NP ExoN led to impaired LASV growth and RNA replication in interferon-deficient cells as compared with wild-type rLASV. By utilizing PacBio Single Molecule, Real-Time (SMRT) long-read sequencing technology, we found that rLASV lacking ExoN activity was prone to producing aberrant viral genomic RNA with structural variations. In addition, NP ExoN deficiency enhanced LASV sensitivity to mutagenic nucleoside analogues in virus titration assay. Next-generation deep sequencing analysis showed increased single nucleotide substitution in ExoN- LASV RNA following mutagenic 5-flurouracil treatment. In conclusion, our study revealed that LASV NP ExoN is required for efficient viral RNA replication and mutation control. Among negative-sense RNA viruses, LASV NP is the first example that a viral protein, other than the RdRp, contributes to reduce errors in RNA replication and maintain genomic RNA integrity. These new findings promote our understanding of the basics of LASV infection and inform antiviral and vaccine development.

Depletion of CD4 and CD8 T Cells Reduces Acute Disease and Is Not Associated with Hearing Loss in ML29-Infected STAT1-/- Mice.

Lassa virus (LASV) is a zoonotic virus endemic to western Africa that can cause a potentially lethal and hemorrhagic disease, Lassa fever (LF). Survivors suffer a myriad of sequelae, most notably sudden onset sensorineural hearing loss (SNHL), the mechanism of which remains unclear. Unfortunately, studies aiming to identify the mechanism of these sequelae are limited due to the biosafety level 4 (BSL4) requirements of LASV itself. ML29, a reassortant virus proposed as an experimental vaccine candidate against LASV, is potentially an ideal surrogate model of LF in STAT1-/- mice due to similar phenotype in these animals. We intended to better characterize ML29 pathogenesis and potential sequelae in this animal model. Our results indicate that while both CD4 and CD8 T cells are responsible for acute disease in ML29 infection, ML29 induces significant hearing loss in a mechanism independent of either CD4 or CD8 T cells. We believe that this model could provide valuable information for viral-associated hearing loss in general.

Machupo Virus with Mutations in the Transmembrane Domain and Glycosylation Sites of the Glycoprotein Is Attenuated and Immunogenic in Animal Models of Bolivian Hemorrhagic Fever.

Several highly pathogenic mammarenaviruses cause severe hemorrhagic and neurologic disease in humans for which vaccines and antivirals are limited or unavailable. New World (NW) mammarenavirus Machupo virus (MACV) infection causes Bolivian hemorrhagic fever in humans. We previously reported that the disruption of specific N-linked glycan sites on the glycoprotein (GPC) partially attenuates MACV in an interferon alpha/beta and gamma (IFN-α/ß and -γ) receptor knockout (R-/-) mouse model. However, some capability to induce neurological pathology still remained. The highly pathogenic Junin virus (JUNV) is another NW arenavirus closely related to MACV. An F427I substitution in the GPC transmembrane domain (TMD) rendered JUNV attenuated in a lethal mouse model after intracranial inoculation. In this study, we rationally designed and rescued a MACV containing mutations at two glycosylation sites and the corresponding F438I substitution in the GPC TMD. The MACV mutant is fully attenuated in IFN-α/ß and -γ R-/- mice and outbred guinea pigs. Furthermore, inoculation with this mutant MACV completely protected guinea pigs from wild-type MACV lethal challenge. Last, we found the GPC TMD F438I substitution greatly impaired MACV growth in neuronal cell lines of mouse and human origins. Our results highlight the critical roles of the glycans and the TMD on the GPC in arenavirus virulence, which provide insight into the rational design of potential vaccine candidates for highly pathogenic arenaviruses. IMPORTANCE For arenaviruses, the only vaccine available is the live attenuated Candid#1 vaccine, a JUNV vaccine approved in Argentina. We and others have found that the glycans on GPC and the F427 residue in the GPC TMD are important for virulence of JUNV. Nevertheless, mutating either of them is not sufficient for full and stable attenuation of JUNV. Using reverse genetics, we disrupted specific glycosylation sites on MACV GPC and also introduced the corresponding F438I substitution in the GPC TMD. This MACV mutant is fully attenuated in two animal models and protects animals from lethal infection. Thus, our studies highlight the feasibility of rational attenuation of highly pathogenic arenaviruses for vaccine development. Another important finding from this study is that the F438I substitution in GPC TMD could substantially affect MACV replication in neurons. Future studies are warranted to elucidate the underlying mechanism and the implication of this mutation in arenavirus neural tropism.

Luminore CopperTouch Surface Coating Effectively Inactivates SARS-CoV-2, Ebola Virus, and Marburg Virus In Vitro.

We investigated the ability of Luminore CopperTouch copper and copper-nickel surfaces to inactivate filoviruses and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The copper and copper-nickel surfaces inactivated 99.9% of Ebola and Marburg viruses after 30 min, and the copper surfaces inactivated 99% of SARS-CoV-2 in 2 h. These data reveal that Ebola virus, Marburg virus, and SARS-CoV-2 are inactivated by exposure to copper ions, validating Luminore CopperTouch as an efficacious tool for infection control.

In vitro efficacy of a copper iodine complex PPE disinfectant for SARS-CoV-2 inactivation.

Background: The ability to protect workers and healthcare professionals from infection by SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is of great concern. Hospitals, nursing homes and employers are adopting infection control strategies based on guidance from leading public health organizations such as the CDC, OSHA, FDA, and other government bodies. Certain hard surface disinfectants are effective against SARS-CoV-2 but are not suitable for use on skin or personal protective equipment (PPE) that comes into contact with skin. Furthermore, near-ubiquitous alcohol-based hand sanitizers are acceptable for use on skin, but they are not suitable for use on PPE. PPE, especially masks, are also commonly being used for longer durations than normal. There is a need for new products and techniques that can effectively disinfect PPE during wear time without having detrimental effects on surrounding skin. Clyraguard spray is a novel copper iodine complex designed to be used on non-critical PPE. Methods: In this study, the Clyraguard copper iodine complex was tested for its ability to inactivate SARS-CoV-2 in solution. Results: These data indicate the product to be effective in reducing SARS-CoV-2 titers in a time-dependent manner, with the virus being reduced below the detection limits within 30 minutes. Conclusions: These results suggest that Clyraguard may be an effective tool for mitigating cross-contamination of non-critical PPE that may come into contact with SARS-CoV-2.

Enterobacterales Infection after Intestinal Dominance in Hospitalized Patients.

The Enterobacterales order of Gram-negative bacteria includes the common nosocomial pathogens Klebsiella pneumoniae, Escherichia coli, Serratia marcescens, and Enterobacter species. Intestinal domination by some colonizing bacterial taxa is associated with subsequent infection, but 16S rRNA gene sequencing is too costly and slow to be used in a clinical setting. The objectives of this study were to develop a PCR-based assay that can measure Enterobacterales density, validate it against 16S rRNA gene sequencing, and measure the association between Enterobacterales dominance and subsequent infection. Two quantitative PCR (qPCR) assays that were developed to quantify the absolute and relative abundance of Enterobacterales had good correlation with 16S rRNA sequence analysis (P < 0.0001). Using both PCR assays and 16S sequencing, a matched case-control study was performed comparing rectal swabs from hospitalized patients who later developed bloodstream, urinary tract, or respiratory Enterobacterales infections (n = 95) to swabs from patients who remained uninfected (n = 189). Enterobacterales abundance measured by sequencing was high in both cases and controls (means, 31.1% and 27.5%, respectively; P = 0.322). We observed an increased risk of infection that depended on both the absolute and relative abundance of Enterobacterales as measured by qPCR assay A (P = 0.012). After adjustment for albumin levels, central venous catheter presence, and use of cephalosporins at the time of swab collection, this association still approached significance (P = 0.061). These results demonstrate that using qPCR to measure intestinal colonization dominance is feasible, indicate that hospitalized patients have high levels of Enterobacterales colonization, and suggest that both relative and absolute abundance may be associated with subsequent infection.IMPORTANCE Increasing antibiotic resistance has resulted in infections that are life-threatening and difficult to treat. Interventions that prevent these infections, particularly without using antibiotics, could save lives. Intestinal colonization by pathogens, including vancomycin-resistant Enterococcus and carbapenem-resistant Enterobacteriaceae (part of the order Enterobacterales) is associated with subsequent infection, and increased colonization density is associated with increased infection risk. Therefore, colonization offers a window of opportunity for infection prevention if (i) there are rapid and inexpensive assays to detect colonization, (ii) there are safe and effective interventions, and (iii) the risk of infection outweighs the risk of the treatment. Fecal transplants are proof of principle that manipulating the microbiome can reduce such colonization and prevent infections. This study demonstrates the feasibility of implementing rapid and inexpensive assays to quantify colonization and measures the strength of association between Enterobacterales dominance and subsequent infection. The approach described here could be a valuable tool in the prevention of antibiotic-resistant infections.

Luminore CopperTouch™ surface coating effectively inactivates SARS-CoV-2, Ebola and Marburg viruses in vitro.

We investigated the ability of Luminore CopperTouch™ copper and copper-nickel surfaces to inactivate filoviruses and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). For this purpose, we compared viral titers in Vero cells from viral droplets exposed to copper surfaces for 30 min. The copper and copper-nickel surfaces inactivated 99.9% of the viral titer of both Ebola and Marburg viruses. The copper surfaces also inactivated 99% of SARS-CoV-2 titers in 2 hours to close to the limit of detection. These data add Ebolavirus, Marburgvirus, and SARS-CoV-2 (COVID-19) to the list of pathogens that can be inactivated by exposure to copper ions, validating Luminore CopperTouch™ technology (currently the only Environmental Protection Agency [EPA]-registered cold spray antimicrobial surface technology) as an efficacious, cost-friendly tool to improve infection control in hospitals, long-term care facilities, schools, hotels, buses, trains, airports, and other highly trafficked areas.

Potent Antiviral Activities of Type I Interferons to SARS-CoV-2 Infection.

The historical outbreak of COVID-19 disease not only constitutes a global public health crisis, but also has a devastating social and economic impact. The disease is caused by a newly identified coronavirus, Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2). There is an urgent need to identify antivirals to curtail the COVID-19 pandemic. Herein, we report the remarkable sensitivity of SARS-CoV-2 to recombinant human interferons α and ß (IFNα/ß). Treatment with IFN-α or IFN-ß at a concentration of 50 international units (IU) per milliliter drastically reduce viral titers by 3.4 log or 4.5 log, respectively in Vero cells. The EC50 of IFN-α and IFN-ß treatment is 1.35 IU/ml and 0.76 IU/ml, respectively, in Vero cells. These results suggested that SARS-CoV-2 is more sensitive to many other human pathogenic viruses, including the SARS-CoV. Overall, our results demonstrate the potent efficacy of human Type I IFN in suppressing SARS-CoV-2 replication, a finding which could inform future treatment options for COVID-19.

Efficacy of a novel iodine complex solution, CupriDyne, in inactivating SARS-CoV-2.

The coronavirus known as SARS-CoV-2, which causes COVID-19 disease, is presently responsible for a global pandemic wherein more than 3.5 million people have been infected and more than 250,000 killed to-date. There is currently no vaccine for COVID-19, leaving governments and public health agencies with little defense against the virus aside from advising or enforcing best practices for virus transmission prevention, which include hand-washing, physical distancing, use of face covers, and use of effective disinfectants. In this study, a novel iodine complex called CupriDyne® was assessed for its ability to inactivate SARS-CoV-2. CupriDyne was shown to be effective in inactivating the virus in a time-dependent manner, reducing virus titers by 99% (2 logs) after 30 minutes, and reducing virus titers to below the detection limit after 60 minutes. The novel iodine complex tested herein offers a safe and gentle alternative to conventional disinfectants for use on indoor and outdoor surfaces.

Antiviral activities of type I interferons to SARS-CoV-2 infection.

There is an urgent need to identify antivirals to curtail the COVID-19 pandemic. Herein, we report the sensitivity of SARS-CoV-2 to recombinant human interferons α and ß (IFNα/ß). Treatment with IFN-α or IFN-ß at a concentration of 50 international units (IU) per milliliter reduces viral titers by 3.4 log or over 4 log, respectively, in Vero cells. The EC50 of IFN-α and IFN-ß treatment is 1.35 IU/ml and 0.76 IU/ml, respectively, in Vero cells. These results suggest that SARS-CoV-2 is more sensitive than many other human pathogenic viruses, including SARS-CoV. Overall, our results demonstrate the potential efficacy of human Type I IFN in suppressing SARS-CoV-2 infection, a finding which could inform future treatment options for COVID-19.

Differential Immune Responses to Hemorrhagic Fever-Causing Arenaviruses.

The family Arenaviridae contains several pathogens of major clinical importance. The Old World (OW) arenavirus Lassa virus is endemic in West Africa and is estimated to cause up to 300,000 infections each year. The New World (NW) arenaviruses Junín and Machupo periodically cause hemorrhagic fever outbreaks in South America. While these arenaviruses are highly pathogenic in humans, recent evidence indicates that pathogenic OW and NW arenaviruses interact with the host immune system differently, which may have differential impacts on viral pathogenesis. Severe Lassa fever cases are characterized by profound immunosuppression. In contrast, pathogenic NW arenavirus infections are accompanied by elevated levels of Type I interferon and pro-inflammatory cytokines. This review aims to summarize recent findings about interactions of these pathogenic arenaviruses with the innate immune machinery and the subsequent effects on adaptive immunity, which may inform the development of vaccines and therapeutics against arenavirus infections.

Virtual Screen for Repurposing of Drugs for Candidate Influenza a M2 Ion-Channel Inhibitors.

Influenza A virus (IAV) matrix protein 2 (M2), an ion channel, is crucial for virus infection, and therefore, an important anti-influenza drug target. Adamantanes, also known as M2 channel blockers, are one of the two classes of Food and Drug Administration-approved anti-influenza drugs, although their use was discontinued due to prevalent drug resistance. Fast emergence of resistance to current anti-influenza drugs have raised an urgent need for developing new anti-influenza drugs against resistant forms of circulating viruses. Here we propose a simple theoretical criterion for fast virtual screening of molecular libraries for candidate anti-influenza ion channel inhibitors both for wild type and adamantane-resistant influenza A viruses. After in silico screening of drug space using the EIIP/AQVN filter and further filtering of drugs by ligand based virtual screening and molecular docking we propose the best candidate drugs as potential dual inhibitors of wild type and adamantane-resistant influenza A viruses. Finally, guanethidine, the best ranked drug selected from ligand-based virtual screening, was experimentally tested. The experimental results show measurable anti-influenza activity of guanethidine in cell culture.

In vitro anti-influenza activity of in silico repurposed candidate drug cycrimine.

BACKGROUND: Due to the limitations of current antiviral therapies because of drug resistance and the emergence of new circulating viral strains, novel effective antivirals are urgently needed. Results of the previous drug repurposing by virtual screening of DrugBank revealed the anticholinergic drug cycrimine as a possible inhibitor of the influenza virus infection. METHODS: In this study we examined the potential antiviral activity of cycrimine in vitro. RESULTS: The experimental results showed the anti-influenza activity of cycrimine against two different influenza A subtypes in cell culture. CONCLUSIONS: The findings of this study suggest cycrimine as a potential therapeutic agent for influenza.

Vaccination has minimal impact on the intrahost diversity of H3N2 influenza viruses.

While influenza virus diversity and antigenic drift have been well characterized on a global scale, the factors that influence the virus' rapid evolution within and between human hosts are less clear. Given the modest effectiveness of seasonal vaccination, vaccine-induced antibody responses could serve as a potent selective pressure for novel influenza variants at the individual or community level. We used next generation sequencing of patient-derived viruses from a randomized, placebo-controlled trial of vaccine efficacy to characterize the diversity of influenza A virus and to define the impact of vaccine-induced immunity on within-host populations. Importantly, this study design allowed us to isolate the impact of vaccination while still studying natural infection. We used pre-season hemagglutination inhibition and neuraminidase inhibition titers to quantify vaccine-induced immunity directly and to assess its impact on intrahost populations. We identified 166 cases of H3N2 influenza over 3 seasons and 5119 person-years. We obtained whole genome sequence data for 119 samples and used a stringent and empirically validated analysis pipeline to identify intrahost single nucleotide variants at ≥1% frequency. Phylogenetic analysis of consensus hemagglutinin and neuraminidase sequences showed no stratification by pre-season HAI and NAI titer, respectively. In our study population, we found that the vast majority of intrahost single nucleotide variants were rare and that very few were found in more than one individual. Most samples had fewer than 15 single nucleotide variants across the entire genome, and the level of diversity did not significantly vary with day of sampling, vaccination status, or pre-season antibody titer. Contrary to what has been suggested in experimental systems, our data indicate that seasonal influenza vaccination has little impact on intrahost diversity in natural infection and that vaccine-induced immunity may be only a minor contributor to antigenic drift at local scales.