Novel poxvirus infection in 2 patients from the United States

Equine dermatitis outbreak associated with parapoxvirus

Parapoxviruses (PPV) cause skin and mucous membrane lesions in several animal species, and of the five recognized PPVs, at least three are zoonotic. Equine PPV (EqPPV) is the sixth one initially described in humans in the United States and later in a severely sick horse in Finland in 2013-2015. In 2021-2022, a large-scale pustulo-vesicular pastern dermatitis outbreak occurred in horses all over Finland. This study aimed at analysing the outbreak, identifying and describing the causative agent, describing clinical signs, and searching for risk factors. EqPPV was identified as a probable causative agent and co-infections with several potentially pathogenic and zoonotic bacteria were observed. Histopathologically, suppurative and ulcerative dermatitis was diagnosed. Due to the lack of specific tests for this virus, we developed a novel diagnostic EqPPV-PCR with sensitivity of 10 copies/reaction. Based on a large proportion of the genome sequenced directly from clinical samples, very little variation was detected between the sequences of the case from 2013 and the cases from 2021 to 2022. Based on an epidemiological survey, the main risk factor for pastern dermatitis was having racehorses. Approximately one third of the horses at each affected stable got clinical dermatitis, manifesting as severe skin lesions. Skin lesions were also occasionally reported in humans, indicating potential zoonotic transmission. Case stables commonly reported attendance at race events before acquiring the disease. Survey also identified differences in practises between case and control stables. Taken together, these results enable a better preparedness, diagnostics, and guidelines for future outbreaks.

Partial Genome Characterization of Novel Parapoxvirus in Horse, Finland

We report a sequencing protocol and 121-kb poxvirus sequence from a clinical sample from a horse in Finland with dermatitis. Based on phylogenetic analyses, the virus is a novel parapoxvirus associated with a recent epidemic; previous data suggest zoonotic potential. Increased awareness of this virus and specific diagnostic protocols are needed.

Laboratory Infection of Novel Akhmeta Virus in CAST/EiJ Mice

Akhmeta virus is a zoonotic Orthopoxvirus first identified in 2013 in the country of Georgia. Subsequent ecological investigations in Georgia have found evidence that this virus is widespread in its geographic distribution within the country and in its host-range, with rodents likely involved in its circulation in the wild. Yet, little is known about the pathogenicity of this virus in rodents. We conducted the first laboratory infection of Akhmeta virus in CAST/EiJ Mus musculus to further characterize this novel virus. We found a dose-dependent effect on mortality and weight loss (p < 0.05). Anti-orthopoxvirus antibodies were detected in the second- and third-highest dose groups (5 × 10⁴ pfu and 3 × 10² pfu) at euthanasia by day 10, and day 14 post-infection, respectively. Anti-orthopoxvirus antibodies were not detected in the highest dose group (3 × 10⁶ pfu), which were euthanized at day 7 post-infection and had high viral load in tissues, suggesting they succumbed to disease prior to mounting an effective immune response. In order of highest burden, viable virus was detected in the nostril, lung, tail, liver and spleen. All individuals tested in the highest dose groups were DNAemic. Akhmeta virus was highly pathogenic in CAST/EiJ Mus musculus, causing 100% mortality when ≥3 × 10² pfu was administered.

Genomic Features and Evolution of the Parapoxvirus during the Past Two Decades

Parapoxvirus (PPV) has been identified in some mammals and poses a great threat to both the livestock production and public health. However, the prevalence and evolution of this virus are still not fully understood. Here, we performed an in silico analysis to investigate the genomic features and evolution of PPVs. We noticed that although there were significant differences of GC contents between orf virus (ORFV) and other three species of PPVs, all PPVs showed almost identical nucleotide bias, that is GC richness. The structural analysis of PPV genomes showed the divergence of different PPV species, which may be due to the specific adaptation to their natural hosts. Additionally, we estimated the phylogenetic diversity of seven different genes of PPV. According to all available sequences, our results suggested that during 2010–2018, ORFV was the dominant virus species under the selective pressure of the optimal gene patterns. Furthermore, we found the substitution rates ranged from 3.56 × 10⁻⁵ to 4.21 × 10⁻⁴ in different PPV segments, and the PPV VIR gene evolved at the highest substitution rate. In these seven protein-coding regions, purifying selection was the major evolutionary pressure, while the GIF and VIR genes suffered the greatest positive selection pressure. These results may provide useful knowledge on the virus genetic evolution from a new perspective which could help to create prevention and control strategies.

Molecular and genomic characterization of a novel equine molluscum contagiosum-like virus

Cases of pox-like lesions in horses and donkeys have been associated with poxviruses belonging to different genera of the family Poxviridae. These include the orthopoxviruses vaccinia virus (VACV), horsepoxvirus (HPXV) and cowpoxvirus (CPXV), as well as a potentially novel parapoxvirus and molluscum contagiosum virus (MOCV). However, with the exception of VACV, HPXV and CPXV, the genomic characterization of the causative agents remains largely elusive with only single short genome fragments available. Here we present the first full-length genome sequence of an equine molluscum contagiosum-like virus (EMCLV) directly determined from skin biopsies of a horse with generalized papular dermatitis. Histopathological analysis of the lesions revealed severe epidermal hyperplasia with numerous eosinophilic inclusion bodies within keratinocytes. Virions were detected in the lesions in embedded tissue by transmission electron microscopy. The genome sequence determined by next- and third-generation sequencing comprises 166 843 nt with inverted terminal repeats (ITRs) of 3473 nt. Overall, 20 of the predicted 159 ORFs have no equivalents in other poxviruses. Intriguingly, two of these ORFs were identified to encode homologues of mammalian proteins involved in immune signalling pathways, namely secreted and transmembrane protein 1 (SECTM1) and insulin growth factor-like family receptor 1 (IGFLR1), that were not described in any virus family so far. Phylogenetic analysis with all relevant representatives of the Poxviridae suggests that EMCLV should be nominated as a new species within the genus Molluscipoxvirus.

Isolation and Characterization of Akhmeta Virus from Wild-Caught Rodents (Apodemus spp.) in Georgia

Akhmeta virus is a unique Orthopoxvirus that was described in 2013 from the country of Georgia. This paper presents the first isolation of this virus from small mammal (Rodentia; Apodemus spp.) samples and the molecular characterization of those isolates. The identification of the virus in small mammals is an essential component to understanding the natural history of this virus and its transmission to human populations and could guide public health interventions in Georgia. Akhmeta virus genomes harbor evidence suggestive of recombination with a variety of other orthopoxviruses; this has implications for the evolution of orthopoxviruses, their ability to infect mammalian hosts, and their ability to adapt to novel host species.

In 2013, a novel orthopoxvirus was detected in skin lesions of two cattle herders from the Kakheti region of Georgia (country); this virus was named Akhmeta virus. Subsequent investigation of these cases revealed that small mammals in the area had serological evidence of orthopoxvirus infections, suggesting their involvement in the maintenance of these viruses in nature. In October 2015, we began a longitudinal study assessing the natural history of orthopoxviruses in Georgia. As part of this effort, we trapped small mammals near Akhmeta (n = 176) and Gudauri (n = 110). Here, we describe the isolation and molecular characterization of Akhmeta virus from lesion material and pooled heart and lung samples collected from five wood mice (Apodemus uralensis and Apodemus flavicollis) in these two locations. The genomes of Akhmeta virus obtained from rodents group into 2 clades: one clade represented by viruses isolated from A. uralensis samples, and one clade represented by viruses isolated from A. flavicollis samples. These genomes also display several presumptive recombination events for which gene truncation and identity have been examined.

IMPORTANCE Akhmeta virus is a unique Orthopoxvirus that was described in 2013 from the country of Georgia. This paper presents the first isolation of this virus from small mammal (Rodentia; Apodemus spp.) samples and the molecular characterization of those isolates. The identification of the virus in small mammals is an essential component to understanding the natural history of this virus and its transmission to human populations and could guide public health interventions in Georgia. Akhmeta virus genomes harbor evidence suggestive of recombination with a variety of other orthopoxviruses; this has implications for the evolution of orthopoxviruses, their ability to infect mammalian hosts, and their ability to adapt to novel host species.

Genome of Alaskapox Virus, A Novel Orthopoxvirus Isolated from Alaska

Since the eradication of smallpox, there have been increases in poxvirus infections and the emergence of several novel poxviruses that can infect humans and domestic animals. In 2015, a novel poxvirus was isolated from a resident of Alaska. Diagnostic testing and limited sequence analysis suggested this isolate was a member of the Orthopoxvirus (OPXV) genus but was highly diverged from currently known species, including Akhmeta virus. Here, we present the complete 210,797 bp genome sequence of the Alaska poxvirus isolate, containing 206 predicted open reading frames. Phylogenetic analysis of the conserved central region of the genome suggested the Alaska isolate shares a common ancestor with Old World OPXVs and is diverged from New World OPXVs. We propose this isolate as a member of a new OPXV species, Alaskapox virus (AKPV). The AKPV genome contained host range and virulence genes typical of OPXVs but lacked homologs of C4L and B7R, and the hemagglutinin gene contained a unique 120 amino acid insertion. Seven predicted AKPV proteins were most similar to proteins in non-OPXV Murmansk or NY_014 poxviruses. Genomic analysis revealed evidence suggestive of recombination with Ectromelia virus in two putative regions that contain seven predicted coding sequences, including the A-type inclusion protein.

PREVALENCE OF ANTIBODIES TO ORTHOPOXVIRUS IN WILD CARNIVORES OF NORTHWESTERN CHIHUAHUA, MEXICO

The distribution of orthopoxviruses (OPXVs) across the North American continent is suggested to be widespread in a wide range of mammalian hosts on the basis of serosurveillance studies. To address the question of whether carnivores in northwestern Mexico are exposed to naturally circulating OPXVs, wild carnivores were collected by live trapping within four different habitat types during fall of 2013 and spring of 2014 within the Janos Biosphere Reserve in northwestern Chihuahua, Mexico. A total of 51 blood samples was collected for testing. Anti-OPXV immunoglobulin G enzymelinked immunosorbent assay, western blot, and rapid fluorescent focus inhibition test (RFFIT) assays were conducted. About 47% (24/51) of the carnivores tested were seropositive for anti-OPXV binding antibodies and had presence of immunodominant bands indicative of OPXV infection. All samples tested were negative for rabies virus neutralizing antibodies by RFFIT, suggesting that the OPXV antibodies were due to circulating OPXV, and not from exposure to oral rabies vaccine (vacciniavectored rabies glycoprotein vaccine) bait distributed along the US-Mexico border. Our results indicated that there may be one or more endemic OPXV circulating within six species of carnivores in northwestern Mexico.

Virus detection by transmission electron microscopy: Still useful for diagnosis and a plus for biosafety

Transmission electron microscopy (TEM) is the only imaging technique allowing the direct visualization of viruses, due to its nanometer‐scale resolution. Between the 1960s and 1990s, TEM contributed to the discovery of many types of viruses and served as a diagnostic tool for identifying viruses directly in biological samples, either in suspension or in sections of tissues or mammalian cells grown in vitro in contact with clinical samples. The diagnosis of viral infections improved considerably during the 1990s, with the advent of highly sensitive techniques, such as enzyme‐linked immunosorbent assay (ELISA) and PCR, rendering TEM obsolete for this purpose. However, the last 20 years have demonstrated the utility of this technique in particular situations, due to its “catch‐all” nature, making diagnosis possible through visualization of the virus, without the need of prior assumptions about the infectious agent sought. Thus, in several major outbreaks in which molecular techniques failed to identify the infectious agent, TEM provided the answer. TEM is also still occasionally used in routine diagnosis to characterize infections not diagnosed by molecular assays. It is also used to check the microbiological safety of biological products. Many biopharmaceuticals are produced in animal cells that might contain little‐known, difficult‐to‐detect viruses. In this context, the “catch‐all” properties of TEM make it possible to document the presence of viruses or virus‐like particles in these products.

Parapoxvirus Infections in the Country of Georgia: A Case Series

Infections caused by viruses of the parapoxvirus (PPV) genus, including orf and pseudocowpox viruses, are frequently seen in both humans and animals in many regions of the world. These infections are often misdiagnosed or neglected because of the lack of clinician awareness, inadequate diagnostic capacity, and their relatively mild disease presentation, which may result in affected individuals not seeking medical attention. Although PPV infections should be routinely considered in patients with cutaneous lesions, especially in those who have occupational exposure to farm animals, they are often excluded from the differential diagnosis because they are not perceived as serious, resulting in underestimation of the burden of disease. Since 2014, significant enhancements to Georgia's epidemiologic and laboratory capacity have made PPV surveillance and detection possible. In this study, we present information on 27 confirmed cases of PPV infection reported to Georgia's national surveillance system from January 2016 through January 2017.

Novel Orthopoxvirus Infection in an Alaska Resident

Background.

Human infection by orthopoxviruses is being reported with increasing frequency, attributed in part to the cessation of smallpox vaccination and concomitant waning of population-level immunity. In July 2015, a female resident of interior Alaska presented to an urgent care clinic with a dermal lesion consistent with poxvirus infection. Laboratory testing of a virus isolated from the lesion confirmed infection by an Orthopoxvirus.

Methods.

The virus isolate was characterized by using electron microscopy and nucleic acid sequencing. An epidemiologic investigation that included patient interviews, contact tracing, and serum testing, as well as environmental and small-mammal sampling, was conducted to identify the infection source and possible additional cases.

Results.

Neither signs of active infection nor evidence of recent prior infection were observed in any of the 4 patient contacts identified. The patient's infection source was not definitively identified. Potential routes of exposure included imported fomites from Azerbaijan via the patient's cohabiting partner or wild small mammals in or around the patient's residence. Phylogenetic analyses demonstrated that the virus represents a distinct and previously undescribed genetic lineage of Orthopoxvirus, which is most closely related to the Old World orthopoxviruses.

Conclusions.

Investigation findings point to infection of the patient after exposure in or near Fairbanks. This conclusion raises questions about the geographic origins (Old World vs North American) of the genus Orthopoxvirus. Clinicians should remain vigilant for signs of poxvirus infection and alert public health officials when cases are suspected.

The Host Restriction Factor Interferon-Inducible Transmembrane Protein 3 Inhibits Vaccinia Virus Infection

Interferons (IFNs) establish dynamic host defense mechanisms by inducing various IFN-stimulated genes that encodes many antiviral innate immune effectors. IFN-inducible transmembrane (IFITM) proteins have been identified as intrinsic antiviral effectors, which block the entry of a broad spectrum of enveloped RNA viruses by interrupting virus-endosomal fusion. However, antiviral activity of IFITM proteins against mammalian DNA virus has not been demonstrated till date. Here, we sought to investigate the antiviral activities and mechanisms of interferon-inducible transmembrane protein 3 (IFITM3) protein against poxvirus infection. Analysis of expression kinetics of cell endogenous IFITM3 protein indicated that vaccinia virus (VACV) infection suppressed its translation, which was independent of IRF3 phosphorylation triggered by VACV. Although silencing of endogenous IFITM proteins did not affect their baseline antiviral effects in the cell, it has reduced the IFN-α-mediated inhibition of VACV infection, and also modulated VACV-induced cell death. Moreover, we discovered that overexpression of IFITM3 significantly restricted VACV infection, replication and proliferation mainly by interfering with virus entry processes prior to the virus nucleocapsid entry into the cytoplasm. Interestingly, IFITM3 overexpression showed an impact on virus binding. Furthermore, IFITM3 interfered with the cytosolic entry of virus through low pH-dependent fashion. Taken together, our findings provide the first evidence of exogenously expressed IFITM3 protein restricting infection of an enveloped DNA virus, thus expanding their antiviral spectrum. This study further explores the complex mechanism and provides novel insights into the interaction between virus infection and host defense.

Infection with Possible Novel Parapoxvirus in Horse, Finland, 2013

A horse in Finland exhibited generalized granulomatous inflammation and severe proliferative dermatitis. After euthanization, we detected poxvirus DNA from a skin lesion sample. The virus sequence grouped with parapoxviruses, closely resembling a novel poxvirus detected in humans in the United States after horse contact. Our findings indicate horses may be a reservoir for zoonotic parapoxvirus.

Unique Presentation of Orf Virus Infection in a Thermal-Burn Patient After Receiving an Autologous Skin Graft

We describe a burn patient who developed skin lesions on her skin-graft harvest and skin-graft recipient (burn) sites. Orf virus infection was confirmed by a combination of diagnostic assays, including molecular tests, immunohistochemical analysis, pathologic analysis, and electron microscopy. DNA sequence analysis grouped this orf virus isolate among isolates from India. Although no definitive source of infection was determined from this case, this is the first reported case of orf virus infection in a skin graft harvest. Skin graft recipients with exposures to animals may be at risk for this viral infection.

Defending against smallpox: a focus on vaccines

Smallpox has shaped human history, from the earliest human civilizations well into the 20th century. With high mortality rates, rapid transmission, and serious long-term effects on survivors, smallpox was a much-feared disease. The eradication of smallpox represents an unprecedented medical victory for the lasting benefit of human health and prosperity. Concerns remain, however, about the development and use of the smallpox virus as a biological weapon, which necessitates the need for continued vaccine development. Smallpox vaccine development is thus a much-reviewed topic of high interest. This review focuses on the current state of smallpox vaccines and their context in biodefense efforts.