Fast and reliable diagnostic methods for the detection of human poxvirus infections

Biological Characteristics and Pathogenesis of Monkeypox Virus: An Overview

Although the smallpox virus has been eradicated worldwide, the World Health Organization (WHO) has issued a warning about the virus's potential to propagate globally. The WHO labeled monkeypox a world public health emergency in July 2022, requiring urgent prevention and treatment. The monkeypox virus is a part of the Poxviridae family, Orthopoxvirus genus, and is accountable for smallpox, which has killed over a million people in the past. Natural hosts of the virus include squirrels, Gambian rodents, chimpanzees, and other monkeys. The monkeypox virus has transmitted to humans through primary vectors (various animal species) and secondary vectors, including direct touch with lesions, breathing particles from body fluids, and infected bedding. The viral particles are ovoid or brick-shaped, 200-250 nm in diameter, contain a single double-stranded DNA molecule, and reproduce only in the cytoplasm of infected cells. Monkeypox causes fever, cold, muscle pains, headache, fatigue, and backache. The phylogenetic investigation distinguished between two genetic clades of monkeypox: the more pathogenic Congo Basin clade and the West Africa clade. In recent years, the geographical spread of the human monkeypox virus has accelerated despite a paucity of information regarding the disease's emergence, ecology, and epidemiology. Using lesion samples and polymerase chain reaction (PCR), the monkeypox virus was diagnosed. In the USA, the improved Ankara vaccine can now be used to protect people who are at a higher risk of getting monkeypox. Antivirals that we have now work well against smallpox and may stop the spread of monkeypox, but there is no particular therapy for monkeypox.

Role of the Laboratory in the Diagnosis of Poxvirus Infections

Although WHO-led global efforts led to eradication of smallpox over four decades ago, other poxviruses, especially monkeypox, have re-emerged to occupy the ecological niche vacated by smallpox. Many of these viruses produce similar lesions thus mandating a prompt laboratory confirmation. There has been considerable evolution in the techniques available to diagnose these infections and differentiate between them. With the 2022 multi-country outbreak of monkeypox, significant efforts were made to apprise the laboratory diagnosis of the virus and numerous real-time-PCR-based assays were made commercially available. This chapter discusses the sample collection and biosafety aspects along with the repertoire of diagnostic modalities, both traditional and emerging, for poxviruses which a special focus on monkeypox. The advantages and disadvantages of each technique have been illustrated. We have also reflected upon the newer advances and the existing lacunae.

Gold-based paper for antigen detection of monkeypox virus

In 2022, the outbreak of the monkeypox virus occurred in many non-endemic countries, and the World Health Organization (WHO) assessed that this outbreak was "atypical". The establishment of a rapid and effective assay that can be used for the early diagnosis of monkeypox virus infection is crucial for outbreak prevention and control. In this study, the monkeypox virus A29 protein and the homologous vaccinia virus A27 protein and cowpox virus 162 protein were expressed in Escherichia coli BL21 for screening. We synthesized the monkeypox virus A29_17-49 peptide as the immunogen and obtained 25 monoclonal antibodies (mAbs) against the A29 protein using mouse hybridoma techniques. Then an immunochromatographic test strip method for detecting A29 was established. The strips utilizing mAb-7C5 and 5D8 showed the best sensitivity and lowest limit of detection: 50 pg mL^-1 for purified A29 and specificity tests showed that the strips did not cross-react with other orthopox viruses (vaccinia virus or cowpox virus) as well as common respiratory pathogens (SARS-CoV-2, influenza A and influenza B). Therefore, this method can be used for early and rapid diagnosis of monkeypox virus infection by antigen detection.

Emergence of monkeypox: a worldwide public health crisis

The human monkeypox virus (MPV), a zoonotic illness that was hitherto solely prevalent in Central and West Africa, has lately been discovered to infect people all over the world and has become a major threat to global health. Humans unintentionally contract this zoonotic orthopoxvirus, which resembles smallpox, when they come into contact with infected animals. Studies show that the illness can also be transferred through frequent proximity, respiratory droplets, and household linens such as towels and bedding. However, MPV infection does not presently have a specified therapy. Smallpox vaccinations provide cross-protection against MPV because of antigenic similarities. Despite scant knowledge of the genesis, epidemiology, and ecology of the illness, the incidence and geographic distribution of monkeypox outbreaks have grown recently. Polymerase chain reaction technique on lesion specimens can be used to detect MPV. Vaccines like ACAM2000, vaccinia immune globulin intravenous (VIG-IV), and JYNNEOS (brand name: Imvamune or Imvanex) as well as FDA-approved antiviral medications such as brincidofovir (brand name: Tembexa), tecovirimat (brand name: TPOXX or ST-246), and cidofovir (brand name: Vistide) are used as therapeutic medications against MPV. In this overview, we provide an outline of the MPV's morphology, evolution, mechanism, transmission, diagnosis, preventative measures, and therapeutic approaches. This study offers the fundamental information required to prevent and manage any further spread of this emerging virus.

Seasonal recurrence of cowpox virus outbreaks in captive cheetahs (Acinonyx jubatus)

Cowpox virus infections in captive cheetahs (Acinonyx jubatus) with high morbidity and mortality have already been reported in the UK and Russia in the 1970s. However, most of the reported cases have been singular events. Here, we report a total of five cowpox virus outbreaks in cheetahs in the same safari park in Denmark between 2010 and 2014. Nine cheetahs showed varying severity of clinical disease; two of them died (22%). All episodes occurred between August and October of the respective year. No other carnivores kept at the same institution nor the keepers taking care of the animals were clinically affected. The clinical picture of cowpox was confirmed by extensive laboratory investigations including histopathological and molecular analyses as well as cell culture isolation of a cowpox virus. High anti-orthopoxvirus antibody titers were detected in all 9 diseased cheetahs compared to seven contact cheetahs without clinical signs and 13 cheetahs not in direct contact. Additionally, whole genome sequencing from one sample of each cluster with subsequent phylogenetic analysis showed that the viruses from different outbreaks have individual sequences but clearly form a clade distinct from other cowpox viruses. However, the intra-clade distances are still larger than those usually observed within clades of one event. These findings indicate multiple and separate introductions of cowpox virus, probably from wild rodent populations, where the virus keeps circulating naturally and is only sporadically introduced into the cheetahs. Sero-positivity of voles (Arvicola amphibious) caught in zoo grounds strengthens this hypothesis. As a consequence, recommendations are given for medical and physical management of diseased cheetahs, for hygienic measures as well as for pre-shipment isolation before cheetah export from zoo grounds.

Classification of Cowpox Viruses into Several Distinct Clades and Identification of a Novel Lineage

Cowpox virus (CPXV) was considered as uniform species within the genus Orthopoxvirus (OPV). Previous phylogenetic analysis indicated that CPXV is polyphyletic and isolates may cluster into different clades with two of these clades showing genetic similarities to either variola (VARV) or vaccinia viruses (VACV). Further analyses were initiated to assess both the genetic diversity and the evolutionary background of circulating CPXVs. Here we report the full-length sequences of 20 CPXV strains isolated from different animal species and humans in Germany. A phylogenetic analysis of altogether 83 full-length OPV genomes confirmed the polyphyletic character of the species CPXV and suggested at least four different clades. The German isolates from this study mainly clustered into two CPXV-like clades, and VARV- and VACV-like strains were not observed. A single strain, isolated from a cotton-top tamarin, clustered distantly from all other CPXVs and might represent a novel and unique evolutionary lineage. The classification of CPXV strains into clades roughly followed their geographic origin, with the highest clade diversity so far observed for Germany. Furthermore, we found evidence for recombination between OPV clades without significant disruption of the observed clustering. In conclusion, this analysis markedly expands the number of available CPXV full-length sequences and confirms the co-circulation of several CPXV clades in Germany, and provides the first data about a new evolutionary CPXV lineage.

Development of a Genus-Specific Antigen Capture ELISA for Orthopoxviruses - Target Selection and Optimized Screening

Orthopoxvirus species like cowpox, vaccinia and monkeypox virus cause zoonotic infections in humans worldwide. Infections often occur in rural areas lacking proper diagnostic infrastructure as exemplified by monkeypox, which is endemic in Western and Central Africa. While PCR detection requires demanding equipment and is restricted to genome detection, the evidence of virus particles can complement or replace PCR. Therefore, an easily distributable and manageable antigen capture enzyme-linked immunosorbent assay (ELISA) for the detection of orthopoxviruses was developed to facilitate particle detection. By comparing the virus particle binding properties of polyclonal antibodies developed against surface-exposed attachment or fusion proteins, the surface protein A27 was found to be a well-bound, highly immunogenic and exposed target for antibodies aiming at virus particle detection. Subsequently, eight monoclonal anti-A27 antibodies were generated and characterized by peptide epitope mapping and surface plasmon resonance measurements. All antibodies were found to bind with high affinity to two epitopes at the heparin binding site of A27, toward either the N- or C-terminal of the crucial KKEP-segment of A27. Two antibodies recognizing different epitopes were implemented in an antigen capture ELISA. Validation showed robust detection of virus particles from 11 different orthopoxvirus isolates pathogenic to humans, with the exception of MVA, which is apathogenic to humans. Most orthopoxviruses could be detected reliably for viral loads above 1 × 103 PFU/mL. To our knowledge, this is the first solely monoclonal and therefore reproducible antibody-based antigen capture ELISA able to detect all human pathogenic orthopoxviruses including monkeypox virus, except variola virus which was not included. Therefore, the newly developed antibody-based assay represents important progress towards feasible particle detection of this important genus of viruses.

Detection of human-pathogenic poxviruses

With the eradication of smallpox about 30 years ago, the identification and differentiation of other poxviruses with varying pathogenicity in humans present a challenge for diagnostic facilities. While a clinical differentiation can be demanding, electron microscopy is the fastest approach to identify poxviruses. Molecular techniques, based on specific genomic sequences, are routinely applied to identify poxvirus species and distinguish between individual virus variants. In this chapter, we present detailed protocols for both techniques and discuss questions relevant to fast and reliable diagnostics of poxviruses.

Cowpox virus outbreak in banded mongooses (Mungos mungo) and jaguarundis (Herpailurus yagouaroundi) with a time-delayed infection to humans

Background

Often described as an extremely rare zoonosis, cowpox virus (CPXV) infections are on the increase in Germany. CPXV is rodent-borne with a broad host range and contains the largest and most complete genome of all poxviruses, including parts with high homology to variola virus (smallpox). So far, most CPXV cases have occurred individually in unvaccinated animals and humans and were caused by genetically distinguishable virus strains.

Methodology/Principal Findings

Generalized CPXV infections in banded mongooses (Mungos mungo) and jaguarundis (Herpailurus yagouaroundi) at a Zoological Garden were observed with a prevalence of the affected animal group of 100% and a mortality of 30%. A subsequent serological investigation of other exotic animal species provided evidence of subclinical cases before the onset of the outbreak. Moreover, a time-delayed human cowpox virus infection caused by the identical virus strain occurred in a different geographical area indicating that handling/feeding food rats might be the common source of infection.

Conclusions/Significance

Reports on the increased zoonotic transmission of orthopoxviruses have renewed interest in understanding interactions between these viruses and their hosts. The list of animals known to be susceptible to CPXV is still growing. Thus, the likely existence of unknown CPXV hosts and their distribution may present a risk for other exotic animals but also for the general public, as was shown in this outbreak. Animal breeders and suppliers of food rats represent potential multipliers and distributors of CPXV, in the context of increasingly pan-European trading. Taking the cessation of vaccination against smallpox into account, this situation contributes to the increased incidence of CPXV infections in man, particularly in younger age groups, with more complicated courses of clinical infections.

Cowpox virus infection in pet rat owners: not always immediately recognized

BACKGROUND

The aim of this article is to make physicians of all specialties aware of the possible variations of clinical course in human cowpox infection. This has been a matter of current interest since the detection of a first cluster of infections among owners of white pet rats in the Krefeld area in the spring of 2008. Two further cases arose in the Krefeld area in November 2008, and there have since been multiple further reports from various regions in Germany and the neighboring countries.

METHOD

The authors report on the first six documented cases of infection with cowpox virus among young persons owning pet rats, with both typical and atypical clinical courses.

RESULTS

The clinical, molecular biological, and serological findings confirmed cowpox virus infection in all six cases. The DNA sequence of the cowpox virus hemagglutinin gene was identical in all patients. The infections had arisen after direct contact with pet rats.

CONCLUSIONS

Molecular genetic analysis of the cases described here suggests that the observed occurrence of cowpox virus infection among human beings and pet rats in multiple geographical areas represents a unitary epidemiological event that has not yet come under control. Further cases can be expected.

Orthopoxvirus detection in environmental specimens during suspected bioterror attacks: inhibitory influences of common household products

After terrorists attacked the United States in 2001, the appearance of letters and other objects containing powdery substances with unknown potentials for biological threat focused attention on the speed, sensitivity, and reliability of diagnostic methods. This study summarizes the abilities and limitations of real-time PCR, electron microscopy (EM), and virus isolation when used to detect potential bioweapons. In particular, we investigated the inhibitory influences of different common household products present in environmental specimens on PCR yield, EM detection, and virus isolation. We used vaccinia virus as a model for orthopoxviruses by spiking it into specimens. In the second part of the study, we describe modifications of diagnostic methods to overcome inhibitory effects. A variety of PCR amplification enhancers, DNA extraction protocols, and applications of internal controls were evaluated to improve diagnostic simplicity, speed, and reliability. As a result, we strongly recommend using at least two different frontline techniques in parallel, e.g., EM and PCR. A positive result obtained by any one of these techniques should be followed by a biological method to confirm the putative diagnosis. Confirmatory methods include virus isolation followed by an agent-specific immunofluorescence assay to confirm the presence of replication-competent particles.