Dhori Virus Research Articles

Histopathological effects of the fruit extract of Citrullus colocynthis on the ovary of the tick Hyalomma dromedarii

Hyalomma dromedarii is the predominant tick species parasitizing camels in Egypt which leads to mortalities in young animals that result in economic losses. It can transmit a lot of pathogens to animals and humans, such as the Crimean-Congo hemorrhagic fever virus, the Dhori virus, Kadam virus, Theileria annulata and spotted fever rickettsia. The continuous use of chemical acaricides has negative impact on the environment and almost led to acaricidal resistance, and hence the plant extracts represent alternative methods for controlling ticks. The present study was carried out to assess the histopathological effects on the ovary of fed female Hyalomma dromedarii following immersion in the ethanolic extract of fruits of Citrullus colocynthis (100 mg/mL). Light, scanning and transmission electron microscopy observations provided evidence that Citrullus colocynthis caused extensive damage to oocytes. Destruction of the internal organelles of oocytes, along with delay and/or inhibition of vitellogenesis were demonstrated. This is the first histological study that points to damage in H. dromedarii ovaries following treatment with the ethanolic extract of fruits of C. colocynthis. The data presented suggest that the plant extract affects the ovary either directly by entering the oocytes and/or indirectly by damaging the gut cells and digestion of blood that interfere with the development of oocytes, so it can be used as a promising agent for tick control.

Pseudotyped zoonotic thogotoviruses exhibit broad entry range in mammalian cells

Viruses in the thogotovirus genus of the family Orthomyxoviridae are much less well-understood than influenza viruses despite documented zoonotic transmission and association with human disease. This study therefore developed a cell-cell fusion assay and three pseudotyping tools and used them to assess envelope function and cell tropism. Envelope glycoproteins of Dhori (DHOV), Thogoto (THOV), Bourbon, and Sinu viruses were all revealed to exhibit pH-dependent triggering of membrane fusion. Lentivirus vectors were robustly pseudotyped with these glycoproteins while influenza virus vectors showed pseudotyping compatibility, albeit at lower efficiencies. Replication-competent vesicular stomatitis virus expressing DHOV or THOV glycoproteins were also successfully generated. These pseudotyped viruses mediated entry into a wide range of mammalian cell lines, including human primary cells. The promiscuousness of these viruses suggests the use of a relatively ubiquitous receptor and their entry into numerous mammalian cells emphasize their high potential as veterinary and zoonotic diseases.

Geographical distribution and pathogenesis of ticks and tick-borne viral diseases.

Ticks are obligatory hematophagous arthropods that harbor and transmit infectious pathogens to humans and animals. Tick species belonging to Amblyomma, Ixodes, Dermacentor, and Hyalomma genera may transmit certain viruses such as Bourbon virus (BRBV), Dhori virus (DHOV), Powassan virus (POWV), Omsk hemorrhagic fever virus (OHFV), Colorado tick fever virus (CTFV), Crimean-Congo hemorrhagic fever virus (CCHFV), Heartland virus (HRTV), Kyasanur forest disease virus (KFDV), etc. that affect humans and certain wildlife. The tick vectors may become infected through feeding on viraemic hosts before transmitting the pathogen to humans and animals. Therefore, it is vital to understand the eco-epidemiology of tick-borne viruses and their pathogenesis to optimize preventive measures. Thus this review summarizes knowledge on some medically important ticks and tick-borne viruses, including BRBV, POWV, OHFV, CTFV, CCHFV, HRTV, and KFDV. Further, we discuss these viruses' epidemiology, pathogenesis, and disease manifestations during infection.

Dhori virus

This datasheet on Dhori virus covers Identity, Distribution, Hosts/Species Affected, Vectors & Intermediate Hosts.

Arboviruses in the Astrakhan region of Russia for 2018 season: The development of multiplex PCR assays and analysis of mosquitoes, ticks, and human blood sera.

The Astrakhan region of Russia is endemic for the number of arboviruses. In this paper, we describe the results of the detection of the list of neglected arboviruses in the Astrakhan region for the 2018 season. For the purpose of the study in-house PCR assays for detection of 18 arboviruses have been developed and validated using arboviruses obtained from Russian State Collection of Viruses. Pools of ticks (n=463) and mosquitoes (n=312) as well as 420 samples of human patients sera have been collected and analyzed. Using developed multiplex real-time PCR assays we were able to detect RNA of eight arboviruses (Crimean-Congo hemorrhagic fever virus, Dhori (Batken strain) virus, Batai virus, Tahyna virus, Uukuniemi virus, Inkoo virus, Sindbis virus and West Nile fever virus). All discovered viruses are capable of infecting humans causing fever and in some cases severe forms with hemorrhagic or neurologic symptoms. From PCR-positive samples, we were able to recover one isolate each of Dhori (Batken strain) virus and Crimean-Congo hemorrhagic fever virus which were further characterized by next-generation sequencing. The genomic sequences of identified Dhori (Batken strain) virus strain represent the most complete genome of Batken virus strain among previously reported.

Epidemiological Study of Thogoto and Dhori Virus Infection in People Bitten by Ticks, and in Sheep, in an Area of Northern Spain.

There is little information on Thogoto virus (THOV) and Dhori virus (DHOV)infection in Spain. A total of 283 serum samples from 150 human subjects (78 males, 72 females) bitten by ticks, as well as samples from 120 sheep (one per animal), were studied by immunofluorescence assay. All human and animal subjects were from the province of Palencia in northern Spain. Eight human subjects had antibodies against THOV (seroprevalence: 5.3%) and six had antibodies against DHOV (seroprevalence: 4%); titers ranged between 1/32–1/256 and 1/32–1/128, respectively. No significant differences were seen in seroprevalence in terms of gender or age, although people with antibodies were significantly more likely to have had contact with livestock for professional reasons. One subject with an acute infection had IgM antibodies to both viruses and seroconverted to IgG. For the sheep, 24 serum samples were positive for antibodies to THOV (seroprevalence: 20%) and 32 for antibodies to DHOV (seroprevalence: 26.8%); titers ranged between 1/16 and 1/128. The seroprevalence of both viruses was significantly higher in animals < 4 years of age. Together, these results reveal the circulation of DHOV and THOV in humans and sheep in the province of Palencia. Sheep might be used as indicators of the presence of these organisms.

Results of investigation of ticks in Volga river delta (Astrakhan region, 2017) for Crimean-Congo hemorrhagic fever virus (Nairoviridae, Orthonairovirus, CCHFV) and other tick-borne arboviruses.

There are natural foci of Crimean-Congo hemorrhagic fever (CCHF) that vectored by Hyalomma marginatum ticks in Volga river delta (Astrakhan region, South of Russia). The circulation of Dhori virus (DHOV) (Thogotovirus: Orthomyxoviridae) has been also shown here. We hypothesized that other tick-borne arboviruses are also likely to circulate in the region. In particular, Bhanja virus (Phlebovirus: Phenuiviridae), Wad Medani virus (Orbivirus: Reoviridae), and Tamdy virus (Orthonairovirus: Nairoviridae), which were found to circulate in neighboring regions and are vectored by Haemaphysalis spp., Dermacenter spp., and Hyalomma spp. ticks. The aim of the study was to examine ixodid ticks in Volga river delta for the presence of CCHFV, DHOV, Bhanja virus, Wad Medani virus, and Tamdy virus. Ticks were collected in Volga river delta in 2017. We used molecular genetic methods for the detection and analysis of nucleic acids (PCR, sequencing, phylogenetic analysis). We detect CCHFV and DHOV RNA in H. marginatum ticks. The rate of infected H. marginatum ticks was 1.98% for CCHFV and 0.4% for DHOV. The results of genetic analysis showed that found DHOV strains are almost identical (99-100% in the M gene) and forms a separate genetic lineage alongside of Batken virus from Central Asia. At the same time, Bhanja virus, Wad Medani virus, and Tamdy virus were not found in ticks, collected in this region. DHOV is circulating in the natural foci of CCHF in the Volga river delta. The ratio of infection of H. marginatum with CCHFV and DHOV was determined for the first time.

Postfusion structure of human-infecting Bourbon virus envelope glycoprotein

Thogotoviruses are important zoonotic viruses infecting a variety of domestic animals, as well as humans. Among these viruses, Bourbon virus (BRBV) is one of the several human-infecting members, which emerged in the US in recent years and caused human deaths. Here, we report the crystal structure of the BRBV envelope glycoprotein in the postfusion conformation. The structure adopts the typical fold of a class III viral fusion protein and displays an extensive positively charged electrostatic potential pattern, which resembles the glycoprotein of Dhori virus and is consistent with our previous predictions. In addition, compared to other previously defined class III viral fusion proteins, the structures of all thogotovirus glycoproteins and homologs are more similar to herpes virus glycoprotein Bs than to the rhabdovirus G proteins. Thus, class III viral fusion proteins are quite diverse in structure, and sub-classes may have developed during evolution.

Improving Baculovirus Transduction of Mammalian Cells by Incorporation of Thogotovirus Glycoproteins.

Baculovirus can transduce a wide range of mammalian cells and is considered a promising gene therapy vector. However, the low transduction efficiency of baculovirus into many mammalian cells limits its practical application. Co-expressing heterologous viral glycoproteins (GPs), such as vesicular stomatitis virus G protein (VSV G), with baculovirus native envelope protein GP64 is one of the feasible strategies for improving virus transduction. Tick-borne thogotoviruses infect mammals and their GPs share sequence/structure homology and common evolutionary origins with baculovirus GP64. Herein, we tested whether thogotovirus GPs could facilitate the entry of the prototype baculovirus Autographa californica multiple multiple nucleopolyhedrovirus (AcMNPV) into mammalian cells. The gp genes of two thogotoviruses, Thogoto virus and Dhori virus, were inserted into the AcMNPV genome. Both GPs were properly expressed and incorporated into the envelope of the recombinant AcMNPVs. The transduction rates of recombinant AcMNPVs expressing the two thogotovirus GPs increased for approximately 4-12 fold compared to the wild type AcMNPV in six of the 12 tested mammalian cell lines. It seemed that thogotovirus GPs provide the recombinant AcMNPVs with different cell tropisms and showed better performance in several mammalian cells compared to VSV G incorporated AcMNPV. Further studies showed that the improved transduction was a result of augmented virus-endosome fusion and endosome escaping, rather than increased cell binding or internalization. We found the AcMNPV envelope protein GP64-mediated fusion was enhanced by the thogotovirus GPs at relatively higher pH conditions. Therefore, the thogotovirus GPs represent novel candidates to improve baculovirus-based gene delivery vectors.

Characterization of a novel thogotovirus isolated from Amblyomma testudinarium ticks in Ehime, Japan: A significant phylogenetic relationship to Bourbon virus

The genus Thogotovirus, as represented by Thogoto virus and Dhori virus, comprises a group of arthropod-borne viruses, most members of which are transmitted by ticks. Here we report the genetic and biological characterization of a new thogotovirus, designated Oz virus (OZV), isolated from the hard tick Amblyomma testudinarium in Ehime, Japan. OZV efficiently replicated and induced a cytopathic effect in Vero cells, from which enveloped pleomorphic virus particles were formed by budding. OZV could also replicate in BHK-21 and DH82 cells and caused high mortality in suckling mice after intracerebral inoculation. Phylogenetic analyses of six viral proteins indicated that OZV is clustered with Dhori and related viruses, and is most closely related in glycoprotein (GP) and matrix protein (M) sequences to Bourbon virus, a human-pathogenic thogotovirus discovered recently in the United States. Our findings emphasize the need for understanding the geographic distribution and ecology of OZV and related viruses and for reevaluation of the medical and public health importance of thogotoviruses.

Structures of human-infecting Thogotovirus fusogens support a common ancestor with insect baculovirus

Thogotoviruses are emerging tick-borne zoonotic orthomyxoviruses infecting both humans and domestic animals with severe clinical consequences. These viruses utilize a single-envelope glycoprotein (Gp) to facilitate their entry into host cells. Here, we present the Gp structures of Thogoto and Dhori viruses, both of which are members of the Thogotovirus genus in the family Orthomyxoviridae These structures, determined in the postfusion conformation, identified them as class III viral fusion proteins. It is intriguing that the Gp structures are similar to the envelope protein of baculovirus, although sharing a low sequence identity of ∼28%. Detailed structural and phylogenic analyses demonstrated that these Gps originated from a common ancestor. Among the structures, domain I is the most conserved region, particularly the fusion loops. Domain II showed the highest variability among different viruses, which might be related to their distinct host tropism. These findings increase our understanding of the divergent evolution processes of various orthomyxoviruses and indicate potential targets for developing antiviral therapeutics by intercepting virus entry.

Upolu virus and Aransas Bay virus, two presumptive bunyaviruses, are novel members of the family Orthomyxoviridae.

Emerging and zoonotic pathogens pose continuing threats to human health and ongoing challenges to diagnostics. As nucleic acid tests are playing increasingly prominent roles in diagnostics, the genetic characterization of molecularly uncharacterized agents is expected to significantly enhance detection and surveillance capabilities. We report the identification of two previously unrecognized members of the family Orthomyxoviridae, which includes the influenza viruses and the tick-transmitted Thogoto and Dhori viruses. We provide morphological, serologic, and genetic evidence that Upolu virus (UPOV) from Australia and Aransas Bay virus (ABV) from North America, both previously considered potential bunyaviruses based on electron microscopy and physicochemical features, are orthomyxoviruses instead. Their genomes show up to 68% nucleotide sequence identity to Thogoto virus (segment 2; ∼74% at the amino acid level) and a more distant relationship to Dhori virus, the two prototype viruses of the recognized species of the genus Thogotovirus. Despite sequence similarity, the coding potentials of UPOV and ABV differed from that of Thogoto virus, instead being like that of Dhori virus. Our findings suggest that the tick-transmitted viruses UPOV and ABV represent geographically distinct viruses in the genus Thogotovirus of the family Orthomyxoviridae that do not fit in the two currently recognized species of this genus. Upolu virus (UPOV) and Aransas Bay virus (ABV) are shown to be orthomyxoviruses instead of bunyaviruses, as previously thought. Genetic characterization and adequate classification of agents are paramount in this molecular age to devise appropriate surveillance and diagnostics. Although more closely related to Thogoto virus by sequence, UPOV and ABV differ in their coding potentials by lacking a proposed pathogenicity factor. In this respect, they are similar to Dhori virus, which, despite the lack of a pathogenicity factor, can cause disease. These findings enable further studies into the evolution and pathogenicity of orthomyxoviruses.

Comparative Structural and Functional Analysis of Orthomyxovirus Polymerase Cap-Snatching Domains

Orthomyxovirus Influenza A virus (IAV) heterotrimeric polymerase performs transcription of viral mRNAs by cap-snatching, which involves generation of capped primers by host pre-mRNA binding via the PB2 subunit cap-binding site and cleavage 10–13 nucleotides from the 5′ cap by the PA subunit endonuclease. Thogotoviruses, tick-borne orthomyxoviruses that includes Thogoto (THOV), Dhori (DHOV) and Jos (JOSV) viruses, are thought to perform cap-snatching by cleaving directly after the cap and thus have no heterogeneous, host-derived sequences at the 5′ extremity of their mRNAs. Based on recent work identifying the cap-binding and endonuclease domains in IAV polymerase, we determined the crystal structures of two THOV PB2 domains, the putative cap-binding and the so-called ‘627-domain’, and the structures of the putative endonuclease domains (PA-Nter) of THOV and DHOV. Despite low sequence similarity, corresponding domains have the same fold confirming the overall architectural similarity of orthomyxovirus polymerases. However the putative Thogotovirus cap-snatching domains in PA and PB2 have non-conservative substitutions of key active site residues. Biochemical analysis confirms that, unlike the IAV domains, the THOV and DHOV PA-Nter domains do not bind divalent cations and have no endonuclease activity and the THOV central PB2 domain does not bind cap analogues. On the other hand, sequence analysis suggests that other, non-influenza, orthomyxoviruses, such as salmon anemia virus (isavirus) and Quaranfil virus likely conserve active cap-snatching domains correlating with the reported occurrence of heterogeneous, host-derived sequences at the 5′ end of the mRNAs of these viruses. These results highlight the unusual nature of transcription initiation by Thogotoviruses.

Ticks and Tick-Borne Viruses From Livestock Hosts in Arid and Semiarid Regions of the Eastern and Northeastern Parts of Kenya

Biodiversity and relative abundance of ticks and associated arboviruses in Garissa (northeastern) and Isiolo (eastern) provinces of Kenya were evaluated. Ticks were collected from livestock, identified to species, pooled, and processed for virus isolation. In Garissa, Rhipicephalus pulchellus Gerstacker (57.8%) and Hyalomma truncatum Koch (27.8%) were the most abundant species sampled, whereas R. pulchellus (80.4%) and Amblyomma gemma Donitz (9.6%) were the most abundant in Isiolo. Forty-four virus isolates, comprising Dugbe virus (DUGV; n = 22) and Kupe virus (n = 10; Bunyaviridae: Nirovirus), Dhori virus (DHOV; n = 10; Orthomyxoviridae: Thogotovirus),and Ngari virus (NRIV; n = 2; Bunyaviridae: Orthobunyavirus), were recovered mostly from R. pulchellus sampled in Isiolo. DUGV was mostly recovered from R. pulchellus from sheep and cattle, and DHOV from R. pulchellus from sheep. All Kupe virus isolates were from Isiolo ticks, including R. pulchellus from all the livestock, A. gemma and Amblyomma variegatum F. from cattle, and H. truncatum from goat. NRIV was obtained from R. pulchellus and A. gemma sampled from cattle in Isiolo and Garissa, respectively, while all DHOV and most DUGV (n = 12) were from R. pulchellus sampled from cattle in Garissa. DUGV was also recovered from H. truncatum and Amblyomma hebraeum Koch from cattle and from Rhipicephalus annulatus Say from camel. This surveillance study has demonstrated the circulation of select tick-borne viruses in parts of eastern and northeastern provinces of Kenya, some of which are of public health importance. The isolation of NRIV from ticks is particularly significant because it is usually known to be a mosquito-borne virus affecting humans.

Dhori Virus (Orthomyxoviridae: Thogotovirus) Infection of Mice Produces a Disease and Cytokine Response Pattern Similar to That of Highly Virulent Influenza A (H5N1) Virus Infection in Humans

Mice infected with Dhori virus (DHOV) develop a fulminant, systemic, and uniformly fatal illness that has many of the clinical and pathologic findings seen in H5N1 influenza A virus infection. However, the role of host's immune response in DHOV infection remains unclear. In this study, the concentrations of 23 inflammatory cytokines and chemokines were measured in the liver, lungs, and sera of mice during the course of DHOV infection. Liver function, level of viremia, and hematologic response were also monitored. Infected animals exhibited significant leucopenia and lymphopenia, which directly correlated with the disease progression. High yields of infectious virus along with strikingly elevated expression of various inflammatory mediators, including tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, IL-10, macrophage inflammatory protein (MIP)-1alpha, manocyte chemoattractant protein (MCP)-1, and interferon (IFN)-alpha, indicate that these responses play an important role in the observed disease and pathology. The overall clinical, pathologic, and immunologic responses of ICR mice to DHOV infection closely resemble those described for highly virulent influenza A virus infection in humans, thereby offering a realistic, safe, and alternative animal model for studying the pathogenesis and treatment of highly pathogenic avian influenza virus.

DHORI VIRUS (ORTHOMYXOVIRIDAE: THOGOTOVIRUS) INFECTION IN MICE: A MODEL OF THE PATHOGENESIS OF SEVERE ORTHOMYXOVIRUS INFECTION

After intranasal, subcutaneous, or intraperitoneal infection with Dhori virus (DHOV), adult mice developed a fulminant and uniformly fatal illness with many of the clinical and pathologic findings seen in mice infected with H5N1 highly pathogenic avian influenza A virus. Histopathologic findings in lungs of DHOV-infected mice consisted of hemorrhage, inflammation, and thickening of the interstitium and the alveolar septa and alveolar edema. Extra-pulmonary findings included hepatocellular necrosis and steatosis, widespread severe fibrinoid necrosis in lymphoid organs, marked lymphocyte loss and karyorrhexis, and neuronal degeneration in brain. Similar systemic histopathologic findings have been reported in the few fatal human H5N1 cases examined at autopsy. Because of the relationship of DHOV to the influenza viruses, its biosafety level 2 status, and its similar pathology in mice, the DHOV-mouse model may offer a low-cost, relatively safe, and realistic animal model for studies on the pathogenesis and management of H5N1 virus infection.

Tickborne Arbovirus Surveillance in Market Livestock, Nairobi, Kenya

To identify tickborne viruses circulating in Kenya and the surrounding region, we conducted surveillance at abattoirs in Nairobi, Kenya. Species of ticks collected included Rhipicephalus pulchellus (56%), Amblyomma gemma (14%), R. appendiculatus (8%), A. variegatum (6%), and others. A total of 56 virus isolates were obtained, 26 from A. gemma, 17 from R. pulchellus, 6 from A. variegatum, and 7 from other species. Virus isolates included Dugbe virus (DUGV), an unknown virus related to DUGV, Thogoto, Bhanja, Kadam, Dhori, Barur, and foot-and-mouth disease (FMDV) viruses. This is the first report of Dhori virus isolation in East Africa and the first known isolation of FMDV associated with tick collection. Our results demonstrate the potential for tickborne dissemination of endemic and emergent viruses and the relevance of A. gemma in the maintenance of tickborne viruses in this region.

Human Laboratory Acquired ARBO-, ARENA-, and Hantavirus Infections

A total of 78 cases of laboratory acquired infections occurred at D. I. Ivanovsky Institute of Virology, M. P. Chumakov Institute of Poliomyelitis and Viral Encephalitis and Rostov na Donu Institute of Epidemiology, Microbiology and Hygiene. All these cases were caused by accidental infection of the staff with the following viruses: Venezuelan equine encephalomyelitis (n=34), Kyasanur forest disease (n=1), Omsk hemorrhagic fever (n=1), Crimean-Congo hemorrhagic fever (CCHF) (n=2), Dhori (n=5), vesicular stomatitis (n=1), Machupo (n=3), and hemorrhagic fever with the renal syndrome (n=31). The majority of cases were caused by inhaling virus aerosols. All cases were a result of accidents or neglect of safety measures. Diagnoses were confirmed by virus isolation and/or detection of specific antibodies in convalescent serum. With the exception of one lethal case of CCHF, patients recovered without disability. The pathogenicity of Dhori virus in man was discovered as a result of laboratory infection of 5 staff members.

Mx1 sensitivity: Batken virus is an orthomyxovirus closely related to Dhori virus.

Batken virus, isolated from mosquitoes and ticks, was tentatively classified as a member of the family Bunyaviridae. Here we show that Batken virus is inhibited by the interferon-induced Mx1 protein of mice which selectively blocks the growth of orthomyxoviruses, including Thogoto and Dhori viruses. Furthermore, we show that Batken virus multiplication is characterized by accumulation of viral proteins in the nucleus and by budding of viral particles from the cell surface. Serological cross-reactions between Batken and Dhori viruses revealed a phylogenetic relationship of these viruses, as previously also proposed by D. K. Lvov. Fragments of the Batken virus glycoprotein and nucleoprotein genes were amplified by RT-PCR. The deduced amino acid sequences were similar to the corresponding Dhori virus sequences. Therefore, Batken virus should be classified into the newly established genus Thogotovirus of the family Orthomyxoviridae. Finally, our results demonstrate that Mx1 susceptibility of orthomyxoviruses is a reliable marker in the hunt for new family members.

The fourth genus in the Orthomyxoviridae: sequence analyses of two Thogoto virus polymerase proteins and comparison with influenza viruses

The tick-borne Thogoto virus (THOV) is the type species of a newly recognized fourth genus, Thogotovirus, in the family Orthomyxoviridae. Because of the distant relationship of THOV with the influenza viruses, determination of its genomic information can potentially be used to identify important domains in influenza virus proteins. We have determined the complete nucleotide sequence of the second longest RNA segment of THOV. The molecule comprises 2212 nucleotides with a single large open reading frame encoding a protein of 710 amino acids, estimated M r 81 284. The protein shares 77% amino acid similarity with the PB1-like protein of Dhori virus, a related tick-borne virus, and 50–53% with the PB1 polymerase proteins of influenza virus A, B and C. All the motifs characteristic of RNA-dependent polymerases were identified including the SSDD motif common to all RNA-dependant RNA polymerases, indicating that the THOV protein is functionally analogous to the influenza virus PB1 proteins and involved in chain elongation. We also report the corrected sequence of the third longest RNA segment of THOV, encoding a protein which shares 44–47% amino acid similarity with the PA-like polymerase proteins of influenza virus A, B and C. The biological significance of conserved domains in these orthomyxovirid proteins is discussed.