Mode of Infection of Hokkaido Virus (GenusHantavirus) among Grey Red-Backed Voles,Myodes rufocanus, in Hokkaido, Japan

Molecular evolution of Hokkaido virus, a genotype of Orthohantavirus puumalaense, among Myodes rodents

Viruses in the genus Orthohantavirus within the family Hantaviridae cause human hantavirus infections and represent a threat to public health. Hokkaido virus (HOKV), a genotype of Orthohantavirus puumalaense (Puumala virus; PUUV), was first identified in Tobetsu, Hokkaido, Japan. Although it is genetically related to the prototype of PUUV, the evolutionary pathway of HOKV is unclear. We conducted a field survey in a forest in Tobetsu in 2022 and captured 44 rodents. Complete coding genome sequences of HOKVs were obtained from five viral-RNA-positive rodents (four Myodes rufocanus bedfordiae and one Apodemus speciosus). Phylogenetic analysis revealed a close relationship between the phylogenies and geographical origins of M. rufocanus-related orthohantaviruses. Comparison of the phylogenetic trees of the S segments of orthohantaviruses and the cytochrome b genes of Myodes species suggested that Myodes-related orthohantaviruses evolved in Myodes rodent species as a result of genetic isolation and host switching.

Hemorrhagic Fever with Renal Syndrome in Asia: History, Pathogenesis, Diagnosis, Treatment, and Prevention

Hemorrhagic Fever with Renal Syndrome (HFRS) is the most frequently diagnosed zoonosis in Asia. This zoonotic infection is the result of exposure to the virus-contaminated aerosols. Orthohantavirus infection may cause Hemorrhagic Fever with Renal Syndrome (HRFS), a disease that is characterized by acute kidney injury and increased vascular permeability. Several species of orthohantaviruses were identified as causing infection, where Hantaan, Puumala, and Seoul viruses are most common. Orthohantaviruses are endemic to several Asian countries, such as China, South Korea, and Japan. Along with those countries, HFRS tops the list of zoonotic infections in the Far Eastern Federal District of Russia. Recently, orthohantavirus circulation was demonstrated in small mammals in Thailand and India, where orthohantavirus was not believed to be endemic. In this review, we summarized the current data on orthohantaviruses in Asia. We gave the synopsis of the history and diversity of orthohantaviruses in Asia. We also described the clinical presentation and current understanding of the pathogenesis of orthohantavirus infection. Additionally, conventional and novel approaches for preventing and treating orthohantavirus infection are discussed.

Hantavirus Induced Kidney Disease

Hantavirus induced hemorrhagic fever with renal syndrome (HFRS) is an emerging viral zoonosis affecting up to 200,000 humans annually worldwide. This review article is focused on recent advances in the mechanism, epidemiology, diagnosis, and treatment of hantavirus induced HFRS. The importance of interactions between viral and host factors in the design of therapeutic strategies is discussed. Hantavirus induced HFRS is characterized by thrombocytopenia and proteinuria of varying severities. The mechanism of kidney injury appears immunopathological with characteristic deterioration of endothelial cell function and compromised barrier functions of the vasculature. Although multidisciplinary research efforts have provided insights about the loss of cellular contact in the endothelium leading to increased permeability, the details of the molecular mechanisms remain poorly understood. The epidemiology of hantavirus induced renal failure is associated with viral species and the geographical location of the natural host of the virus. The development of vaccine and antiviral therapeutics is necessary to avoid potentially severe outbreaks of this zoonotic illness in the future. The recent groundbreaking approach to the SARS-CoV-2 mRNA vaccine has revolutionized the general field of vaccinology and has provided new directions for the use of this promising platform for widespread vaccine development, including the development of hantavirus mRNA vaccine. The combinational therapies specifically targeted to inhibit hantavirus replication and vascular permeability in infected patients will likely improve the disease outcome.

[Yezo virus and emerging orthonairovirus diseases]

A new etiological agent of an acute febrile illness following tick bite has been found in Hokkaido, Japan, in 2019 and designated as Yezo virus. Seven cases of Yezo virus infection were identified from 2014 to 2020 by passive and retrospective surveillance. Yezo virus is classified into the genus Orthonairovirus, family Nairoviridae and forms Sulina genogroup together with Sulina virus, which was identified in ticks in Romania. The Sulina genogroup viruses are closely related to the Tamdy genogroup viruses recently reported as causative agents of febrile illness in China and distant from known orthonairovirus pathogens, such as Crimean-Congo hemorrhagic fever virus. Since only limited information is available for the emerging orthonairovirus diseases, including Yezo virus infection, their occurrence should be carefully monitored.

[Rodent associated hantaviruses and hantavirus infections]

Hantaviruses belongs to the genus Hantavirus in the family Bunyaviridae are maintained in rodents and infects to humans by inhalation of the aerosol of infected rodent excreta. In this article, the epidemiology of hantavirus infection and the special relationship between rodent and hantavirus are described. Hantavirus infections include hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). HFRS is characterized high fever, hemorrhage, and renal disorder. HFRS is distributed in East Asia, Europe, and Russia. While HCPS is characterized acute respiratory dysfunction and cardiogenic shock. The distribution of HCPS is limited in North and South Americas. In Japan's neighboring countries, such as Russia, China, and Korea, large numbers of HFRS patients are reported in association with multiple hantaviruses. In Japan, hantavirus infection has not been reported since 1985 but grey red-backed vole (Myodes rufocanus bedfordiae) inhabiting Hokkaido maintain one of the hantaviruses. Coevolution between hantavirus and host may have been occurred during a long period. The endemic areas of hantavirus infection are strongly associated with the distribution of host animal carrying pathogenic hantaviruses.

Dynamic Circulation and Genetic Exchange of a Shrew-borne Hantavirus, Imjin virus, in the Republic of Korea

Hantaviruses (family Bunyaviridae) are enveloped negative-sense tripartite RNA viruses. The natural hosts of hantaviruses include rodents, shrews, moles, and bats. Imjin virus (MJNV) is a shrew-borne hantavirus identified from the Ussuri white-toothed shrews (Crocidura lasiura) in the Republic of Korea (ROK) and China. We have isolated MJNV and determined its prevalence and molecular diversity in Gyeonggi province, ROK. However, the distribution and phylogeography of MJNV in other regions of ROK remain unknown. A total of 96 C. lasiura were captured from Gangwon and Gyeonggi provinces, ROK, during 2011–2014. Among them, four (4.2%) shrews were positive for anti-MJNV IgG and MJNV RNA was detected from nine (9.4%), respectively. Based on the prevalence of MJNV RNA, the preponderance of infected shrews was male and adult, consistent with the gender- and weight-specific prevalence of hantaviruses in other species. We monitored the viral load of MJNV RNA in various tissues of shrews, which would reflect the dynamic infectious status and circulation of MJNV in nature. Our phylogeographic and genomic characterization of MJNV suggested natural occurrences of recombination and reassortment in the virus population. Thus, these findings provide significant insights into the epidemiology, phylogeographic diversity, and dynamic circulation and evolution of shrew-borne hantaviruses.

Detection of Hantaan virus RNA from anti-Hantaan virus IgG seronegative rodents in an area of high endemicity in Republic of Korea

Hantaan virus (HTNV), of the family Bunyaviridae, causes hemorrhagic fever with renal syndrome (HFRS) in humans. Although the majority of epidemiologic studies have found that rodents are seropositive for hantavirus-specific immunoglobulin, the discovery of hantavirus RNA in seronegative hosts has led to an investigation of the presence of HTNV RNA in rodents captured in HFRS endemic areas. HTNV RNA was detected in seven (3.8%) of 186 anti-HTNV IgG seronegative rodents in Republic of Korea (ROK) during 2013-2014. RT-qPCR for HTNV RNA revealed dynamic virus-host interactions of HTNV in areas of high endemicity, providing important insights into the epidemiology of hantaviruses.

Ecology of hantaviruses in Mexico: genetic identification of rodent host species and spillover infection

In our recent epidemiological survey conducted in Mexico for hantavirus infection, we identified three distinct viruses circulating in Mexican wild rodents, namely Montano virus (MTNV), Huitzilac virus (HUIV), and Carrizal virus (CARV). To gain a detailed understanding of hantavirus epidemiology and its associated hosts, 410 rodents were captured at eight collecting points in Morelos and Guerrero, Mexico, and examined for hantavirus seroprevalence, the presence of viral RNA, and rodent host species identification using cytochrome b gene sequences. Of the 32 species captured, seven species were positive for hantavirus: Peromyscus beatae (31/127; 24.4%), Reithrodontomys sumichrasti (6/15; 40%), Reithrodontomys megalotis (2/25; 8%), Peromyscus aztecus evides (1/1; 100%), Peromyscus megalops (1/41; 2.4%), Megadontomys thomasi (1/9; 11.1%), and Neotoma picta (1/6; 16.7%), with an overall prevalence of 10.5%; virus genome persisted in the majority of seropositive rodents. Nucleotide sequence and phylogenetic analysis showed that the viruses belonged mainly to the three lineages previously identified. The data showed that MTNV and CARV were primarily carried by P. beatae and R. sumichrasti, respectively. In addition, the data revealed an apparent complex interaction between hantaviruses and their hosts, suggesting active transmission and/or spillover infections within sympatric rodent species.

Puumala virus infection in Syrian hamsters (Mesocricetus auratus) resembling hantavirus infection in natural rodent hosts

The mechanism of hantavirus persistent infection in natural hosts is poorly understood due to a lack of laboratory animal models. Herein, we report that Syrian hamsters (Mesocricetus auratus) infected with Puumala virus (PUUV) at 4 weeks old show persistent infection without clinical symptoms for more than 2 months. IgG and IgM antibodies against the viral nucleocapsid protein and neutralizing antibody were first detectable at 14 days postinoculation (dpi) and maintained through 70 dpi. Viral RNA was first detected from 3 dpi in lungs and blood clots, and was detected in all tissues tested at 7 dpi. The viral RNA persisted for at least 70 days in the lungs, kidney, spleen, heart, and brain. The highest level of RNA copies was observed at 14 dpi in the lungs. Slight inflammatory reactions were observed in the lungs, adrenal glands, and brain. Immunohistochemical analysis revealed that PUUV antigen persisted until 56 dpi in the kidneys and adrenal glands. Infected hamsters showed no body weight loss or clinical signs. These results indicate that PUUV infection in hamsters is quite similar to the hantavirus infection of natural host rodents.

Phylogenetic analysis of Puumala virus subtype Bavaria, characterization and diagnostic use of its recombinant nucleocapsid protein

Puumala virus (PUUV) is the predominant hantavirus species in Germany causing large numbers of mild to moderate cases of haemorrhagic fever with renal syndrome (HFRS). During an outbreak in South-East Germany in 2004 a novel PUUV subtype designated Bavaria was identified as the causative agent of HFRS in humans [1]. Here we present a molecular characterization of this PUUV strain by investigating novel partial and almost entire nucleocapsid (N) protein-encoding small (S-) segment sequences and partial medium (M-) segment sequences from bank voles (Myodes glareolus) trapped in Lower Bavaria during 2004 and 2005. Phylogenetic analyses confirmed their classification as subtype Bavaria, which is further subdivided into four geographical clusters. The entire N protein, harbouring an amino-terminal hexahistidine tag, of the Bavarian strain was produced in yeast Saccharomyces cerevisiae and showed a slightly different reactivity with N-specific monoclonal antibodies, compared to the yeast-expressed N protein of the PUUV strain Vranica/Hällnäs. Endpoint titration of human sera from different parts of Germany and from Finland revealed only very slight differences in the diagnostic value of the different recombinant proteins. Based on the novel N antigen indirect and monoclonal antibody capture IgG-ELISAs were established. By using serum panels from Germany and Finland their validation demonstrated a high sensitivity and specificity. In summary, our investigations demonstrated the Bavarian PUUV strain to be genetically divergent from other PUUV strains and the potential of its N protein for diagnostic applications.

An efficient in vivo method for the isolation of Puumala virus in Syrian hamsters and the characterization of the isolates from Russia

Puumala virus (PUUV) and other Arvicolinae-borne hantaviruses are difficult to cultivate in cell culture. To isolate these hantaviruses efficiently, hantavirus nucleocapsid protein (NP)-positive but seronegative wild rodents were selected by NP-detection ELISA. Three of 68 Myodes glareolus captured in Samara, Russia, were NP-positive and seronegative. Syrian hamsters were inoculated with lung homogenates from NP-positive rodents for virus propagation. Virus isolation in vitro was carried out by inoculation of lung homogenates of NP-positive hamsters to Vero E6 cell monolayers. Two PUUV strains (Samara49/CG/2005 and Samara94/CG/2005) from M. glareolus were isolated in Vero E6 cells. Nucleotide and amino acid sequence identities of the S segment of these isolates to those of PUUV F-s808 from a fatal HFRS patient in Samara region were 96.7-99.3% and 99.3-100.0%, respectively. Morphologic features of Vero E6 cells infected with PUUV strain Samara49/CG/2005 were quite similar to those of Hantaan virus-infected cells. Isolation of Hokkaido virus from Myodes rufocanus captured in Hokkaido, Japan, was also performed. Hokkaido virus NP and RNA were recovered and maintained in hamsters. These results suggest that inoculation of Syrian hamsters with rodent samples is an efficient method for the isolation and maintenance of PUUV and other Arvicolinae-borne hantaviruses.