Life-threatening Dobrava hantavirus infection with unusually extended pulmonary involvement

Orthohantavirus Pathogenesis and Cell Tropism

Orthohantaviruses are zoonotic viruses that are naturally maintained by persistent infection in specific reservoir species. Although these viruses mainly circulate among rodents worldwide, spill-over infection to humans occurs. Orthohantavirus infection in humans can result in two distinct clinical outcomes: hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). While both syndromes develop following respiratory transmission and are associated with multi-organ failure and high mortality rates, little is known about the mechanisms that result in these distinct clinical outcomes. Therefore, it is important to identify which cell types and tissues play a role in the differential development of pathogenesis in humans. Here, we review current knowledge on cell tropism and its role in pathogenesis during orthohantavirus infection in humans and reservoir rodents. Orthohantaviruses predominantly infect microvascular endothelial cells (ECs) of a variety of organs (lungs, heart, kidney, liver, and spleen) in humans. However, in this review we demonstrate that other cell types (e.g., macrophages, dendritic cells, and tubular epithelium) are infected as well and may play a role in the early steps in pathogenesis. A key driver for pathogenesis is increased vascular permeability, which can be direct effect of viral infection in ECs or result of an imbalanced immune response in an attempt to clear the virus. Future studies should focus on the role of identifying how infection of organ-specific endothelial cells as well as other cell types contribute to pathogenesis.

Proteinuria and the Clinical Course of Dobrava-Belgrade Hantavirus Infection

Purpose

Human infection with Dobrava-Belgrade virus (DOBV) in Northern Germany causes a mild form of hantavirus disease predominantly characterized by acute kidney injury due to interstitial nephritis. We evaluated the largest number of DOBV-infected patients so far regarding clinical course, proteinuria, and prognostic markers.

Patients and Methods

Patients with DOBV-associated hantavirus disease admitted to the Renal Division of the University of Lübeck (Germany) between 1997 and 2012 were included in this study. Symptoms, clinical course, laboratory parameters, and urinary protein analysis were investigated at admission (baseline, t₀), 3–5 days (t_3–5), 10–17 days (t_10–17), and after 1 year of follow-up (t₃₆₅).

Results

Of the 34 patients (male/female ratio: 23/11; age: 41 ± 14 years) included in the study, 4 underwent hemodialysis (HD). Glomerular filtration rate was 17 ± 14 mL/min at t₀ and increased to 27 ± 26 mL/min (t_3–5), 57 ± 20 mL/min (t_10–17), and 84 ± 16 mL/min (t₃₆₅). Albuminuria and tubular proteinuria (α₁- and β₂-microglobulin) decreased during follow-up; the urinary α₁-microglobulin concentration in patients who required HD was significantly higher than that in patients not requiring HD (t₀: 186 ± 51 vs. 45 ± 26 mg/g creatinine; t_3–5: 87 ± 14 vs. 32 ± 16 mg/g creatinine; t_10–17: 63 ± 18 vs. 28 ± 12 mg/g creatinine; p < 0.001).

Conclusions

DOBV infection of inpatients in Northern Germany is associated with severe kidney injury that recovers within a few weeks and normalizes within 1 year. Tubular proteinuria is associated with the severity of kidney injury and the necessity of renal replacement therapy in these DOBV-infected patients.

Hantavirus disease in Germany due to infection with Dobrava-Belgrade virus genotype Kurkino

Members of the Dobrava-Belgrade virus (DOBV) species are hantaviruses carried by different Apodemus mice as reservoir hosts and causing haemorrhagic fever with renal syndrome (HFRS) in humans. In Central Europe, the Kurkino genotype of DOBV, associated with the striped field mouse, Apodemus agrarius, is prevalent. This paper presents the first extensive study of the serological and molecular diagnostics, epidemiology and clinics of DOBV-Kurkino infections in Central Europe. Serum samples from 570 German patients living in the habitat of A. agrarius (north and northeast Germany) and exhibiting febrile disease, were analysed. All samples were tested by ELISA, subsets of samples were also analysed by immunoblot, neutralization assay, and RT-PCR. A group of 86 individuals was confirmed as DOBV-infected. The virus neutralization assay allowed a reliable identification of DOBV antibodies during both acute and convalescent phases of infection. However, differentiation of relevant DOBV genotypes was not possible by neutralization test but required molecular analysis. Whereas DOBV IgM antibodies tend to persist in the infected organism, RNAaemia seems to be short. Nucleotide sequences were amplified from four patients, and their analysis demonstrated infection by DOBV-Kurkino. With respect to the initial results, the high degree of identity of local patient-derived and A. agrarius-derived virus sequences may allow a closer allocation of the geographical place where the human infection occurred. In contrast to moderate/severe HFRS caused by the DOBV genotypes Dobrava or Sochi, all available data showed a mild clinical course of HFRS caused by DOBV-Kurkino infection without lethal outcomes.

Complex evolution and epidemiology of Dobrava-Belgrade hantavirus: definition of genotypes and their characteristics

Dobrava-Belgrade virus (DOBV) is a human pathogen that has evolved in, and is hosted by, mice of several species of the genus Apodemus. We propose a subdivision of the species Dobrava-Belgrade virus into four related genotypes - Dobrava, Kurkino, Saaremaa, and Sochi - that show characteristic differences in their phylogeny, specific host reservoirs, geographical distribution, and pathogenicity for humans.

Hantavirus infections in Europe and their impact on public health

Hantaviruses (genus Hantavirus, family Bunyaviridae) are enveloped tri-segmented negative-stranded RNA viruses each carried by a specific rodent or insectivore host species. Several different hantaviruses known to infect humans circulate in Europe. The most common is Puumala (PUUV) carried by the bank vole; another two important, genetically closely related ones are Dobrava-Belgrade (DOBV) and Saaremaa viruses (SAAV) carried by Apodemus mice (species names follow the International Committee on Taxonomy of Viruses nomenclature). Of the two hantaviral diseases, hemorrhagic fever with renal syndrome (HFRS) and hantaviral cardiopulmonary syndrome, the European viruses cause only HFRS: DOBV with often severe symptoms and a high case fatality rate, and PUUV and SAAV more often mild disease. More than 10,000 HFRS cases are diagnosed annually in Europe and in increasing numbers. Whether this is because of increasing recognition by the medical community or due to environmental factors such as climate change, or both, is not known. Nevertheless, in large areas of Europe, the population has a considerable seroprevalence but only relatively few HFRS cases are reported. Moreover, no epidemiological data are available from many countries. We know now that cardiac, pulmonary, ocular and hormonal disorders are, besides renal changes, common during the acute stage of PUUV and DOBV infection. About 5% of hospitalized PUUV and 16%-48% of DOBV patients require dialysis and some prolonged intensive-care treatment. Although PUUV-HFRS has a low case fatality rate, complications and long-term hormonal, renal, and cardiovascular consequences commonly occur. No vaccine or specific therapy is in general use in Europe. We conclude that hantaviruses have a significant impact on public health in Europe.

Molecular diagnostics of hemorrhagic fever with renal syndrome during a Dobrava virus infection outbreak in the European part of Russia

A large outbreak of hemorrhagic fever with renal syndrome (HFRS) occurred in the winter of 2006-2007 in a region southeast of Moscow in Central European Russia. Of the 422 patients with HFRS investigated in this study, 58 patients were found to be infected by Puumala virus, whereas as many as 364 were infected by Dobrava-Belgrade virus (DOBV). Early serum samples from 10 DOBV-infected patients were used for nucleic acid amplification, which was successful for 5 patients. Molecular analyses demonstrated that the causative hantavirus belongs to the DOBV-Aa genetic lineage, which is carried by the striped field mouse (Apodemus agrarius) as the natural reservoir host. Neutralization assays with convalescent-phase sera from these patients confirmed infection by DOBV-Aa; related viruses, such as the Dobrava-Slovenia virus (DOBV-Af) and the Dobrava-Sochi virus (DOBV-Ap), were neutralized at lower efficiencies. The clinical courses of the 205 patients enrolled in the study were found to be mostly mild to moderate; however, an unexpectedly high fraction (27%) of patients exhibited severe illness. One patient died from kidney failure and showed symptoms of generalized subcutaneous hemorrhage. The results provide molecular, serodiagnostic, and clinical evidence that DOBV-Aa is a common pathogen in East Europe that causes large outbreaks of HFRS.

Hemorrhagic fever with renal syndrome caused by 2 lineages of Dobrava hantavirus, Russia

Dobrava-Belgrade virus (DOBV) is a European hantavirus that causes hemorrhagic fever with renal syndrome (HFRS); case-fatality rates in Balkan countries are as high as 12%. To determine causative agents, we examined 126 cases of DOBV-associated HFRS in central and southern European Russia. In central Russia (Lipetsk, Voronezh, Orel regions), outbreaks were caused by a DOBV variant (DOBV-Aa) carried by Apodemus agrarius. In southern Russia (Sochi district), where HFRS is endemic, HFRS cases were caused by a new DOBV variant (DOBV-Ap), found in A. ponticus, a novel hantavirus natural host. Both viruses, DOBV-Aa/Lipetsk and DOBV-Ap/Sochi, were isolated through Vero E6 cells, genetically characterized, and used for serotyping of the HFRS patients' serum. The clinical severity of HFRS caused by DOBV-Aa resembles that of HFRS caused by Puumala virus (mild to moderate); clinical severity of disease caused by DOBV-Ap infections is more often moderate to severe.

Detection and typing of human pathogenic hantaviruses by real-time reverse transcription-PCR and pyrosequencing

BACKGROUND

Because the clinical course of human infections with hantaviruses can vary from subclinical to fatal, rapid and reliable detection of hantaviruses is essential. To date, the diagnosis of hantavirus infection is based mainly on serologic assays, and the detection of hantaviral RNA by the commonly used reverse transcription (RT)-PCR is difficult because of high sequence diversity of hantaviruses and low viral loads in clinical specimens.

METHODS

We developed 5 real-time RT-PCR assays, 3 of which are specific for the individual European hantaviruses Dobrava, Puumala, or Tula virus. Two additional assays detect the Asian species Hantaan virus together with Seoul virus and the American species Andes virus together with Sin Nombre virus. Pyrosequencing was established to provide characteristic sequence information of the amplified hantavirus for confirmation of the RT-PCR results or for a more detailed virus typing.

RESULTS

The real-time RT-PCR assays were specific for the respective hantavirus species and optimized to run on 2 different platforms, the LightCycler and the ABI 7900/7500. Each assay showed a detection limit of 10 copies of a plasmid containing the RT-PCR target region, and pyrosequencing was possible with 10 to 100 copies per reaction. With this assay, viral genome could be detected in 16 of 552 (2.5%) specimens of suspected hantavirus infections of humans and mice.

CONCLUSIONS

The new assays detect, differentiate, and quantify hantaviruses in clinical specimens from humans and from their natural hosts and may be useful for in vitro studies of hantaviruses.

Detection of Dobrava hantaviruses in Apodemus agrarius mice in the Transdanubian region of Hungary

Dobrava hantavirus (DOBV) belongs to the genus Hantavirus of the family Bunyaviridae, and is carried by yellow necked and striped field mice (Apodemus flavicollis and Apodemus agrarius), respectively. The aim of this study was to detect and genetically characterize new DOBV strains in rodents captured in the Transdanubian region of Hungary. Rodent corpses were dissected and lung tissues were used for hantavirus detection by SYBR Green-based real-time RT-PCR using specific primers located in the S-segment of the virus genome. A total of 22 captured animals of the Apodemus species were tested for the presence of DOBV. Three out of the 22 mice were positive. Phylogenetic and molecular sequence analyses showed that Hungarian DOBVs were most closely related to those viruses detected from A. agrarius mice in Slovenia. Based on our new data from the region we concluded that extended reservoir studies would be necessary in the future.

Corticosteroids combined with continuous veno-venous hemodiafiltration for treatment of hantavirus pulmonary syndrome caused by Puumala virus infection

Reported here are two cases of hantavirus pulmonary syndrome caused by Puumala virus infection, which rapidly resolved after initiation of corticosteroid treatment combined with continuous veno-venous hemodiafiltration. These cases emphasize the role of the inflammatory response in the pathogenesis of hantavirus pulmonary syndrome.

Central European Dobrava Hantavirus isolate from a striped field mouse (Apodemus agrarius)

Dobrava virus (DOBV) is a hantavirus that causes hemorrhagic fever with renal syndrome (HFRS) in Europe. It is hosted by at least two rodent species, Apodemus flavicollis and A. agrarius. According to their natural hosts they form the distinct genetic lineages DOBV-Af and DOBV-Aa, respectively. We have now established a DOBV isolate named Slovakia (SK/Aa) from an A. agrarius animal captured in Slovakia. The complete S and M and partial L segment nucleotide sequences of the new isolate were determined. Phylogenetic analyses showed that the SK/Aa isolate clustered together with the other DOBV-Aa sequences amplified from A. agrarius before and can be taken as the representative of this genetic lineage. SK/Aa, in comparison with a DOBV-Af isolate, was used for serotyping neutralizing antibodies of HFRS patients in Central Europe. Most patients' sera exhibited a higher endpoint titer when probed with our new isolate, suggesting that DOBV-Aa strains are responsible for most of the DOBV-caused HFRS cases in this region.