Innate lymphoid cells are activated in HFRS, and their function can be modulated by hantavirus-induced type I interferons.

Hantaviruses cause the acute zoonotic diseases hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Infected patients show strong systemic inflammation and immune cell activation. NK cells are highly activated in HFRS, suggesting that also other innate lymphoid cells (ILCs) might be responding to infection. Here, we characterized peripheral ILC responses, and measured plasma levels of soluble factors and plasma viral load, in 17 Puumala virus (PUUV)-infected HFRS patients. This revealed an increased frequency of ILC2 in patients, in particular the ILC2 lineage-committed c-Kitlo ILC2 subset. Patients' ILCs showed an activated profile with increased proliferation and displayed altered expression of several homing markers. How ILCs are activated during viral infection is largely unknown. When analyzing PUUV-mediated activation of ILCs in vitro we observed that this was dependent on type I interferons, suggesting a role for type I interferons-produced in response to virus infection-in the activation of ILCs. Further, stimulation of naïve ILC2s with IFN-ß affected ILC2 cytokine responses in vitro, causing decreased IL-5 and IL-13, and increased IL-10, CXCL10, and GM-CSF secretion. These results show that ILCs are activated in HFRS patients and suggest that the classical antiviral type I IFNs are involved in shaping ILC functions.

Orthohantaviruses in Misiones Province, Northeastern Argentina.

Few cases of hantavirus pulmonary syndrome have been reported in northeastern Argentina. However, neighboring areas show a higher incidence, suggesting underreporting. We evaluated the presence of antibodies against orthohantavirus in small rodents throughout Misiones province. Infected Akodon affinis montensis and Oligoryzomys nigripes native rodents were found in protected areas of Misiones.

Seroprevalence of hantavirus infection in non-epidemic settings over four decades: a systematic review and meta-analysis.

INTRODUCTION: Hantavirus infection is a zoonotic disease from rodents to humans, necessitating seroprevalence assessment for disease burden clarification and control measure implementation. This study aimed to estimate global hantaviruses seroprevalence, examining variations by regions, populations or settings. METHODS: A comprehensive database search identified studies on human hantaviruses seroprevalence using IgG detection until january 2024. A random-effects meta-analysis estimated pooled seroprevalence, with subgroup analyses for geographical region, population, setting or occupation. RESULTS: Out of 3,382 abstracts reviewed, 110 studies were selected, comprising 81,815 observations and 3207 events. The global seroprevalence was calculated at 2.93% (2.34%-3.67%). In terms of geographical distribution, our analysis encompassed 61 studies from the Americas, where the seroprevalence was estimated at 2.43% (95% CI: 1.71%-3.46%), 33 studies from Europe indicating a seroprevalence of 2.98% (95% CI: 2.19%-4.06%), 10 studies from Asia revealing a seroprevalence of 6.84% (95% CI: 3.64%-12.50%), and 6 studies from Africa demonstrating a seroprevalence of 2.21% (95% CI: 1.82%-2.71%). Subgroup analysis underscored varying seroprevalence rates across different populations, settings, and occupations, highlighting the necessity for targeted interventions and preventive measures. CONCLUSION: The analysis reveals a moderate global hantaviruses seroprevalence, emphasizing the viral family's complex transmission dynamics influenced by exposure and geographical factors. This highlights the need for targeted prevention and control strategies.

Hantavirus infection-induced B cell activation elevates free light chains levels in circulation.

In humans, orthohantaviruses can cause hemorrhagic fever with renal syndrome (HFRS) or hantavirus pulmonary syndrome (HPS). An earlier study reported that acute Andes virus HPS caused a massive and transient elevation in the number of circulating plasmablasts with specificity towards both viral and host antigens suggestive of polyclonal B cell activation. Immunoglobulins (Igs), produced by different B cell populations, comprise heavy and light chains; however, a certain amount of free light chains (FLCs) is constantly present in serum. Upregulation of FLCs, especially clonal species, associates with renal pathogenesis by fibril or deposit formations affecting the glomeruli, induction of epithelial cell disorders, or cast formation in the tubular network. We report that acute orthohantavirus infection increases the level of Ig FLCs in serum of both HFRS and HPS patients, and that the increase correlates with the severity of acute kidney injury in HFRS. The fact that the kappa to lambda FLC ratio in the sera of HFRS and HPS patients remained within the normal range suggests polyclonal B cell activation rather than proliferation of a single B cell clone. HFRS patients demonstrated increased urinary excretion of FLCs, and we found plasma cell infiltration in archival patient kidney biopsies that we speculate to contribute to the observed FLC excreta. Analysis of hospitalized HFRS patients' peripheral blood mononuclear cells showed elevated plasmablast levels, a fraction of which stained positive for Puumala virus antigen. Furthermore, B cells isolated from healthy donors were susceptible to Puumala virus in vitro, and the virus infection induced increased production of Igs and FLCs. The findings propose that hantaviruses directly activate B cells, and that the ensuing intense production of polyclonal Igs and FLCs may contribute to acute hantavirus infection-associated pathological findings.

RIG-I-like receptor activation drives type I IFN and antiviral signaling to limit Hantaan orthohantavirus replication.

Pathogenic hantaviruses, genus Orthohantaviridae, are maintained in rodent reservoirs with zoonotic transmission to humans occurring through inhalation of rodent excreta. Hantavirus disease in humans is characterized by localized vascular leakage and elevated levels of circulating proinflammatory cytokines. Despite the constant potential for deadly zoonotic transmission to humans, specific virus-host interactions of hantaviruses that lead to innate immune activation, and how these processes impart disease, remain unclear. In this study, we examined the mechanisms of viral recognition and innate immune activation of Hantaan orthohantavirus (HTNV) infection. We identified the RIG-I-like receptor (RLR) pathway as essential for innate immune activation, interferon (IFN) production, and interferon stimulated gene (ISG) expression in response to HTNV infection in human endothelial cells, and in murine cells representative of a non-reservoir host. Our results demonstrate that innate immune activation and signaling through the RLR pathway depends on viral replication wherein the host response can significantly restrict replication in target cells in a manner dependent on the type 1 interferon receptor (IFNAR). Importantly, following HTNV infection of a non-reservoir host murine model, IFNAR-deficient mice had higher viral loads, increased persistence, and greater viral dissemination to lung, spleen, and kidney compared to wild-type animals. Surprisingly, this response was MAVS independent in vivo. Innate immune profiling in these tissues demonstrates that HTNV infection triggers expression of IFN-regulated cytokines early during infection. We conclude that the RLR pathway is essential for recognition of HTNV infection to direct innate immune activation and control of viral replication in vitro, and that additional virus sensing and innate immune response pathways of IFN and cytokine regulation contribute to control of HTNV in vivo. These results reveal a critical role for innate immune regulation in driving divergent outcomes of HTNV infection, and serve to inform studies to identify therapeutic targets to alleviate human hantavirus disease.

Seroprevalence, cross antigenicity and circulation sphere of bat-borne hantaviruses revealed by serological and antigenic analyses.

Bats are newly identified reservoirs of hantaviruses (HVs) among which very divergent HVs have been discovered in recent years. However, their significance for public health remains unclear since their seroprevalence as well as antigenic relationship with human-infecting HVs have not been investigated. In the present study archived tissues of 1,419 bats of 22 species from 6 families collected in 5 south and southwest provinces in China were screened by pan-HV RT-PCR following viral metagenomic analysis. As a result nine HVs have been identified in two bat species in two provinces and phylogenetically classified into two species, Laibin virus (LAIV, ICTV approved species, 1 strain) and Xuan son virus (XSV, proposed species, 8 strains). Additionally, 709 serum samples of these bats were also analyzed by ELISA to investigate the seroprevalence and cross-reactivity between different HVs using expressed recombinant nucleocapsid proteins (rNPs) of LAIV, XSV and Seoul virus (SEOV). The cross-reactivity of some bat sera were further confirmed by western blot (WB) using three rNPs followed by fluorescent antibody virus neutralization test (FAVNT) against live SEOV. Results showed that the total HV seropositive rate of bat sera was 18.5% (131/709) with many cross reacting with two or all three rNPs and several able to neutralize SEOV. WB analysis using the three rNPs and their specific hyperimmune sera demonstrated cross-reactivity between XSV/SEOV and LAIV/XSV, but not LAIV/SEOV, indicating that XSV is antigenically closer to human-infecting HVs. In addition a study of the distribution of the viruses identified an area covering the region between Chinese Guangxi and North Vietnam, in which XSV and LAIV circulate within different bat colonies with a high seroprevalence. A circulation sphere of bat-borne HVs has therefore been proposed.

Serological methods for detection of infection with shrew-borne hantaviruses: Thottapalayam, Seewis, Altai, and Asama viruses.

The infectivity of shrew-borne hantaviruses to humans is still unclear because of the lack of a serodiagnosis method for these viruses. In this study, we prepared recombinant nucleocapsid (rN) proteins of Seewis orthohantavirus, Altai orthohantavirus (ALTV), Thottapalayam thottimvirus (TPMV), and Asama orthohantavirus. Using monospecific rabbit sera, no antigenic cross-reactivity was observed. In a serosurvey of 104 samples from renal patients and 271 samples from heathy controls from Sri Lanka, one patient serum and two healthy control sera reacted with rN proteins of ALTV and TPMV, respectively. The novel assays should be applied to investigate potential infectivity of shrew-borne hantaviruses to humans.

Heterozygous TLR3 Mutation in Patients with Hantavirus Encephalitis.

Puumala hantavirus (PUUV) hemorrhagic fever with renal syndrome (HFRS) is common in Northern Europe; this infection is usually self-limited and severe complications are uncommon. PUUV and other hantaviruses, however, can rarely cause encephalitis. The pathogenesis of these rare and severe events is unknown. In this study, we explored the possibility that genetic defects in innate anti-viral immunity, as analogous to Toll-like receptor 3 (TLR3) mutations seen in HSV-1 encephalitis, may explain PUUV encephalitis. We completed exome sequencing of seven adult patients with encephalitis or encephalomyelitis during acute PUUV infection. We found heterozygosity for the TLR3 p.L742F novel variant in two of the seven unrelated patients (29%, p = 0.0195). TLR3-deficient P2.1 fibrosarcoma cell line and SV40-immortalized fibroblasts (SV40-fibroblasts) from patient skin expressing mutant or wild-type TLR3 were tested functionally. The TLR3 p.L742F allele displayed low poly(I:C)-stimulated cytokine induction when expressed in P2.1 cells. SV40-fibroblasts from three healthy controls produced increasing levels of IFN-λ and IL-6 after 24 h of stimulation with increasing concentrations of poly(I:C), whereas the production of the cytokines was impaired in TLR3 L742F/WT patient SV40-fibroblasts. Heterozygous TLR3 mutation may underlie not only HSV-1 encephalitis but also PUUV hantavirus encephalitis. Such possibility should be further explored in encephalitis caused by these and other hantaviruses.

Peritonitis secondary to hemorrhagic fever with renal syndrome: a case report in GuangZhou China.

BACKGROUND: Hantavirus infection is worldwide epidemic and can cause life-threatening consequences. With more and more cases reported in countries with atypical morbidity, it is necessarily urgent to know some atypical symptoms and signs of Hantavirus infection. CASE PRESENTATION: Here we report the case of a 44-year old male with a complaint of fever and diffuse abdominal pain, initially suspiciously diagnosed with acute peritonitis. The patient was eventually diagnosed as hemorrhagic fever with renal syndrome and enhanced CT scan showed peritonitis. The clinical condition of the patient was relatively mild and he was recovered 9 days later. CONCLUSION: Peritonitis secondary to hemorrhagic fever with renal syndrome is rare in clinically practice. When confronted with atypical celialgia, it is important to make differential diagnosis of hantavirus infection.

Continuous renal replacement therapy rescues severe haemorrhagic fever with renal syndrome in pregnancy: a case report.

BACKGROUND: Haemorrhagic fever with renal syndrome (HFRS) is a natural epidemic disease caused by various types of viruses of the genus Hantavirus, which are mainly transmitted by contact with the infected rodents and their droppings. Pregnancy complicated with HFRS is rare; however, adverse maternal and foetal outcomes may be noted. In this report, we describe a case involving a pregnant woman with HFRS who was in a state of multiple organ dysfunction syndrome (MODS) and was successfully treated with continuous renal replacement therapy (CRRT). CASE PRESENTATION: A 32-year-old pregnant woman at 29 weeks of gestation was hospitalised for a fever and upper respiratory tract infection due to HFRS in winter. Persistent fever, coagulation disorder, thrombocytopenia, electrolyte imbalance, abnormal liver function, and renal failure were noted during the progression of the disease. The patient was treated with CRRT. She recovered after 21 days, and delivered a live infant by caesarean section at 38 weeks of gestation. Furthermore, obvious abnormalities were not detected during the follow-up of the mother and infant at 42 days, 3 months, 6 months, and 1 year after the delivery. CONCLUSIONS: Early diagnosis, timely application of CRRT, and comprehensive treatment may be essential for the successful treatment of patients with HFRS during pregnancy.

When polyuria does not stop: a case report on an unusual complication of hantavirus infection.

BACKGROUND: The clinical features, course and outcome of hantavirus infection is highly variable. Symptoms of the central nervous system may occur, but often present atypically and diagnostically challenging. Even though the incidence of hantavirus infection is increasing worldwide, this case is the first to describe diabetes insipidus centralis as a complication of hantavirus infection in the Western world. CASE PRESENTATION: A 49-year old male presenting with severe headache, nausea and photophobia to our neurology department was diagnosed with acute haemorrhage in the pituitary gland by magnetic resonance imaging. In the following days, the patient developed severe oliguric acute kidney failure. Diagnostic workup revealed a hantavirus infection, so that the pituitary haemorrhage resulting in hypopituitarism was seen as a consequence of hantavirus-induced hypophysitis. Under hormone replacement and symptomatic therapy, the patient's condition and kidney function improved considerably, but significant polyuria persisted, which was initially attributed to recovery from kidney injury. However, water deprivation test revealed central diabetes insipidus, indicating involvement of the posterior pituitary gland. The amount of urine production normalized with desmopressin substitution. CONCLUSION: Our case report highlights that neurological complications of hantavirus infection should be considered in patients with atypical clinical presentation.

Molecular Epidemiology of Hantaviruses in the Czech Republic.

During 2008-2018, we collected samples from rodents and patients throughout the Czech Republic and characterized hantavirus isolates. We detected Dobrava-Belgrade and Puumala orthohantaviruses in patients and Dobrava-Belgrade, Tula, and Seewis orthohantaviruses in rodents. Increased knowledge of eco-epidemiology of hantaviruses will improve awareness among physicians and better outcomes of patients.

Infection with New York Orthohantavirus and Associated Respiratory Failure and Multiple Cerebral Complications.

We report a case of infection with New York orthohantavirus in a woman who showed renal impairment and hemorrhage, complicated by hydrocephalus, in Long Island, New York, USA. Phylogenetic analysis showed that this virus was genetically similar to a New York orthohantavirus isolated in the same region during 1993.

Defining of MAbs-neutralizing sites on the surface glycoproteins Gn and Gc of a hantavirus using vesicular stomatitis virus pseudotypes and site-directed mutagenesis.

Earlier four monoclonal antibodies (MAbs) against surface glycoproteins Gn and Gc of puumala virus (PUUV, genus Orthohantavirus, family Hantaviridae, order Bunyavirales) were generated and for three MAbs with neutralizing capacity the localization of binding epitopes was predicted using pepscan and phage-display techniques. In this work, we produced vesicular stomatitis virus (VSV) particles pseudotyped with the Gn and Gc glycoproteins of PUUV and applied site-directed mutagenesis to dissect the structure of neutralizing epitopes. Replacement of cysteine amino acid (aa) residues with alanines resulted in pseudotype particles with diminished (16 to 18 %) neut-titres; double Cys→Ala mutants, as well as mutants with bulky aromatic and charged residues replaced with alanines, have shown even stronger reduction in neut-titres (from 25 % to the escape phenotype). In silico modelling of the neut-epitopes supported the hypothesis that these critical residues are located on the surface of viral glycoprotein molecules and thus can be recognized by the antibodies indeed. A similar pattern was observed in experiments with mutant pseudotypes and sera collected from patients suggesting that these neut-epitopes are utilized in a course of human PUUV infection. These data will help understanding the mechanisms of hantavirus neutralization and assist construction of vaccine candidates.

[Fulminant acute kidney injury after cholecystectomy in a 45-year-old female patient]. / Fulminantes akutes Nierenversagen nach Cholezystektomie bei einer 45­jährigen Patientin.

A cholecystectomy was carried out on a 45-year-old female patient with fever, myalgia and right upper abdominal pain because of a suspected cholecystitis. Postoperatively acute kidney injury occurred. A comprehensive medical history taken later revealed a presumed occupational contact to rodents. Serological testing detected a recent infection with Dobrava-Belgrade hantavirus. The kidney function normalized with supportive therapeutic measures. Hantavirus infection should be considered in the differential diagnosis of acute kidney injury combined with fever, myalgia and abdominal pain.

Seroprevalence of hantavirus and Borrelia burgdorferi in Düzce (Turkey) forest villages and the relationship with sociodemographic features

Background/aim: Hantavirus and Borrelia burgdorferi are two zoonotic agents that pose a great risk especially for people living in forest areas. This study aimed to investigate the seroprevalence of hantavirus and B. burgdorferi in forest villages of Düzce and its relationship with sociodemographic features. Materials and methods: The presence of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against hantavirus and B. burgdorferi in serum samples was investigated via enzyme-linked immunosorbent assay (ELISA). Hantavirus IgG and B. burgdorferi IgM and IgG positivity was then validated by western blot (WB) method. Results: During the analyses, 193 serum samples were tested. Eleven (6%) cases of hantavirus IgM was found positive by ELISA. Six (3%) cases of hantavirus IgG, 3 (2%) cases of B. burgdorferi IgM, and 12 (6%) cases of B. burgdorferi IgG were found positive by WB. Borrelia burgdorferi IgG positivity was found to be higher in the 46­70 age group and it was seen that the positivity was the highest among those who lived in mud-brick houses. Conclusion: This study was the first to determine the frequency of hantavirus in the study region and it includes current data for B. burgdorferi. Consequently, it is recommended that similar studies be carried out on rodents in all the regions at risk.

Protective Effectiveness of Inactivated Hantavirus Vaccine Against Hemorrhagic Fever With Renal Syndrome.

As there is no effective treatment against hemorrhagic fever with renal syndrome (HFRS), the development of effective vaccine is important. An inactivated hantavirus vaccine (IHV) has been used in Korea, but there has been controversy regarding its effectiveness. We conducted a case-control study to evaluate the vaccine effectiveness (VE) of IHV against HFRS in the Korean military. Unadjusted and adjusted VEs of IHV were 59.1% and 58.9%, respectively. VE was higher in divisions with high incidence of HFRS (unadjusted VE, 71.4%; adjusted VE, 78.7%). Our study demonstrated the moderate effectiveness of IHV in high-risk populations residing in endemic area.

Delayed Interferon Type 1-Induced Antiviral State Is a Potential Factor for Hemorrhagic Fever With Renal Syndrome Severity.

Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. Interferon (IFN) responses play an important role in HFRS pathogenesis and early IFN-ß response is delayed by pathogenic hantaviruses. The severity of HFRS caused by Dobrava virus (DOBV) and Puumala virus (PUUV) varies. Our aim was to determine whether differences in early activation of IFN type 1-induced antiviral state influence HFRS severity. Peripheral blood mononuclear cells (PBMCs) from healthy donors and HFRS patients were stimulated with DOBV or PUUV and expression of selected genes was measured. PUUV, but not DOBV, activated IFN type 1-induced antiviral state in stimulated PBMCs, and IFNß, STAT-1, and MxA were highly upregulated. Upregulation of MxA was earlier in acute-phase PBMCs and higher in convalescent-phase PBMCs from patients with mild compared with severe PUUV infection. Our study showed that delayed IFN type 1-induced antiviral state could contribute to HFRS severity, particularly in PUUV infection.

Maripa Virus RNA Load and Antibody Response in Hantavirus Pulmonary Syndrome, French Guiana.

We report viral RNA loads and antibody responses in 6 severe human cases of Maripa virus infection (2 favorable outcomes) and monitored both measures during the 6-week course of disease in 1 nonfatal case. Further research is needed to determine prevalence of this virus and its effect on other hantaviruses.

Spatiotemporal analysis and forecasting model of hemorrhagic fever with renal syndrome in mainland China.

Hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses is a serious public health problem in China, accounting for 90% of HFRS cases reported globally. In this study, we applied geographical information system (GIS), spatial autocorrelation analyses and a seasonal autoregressive-integrated moving average (SARIMA) model to describe and predict HFRS epidemic with the objective of monitoring and forecasting HFRS in mainland China. Chinese HFRS data from 2004 to 2016 were obtained from National Infectious Diseases Reporting System (NIDRS) database and Chinese Centre for Disease Control and Prevention (CDC). GIS maps were produced to detect the spatial distribution of HFRS cases. The Moran's I was adopted in spatial global autocorrelation analysis to identify the integral spatiotemporal pattern of HFRS outbreaks, while the local Moran's Ii was performed to identify 'hotspot' regions of HFRS at province level. A fittest SARIMA model was developed to forecast HFRS incidence in the year 2016, which was selected by Akaike information criterion and Ljung-Box test. During 2004-2015, a total of 165 710 HFRS cases were reported with the average annual incidence at province level ranged from 0 to 13.05 per 100 000 persons. Global Moran's I analysis showed that the HFRS outbreaks presented spatially clustered distribution, with the degree of cluster gradually decreasing from 2004 to 2009, then turned out to be randomly distributed and reached lowest point in 2012. Local Moran's Ii identified that four provinces in northeast China contributed to a 'high-high' cluster as a traditional epidemic centre, and Shaanxi became another HFRS 'hotspot' region since 2011. The monthly incidence of HFRS decreased sharply from 2004 to 2009 in mainland China, then increased markedly from 2010 to 2012, and decreased again since 2013, with obvious seasonal fluctuations. The SARIMA ((0,1,3) × (1,0,1)12) model was the most fittest forecasting model for the dataset of HFRS in mainland China. The spatiotemporal distribution of HFRS in mainland China varied in recent years; together with the SARIMA forecasting model, this study provided several potential decision supportive tools for the control and risk-management plan of HFRS in China.