Serum Cytokine Profiles Differentiating Hemorrhagic Fever with Renal Syndrome and Hantavirus Pulmonary Syndrome

Canonical effects of cytokines on glomerulonephritis: A new outlook in nephrology

Glomerulonephritis (GN) is an important cause of renal inflammation resulting from kidney-targeted adaptive and innate immune responses and consequent glomerular damage. Given the lack of autoantibodies, immune complexes, or the infiltrating immune cells in some forms of GN, for example, focal segmental glomerulosclerosis and minimal change disease, along with paraneoplastic syndrome and a special form of renal involvement in some viral infections, the likeliest causative scenario would be secreted factors, mainly cytokine(s). Since cytokines can modulate the inflammatory mechanisms, severity, and clinical outcomes of GN, it is rational to consider the umbrella term of cytokine GN as a new outlook to reclassify a group of previously known GN. We focus here, particularly, on cytokines that have the central "canonical effect" in the development of GN.

A pan-orthohantavirus human lung xenograft mouse model and its utility for preclinical studies

Orthohantaviruses are emerging zoonotic viruses that can infect humans via the respiratory tract. There is an unmet need for an in vivo model to study infection of different orthohantaviruses in physiologically relevant tissue and to assess the efficacy of novel pan-orthohantavirus countermeasures. Here, we describe the use of a human lung xenograft mouse model to study the permissiveness for different orthohantavirus species and to assess its utility for preclinical testing of therapeutics. Following infection of xenografted human lung tissues, distinct orthohantavirus species differentially replicated in the human lung and subsequently spread systemically. The different orthohantaviruses primarily targeted the endothelium, respiratory epithelium and macrophages in the human lung. A proof-of-concept preclinical study showed treatment of these mice with a virus neutralizing antibody could block Andes orthohantavirus infection and dissemination. This pan-orthohantavirus model will facilitate progress in the fundamental understanding of pathogenesis and virus-host interactions for orthohantaviruses. Furthermore, it is an invaluable tool for preclinical evaluation of novel candidate pan-orthohantavirus intervention strategies.

A Comprehensive Analysis Exploring the Vital Role of the Systemic Immune-Inflammatory Index Upon Admission in Severe Hemorrhagic Fever with Renal Syndrome

Objective

To explore the value of the systemic immune-inflammatory index (SII) and the systemic inflammatory response index (SIRI) in patients with severe hemorrhagic fever with renal syndrome (HFRS) upon admission.

Methods

This study included a total of 165 patients with HFRS, who were divided into mild and severe groups based on the severity of the disease. By reviewing medical records, we collected the white blood cell (WBC), SII, and SIRI values of patients upon admission. Univariate and multivariate logistics regression analyses were performed to identify risk factors for severe HFRS. The receiver operating characteristic (ROC) curve was applied to calculate the area under the ROC curve (AUC) to analyze the predictive value of SII and SIRI for severe HFRS, and the results were compared with WBC and SIRI.

Results

Compared with the mild HFRS group, patients in the severe HFRS group had a longer duration of illness (P < 0.05), higher levels of WBC, neutrophil (NEUT), lymphocyte (LYMP), monocyte (MONO), procalcitonin (PCT), SIRI, alanine transaminase (ALT), and creatinine (Scr) (P < 0.05), while lower levels of ALB, platelet (PLT), platelet-to-lymphocyte rate (PLR), and SII, with statistically significant differences (P < 0.05). Binary logistics regression analysis indicated that WBC (OR: 1.190, 95% CI: 1.032-1.371), SII (OR: 0.967, 95% CI: 0.951-0.984), and SIRI (OR: 4.743, 95% CI: 2.077-10.830) were risk factors for severe HFRS. The AUCs of WBC, SII, and SIRI for predicting severe HFRS were 0.765, 0.803, and 0.785, respectively.

Conclusion

Low levels of SII and high levels of WBC and SIRI upon admission are risk factors for severe HFRS and have certain value in predicting the progression of HFRS to severe cases, among which SII exhibits the best predictive value.

Replication kinetics of pathogenic Eurasian orthohantaviruses in human mesangial cells

BACKGROUND

Eurasian pathogenic orthohantaviruses cause hemorrhagic fever with renal syndrome (HFRS) characterized by acute kidney injury (AKI). The virulence of orthohantaviruses varies enormously and direct infection of different renal cell types contribute to pathogenesis. Glomerular mesangial cells play an essential role in the interplay between kidney cells and proper kidney function. Therefore, we analyzed the replication competence of different orthohantavirus species in primary mesangial cells and a mesangial cell line.

METHODS

We tested the suitability of the mesangial cell line CIHGM-1 (conditionally immortalized human glomerular mesangial cells) as cell culture model for orthohantavirus kidney infection by comparison with primary human renal mesangial cells (HRMCs). We analyzed infection with high pathogenic Hantaan virus (HTNV), moderate pathogenic Puumala virus (PUUV) and non-/low-pathogenic Tula virus (TULV).

RESULTS

Effective viral spread was observed for PUUV only, whereas infection with HTNV and TULV was abortive. However, in contrast to TULV, HTNV exhibits an initially high infection rate and declines afterwards. This replication pattern was observed in HRMCs and CIHGM-1 cells. Viability or adhesion was neither impaired for PUUV-infected CIHGM-1 nor HRMCs. A loss of migration capacity was observed in PUUV-infected CIHGM-1 cells, but not in HRMCs.

CONCLUSIONS

The identification of differences in the replication competence of pathogenic orthohantavirus strains in renal mesangial cells is of special interest and may provide useful insights in the virus-specific mechanisms of orthohantavirus induced AKI. The use of CIHGM-1 cells will facilitate the research in a relevant cell culture system.

A three-dimensional vessel-on-chip model to study Puumala orthohantavirus pathogenesis

Puumala orthohantavirus (PUUV) infection in humans can result in hemorrhagic fever with renal syndrome. Endothelial cells (ECs) are primarily infected with increased vascular permeability as a central aspect of pathogenesis. Historically, most studies included ECs cultured under static two-dimensional (2D) conditions, thereby not recapitulating the physiological environment due to their lack of flow and inherent pro-inflammatory state. Here, we present a high-throughput model for culturing primary human umbilical vein ECs in 3D vessels-on-chip in which we compared host responses of these ECs to those of static 2D-cultured ECs on a transcriptional level. The phenotype of ECs in vessels-on-chip more closely resembled the in vivo situation due to higher similarity in expression of genes encoding described markers for disease severity and coagulopathy, including IDO1, LGALS3BP, IL6 and PLAT, and more diverse endothelial-leukocyte interactions in the context of PUUV infection. In these vessels-on-chip, PUUV infection did not directly increase vascular permeability, but increased monocyte adhesion. This platform can be used for studying pathogenesis and assessment of possible therapeutics for other endotheliotropic viruses even in high biocontainment facilities.

Treatment of Acute and Long-COVID, Diabetes, Myocardial Infarction, and Alzheimer's Disease: The Potential Role of a Novel Nano-Compound-The Transdermal Glutathione-Cyclodextrin Complex

Oxidative stress (OS) occurs from excessive reactive oxygen species or a deficiency of antioxidants-primarily endogenous glutathione (GSH). There are many illnesses, from acute and post-COVID-19, diabetes, myocardial infarction to Alzheimer's disease, that are associated with OS. These dissimilar illnesses are, in order, viral infections, metabolic disorders, ischemic events, and neurodegenerative disorders. Evidence is presented that in many illnesses, (1) OS is an early initiator and significant promotor of their progressive pathophysiologic processes, (2) early reduction of OS may prevent later serious and irreversible complications, (3) GSH deficiency is associated with OS, (4) GSH can likely reduce OS and restore adaptive physiology, (5) effective administration of GSH can be accomplished with a novel nano-product, the GSH/cyclodextrin (GC) complex. OS is an overlooked pathological process of many illnesses. Significantly, with the GSH/cyclodextrin (GC) complex, therapeutic administration of GSH is now available to reduce OS. Finally, rigorous prospective studies are needed to confirm the efficacy of this therapeutic approach.

The differences in cytokine signatures between severe fever with thrombocytopenia syndrome (SFTS) and hemorrhagic fever with renal syndrome (HFRS)

Severe fever with thrombocytopenia syndrome (SFTS) virus and hantavirus are categorized under the Bunyavirales order. The severe disease progression in both SFTS and hemorrhagic fever with renal syndrome (HFRS) is associated with cytokine storms. This study aimed to explore the differences in cytokine profiles and immune responses between the two diseases. A cross-sectional, single-center study involved 100 participants, comprising 46 SFTS patients, 48 HFRS patients, and 6 healthy controls. The study employed the Luminex cytokine detection platform to measure 48 cytokines. The differences in cytokine profiles and immune characteristics between the two diseases were further analyzed using multiple linear regression, principal component analysis, and random forest method. Among the 48 cytokines tested, 30 showed elevated levels in SFTS and/or HFRS compared to the healthy control group. Furthermore, there were 19 cytokines that exhibited significant differences between SFTS and HFRS. Random forest analysis suggested that TRAIL and CTACK were predictive of SFTS, while IL2Ralpha, MIG, IL-8, IFNalpha2, HGF, SCF, MCP-3, and PDGFBB were more common with HFRS. It was further verified by the receiver operating characteristic with area under the curve >0.8 and P-values <0.05, except for TRAIL. Significant differences were observed in the cytokine profiles of SFTS and HFRS, with TRAIL, IL2Ralpha, MIG, and IL-8 being the top 4 cytokines that most clearly distinguished the two diseases.

IMPORTANCE

SFTS and HFRS differ in terms of cytokine immune characteristics. TRAIL, IL-2Ralpha, MIG, and IL-8 were the top 4 that differed markedly between SFTS and HFRS.

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-β 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.

Sivelestat Inhibits Vascular Endothelial Injury Induced by Inflammatory Response and Improves the Prognosis of Hemorrhagic Fever with Renal Syndrome in Children: An Ambispective Cohort Study

Background

In Asia, Hanta virus (HTNV) results in severe hemorrhagic fever with renal syndrome (HFRS). The efficacy of sivelestat in treating children with HTNV-induced HFRS remains unclear.

Methods

An ambispective cohort study was performed on children diagnosed with HFRS and hospitalized at the Children's Hospital Affiliated to Xi'an Jiaotong University from August 2018 to 2023. Patients who received neutrophil elastin-inhibitor infusion between August 2019 and August 2023 were assigned to the sivelestat group, while patients who did not were assigned to the control group. The independent sample t test was used for inter-group analysis. The Chi-square test and Fisher's exact probability test were used for categorical variables. Spearman correlation test was used to evaluate the correlation between two sets of continuous variables. Kaplan-Meier survival curve and Log -Rank test was used to evaluate the difference in cumulative probability of survival between the two groups.

Results

No significant differences were observed between the two groups in gender, age, contact history, body mass index, HFRS severity, clinical indexes at admission. Compared to the control group, the sivelestat group exhibited a significant decrease in the interleukin-8 level at 48 h (28.5±3 vs 34.5±3.5) and 72 h (21.3±4.5 vs 31.5±5.6) (P<0.05), as well as the ICAM-1 level at 48 h (553±122 vs 784±187) and 72 h (452±130 vs 623±85) (P<0.05). The concentration of VCAM-1 in the sivelestat group exhibited a consistent downward trend. Moreover, the level of VCAM-1 was significantly lower than that in the control group at 24 h (1760±289 vs 2180±445), 48 h (1450±441 vs 1890±267), and 72 h (1149±338 vs 1500±396) (P<0.05). Kaplan-Meier curve analysis revealed a statistically significant difference in the cumulative probability of survival between two groups (P = 0.041). In the secondary outcomes, the sivelestat group demonstrated a decrease in the utilization rate of mechanical ventilation and continuous renal replacement therapy (CRRT).

Conclusion

Sivelestat may suppress neutrophil-mediated inflammatory response to reduce endothelial and organ damage, and improve clinical outcomes in children with severe hemorrhagic fever and renal syndrome.

Design and validation of a novel multi-epitopes vaccine against hantavirus

Hantavirus is a member of the order Bunyavirales and an emerging global pathogen. Hantavirus infections have affected millions of people globally based on available epidemiological data and research studies. Hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) are the two main human diseases associated with hantavirus infections. Hence, efforts are required to develop a potent vaccine against the pathogen. The only vaccine that is in use for hantavirus is an inactivated virus vaccine, "Hantavax", but it failed to produce neutralizing antibodies. Vaccine development is of much importance in dealing with the surge of hantavirus globally. In this study, hantavirus five proteins (N protein, G1 and G2, L protein, and non-structural proteins) were used in NetCTL 1.2 program to predict T-cell epitopes. To predict major histocompatibility complex (MHC) binding alleles, an immune epitope database (IEDB) was used. All predicted epitopes were then investigated for different immunoinformatics analyses such as antigenicity and toxicity analyses. The good water-soluble, non-toxic, probable antigenic, and DRB*0101 binder was selected. A multi-epitopes-based vaccine designing was then done where linkers were used to connect the shortlisted epitopes. In addition, an adjuvant molecule was supplementary to the multi-epitopes peptide to improve the vaccine's immunogenic potential. The final vaccine construct's three-dimensional structure was modeled by ab initio method. The vaccine molecule was then evaluated for its binding potential with TLR-3 immune receptor, which is key for its recognition and processing by the host immune system. Docking studies were performed using HADDOCK software. The best-docked complex was selected and visualized for intermolecular binding and interactions using UCSF Chimera 1.16 software. The findings revealed that the designed vaccine might be a potential vaccine against hantavirus and can be used in experimental animal model testings.Communicated by Ramaswamy H. Sarma.

Disparate macrophage responses are linked to infection outcome of Hantan virus in humans or rodents

Hantaan virus (HTNV) is asymptomatically carried by rodents, yet causes lethal hemorrhagic fever with renal syndrome in humans, the underlying mechanisms of which remain to be elucidated. Here, we show that differential macrophage responses may determine disparate infection outcomes. In mice, late-phase inactivation of inflammatory macrophage prevents cytokine storm syndrome that usually occurs in HTNV-infected patients. This is attained by elaborate crosstalk between Notch and NF-κB pathways. Mechanistically, Notch receptors activated by HTNV enhance NF-κB signaling by recruiting IKKβ and p65, promoting inflammatory macrophage polarization in both species. However, in mice rather than humans, Notch-mediated inflammation is timely restrained by a series of murine-specific long noncoding RNAs transcribed by the Notch pathway in a negative feedback manner. Among them, the lnc-ip65 detaches p65 from the Notch receptor and inhibits p65 phosphorylation, rewiring macrophages from the pro-inflammation to the pro-resolution phenotype. Genetic ablation of lnc-ip65 leads to destructive HTNV infection in mice. Thus, our findings reveal an immune-braking function of murine noncoding RNAs, offering a special therapeutic strategy for HTNV infection.

Hantavirus Pulmonary Syndrome Caused by Puumala Orthohantavirus-A Case Report and Literature Review

In this article, we report on a rare case of acute respiratory distress syndrome (ARDS) caused by the Puumala orthohantavirus (PUUV), which is typically associated with hemorrhagic fever with renal syndrome (HFRS). This is the first documented case of PUUV-associated ARDS in Southeast Europe. The diagnosis was confirmed by serum RT-PCR and serology and corroborated by phylogenetic analysis and chemokine profiling. The patient was a 23-year-old male from Zagreb, Croatia, who had recently traveled throughout Europe. He presented with fever, headache, abdominal pain, and sudden onset of ARDS. Treatment involved high-flow nasal cannula oxygen therapy and glucocorticoids, which resulted in a full recovery. A systematic literature review identified 10 cases of hantavirus pulmonary syndrome (HPS) caused by PUUV in various European countries and Turkey between 2002 and 2023. The median age of patients was 53 years (range 24-73), and six of the patients were male. Most patients were treated in intensive care units, but none received antiviral therapy targeting PUUV. Eight patients survived hospitalization. The presented case highlights the importance of considering HPS in the differential diagnosis of ARDS, even in areas where HFRS is the dominant form of hantavirus infection.

Hantavirus Infection in Children-A Pilot Study of Single Regional Center

BACKGROUND

Hantaviruses are infectious etiological agents of a group of rodent-borne hemorrhagic fevers, with two types of clinical manifestations in humans: hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). According to available statistics, the disease occurs mainly in adults, but the lower incidence in the pediatric population might also be related to a lack of diagnosis possibilities or even unsatisfactory knowledge about the disease.

MATERIALS AND METHODS

The purpose of this study was to evaluate the cases of hemorrhagic fever with renal syndrome diagnosed and treated in the Department of Nephrology at St. Mary's Emergency Hospital for Children in Iasi, Romania, representative of the North-East of Romania. We also reviewed the specialized literature on the topic.

RESULTS

Between January 2017 and January 2022, eight cases of HFRS, all men, and seven from rural areas, aged 11-18 years old, were referred to our clinic because of an acute kidney injury (AKI). Seven cases were identified as Dobrava serotype while one case was determined by Haantan serotype.

CONCLUSIONS

HFRS should always be considered as a differential diagnosis when faced with a patient with AKI and thrombocytopenia. Dobrava serotype is the most common hantavirus subtype in the Balkans. For the specific prevention of human infections, mainly in high-risk groups, vaccines are needed. As far as we know, this is the first study on HFRS in Romanian children.

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.

Expert Consensus on the Prevention and Treatment of Hemorrhagic Fever with Renal Syndrome

Abstract

Hemorrhagic fever with renal syndrome (HFRS) is an acute zoonosis with a global distribution. China is one of the countries with a high incidence of HFRS, which has long endangered the lives and health of the Chinese people. The Infectious Disease Branch of the Chinese Preventive Medicine Association and the Infectious Diseases Branch of the Chinese Medical Association organized national multidisciplinary experts, based on domestic and international research results combined with experts’ practical experiences, to reach this consensus after thorough discussion. This consensus contains 17 recommendations aimed at prevention and identification of important clinical issues to further standardize the prevention, diagnosis, and treatment of HFRS.

Serum Markers Associated with Disease Severity in a Bosnian Hemorrhagic Fever with Renal Syndrome Cohort

Puumala orthohantavirus (PUUV) is endemic in Europe and can cause hemorrhagic fever with renal syndrome (nephropathia epidemica). Disease features include fever, thrombocytopenia, and acute kidney injury (AKI). This retrospective cohort study of forty PUUV patients aims to characterize associations of serum immunological, hemostatic or kidney injury markers to disease severity. While interleukin-18 (IL-18) was significantly increased in severely thrombocytopenic patients (<100 × 109 platelets/L) compared to patients with higher platelet counts, RANTES was significantly decreased in these patients. These data suggest that patients with significant thrombocytopenia might have experienced pronounced Th1 immune responses. When kidney dysfunction was used as the primary disease outcome, recently identified AKI biomarkers (Cystatin C, insulin-like growth factor-binding protein 7, Nephrin, and trefoil factor 3) were significantly upregulated in patients with severe PUUV infection, defined as the estimated glomerular filtration rate (eGFR) below 30 m/min/1.73 m2. The increased expression of these markers specifically indicates pathology in glomeruli and proximal tubuli. Furthermore, E-selectin was significantly higher while interferon gamma-induced protein 10 (IP-10) was significantly lower in PUUV patients with more severe kidney dysfunction compared to patients with higher eGFR-values. Increased E-selectin illustrates the central role of endothelial cell activation, whereas decreased IP-10 could indicate a less important role of this cytokine in the pathogenesis of kidney dysfunction.

Clinical and Immunological Predictors of Hemorrhagic Fever with Renal Syndrome Outcome during the Early Phase

The ability to accurately predict the early progression of hemorrhagic fever with renal syndrome (HFRS) is crucial for reducing morbidity and mortality rates in severely affected patients. However, the utility of biomarkers for predicting clinical outcomes remains elusive in HFRS. The aims of the current study were to analyze the serum levels of immune function-related proteins and identify novel biomarkers that may help ascertain clinical outcomes of HFRS. Enzyme-linked immunosorbent assay, Luminex, and bioanalyzer assays were used to quantitatively detect 15 biomarkers in 49 serum samples of 26 patients with HFRS. High hemoglobin (HGB) and low urine output (UO) levels were identified as potential biomarkers associated with the acute HFRS. The serum soluble urokinase plasminogen activator receptor (suPAR) and C-X-C motif chemokine ligand 10 (CXCL10) values increased in the early phase of diseases. Elevated suPAR, interleukin-10 (IL-10), CXCL10, and decreased transforming growth factor-beta 3 (TGF-β3) were representative predictors of the disease severity. Upregulation of the HGB showed a significant correlation with high levels of suPAR and CXCL10. Reduced UO positively correlated with increased suPAR, CXCL10, and TGF-β2, and decreased vascular endothelial growth factor and TGF-β3. The changing HGB and UO criteria, high suPAR, IL-10, CXCL10, and low TGF-β3 of HFRS raise significant awareness for physicians regarding prospective biomarkers for monitoring early warning signs of HFRS. This study provides critical insights into the clinical and immunological biomarkers for disease severity and progression in patients with HFRS to identify early predictions of fatal outcomes.

Serum Cytokine Alterations Associated with Age of Patients with Nephropathia Epidemica

Nephropathia epidemica (NE) is a zoonotic disease caused by hantaviruses transmitted from rodents, endemic in the Republic of Tatarstan, Russia. The disease presents clinically with mild, moderate, and severe forms, and time-dependent febrile, oliguric, and polyuric stages of the disease are also recognized. The patient's cytokine responses have been suggested to play a central role in disease pathogenesis; however, little is known about the different patterns of cytokine expression in NE in cohorts of different ages and sexes. Serum samples and clinical records were collected from 139 patients and 57 controls (healthy donors) and were used to analyze 48 analytes with the Bio-Plex multiplex magnetic bead-based antibody detection kits. Principal component analysis of 137 patient and 55 controls (for which there was full data) identified two components that individually accounted for >15% of the total variance in results and together for 38% of the total variance. PC1 represented a proinflammatory TH17/TH2 cell antiviral cytokine profile and PC2 a more antiviral cytokine profile with patients tending to display one or the other of these. Severity of disease and stage of illness did not show any correlation with PC1 profiles; however, significant differences were seen in patients with high PC1 profiles vs. lower for a number of individual clinical parameters: High PC1 patients showed a reduced number of febrile days, but higher maximum urine output, higher creatinine levels, and lower platelet levels. Overall, the results of this study point towards a stronger proinflammatory profile occurring in younger NE patients, this being associated with markers of acute kidney injury and low levels of high-density cholesterol. This is consistent with previous work indicating that the pathology of NE is immune driven, with an inflammatory immune response being associated with disease and that this immune response is more extreme in younger patients.

OUP accepted manuscript

Hantavirus-induced diseases are emerging zoonoses with endemic appearances and frequent outbreaks in different parts of the world. In humans, hantaviral pathology is characterized by the disruption of the endothelial cell barrier followed by increased capillary permeability, thrombocytopenia due to platelet activation/depletion and an overactive immune response. Genetic vulnerability due to certain human leukocyte antigen haplotypes is associated with disease severity. Typically, two different hantavirus-caused clinical syndromes have been reported: hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The primarily affected vascular beds differ in these two entities: renal medullary capillaries in HFRS caused by Old World hantaviruses and pulmonary capillaries in HCPS caused by New World hantaviruses. Disease severity in HFRS ranges from mild, e.g. Puumala virus-associated nephropathia epidemica, to moderate, e.g. Hantaan or Dobrava virus infections. HCPS leads to a severe acute respiratory distress syndrome with high mortality rates. Due to novel insights into organ tropism, hantavirus-associated pathophysiology and overlapping clinical features, HFRS and HCPS are believed to be interconnected syndromes frequently involving the kidneys. As there are no specific antiviral treatments or vaccines approved in Europe or the USA, only preventive measures and public awareness may minimize the risk of hantavirus infection. Treatment remains primarily supportive and, depending on disease severity, more invasive measures (e.g., renal replacement therapy, mechanical ventilation and extracorporeal membrane oxygenation) are needed.

Serum Cytokine Profiles of Rapid Recovery Patients with COVID-19: Series of 6 Cases

COVID-19 patients reveal various clinical manifestations; however, the specific mechanisms and factors contributing to rapid recovery remain unclear. We performed serum cytokine profiling using a bead-based immunoassay in six COVID-19 patients with mild symptoms who experienced rapid recovery. All patients had fever that resolved within 4 days. During the study, the interferon gamma-related protein 10 (IP-10) level rapidly increased initially, and then rapidly decreased in all six patients. Similarly, the interferon (IFN)-λ 2/3 levels rapidly increased initially, and then decreased in five of the six patients. IP-10 and IFN-λ2/3 may play a key role in the rapid recovery of mild COVID-19.

Elevated Plasma Fractalkine Level Is Associated with the Severity of Hemorrhagic Fever with Renal Syndrome in Humans

Hantaan virus infection may cause severe lethal hemorrhagic fever with renal syndrome (HFRS) in humans. The chemokine fractalkine (CX3CL1) acts as a proinflammatory cytokine, and it is elevated in several infectious diseases. However, little is known about the contributions of CX3CL1 to HFRS pathogenesis. Present study detected plasma CX3CL1 levels and expression of the receptor CX3CR1 in HFRS patients and discussed the possible effects of CX3CL1 on pathogenesis of HFRS. Plasma CX3CL1 in acute phase and Critical/Severe groups of HFRS patients were significantly increased compared to that in normal controls (p < 0.001 and p < 0.01, respectively). High plasma CX3CL1 was negatively correlated with platelet count (r = -0.5844, p < 0.0001) and positively correlated with blood urea nitrogen (r = 0.3668, p = 0.0039), creatinine (r = 0.42, p = 0.0008), and white blood cells (r = 0.2646, p = 0.0411). Expression of CX3CR1 on nonclassical and intermediate monocytes was also increased in the acute phase (p < 0.01 for both the cells) and Critical/Severe groups (p < 0.05 and p < 0.01, respectively) of HFRS patients compared to that in normal controls. Taken together, elevation of plasma CX3CL1 in HFRS patients and expression of CX3CR1 on nonclassical and intermediate monocyte subsets might provide new insights into the potential role of CX3CL1/CX3CR1 in pathogenesis of HFRS.

Immunopathogenesis of Different Emerging Viral Infections: Evasion, Fatal Mechanism, and Prevention

Different emerging viral infections may emerge in different regions of the world and pose a global pandemic threat with high fatality. Clarification of the immunopathogenesis of different emerging viral infections can provide a plan for the crisis management and prevention of emerging infections. This perspective article describes how an emerging viral infection evolves from microbial mutation, zoonotic and/or vector-borne transmission that progresses to a fatal infection due to overt viremia, tissue-specific cytotropic damage or/and immunopathology. We classified immunopathogenesis of common emerging viral infections into 4 categories: 1) deficient immunity with disseminated viremia (e.g., Ebola); 2) pneumocytotropism with/without later hyperinflammation (e.g., COVID-19); 3) augmented immunopathology (e.g., Hanta); and 4) antibody-dependent enhancement of infection with altered immunity (e.g., Dengue). A practical guide to early blocking of viral evasion, limiting viral load and identifying the fatal mechanism of an emerging viral infection is provided to prevent and reduce the transmission, and to do rapid diagnoses followed by the early treatment of virus neutralization for reduction of morbidity and mortality of an emerging viral infection such as COVID-19.

Immune response during hantavirus diseases: implications for immunotherapies and vaccine design

Orthohantaviruses, previously named hantaviruses, cause two emerging zoonotic diseases: haemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Overall, over 200 000 cases are registered every year worldwide, with a fatality rate ranging between 0·1% and 15% for HFRS and between 20% and 40% for HCPS. No specific treatment or vaccines have been approved by the U.S. Food and Drug Administration (FDA) to treat or prevent hantavirus-caused syndromes. Currently, little is known about the mechanisms at the basis of hantavirus-induced disease. However, it has been hypothesized that an excessive inflammatory response plays an essential role in the course of the disease. Furthermore, the contributions of the cellular immune response to either viral clearance or pathology have not been fully elucidated. This article discusses recent findings relative to the immune responses elicited to hantaviruses in subjects suffering HFRS or HCPS, highlighting the similarities and differences between these two clinical diseases. Also, we summarize the most recent data about the cellular immune response that could be important for designing new vaccines to prevent this global public health problem.

Rapid humoral immune responses are required for recovery from haemorrhagic fever with renal syndrome patients

Haemorrhagic fever with renal syndrome (HFRS) following Hantaan virus (HTNV) infection displays variable clinical signs. Humoral responses elicited during HTNV infections are considered important, however, this process remains poorly understood. Herein, we have investigated the phenotype, temporal dynamics, and characteristics of B-cell receptor (BCR) repertoire in an HFRS cohort. The serological profiles were characterized by a lowered expression level of nucleoprotein (NP)-specific antibody in severe cases. Importantly, B-cell subsets were activated and proliferated within the first two weeks of symptom onset and moderate cases reacted more rapidly. BCR analysis in the recovery phase revealed a dramatic increase in the immunoglobulin gene diversity which was more significantly progressed in moderate infections. In severe cases, B-cell-related transcription was lower with inflammatory sets overactivated. Taken together, these data suggest the clinical signs and disease recovery in HFRS patients were positively impacted by rapid and efficacious humoral responses.

Cytokine, Chemokine, and Metalloprotease Activation in the Serum of Patients with Nephropathia Epidemica from the Republic of Tatarstan and the Republic of Mordovia, Russia

Nephropathia Epidemica (NE), endemic to several Volga regions of Russia, including the Republic of Tatarstan (RT) and the Republic of Mordovia (RM), is a mild form of hemorrhagic fever with renal syndrome caused by infection with rodent-borne orthohantaviruses. Although NE cases have been reported for decades, little is known about the hantavirus strains associated with human infection in these regions. There is also limited understanding of the pathogenesis of NE in the RT and the RM. To address these knowledge gaps, we conducted comparative analyses of patients with NE in the RT and the RM. Clinical symptoms were more severe in patients with NE from the RM with longer observed duration of fever symptoms and hospitalization. Analysis of patient sera showed changes in the levels of numerous cytokines, chemokines, and matrix metalloproteases (MMPs) in patients with NE from both the RT and the RM, suggesting leukocyte activation, extracellular matrix degradation, and leukocyte chemotaxis. Interestingly, levels of several cytokines were distinctly different between patients NE from the RT when compared with those from the RM. These differences were not related to the genetic variation of orthohantaviruses circulating in those regions, as sequence analysis showed that Puumala virus (PUUV) was the causative agent of NE in these regions. Additionally, only the “Russia” (RUS) genetic lineage of PUUV was detected in the serum samples of patients with NE from both the RT and the RM. We therefore conclude that differences in serum cytokine, chemokine, and MMP levels between the RT and the RM are related to environmental factors and lifestyle differences that influence individual immune responses to orthohantavirus infection.

Cytokine Profiles and Antibody Response Associated to Choclo Orthohantavirus Infection

Background

New World Hantaviruses (NWHs) are the etiological agent underlying hantavirus cardiopulmonary syndrome (HCPS), a severe respiratory disease with high mortality rates in humans. In Panama, infections with Choclo Orthohantavirus (CHOV) cause a much milder illness characterized by higher seroprevalence and lower mortality rates. To date, the cytokine profiles and antibody responses associated with this milder form of HCPS have not been defined. Therefore, in this study, we examined immune serological profiles associated with CHOV infections.

Methods

For this retrospective study, sera from fifteen individuals with acute CHOV-induced HCPS, were analyzed alongside sera from fifteen convalescent phase individuals and thirty-three asymptomatic, CHOV-seropositive individuals. Cytokine profiles were analyzed by multiplex immunoassay. Antibody subclasses, binding, and neutralization against CHOV-glycoprotein (CHOV-GP) were evaluated by ELISA, and flow cytometry.

Results

High titers of IFNγ, IL-4, IL-8, and IL-10 serum cytokines were found in the acute individuals. Elevated IL-4 serum levels were found in convalescent and asymptomatic seropositive individuals. High titers of IgG1 subclass were observed across the three cohorts analyzed. Neutralizing antibody response against CHOV-GP was detectable in few acute individuals but was strong in both convalescent and asymptomatic seropositive individuals.

Conclusion

A Th1/Th2 cytokine signature is characteristic during acute mild HCPS caused by CHOV infection. High expression of Th2 and IL-8 cytokines are correlated with clinical parameters in acute mild HCPS. In addition, a strong IL-4 signature is associated with different cohorts, including asymptomatic individuals. Furthermore, asymptomatic individuals presented high titers of neutralizing antibodies.

Monocyte subset redistribution from blood to kidneys in patients with Puumala virus caused hemorrhagic fever with renal syndrome

Innate immune cells like monocytes patrol the vasculature and mucosal surfaces, recognize pathogens, rapidly redistribute to affected tissues and cause inflammation by secretion of cytokines. We previously showed that monocytes are reduced in blood but accumulate in the airways of patients with Puumala virus (PUUV) caused hemorrhagic fever with renal syndrome (HFRS). However, the dynamics of monocyte infiltration to the kidneys during HFRS, and its impact on disease severity are currently unknown. Here, we examined longitudinal peripheral blood samples and renal biopsies from HFRS patients and performed in vitro experiments to investigate the fate of monocytes during HFRS. During the early stages of HFRS, circulating CD14-CD16+ nonclassical monocytes (NCMs) that patrol the vasculature were reduced in most patients. Instead, CD14+CD16- classical (CMs) and CD14+CD16+ intermediate monocytes (IMs) were increased in blood, in particular in HFRS patients with more severe disease. Blood monocytes from patients with acute HFRS expressed higher levels of HLA-DR, the endothelial adhesion marker CD62L and the chemokine receptors CCR7 and CCR2, as compared to convalescence, suggesting monocyte activation and migration to peripheral tissues during acute HFRS. Supporting this hypothesis, increased numbers of HLA-DR+, CD14+, CD16+ and CD68+ cells were observed in the renal tissues of acute HFRS patients compared to controls. In vitro, blood CD16+ monocytes upregulated CD62L after direct exposure to PUUV whereas CD16- monocytes upregulated CCR7 after contact with PUUV-infected endothelial cells, suggesting differential mechanisms of activation and response between monocyte subsets. Together, our findings suggest that NCMs are reduced in blood, potentially via CD62L-mediated attachment to endothelial cells and monocytes are recruited to the kidneys during HFRS. Monocyte mobilization, activation and functional impairment together may influence the severity of disease in acute PUUV-HFRS.

Unique Cytokine Response in West Nile Virus Patients Who Developed Chronic Kidney Disease: A Prospective Cohort Study

West Nile virus (WNV) is a widespread and devastating disease, especially in those who develop neuroinvasive disease. A growing body of evidence describes sequelae years after infection, including neurological complications and chronic kidney disease (CKD). Eighty-nine out of 373 WNV-positive cases were followed for approximately two years and compared to 127 WNV-negative controls with and without CKD. Adjusted risk ratios (aRRs) were calculated via a log binomial regression to determine the impact of WNV exposure and other possible confounders on the likelihood of developing CKD. Cytokine profiles of WNV patients and controls were evaluated to characterize differences and describe potential underlying pathophysiological mechanisms. The associated risk for developing CKD was significantly associated with history of WNV infection (aRR = 1.91, 95% CI 1.13–3.25). Additionally, five distinct cytokines were found to be significantly associated with WNV infection (eotaxin, IL-8, IL-12p70, IP-10, and TNFα) after the p-value was adjusted to <0.0019 due to the Bonferroni correction. These data support that WNV infection is an independent risk factor for CKD, even after accounting for confounding comorbidities. WNV participants who developed CKD had high activity of proinflammatory markers, indicating underlying inflammatory disease. This study provides new insights into CKD resultant of WNV infection.

SARS-CoV-2: Immune Response Elicited by Infection and Development of Vaccines and Treatments

The World Health Organization (WHO) announced in March a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This new infectious disease was named Coronavirus Disease 19 (COVID-19), and at October 2020, more than 39,000,000 cases of SARS-CoV-2 have been detected worldwide leading to near 1,100,000 deaths. Clinically, COVID-19 is characterized by clinical manifestations, such as fever, dry cough, headache, and in more severe cases, respiratory distress. Moreover, neurological-, cardiac-, and renal-related symptoms have also been described. Clinical evidence suggests that migration of immune cells to the affected organs can produce an exacerbated release of proinflammatory mediators that contribute to disease and render the immune response as a major player during the development of the COVID-19 disease. Due to the current sanitary situation, the development of vaccines is imperative. Up to the date, 42 prototypes are being tested in humans in different clinical stages, with 10 vaccine candidates undergoing evaluation in phase III clinical trials. In the same way, the search for an effective treatment to approach the most severe cases is also in constant advancement. Several potential therapies have been tested since COVID-19 was described, including antivirals, antiparasitic and immune modulators. Recently, clinical trials with hydroxychloroquine-a promising drug in the beginning-were suspended. In addition, the Food and Drug Administration (FDA) approved convalescent serum administration as a treatment for SARS-CoV-2 patients. Moreover, monoclonal antibody therapy is also under development to neutralize the virus and prevent infection. In this article, we describe the clinical manifestations and the immunological information available about COVID-19 disease. Furthermore, we discuss current therapies under study and the development of vaccines to prevent this disease.

Differential CD4 T Regulatory Cell Phenotype Induced by Andes Hantavirus Glycoprotein

Hantavirus cardiopulmonary syndrome (HCPS) caused by Andes orthohantavirus (ANDV) in South America is a public health threat due to the significant rate of mortality and the lack of a specific treatment. Interestingly, the virus does not produce cytopathic effect, thereby the strong antiviral immune response is suspected to contribute to pathogenesis, hence is important to understand the balance between protective and harmfully immunity. CD4⁺ T regulatory cells (Treg) are essential to control an exacerbated immune response. In human ANDV infection, little is known about CD4⁺ Treg cells, which may be involved in control immunopathology associated to the infection. In this report, we characterize the phenotype of memory CD4⁺ Tregs in a HCPS survivor's cohort. Based on the expression of CXCR3, CCR4, and CCR6, we identified different Th-like Treg populations in ANDV survival's PBMCs. In addition, the effect of ANDV-glycoprotein virus like particles (VLP) was determined. We demonstrated that memory CD4⁺ Treg from HCPS present a specific phenotype, showing higher frequency of PD-1 compared to healthy donors (HD). In addition, it was observed a decrease in the frequency of Th1-like memory CD4⁺ Treg in HCPS, important to highlight that this signature could be preserved even years after resolution of infection. Moreover, to gain insight in the mechanism involved, we evaluated whether ANDV-glycoprotein (GP) VLP could modulate CD4⁺ Treg. Interestingly, ANDV-GP VLP induced a decrease in the frequency of CXCR3 (Th1-like) and an increase in CCR4 (Th2-like) memory CD4⁺ Treg in both HD and HCPS PBMCs, indicating that ANDV-GP could specifically act over CXCR3 and CCR4 in CD4⁺ Treg. This report contributes to the study of human CD4⁺ Treg cells in ANDV infection.

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.

Elevated plasma interleukin 34 levels correlate with disease severity-reflecting parameters of patients with haemorrhagic fever with renal syndrome

Background: Haemorrhagic fever with renal syndrome (HFRS) is characterized by an uncontrolled cytokine storm that causes vascular leakage and kidney injury. The cytokine interleukin 34 (IL-34) enhances proliferation and differentiation of myeloid cells and secretion of pro-inflammatory cytokines, which is involved in the pathogenesis of some inflammatory and infectious diseases, including acute kidney injury. To date, however, the role of IL-34 in patients with HFRS is unclear. This study aims to determine the plasma IL-34 levels of HFRS patients and discuss the possible effects of IL-34 in the pathogenesis of HFRS. Methods: Plasma levels of IL-34 in 52 HFRS patients and 20 healthy controls were quantified using enzyme-linked immunosorbent assay. Results: Compared with healthy controls, the plasma IL-34 levels in HFRS patients were significantly elevated in acute phase [37.92 (0-215.45) pg/ml vs. 7.13 (0-19.44) pg/ml, p < .0001], and then decreased to the normal levels in convalescent phase. Importantly, IL-34 levels correlated positively with white blood cell counts and mononuclear cell counts (r = 0.592, p < .0001 and r = 0.458, p < .0001, respectively), and correlated negatively with platelet counts and serum albumin levels (r = -0.430, p < .0001 and r = -0.479, p = .0001, respectively). Conclusions: Plasma levels of IL-34 in HFRS patients were significantly elevated in acute phase and correlated with disease severity-reflecting parameters, which suggests a potential role of IL-34 in HFRS and should be future explored.

Δccr5 Genotype Is Associated with Mild Form of Nephropathia Epidemica

Nephropathia Epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS) and linked to hantavirus infection, is endemic in the Republic of Tatarstan. Several genetic markers of HFRS severity have been identified previously, including human leukocyte antigen (HLA) complexes and nucleotide polymorphism in the tumor necrosis factor alpha (TNFα) gene. Still, our understanding of the genetic markers of NE severity remains incomplete. The frequency of the C-C chemokine receptor type 5 (CCR5) gene wild type and gene with 32-base-pair deletion (Δ32CCR5) genotypes in 98 NE samples and 592 controls was analyzed using PCR. Along with the serum levels of 94 analytes, a lack of differences in the CCR5 genotype distribution between NE cases and the general population suggests that the CCR5 genotype does not affect susceptibility to hantavirus infection. However, in NE cases, significant variation in the serum levels of the host matrix metalloproteases between functional CCR5 homozygous and Δ32CCR5 heterozygous patients was detected. Also, the oliguric phase was longer, while thrombocyte counts were lower in functional CCR5 homozygous as compared to heterozygous NE cases. Our data, for the first time, presents the potential role of the CCR5 receptor genotype in NE pathogenesis. Our data suggests that NE pathogenesis in functional CCR5 homozygous and heterozygous NE patients differs, where homozygous cases may have more disintegration of the extracellular matrix and potentially more severe disease.

Cytokine Storm Combined with Humoral Immune Response Defect in Fatal Hemorrhagic Fever with Renal Syndrome Case, Tatarstan, Russia

Hemorrhagic fever with renal syndrome (HFRS) is endemic in Tatarstan, where thousands of cases are registered annually. Puumalaorthohantavirus is commonly detected in human case samples as well as in captured bank voles, the rodent hosts. The pathogenesis of HFRS is still not well described, although the cytokine storm hypothesis is largely accepted. In this study, we present a comprehensive analysis of a fatal HFRS case compared with twenty four non-fatal cases where activation of the humoral and cellular immune responses, pro-inflammatory cytokines and disturbed blood coagulation were detected using immunological, histological, genetic and clinical approaches. Multiple organ failure combined with disseminated intravascular coagulation syndrome and acute renal failure was the cause of death. Decreased Interleukin (IL)-7 and increased IL-18, chemokine (C-C motif) ligand (CCL)-5, stem cell growth factor (SCGF)-b and tumor necrosis factor-beta (TNF-β) serum levels were found, supporting the cytokine storm hypothesis of hantavirus pathogenesis.

Innate and adaptive immune responses against human Puumala virus infection: immunopathogenesis and suggestions for novel treatment strategies for severe hantavirus-associated syndromes

Two related hyperinflammatory syndromes are distinguished following infection of humans with hantaviruses: haemorrhagic fever with renal syndrome (HFRS) seen in Eurasia and hantavirus pulmonary syndrome (HPS) seen in the Americas. Fatality rates are high, up to 10% for HFRS and around 35%-40% for HPS. Puumala virus (PUUV) is the most common HFRS-causing hantavirus in Europe. Here, we describe recent insights into the generation of innate and adaptive cell-mediated immune responses following clinical infection with PUUV. First described are studies demonstrating a marked redistribution of peripheral blood mononuclear phagocytes (MNP) to the airways, a process that may underlie local immune activation at the site of primary infection. We then describe observations of an excessive natural killer (NK) cell activation and the persistence of highly elevated numbers of NK cells in peripheral blood following PUUV infection. A similar vigorous CD8 Tcell response is also described, though Tcell responses decline with viraemia. Like MNPs, many NK cells and CD8 T cells also localize to the lung upon acute PUUV infection. Following this, findings demonstrating the ability of hantaviruses, including PUUV, to cause apoptosis resistance in infected target cells, are described. These observations, and associated inflammatory cytokine responses, may provide new insights into HFRS and HPS disease pathogenesis. Based on similarities between inflammatory responses in severe hantavirus infections and other hyperinflammatory disease syndromes, we speculate whether some therapeutic interventions that have been successful in the latter conditions may also be applicable in severe hantavirus infections.

T-Cell Response to Viral Hemorrhagic Fevers

Viral hemorrhagic fevers (VHF) are a group of clinically similar diseases that can be caused by enveloped RNA viruses primarily from the families Arenaviridae, Filoviridae, Hantaviridae, and Flaviviridae. Clinically, this group of diseases has in common fever, fatigue, dizziness, muscle aches, and other associated symptoms that can progress to vascular leakage, bleeding and multi-organ failure. Most of these viruses are zoonotic causing asymptomatic infections in the primary host, but in human beings, the infection can be lethal. Clinical and experimental evidence suggest that the T-cell response is needed for protection against VHF, but can also cause damage to the host, and play an important role in disease pathogenesis. Here, we present a review of the T-cell immune responses to VHF and insights into the possible ways to improve counter-measures for these viral agents.

Motility of human renal cells is disturbed by infection with pathogenic hantaviruses

Background

Hemorrhagic fever with renal syndrome (HFRS) caused by pathogenic hantaviruses in Europe and Asia is often characterized by acute kidney injury (AKI) with massive proteinuria. Renal filtration depends on the integrity of epithelial and endothelial monolayers in the tubular and glomerular apparatus. Tubular and glomerular cells represent target cells of hantavirus infection. However, the detailed mechanisms of renal impairment induced by hantaviruses are not well understood.

Methods

We analyzed the cellular consequences of hantavirus infection by measuring adhesion and migration capacity of human renal cells infected with Puumala (PUUV) or Hantaan (HTNV) virus. The impact of hantaviral nucleocapsid proteins (N proteins) on motility was examined by transfection of podocytes.

Results

Infection of kidney cells with hantavirus species PUUV and HTNV causes a significant reduction of migration capacity. The impaired motility depends on viral replication and transfection of podocytes with N protein of PUUV or HTNV reveals that the expression of N protein alone is sufficient to deteriorate podocyte function. The cellular effects are more pronounced for the more pathogenic HTNV than for PUUV that causes a milder form of HFRS.

Conclusions

The direct impairment of migration capacity of renal cells by hantaviral N proteins may contribute substantially to proteinuria observed in the clinical picture of hantavirus infection.

Preliminary insights into the genetics of bank vole tolerance to Puumala hantavirus in Sweden

Natural reservoirs of zoonotic pathogens generally seem to be capable of tolerating infections. Tolerance and its underlying mechanisms remain difficult to assess using experiments or wildlife surveys. High-throughput sequencing technologies give the opportunity to investigate the genetic bases of tolerance, and the variability of its mechanisms in natural populations. In particular, population genomics may provide preliminary insights into the genes shaping tolerance and potentially influencing epidemiological dynamics. Here, we addressed these questions in the bank vole Myodes glareolus, the specific asymptomatic reservoir host of Puumala hantavirus (PUUV), which causes nephropathia epidemica (NE) in humans. Despite the continuous spatial distribution of M. glareolus in Sweden, NE is endemic to the northern part of the country. Northern bank vole populations in Sweden might exhibit tolerance strategies as a result of coadaptation with PUUV. This may favor the circulation and maintenance of PUUV and lead to high spatial risk of NE in northern Sweden. We performed a genome-scan study to detect signatures of selection potentially correlated with spatial variations in tolerance to PUUV. We analyzed six bank vole populations from Sweden, sampled from northern NE-endemic to southern NE-free areas. We combined candidate gene analyses (Tlr4, Tlr7, and Mx2 genes) and high-throughput sequencing of restriction site-associated DNA (RAD) markers. Outlier loci showed high levels of genetic differentiation and significant associations with environmental data including variations in the regional number of NE human cases. Among the 108 outliers that matched to mouse protein-coding genes, 14 corresponded to immune-related genes. The main biological pathways found to be significantly enriched corresponded to immune processes and responses to hantavirus, including the regulation of cytokine productions, TLR cascades, and IL-7, VEGF, and JAK-STAT signaling. In the future, genome-scan replicates and functional experimentations should enable to assess the role of these biological pathways in M. glareolus tolerance to PUUV.

Upregulation of P2Y2R, Active uPA, and PAI-1 Are Essential Components of Hantavirus Cardiopulmonary Syndrome

Sin Nombre virus (SNV) causes hantavirus cardiopulmonary pulmonary syndrome (HCPS) with the loss of pulmonary vascular endothelial integrity, and pulmonary edema without causing cytopathic effects on the vascular endothelium. HCPS is associated primarily with a dysregulated immune response. We previously found occult signs of hemostatic imbalance in the form of a sharp >30-100 fold increase in the expression of plasminogen activator inhibitor type 1 (PAI-1), in serial blood plasma draws of terminal stage-patients. However, the mechanism of the increase in PAI-1 remains unclear. PAI-1 is a primary inhibitor of fibrinolysis caused by tissue plasminogen activator (tPA) and urokinase plasminogen activator plasma (uPA). Here, we investigate factors that contribute to PAI-1 upregulation during HCPS. Using zymography, we found evidence of PAI-1-refractory uPA activity and no tPA activity in plasma samples drawn from HCPS patients. The sole prevalence of uPA activity suggested that severe inflammation drove PAI-1 activity. We have recently reported that the P2Y₂ receptor (P2Y₂R) mediates SNV infectivity by interacting in cis with β₃ integrins, which activates the latter during infection. P2Y₂R is a known effector for several biological processes relevant to HCPS pathogenesis, such as upregulation of tissue factor (TF), a primary initiator of the coagulation cascade, stimulating vascular permeability and leukocyte homing to sites of infection. As P2Y₂R is prone to upregulation under conditions of inflammation, we compared the expression level of P2Y₂R in formalin fixed tissues of HCPS decedents using a TaqMan assay and immunohistochemistry. Our TaqMan results show that the expression of P2Y₂R is upregulated significantly in HCPS cases compared to non- HCPS controls (P < 0.001). Immunohistochemistry showed that lung macrophages were the primary reservoir of high and coincident localization of P2Y₂R, uPA, PAI-1, and TF antigens. We also observed increased staining for SNV antigens in the same tissue segments where P2Y₂R expression was upregulated. Conversely, sections of low P2Y₂R expression showed weak manifestations of macrophages, SNV, PAI-1, and TF. Coincident localization of P2Y₂R and PAI-1 on macrophage deposits suggests an inflammation-dependent mechanism of increasing pro-coagulant activity in HCPS in the absence of tissue injury.