Hantavirus interferon regulation and virulence determinants

Scientometric analysis of research trends in hemorrhagic fever with renal syndrome: A historical review and network visualization

BACKGROUND

Hemorrhagic fever with renal syndrome (HFRS) research has undergone significant global transformation over the past decades. A comprehensive scientometric overview of research trends and scholarly cooperation in HFRS is absent. This study employs scientometric analysis to map the evolution of research themes, identify widely and scarcely explored areas, and anticipate future research directions.

METHODS

We searched Web of Science Core Collection from inception until July 31, 2023, identifying 3908 HFRS-related studies published for analysis. Utilizing CiteSpace, VOSviewer, and Bibliometrix, we performed co-authorship, co-occurrence, and co-citation analyses, and visualized research networks.

RESULTS

Our analysis revealed a consistent upward trend in HFRS publications since 1980, with an average growth rate of 11.34 %. The United States led in publication and citation counts, followed by China, Finland, Germany, and Sweden. Through co-occurrence analysis, we categorized keywords into eight clusters and 24 sub-clusters, revealing six predominant research themes: Clinical Features, Epidemiology, Mechanisms, Virus, Evolution, and Host. Notably, while themes such as Virus and Pathogenesis have been extensively studied, others, including certain aspects of Host research and Environmental Factors, remain less explored.

CONCLUSION

This scientometric synthesis provides a global perspective on the breadth and depth of HFRS research, highlighting well-trodden and understudied areas. It offers a roadmap for researchers to navigate the evolving landscape of HFRS studies and prioritize areas ripe for future investigation.

MicroRNA let-7a regulation of Hantaan virus replication by Targeting FAS Signaling Pathways

Hantaan virus (HTNV) infection in humans can cause hemorrhagic fever and renal syndrome (HFRS). Understanding host responses to HTNV infection is crucial for developing effective disease intervention strategies. Previous RNA-sequencing studies have investigated the role of microRNAs (miRNAs) in the post-transcriptional regulation of host genes in response to HTNV infection. In this study, we demonstrated that HTNV infection induces let-7a expression in human umbilical vein endothelial cells (HUVEC) and that HTNV G protein upregulates the expression of let-7a. miRNA let-7a mimics and inhibitors validated the predicted targets, including cell apoptosis genes (FAS, caspase-8, and caspase-3) and inflammatory factors (IL-6 and its related factors). Modulation of miRNA let-7a levels by miRNA mimics and inhibitors affected HTNV replication, indicating that HTNV modulates host miRNA expression to affect the outcome of the antiviral host response.

Hantaan virus inhibits type I interferon response by targeting RLR signaling pathways through TRIM25

Hantaan virus (HTNV) is responsible for hemorrhagic fever with renal syndrome (HFRS), primarily due to its ability to inhibit host innate immune responses, such as type I interferon (IFN-I). In this study, we conducted a transcriptome analysis to identify host factors regulated by HTNV nucleocapsid protein (NP) and glycoprotein. Our findings demonstrate that NP and Gc proteins inhibit host IFN-I production by manipulating the retinoic acid-induced gene I (RIG-I)-like receptor (RLR) pathways. Further analysis reveals that HTNV NP and Gc proteins target upstream molecules of MAVS, such as RIG-I and MDA-5, with Gc exhibiting stronger inhibition of IFN-I responses than NP. Mechanistically, NP and Gc proteins interact with tripartite motif protein 25 (TRIM25) to competitively inhibit its interaction with RIG-I/MDA5, suppressing RLR signaling pathways. Our study unveils a cross-talk between HTNV NP/Gc proteins and host immune response, providing valuable insights into the pathogenic mechanism of HTNV.

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.

Innate Immunity to Orthohantaviruses: Could Divergent Immune Interactions Explain Host-specific Disease Outcomes?

The genus Orthohantavirus (family Hantaviridae, order Bunyavirales) consists of numerous genetic and pathologically distinct viral species found within rodent and mammalian insectivore populations world-wide. Although reservoir hosts experience persistent asymptomatic infection, numerous rodent-borne orthohantaviruses cause severe disease when transmitted to humans, with case-fatality rates up to 40%. The first isolation of an orthohantavirus occurred in 1976 and, since then, the field has made significant progress in understanding the immune correlates of disease, viral interactions with the human innate immune response, and the immune kinetics of reservoir hosts. Much still remains elusive regarding the molecular mechanisms of orthohantavirus recognition by the innate immune response and viral antagonism within the reservoir host, however. This review provides a summary of the last 45 years of research into orthohantavirus interaction with the host innate immune response. This summary includes discussion of current knowledge involving human, non-reservoir rodent, and reservoir innate immune responses to viruses which cause hemorrhagic fever with renal syndrome and hantavirus cardio-pulmonary syndrome. Review of the literature concludes with a brief proposition for the development of novel tools needed to drive forward investigations into the molecular mechanisms of innate immune activation and consequences for disease outcomes in the various hosts for orthohantaviruses.

Hantavirus infection in type I interferon receptor-deficient (A129) mice

Type I interferon receptor knockout mice (strain A129) were assessed as a disease model of hantavirus infection. A range of infection routes (intramuscular, intraperitoneal and intranasal) were assessed using minimally passaged Seoul virus (strain Humber). Dissemination of virus to the spleen, kidney and lung was observed at 5 days after intramuscular and intraperitoneal challenge, which was resolved by day 14. In contrast, intranasal challenge of A129 mice demonstrated virus tropism to the lung, which was maintained to day 14 post-challenge. These data support the use of the A129 mouse model for future infection studies and the in vivo evaluation of interventions.

Interactions of Viral Proteins from Pathogenic and Low or Non-Pathogenic Orthohantaviruses with Human Type I Interferon Signaling

Rodent-borne orthohantaviruses are asymptomatic in their natural reservoir, but they can cause severe diseases in humans. Although an exacerbated immune response relates to hantaviral pathologies, orthohantaviruses have to antagonize the antiviral interferon (IFN) response to successfully propagate in infected cells. We studied interactions of structural and nonstructural (NSs) proteins of pathogenic Puumala (PUUV), low-pathogenic Tula (TULV), and non-pathogenic Prospect Hill (PHV) viruses, with human type I and III IFN (IFN-I and IFN-III) pathways. The NSs proteins of all three viruses inhibited the RIG-I-activated IFNβ promoter, while only the glycoprotein precursor (GPC) of PUUV, or its cleavage product Gn/Gc, and the nucleocapsid (N) of TULV inhibited it. Moreover, the GPC of both PUUV and TULV antagonized the promoter of IFN-stimulated responsive elements (ISRE). Different viral proteins could thus contribute to inhibition of IFNβ response in a viral context. While PUUV and TULV strains replicated similarly, whether expressing entire or truncated NSs proteins, only PUUV encoding a wild type NSs protein led to late IFN expression and activation of IFN-stimulated genes (ISG). This, together with the identification of particular domains of NSs proteins and different biological processes that are associated with cellular proteins in complex with NSs proteins, suggested that the activation of IFN-I is probably not the only antiviral pathway to be counteracted by orthohantaviruses and that NSs proteins could have multiple inhibitory functions.

Biodefense Implications of New-World Hantaviruses

Hantaviruses, part of the Bunyaviridae family, are a genus of negative-sense, single-stranded RNA viruses that cause two major diseases: New-World Hantavirus Cardiopulmonary Syndrome and Old-World Hemorrhagic Fever with Renal Syndrome. Hantaviruses generally are found worldwide with each disease corresponding to their respective hemispheres. New-World Hantaviruses spread by specific rodent-host reservoirs and are categorized as emerging viruses that pose a threat to global health and security due to their high mortality rate and ease of transmission. Incidentally, reports of Hantavirus categorization as a bioweapon are often contradicted as both US National Institute of Allergy and Infectious Diseases and the Centers for Disease Control and Prevention refer to them as Category A and C bioagents respectively, each retaining qualitative levels of importance and severity. Concerns of Hantavirus being engineered into a novel bioagent has been thwarted by Hantaviruses being difficult to culture, isolate, and purify limiting its ability to be weaponized. However, the natural properties of Hantaviruses pose a threat that can be exploited by conventional and unconventional forces. This review seeks to clarify the categorization of Hantaviruses as a bioweapon, whilst defining the practicality of employing New-World Hantaviruses and their effect on armies, infrastructure, and civilian targets.

The Glycoprotein and Nucleocapsid Protein of Hantaviruses Manipulate Autophagy Flux to Restrain Host Innate Immune Responses

Hantavirus infection, which causes severe zoonotic diseases with high mortality in humans, has become a global public health concern. Here, we demonstrate that Hantaan virus (HTNV), the prevalent prototype of the hantavirus in Asia, can restrain innate immune responses by manipulating host autophagy flux. HTNV induces complete mitophagy at the early stage of infection but incomplete autophagy at the late stage, and these responses involve the viral glycoprotein (Gn) and nucleocapsid protein (NP), respectively. Gn translocates to mitochondria and interacts with TUFM, recruiting LC3B and promoting mitophagy. Gn-induced mitophagy inhibits type I interferon (IFN) responses by degrading MAVS. Additionally, we found that NP competes with Gn for binding to LC3B, which inhibits Gn-mediated autophagosome formation, and interacts with SNAP29, which prevents autophagosome-lysosome fusion. Thus, NP disturbs the autophagic degradation of Gn. These findings highlight how hantaviruses repurpose host autophagy and evade innate immune responses for their life cycle and pathogenesis.

Vaccines and Therapeutics Against Hantaviruses

Hantaviruses (HVs) are rodent-transmitted viruses that can cause hantavirus cardiopulmonary syndrome (HCPS) in the Americas and hemorrhagic fever with renal syndrome (HFRS) in Eurasia. Together, these viruses have annually caused approximately 200,000 human infections worldwide in recent years, with a case fatality rate of 5–15% for HFRS and up to 40% for HCPS. There is currently no effective treatment available for either HFRS or HCPS. Only whole virus inactivated vaccines against HTNV or SEOV are licensed for use in the Republic of Korea and China, but the protective efficacies of these vaccines are uncertain. To a large extent, the immune correlates of protection against hantavirus are not known. In this review, we summarized the epidemiology, virology, and pathogenesis of four HFRS-causing viruses, HTNV, SEOV, PUUV, and DOBV, and two HCPS-causing viruses, ANDV and SNV, and then discussed the existing knowledge on vaccines and therapeutics against these diseases. We think that this information will shed light on the rational development of new vaccines and treatments.

Puumala and Tula Virus Differ in Replication Kinetics and Innate Immune Stimulation in Human Endothelial Cells and Macrophages

Old world hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) upon zoonotic transmission to humans. In Europe, the Puumala virus (PUUV) is the main causative agent of HFRS. Tula virus (TULV) is also widely distributed in Europe, but there is little knowledge about the pathogenicity of TULV for humans, as reported cases are rare. We studied the replication of TULV in different cell types in comparison to the pathogenic PUUV and analyzed differences in stimulation of innate immunity. While both viruses replicated to a similar extent in interferon (IFN)-deficient Vero E6 cells, TULV replication in human lung epithelial (A549) cells was slower and less efficient when compared to PUUV. In contrast to PUUV, no replication of TULV could be detected in human microvascular endothelial cells and in macrophages. While a strong innate immune response towards PUUV infection was evident at 48 h post infection, TULV infection triggered only a weak IFN response late after infection of A549 cells. Using appropriate in vitro cell culture models for the orthohantavirus infection, we could demonstrate major differences in host cell tropism, replication kinetics, and innate immune induction between pathogenic PUUV and the presumably non- or low-pathogenic TULV that are not observed in Vero E6 cells and may contribute to differences in virulence.

Unique Interferon Pathway Regulation by the Andes Virus Nucleocapsid Protein Is Conferred by Phosphorylation of Serine 386

Andes virus (ANDV) causes hantavirus pulmonary syndrome (HPS) and is the only hantavirus shown to spread person to person and cause a highly lethal HPS-like disease in Syrian hamsters. The unique ability of ANDV N protein to inhibit beta interferon (IFNβ) induction may contribute to its virulence and spread. Here we analyzed IFNβ regulation by ANDV N protein substituted with divergent residues from the nearly identical Maporal virus (MAPV) N protein. We found that MAPV N fails to inhibit IFNβ signaling and that replacing ANDV residues 252 to 296 with a hypervariable domain (HVD) from MAPV N prevents IFNβ regulation. In addition, changing ANDV residue S386 to the histidine present in MAPV N or the alanine present in other hantaviruses prevented ANDV N from regulating IFNβ induction. In contrast, replacing serine with phosphoserine-mimetic aspartic acid (S386D) in ANDV N robustly inhibited interferon regulatory factor 3 (IRF3) phosphorylation and IFNβ induction. Additionally, the MAPV N protein gained the ability to inhibit IRF3 phosphorylation and IFNβ induction when ANDV HVD and H386D replaced MAPV residues. Mass spectroscopy analysis of N protein from ANDV-infected cells revealed that S386 is phosphorylated, newly classifying ANDV N as a phosphoprotein and phosphorylated S386 as a unique determinant of IFN regulation. In this context, the finding that the ANDV HVD is required for IFN regulation by S386 but dispensable for IFN regulation by D386 suggests a role for HVD in kinase recruitment and S386 phosphorylation. These findings delineate elements within the ANDV N protein that can be targeted to attenuate ANDV and suggest targeting cellular kinases as potential ANDV therapeutics.IMPORTANCE ANDV contains virulence determinants that uniquely permit it to spread person to person and cause highly lethal HPS in immunocompetent hamsters. We discovered that ANDV S386 and an ANDV-specific hypervariable domain permit ANDV N to inhibit IFN induction and that IFN regulation is directed by phosphomimetic S386D substitutions in ANDV N. In addition, MAPV N proteins containing D386 and ANDV HVD gained the ability to inhibit IFN induction. Validating these findings, mass spectroscopy analysis revealed that S386 of ANDV N protein is uniquely phosphorylated during ANDV infection. Collectively, these findings reveal new paradigms for ANDV N protein as a phosphoprotein and IFN pathway regulator and suggest new mechanisms for hantavirus regulation of cellular kinases and signaling pathways. Our findings define novel IFN-regulating virulence determinants of ANDV, identify residues that can be modified to attenuate ANDV for vaccine development, and suggest the potential for kinase inhibitors to therapeutically restrict ANDV replication.

Targeted inhibition of hantavirus replication and intracranial pathogenesis by a chimeric protein-delivered siRNA

Hantavirus (HV) infection, which underlies hantavirus hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, remains to be a severe clinical challenge. Here, we synthesized small interfering RNAs (siRNAs) that target the encoding sequences of HV strain 76-118, and validated their inhibitory role in virus replication in HV-infected monkey kidney Vero E6 cells. A chimeric protein, 3G1-Cκ-tP, consisting of a single-chain antibody fragment (3G1) against the HV surface envelop glycoprotein, the constant region of human immunoglobulin κ chain (Cκ), and truncated protamine (amino acids 8-29, tP), was further generated. The fusion protein showed high affinity to HV antigen on the infected cell membrane, and internalized through clathrin-mediated endocytosis; it bound to siRNAs via the basic nucleic acid-rich protamine fragment, leading to their specific delivery into HV-infected cells and efficient inhibition of virus replication. An encephalitis mouse model was established via intracranial HV administration. Intraperitoneal injection of siRNAs complexed with 3G1-Cκ-tP achieved specific distribution of siRNAs in HV-infected brain cells, significantly reduced HV antigen levels, and effective protection from HV infection-derived animal death. These results provide a compelling rationale for novel therapeutic protocols designed for HV infection and related disorders.

Clinical characterization of two severe cases of hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses Puumala and Dobrava-Belgrade genotype Sochi

BACKGROUND

Hantavirus disease belongs to the emerging infections. The clinical picture and severity of infections differ between hantavirus species and may even vary between hantavirus genotypes. The mechanisms that lead to the broad variance of severity in infected patients are not completely understood. Host- and virus-specific factors are considered.

CASE PRESENTATION

We analyzed severe cases of hantavirus disease in two young women. The first case was caused by Puumala virus (PUUV) infection in Germany; the second case describes the infection with Dobrava-Belgrade virus (DOBV) in Russia. Symptoms, laboratory parameters and cytokine levels were analyzed and compared between the two patients. Serological and sequence analysis revealed that PUUV was the infecting agent for the German patient and the infection of the Russian patient was caused by Dobrava-Belgrade virus genotype Sochi (DOBV-Sochi). The symptoms in the initial phase of the diseases did not differ noticeably between both patients. However, deterioration of laboratory parameter values was prolonged and stronger in DOBV-Sochi than in PUUV infection. Circulating endothelial progenitor cells (cEPCs), known to be responsible for endothelial repair, were mobilized in both infections. Striking differences were observed in the temporal course and level of cytokine upregulation. Levels of angiopoietin-2 (Ang-2), vascular endothelial growth factor (VEGF), and stromal derived factor-1 (SDF-1α) were increased in both infections; but, sustained and more pronounced elevation was observed in DOBV-Sochi infection.

CONCLUSIONS

Severe hantavirus disease caused by different hantavirus species did not differ in the general symptoms and clinical characteristics. However, we observed a prolonged clinical course and a late and enhanced mobilization of cytokines in DOBV-Sochi infection. The differences in cytokine deregulation may contribute to the observed variation in the clinical course.

What Do We Know about How Hantaviruses Interact with Their Different Hosts?

Hantaviruses, like other members of the Bunyaviridae family, are emerging viruses that are able to cause hemorrhagic fevers. Occasional transmission to humans is due to inhalation of contaminated aerosolized excreta from infected rodents. Hantaviruses are asymptomatic in their rodent or insectivore natural hosts with which they have co-evolved for millions of years. In contrast, hantaviruses cause different pathologies in humans with varying mortality rates, depending on the hantavirus species and its geographic origin. Cases of hemorrhagic fever with renal syndrome (HFRS) have been reported in Europe and Asia, while hantavirus cardiopulmonary syndromes (HCPS) are observed in the Americas. In some cases, diseases caused by Old World hantaviruses exhibit HCPS-like symptoms. Although the etiologic agents of HFRS were identified in the early 1980s, the way hantaviruses interact with their different hosts still remains elusive. What are the entry receptors? How do hantaviruses propagate in the organism and how do they cope with the immune system? This review summarizes recent data documenting interactions established by pathogenic and nonpathogenic hantaviruses with their natural or human hosts that could highlight their different outcomes.

Genetic characterization of hantaviruses isolated from rodents in the port cities of Heilongjiang, China, in 2014

Background

Hantavirus is a tripartite negative-sense RNA virus. It can infect humans through contaminated rodent excreta and causes two types of fatal human diseases: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). China exhibits the highest HFRS occurrence rate in the world, and the Heilongjiang area is one of the most severely infected regions.

Results

To obtain additional insights into the genetic characteristics of hantaviruses in the port cities of the Heilongjiang area in China, a molecular epidemiological investigation of hantaviruses isolated from rodents was performed in 2014. A total of 649 rodents (11 murine species and 1 shrew species) were caught in 12 port cities in Heilongjiang. Among these rodents, the most common species was A. agrarius, and the second-most common was R. norvegicus. A viral gene PCR assay revealed the presence of two specific genotypes of hantavirus, referred to as Hantaan virus (HTNV) and Seoul virus (SEOV), and the positive SEOV infection rate was higher than that for HTNV. A genetic analysis based on partial M segment sequences indicated that all of the isolates belonging to SEOV could be assigned to two genetic lineages, whereas the isolate belonging to HTNV could be assigned to only one genetic lineage.

Conclusions

These results suggested that HTNV and SEOV are circulating in A. agrarius and R. norvegicus in the port cities in the area of Heilongjiang, but SEOV may be the dominant common hantavirus.

Hantaviral Proteins: Structure, Functions, and Role in Hantavirus Infection

Hantaviruses are the members of the family Bunyaviridae that are naturally maintained in the populations of small mammals, mostly rodents. Most of these viruses can easily infect humans through contact with aerosols or dust generated by contaminated animal waste products. Depending on the particular Hantavirus involved, human infection could result in either hemorrhagic fever with renal syndrome or in Hantavirus cardiopulmonary syndrome. In the past few years, clinical cases of the Hantavirus caused diseases have been on the rise. Understanding structure of the Hantavirus genome and the functions of the key viral proteins are critical for the therapeutic agents’ research. This paper gives a brief overview of the current knowledge on the structure and properties of the Hantavirus nucleoprotein and the glycoproteins.

Effects of Different Doses of Nucleocapsid Protein from Hantaan Virus A9 Strain on Regulation of Interferon Signaling

Hantaan virus A9 strain (HTNV A9) is an etiologic agent of hemorrhagic fever with renal syndrome in China. The virulence of the pathogenic hantaviruses is determined by their ability to alter key signaling pathways of early interferon (IFN) induction within cells. The potential role of HTNV A9 structural proteins, such as nucleocapsid (N) and envelope glycoproteins (Gn and Gc), in regulating human's innate antiviral immune response has not yet been clarified. In this study, we investigated the effect of HTNV A9 N protein on the regulation of the IFN pathway. We found that A9 N protein can influence the host innate immune response by regulating the activation of IFNβ. The A9 N protein stimulates IFN response in low doses, whereas significantly inhibits IFNβ production at high doses. Furthermore, A9 N protein constitutively inhibits nuclear factor kappa B activation. A high dose of A9 N protein could inhibit either Poly IC-induced IFNβ or vesicular stomatitis virus-induced IFNβ and interferon-stimulated gene production. Our results indicate that HTNV A9 N protein helps virus establish successful infection by downregulating the IFN response and shed new light to the understanding of the interaction between the host innate immunity and virus during Hantaan virus infection.

Viral load of patients with hantavirus pulmonary syndrome in Argentina

Hantavirus causes severe illness including pneumonia, which leads to hospitalization and often death. At present, there is no specific treatment available. The hantavirus pathogenesis is not well understood, but most likely both virus-mediated and host-mediated mechanisms, are involved. The aim of this study was to correlate viral load in samples of hantavirus pulmonary syndrome cases and hantavirus infected individuals, with clinical epidemiological parameters and disease outcome. The variables that could potentially be related with viral load were analyzed. The retrospective study included 73 cases or household contacts, with different clinical evolution. Viral load was measured by reverse-transcription and real time polymerase chain reaction. There was no statistically significant association between blood viral RNA levels and severity of disease. However, viral load was inversely correlated with IgG response in a statistically significant manner. The level of viral RNA was significantly higher in patients infected with Andes virus South lineage, and was markedly low in persons infected with Laguna Negra virus. These results suggest that the infecting viral genotype is associated with disease severity, and that high viral load is associated with a low specific IgG response. Sex, age and disease severity were not related with viral load. Further investigations increasing strikingly the number of cases and also limiting the variables to be studied are necessary.