Reduced circulating CD4+CD25+ cell populations in haemorrhagic fever with renal syndrome

Hemorrhagic fever viruses: Pathogenesis, therapeutics, and emerging and re-emerging potential

Hemorrhagic fever viruses (HFVs) pose a threat to global public health owing to the emergence and re-emergence of highly fatal diseases. Viral hemorrhagic fevers (VHFs) caused by these viruses are mostly characterized by an acute febrile syndrome with coagulation abnormalities and generalized hemorrhage that may lead to life-threatening organ dysfunction. Currently, the events underlying the viral pathogenicity associated with multiple organ dysfunction syndrome still underexplored. In this minireview, we address the current knowledge of the mechanisms underlying VHFs pathogenesis and discuss the available development of preventive and therapeutic options to treat these infections. Furthermore, we discuss the potential of HFVs to cause worldwide emergencies along with factors that favor their spread beyond their original niches.

Hantavirus Induced Kidney Disease

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

Comparison of Lymphocyte Populations in Patients With Dobrava or Puumala orthohantavirus Infection

Hemorrhagic fever with renal syndrome (HFRS), caused by Dobrava (DOBV) and Puumala (PUUV) orthohantaviruses, is an endemic disease in Slovenia. DOBV is mainly responsible for a more severe disease, whereas PUUV usually causes a milder form. Therefore, the aim of our study was to determine whether any differences in lymphocyte population in patients infected with these two viruses exist. Mononuclear cells from peripheral blood (PBMCs) were isolated from DOBV or PUUV infected patients and different lymphocyte subpopulations were analyzed with flow cytometry. Decreased concentrations of lymphocyte subpopulation were observed in DOBV and in PUUV infected patients compared with a healthy control, which was especially evident in DOBV infected patients. The lower values of T cells are likely due to the extravasation of the activated cells from the circulation to the infected tissue. Higher percentage of NK cells were detected in DOBV infected patients in comparison to PUUV infected patients, which could be associated with a more severe HFRS caused by DOBV. PUUV infected patients had a significantly higher concentration of activated T cell subsets, expressing markers CD25, CD69, and HLA-DR in comparison to DOBV infected patients. Higher activation of T cell subsets in PUUV infected patients could be a contributor to a milder HFRS. Further studies are necessary to elucidate the relation between the protective and the harmful role of activated lymphocytes subsets in HFRS pathogenesis.

The role of Treg population in pathogenesis of Crimean Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a severe human infection caused by CCHF virus (CCHFV). Today, although the literature on CCHF pathogenesis is still limited, it is thought to be associated with immunosuppression in the early phase of infection followed by pro-inflammatory immune response that may lead to fatal outcomes. The aim of this study is to investigate the role of regulatory T-cells (T_reg cells) in the pathogenesis of CCHFV. Peripheral blood mononuclear cell samples collected from 14 acute CCHF patients with mild disease course and 13 healthy subjects were included in this study. T_reg expression and functional levels were analyzed by flow cytometry. T_reg cells were identified as CD4+CD25 + CD127dim cells, and their functional levels were compared by measuring their ability to suppress CD69 and CD154 expression by activated T-cells. The flow cytometry analysis revealed that total T-cell and helper T-cell levels did not vary between the two groups. In contrast, CCHF patients displayed higher T_reg cell levels but lower T_reg suppressive activities when compared with control subjects. This is the first study on the involvement of T_reg cells in CCHF pathogenesis. Our results indicate that even though T_reg cell levels are elevated during acute phase of CCHF infection, not all generated T_reg cells has immunosuppressive capacity, and therefore may not represent 'true' T_reg cell population. Future studies on the intrinsic mechanisms responsible for the reduced T_reg inhibitory activities are required for further enlightening the CCHF pathogenesis, especially in the acute phase of the disease.

Hantavirus induced cardiopulmonary syndrome: A public health concern

Hantavirus cardiopulmonary syndrome is characterized by pulmonary capillary leakage and alveolar flooding, resulting in 50% mortality due to fulminant hypoxic respiratory failure. In addition, depression of cardiac function ensues, which complicates the picture with cardiogenic shock. Early diagnosis and appropriate use of extracorporeal membrane oxygenation (ECMO) are amongst the lifesaving interventions in this fatal illness. However, a recent case report demonstrates that implementation of high volume continuous hemofilteration along with protective ventilation reverses the cardiogenic shock within few hours in hantavirus infected patients. This review article is focused on the recent advances in clinical features, diagnosis, management, epidemiology, and pathogenesis of hantavirus induced cardiopulmonary syndrome. It provides information for clinicians to help in correct diagnosis during the early stages of viral infection that could improve the prognosis of this viral illness.

Involvement of CD8+ T cells in the development of renal hemorrhage in a mouse model of hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) is caused by hantavirus infection. Although host immunity is thought to be involved in the pathogenesis of HFRS, the mechanism remains to be elucidated. A mouse model of HFRS, which showed renal hemorrhage similar to that seen in patients, has been developed previously. In this study, we aimed to clarify whether CD4⁺ and CD8⁺ T cells are involved in the development of renal hemorrhage in the mouse model. At 2 days before virus inoculation, CD4⁺ or CD8⁺ T cells in 6-week-old BALB/c mice were depleted by administration of antibodies. The CD4⁺ T cell-depleted mice developed signs of disease such as transient weight loss, ruffled fur and renal hemorrhage as in non-depleted mice. In contrast, the CD8⁺ T cell-depleted mice showed no signs of disease. After determination of CTL epitopes on the viral glycoprotein in BALB/c mice, the quantity of virus-specific CTLs was analyzed using an MHC tetramer. The quantity of virus-specific CTLs markedly increased in spleens and kidneys of virus-infected mice. However, the quantity in high-pathogenic clone-infected mice was comparable to that in low-pathogenic clone-infected mice. We previously reported that the high-pathogenic clone propagated more efficiently than the low-pathogenic clone in kidneys of mice during the course of infection. Therefore, there is a possibility that the balance between quantities of the target and effector is important for disease outcome. In conclusion, this study showed that CD8⁺ T cells are involved in the development of renal hemorrhage in a mouse model of HFRS.

Cytotoxic immune responses in the lungs correlate to disease severity in patients with hantavirus infection

Hantavirus infections may cause severe and sometime life-threatening lung failure. The pathogenesis is not fully known and there is an urgent need for effective treatment. We aimed to investigate the association between pulmonary viral load and immune responses, and their relation to disease severity. Bronchoscopy with sampling of bronchoalveolar lavage (BAL) fluid was performed in 17 patients with acute Puumala hantavirus infection and 16 healthy volunteers acting as controls. Lymphocyte subsets, granzyme concentrations, and viral load were determined by flow cytometry, enzyme-linked immunosorbent assay (ELISA), and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. Analyses of BAL fluid revealed significantly higher numbers of activated CD8⁺ T cells and natural killer (NK) cells, as well as higher concentrations of the cytotoxins granzymes A and B in hantavirus-infected patients, compared to controls. In patients, Puumala hantavirus RNA was detected in 88 % of BAL cell samples and correlated inversely to the T cell response. The magnitude of the pulmonary cytotoxic lymphocyte response correlated to the severity of disease and systemic organ dysfunction, in terms of need for supplemental oxygen treatment, hypotension, and laboratory data indicating renal failure, cardiac dysfunction, vascular leakage, and cell damage. Regulatory T cell numbers were significantly lower in patients compared to controls, and may reflect inadequate immune regulation during hantavirus infection. Hantavirus infection elicits a pronounced cytotoxic lymphocyte response in the lungs. The magnitude of the immune response was associated with disease severity. These results give insights into the pathogenesis and possibilities for new treatments.

Hemorrhagic Fever with Renal Syndrome: Pathogenesis and Clinical Picture

Hantaan virus (HTNV) causes hemorrhagic fever with renal syndrome (HFRS), which is a zoonosis endemic in eastern Asia, especially in China. The reservoir host of HTNV is field mouse (Apodemus agraricus). The main manifestation of HFRS, including acute kidney injury, increases vascular permeability, and coagulation abnormalities. In this paper, we review the current knowledge of the pathogenesis of HFRS including virus factor, immunity factor and host genetic factors. Furthermore, the treatment and prevention will be discussed.

Circulating T-regulatory cells in PNET: a prospective study

PURPOSE

Bone marrow regulatory T-cells (Tregs) have been evaluated in patients with peripheral neuroectodermal tumor (PNET); data on peripheral blood circulating Tregs are lacking. The objective of our study was to determine baseline Tregs (both Treg frequency and absolute number) in patients with PNET and correlate with patient characteristics, and observe their change with treatment and relapse.

METHODS

Five milliliters blood was evaluated in de novo patients with PNET at diagnosis, post-neoadjuvant chemotherapy and at relapse/progression, along with nine healthy controls using flow-cytometric analysis for Treg cells (CD4+ CD25+ FoxP3+).

RESULTS

Thirty-seven patients with median age 17 years; male/female ratio 5.1:1 had significantly higher baseline absolute Tregs than controls (mean 338.95 ± 264.63/mm(3) vs. 34.83 ± 24.90/mm(3); P < 0.001). Patients with fever had a significantly higher mean Treg frequency than those without fever (11.27 ± 8.36% vs. 8.40 ± 2.58%; P = 0.014). There was significant reduction in the circulating Tregs after neoadjuvant chemotherapy (mean 339.78 ± 294.31/mm(3) vs. 82.09 ± 91.25/mm(3), P < 0.001) and rise at progression (n = 13) as compared to values post-neoadjuvant chemotherapy (mean 240.92 ± 191.90/mm(3) vs. 57.67 ± 39.01/mm(3), P = 0.012). There was no significant difference in the event-free survival (EFS) or overall survival (OS) between the high and low Treg cell groups (2-year EFS 51.6% vs. 52.1%; P = 0.689 and OS 61.3% vs. 59.2%; P = 0.891).

CONCLUSION

This study on circulating Tregs in PNET demonstrated that peripheral blood Tregs are higher in patients than healthy controls. There was significant reduction in Tregs with chemotherapy and rise at progression.

Hantaviruses: past, present and future

ABSTRACT: 

Hantaviruses productively infect endothelial cells in their rodent reservoirs and humans, but the infection only causes disease in humans – hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome. Despite the enormous progress that has been made in understanding the pathogenesis and immune responses of hantavirus infection, there is a large gap in our molecular-based knowledge of hantaviral proteins in their structures, functions and the mechanisms that facilitate their entry, replication and assembly. Importantly, we know little about the specific viral determinants and viral protein–host interactions that drive differences noted in immune responses between the reservoir and humans. This review discusses our current understanding and future work needed for unraveling the biology of these viruses in their reservoirs and in humans.

Regulatory T cell response correlates with the severity of human hantavirus infection

OBJECTIVES

Hantaviruses are an important group of emerging zoonotic pathogens, with significant mortality rates. Immunopathology is thought to be important in hantaviral disease, but the balance between protective and harmful responses is unknown. We studied Puumala hantavirus (PUUV) infection, which causes hemorrhagic fever with renal syndrome (HFRS) with a generally mild but highly variable clinical course.

METHODS

Clinical data and blood samples were collected from 24 patients with acute PUUV infection, and analyzed by flow cytometry and quantitative PCR.

RESULTS

The patients had a significantly increased frequency of CD4(+) and CD8(+) cells expressing the cell cycle marker Ki-67, but the magnitude of the effector T cell response did not correlate with disease severity. The frequency of FOXP3(+) regulatory T (Treg) cells expressing Ki-67 was also increased, and likewise did not correlate with disease outcome. In contrast, the level of FOXP3 expression, a surrogate of the suppressive phenotype, had a strong positive correlation with disease severity. This correlation was also found in samples taken 6-12 months after the HFRS.

CONCLUSIONS

The best predictor of a severe disease course in HFRS was the FOXP3(+) Treg cell response, suggesting that the role of Treg cells in acute human hantaviral infections may be deleterious.

The pathogenesis of nephropathia epidemica: new knowledge and unanswered questions

Puumala virus (PUUV) causes an acute hemorrhagic fever with renal syndrome (HFRS), a zoonosis also called nephropathia epidemica (NE). The reservoir host of PUUV is the bank vole (Myodes glareolus). Herein we review the main clinical manifestations of NE, acute kidney injury, increased vascular permeability, coagulation abnormalities as well as pulmonary, cardiac, central nervous system and ocular manifestations of the disease. Several biomarkers of disease severity have recently been discovered: interleukin-6, pentraxin-3, C-reactive protein, indoleamine 2,3-dioxygenase, cell-free DNA, soluble urokinase-type plasminogen activator, GATA-3 and Mac-2 binding protein. The role of cytokines, vascular endothelial growth hormone, complement, bradykinin, cellular immune response and other mechanisms in the pathogenesis of NE as well as host genetic factors will be discussed. Finally therapeutic aspects and directions for further research will be handled.

Hantavirus infection: an emerging infectious disease causing acute renal failure

The function of the kidney with its highly differentiated and specialized cell types is affected by infection with several viruses. Viral infections of the kidney have a negative impact not only on patients undergoing renal transplantation and immunosuppression. Besides the increasing number of patients suffering from HIV-associated nephropathy, another group of viruses infects immunocompetent patients and induces renal failure. Hantaviruses belong nowadays to the emerging zoonoses that increase in number and geographic distribution. The viruses are distributed worldwide in endemic areas and distribution seems to expand. Together with the increase in the number of cases in the last few years, the understanding of epidemiology and pathology has deepened and some concepts had to be changed. Symptoms and mortality vary between species. The classification refers to geographical distribution: New World hantaviruses causing hantavirus cardiopulmonary syndrome (HCPS) and Old World hantaviruses causing hemorrhagic fever with renal syndrome (HFRS). Indeed, in most HFRS cases, the kidney is mainly affected and HCPS is characterized by cardiopulmonary involvement. But the picture of strict organ tropism is changing and reports of pulmonary findings and nonrenal manifestations in infections with Old World hantaviruses are increasing. However, the overall symptoms-vascular alterations and leakage-that are responsible for organ failure are characteristic for all diseases caused by hantaviruses.

Regulatory T cells in children with recently diagnosed type 1 diabetes

BACKGROUND

Regulatory T cells have an important role in the control of immune reactivity against self antigens and probably play a role in pathogenesis of type 1 diabetes (T1D). We aimed to determine the frequency of regulatory T cells in recently diagnosed children with/T1D.

MATERIALS AND METHODS

20 children with/T1D and 20 healthy children of matched age and sex as controls were enrolled in this study. All cases were subjected to a thorough history taking, full clinical examinations and investigations which include; insulin C peptide levels and flow cytometric detection of B-, T-lymphocytes and regulatory T cells.

RESULTS

Insulin C peptide level was significantly lower in children with/ T1D compared with controls. The percentages of B and T-lymphocytes were not significantly different between patients and controls. The percentages of CD4+CD25+High and CD4+CD25+High Foxp3+ cells both in total lymphocytes and in CD4+ lymphocytes were significantly decreased in patients than controls, while the percentages of total CD4+CD25+ and CD4+CD25+Intermediate both in total lymphocytes and in CD4+ lymphocytes were not significantly different between patients and controls. The geometric mean of fluorescence intensity (MFI) of Foxp3+ expression in CD4+CD25+High cells was significantly decreased in patients than controls. Positive correlations were observed between both age and insulin C peptide and frequency of CD4+CD25+High Foxp3.

CONCLUSION

The percentage of regulatory T cells; CD4+CD25+High Foxp3 was decreased in children with recent T1D and may have a role in its pathogenesis. Their role as a prognostic signifi cance and their relation to various complications should be explored.

Seoul virus-infected rat lung endothelial cells and alveolar macrophages differ in their ability to support virus replication and induce regulatory T cell phenotypes

Hantaviruses cause a persistent infection in reservoir hosts that is attributed to the upregulation of regulatory responses and downregulation of proinflammatory responses. To determine whether rat alveolar macrophages (AMs) and lung microvascular endothelial cells (LMVECs) support Seoul virus (SEOV) replication and contribute to the induction of an environment that polarizes CD4(+) T cell differentiation toward a regulatory T (Treg) cell phenotype, cultured primary rat AMs and LMVECs were mock infected or infected with SEOV and analyzed for viral replication, cytokine and chemokine responses, and expression of cell surface markers that are related to T cell activation. Allogeneic CD4(+) T cells were cocultured with SEOV-infected or mock-infected AMs or LMVECs and analyzed for helper T cell (i.e., Treg, Th17, Th1, and Th2) marker expression and Treg cell frequency. SEOV RNA and infectious particles in culture media were detected in both cell types, but at higher levels in LMVECs than in AMs postinfection. Expression of Ifnβ, Ccl5, and Cxcl10 and surface major histocompatibility complex class II (MHC-II) and MHC-I was not altered by SEOV infection in either cell type. SEOV infection significantly increased Tgfβ mRNA in AMs and the amount of programmed cell death 1 ligand 1 (PD-L1) in LMVECs. SEOV-infected LMVECs, but not AMs, induced a significant increase in Foxp3 expression and Treg cell frequency in allogeneic CD4(+) T cells, which was virus replication and cell contact dependent. These data suggest that in addition to supporting viral replication, AMs and LMVECs play distinct roles in hantavirus persistence by creating a regulatory environment through increased Tgfβ, PD-L1, and Treg cell activity.

CD4+CD25+High Foxp3+ Regulatory T Cells, B Lymphocytes, and T Lymphocytes in Patients With Acute ITP in Assiut Children Hospital

We aimed to examine the levels of lymphocyte subsets and regulatory T cells in patients with newly diagnosed immune thrombocytopenia (ITP) and their correlation with the course of ITP. The study included 40 pediatric patients with acute ITP and 30 controls. Lymphocytes and regulatory T cells were analyzed by flow cytometry. The percentages of CD19+ and CD8+ cells were significantly increased while that of CD4+ cells and CD4+/CD8+ ratio were significantly decreased. The percentages of CD4+CD25+High and CD4+CD25+High forkhead box protein 3 (Foxp3+) cells and the expression of Foxp3+ in CD4+CD25+High cells were significantly decreased in patients. Age, platelet count, and mean platelet volume (MPV) in patients with brief duration of thrombocytopenia were significantly decreased than in those with prolonged duration. The percentages of CD8+, CD4+CD25+High, and CD4+CD25+High Foxp3+ were significantly increased in patients with brief duration. Age, platelet count and MPV, and CD8+ cells had prognostic significance. CD4+CD25+High Foxp+ T cells may be a helpful prognostic marker in children with acute ITP.

Pathogenesis and host response in Syrian hamsters following intranasal infection with Andes virus

Hantavirus pulmonary syndrome (HPS), also referred to as hantavirus cardiopulmonary syndrome (HCPS), is a rare but frequently fatal disease caused by New World hantaviruses. In humans HPS is associated with severe pulmonary edema and cardiogenic shock; however, the pathogenesis of this disease remains unclear largely due to a lack of suitable animal models for the study of disease progression. In this study we monitored clinical, virological, pathophysiological parameters and host immunological responses to decipher pathological factors and events in the lethal Syrian hamster model of HPS following intranasal inoculation of Andes virus. Transcriptional profiling of the host gene responses demonstrated a suppression of innate immune responses in most organs analyzed during the early stage of infection, except for in the lung which had low level activation of several pro-inflammatory genes. During this phase Andes virus established a systemic infection in hamsters, with viral antigen readily detectable in the endothelium of the majority of tissues analyzed by 7-8 days post-inoculation. Despite wide-spread infection, histological analysis confirmed pathological abnormalities were almost exclusively found in the lungs. Immediately preceding clinical signs of disease, intense activation of pro-inflammatory and Th1/Th2 responses were observed in the lungs as well as the heart, but not in peripheral organs, suggesting that localized immune-modulations by infection is paramount to pathogenesis. Throughout the course of infection a strong suppression of regulatory T-cell responses was noted and is hypothesized to be the basis of the aberrant immune activations. The unique and comprehensive monitoring of host immune responses to hantavirus infection increases our understanding of the immuno-pathogenesis of HPS and will facilitate the development of treatment strategies targeting deleterious host immunological responses.

The adaptor protein Bam32 in human dendritic cells participates in the regulation of MHC class I-induced CD8+ T cell activation

The B lymphocyte adaptor molecule of 32 kDa (Bam32) is strongly induced during the maturation of dendritic cells (DC). Most known functions of Bam32 are related to the signaling of the B cell receptor for Ag. Because DC do not express receptors specific for Ags, we aim at characterizing the role of Bam32 in human monocyte-derived DC in this study. Our results show that binding of allogeneic T cells to mature DC causes accumulation of Bam32 on the contact sites and that this translocation is mimicked by Ab-mediated engagement of MHC class I. Silencing of Bam32 in mature monocyte-derived DC results in an enhanced proliferation of CD8(+) T cells in an Ag-specific T cell proliferation assay. Further studies identify galectin-1 as an intracellular binding partner of Bam32. Regulating immune responses via regulatory T cell (Treg) modulation is one of the many immunological activities attributed to galectin-1. Therefore, we assayed mixed leukocyte reactions for Treg expansion and found fewer Treg in reactions stimulated with DC silenced for Bam32 compared to reactions stimulated with DC treated with a nontarget control. Based on our findings, we propose a role for Bam32 in the signaling of MHC class I molecules in professional Ag-presenting DC for the regulation of CD8(+) T cell activation. It is distinct from that of MHC class I recognized by CD8(+) T cells leading to target [corrected] cell death. Thus, our data pinpoint a novel level of T cell regulation that may be of biological relevance.

Longitudinal analysis of the human T cell response during acute hantavirus infection

Longitudinal studies of T cell immune responses during viral infections in humans are essential for our understanding of how effector T cell responses develop, clear infection, and provide long-lasting immunity. Here, following an outbreak of a Puumala hantavirus infection in the human population, we longitudinally analyzed the primary CD8 T cell response in infected individuals from the first onset of clinical symptoms until viral clearance. A vigorous CD8 T cell response was observed early following the onset of clinical symptoms, determined by the presence of high numbers of Ki67(+)CD38(+)HLA-DR(+) effector CD8 T cells. This response encompassed up to 50% of total blood CD8 T cells, and it subsequently contracted in parallel with a decrease in viral load. Expression levels of perforin and granzyme B were high throughout the initial T cell response and likewise normalized following viral clearance. When monitoring regulatory components, no induction of regulatory CD4 or CD8 T cells was observed in the patients during the infection. However, CD8 as well as CD4 T cells exhibited a distinct expression profile of inhibitory PD-1 and CTLA-4 molecules. The present results provide insight into the development of the T cell response in humans, from the very onset of clinical symptoms following a viral infection to resolution of the disease.

T cells and pathogenesis of hantavirus cardiopulmonary syndrome and hemorrhagic fever with renal syndrome

We previously hypothesized that increased capillary permeability observed in both hantavirus cardiopulmonary syndrome (HCPS) and hemorrhagic fever with renal syndrome (HFRS) may be caused by hantavirus-specific cytotoxic T cells attacking endothelial cells presenting viral antigens on their surface based on clinical observations and in vitro experiments. In HCPS, hantavirus-specific T cell responses positively correlated with disease severity. In HFRS, in one report, contrary to HCPS, T cell responses negatively correlated with disease severity, but in another report the number of regulatory T cells, which are thought to suppress T cell responses, negatively correlated with disease severity. In rat experiments, in which hantavirus causes persistent infection, depletion of regulatory T cells helped infected rats clear virus without inducing immunopathology. These seemingly contradictory findings may suggest delicate balance in T cell responses between protection and immunopathogenesis. Both too strong and too weak T cell responses may lead to severe disease. It is important to clarify the role of T cells in these diseases for better treatment (whether to suppress T cell functions) and protection (vaccine design) which may need to take into account viral factors and the influence of HLA on T cell responses.

Hantavirus protein interactions regulate cellular functions and signaling responses

Rodent-borne pathogenic hantaviruses cause two severe and often lethal zoonotic diseases: hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Currently, no US FDA-approved therapeutics or vaccines are available for HFRS/HCPS. Infections with hantaviruses are not lytic, and it is currently not known exactly why infections in humans cause disease. A better understanding of how hantaviruses interfere with normal cell functions and activation of innate and adaptive immune responses might provide clues to future development of specific treatment and/or vaccines against hantavirus infection. In this article, the current knowledge regarding immune responses observed in patients, hantavirus interference with cellular proteins and signaling pathways, and possible approaches in the development of therapeutics are discussed.

Involvement of T helper type 17 and regulatory T cell activity in tumour immunology of bladder carcinoma

T helper type 17 (Th17) and regulatory T cells (T(reg) ) play an important role in the pathogenesis of inflammation and autoimmune disorders. Recent studies have suggested that they also had an impact on tumour immunology. However, the relationship between Th17 and T(reg) cells in the pathogenesis of bladder carcinoma is still unclear. Flow cytometry was used to analyse the numbers, phenotype and cytokine production of Th17 cells in peripheral blood and tumour tissue from bladder carcinoma patients, in parallel with analysis of T(reg) cells. The suppressor capacity of T(reg) and the potential effects of interleukin (IL)-2 on the differentiation of Th17 and T(reg) cells in vitro were studied in a T cell stimulation and suppression assays. The results were as follows: Th17 cells were enriched in the tumours of patients with bladder carcinoma compared with the peripheral blood of patients and controls; patients with bladder carcinoma had a higher proportion of T(reg) cells in peripheral blood compared with healthy controls and nearly all patients examined showed a relative enrichment of tumour-infiltrating T(reg) with respect to peripheral blood; there appeared to be an inverse relationship between tumour-infiltrating Th17 and T(reg) cells; IL-2 could convert tumour-infiltrating T(reg) cells cultured in the presence of the autologous irradiated CD3(-) fraction into Th17 cells, down-regulate forkhead box P2 expression and suppressive capacity of T(reg) cells. This study is the first to define the frequency and characteristics of Th17 cells in bladder carcinoma. We suggest that the balance between Th17 and T(reg) cells may be involved in the development or progression of bladder carcinoma.

Alpha/beta interferon (IFN-alpha/beta)-independent induction of IFN-lambda1 (interleukin-29) in response to Hantaan virus infection

Type III interferons ([IFNs] IFN-lambda and interleukin-28 and -29 [IL-28/29]) are recently recognized cytokines with innate antiviral effects similar to those of type I IFNs (IFN-alpha/beta). Like IFN-alpha/beta, IFN-lambda-expression can be induced by viruses, and it is believed that type I and III IFNs are regulated in the same manner. Hantaviruses are weak IFN-alpha/beta inducers and have surprisingly been shown to activate IFN-alpha/beta-independent IFN-stimulated gene (ISG) expression. Here, we show that in Hantaan virus (HTNV)-infected human epithelial A549 cells, induction of IFN-lambda1 preceded induction of MxA and IFN-beta by 12 and 24 h, respectively, and IFN-alpha was not induced at all. Furthermore, induction of IFN-lambda1 and MxA was observed in HTNV-infected African green monkey epithelial Vero E6 cells, a cell line that cannot produce type I IFNs, clearly showing that HTNV can induce IFN-lambda1 and ISGs in the complete absence of IFN-alpha/beta. In HTNV-infected human fibroblast MRC-5 cells, which lack the IFN-lambda receptor, induction of MxA coincided in time with IFN-beta-induction. UV-inactivated HTNV did not induce any IFNs or MxA in any cell line, showing that activation of IFN-lambda1 is dependent on replicating virus. Induction of both IFN-beta and IFN-lambda1 in A549 cells after poly(I:C)-stimulation was strongly inhibited in HTNV-infected cells, suggesting that HTNV can inhibit signaling pathways used to simultaneously activate types I and III IFNs. In conclusion, we show that HTNV can cause type I IFN-independent IFN-lambda1 induction and IFN-lambda1-specific ISG induction. Importantly, the results suggest the existence of specific signaling pathways that induce IFN-lambda1 without simultaneous type I IFN induction during virus infection.