Crimean Congo hemorrhagic fever virus infects human monocyte-derived dendritic cells

Vascular dysfunction in hemorrhagic viral fevers: opportunities for organotypic modeling

The hemorrhagic fever viruses (HFVs) cause severe or fatal infections in humans. Named after their common symptom hemorrhage, these viruses induce significant vascular dysfunction by affecting endothelial cells, altering immunity, and disrupting the clotting system. Despite advances in treatments, such as cytokine blocking therapies, disease modifying treatment for this class of pathogen remains elusive. Improved understanding of the pathogenesis of these infections could provide new avenues to treatment. While animal models and traditional 2D cell cultures have contributed insight into the mechanisms by which these pathogens affect the vasculature, these models fall short in replicatingin vivohuman vascular dynamics. The emergence of microphysiological systems (MPSs) offers promising avenues for modeling these complex interactions. These MPS or 'organ-on-chip' models present opportunities to better mimic human vascular responses and thus aid in treatment development. In this review, we explore the impact of HFV on the vasculature by causing endothelial dysfunction, blood clotting irregularities, and immune dysregulation. We highlight how existing MPS have elucidated features of HFV pathogenesis as well as discuss existing knowledge gaps and the challenges in modeling these interactions using MPS. Understanding the intricate mechanisms of vascular dysfunction caused by HFV is crucial in developing therapies not only for these infections, but also for other vasculotropic conditions like sepsis.

Crimean-Congo haemorrhagic fever virus uses LDLR to bind and enter host cells

Climate change and population densities accelerated transmission of highly pathogenic viruses to humans, including the Crimean-Congo haemorrhagic fever virus (CCHFV). Here we report that the Low Density Lipoprotein Receptor (LDLR) is a critical receptor for CCHFV cell entry, playing a vital role in CCHFV infection in cell culture and blood vessel organoids. The interaction between CCHFV and LDLR is highly specific, with other members of the LDLR protein family failing to bind to or neutralize the virus. Biosensor experiments demonstrate that LDLR specifically binds the surface glycoproteins of CCHFV. Importantly, mice lacking LDLR exhibit a delay in CCHFV-induced disease. Furthermore, we identified the presence of Apolipoprotein E (ApoE) on CCHFV particles. Our findings highlight the essential role of LDLR in CCHFV infection, irrespective of ApoE presence, when the virus is produced in tick cells. This discovery holds profound implications for the development of future therapies against CCHFV.

Crimean-Congo Hemorrhagic Fever Virus: Progress in Vaccine Development

Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the Nairoviridae family and Bunyavirales order, is transmitted to humans via tick bites or contact with the blood of infected animals. It can cause severe symptoms, including hemorrhagic fever, with a mortality rate between 5 to 30%. CCHFV is classified as a high-priority pathogen by the World Health Organization (WHO) due to its high fatality rate and the absence of effective medical countermeasures. CCHFV is endemic in several regions across the world, including Africa, Europe, the Middle East, and Asia, and has the potential for global spread. The emergence of the disease in new areas, as well as the presence of the tick vector in countries without reported cases, emphasizes the need for preventive measures to be taken. In the past, the lack of a suitable animal model susceptible to CCHFV infection has been a major obstacle in the development of vaccines and treatments. However, recent advances in biotechnology and the availability of suitable animal models have significantly expedited the development of vaccines against CCHF. These advancements have not only contributed to an enhanced understanding of the pathogenesis of CCHF but have also facilitated the evaluation of potential vaccine candidates. This review outlines the immune response to CCHFV and animal models utilized for the study of CCHFV and highlights the progress made in CCHFV vaccine studies. Despite remarkable advancements in vaccine development for CCHFV, it remains crucial to prioritize continued research, collaboration, and investment in this field.

Crimean-Congo hemorrhagic fever: Immunopathogenesis and recent advances in the development of vaccines

Crimean-Congo hemorrhagic fever is a serious vector-borne zoonotic viral infection which leads to severe illness and fatalities in people living in endemic regions and becoming infected sporadically. Hyalomma ticks are responsible for the transmission of the virus which belongs to the family Nairoviridae. This disease spreads through ticks bite, infected tissues, or blood of viremic animals, and from infected humans to others. Serological studies also indicate the presence of the virus in various domestic and wild animals to be a risk factor for the transmission of the disease. Crimean-Congo hemorrhagic fever virus elicits many immune responses during the infection including inflammatory, innate, and adaptive immune responses. The development of an effective vaccine could be a promising method for the control and prevention of disease in endemic areas. The purpose of this review is to highlight the importance of CCHF, its mode of transmission, the interaction of the virus with the hosts and ticks, immunopathogenesis, and advances in immunization.

The Relationship Between Cytokine Concentrations and Severity Scoring Index for Crimean-Congo Hemorrhagic Fever

Background This study aimed to investigate the effects of serum high mobility group box-1 (HMGB1), interleukin (IL)-6, IL-8, IL-1β, IL-10, and tumor necrosis factor alpha (TNF-α) levels on disease severity and mortality in Crimean-Congo hemorrhagic fever (CCHF) patients. Materials and methods This study was performed prospectively in the intensive care unit (ICU) and infection ward of a tertiary hospital in the Republic of Türkiye. Patients aged 18 years and older diagnosed with CCHF were included. Results Our study included 30 patients, of whom 83.3% were male, where the mean age was 51.6±14.35 years. The most common clinical findings in patients were malaise (90%) and myalgia (63.3%). In our study, IL-1β levels were found to be 1173.6 (783.0-1823.0) pg/mL, IL-6 69.9 (56.8-133.1) pg/mL, IL-8 191.2 (152.8-516.9) pg/mL, TNF-α 129.5 (104.9-270.8), HMGB1 37.01 (29.26-75.18), and IL-10 190.1 (IQR: 147.8-387.8) pg/mL. The patients' median Severity Scoring Index (SSI) score was found to be 2.5 (1.8-5.5). There was a moderate correlation between the patients' SSI score and serum IL-6 (r=0.464, p=0.010), TNF-α (r=0.420, p=0.021), and IL-10 levels (r=0.518, p=0.003), and a weak correlation between serum HMGB1 (r=0.392, p=0.032). The correlation between SSI and creatine phosphokinase (CPK) levels (r=0.499, p=0.036) was observed to be moderate. Conclusion It was seen that IL-10, IL-6, TNF-α, HMBG-1, and CPK levels evaluated at the CCHF patients' time of admission to the clinic and SSI clinical score were found to be significantly related. It is clear that more studies with patients and groups of healthy volunteers are needed on this subject.

An Immunoinformatics Approach to Design a Potent Multi-Epitope Vaccine against Asia-1 Genotype of Crimean-Congo Haemorrhagic Fever Virus Using the Structural Glycoproteins as a Target

Crimean-Congo haemorrhagic fever (CCHF), caused by Crimean-Congo haemorrhagic fever virus (CCHFV), is a disease of worldwide importance (endemic yet not limited to Asia, Middle East, and Africa) and has triggered several outbreaks amounting to a case fatality rate of 10-40% as per the World Health Organization. Genetic diversity and phylogenetic data revealed that the Asia-1 genotype of CCHFV remained dominant in Pakistan, where 688 confirmed cases were reported between the 2012-2022 period. Currently, no approved vaccine is available to tackle the viral infection. Epitope-based vaccine design has gained significant attention in recent years due to its safety, timeliness, and cost efficiency compared to conventional vaccines. In the present study, we employed a robust immunoinformatics-based approach targeting the structural glycoproteins G1 and G2 of CCHFV (Asia-1 genotype) to design a multi-epitope vaccine construct. Five B-cells and six cytotoxic T-lymphocytes (CTL) epitopes were mapped and finalized from G1 and G2 and were fused with suitable linkers (EAAAK, GGGS, AAY, and GPGPG), a PADRE sequence (13 aa), and an adjuvant (50S ribosomal protein L7/L12) to formulate a chimeric vaccine construct. The selected CTL epitopes showed high affinity and stable binding with the binding groove of common human HLA class I molecules (HLA-A*02:01 and HLA-B*44:02) and mouse major histocompatibility complex class I molecules. The chimeric vaccine was predicted to be an antigenic, non-allergenic, and soluble molecule with a suitable physicochemical profile. Molecular docking and molecular dynamics simulation indicated a stable and energetically favourable interaction between the constructed antigen and Toll-like receptors (TLR2, TLR3, and TLR4). Our results demonstrated that innate, adaptive, and humoral immune responses could be elicited upon administration of such a potent muti-epitope vaccine construct. These results could be helpful for an experimental vaccinologist to develop an effective vaccine against the Asia-1 genotype of CCHFV.

Multi-omics insights into host-viral response and pathogenesis in Crimean-Congo hemorrhagic fever viruses for novel therapeutic target

The pathogenesis and host-viral interactions of the Crimean–Congo hemorrhagic fever orthonairovirus (CCHFV) are convoluted and not well evaluated. Application of the multi-omics system biology approaches, including biological network analysis in elucidating the complex host-viral response, interrogates the viral pathogenesis. The present study aimed to fingerprint the system-level alterations during acute CCHFV-infection and the cellular immune responses during productive CCHFV-replication in vitro. We used system-wide network-based system biology analysis of peripheral blood mononuclear cells (PBMCs) from a longitudinal cohort of CCHF patients during the acute phase of infection and after one year of recovery (convalescent phase) followed by untargeted quantitative proteomics analysis of the most permissive CCHFV-infected Huh7 and SW13 cells. In the RNAseq analysis of the PBMCs, comparing the acute and convalescent-phase, we observed system-level host’s metabolic reprogramming towards central carbon and energy metabolism (CCEM) with distinct upregulation of oxidative phosphorylation (OXPHOS) during CCHFV-infection. Upon application of network-based system biology methods, negative coordination of the biological signaling systems like FOXO/Notch axis and Akt/mTOR/HIF-1 signaling with metabolic pathways during CCHFV-infection were observed. The temporal quantitative proteomics in Huh7 showed a dynamic change in the CCEM over time and concordant with the cross-sectional proteomics in SW13 cells. By blocking the two key CCEM pathways, glycolysis and glutaminolysis, viral replication was inhibited in vitro. Activation of key interferon stimulating genes during infection suggested the role of type I and II interferon-mediated antiviral mechanisms both at the system level and during progressive replication.

Crimean-Congo hemorrhagic fever (CCHF) is an emerging disease that is increasingly spreading to new populations. The condition is now endemic in almost 30 countries in sub-Saharan Africa, South-Eastern Europe, the Middle East and Central Asia. CCHF is caused by a tick-borne virus and can cause uncontrolled bleeding. It has a mortality rate of up to 40%, and there are currently no vaccines or effective treatments available.

All viruses depend entirely on their hosts for reproduction, and they achieve this through hijacking the molecular machinery of the cells they infect. However, little is known about how the CCHF virus does this and how the cells respond. To understand more about the relationship between the cell’s metabolism and viral replication, Neogi, Elaldi et al. studied immune cells taken from patients during an infection and one year later.

The gene activity of the cells showed that the virus prefers to hijack processes known as central carbon and energy metabolism. These are the main regulator of the cellular energy supply and the production of essential chemicals. By using cancer drugs to block these key pathways, Neogi, Elaldi et al. could reduce the viral reproduction in laboratory cells.

These findings provide a clearer understanding of how the CCHF virus replicates inside human cells. By interfering with these processes, researchers could develop new antiviral strategies to treat the disease. One of the cancer drugs tested in cells, 2-DG, has been approved for emergency use against COVID-19 in some countries. Neogi, Elaldi et al. are now studying this further in animals with the hope of reaching clinical trials in the future.

Immunobiology of Crimean-Congo hemorrhagic fever

Human infection with Crimean-Congo hemorrhagic fever virus (CCHFV), a tick-borne pathogen in the family Nairoviridae, can result in a spectrum of outcomes, ranging from asymptomatic infection through mild clinical signs to severe or fatal disease. Studies of CCHFV immunobiology have investigated the relationship between innate and adaptive immune responses with disease severity, attempting to elucidate factors associated with differential outcomes. In this article, we begin by highlighting unanswered questions, then review current efforts to answer them. We discuss in detail current clinical studies and research in laboratory animals on CCHF, including immune targets of infection and adaptive and innate immune responses. We summarize data about the role of the immune response in natural infections of animals and humans and experimental studies in vitro and in vivo and from evaluating immune-based therapies and vaccines, and present recommendations for future research.

Insights into the Pathogenesis of Viral Haemorrhagic Fever Based on Virus Tropism and Tissue Lesions of Natural Rift Valley Fever

Rift Valley fever phlebovirus (RVFV) infects humans and a wide range of ungulates and historically has caused devastating epidemics in Africa and the Arabian Peninsula. Lesions of naturally infected cases of Rift Valley fever (RVF) have only been described in detail in sheep with a few reports concerning cattle and humans. The most frequently observed lesion in both ruminants and humans is randomly distributed necrosis, particularly in the liver. Lesions supportive of vascular endothelial injury are also present and include mild hydropericardium, hydrothorax and ascites; marked pulmonary congestion and oedema; lymph node congestion and oedema; and haemorrhages in many tissues. Although a complete understanding of RVF pathogenesis is still lacking, antigen-presenting cells in the skin are likely the early targets of the virus. Following suppression of type I IFN production and necrosis of dermal cells, RVFV spreads systemically, resulting in infection and necrosis of other cells in a variety of organs. Failure of both the innate and adaptive immune responses to control infection is exacerbated by apoptosis of lymphocytes. An excessive pro-inflammatory cytokine and chemokine response leads to microcirculatory dysfunction. Additionally, impairment of the coagulation system results in widespread haemorrhages. Fatal outcomes result from multiorgan failure, oedema in many organs (including the lungs and brain), hypotension, and circulatory shock. Here, we summarize current understanding of RVF cellular tropism as informed by lesions caused by natural infections. We specifically examine how extant knowledge informs current understanding regarding pathogenesis of the haemorrhagic fever form of RVF, identifying opportunities for future research.

Differential Cell Line Susceptibility to Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe tick-borne viral disease of global concerns due to the increasing incidence and lack of effective treatments. The causative agent, CCHF virus (CCHFV), has been characterized for years; however, its tropism in cell lines of different host and tissue origins remains unclear. This study characterized the susceptibility of 16 human and 6 animal cell lines to CCHFV. Increased viral load and viral nucleoprotein expression, and productive CCHFV replication were detected in human vascular (HUVEC), renal (SW-13 and HEK-293), hepatic (Huh7), and cerebral (U-87 MG) cell lines, which were considered CCHFV-highly permissive cell lines. Renal cell lines derived from monkey and dog could also support CCHFV replication. This study evaluated the susceptibility of different cell lines to CCHFV and identified CCHFV-permissive cell lines. Our findings raise concerns regarding the use of cell lines in ex vivo studies of CCHFV and may have important implications for further fundamental research, which would promote understanding of CCHFV pathogenesis and transmission, as well as benefit designing strategies for disease prevention and control.

MicroRNA analysis from acute to convalescence in Crimean Congo hemorrhagic fever

Crimean Congo hemorrhagic fever (CCHF) is one of the most important viral infections and is caused by Crimean Congo hemorrhagic fever orthonairovirus (CCHFV). Severity of CCHF can vary from a mild and nonspecific illness to a severe disease with fatal outcomes. MicroRNAs (miRNAs) have an increasing impact on the different pathways of viral infections. Within the transition process from acute phase to convalescence with 18 CCHF patients, we investigated the impacts on miRNA via microarray for the first time. We also compared miRNA gene expression in 16 severe and 15 mild cases. We identified Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathways associated with significant miRNAs utilizing DIANA TOOLS mirPath v.3. In this study, miR-15b-5p and miR-29a-3p were significantly downregulated in statistical terms; miR-4741, miR-937-5p, miR-6068, miR-7110-5p, miR-6126, and miR-7107-5p were upregulated in acute cases in comparison with convalescent patients (p ≤ .05). In total, 28 miRNAs (8 downregulated, 20 upregulated) were differentially expressed in severe CCHF patients as compared with mild cases (p ≤ .05). Whereas miR-6732-3p, miR-4436b-5p, miR-483-3p, and miR-6807-5p had the highest downregulation, miR-532-5p, miR-142-5p, miR-29c-3p, and let-7f-5p had the highest upregulation in severe patients in comparison with mild cases. Consequently, we determined that CCHF-induced miRNAs are associated with antiviral and proinflammatory pathways in acute and severe cases. In comparison with convalescence, these miRNAs in acute period may be therapeutic targets.

[Crimean-Congo hemorrhagic fever, a future health problem in France?]

The Crimean-Congo hemorrhagic fever virus (CCHFV) is the etiological agent of a severe hemorrhagic fever affecting Africa, Asia and southern Europe. Climate changes of recent decades have recently led to a rise in the distribution of this virus. Still few scientific data are available on the biology of its vector, the tick, or its own biology, but the proven presence of human infections observed in Spain and animals with positive serology in Corsica should focus our attention on this pathogen. This review takes stock of the epidemiologic evolution of CCHF in Europe, notably in France.

Hazara virus and Crimean-Congo Hemorrhagic Fever Virus show a different pattern of entry in fully-polarized Caco-2 cell line

Crimean-Congo Hemorrhagic Fever Virus (CCHFV) and Hazara virus (HAZV) belong to the same viral serotype and family. HAZV has lately been used as a model system and surrogate to CCHFV. However, virus-host cell interaction and level of pathogenicity for these viruses are not well investigated nor compared. In this study, we compared HAZV and CCHFV infection of human polarized epithelial cells to shed light on similarities and differences in virus-host cell interaction between these two viruses. We investigated the pattern of infection of CCHFV and HAZV in fully polarized human cells, the Caco-2 cell line. Polarization of Caco-2 cells lead to difference in expression level and pattern of proteins between the apical and the basolateral membranes. We found that CCHFV virus, in contrast to HAZV, is more likely infecting polarized cells basolaterally. In addition, we found that cytokines/pro-inflammatory factors or other viral factors secreted from CCHFV infected moDC cells enhance the entry of CCHFV contrary to HAZV. We have shown that CCHFV and HAZV early in infection use different strategies for entry. The data presented in this study also highlight the important role of cytokines in CCHFV-host cell interaction.

Crimean-Congo Hemorrhagic Fever virus (CCHFV) is a tick-borne pathogen responsible for a severe acute fever disease in humans, requiring biosafety level 4 laboratory for handling. This is the reason why the molecular pathogenesis of CCHFV remains largely unknown. Hazara virus (HAZV), member of the same serogroup but nor responsible for human disease, is commonly used as surrogate model to study CCHFV in biosafety level 2 laboratory. As an important viral model, it is important to better understand its range of applicability. Using polarized Caco-2 cells, we showed HAZV doesn’t have the same pattern of infection in fully polarized cells than CCHFV. These data were confirmed using compounds able to modulate cell junctions: compounds leaded to opposite effect on respective virus infection capacity. All data together suggest that CCHFV and HAZV receptors have different localization on polarized Caco-2 cells. Moreover, using supernatant of HAZV or CCHFV infected monocyte-derived dendritic cells, we demonstrated that only factors released from CCHFV-infected moDCs are able to enhance CCHFV infection. To our knowledge, this study is the first one showing differences in HAZV and CCHFV entry into polarized target cells and in CCHFV infection modulation by a paracrine effect linked to infected dendritic cells.

The emerging tick-borne Crimean-Congo haemorrhagic fever virus: A narrative review

Crimean-Congo Haemorrhagic Fever (CCHF) is an increasingly relevant viral zoonosis caused by the negative-sense single-stranded (ss) RNA Crimean-Congo Haemorrhagic Fever Orthonairovirus (CCHFV) (Nairoviridae family, Bunyavirales order). The viral genome is divided into three segments (L-M-S) of distinct size and functions. The infection is generally mediated by a tick vector, in particular belonging to the Hyalomma genus, and the transmission follows a tick-vertebrate-tick ecologic cycle, with asymptomatic infected animals functioning as reservoirs and amplifiers for CCHFV. Human hosts could be infected primarily through infected ticks or by contact with infected hosts or their body fluids and tissues, also in a nosocomial way and in occupational contexts. Infected symptomatic patients generally manifest a nonspecific illness, which progresses across four stages, with possibly lethal outcomes. Disease outbreaks show a widespread geographic diffusion and a highly variable mortality rate, dramatically peaking in untreated patients. The lack of an adequate animal model and the elevated virus biological risk (only manageable under biosafety level 4 conditions) represent strongly limiting factors for a better characterization of the disease and for the development of specific therapies and vaccines. The present review discusses updated information on CCHFV-related disease, including details about the virus (taxonomy, structure, life cycle, transmission modalities) and considering CCHF pathogenesis, epidemiology and current strategies (diagnostic, therapeutic and preventive).

Dual RNA-Seq characterization of host and pathogen gene expression in liver cells infected with Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus that can cause a hemorrhagic fever in humans, with a case fatality rate of up to 40%. Cases of CCHFV have been reported in Africa, Asia, and southern Europe; and recently, due to the expanding range of its vector, autochthonous cases have been reported in Spain. Although it was discovered over 70 years ago, our understanding of the pathogenesis of this virus remains limited. We used RNA-Seq in two human liver cell lines (HepG2 and Huh7) infected with CCHFV (strain IbAr10200), to examine kinetic changes in host expression and viral replication simultaneously at 1 and 3 days post infection. Through this, numerous host pathways were identified that were modulated by the virus including: antiviral response and endothelial cell leakage. Notably, the genes encoding DDX60, a cytosolic component of the RIG-I signalling pathway and OAS2 were both shown to be dysregulated. Interestingly, PTPRR was induced in Huh7 cells but not HepG2 cells. This has been associated with the TLR9 signalling cascade, and polymorphisms in TLR9 have been associated with poor outcomes in patients. Additionally, we performed whole-genome sequencing on CCHFV to assess viral diversity over time, and its relationship to the host response. As a result, we have demonstrated that through next-generation mRNA deep-sequencing it is possible to not only examine mRNA gene expression, but also to examine viral quasispecies and typing of the infecting strain. This demonstrates a proof-of-principle that CCHFV specimens can be analyzed to identify both the virus and host biomarkers that may have implications for prognosis.

Factors related to fatalities and clinical progression of Crimean-Congo hemorrhagic fever patients and the effects of IL 28-B gene polymorphism

Mortality rates of Crimean-Congo hemorrhagic fever (CCHF) vary from 5% to 80%. However, there is no clear information available about why this disease is fatal for some people while others recover. In this study, the factors related to fatalities and serious clinical progression of CCHF patients and the correlation between serious prognosis and IL 28-B gene polymorphism were investigated. The study included 107 patients with a preliminary diagnosis of CCHF, and the patients were found positive for CCHFV RNA based on polymerase chain reaction (PCR) analysis. The IL 28-B rs12979860 polymorphism was identified by PCR "restriction fragment length polymorphism" (PCR-RFLP) analysis using blood samples from the patients. In addition to the IL 28-B analysis results, a variety of data along with laboratory records obtained during the hospital stay were evaluated using statistical analysis. Of the 107 cases, nine were fatal (8.4%), while the other patients recovered and were discharged. Twenty-four patients had the CC genotype (22.43%), 64 had the CT genotype (59.81%), and 19 had the TT genotype (17.76%). Of the nine patients who died, three had the CC genotype (33.33%) and six had the CT genotype (66.67%). None of the patients who died had the TT genotype. Symptoms and findings of diarrhea, abdominal pain, hemorrhage, and rash were more common in fatal cases than in non-fatal cases. The IL 28-B rs12979860 polymorphism was not found to have a statistically significant correlation with fatality or symptoms indicating serious clinical progression in CCHF patients. As has been observed in previous studies, our study showed that leukocytosis, abdominal pain and diarrhea were more common in fatal cases.

Kyasanur Forest disease virus infection activates human vascular endothelial cells and monocyte-derived dendritic cells

Kyasanur Forest disease virus (KFDV) is a highly pathogenic tick-borne flavivirus enzootic to India. In humans, KFDV causes a severe febrile disease. In some infected individuals, hemorrhagic manifestations, such as bleeding from the nose and gums and gastrointestinal bleeding with hematemesis and/or blood in the stool, have been reported. However, the mechanisms underlying these hemorrhagic complications remain unknown, and there is no information about the specific target cells for KFDV. We investigated the interaction of KFDV with vascular endothelial cells (ECs) and monocyte-derived dendritic cells (moDCs), which are key targets for several other hemorrhagic viruses. Here, we report that ECs are permissive to KFDV infection, which leads to their activation, as demonstrated by the upregulation of E-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 at the mRNA and protein levels. Increased expression of these adhesive molecules correlated with increased leukocyte adhesion. Infected ECs upregulated the expression of interleukin (IL)-6 but not IL-8. Additionally, moDCs were permissive to KFDV infection, leading to increased release of IL-6 and tumor necrosis factor-α. Supernatants from KFDV-infected moDCs caused EC activation, as measured by leukocyte adhesion. The results indicate that ECs and moDCs can be targets for KFDV and that both direct and indirect mechanisms can contribute to EC activation.

Interactions of Human Dermal Dendritic Cells and Langerhans Cells Treated with Hyalomma Tick Saliva with Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus is one the most important and wide spread tick-borne viruses. Very little is known about the transmission from the tick and the early aspects of pathogenesis. Here, we generate human cutaneous antigen presenting cells-dermal dendritic cells and Langerhans cells-from umbilical cord progenitor cells. In order to mimic the environment created during tick feeding, tick salivary gland extract was generated from semi-engorged Hyalomma marginatum ticks. Our findings indicate that human dermal dendritic cells and Langerhans cells are susceptible and permissive to Crimean-Congo hemorrhagic fever virus infection, however, to different degrees. Infection leads to cell activation and cytokine/chemokine secretion, although these responses vary between the different cell types. Hyalomma marginatum salivary gland extract had minimal effect on cell responses, with some synergy with viral infection with respect to cytokine secretion. However, salivary gland extract appeared to inhibit antigen presenting cells (APCs) migration. Based on the findings here we hypothesize that human dermal dendritic cells and Langerhans cells serve as early target cells. Rather affecting Crimean-Congo hemorrhagic fever virus replication, tick saliva likely immunomodulates and inhibits migration of these APCs from the feeding site.

Dynamics of viral load in Crimean Congo hemorrhagic fever

Crimean Congo hemorrhagic fever (CCHF) is a viral zoonotic disease with high mortality rate. There are only a few studies on viral load in CCHF. In our study, we revealed the dynamics of viral load and its relationship with mortality in early phase of the disease. A total of 138 serum samples were collected from 23 patients. All patients had positive PCR for CCHF on admission. Serum samples were obtained daily from all patients for the first 6 days of hospitalization and stored at -80°C for viral load measurement. We found statistically significant difference between mean number of viremic serum samples of fatal and non-fatal patients. Furthermore, non-fatal cases' viral loads demonstrated statistically significant decreases over time; however, we could not observe a similar trend in viral loads of fatal cases. Limited number of studies on CCHF indicate that score of the contest between CCHF virus and immune system determines the survival in CCHF and viral load is found to be the most prognostic factor. In our study, we found that there is a notable decrease trend in viral loads of non-fatal patients over time and this clearance of CCHF virus is significantly related with survival.

Apoptosis during arenavirus infection: mechanisms and evasion strategies

In recent years there has been a greatly increased interest in the interactions of arenaviruses with the apoptotic machinery, and particularly the extent to which these interactions may be an important contributor to pathogenesis. Here we summarize the current state of our knowledge on this subject and address the potential for interplay with other immunological mechanisms known to be regulated by these viruses. We also compare and contrast what is known for arenavirus-induced apoptosis with observations from other segmented hemorrhagic fever viruses.

Development of vaccines against Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever virus (CCHFV) is a deadly human pathogen of the utmost seriousness being highly lethal causing devastating disease symptoms that result in intense and prolonged suffering to those infected. During the past 40years, this virus has repeatedly caused sporadic outbreaks responsible for relatively low numbers of human casualties, but with an alarming fatality rate of up to 80% in clinically infected patients. CCHFV is transmitted to humans by Hyalomma ticks and contact with the blood of viremic livestock, additionally cases of human-to-human transmission are not uncommon in nosocomial settings. The incidence of CCHF closely matches the geographical range of permissive ticks, which are widespread throughout Africa, Asia, the Middle East and Europe. As such, CCHFV is the most widespread tick-borne virus on earth. It is a concern that recent data shows the geographic distribution of Hyalomma ticks is expanding. Migratory birds are also disseminating Hyalomma ticks into more northerly parts of Europe thus potentially exposing naïve human populations to CCHFV. The virus has been imported into the UK on two occasions in the last five years with the first fatal case being confirmed in 2012. A licensed vaccine to CCHF is not available. In this review, we discuss the background and complications surrounding this limitation and examine the current status and recent advances in the development of vaccines against CCHFV.

Cytokine response in crimean-congo hemorrhagic fever virus infection

We described the predictive role of cytokines in fatality of Crimean Congo Hemorrhagic Fever Virus (CCHFV) infection by using daily clinical sera samples. Consequent serum samples of the selected patients in different severity groups and healthy controls were examined by using human cytokine 17-plex assay. We included 12 (23%) mild, 30 (58%) moderate, 10 (19%) severe patients, and 10 healthy volunteers. The mean age of the patients was 52 (sd 15), 52% were female. Forty-six patients (88%) received ribavirin. During disease course, the median levels of IL-6, IL-8, IL-10, IL-10/12, IFN-γ, MCP-1, and MIP-1b were found to be significantly higher among CCHF patients than the healthy controls. Within the first 5 days after onset of disease, among the fatal cases, the median levels of IL-6 and IL-8 were found to be significantly higher than the survived ones (Fig. 3), and MCP-1 was elevated among fatal cases, but statistical significance was not detected. In receiver operating characteristic (ROC) analysis, IL-8 (92%), IL-6 (92%), MCP-1 (79%) were found to be the most significant cytokines in predicting the fatality rates in the early period of the disease (5 days). IL-6 and IL-8 can predict the poor outcome, within the first 5 days of disease course. Elevated IL-6 and IL-8 levels within first 5 days could be used as prognostic markers.

The role of ticks in the maintenance and transmission of Crimean-Congo hemorrhagic fever virus: A review of published field and laboratory studies

This manuscript is part of a series of reviews that aim to cover published research on Crimean-Congo hemorrhagic fever (CCHF) and its etiological agent, CCHF virus (CCHFV). The virus is maintained and transmitted in a vertical and horizontal transmission cycle involving a variety of wild and domestic vertebrate species that act as amplification hosts, without showing signs of illness. These vertebrates have traditionally been considered reservoirs of CCHFV, but in fact they develop only a transient viremia, while the virus can persist in ticks for their entire lifespan, and can also be transmitted vertically to the next generation. As a result, ticks are now considered to be both the vector and the reservoir for the virus. CCHFV has been detected in a wide range of tick species, but only a few have been proven to be vectors and reservoirs, mainly because most published studies have been performed under a broad variety of conditions, precluding definitive characterization. This article reviews the published literature, summarizes current knowledge of the role of ticks in CCHFV maintenance and transmission and provides guidance for how to fill the knowledge gaps. Special focus is given to existing data on tick species in which vertical passage has been demonstrated under natural or experimental conditions. At the same time, we identify earlier reports that used unreliable methods and perceptions to ascribe a vector role to some species of ticks, and have contributed to confusion regarding viral transmission. We also examine epidemiological pathways of CCHFV circulation and discuss priority areas for future research.

Crimean-Congo Hemorrhagic Fever: Tick-Host-Virus Interactions

Crimean-Congo hemorrhagic fever virus (CCHFV) is transmitted to humans by bite of infected ticks or by direct contact with blood or tissues of viremic patients or animals. It causes to humans a severe disease with fatality up to 30%. The current knowledge about the vector-host-CCHFV interactions is very limited due to the high-level containment required for CCHFV studies. Among ticks, Hyalomma spp. are considered the most competent virus vectors. CCHFV evades the tick immune response, and following its replication in the lining of the tick's midgut, it is disseminated by the hemolymph in the salivary glands and reproductive organs. The introduction of salivary gland secretions into the host cells is the major route via which CCHFV enters the host. Following an initial amplification at the site of inoculation, the virus is spread to the target organs. Apoptosis is induced via both intrinsic and extrinsic pathways. Genetic factors and immune status of the host may affect the release of cytokines which play a major role in disease progression and outcome. It is expected that the use of new technology of metabolomics, transcriptomics and proteomics will lead to improved understanding of CCHFV-host interactions and identify potential targets for blocking the CCHFV transmission.

Expression and characterization of codon-optimized Crimean-Congo hemorrhagic fever virus Gn glycoprotein in insect cells

Crimean-Congo hemorrhagic fever virus (CCHFV) is a major cause of tick-borne viral hemorrhagic disease in the world. Despite of its importance as a deadly pathogen, there is currently no licensed vaccine against CCHF disease. The attachment glycoprotein of CCHFV (Gn) is a potentially important target for protective antiviral immune responses. To characterize the expression of recombinant CCHFV Gn in an insect-cell-based system, we developed a gene expression system expressing the full-length coding sequence under a polyhedron promoter in Sf9 cells using recombinant baculovirus. Recombinant Gn was purified by affinity chromatography, and the immunoreactivity of the protein was evaluated using sera from patients with confirmed CCHF infection. Codon-optimized Gn was successfully expressed, and the product had the expected molecular weight for CCHFV Gn glycoprotein of 37 kDa. In time course studies, the optimum expression of Gn occurred between 36 and 48 hours postinfection. The immunoreactivity of the recombinant protein in Western blot assay against human sera was positive and was similar to the results obtained with the anti-V5 tag antibody. Additionally, mice were subjected to subcutaneous injection with recombinant Gn, and the cellular and humoral immune response was monitored. The results showed that recombinant Gn protein was highly immunogenic and could elicit high titers of antigen-specific antibodies. Induction of the inflammatory cytokine interferon-gamma and the regulatory cytokine IL-10 was also detected. In conclusion, a recombinant baculovirus harboring CCHFV Gn was constructed and expressed in Sf9 host cells for the first time, and it was demonstrated that this approach is a suitable expression system for producing immunogenic CCHFV Gn protein without any biosafety concerns.

Uukuniemi Virus as a Tick-Borne Virus Model

In the last decade, novel tick-borne pathogenic phleboviruses in the family Bunyaviridae, all closely related to Uukuniemi virus (UUKV), have emerged on different continents. To reproduce the tick-mammal switch in vitro, we first established a reverse genetics system to rescue UUKV with a genome close to that of the authentic virus isolated from the Ixodes ricinus tick reservoir. The IRE/CTVM19 and IRE/CTVM20 cell lines, both derived from I. ricinus, were susceptible to the virus rescued from plasmid DNAs and supported production of the virus over many weeks, indicating that infection was persistent. The glycoprotein G_C was mainly highly mannosylated on tick cell-derived viral progeny. The second envelope viral protein, G_N, carried mostly N-glycans not recognized by the classical glycosidases peptide-N-glycosidase F (PNGase F) and endoglycosidase H (Endo H). Treatment with β-mercaptoethanol did not impact the apparent molecular weight of G_N. On viruses originating from mammalian BHK-21 cells, G_N glycosylations were exclusively sensitive to PNGase F, and the electrophoretic mobility of the protein was substantially slower after the reduction of disulfide bonds. Furthermore, the amount of viral nucleoprotein per focus forming unit differed markedly whether viruses were produced in tick or BHK-21 cells, suggesting a higher infectivity for tick cell-derived viruses. Together, our results indicate that UUKV particles derived from vector tick cells have glycosylation and structural specificities that may influence the initial infection in mammalian hosts. This study also highlights the importance of working with viruses originating from arthropod vector cells in investigations of the cell biology of arbovirus transmission and entry into mammalian hosts.

IMPORTANCE Tick-borne phleboviruses represent a growing threat to humans globally. Although ticks are important vectors of infectious emerging diseases, previous studies have mainly involved virus stocks produced in mammalian cells. This limitation tends to minimize the importance of host alternation in virus transmission to humans and initial infection at the molecular level. With this study, we have developed an in vitro tick cell-based model that allows production of the tick-borne Uukuniemi virus to high titers. Using this system, we found that virions derived from tick cells have specific structural properties and N-glycans that may enhance virus infectivity for mammalian cells. By shedding light on molecular aspects of tick-derived viral particles, our data illustrate the importance of considering the host switch in studying early virus-mammalian receptor/cell interactions. The information gained here lays the basis for future research on not only tick-borne phleboviruses but also all viruses and other pathogens transmitted by ticks.

Early Bunyavirus-Host Cell Interactions

The Bunyaviridae is the largest family of RNA viruses, with over 350 members worldwide. Several of these viruses cause severe diseases in livestock and humans. With an increasing number and frequency of outbreaks, bunyaviruses represent a growing threat to public health and agricultural productivity globally. Yet, the receptors, cellular factors and endocytic pathways used by these emerging pathogens to infect cells remain largely uncharacterized. The focus of this review is on the early steps of bunyavirus infection, from virus binding to penetration from endosomes. We address current knowledge and advances for members from each genus in the Bunyaviridae family regarding virus receptors, uptake, intracellular trafficking and fusion.

Molecular Insights into Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne pathogen that causes high morbidity and mortality. Efficacy of vaccines and antivirals to treat human CCHFV infections remains limited and controversial. Research into pathology and underlying molecular mechanisms of CCHFV and other nairoviruses is limited. Significant progress has been made in our understanding of CCHFV replication and pathogenesis in the past decade. Here we review the most recent molecular advances in CCHFV-related research, and provide perspectives on future research.

Differential Use of the C-Type Lectins L-SIGN and DC-SIGN for Phlebovirus Endocytosis

Bunyaviruses represent a growing threat to humans and livestock globally. The receptors, cellular factors and endocytic pathways used by these emerging pathogens to infect cells remain largely unidentified and poorly characterized. DC-SIGN is a C-type lectin highly expressed on dermal dendritic cells that has been found to act as an authentic entry receptor for many phleboviruses (Bunyaviridae), including Rift Valley fever virus (RVFV), Toscana virus (TOSV) and Uukuniemi virus (UUKV). We found that these phleboviruses can exploit another C-type lectin, L-SIGN, for infection. L-SIGN shares 77% sequence homology with DC-SIGN and is expressed on liver sinusoidal endothelial cells. L-SIGN is required for UUKV binding but not for virus internalization. An endocytosis-defective mutant of L-SIGN was still able to mediate virus uptake and infection, indicating that L-SIGN acts as an attachment receptor for phleboviruses rather than an endocytic receptor. Our results point out a fundamental difference in the use of the C-type lectins L-SIGN and DC-SIGN by UUKV to enter cells, although both proteins are closely related in terms of molecular structure and biological function. This study sheds new light on the molecular mechanisms by which phleboviruses target the liver and also highlights the added complexity in virus-receptor interactions beyond attachment.

Current situation of Crimean-Congo hemorrhagic fever in Southeastern Europe and neighboring countries: a public health risk for the European Union?

Crimean-Congo hemorrhagic fever (CCHF) is the most widespread tick-borne viral infection of humans, occurring across western China through southern Asia, Middle East, and Southeastern Europe (SEE) and in the most of African countries. CCHF virus is maintained through vertical and horizontal transmission in several genera of ticks, mainly in Hyalomma, which spreads the virus to a variety of wild and domestic mammals, which develop a transient viremia without signs of illness. Human infections occur through tick bite or exposure to the blood or other body fluids of an infected animal or of a CCHF patient. In SEE the number of clinical cases of CCHF as well as the areal of the infected ticks continuously rapidly increased after 2000. The aim of this study was to present actual situation of CCHF in SEE. Sources of information include published literature and personal unpublished data.

CONCLUSIONS

Based on: 1. Hyaloma's presence in Western EU countries, 2. Changes in climatic conditions and 3. Absence of an active vaccination against CCHF, it can be expected that this disease will continue to present real threat for human health in SEE and Southwestern Europe (SWE).

Analysis of the entry mechanism of Crimean-Congo hemorrhagic fever virus, using a vesicular stomatitis virus pseudotyping system

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease causing severe hemorrhagic symptoms with a nearly 30 % case-fatality rate in humans. The experimental use of CCHF virus (CCHFV), which causes CCHF, requires high-biosafety-level (BSL) containment. In contrast, pseudotyping of various viral glycoproteins (GPs) onto vesicular stomatitis virus (VSV) can be used in facilities with lower BSL containment, and this has facilitated studies on the viral entry mechanism and the measurement of neutralizing activity, especially for highly pathogenic viruses. In the present study, we generated high titers of pseudotyped VSV bearing the CCHFV envelope GP and analyzed the mechanisms involved in CCHFV infection. A partial deletion of the CCHFV GP cytoplasmic domain increased the titer of the pseudotyped VSV, the entry mechanism of which was dependent on the CCHFV envelope GP. Using the pseudotype virus, DC-SIGN (a calcium-dependent [C-type] lectin cell-surface molecule) was revealed to enhance viral infection and act as an entry factor for CCHFV.

Serum sTREM-1 level is quite higher in Crimean Congo Hemorrhagic Fever, a viral infection

Members of triggering receptor expressed on myeloid cells (TREM) family are known as immunmodulators in several infectious or noninfectious inflammatory disorders. The information about their role in viral infections is very limited. To enlighten if there is a relation between soluble TREM-1(sTREM-1) and a viral infection, Crimean Congo Haemorrhagic Fever (CCHF), we investigated the levels of sTREM-1 in the sera of 39 CCHF patients both at admission and at recovery and compared with 40 healthy controls by using microELISA technique. Statistical analysis was made by using Statistical Package for Social Sciences (SPSS) for Windows 20 programme. Value of P < 0.05 was accepted as significant for statistical analyses. Median sTREM-1 level was higher in CCHF group when compared to the control group (1,961 vs. 151.1 pg/ml, respectively; P < 0.001). In CCHF patients, sTREM-1 levels were significantly decreased at recovery compared to initial level measured at hospital admission (1,961 vs. 948 pg/ml, respectively; P = 0.019). ΔsTREM-1 is correlated with ΔCRP, ΔWBC, and ΔPlt. We found that serum levels of sTREM-1 higher than 405.9 pg/ml existed as a cut off point for differentiating CCHF patients and control group with a sensitivity of 94.9% and specifity of 87.5%. It is proved that sTREM-1 is increased and correlates with the clinical and laboratory findings in CCHF, a viral infection characterized by activation of inflammation. This finding may lead new studies to enlighten the pathogenesis of infections developing by activation of inflammatory cascades and high level cytokine releases, especially. J. Med. Virol. 88:1473-1478, 2016. © 2016 Wiley Periodicals, Inc.

Relationship between IFNA1, IFNA5, IFNA10, and IFNA17 gene polymorphisms and Crimean-Congo hemorrhagic fever prognosis in a Turkish population range

Crimean-Congo hemorrhagic fever (CCHF) is a fatal emerging acute viral infection. Not much is known regarding the pathogenic mechanisms and the reasons behind severe or mild disease courses in CCHF. IFN-alpha (IFNA) is one of the essential cytokines in the immune system. Existence of single nucleotide gene polymorphisms (SNPs) in cytokines can cause susceptibility or resistance to viral agents and different clinical courses. Hence, the relationship between SNPs in genes encoding cytokines (IFNA1 -1823G/A (rs1332190), IFNA5 -2529T/A (rs758236), IFNA10 Cys20stop (rs10119910), and IFNA17 Ile184Arg (rs9298814) SNPs and disease susceptibility were investigated. The associations between SNPs and CCHF prognosis were also studied. Total 150 patients with CCHF and 170 healthy individuals were enrolled. Genotyping was performed by PCR-RFLP methods. The frequency of IFNA1 -1823 (rs1332190) GG genotype was significantly higher in control subjects than CCHF patients (20% vs. 8%; P = 0.01). For IFNA17 Ile184Arg (rs9298814) polymorphism, CCHF patients having TG genotype had a higher frequency than the control subjects (38% vs. 32.4%; P = 0.039). The distribution of TT + TG genotype frequencies was also significantly higher in CCHF group than the controls (97.3% vs. 91.8%; P = 0.049). Genotype and allele frequencies for IFNA subtypes between fatal and survivors were the same (P > 0.05). Genotype and allele frequencies between severe and mild/moderate CCHF patients were also the same (P > 0.05). The results show that IFNA1 rs1332190 and IFNA17 rs9298814 SNPs may play an important role in CCHF susceptibility. Determining the existence of other connections for IFNA SNPs and CCHF severity and fatality requires further investigations.

Bunyaviruses: from transmission by arthropods to virus entry into the mammalian host first-target cells

The Bunyaviridae constitute a large family of animal RNA viruses distributed worldwide, most members of which are transmitted to vertebrate hosts by arthropods and can cause severe pathologies in humans and livestock. With an increasing number of outbreaks, arthropod-borne bunyaviruses (arbo-bunyaviruses) present a global threat to public health and agricultural productivity. Yet transmission, tropism, receptors and cell entry remain poorly characterized. The focus of this review is on the initial infection of mammalian hosts by arbo-bunyaviruses from cellular and molecular perspectives, with particular attention to the human host. We address current knowledge and advances regarding the identity of the first-target cells and the subsequent processes of entry and penetration into the cytosol. Aspects of the vector-to-host switch that influence the early steps of cell infection in mammalian skin, where incoming particles are introduced by infected arthropods, are also highlighted and discussed.

Antibodies to the core proteins of Nairobi sheep disease virus/Ganjam virus reveal details of the distribution of the proteins in infected cells and tissues

Nairobi sheep disease virus (NSDV; also called Ganjam virus in India) is a bunyavirus of the genus Nairovirus. It causes a haemorrhagic gastroenteritis in sheep and goats with mortality up to 90%. The virus is closely related to the human pathogen Crimean-Congo haemorrhagic fever virus (CCHFV). Little is currently known about the biology of NSDV. We have generated specific antibodies against the virus nucleocapsid protein (N) and polymerase (L) and used these to characterise NSDV in infected cells and to study its distribution during infection in a natural host. Due to its large size and the presence of a papain-like protease (the OTU-like domain) it has been suggested that the L protein of nairoviruses undergoes an autoproteolytic cleavage into polymerase and one or more accessory proteins. Specific antibodies which recognise either the N-terminus or the C-terminus of the NSDV L protein showed no evidence of L protein cleavage in NSDV-infected cells. Using the specific anti-N and anti-L antibodies, it was found that these viral proteins do not fully colocalise in infected cells; the N protein accumulated near the Golgi at early stages of infection while the L protein was distributed throughout the cytoplasm, further supporting the multifunctional nature of the L protein. These antibodies also allowed us to gain information about the organs and cell types targeted by the virus in vivo. We could detect NSDV in cryosections prepared from various tissues collected post-mortem from experimentally inoculated animals; the virus was found in the mucosal lining of the small and large intestine, in the lungs, and in mesenteric lymph nodes (MLN), where NSDV appeared to target monocytes and/or macrophages.

Elevated chemokine levels during adult but not pediatric Crimean-Congo hemorrhagic fever

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral zoonosis. Clinical reports indicate the severity of CCHF is milder in children than adults. The chemokines are important chemo-attractant mediators of the host immune system.

OBJECTIVES

The main aim of the study was to identify whether or not there were any differences in chemokine levels between the pediatric and adult patients and control groups, and whether there was any correlation with disease severity.

STUDY DESIGN

The serum levels of select chemokines including chemokine (C-C) ligand 2 (CCL2), CCL3, CCL4, chemokine (C-X-C) ligand 8 (CXCL8), CXCL9, and granulocyte-colony stimulating factor (G-CSF) in 29 adult and 32 pediatric CCHF patients and in 35 healthy children and 40 healthy adult control groups were studied by flow cytometric bead immunoassay method.

RESULTS

Great variability was detected in the serum levels of the chemokines for both the adult and pediatric patients and controls. With the exception of G-CSF, the median serum levels of CCL2, CCL3, CCL4, CXCL8, and CXCL9 were found to be significantly higher in the adult patients compared to adult controls (2364.7 vs. 761 pg/ml; 714.1 vs. 75.2 pg/ml; 88.6 vs. 25.5 pg/ml; 217.9 vs. 18.3 pg/ml; 875 vs. 352.2 pg/ml, respectively, p < 0.0001 for all comparisons). Among the chemokines the median CCL4 and G-CSF levels were significantly higher in the pediatric patients compared to pediatric controls (40.3 vs. 7.1 pg/ml, p < 0.0001; 0.1 vs. 0.1 pg/ml, p = 0.049, respectively).

CONCLUSION

The results of this study showed prominent chemokine raising in adult CCHF patients compared to children CCHF patients.

Recent advances in research on Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is an expanding tick-borne hemorrhagic disease with increasing human and animal health impact. Immense knowledge was gained over the past 10 years mainly due to advances in molecular biology, but also driven by an increased global interest in CCHFV as an emerging/re-emerging zoonotic pathogen. In the present article, we discuss the advances in research with focus on CCHF ecology, epidemiology, pathogenesis, diagnostics, prophylaxis and treatment. Despite tremendous achievements, future activities have to concentrate on the development of vaccines and antivirals/therapeutics to combat CCHF. Vector studies need to continue for better public and animal health preparedness and response. We conclude with a roadmap for future research priorities.

Some acute phase reactants and cholesterol levels in serum of patient with Crimean-Congo haemorrhagic fever

The purpose of this study is to determine erythrocyte sedimentation rate (ESR), C - reactive protein (CRP), serum amyloid-A (SAA) and cholesterol levels in patients with Crimean-Congo Hemorrhagic Fever (CCHF) and determine the relationship of these parameters with the severity of disease. By polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) method 40 patients were diagnosed as CCHF and 39 volunteer without any systemic disease whose blood were taken and their serum separated. SAA, CRP and ESR were measured with ELISA, nephelometry and Mix-Rate x100 vital diagnostic device, respectively, in serum samples. High density lipoprotein (HDL), low density lipoprotein (LDL) and total cholesterol levels were determined by using autoanalyzer HDL, LDL and total cholesterol kit (Syncron LX20). Statistically significant difference was determined between patients and controls in terms of the levels of SAA, CRP, HDL, LDL and total cholesterol (p<0.05). However, there was no significant difference between the groups in terms of the levels of ESR. In addition, neither SAA, CRP, ESR nor HDL, LDL and total cholesterol levels varied with the severity of disease in the cases assessed (p>0.05). Using of CRP and SAA together might increase the sensitivity of diagnosis of CCHF infection. However, none of the parameters investigated in this study were found to be a proper marker of the prognosis in CCHF. Cholesterol levels were significantly decreased in patients with CCHF, which was suggested to be associated with the increased serum levels of SAA in the patient group.

Crimean-Congo hemorrhagic fever: history, epidemiology, pathogenesis, clinical syndrome and genetic diversity

Crimean-Congo hemorrhagic fever (CCHF) is the most important tick-borne viral disease of humans, causing sporadic cases or outbreaks of severe illness across a huge geographic area, from western China to the Middle East and southeastern Europe and throughout most of Africa. CCHFV is maintained in vertical and horizontal transmission cycles involving ixodid ticks and a variety of wild and domestic vertebrates, which do not show signs of illness. The virus circulates in a number of tick genera, but Hyalomma ticks are the principal source of human infection, probably because both immature and adult forms actively seek hosts for the blood meals required at each stage of maturation. CCHF occurs most frequently among agricultural workers following the bite of an infected tick, and to a lesser extent among slaughterhouse workers exposed to the blood and tissues of infected livestock and medical personnel through contact with the body fluids of infected patients. CCHFV is the most genetically diverse of the arboviruses, with nucleotide sequence differences among isolates ranging from 20% for the viral S segment to 31% for the M segment. Viruses with diverse sequences can be found within the same geographic area, while closely related viruses have been isolated in far distant regions, suggesting that widespread dispersion of CCHFV has occurred at times in the past, possibly by ticks carried on migratory birds or through the international livestock trade. Reassortment among genome segments during co-infection of ticks or vertebrates appears to have played an important role in generating diversity, and represents a potential future source of novel viruses. In this article, we first review current knowledge of CCHFV, summarizing its molecular biology, maintenance and transmission, epidemiology and geographic range. We also include an extensive discussion of CCHFV genetic diversity, including maps of the range of the virus with superimposed phylogenetic trees. We then review the features of CCHF, including the clinical syndrome, diagnosis, treatment, pathogenesis, vaccine development and laboratory animal models of CCHF. The paper ends with a discussion of the possible future geographic range of the virus. For the benefit of researchers, we include a Supplementary Table listing all published reports of CCHF cases and outbreaks in the English-language literature, plus some principal articles in other languages, with total case numbers, case fatality rates and all CCHFV strains on GenBank.

Ganjam virus/Nairobi sheep disease virus induces a pro-inflammatory response in infected sheep

Partly due to climate change, and partly due to changes of human habitat occupation, the impact of tick-borne viruses is increasing. Nairobi sheep disease virus (NSDV) and Ganjam virus (GV) are two names for the same virus, which causes disease in sheep and goats and is currently known to be circulating in India and East Africa. The virus is transmitted by ixodid ticks and causes a severe hemorrhagic disease. We have developed a real-time PCR assay for the virus genome and validated it in a pilot study of the pathogenicity induced by two different isolates of NSDV/GV. One isolate was highly adapted to tissue culture, grew in most cell lines tested, and was essentially apathogenic in sheep. The second isolate appeared to be poorly adapted to cell culture and retained pathogenicity in sheep. The real-time PCR assay for virus easily detected 4 copies or less of the viral genome, and allowed a quantitative measure of the virus in whole blood. Measurement of the changes in cytokine mRNAs showed similar changes to those observed in humans infected by the closely related virus Crimean Congo hemorrhagic fever virus.

Application of the pseudo-plaque assay for detection and titration of Crimean-Congo hemorrhagic fever virus

A pseudo-plaque assay was developed for detection and quantitation of Crimean-Congo hemorrhagic fever virus Turkey-Kelkit06. Enzyme-catalyzed color development of infected cells probed with anti-Crimean-Congo hemorrhagic fever virus antibodies was used for determining the titer of Crimean-Congo hemorrhagic fever Turkey-Kelkit06 and for its detection in samples from persons infected with the Crimean-Congo hemorrhagic fever virus. The pseudo-plaque assay accuracy was confirmed by comparing pseudo-plaque assay titers with fluorescent immunofocus assay and focus formation assay titers using three stocks of virus. No significant difference in virus titers of Crimean-Congo hemorrhagic fever Turkey-Kelkit06 among the three methods was observed. The pseudo-plaque assay is more sensitive than the fluorescent immunofocus assay for detecting the virus in primary isolates of Crimean-Congo hemorrhagic fever virus collected from humans, but no difference in sensitivity between the two methods was observed in the cell-adapted strain of Crimean-Congo hemorrhagic fever Turkey-Kelkit06. The pseudo-plaque assay is suitable for titration of Crimean-Congo hemorrhagic fever Turkey-Kelkit06, which does not develop plaques, suggesting it may also be suitable for the detection of other viruses.

Crimean-Congo hemorrhagic fever virus-infected hepatocytes induce ER-stress and apoptosis crosstalk

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed tick-borne member of the Nairovirus genus (Bunyaviridae) with a high mortality rate in humans. CCHFV induces a severe disease in infected patients that includes, among other symptoms, massive liver necrosis and failure. The interaction between liver cells and CCHFV is therefore important for understanding the pathogenesis of this disease. Here, we described the in vitro CCHFV-infection and -replication in the hepatocyte cell line, Huh7, and the induced cellular and molecular response modulation. We found that CCHFV was able to infect and replicate to high titres and to induce a cytopathic effect (CPE). We also observed by flow cytometry and real time quantitative RT-PCR evidence of apoptosis, with the participation of the mitochondrial pathway. On the other hand, we showed that the replication of CCHFV in hepatocytes was able to interfere with the death receptor pathway of apoptosis. Furthermore, we found in CCHFV-infected cells the over-expression of PUMA, Noxa and CHOP suggesting the crosstalk between the ER-stress and mitochondrial apoptosis. By ELISA, we observed an increase of IL-8 in response to viral replication; however apoptosis was shown to be independent from IL-8 secretion. When we compared the induced cellular response between CCHFV and DUGV, a mild or non-pathogenic Nairovirus for humans, we found that the most striking difference was the absence of CPE and apoptosis. Despite the XBP1 splicing and PERK gene expression induced by DUGV, no ER-stress and apoptosis crosstalk was observed. Overall, these results suggest that CCHFV is able to induce ER-stress, activate inflammatory mediators and modulate both mitochondrial and death receptor pathways of apoptosis in hepatocyte cells, which may, in part, explain the role of the liver in the pathogenesis of CCHFV.

DC-SIGN as a receptor for phleboviruses

During natural transmission, bunyaviruses are introduced into the skin through arthropod bites, and dermal dendritic cells (DCs) are the first to encounter incoming viruses. DC-SIGN is a C-type lectin highly expressed on the surface of dermal DCs. We found that several arthropod-borne phleboviruses (Bunyaviridae), including Rift Valley fever and Uukuniemi viruses, exploit DC-SIGN to infect DCs and other DC-SIGN-expressing cells. DC-SIGN binds the virus directly via interactions with high-mannose N-glycans on the viral glycoproteins and is required for virus internalization and infection. In live cells, virus-induced clustering of cell surface DC-SIGN could be visualized. An endocytosis-defective mutant of DC-SIGN was unable to mediate virus uptake, indicating that DC-SIGN is an authentic receptor required for both attachment and endocytosis. After internalization, viruses separated from DC-SIGN and underwent trafficking to late endosomes. Our study provides real-time visualization of virus-receptor interactions on the cell surface and establishes DC-SIGN as a phlebovirus entry receptor.

Rift Valley fever virus inhibits a pro-inflammatory response in experimentally infected human monocyte derived macrophages and a pro-inflammatory cytokine response may be associated with patient survival during natural infection

Rift Valley fever virus (RVFV) causes significant morbidity and mortality in humans and livestock throughout Africa and the Middle East. The clinical disease ranges from mild febrile illness, to hepatitis, retinitis, encephalitis and fatal hemorrhagic fever. RVFV NSs protein has previously been shown to interfere in vitro with the interferon response, and RVFV lacking the NSs protein is attenuated in several animal models. Monocytes and macrophages are key players in the innate immune response via expression of various cytokines and chemokines. Here we demonstrate that wild-type RVFV infection of human monocyte-derived macrophages leads to a productive infection and inhibition of the innate immune response via decreased expression of IFN-α2, IFN-β and TNF-α. Using a recombinant virus lacking the NSs protein, we show that this effect is mediated by the viral NSs protein. Finally, analysis of RVF patient samples demonstrated an association between a pro-inflammatory cytokine response and patient survival.

Crimean-Congo haemorrhagic fever: peritoneal and pleural effusion

In Crimean-Congo haemorrhagic fever (CCHF), haemorrhagic manifestations are usually petechiae and ecchymoses on mucous membranes and skin. Rarely, there is bleeding from the nose, gingiva, gastro-intestinal tract, genito-urinary tract, brain and lungs. A 13-year-old boy with CCHF presented with gastro-intestinal bleeding and developed peritoneal and pleural effusion. He made a complete recovery with supportive treatment and ribavirin, without requiring chest or peritoneal fluid drainage. To our knowledge, this is the first report of CCHF associated with peritoneal and pleural fluid.