Cytokine levels in Crimean-Congo hemorrhagic fever

Distinguishing host responses, extensive viral dissemination and long-term viral RNA persistence in domestic sheep experimentally infected with Crimean-Congo haemorrhagic fever virus Kosovo Hoti

Crimean-Congo haemorrhagic fever orthonairovirus (CCHFV) is a tick-borne, risk group 4 pathogen that often causes a severe haemorrhagic disease in humans (CCHF) with high case fatality rates. The virus is believed to be maintained in a tick-vertebrate-tick ecological cycle involving numerous wild and domestic animal species; however the biology of CCHFV infection in these animals remains poorly understood. Here, we experimentally infect domestic sheep with CCHFV Kosovo Hoti, a clinical isolate representing high pathogenicity to humans and increasingly utilized in current research. In the absence of prominent clinical signs, the infection leads to an acute viremia and coinciding viral shedding, fever and markers for potential impairment in liver and kidney functions. A number of host responses distinguish the subclinical infection in sheep versus fatal infection in humans. These include an early reduction of neutrophil recruitment and its chemoattractant, IL-8, in the blood stream of infected sheep, whereas neutrophil infiltration and elevated IL-8 are features of fatal CCHFV infections reported in immunodeficient mice and humans. Several inflammatory cytokines that correlate with poor disease outcomes in humans and have potential to cause vascular dysfunction, a primary hallmark of severe CCHF, are down-regulated or restricted from increasing in sheep. Of particular interest, the detection of CCHFV RNA (including full-length genome) in a variety of sheep tissues long after the acute phase of infection indicates a widespread viral dissemination in the host and suggests a potentially long-term persisting impact of CCHFV infection. These findings reveal previously unrecognized aspects of CCHFV biology in animals.

Can we predict bleeding at admission in Crimean-Congo hemorrhagic fever?

BACKGROUND

In Crimean-Congo hemorrhagic fever, bleeding has a significant impact on the prognosis of the disease. In our study, we aimed to identify independent risk factors for the development of bleeding in Crimean-Congo hemorrhagic fever and to contribute to the management of the disease.

METHODS

Cases with a definitive diagnosis of Crimean-Congo hemorrhagic fever were divided into two groups: those who developed bleeding and those who did not. Demographic, clinical and laboratory parameters were subjected to logistic regression analysis in terms of risk factors for bleeding development. Cut-off values for numerical variables were determined by receiver operating characteristics.

RESULTS

A total of 74 patients diagnosed with CCHF were included in the study. Bleeding occurred in at least one defined focus in 21 patients. In the multivariate logistic regression model, procalcitonin, days from symptom onset to admission, platelet count, and d-dimer were identified as independent risk factors for bleeding development. Procalcitonin had the most significant effect, with an approximately 5.3-fold increase in bleeding risk for each unit increase in its level. For discriminate bleeding, LDH and ferritin exhibited the highest sensitivity, while procalcitonin showed the highest specificity.

CONCLUSION

This study demonstrates the potential use of specific clinical and laboratory variables to predict bleeding development in CCHF patients. Procalcitonin elevation and the time from symptom onset to hospital admission have a significant effect in predicting bleeding.

Recent Advances in Crimean-Congo Hemorrhagic Fever Virus Detection, Treatment, and Vaccination: Overview of Current Status and Challenges

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus, and zoonosis, and affects large regions of Asia, Southwestern and Southeastern Europe, and Africa. CCHFV can produce symptoms, including no specific clinical symptoms, mild to severe clinical symptoms, or deadly infections. Virus isolation attempts, antigen-capture enzyme-linked immunosorbent assay (ELISA), and reverse transcription polymerase chain reaction (RT-PCR) are all possible diagnostic tests for CCHFV. Furthermore, an efficient, quick, and cheap technology, including biosensors, must be designed and developed to detect CCHFV. The goal of this article is to offer an overview of modern laboratory tests available as well as other innovative detection methods such as biosensors for CCHFV, as well as the benefits and limits of the assays. Furthermore, confirmed cases of CCHF are managed with symptomatic assistance and general supportive care. This study examined the various treatment modalities, as well as their respective limitations and developments, including immunotherapy and antivirals. Recent biotechnology advancements and the availability of suitable animal models have accelerated the development of CCHF vaccines by a substantial margin. We examined a range of potential vaccines for CCHF in this research, comprising nucleic acid, viral particles, inactivated, and multi-epitope vaccines, as well as the present obstacles and developments in this field. Thus, the purpose of this review is to present a comprehensive summary of the endeavors dedicated to advancing various diagnostic, therapeutic, and preventive strategies for CCHF infection in anticipation of forthcoming hazards.

Replicon particle vaccination induces non-neutralizing anti-nucleoprotein antibody-mediated control of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) can cause severe human disease and is considered a WHO priority pathogen due to the lack of efficacious vaccines and antivirals. A CCHF virus replicon particle (VRP) has previously shown protective efficacy in a lethal Ifnar-/- mouse model when administered as a single dose at least 3 days prior to challenge. Here, we determine that non-specific immune responses are not sufficient to confer short-term protection, since Lassa virus VRP vaccination 3 days prior to CCHFV challenge was not protective. We also investigate how CCHF VRP vaccination confers protective efficacy by examining viral kinetics, histopathology, clinical analytes and immunity early after challenge (3 and 6 days post infection) and compare to unvaccinated controls. We characterize how these effects differ based on vaccination period and correspond to previously reported CCHF VRP-mediated protection. Vaccinating Ifnar-/- mice with CCHF VRP 28, 14, 7, or 3 days prior to challenge, all known to confer complete protection, significantly reduced CCHFV viral load, mucosal shedding, and markers of clinical disease, with greater reductions associated with longer vaccination periods. Interestingly, there were no significant differences in innate immune responses, T cell activation, or antibody titers after challenge between groups of mice vaccinated a week or more before challenge, but higher anti-NP antibody avidity and effector function (ADCD) were positively associated with longer vaccination periods. These findings support the importance of antibody-mediated responses in VRP vaccine-mediated protection against CCHFV infection.

IL-36 signaling pathway dysregulation in Crimean-Congo hemorrhagic fever virus patients: A potential therapeutic avenue

Crimean-Congo hemorrhagic fever (CCHF) is a severe viral disease. The scientific literature is growing, emphasizing the significance of the interleukin (IL)-36 family in the proinflammatory signaling pathway. However, to date, no research has explored the potential of IL-36 family members as biomarkers in CCHF. This study aims to bridge this gap by evaluating IL-36α, IL-36β, and IL-36γ levels in CCHF patients and healthy controls and investigating their association with disease severity and prognosis. Sixty confirmed CCHF patients and 29 healthy controls were enrolled in this case-control study. Serum levels of IL-36α, IL-36β, and IL-36γ were measured using enzyme-linked immunosorbent assays. Significantly higher levels of IL-36α and IL-36β were observed in CCHF patients compared to healthy controls (p < 0.05). However, no statistically significant changes were found in IL-36γ levels between the two groups. Among the CCHF patients, those who did not survive exhibited significantly elevated IL-36α and IL-36γ levels compared to survivors (p < 0.01). Positive correlations were identified between IL-36α and IL-36γ levels with activated partial thromboplastin time, and D-dimer (p < 0.01). Conversely, platelet levels showed a negative correlation with IL-36α and IL-36γ levels (p < 0.01). The increased levels of IL-36α, IL-36β, and IL-36γ in patients indicate their participation in proinflammatory reactions in CCHF patients. Understanding the role of IL-36 family members in CCHF pathogenesis could offer valuable insights into disease progression and facilitate the development of targeted therapeutic strategies.

CD8+ T-cells target the Crimean-Congo haemorrhagic fever virus Gc protein to control the infection in wild-type mice

BACKGROUND

Crimean-Congo haemorrhagic fever (CCHF) is a serious viral hemorrhagic fever caused by the CCHF virus (CCHFV). Spread by the bites of infected ticks or handling of viremic livestock, human disease is characterized by a non-specific febrile illness that can rapidly progress to fatal hemorrhagic disease. No vaccines or antivirals are available. Case fatality rates can vary but can be higher than 30%, although sub-clinical infections are often unrecognized and unreported. Yet, while most humans infected with CCHFV will survive the infection, often with little-to-no symptoms, the host responses that control the infection are unknown.

METHODS

Here we investigated the role of cellular immunity in control of CCHFV infection in an immunocompetent mouse model.

FINDINGS

We found that CD8+ T-cells are crucial for efficient control of the acute infection and rapidly acquired CCHFV-specific antiviral effector functions such as production of antiviral cytokines and degranulating in response to CCHFV peptides. We further identified the minimal CD8+ T-cell epitopes in the viral Gc proteins and that infection of mice lacking IFNγ resulted in worsened disease and higher viral loads.

INTERPRETATION

Together our data suggest that CD8+ T-cells are important for control of acute CCHFV infection likely through production of antiviral cytokines.

FUNDING

This work was supported by the Intramural Research Program of the NIH.

Favipiravir and Ribavirin protect immunocompetent mice from lethal CCHFV infection

Crimean-Congo hemorrhagic fever virus (CCHFV) causes Crimean-Congo hemorrhagic fever (CCHF) in humans with high morbidity and mortality. Currently, there is neither an approved antiviral drug nor a vaccine against CCHFV. In this study, we describe a lethal model of CCHFV infection using a mouse-adapted strain of CCHFV (MA-CCHFV) in adult wild-type male mice. Infected mice developed high viral loads, tissue pathology, and inflammatory immune responses before ultimately succumbing to the infection. We used the model to evaluate the protective efficacy of nucleoside analogs monulpiravir, favipiravir, ribavirin, the antibiotic tigecycline and the corticosteroids dexamethasone and methylprednisolone against lethal CCHFV infection. Tigecycline, monulpiravir and the corticosteroids failed to protect mice from lethal MA-CCHFV infection. In contrast, favipiravir and ribavirin protected animals from clinical disease and death even when treatment was delayed. Despite demonstrating uniform protection, CCHFV RNA persisted in survivors treated with favipiravir and ribavirin. Nevertheless, the study demonstrated the anti-CCHFV efficacy of favipiravir and ribavirin in a model with intact innate immunity and establishes this model for continued development of CCHFV countermeasures.

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: An Emerging Viral Infection in India, Revisited and Lessons Learned

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic disease caused by the CCHF virus. It was first recognized in 1944 in the Crimea region of the former Soviet Union and then was subsequently isolated in Congo, from a child with similar symptoms. Hence, the virus was termed the Crimean-Congo hemorrhagic fever virus. CCHF is an emerging disease with more than 1000 human cases being reported every year from South-Eastern Europe and Western Asia. The disease is endemic in Africa, the Balkans, the Middle East, and Asia, with an estimated 10,000 to 15,000 CCHF infections each year. The geographic range of the CCHF virus is most extensive among the tick-borne viruses that infect humans. The first outbreak of CCHF in India was described in 2011 in the state of Gujarat with four cases being reported. Since then, there have been sporadic cases in India occurring in small clusters with community and nosocomial spread. Here, we describe three cases that were treated at a tertiary care teaching hospital in the Gujarat state of India. All of them had nonspecific symptoms of viremia initially, followed by rapid deterioration of the general condition. Two of the three patients died. Because of its resemblance with other hemorrhagic fevers, diagnosis of CCHF remains a challenge, especially in non-endemic areas. We aim to sensitize the readers to this emerging arboviral disease because the virus is highly infectious and carries high mortality, and hence, it is crucial to suspect and diagnose the index case at the earliest.

Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever (CCHF) is a severe tick-borne illness with a wide geographical distribution and case fatality rates of 30% or higher. Caused by infection with the CCHF virus (CCHFV), cases are reported throughout Africa, the Middle East, Asia and southern and eastern Europe. The expanding range of the Hyalomma tick vector is placing new populations at risk for CCHF, and no licensed vaccines or specific antivirals exist to treat CCHF. Furthermore, despite cases of CCHF being reported annually, the host and viral determinants of CCHFV pathogenesis are poorly understood. CCHFV can productively infect a multitude of animal species, yet only humans develop a severe illness. Within human populations, subclinical infections are underappreciated and may represent a substantial proportion of clinical outcomes. Compared with other members of the Bunyavirales order, CCHFV has a more complex genomic organization, with many viral proteins having unclear functions in viral pathogenesis. In recent years, improved animal models have led to increased insights into CCHFV pathogenesis, and several antivirals and vaccines for CCHFV have shown robust efficacy in preclinical models. Translation of these insights and candidate therapeutics to the clinic will hopefully reduce the morbidity and mortality caused by CCHFV.

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.

Changing Disease Course of Crimean-Congo Hemorrhagic Fever in Children, Turkey

Crimean-Congo hemorrhagic fever (CCHF), endemic in certain regions of the world, is listed as a priority disease with pandemic potential. Since CCHF was first identified in Turkey, children have been known to experience milder disease than adults. However, during the COVID-19 pandemic, we observed an unusually severe disease course, including hemophagocytic lymphohistiocytosis (HLH). We examined cytokine/chemokine profiles of 9/12 case-patients compared with healthy controls at 3 time intervals. Interferon pathway-related cytokines/chemokines, including interleukin (IL) 18, macrophage inflammatory protein 3α, and IL-33, were elevated, but tumor necrosis factor-α, IL-6, CXCL8 (formerly IL-8), and cytokines acting through C-C chemokine receptor 2 and CCR5 were lower among case-patients than controls. Interferon pathway activation and cytokines/chemokines acting through CCR2 and CCR5 improved health results among children with severe CCHF. Children can experience severe CCHF, including HLH, and HLH secondary to CCHF can be successfully treated with intravenous immunoglobulin and steroid therapy.

The host inflammatory response contributes to disease severity in Crimean-Congo hemorrhagic fever virus infected mice

Crimean-Congo hemorrhagic fever virus (CCHFV) is an important human pathogen. In cell culture, CCHFV is sensed by the cytoplasmic RNA sensor retinoic acid-inducible gene I (RIG-I) molecule and its adaptor molecule mitochondrial antiviral signaling (MAVS) protein. MAVS initiates both type I interferon (IFN-I) and proinflammatory responses. Here, we studied the role MAVS plays in CCHFV infection in mice in both the presence and absence of IFN-I activity. MAVS-deficient mice were not susceptible to CCHFV infection when IFN-I signaling was active and showed no signs of disease. When IFN-I signaling was blocked by antibody, MAVS-deficient mice lost significant weight, but were uniformly protected from lethal disease, whereas all control mice succumbed to infection. Cytokine activity in the infected MAVS-deficient mice was markedly blunted. Subsequent investigation revealed that CCHFV infected mice lacking TNF-α receptor signaling (TNFA-R-deficient), but not IL-6 or IL-1 activity, had more limited liver injury and were largely protected from lethal outcomes. Treatment of mice with an anti-TNF-α neutralizing antibody also conferred partial protection in a post-virus exposure setting. Additionally, we found that a disease causing, but non-lethal strain of CCHFV produced more blunted inflammatory cytokine responses compared to a lethal strain in mice. Our work reveals that MAVS activation and cytokine production both contribute to CCHFV pathogenesis, potentially identifying new therapeutic targets to treat this disease.

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.

Immune responses in multiple hosts to Nucleocapsid Protein (NP) of Crimean-Congo Hemorrhagic Fever Virus (CCHFV)

In 2019, the World Health Organization declared 3 billion to be at risk of developing Crimean Congo Hemorrhagic Fever (CCHF). The causative agent of this deadly infection is CCHFV. The data related to the biology and immunology of CCHFV are rather scarce. Due to its indispensable roles in the viral life cycle, NP becomes a logical target for detailed viral immunology studies. In this study, humoral immunity to NP was investigated in CCHF survivors, as well as in immunized mice and rabbits. Abundant antibody response against NP was demonstrated both during natural infection in humans and following experimental immunizations in mice and rabbits. Also, cellular immune responses to recombinant NP (rNP) was detected in multispecies. This study represents the most comprehensive investigation on NP as an inducer of both humoral and cellular immunity in multiple hosts and proves that rNP is an excellent candidate warranting further immunological studies specifically on vaccine investigations.

Crimean Congo Hemorrhagic Fever Virus (CCHFV) is the most lethal human pathogen of medical importance after the dengue virus among arboviruses. The increasing geographic spread of Hyalomma ticks, which are responsible for viral transmission widespread, threatens billions of people. WHO currently declares the field of research on CCHFV as the second most urgently needed areas of investigations on emerging pathogens. About 10 to 40% of those infected with the virus lose their life due to the rapidly developing severe clinical manifestations. Pandemic potential and the lack of any approved treatment or vaccine make raise the studies on CCHFV as critical. The studies on CCHFV are challenging due to the necessities of BSL-4 facilities and the immunological characterization of individual structural proteins will lay the groundwork for the steps to be taken to treat and prevent this emerging disease. As is known from other RNA viruses, nucleoprotein (NP) has crucial roles in the viral life cycle, both in viral replication and transcription and in the formation of the virion structure. So far, detailed and comprehensive immunological characterizations on NP in multiple are not undertaken. Our study was set out to embark such detailed investigation. The strong humoral and cellular immune response to NP demonstrated by this study indicates that NP might be an excellent candidate for future scrutinies on vaccines and diagnostic reagents.

Host response transcriptomic analysis of Crimean-Congo hemorrhagic fever pathogenesis in the cynomolgus macaque model

Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly pathogenic tick-borne RNA virus prevalent in Asia, Europe, and Africa, and can cause a hemorrhagic disease (CCHF) in humans with mortality rates as high as 60%. A general lack of both effective medical countermeasures and a comprehensive understanding of disease pathogenesis is partly driven by an historical lack of viable CCHF animal models. Recently, a cynomolgous macaque model of CCHF disease was developed. Here, we document the targeted transcriptomic response of non-human primates (NHP) to two different CCHFV strains; Afghan09-2990 and Kosova Hoti that both yielded a mild CCHF disease state. We utilized a targeted gene panel to elucidate the transcriptomic changes occurring in NHP whole blood during CCHFV infection; a first for any primate species. We show numerous upregulated genes starting at 1 day post-challenge through 14 days post-challenge. Early gene changes fell predominantly in the interferon stimulated gene family with later gene changes coinciding with an adaptive immune response to the virus. There are subtle differences between viral strains, namely duration of the differentially expressed gene response and biological pathways enriched. After recovery, NHPs showed no lasting transcriptomic changes at the end of sample collection.

Sequential determination of viral load, humoral responses and phylogenetic analysis in fatal and non-fatal cases of Crimean-Congo hemorrhagic fever patients from Gujarat, India, 2019

Background

Thirty-four CCHF cases (17 fatal; 17 survived) were confirmed from Gujarat state, India during the year 2019. We aimed to find out the viral load, antibody kinetics, cytokine profile and phylogenetic analysis between fatal and non- fatal cases.

Methods

Thirty four cases were included in this study. Blood and urine samples were collected from all the cases on the day of admission to hospital. Non-fatal cases were followed weekly for understanding the profile of viral kinetics, anti-CCHFV IgM and IgG antibodies. We also quantified the cytokines in both fatal and non-fatal cases. For epidemiological correlation, livestock were screened for anti-CCHF IgG antibodies and the tick pool specimens were tested by real time RT-PCR. Virus isolation was attempted on tick pools and human specimens and phylogenetic analysis performed on human and ticks complete genome sequences.

Results

CCHF cases were detected throughout year in 2019 with the peak in August. Out of 34 cases, eight secondary CCHF cases were reported. Cases were predominantly detected in males and in 19–45 years age group (55.88%). The persistence of viremia was observed till 76^th POD (post onset date) in one case whereas anti-CCHFV IgM and IgG was detected amongst these cases from the 2^nd and 20^th POD respectively. Positivity observed amongst livestock and tick pools were was 21.57% and 7.4% respectively. The cytokine analysis revealed a significant increase in the level of serum IL-6, IL-10 and IFN-γ during the acute phase of the infection, but interestingly IL-10 lowered to normal upon clearance of the virus in the clinically recovered case. Fatal cases had high viral RNA copy numbers. Bleeding from one or two mucosal sites was significantly associated with fatality (OR-16.47;p-0.0034 at 95% CI). We could do CCHF virus isolation from two cases. Phylogenetic analysis revealed circulation of re-assortment of Asian-West African genotypes in humans and ticks.

Conclusions

The persistence of CCHF viral RNA was detected till 76^th POD in one of the survivors. The circulation of a re-assortment Asian-West African genotype in a CCHF case is also reported first time from India.

Crimean Congo hemorrhagic fever is a zoonotic tick-borne viral hemorrhagic disease. This disease is reported from Europe, Mediterranean, north-western China, central Asia, Africa, and the Middle East. Several outbreaks of CCHF were reported from Gujarat and Rajasthan states, India from 2011 to 2019. In this study, we discuss the clinical, molecular, serological, and the cytokine data of 34 CCHF cases (17 fatal and 17 survived) which were detected from Gujarat state in the year 2019. A sequential weekly follow up of the CCHF survivors was performed to understand the viral kinetics and the antibody profile. Interestingly, the presence of persistence CCHF viral RNA was observed till 76^th POD in one of the survivors. To our knowledge, we are reporting this long term persistence of viremia for the first time. We also observed that the anti-CCHFV IgM detection in the serum samples starts as soon as 2^nd POD but anti-CCHFV IgG antibody could be detected in the majority of the cases only after the 28^th POD. The cytokine analysis revealed a significant increase in the level of serum IL-6, IL-10 and IFN-γ during the acute phase of the infection, but interestingly IL-10 lowered to normal upon clearance of the virus in the clinically recovered case. We did the phylogenetic analysis and concluded the circulation of the Asian-West African re-assortment genotype in humans, which has not been reported from India prior to this study.

T-Cells and Interferon Gamma Are Necessary for Survival Following Crimean-Congo Hemorrhagic Fever Virus Infection in Mice

Crimean-Congo hemorrhagic fever (CCHF) is a severe tick-borne febrile illness with wide geographic distribution. In humans, the disease follows infection by the Crimean-Congo hemorrhagic fever virus (CCHFV) and begins as flu-like symptoms that can rapidly progress to hemorrhaging and death. Case fatality rates can be as high as 30%. An important gap in our understanding of CCHF are the host immune responses necessary to control the infection. A better understanding of these responses is needed to direct therapeutic strategies to limit the often-severe morbidity and mortality seen in humans. In this report, we have utilized a mouse model in which mice develop severe disease but ultimately recover. T-cells were robustly activated, differentiated to produce antiviral cytokines, and were critical for survival following CCHFV infection. We further identified a key role for interferon gamma (IFNγ) in survival following CCHFV infection. These results significantly improve our understanding of the host adaptive immune response to severe CCHFV infection.

Purtscher-like Retinopathy Associated with Crimean-Congo Hemorrhagic Fever: A Case Report

PURPOSE

To describe retinal findings and spectral-domain optical coherence tomographic (SD-OCT) features of a patient with Crimean-Congo hemorrhagic fever (CCHF) presenting as Purtscher-like retinopathy.

CASE REPORT

A 70-year-old woman presented with the emerging bilateral blurring of vision. She had been diagnosed with CCHF one week ago and hospitalized in another hospital for treatment of disease. Fundoscopy of the patient revealed cotton-wool spots, retinal whitening areas, and few retinal hemorrhages in a Purtscher-like configuration in both eyes. Spectral-domain optical coherence tomography revealed inner retinal hyperreflectivity corresponding to the cotton-wool spots in both eyes, and also showed subretinal fluid in the left eye. Without any treatment retinal lesions and inner retinal hyperreflectivity on SD-OCT regressed within one month.

CONCLUSION

Crimean-Congo hemorrhagic fever is known to cause mild ocular disease, and may also cause Purtscher-like retinopathy. It is important to aware of the ocular findings of CCHF.

Immunocompetent mouse model for Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe tick-borne febrile illness with wide geographic distribution. CCHF is caused by infection with the Crimean-Congo hemorrhagic fever virus (CCHFV) and case fatality rates can be as high as 30%. Despite causing severe disease in humans, our understanding of the host and viral determinants of CCHFV pathogenesis are limited. A major limitation in the investigation of CCHF has been the lack of suitable small animal models. Wild-type mice are resistant to clinical isolates of CCHFV and consequently, mice must be deficient in type I interferon responses to study the more severe aspects of CCHFV. We report here a mouse-adapted variant of CCHFV that recapitulates in adult, immunocompetent mice the severe CCHF observed in humans. This mouse-adapted variant of CCHFV significantly improves our ability to study host and viral determinants of CCHFV-induced disease in a highly tractable mouse model.

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).

Characterization of a novel STAT 2 knock-out hamster model of Crimean-Congo hemorrhagic fever virus pathogenesis

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne pathogen causing a febrile illness in humans, which can progress to hemorrhagic manifestations, multi-organ failure, and death. Current mouse models of CCHFV infection reliably succumb to virus challenge but vary in their ability to reflect signs of disease similar to humans. In this study, we established a signal transducer and activator of transcription 2 (STAT2) knockout hamster model to expand the repertoire of animal models of CCHFV pathogenesis that can be used for therapeutic development. These hamsters demonstrated a systemic and lethal disease in response to infection. Hallmarks of human disease were observed including petechial rash, blood coagulation dysfunction, and various biochemistry and blood cell count abnormalities. Furthermore, we also demonstrated the utility of this model for anti-CCHFV therapeutic evaluation. The STAT2 knock-out hamster model of CCHFV infection may provide some further insights into clinical disease, viral pathogenesis, and pave the way for testing of potential drug and vaccine candidates.

Analysis of Pediatric Intensive Care Unit Admissions for Crimean–Congo Hemorrhagic Fever in Turkey

Objective The aim of this study was to determine the clinical characteristics, course of disease, and outcomes of patients admitted to our pediatric intensive care unit (PICU) for Crimean–Congo hemorrhagic fever (CCHF).

Methods Data of all patients with CCHF who were admitted to PICU during a 3-year period and whose diagnosis was confirmed by serological methods or polymerase chain reaction were retrospectively reviewed. Their presenting characteristics, treatments, and outcomes were extracted from the hospital's electronic database. Disease severity scoring was performed using the severity scoring index and severity grading score system.

Results The data of 22 of 123 patients with suspected CCHF who were admitted to PICU were evaluated. Among them, 68.2% were males and mean age of all patients was 13.4 ± 2.2 years. The average length of stay of 10 patients was >10 days. On average, 3.72 units of platelet suspension per patient was transfused. In the course of the disease, the highest laboratory values were reached on day 3 of admission.

Conclusion Poor CCHF outcome depends on thrombocytopenia severity, prolonged coagulation tests, high-liver enzyme levels, and disseminated intravascular coagulation. Poor outcomes can be avoided by CCHF awareness and preparedness, early diagnosis of the disease, and supportive treatment with appropriate fluid and blood product transfusion. Randomized controlled trials on prophylactic transfusion and ribavirin use are needed.

Fluorescent Crimean-Congo hemorrhagic fever virus illuminates tissue tropism patterns and identifies early mononuclear phagocytic cell targets in Ifnar-/- mice

Crimean-Congo hemorrhagic fever virus (CCHFV, order Bunyavirales, family Nairoviridae, genus Orthonairovirus) is the tick-borne etiological agent of Crimean-Congo hemorrhagic fever (CCHF) in humans. Animals are generally susceptible to CCHFV infection but refractory to disease. Small animal models are limited to interferon-deficient mice, that develop acute fatal disease following infection. Here, using a ZsGreen1- (ZsG) expressing reporter virus (CCHFV/ZsG), we examine tissue tropism and dissemination of virus in interferon-α/β receptor knock-out (Ifnar^-/-) mice. We demonstrate that CCHFV/ZsG retains in vivo pathogenicity comparable to wild-type virus. Interestingly, despite high levels of viral RNA in all organs assessed, 2 distribution patterns of infection were observed by both fluorescence and immunohistochemistry (IHC), corresponding to the permissiveness of organ tissues. To further investigate viral dissemination and to temporally define cellular targets of CCHFV in vivo, mice were serially euthanized at different stages of disease. Flow cytometry was used to characterize CCHFV-associated alterations in hematopoietic cell populations and to classify infected cells in the blood, lymph node, spleen, and liver. ZsG signal indicated that mononuclear phagocytic cells in the lymphatic tissues were early targets of infection; in late-stage infection, overall, the highest levels of signal were detected in the liver, and ZsG was found in both antigen-presenting and lymphocyte cell populations.

Human infection by tick-borne Crimean-Congo hemorrhagic fever virus (CCHFV) can result in severe disease with up to 30% case fatality rates. While CCHFV is known to be hepatotropic, the presence and implications of virus in other tissues are less clear. Furthermore, to date, early cellular targets of infection in a CCHFV disease model have not been investigated in detail. Here, using a recombinant reporter CCHFV expressing the fluorescent protein ZsGreen1 (ZsG; CCHFV/ZsG) in interferon-α/β receptor knock-out (Ifnar^-/-) mice, which develop acute fatal disease following infection, we investigate both cellular and tissue targets of infection. Importantly, we find that CCHFV/ZsG infection demonstrated comparable pathogenicity to wild-type virus in Ifnar^-/- mice. We used in situ visualization of fluorescent signal in tissues to assess viral dissemination throughout the course of infection, and found robust viral signal in reproductive tissues, previously unrecognized as sites of CCHFV infection. We also used flow cytometry to detect intracellular fluorescent signal, and identified initial target cells of CCHFV infection as macrophage and monocyte populations in lymphatic tissues. These findings support a central role of immune cells in early virus dissemination, and a need for further investigations into reproductive tract involvement in human CCHFV infection.

Characterization of Biomarker Levels in Crimean-Congo Hemorrhagic Fever and Hantavirus Fever with Renal Syndrome

Hemorrhagic fever with renal syndrome (HFRS) and Crimean-Congo hemorrhagic fever (CCHF) are important viral hemorrhagic fevers (VHF), especially in the Balkan region. Infections with Dobrava or Puumala orthohantavirus and Crimean-Congo hemorrhagic fever orthonairovirus can vary from a mild, nonspecific febrile illness, to a severe disease with a fatal outcome. The pathogenesis of both diseases is poorly understood, but it has been suggested that a host’s immune mechanism might influence the pathogenesis of the diseases and survival. The aim of our study is to characterize cytokine response in patients with VHF in association with the disease progression and viral load. Forty soluble mediators of the immune response, coagulation, and endothelial dysfunction were measured in acute serum samples in 100 HFRS patients and 70 CCHF patients. HFRS and CCHF patients had significantly increased levels of IL-6, IL-12p70, IP-10, INF-γ, TNF-α, GM-CSF, MCP-3, and MIP-1b in comparison to the control group. Interestingly, HFRS patients had higher concentrations of serum MIP-1α, MIP-1β, which promote activation of macrophages and NK cells. HFRS patients had increased concentrations of IFN-γ and TNF-α, while CCHF patients had significantly higher concentrations of IFN-α and IL-8. In both, CCHF and HFRS patients’ viral load significantly correlated with IP-10. Patients with fatal outcome had significantly elevated concentrations of IL-6, IFN-α2 and MIP-1α, while GRO-α, chemokine related to activation of neutrophils and basophils, was downregulated. Our study provided a comprehensive characterization of biomarkers released in the acute stages of CCHF and HFRS.

Animal Models for Crimean-Congo Hemorrhagic Fever Human Disease

Crimean-Congo hemorrhagic fever virus (CCHFV) is an important tick-borne human pathogen endemic throughout Asia, Africa and Europe. CCHFV is also an emerging virus, with recent outbreaks in Western Europe. CCHFV can infect a large number of wild and domesticated mammalian species and some avian species, however the virus does not cause severe disease in these animals, but can produce viremia. In humans, CCHFV infection can lead to a severe, life-threating disease characterized by hemodynamic instability, hepatic injury and neurological disorders, with a worldwide lethality rate of ~20-30%. The pathogenic mechanisms of CCHF are poorly understood, largely due to the dearth of animal models. However, several important animal models have been recently described, including novel murine models and a non-human primate model. In this review, we examine the current knowledge of CCHF-mediated pathogenesis and describe how animal models are helping elucidate the molecular and cellular determinants of disease. This information should serve as a reference for those interested in CCHFV animal models and their utility for evaluation of medical countermeasures (MCMs) and in the study of pathogenesis.

Diagnostic approaches for Crimean-Congo hemorrhagic fever virus

Introduction: Crimean-Congo hemorrhagic fever (CCHF) is a potentially severe tick-borne viral disease endemic in several regions of Europe, Africa, and Asia. Rapid and reliable diagnosis is essential for early initiation of patient's treatment and for prompt implementation of appropriate precaution and infection control measures to prevent further spread of the disease. Areas covered: A literature search was undertaken on available approaches for laboratory diagnosis of CCHF infections, and the advantages and limitations of the assays are discussed. Expert opinion: Given that the genetic variability among CCHFV strains is high, attention has to be paid on the molecular protocols to detect all currently known genetic lineages of the virus as the emergence of CCHFV strains belonging to various lineages in new environments is not unexpected. In severe cases, the antibody production may be delayed or absent. It is important that the laboratories involved in CCHFV diagnostics to run quality control assays. Standardized assays and point-of-care tests with high sensitivity and specificity are needed. It is expected that the application of next-generation sequencing will be a powerful tool for CCHF diagnostics. Awareness, preparedness, and surveillance are required for prompt detection of CCHF cases.

Identification of potential microRNA markers related to Crimean-Congo hemorrhagic fever disease

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease caused by the arbovirus Crimean-Congo hemorrhagic fever virus (CCHFV). The CCHFV has a single-stranded RNA genome of negative sense. MicroRNAs (miRNAs) are key players in virus-host interactions and viral pathogenesis. We investigated the miRNA gene expression profiles in patients with CCHF using microarray for the first time in the world. Microarray analysis was performed using mirBase Ver 21 (Agilent Technologies, Santa Clara, CA). All statistical analyses were performed across the case-control, fatal-control, and fatal-nonfatal case groups using Genespring (Ver 3.0). Fifteen miRNAs were statistical significant in patients with CCHF compared with the controls (5 were upregulated, 10 were downregulated). Seventy-five and sixty-six miRNAs are in fatal compared with control and nonfatal case, respectively (fold change ([FC] ≥50) were statistically significant. In this study, the target genes of important miRNAs were identified and Gene Ontology analyses were performed across all groups. As a result of this study, we propose that the detection of miRNAs in patients with CCHF will allow the determination of therapeutic targets in diseases. CCHF is an important public health problem that can often be fatal. In this study, we investigated miRNA expression in case-control, fatal-control, and fatal-nonfatal case groups. Significant miRNAs associated with fatality were detected in CCHF. This study will serve as a source of data for the development of an antagomir-based therapy against CCHF using miRNAs in the future.

Interleukin-6 and Tumor Growth Factor-β are Risk Factors for Idiopathic Epistaxis

Objective

To evaluate the serum levels of interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, tumor growth factor (TGF)-β, endothelin, and immunoglobulin (Ig)E in patients with idiopathic epistaxis, compared with healthy control individuals.

Methods

Serum levels of IL-6, IL-8, TNF-α, TGF-β, endothelin, and IgE were evaluated in 110 patients with idiopathic epistaxis and 100 healthy controls using the enzyme-linked immunosorbent assay (ELISA) technique.

Results

Serum levels of IL-6 (P <.001) and TGF-β (P = .001) were significantly increased in patients with idiopathic epistaxis, compared with controls. TNF-α serum levels were significantly increased in male patients, compared with female patients (P = .053). We observed decreased antihistamine levels and increased expression of TGF-β (P = .02) and TNF-α (P = .02), respectively.

Conclusions

IL-6 and TGF-β appear to participate in the pathogenesis of idiopathic epistaxis. TNF-α may be considered a risk factor for male patients in developing epistaxis. Antihistamines may inhibit angiogenesis by decreasing expression of TGF-β and increasing expression of TNF-α.

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.

Recent advances in understanding Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed hemorrhagic fever virus and the cause of hemorrhagic disease in Africa, Southern and Eastern Europe, the Middle East, India and Asia. Recent emergence of CCHFV into Spain indicates that the geographic range of this virus is expanding and the presence of its tick vector in several countries without reported disease suggest that CCHFV will continue to spread. Research into CCHFV was historically limited by a lack of suitable animal models and tools to study viral pathogenesis. However, in the past few years the toolset for studying CCHFV has expanded with small animal and non-human primate models for CCHFV being developed along with a reverse genetics system that allows for investigation of viral determinants of disease. These tools have been utilized to understand how CCHFV antagonizes host restriction factors and to develop novel vaccine candidates that may help limit the substantial morbidity and mortality in humans caused by CCHFV.

Exploring Crimean-Congo Hemorrhagic Fever Virus-Induced Hepatic Injury Using Antibody-Mediated Type I Interferon Blockade in Mice

Crimean-Congo hemorrhagic fever virus (CCHFV) can cause severe hepatic injury in humans. However, the mechanism(s) causing this damage is poorly characterized. CCHFV produces an acute disease, including liver damage, in mice lacking type I interferon (IFN-I) signaling due to either STAT-1 gene deletion or disruption of the IFN-I receptor 1 gene. Here, we explored CCHFV-induced liver pathogenesis in mice using an antibody to disrupt IFN-I signaling. When IFN-I blockade was induced within 24 h postexposure to CCHFV, mice developed severe disease with greater than 95% mortality by 6 days postexposure. In addition, we observed increased proinflammatory cytokines, chemoattractants, and liver enzymes in these mice. Extensive liver damage was evident by 4 days postexposure and was characterized by hepatocyte necrosis and the loss of CLEC4F-positive Kupffer cells. Similar experiments in CCHFV-exposed NOD-SCID-γ (NSG), Rag2-deficient, and perforin-deficient mice also demonstrated liver injury, suggesting that cytotoxic immune cells are dispensable for hepatic damage. Some apoptotic liver cells contained viral RNA, while other apoptotic liver cells were negative, suggesting that cell death occurred by both intrinsic and extrinsic mechanisms. Protein and transcriptional analysis of livers revealed that activation of tumor necrosis factor superfamily members occurred by day 4 postexposure, implicating these molecules as factors in liver cell death. These data provide insights into CCHFV-induced hepatic injury and demonstrate the utility of antibody-mediated IFN-I blockade in the study of CCHFV pathogenesis in mice.IMPORTANCE CCHFV is an important human pathogen that is both endemic and emerging throughout Asia, Africa, and Europe. A common feature of acute disease is liver injury ranging from mild to fulminant hepatic failure. The processes through which CCHFV induces severe liver injury are unclear, mostly due to the limitations of existing small-animal systems. The only small-animal model in which CCHFV consistently produces severe liver damage is mice lacking IFN-I signaling. In this study, we used antibody-mediated blockade of IFN-I signaling in mice to study CCHFV liver pathogenesis in various transgenic mouse systems. We found that liver injury did not depend on cytotoxic immune cells and observed extensive activation of death receptor signaling pathways in the liver during acute disease. Furthermore, acute CCHFV infection resulted in a nearly complete loss of Kupffer cells. Our model system provides insight into both the molecular and the cellular features of CCHFV hepatic injury.

Favipiravir (T-705) but not ribavirin is effective against two distinct strains of Crimean-Congo hemorrhagic fever virus in mice

Crimean-Congo hemorrhagic fever virus (CCHFV) is a cause of serious hemorrhagic disease in humans. Humans infected with CCHFV develop a non-specific febrile illness and then progress to the hemorrhagic phase where case fatality rates can be as high as 30%. Currently there is lack of vaccines and the recommended antiviral treatment, ribavirin, has inconsistent efficacy in both human and animal studies. In this study we developed a model of CCHFV infection in type I interferon deficient mice using the clinical CCHFV isolate strain Hoti. Mice infected with strain Hoti develop a progressively worsening and ultimately fatal disease. We utilized this model along with our established model using the prototypical CCHFV strain 10200 to evaluate treatment with ribavirin or the antiviral favipiravir. While ribavirin treatment was able to suppress viral loads at early time points it was ultimately unable to prevent development of terminal disease in mice infected with either strain of CCHFV. In contrast, favipiravir showed clinical benefit even when administered late in the clinical progression of CCHF. Interestingly, in a small subset of mice, late-onset of CCHF was observed after favipiravir treatment was stopped and persistence of viral RNA in favipiravir treated survivors was also seen. Nevertheless, favipiravir showed significant clinical benefit against two distinct strains of CCHFV suggesting it may be a potent antiviral for treatment of human CCHFV infections.

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.

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.

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.

MicroRNA expression profiles in patients with acute Crimean Congo hemorrhagic fever reveal possible adjustments to cellular pathways

Several viral diseases are associated with altered microRNA (miRNA) expression, which can provide vital information about how cellular pathways respond to infection. However, the miRNA profile of Crimean Congo Hemorrhagic Fever (CCHFV) infections are not known. To address this gap, we performed real-time PCR-based miRNA analysis in individuals with acute Crimean Congo Hemorrhagic Fever (CCHFV) infections, with the goal of identifying pathways that might be associated with this disease. Peripheral blood mononuclear cells were analysed in eight individuals with detectable viral RNA and compared to five healthy subjects. A total of 106 differentially expressed miRNAs were identified, of which 19 miRNAs were either fivefold prominently up- or down-regulation. Several miRNAs associated with cytokine expression, some of which were previously associated with Dengue and Hantavirus infections were revealed. Moreover, possible mechanisms related to secretion of adhesion molecules and viral escape from innate immunity were identified. Pathway enrichment analyses further revealed the putative involvement of TNF-alfa, TGF-beta, MAPK, WNT, and neurotrophin signaling pathways in disease pathogenesis. J. Med. Virol. 89:417-422, 2017. © 2016 Wiley Periodicals, Inc.

Prognostic factors, pathophysiology and novel biomarkers in Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a geographically widespread tick-borne zoonosis. The clinical spectrum of the illness varies from mild infection to severe disease and death. In severe cases, hemorrhagic manifestations develop, with fatality rates of 4-20%, depending on the geographic region and quality of the health care. Although vast majority of the CCHF cases were reported from Turkey, mortality rate is lower than the other regions, which is 5% on average. Prediction of the clinical course of the disease enables appropriate management planning by the physician and prompt transportation, if needed, of the patient to a tertiary care hospital for an intensive therapy. Thus, predicting the outcome of the disease may avert potential mortality. There are numerous studies investigating the prognostic factors of CCHF in the literature. Majority of them were reported from Turkey and included investigations on clinical and biochemical parameters, severity scoring systems and some novel biomarkers. Somnolence, bleeding, thrombocytopenia, elevated liver enzymes and prolonged bleeding times are the most frequently reported prognostic factors to predict the clinical course of the disease earlier. High viral load seems to be the strongest predictor to make a clinical decision about the patient outcome. The severity scoring systems based on clinically important mortality-related parameters are especially useful for clinicians working in the field to predict the course of the disease and to decide which patient should be referred to a tertiary care hospital for intensive care. In the light of the pathophysiological characteristics of CCHF, some new biomarkers of prognosis including cytokines, soluble adhesion molecules, genetic polymorphisms and coagulopathy parameters were also investigated. However most of these tests are not available to clinicians and they were obtained mostly for research purposes. In spite of the various studies about prognostic factors, they have several inherent limitations, including large variability in the results and confusing data that are not useful for clinicians in routine practice. In this paper, the results of diverse studies of the prediction of the prognosis in CCHF based on epidemiological, clinical and laboratory findings of the disease were summarized and suggestions for future studies are provided.

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.

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).

Protective role of host aquaporin 6 against Hazara virus, a model for Crimean-Congo hemorrhagic fever virus infection

Crimean-Congo hemorrhagic fever virus (CCHFV) is an arthropod-borne pathogen that causes infectious disease with severe hemorrhagic manifestations in vascular system in humans. The proper function of the cells in the vascular system is critically regulated by aquaporins (AQP), water channels that facilitate fluxes of water and small solutes across membranes. With Hazara virus as a model for CCHFV, we investigated the effects of viruses on AQP6 and the impact of AQP6 on virus infectivity in host cells, using transiently expressed GFP-AQP6 cells, immunofluorescent assay for virus detection, epifluorescent imaging of living cells and confocal microscopy. In GFP-AQP6 expressing cells, Hazara virus reduced both the cellular and perinuclear AQP6 distribution and changed the cell area. Infection of human cell with CCHFV strain IbAR 10200 downregulated AQP6 expression at mRNA level. Interestingly, the overexpression of AQP6 in host cells decreased the infectivity of Hazara virus, speaking for a protective role of AQP6. We suggest the possibility for AQP6 being a novel player in the virus-host interactions, which may lead to less severe outcomes of an infection.

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.

Evaluation of Prognostic Values of Tissue Plasminogen Activator and Plasminogen Activator Inhibitor-1 in Crimean-Congo Hemorrhagic Fever Patients

Background:

Crimean-Congo hemorrhagic fever (CCHF) is a widespread disease in Turkey, and was responsible for many deaths in endemic regions during the last decade. The pathogenesis of the disease is not fully understood yet.

Objectives:

In this study we aimed to determine the levels of tissue plasminogen activator (tPA) and Plasminogen activator inhibitor-1 (PAI-1) as predictors of prognosis in CCHF.

Patients and Methods:

Patients who were diagnosed by the polymerase chain reaction (PCR) and IgM positivity in the reference laboratory were included in this study. Tissue Plasminogen activator and PAI-1 levels were measured by the enzyme linked immunosorbent assay (ELISA) using a commercial kit (human t-PA ELISA and human PAL-1 ELISA; BioVendor research and diagnostic products, BioVendor-Laboratorni medicina a.s., Brno, Czech Republic).

Results:

A total of 46 patients participated in this study. The significant differences between recovering patients and the patients who died, regarding Aspartate aminotransferase (AST), Creatine Phosphokinase (CPK), Lactate Dehydrogenase (LDH), Prothrombin Time (PT), activated Partial Thromboplastin time (aPTT), and thrombocyte and fibrinogen levels, were consistent with many clinical studies in the literature. The fatal cases were found to have higher tPA and PAI-1 levels in contrast to the patients who completely recovered.

Conclusions:

We think that these findings may help the progress of understanding of CCHF pathogenesis.

Health care response to CCHF in US soldier and nosocomial transmission to health care providers, Germany, 2009

Early recognition and implementation of appropriate infection control measures were effective in preventing further transmission.

In 2009, a lethal case of Crimean–Congo hemorrhagic fever (CCHF), acquired by a US soldier in Afghanistan, was treated at a medical center in Germany and resulted in nosocomial transmission to 2 health care providers (HCPs). After his arrival at the medical center (day 6 of illness) by aeromedical evacuation, the patient required repetitive bronchoscopies to control severe pulmonary hemorrhage and renal and hepatic dialysis for hepatorenal failure. After showing clinical improvement, the patient died suddenly on day 11 of illness from cerebellar tonsil herniation caused by cerebral/cerebellar edema. The 2 infected HCPs were among 16 HCPs who received ribavirin postexposure prophylaxis. The infected HCPs had mild or no CCHF symptoms. Transmission may have occurred during bag-valve-mask ventilation, breaches in personal protective equipment during resuscitations, or bronchoscopies generating infectious aerosols. This case highlights the critical care and infection control challenges presented by severe CCHF cases, including the need for experience with ribavirin treatment and postexposure prophylaxis.