Cryo-EM structure of glycoprotein C from Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a causative agent of serious hemorrhagic diseases in humans with high mortality rates. CCHFV glycoprotein Gc plays critical roles in mediating virus-host membrane fusion and has been studied extensively as an immunogen. However, the molecular mechanisms involved in membrane fusion and Gc-specific antibody-antigen interactions remain unresolved largely because structural information of this glycoprotein is missing. We designed a trimeric protein including most of the ectodomain region of Gc from the prototype CCHFV strain, IbAr10200, which enabled the cryo-electron microscopy structure to be solved at a resolution of 2.8 ?. The structure confirms that CCHFV Gc is a class II fusion protein. Unexpectedly, structural comparisons with other solved Gc trimers in the postfusion conformation revealed that CCHFV Gc adopted hybrid architectural features of the fusion loops from hantaviruses and domain III from phenuiviruses, suggesting a complex evolutionary pathway among these bunyaviruses. Antigenic sites on CCHFV Gc that protective neutralizing antibodies target were mapped onto the CCHFV Gc structure, providing valuable information that improved our understanding of potential neutralization mechanisms of various antibodies.     

Induction of caspase activation and cleavage of the viral nucleocapsid protein in different cell types during Crimean-Congo hemorrhagic fever virus infection

Regulation of apoptosis during infection has been observed for several viral pathogens. Programmed cell death and regulation of apoptosis in response to a viral infection are important factors for host or virus survival. It is not known whether Crimean-Congo hemorrhagic fever virus (CCHFV) infection regulates the apoptosis process in vitro. This study for the first time suggests that CCHFV induces apoptosis, which may be dependent on caspase-3 activation. This study also shows that the coding sequence of the S segment of CCHFV contains a proteolytic cleavage site, DEVD, which is conserved in all CCHFV strains. By using different recombinant expression systems and site-directed mutagenesis, we demonstrated that this motif is subject to caspase cleavage. We also demonstrate that CCHFV nucleocapsid protein (NP) is cleaved into a 30-kDa fragment at the same time as caspase activity is induced during infection. Using caspase inhibitors and cells lacking caspase-3, we clearly demonstrate that the cleavage of NP is caspase-3-dependent. We also show that the inhibition of apoptosis induced progeny viral titers of ～80-90%. Thus, caspase-3-dependent cleavage of NP may represent a host defense mechanism against lytic CCHFV infection. Taken together, these data suggest that the most abundant protein of CCHFV, which has several essential functions such as protection of viral RNA and participation in various processes in the replication cycle, can be subjected to cleavage by host cell caspases.     

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.     

A new strain of Crimean-Congo hemorrhagic fever virus isolated from Xinjiang,China

Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly pathogenic tick-borne virus with a fatality rate of up to 50% in humans. CCHFV is widely distributed in countries around the world. Outbreaks of CCHFV infection in humans have occurred in prior years in Xinjiang Province, China. Epidemiological surveys have detected CCHFV RNA in ticks and animals; however, few isolates were identified. In this study, we identified and isolated a new CCHFV strain from Hyalomma asiaticum asiaticum ticks collected from north of Tarim Basin in Xinjiang, China. A preliminary investigation of infection and antigens expression of CCHFV was performed in newborn mice. The target tissues for CCHFV replication in newborn mice were identified. The analysis of the phylogenetic relationships with other Chinese strains suggested that diverse genotypes of CCHFV have circulated in Xinjiang for years. These findings provide important insights into our understanding of CCHFV infection and evolution as well as disease prevention and control for local residents.

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Protective neutralizing antibodies from human survivors of Crimean-Congo hemorrhagic fever

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Role of cognitive parameters in dengue hemorrhagic fever and dengue shock syndrome

Dengue is becoming recognized as one of the most important vector-borne human diseases. It is predominant in tropical and subtropical zones but its geographical distribution is progressively expanding, making it an escalating global health problem of today. Dengue presents with spectrum of clinical manifestations, ranging from asymptomatic, undifferentiated mild fever, dengue fever (DF), to dengue hemorrhagic fever (DHF) with or without shock (DSS), a life-threatening illness characterized by plasma leakage due to increased vascular permeability. Currently, there are no antiviral modalities or vaccines available to treat and prevent dengue. Supportive care with close monitoring is the standard clinical practice. The mechanisms leading to DHF/DSS remains poorly understood. Multiple factors have been attributed to the pathological mechanism, but only a couple of these hypotheses are popular in scientific circles. The current discussion focuses on underappreciated factors, temperature, natural IgM, and endotoxin, which may be critical components playing roles in dengue pathogenesis.     

Epidemiology and Mutational Analysis of Global Strains of Crimean-Congo Haemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe illness with high fatality.Cases are reported in several countries in Africa,Europe,the Middle East,and Asia.Phylogenetic analyses based on the virus S (nucleocapsid),M (glycoprotein),and L (polymerase) genome segments sequences indicate distinct geographic lineages exist but their specific genetic characteristics require elucidation.In this work we collected all full length S segment sequences and generated a phylogenetic tree based on the alignment of these 62 samples.We then analyzed the alignment using entries from AAIndex,the Amino Acid Index database,to identify amino acid mutations that performed significant changes in charge,pka,hydropathy and side chain volume.Finally,we mapped these changes back to the tree and alignment to identify correlated mutations or sites that characterized a specific lineage.Based on this analysis we are able to propose a number of sites that appear to be important for virus function and which would be good candidates for experimental mutational analysis studies.     

Epidemiology and Mutational Analysis of Global Strains of Crimean-Congo Haemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe illness with high fatality.Cases are reported in several countries in Africa,Europe,the Middle East,and Asia.Phylogenetic analyses based on the virus S (nucleocapsid),M (glycoprotein),and L (polymerase) genome segments sequences indicate distinct geographic lineages exist but their specific genetic characteristics require elucidation.In this work we collected all full length S segment sequences and generated a phylogenetic tree based on the alignment of the...     

A mathematical model for Crimean-Congo haemorrhagic fever: tick-borne dynamics with conferred host immunity

Crimean-Congo haemorrhagic fever (CCHF) is a highly contagious tick-borne disease that impacts many countries in parts of Africa, Europe, Asia, and the Middle East. Outbreaks are episodic, but deadly. Due to the highly contagious nature of this disease, suspected cases are taken extremely serious, with very strong control measures implemented almost immediately. It is primarily those living on farms, livestock workers, and medical workers who are at risk. The virus responsible for CCHF is transmitted asymptomatically and transiently to livestock, and symptomatically to humans. The fatality rate in human cases can be very high. The number of methods and directions of viral transmission is large, including tick-to-tick, tick-to-livestock, tick-to-human, livestock-to-tick, livestock-to-human, and human-to-human. We model CCHF using a deterministic system of nonlinear differential equations. This compartment model allows us to analyse threshold parameters and equilibria describing the magnitude and progression of cases of the disease in a hypothetical outbreak.     

Interferon and cytokine responses to Crimean Congo hemorrhagic fever virus; an emerging and neglected viral zonoosis

Crimean Congo hemorrhagic fever virus (CCHFV) causes an acute disease with the potential of a fatal outcome. The virus is prevalent in about 30 countries. Clinical symptoms of infection commonly include fever, myalgia, and hemorrhages. Levels of liver enzymes are raised, and bleeding markers are often increased. A role of inflammatory cytokines in the pathogenesis has been suggested, and CCHFV employs a range of passive and active mechanisms to avoid induction of the antiviral type I interferons. Here, we review the most recent findings on the molecular pathogenesis and the interaction of CCHFV with the type I interferon and cytokine responses and discuss implications for pathogenesis.     

Crimean-Congo hemorrhagic fever in Rostov Province: the epidemiological characteristics of an outbreak

The results of the epidemiological analysis of the outbreak of hemorrhagic fever which was caused by Crimean-Congo hemorrhagic fever virus and occurred during the period of July 3-19, 1999, in the Oblivskaya district of Rostov Province are presented. The specific epidemiological features of the outbreak have been determined. The possible versions of the appearance of the focus of infection and the role of Ixodes ticks in the circulation of the infective agent are discussed.     

Congenital toxoplasmosis: An overview of the neurological and ocular manifestations

Toxoplasma gondii is an obligate intracellular parasite which is known to infect one-third of the total world population chronically though it is asymptomatic in immunocompetent patients. However, in an immunocompromised patient or an infected fetus, it may cause devastating effects. The parasite may cross the placenta of an infected pregnant woman and probably infect the fetus congenitally. The severity of the infection depends on the gestational age at which the infection has occurred i.e., if it has occurred in the early phase, the rate of transmission is low but the severity is high if the fetus is infected and if it has occurred in the later phase then transmission rate is higher while the severity would be low. Congenital toxoplasmosis may result in non-specific consequences like abortion, intra-uterine growth restriction, jaundice, hepatosplenomegaly or even intra-uterine death. It may also result in neurological or ocular manifestations like intracranial calcifications, hydrocephalus or retinochoroiditis. The diagnosis may be done by serological screening of anti-Toxoplasma antibodies (IgM and IgG) while PCR of the amniotic fluid or the placenta is the confirmatory test. Acute or chronic infections may be differentiated by IgG avidity tests. The treatment regimens include spiramycin to prevent congenital transmission from an infected mother, pyrimethamine, sulfadoxine and folinic acid to treat the infected fetus, CSF shunting for the treatment of hydrocephalus and a combination of pyrimethamine, azithromycin, and corticosteroids for treating ocular toxoplasmosis.     

An overview of the highly pathogenic H5N1 influenza virus

Since the first human case of H5N1 avian influenza virus infection was reported in 1997, this highly pathogenic virus has infected hundreds of people around the world and resulted in many deaths. The ability of H5N1 to cross species boundaries, and the presence of polymorphisms that enhance virulence, present challenges to developing clear strategies to prevent the pandemic spread of this highly pathogenic avian influenza (HPAI) virus. This review summarizes the current understanding of, and recent research on, the avian influenza H5N1 virus, including transmission, virulence, pathogenesis, clinical characteristics, treatment and prevention.     

An evaluation of the status of natural foci of Crimean-Congo hemorrhagic fever in the Crimea]

Parasitological data, the results of virological and serological investigations of materials, collected in nature and during the study of the immune structure of the population and indicative of the circulation of CCHF, virus in the Crimea and the possibility of human infection, are presented. The data on the spontaneous CCHF virus infection of 4 tick species belonging to the genus Ixodes have been confirmed, and evidence on the participation of Dermacentor marginatus in this process obtained for the first time in this region. The study has revealed for the first time that, besides European brown hares, scilly shrews, common voles and field mice may contribute to the maintenance of the natural foci of this infection. The low activity of the Crimean focus of CCHF may be the result of the intensive use of land, the widely spread stall-feeding of cattle, as well as a sharp decrease in the number of hares on the territories of hunting preserves.     

An assessment of the status of natural foci of Crimean-Congo hemorrhagic fever in the Crimea]

The parasitological data and the results of the virological and serological investigations of materials, collected in nature and in the course of study of the immune structure of the population, are indicative of the circulation of CHF virus in the Crimea and the possibility of human infection. Data on spontaneous infection of four species of Ixodes ticks with CHF virus have been confirmed, including the data, obtained for the first time for this region, on the participation of Dermacentor marginatus in this process. The study has revealed, also for the first time, that, together with European brown hares, the natural foci of this infection may be maintained by scilly shrews, common voles and European wood mice. Low activity of the Crimean focus may be the result of active land reclamation, keeping the cattle stalled in most of the stock-breeding farms of the region, as well as a sharp decline in the number of hares at the territories of hunting preserves.     

Epidemiology and mutational analysis of global strains of crimean-congo haemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe illness with high fatality. Cases are reported in several countries in Africa, Europe, the Middle East, and Asia. Phylogenetic analyses based on the virus S (nucleocapsid), M (glycoprotein), and L (polymerase) genome segments sequences indicate distinct geographic lineages exist but their specific genetic characteristics require elucidation. In this work we collected all full length S segment sequences and generated a phylogenetic tree based on the alignment of these 62 samples. We then analyzed the alignment using entries from AAIndex, the Amino Acid Index database, to identify amino acid mutations that performed significant changes in charge, pka, hydropathy and side chain volume. Finally, we mapped these changes back to the tree and alignment to identify correlated mutations or sites that characterized a specific lineage. Based on this analysis we are able to propose a number of sites that appear to be important for virus function and which would be good candidates for experimental mutational analysis studies.