Crimean-Congo hemorrhagic fever virus nucleoprotein reveals endonuclease activity in bunyaviruses

Crimean–Congo hemorrhagic fever virus (CCHFV), a virus with high mortality in humans, is a member of the genus Nairovirus in the family Bunyaviridae, and is a causative agent of severe hemorrhagic fever (HF). It is classified as a biosafety level 4 pathogen and a potential bioterrorism agent due to its aerosol infectivity and its ability to cause HF outbreaks with high case fatality (∼30%). However, little is known about the structural features and function of nucleoproteins (NPs) in the Bunyaviridae, especially in CCHFV. Here we report a 2.3-Å resolution crystal structure of the CCHFV nucleoprotein. The protein has a racket-shaped overall structure with distinct “head” and “stalk” domains and differs significantly with NPs reported so far from other negative-sense single-stranded RNA viruses. Furthermore, CCHFV NP shows a distinct metal-dependent DNA-specific endonuclease activity. Single residue mutations in the predicted active site resulted in a significant reduction in the observed endonuclease activity. Our results present a new folding mechanism and function for a negative-strand RNA virus nucleoprotein, extend our structural insight into bunyavirus NPs, and provide a potential target for antiviral drug development to treat CCHFV infection.     

The Bulgarian vaccine Crimean-Congo haemorrhagic fever virus strain

The Crimean-Congo haemorrhagic fever virus (CCHFV) is a 3-segmented RNA virus, which causes disease with a high fatality rate in humans. An inactivated suckling mouse brain-derived vaccine is used in Bulgaria for protection against CCHF. Strain V42/81 is currently used for the vaccine preparation. As the M-RNA segment plays a major role in the immune response, the full-length M segment sequence of the V42/81 strain was characterized. A great genetic diversity was observed among CCHFV strains. In order to gain an insight into the topology of the strain in the CCHFV phylogenetic trees, the full-length S and partial L segments were additionally sequenced and analyzed.     

Immunosorbent assays for diagnosis of Crimean-Congo hemorrhagic fever (CCHF)

Utilization of direct and indirect enzyme-linked immunosorbent assay (ELISA) and solid-phase radioimmunoassay (SPRIA) for the diagnosis of Crimean-Congo hemorrhagic fever (CCHF) allows the detection of low amounts of infectious virus (2 log LD50) or inactivated antigen and antibody to CCHF within 5-6 hours. These methods were shown to be more sensitive, specific, rapid, and reproducible than the complement-fixation test, immunofluorescence, hemagglutination, or radial diffusion in gel. The experimental design of ELISA and SPRIA developed for CCHF may be used successfully for the detection of the other members of the Bunyaviridae family.     

Crimean-Congo hemorrhagic fever in Southeast of Iran

In June 1999, a cluster of patients with viral hemorrhagic fever were reported in central provinces of Iran. Similar cases were subsequently verified in other parts of Iran. During June 1999 to February 2004, a total of 255 patients were recorded in Southeast of Iran. The epidemiological features, clinical manifestations, treatment and outcome will be discussed.     

Imported Crimean-Congo hemorrhagic fever cases in Istanbul

We described a series of imported cases of Crimean-Congo Hemorrhagic Fever (CCHF) in Istanbul and investigated the genetic diversity of the virus. All the suspected cases of CCHF, who were applied to the health centers in Istanbul, were screened for CCHF virus (CCHFv) infection by using semi-nested Polymerase Chain Reaction (PCR) following RT-PCR. Simultaneous blood samples were also sent to the national reference laboratory in Ankara for serologic investigation. In 10 out of 91 patients, CCHFv was detected by PCR, and among 9 out of 10, anti-CCHFv IgM antibodies were also positive. Clinical features were characterized by fever, myalgia, and hemorrhage. The levels of liver enzymes, creatinine phosphokinase, and lactate dehydrogenase were elevated, and bleeding markers were prolonged. All the cases were treated with ribavirin. There was no fatal case. All the strains clustered within the same group as other Europe/Turkey isolates.     

Antibody to Crimean-Congo hemorrhagic fever virus in wild mammals from southern Africa

Crimean-Congo hemorrhagic fever (CCHF) virus is becoming increasingly recognized as an important human pathogen in southern Africa. In order to determine the role of wild mammals in the natural ecology of the virus, sera from 3,772 wild mammals of 87 species and from 1,978 domestic dogs collected in South Africa and Zimbabwe between 1964 and 1985 were tested for antibody to CCHF virus by reversed passive hemagglutination inhibition (RPHI) and by indirect immunofluorescence (IF). Antibody was found to be highly prevalent in large mammals in the Orders Artiodactyla and Perissodactyla such as giraffe, Giraffa camelopardalis (3/3 positive), rhinoceros, Ceratotherium simium and Diceros bicornis (7/13), eland, Taurotragus oryx (59/127), buffalo, Syncerus caffer (56/287), kudu, Tragelaphus strepsiceros (17/78), and zebra, Equus burchelli (16/93). In small mammals antibody was found in the sera of 40/293 hares, 22/1,305 rodents, and 1/74 wild carnivores, but not in 522 primates, 176 insectivores, or 19 hyrax. Antibody was also found in the sera of 118/1,978 domestic dogs. The species of wild mammal in which antibody was distributed (with highest antibody prevalence in hares and large herbivores) reflects the feeding preference of immature and adult ticks of the genus Hyalomma, suggesting that Hyalomma sp. are the principal CCHF vectors in the wild.     

Evaluation of respiratory findings in Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic disease with a high mortality rate causing viral hemorrhagic fever. We studies the respiratory system findings, demographics, clinical and laboratory findings of patients with CCHF admitted to our hospital. In this retrospective study we evaluated 108 patients with CCHF confirmed by laboratory findings. The charts of all hospitalized patients were reviewed, and the age, sex, occupation, city of residence, history of tick bite or of removing a tick, smoking history, chest X-ray results, outcome and clinical and laboratory findings were recorded for each patient. Sixty of the chest radiographs were read as normal, 33 were read as showing unilateral pathology and 15 showed bilateral pathology. Seven of the 108 patients died due to severe pulmonary infection and hemorrhage. The frequency of pathological chest radiographs was higher among the CCHF patients who died than among the survivors, but the difference was not significant. Pulmonary parenchyma hemorrhage can occur in CCHF patients with hemoptysis, dyspnea, chest pain and infiltration on chest radiographs and may lead to morality.     

Preparation and use of monoclonal antibodies for identifying Crimean-Congo hemorrhagic fever virus

Seven monoclonal antibodies were prepared against a South African strain of Crimean-Congo hemorrhagic fever (CCHF) virus and were found to be directed against viral nucleocapsid protein. Five of the monoclonal antibodies reacted to high titer in indirect immunofluorescence (IF) tests and enzyme-linked immunosorbent assays (ELISA) with 22 strains of CCHF virus and failed to cross-react with the closest antigenic relative of CCHF, Hazara virus, or with 4 other nairoviruses which need to be distinguished from CCHF virus in Africa. These antibodies, used in the IF technique, readily detected antigens induced by all strains of CCHF virus included in the study in cell culture monolayers and mouse brain tissue, which represent the systems commonly used for isolation of CCHF virus. The IF technique with monoclonal antibodies constitutes a rapid and specific means of identifying newly isolated strains of CCHF virus.     

Tick cell lines for study of Crimean-Congo hemorrhagic fever virus and other arboviruses

Continuous cell lines derived from many of the vectors of tick-borne arboviruses of medical and veterinary importance are now available. Their role as tools in arbovirus research to date is reviewed and their potential application in studies of tick cell responses to virus infection is explored, by comparison with recent progress in understanding mosquito immunity to arbovirus infection. A preliminary study of propagation of the human pathogen Crimean-Congo hemorrhagic fever virus (CCHFV) in tick cell lines is reported; CCHFV replicated in seven cell lines derived from the ticks Hyalomma anatolicum (a known vector), Amblyomma variegatum, Rhipicephalus (Boophilus) decoloratus, Rhipicephalus (Boophilus) microplus, and Ixodes ricinus, but not in three cell lines derived from Rhipicephalus appendiculatus and Ornithodoros moubata. This indicates that tick cell lines can be used to study growth of CCHFV in arthropod cells and that there may be species-specific restriction in permissive CCHFV infection at the cellular level.     

Seroprevalence of Crimean-Congo hemorrhagic fever in Sistan-va-Baluchestan province of Iran

During the years 2000 to 2004, of 248 serologically confirmed cases of Crimean-Congo hemorrhagic fever (CCHF) that occurred in several parts of Iran, 169 were reported from Sistan-va-Baluchestan province. To assess the seroprevalence of CCHF virus infection within the Zahedan and Zabol districts of the Sistan-va-Baluchestan province in Iran, 300 subjects were sampled from the general population. In addition to blood sampling, a questionnaire was completed for every subject. All but just 3 of our 300 sampled subjects participated in blood sampling, and just 7 out of the 297 serum samples were found to be IgG ELISA positive. The point estimate of the seroprevalence was 0.024 (95% confidence interval: 0.003-0.044). A history of keeping livestock in houses (even for short periods) showed an association with seropositivity (P = 0.018). It seems that even occasional contact with livestock could be effective in transmission of the virus.