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Abstract: Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral zoonosis distributed widely in Africa, Asia, Russia and the Balkans. Occurrence of segment reassortment has been established and may be associated with pathogenicity. The ability to distinguish between an infection with a reassortant and a non-reassortant variant may have prognostic value. In this study the use of Simple-Probe technology and real-time PCR was investigated to detect rapidly CCHF viral nucleic acid and to distinguish between reassorted and non-reassorted variants of southern African CCHF virus (CCHFV) isolates. A Simple-Probe® was designed based on multiple alignments of 19 CCHFV partial M segment sequences that included reassorted and non-reassorted isolates from two phylogenies. Real-time PCR followed by probe-specific melting-curve analysis allowed differentiation of three selected isolates representative of two phylogenetically distinct groups, SPU 431/85 (group IV), 383/87 (group IV) and 103/87 (group III) based on melting temperatures. Within group IV there are two distinct lineages which were represented in the optimization. A further 16 clinical isolates could be genotyped into groups III and IV using the Simple-Probe real-time PCR assay developed in this study. This assay provides a reliable and sensitive tool for the differentiation between reassorted and non-reassorted variants of CCHFV which finds application for diagnosis and epidemiologic and surveillance studies. [ABSTRACT FROM AUTHOR]

In contrast to animals, Crimean-Congo hemorrhagic fever (CCHF) causes a severe disease in humans with a high mortality rate. The etiological agent, CCHF virus (CCHFV), can be transmitted by argasid and ixodid ticks, but arachnids of the genus Hyalomma, followed by Rhipicephalus and Dermacentor serve as the major vectors of this virus. The goal of the study was to assess the epidemiological situation of CCHFV infection in cattle in south-east Poland, and survey for potential tick vector species. A total of 592 bovine blood samples from animals located in the southernmost region in Poland were tested by IgG sandwich enzyme-linked immunosorbent assay. Ticks ( n = 993) from south-east Poland were collected from dogs, cats, cattle, and horses and tested by RT-PCR. All 592 serum samples were negative for IgG antibodies to CCHFV. Of the ticks collected, 125 were Dermacentor reticulatus and 868 represented Ixodes ricinus, both species are regarded as potential vectors of CCHFV. All tick samples were negative for the presence of CCHFV. Considering the zoonotic nature, public health importance, and the virus increasing spread, it was prudent to assess the seroprevalence of CCHFV in the south-east area of Poland, bordering with CCHFV endemic areas. It seems unlikely that CCHFV infection will suddenly spread in Poland, but considering the multiple possibilities of the virus introduction, serosurveys and vector biosurveillance should be conducted at regular intervals. [ABSTRACT FROM AUTHOR]

Crimean-Congo hemorrhagic fever virus (CCHFV) is a bunyavirus causing severe hemorrhagic fever disease in humans, with high mortality rates. The requirement of a high-containment laboratory and the lack of an animal model hampered the study of the immune response and protection of vaccine candidates. Using the recently developed interferon alpha receptor knockout (IFNAR-/-) mouse model, which replicates human disease, we investigated the immunogenicity and protection of two novel CCHFV vaccine candidates: a DNA vaccine encoding a ubiquitin-linked version of CCHFV Gc, Gn, and N and one using transcriptionally competent virus-like particles (tc-VLPs). In contrast to most studies that focus on neutralizing antibodies, we measured both humoral and cellular immune responses. We demonstrated a clear and 100% efficient preventive immunity against lethal CCHFV challenge with the DNA vaccine. Interestingly, there was no correlation with the neutralizing antibody titers alone, which were higher in the tc-VLP-vaccinated mice. However, the animals with a lower neutralizing titer, but a dominant cell-mediated Th1 response and a balanced Th2 response, resisted the CCHFV challenge. Moreover, we found that in challenged mice with a Th1 response (immunized by DNA/DNA and boosted by tc-VLPs), the immune response changed to Th2 at day 9 postchallenge. In addition, we were able to identify new linear B-cell epitope regions that are highly conserved between CCHFV strains. Altogether, our results suggest that a predominantly Th1-type immune response provides the most efficient protective immunity against CCHFV challenge. However, we cannot exclude the importance of the neutralizing antibodies as the surviving immunized mice exhibited substantial amounts of them. [ABSTRACT FROM AUTHOR]