Apoptosis-Related Gene Expression in an Adult Cohort with Crimean-Congo Hemorrhagic Fever

Apoptosis activation during Lagovirus europaeus/GI.2 infection in rabbits

Rabbit Haemorrhagic Disease (RHD) is a severe disease caused by Lagovirus europaeus/GI.1 and GI.2. Immunological processes such as apoptosis are important factors involved in the pathogenesis of Rabbit Haemorrhagic Disease (RHD). The process of programmed cell death has been quite well characterized in infection with GI.1 strains, but apoptosis in infection with GI.2 strains has not been widely studied. This is particularly important as several studies have shown that significant differences in the host immune response are observed during infection with different strains of Lagovirus europaeus. In this study, we analyzed the gene expression, protein levels and activity of key apoptotic cell death factors in the spleen, kidney, lung, and heart of rabbits. As a result, we showed that there is a significant increase in caspase-3, Bax, Bcl2 and Bax/Bcl2 mRNA gene expression ratio in organs of infected animals. Our results show also increased levels of cleaved caspase-3, caspase-6 and PARP. Moreover, significant activity of caspase-3 was also detected. Our results indicate that caspase-3, caspase-6 and genes coding Bcl2 family proteins play a key role in the apoptotic response in Lagovirus europaeus/GI.2 infection in organs that are not the target of virus replication.

Virus-host interactions during tick-borne bunyavirus infection

The Bunyavirales order is the largest grouping of RNA viruses, comprising emerging and re-emerging human, plant and animal pathogens. Bunyaviruses have a global distribution and many members of the order are transmitted by arthropods. They have evolved a plethora of mechanisms to manipulate the regulatory processes of the infected cell to facilitate their own replicative cycle, in hosts of disparate phylogenies. Interest in virus-vector interactions is growing rapidly. However, current understanding of tick-borne bunyavirus cellular interaction is heavily biased to studies conducted in mammalian systems. In this short review, we summarise current understandings of how tick-borne bunyaviruses utilise major cellular pathways (innate immunity, apoptosis and RNAi responses) in mammalian or tick cells to facilitate virus replication.

MicroRNA analysis from acute to convalescence in Crimean Congo hemorrhagic fever

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

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

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

Regulation of Hazara virus growth through apoptosis inhibition by viral nucleoprotein

Hazara virus (HAZV) is closely related to Crimean-Congo hemorrhagic fever virus (CCHFV), but differs in that it is non-pathogenic to humans. Since HAZV was isolated for the first time in 1954, the biological characteristics of this virus, particularly its behavior within culture cells, have not been well-studied, despite its importance as a surrogate model for CCHFV. Nucleoprotein (N) is the main component of viral nucleocapsid and is the most abundant virion protein, it is believed to play a pivotal role in the viral lifecycle. Generation of a series of anti-HAZV N monoclonal antibodies has enabled us to directly examine the involvement of this protein on viral growth. Observation of HAZV-infected cells revealed that this infection caused apoptosis, which was further characterized by DNA ladder and elevated caspase-3/7 activity. HAZV titers initially increased in cell culture, but after reaching the peak titer began to rapidly decline. HAZV particles were found to be very unstable in culture medium at 37 °C, and virus particles tend to lose infectivity at that point. HAZV N appears to inhibit apoptosis, thus can potentially support efficient viral propagation.

Apoptosis and its relation with clinical course in patients with Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a tick-mediated viral infection. Patients with CCHF may show various clinical presentations. The cause of this difference in the clinical course is not completely understood. Apoptosis is programmed cell death and plays an important role in regulating the immune system. Our knowledge of the role of apoptosis in CCHF disease is limited. We investigated the role of apoptosis and their relationship with the severity of the disease in CCHF. Thus, in 30 patients with CCHF and 30 healthy individuals, we analyzed the serum levels of cytochrome C, apoptotic protease activating factor-1 (Apaf 1), caspase 3, caspase 8, caspase 9, sFas, sFasL, perforin, granzyme B, and CK18 by enzyme-linked immunosorbent assay. This is the first study that research the serum levels of the mentioned apoptosis markers in adult patients with CCHF. We found that the serum levels of sFasL, cytochrome C, Apaf 1, caspase 3, caspase 8, caspase 9, perforin, granzyme B, and M30 were statistically significantly different in the acute phase of the disease compared with healthy individuals and patients in convalescent period. There was no association between the clinical severity of the disease and apoptosis markers. In conclusion, the results of our study suggested that the extrinsic and intrinsic apoptosis pathway play an important role in CCHF.

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.