Morphological changes in human neural cells following tick-borne encephalitis virus infection

Abstract

Tick-borne encephalitis (TBE) is one of the leading and most dangerous human viral neuroinfections in Europe and north-eastern Asia. The clinical manifestations include asymptomatic infections, fevers and debilitating encephalitis that might progress into chronic disease or fatal infection. To understand TBE pathology further in host nervous systems, three human neural cell lines, neuroblastoma, medulloblastoma and glioblastoma, were infected with TBE virus (TBEV). The susceptibility and virus-mediated cytopathic effect, including ultrastructural and apoptotic changes of the cells, were examined. All the neural cell lines tested were susceptible to TBEV infection. Interestingly, the neural cells produced about 100-to 10 000-fold higher virus titres than the conventional cell lines of extraneural origin, indicating the highly susceptible nature of neural cells to TBEV infection. The infection of medulloblastoma and glioblastoma cells was associated with a number of major morphological changes, including proliferation of membranes of the rough endoplasmic reticulum and extensive rearrangement of cytoskeletal structures. The TBEV-infected cells exhibited either necrotic or apoptotic morphological features. We observed ultrastructural apoptotic signs (condensation, margination and fragmentation of chromatin) and other alterations, such as vacuolation of the cytoplasm, dilatation of the endoplasmic reticulum cisternae and shrinkage of cells, accompanied by a high density of the cytoplasm. On the other hand, infected neuroblastoma cells did not exhibit proliferation of membranous structures. The virions were present in both the endoplasmic reticulum and the cytoplasm. Cells were dying preferentially by necrotic mechanisms rather than apoptosis. The neuropathological significance of these observations is discussed. INTRODUCTIONTick-borne encephalitis virus (TBEV) is the most medically important member of the tick-borne group of the genus Flavivirus within the family Flaviviridae (Thiel et al., 2005). The virus represents a causative agent of tick-borne encephalitis (TBE), a severe infection of the central nervous system (CNS) (Gritsun et al., 2003), which is prevalent throughout wide areas in Europe and Asia.The nature of the host cell response to TBEV infection remains undefined. Characteristic, but not disease-specific neuropathologic changes in the CNS include meningitis and polioencephalomyelitis predominantly in the spinal cord, brainstem and cerrebellum associated with inflammatory cell infiltration. These pathological changes have been described in mice (Osetowska & Wró blewskaMularczyk, 1966; Rů žek et al., 2009), hamsters (Simon et al., 1966), monkeys (Simon et al., 1967 and humans (Seitelberger & Jellinger, 1966; Környey, 1978;Beer et al., 1999; Schellinger et al., 2000; Gelpi et al., 2005 Gelpi et al., , 2006. Although cytopathic effects (CPEs) have been observed primarily in virus-infected neurons, other cells can also exhibit pathological changes, presumably through bystander injury.To clarify the inter...

Electron Tomography Analysis of Tick-Borne Encephalitis Virus Infection in Human Neurons

“…In a previous study, we compared TBEV growth in human neuroblastoma, glioblastoma, medulloblastoma, and PS cells. That study showed that virus replication in neural cell lines was more than 100 times more efficient than in the PS cells14. In the present study, we showed that primary HNs were also highly sensitive to TBEV infection, and they also produced high virus titers.…”

“…Various cellular models, including neuronal cell lines, primary cultures of embryonic or neonatal mouse and rat neuronal cells, and neurons derived from embryonic stem cells, have been used to explore infections with various neurotropic viruses (e.g., polio, herpes simplex type 1, varicella-zoster, West Nile, Japanese encephalitis, and rabies)10111213. We previously examined TBEV infections in human neural (neuroblastoma, glioblastoma, and medulloblastoma) cell lines14. On the ultrastructural level, the infection caused massive morphological changes in cells, including the proliferation and rearrangement of rough endoplasmic reticulum (RER) and signs of apoptosis or necrosis14.…”

“…We previously examined TBEV infections in human neural (neuroblastoma, glioblastoma, and medulloblastoma) cell lines14. On the ultrastructural level, the infection caused massive morphological changes in cells, including the proliferation and rearrangement of rough endoplasmic reticulum (RER) and signs of apoptosis or necrosis14.…”

Nucleoside Inhibitors of Tick-Borne Encephalitis Virus

“…PS cells are widely used for TBEV isolation and for multiplication and plaque assays (30). Human neuroblastoma cells are highly sensitive to TBEV infection and represent a valuable model for neuropathogenesis studies of TBEV as well as for studies of several other neurotropic viruses (31). The initial screening was performed using two TBEV strains, Neudoerfl and Hypr, which represent two virulence models.…”

“…Porcine kidney stable (PS) cells were cultured at 37°C in Leibovitz (L-15) medium supplemented with 3% precolostral calf serum and a 1% mixture of penicillin and glutamine (Sigma-Aldrich, Prague, Czech Republic) (30). Human neuroblastoma UKF-NB-4 cells were cultured at 37°C in 5% CO 2 in Iscove's modified Dulbecco's medium (IMDM) supplemented with 10% fetal bovine serum and a 1% mixture of penicillin and streptomycin (Sigma-Aldrich) (31). All experiments were performed with TBEV strains Hypr and Neudoerfl, which are representatives of the West European TBEV subtype.…”