Joanna Cymerys

Mechanisms of endocytosis utilized by viruses during infection.

Viruses, despite being relatively simple in structure and composition, have evolved a broad spectrum of mechanisms to exploit the host cell. To initiate effective infection, viruses or viral genomes have to enter cells. Recently studies have shown that apart from the direct fusion at the plasma membrane, endocytosis is more often the preferred means of entry into the host cell. Endocytosis is a complex phenomenon, that includes multiple pathways of membrane trafficking, such as clathrin-mediated endocytosis, caveolin-mediated endocytosis, macropinocytosis and phagocytosis. Endosomes offer a convenient and often rapid transit system across the plasma membrane and cytoplasm via the cellular microtubular network. They also provide protection to the virus from detection by the hosts innate immune defences. What is important, viruses are able to utilize not just one, but multiple uptake routes. Identification of these processes and factors will not only allow a better insight into pathogenic mechanism, but may identify novel targets for future therapeutic development. This review provides insight on recent developments in the rapidly evolving field of viral entry.

Herpesviruses survival strategies - latency and apoptosis

Apoptosis is a process of programmed cell death in response to various stimuli, including virus infection. Herpesviruses have evolved the ability to interfere with apoptosis by its inhibition or activation in host cells. They can interfere with the extrinsic and intrinsic pathways of apoptosis. A special feature of herpesviruses is establishing a latent infection, during which expression of virus genes is strongly restricted and production of infectious virus particles is not observed. HSV-1 establishes latency in neurons, CMV in bone marrow progenitor cells and monocytes, EBV and HHV-8 in B cells. Studies show that latent infections also depend on prevention of the death of the infected cells. Control of apoptosis machinery by viruses may be critical for their reproduction and provision of the adequate yield of progeny virions. The present article summarizes the current knowledge about the latent viral infection and mechanisms of apoptosis modulation by selected viruses from the Herpesviridae family.

Application of three-dimensional neuronal cell cultures in the studies of mechanisms of neurodegenerative diseases

In vitro models utilizing cells in planar two-dimensional (2D) cultures do not reflect the in vivo environment and are increasingly replaced by three-dimensional (3D) cultures. Fundamental differences between 2D and 3D cell cultures systems include cell attach, spread and grow, their morphology, proliferation, differentiation or gene and protein expression. For that reason 3D models have been proven to be invaluable tools of study for the various fields of science, such as drug discovery, cancer research, differentiation studies or neuroscience. In the present review, we discuss 3D neural in vitro models that might provide important insides about the mechanisms of pathogenesis of neurodegenerative diseases.

Acyclovir and trichostatin A modulate EHV-1 replication in murine neurons in vitro

Equine herpesvirus type 1 (EHV-1) is one of the most important viral pathogens of horses worldwide (2). It may cause respiratory disease, sporadic or epizootic abortions, or, recently more often, neurological disease known as equine herpesvirus myeloencephalopathy (EHM), which may be life-threatening and results in significant economic losses to the equine industry (1, 13, 15, 18, 19). It has been suggested that a single-nucleotide polymorphism in the EHV-1 DNA polymerase gene, which leads to amino acid variation (N752/D752), may be associated with outbreaks of EHM (3, 11, 13). D752 strains of EHV-1, which are statistically more often isolated from cases of EHM, were called neuropathogenic strains. However, it is worth mentioning that all EHV-1 strains show neurotropism and are capable of establishing latency in peripheral neurons. Moreover, EHV-1 may also establish latency in leukocytes (10). The main role of latency is to maintain the viral genome for a long time inside host cells, at the same time avoiding the immune response. On the other hand, the virus may reactivate and start productive replication at any time, especially during stress, which leads to the dissemination of progeny virions (17). The current approach to the control of EHV-1 infections is based on biosecurity measures and vaccination, but it is not sufficient. Immunity after infection or vaccination is usually incomplete and short-lived, and once latency has been established, the virus cannot be eliminated from host cells. Although some progress has been made in understanding the adaptive immunity to EHV-1, innate immunity remains poorly characterized, despite the fact that it is critically important for inducAcyclovir and trichostatin A modulate EHV-1 replication in murine neurons in vitro1)

Primary murine neurons as in vitro model for studying neuroinfections caused by human adenoviruses

Adenoviral infections of the central nervous system are rare, but they are characteristic for their high mortality rate. People with impaired immunity and children are particularly vulnerable. A few reports of neuroinfections caused by adenoviruses are found in literature. In this study the tropism of the human adenoviruses type 4, 5, 7 to primary cultures of murine neurons and the influence of infection on the neuron morphology and actin cytoskeleton was examined. The A549 non-small-cell lung cancer cell line was used as a reference line. Viral effects upon the cell culture were evaluated by direct immunofluorescence. The levels of adenovirus replication in the above-mentioned cell cultures were determined by real-time PCR. In the current study we demonstrated for the first time that human adenovirus (HAdV) type 4, 5 and 7 exhibits tropism for neurons cultured in vitro followed by the extensive replication of all serotypes in the primary culture of murine neurons. Immunofluorescent labelling and confocal microscopy revealed the changes in cell morphology, destruction of actin cytoskeleton and cell lysis as the final stage of infection. According to the obtained results we can assume that productive cycle of HAdV in the studied cell cultures occurred. We also observed accumulation of nuclear actin within nuclei of infected cells which may indicate that it plays role in adenovirus infection and replication in neurons and A549 cells.