Ectromelia Virus Affects Mitochondrial Network Morphology, Distribution, and Physiology in Murine Fibroblasts and Macrophage Cell Line.

Mitochondria are multifunctional organelles that participate in numerous processes in response to viral infection, but they are also a target for viruses. The aim of this study was to define subcellular events leading to alterations in mitochondrial morphology and function during infection with ectromelia virus (ECTV). We used two different cell lines and a combination of immunofluorescence techniques, confocal and electron microscopy, and flow cytometry to address subcellular changes following infection. Early in infection of L929 fibroblasts and RAW 264.7 macrophages, mitochondria gathered around viral factories. Later, the mitochondrial network became fragmented, forming punctate mitochondria that co-localized with the progeny virions. ECTV-co-localized mitochondria associated with the cytoskeleton components. Mitochondrial membrane potential, mitochondrial fission⁻fusion, mitochondrial mass, and generation of reactive oxygen species (ROS) were severely altered later in ECTV infection leading to damage of mitochondria. These results suggest an important role of mitochondria in supplying energy for virus replication and morphogenesis. Presumably, mitochondria participate in transport of viral particles inside and outside of the cell and/or they are a source of membranes for viral envelope formation. We speculate that the observed changes in the mitochondrial network organization and physiology in ECTV-infected cells provide suitable conditions for viral replication and morphogenesis.

African Swine Fever Virus: a new old enemy of Europe

African swine fever (ASF) is a highly contagious viral disease of swine with a mortality rate approaching 100 percent. African Swine Fever Virus (ASFV) is a double-stranded DNA virus with a complex molecular structure. Its large genome, encoding multiple virulence factors, allows for efficient replication, which takes place predominantly in the cytoplasm of monocytes and macrophages. Also, ASFV has the ability to interfere with cell signalling pathways, which leads to various modulations in the synthesis profiles of interferon and other cytokines. Sustained viremia favours the persistence of virions in blood and tissues of the convalescents, and the extended circulation of ASFV within the herd. ASFV has been spreading in the Caucasus since 2007, and in 2014 reached the eastern territory of the European Union. Outbreaks pose an economical threat to native pig rearing, especially since a single point source may easily develop into an epizootic event. There is currently no effective vaccine nor treatment for ASF, and eradication is possible only by prevention or the slaughter of diseased animals. This review paper summarizes the current state of knowledge about ASFV.

Remodeling of the fibroblast cytoskeletal architecture during the replication cycle of Ectromelia virus: A morphological in vitro study in a murine cell line.

Ectromelia virus (ECTV, the causative agent of mousepox), which represents the same genus as variola virus (VARV, the agent responsible for smallpox in humans), has served for years as a model virus for studying mechanisms of poxvirus-induced disease. Despite increasing knowledge on the interaction between ECTV and its natural host-the mouse-surprisingly, still little is known about the cell biology of ECTV infection. Because pathogen interaction with the cytoskeleton is still a growing area of research in the virus-host cell interplay, the aim of the present study was to evaluate the consequences of ECTV infection on the cytoskeleton in a murine fibroblast cell line. The viral effect on the cytoskeleton was reflected by changes in migration of the cells and rearrangement of the architecture of tubulin, vimentin, and actin filaments. The virus-induced cytoskeletal rearrangements observed in these studies contributed to the efficient cell-to-cell spread of infection, which is an important feature of ECTV virulence. Additionally, during later stages of infection L929 cells produced two main types of actin-based cellular protrusions: short (actin tails and "dendrites") and long (cytoplasmic corridors). Due to diversity of filopodial extensions induced by the virus, we suggest that ECTV represents a valuable new model for studying processes and pathways that regulate the formation of cytoskeleton-based cellular structures. © 2016 Wiley Periodicals, Inc.

[MAVS protein and its interactions with hepatitis A, B and C viruses]. / Bialko MAVS i jego interakcje z wirusami zapalenia watroby typu A, B i C.

Mitochondrial antiviral signaling protein (MAVS) transmits activation signal of type I interferon (IFN) gene transcription in the molecular intracellular pathway, which depends on the protein encoded by retinoic acid inducible gene I (RIG-I) or melanoma differentiation-associated protein-5 (MDA-5). MAVS, as a signal molecule, performs an essential function in the development of an antiviral immune response. The molecule of MAVS consists of two domains: the N-terminal domain and the C-terminal domain. The N-terminal end of MAVS contains the caspase activation and recruitment domain (CARD). CARD is responsible for MAVS interaction with RIG-I and MDA-5, which act as cytosolic sensors detecting foreign viral genetic material in the host cell. After binding to viral RNA, RIG-I or MDA-5 activates MAVS and transmits the signal of IFN type I gene expression. The C-terminal transmembrane domain (TM) of MAVS anchors the protein to the outer mitochondrial membrane. In this paper interactions between MAVS and hepatitis virus type A (HAV), type B (HBV) and type C (HCV) are presented. Mechanisms of indirect activation of MAVS by viral DNA and RNA, as well as the strategies of HAV, HBV and HCV for blocking of the intracellular signaling pathway at the level of MAVS, are described.

[Cooperation between heat shock proteins in organizing of proteins spatial structure]. / Wspóldzialanie bialek szoku cieplnego w organizowaniu struktury przestrzennej bialek.

Heat shock proteins (Hsps) are a class of proteins with highly conserved amino acid sequences. They are widespread in nature; they are found in archeons, true bacteria and eukaryotic organisms. Hsps from various families, commonly interact to execute essential cellular tasks, such as molecular regulation of newly synthesized protein-folding or restoration of the appropriate conformation of denatured and aggregated proteins. In this review we discuss mechanisms of spatial organization of protein structure mediated by Hsp10, Hsp40, Hsp60, Hsp70, Hsp104 (Hsp100) and Hsp110. Interactions between Hsps of different molecular weights are described.

Changes in the mitochondrial network during ectromelia virus infection of permissive L929 cells.

Mitochondria are extremely important organelles in the life of a cell. Recent studies indicate that mitochondria also play a fundamental role in the cellular innate immune mechanisms against viral infections. Moreover, mitochondria are able to alter their shape continuously through fusion and fission. These tightly regulated processes are activated or inhibited under physiological or pathological (e.g. viral infection) conditions to help restore homeostasis. However, many types of viruses, such as orthopoxviruses, have developed various strategies to evade the mitochondrial-mediated antiviral innate immune responses. Moreover, orthopoxviruses exploit the mitochondria for their survival. Such viral activity has been reported during vaccinia virus (VACV) infection. Our study shows that the Moscow strain of ectromelia virus (ECTV-MOS), an orthopoxvirus, alters the mitochondrial network in permissive L929 cells. Upon infection, the branching structure of the mitochondrial network collapses and becomes disorganized followed by destruction of mitochondrial tubules during the late stage of infection. Small, discrete mitochondria co-localize with progeny virions, close to the cell membrane. Furthermore, clustering of mitochondria is observed around viral factories, particularly between the nucleus and viroplasm. Our findings suggest that ECTV-MOS modulates mitochondrial cellular distribution during later stages of the replication cycle, probably enabling viral replication and/or assembly as well as transport of progeny virions inside the cell. However, this requires further investigation.