African Swine Fever Virus Manipulates the Cell Cycle of G0-Infected Cells to Access Cellular Nucleotides.

African swine fever virus manipulates the cell cycle of infected G0 cells by inducing its progression via unblocking cells from the G0 to S phase and then arresting them in the G2 phase. DNA synthesis in infected alveolar macrophages starts at 10-12 h post infection. DNA synthesis in the nuclei of G0 cells is preceded by the activation of the viral genes K196R, A240L, E165R, F334L, F778R, and R298L involved in the synthesis of nucleotides and the regulation of the cell cycle. The activation of these genes in actively replicating cells begins later and is less pronounced. The subsequent cell cycle arrest at the G2 phase is also due to the cessation of the synthesis of cellular factors that control the progression of the cell cycle-cyclins. This data describes the manipulation of the cell cycle by the virus to gain access to the nucleotides synthesized by the cell. The genes affecting the cell cycle simply remain disabled until the beginning of cellular DNA synthesis (8-9 hpi). The genes responsible for the synthesis of nucleotides are turned on later in the presence of nucleotides and their transcriptional activity is lower than that during virus replication in an environment without nucleotides.

Patterns of alveolar macrophage activation upon attenuated and virulent African swine fever viruses in vitro.

The pattern of porcine alveolar macrophage (AM) activation upon classical stimuli of two strains of African swine fever (ASF) viruses, an attenuated ASFV-BA71V and virulent ASFV-Georgia2007 were investigated. In an in vitro experiment ASFV-Georgia2007-infected AM showed M1 polarization pattern different from the one induced by classical stimuli. Altered morphology, appearance of binuclear cells, decreased synthesis of IFN-alpha as well as IFN-epsilon was observed compared with attenuated ASFV-BA71V, and decreased synthesis of IFN-omega compared with intact cells. However, CD68 level did not significantly differ between alveolar macrophage populations infected by ASFV-Georgia2007 and control group, while both LPS/IFN-gamma stimulation and non-pathogenic ASFV-BA71V virus increased the level of CD68 soluble receptor. AM infection with ASFV-Georgia2007 resulted in remarkable DNA proliferation whereas LPS/IFN-gamma and ASFV-BA71V induced less expressed DNA proliferation in activated cells. The higher value of nitric oxide was obvious in the cells infected with ASFV-BA71V, compared to ASFV-Georgia2007 and LPS/IFN-gamma activated cells. In conclusion, pattern of activation of alveolar macrophages induced by ASFV-Georgia2007 virus differs from the one expressed in LPS/IFN-gamma- and ASFV-BA71V-activated cells. ASFV-BA71V and LPS/IFN-gamma share similar antiviral response of porcine AM. Therefore we assume that wild type virulent ASFV can partially down regulate antiviral response of AM and conclude that evolutionary decrease of virulence in ASFV is related to alterations of control of the host cell antiviral response.

Evaluation of Viral Genome Copies Within Viral Factories on Different DNA Viruses.

This article describes a simple method of measuring the number of viral genomes within viral factories. For this purpose, we use three DNA viruses replicating in the cytoplasm of the infected cells: wild-type African swine fever virus (ASFV)-Georgia 2007, culture-adapted type ASFV-BA71V, and Vaccinia virus (VV). The measurements are conducted in three steps. In the first step, after DNA staining, we evaluate Integrated Optical Density (IOD) of total DNA for each viral factory. The second step involves the calculations of the mass of DNA in the viral factories in picograms (pg). And, in the third step, by dividing the mass of DNA within viral factory by the weight of a single viral genome, we obtain the number of viral genomes within the factory.

Pathomorphology of the brain in the acute form of African swine fever

The brains of 10 infected pigs were examined for histopathology and presence of African swine fever virus (ASFV) DNA ASFV infection induces inflamed meninges, cerebral edema and vascular thrombosis, as well as subdural hematomas. Slight tension in the dura mater, flattening of the gyri and narrowing of the sulci were also observed at four days post infection (dpi). Enlarged perivascular spaces were detected for most vessels of the brain after three to four dpi. Considerable lymphocytic infiltration of the brain tissue was observed at the terminal stage of disease. ASFV was present in all investigated areas of brain beginning from three to four dpi. The isolated virus do not differ from the used in present study Georgia 2007 strain.