Biological properties of the African swine fever (ASF) virus isolates originating from various regions of the Russian Federation (2013–2018) were studied in a series of experimental infections. Comparative analysis allowed us to establish the differences in the key characteristics of the infection, such us the duration of the incubation periods, disease, and the onset of death. The incubation period averaged 4.1 days, varying from 1 to 13 days. An average duration of the disease was 6.3 days and varied from 0 to 18 days. Overall case fatality was 94.5%, and antibodies were detected only in 19.3% of the animals. The biological properties of isolates Odintsovo 02/14 and Lipetsk 12/16 were significantly different from others. For this two, the presence of antibodies to the virus was detected in 71.4% and 75% of animals respectively and mortality levels were of 87.5% and 50%.

African swine fever is a contagious viral disease that has been spreading through Europe and Asia since its initial report from Georgia in 2007. Due to the large genome size of the causative agent, the African swine fever virus (ASFV), the molecular epidemiology, and virus evolution are analyzed by employing different markers. Most of these markers originate from single nucleotide polymorphisms or disparities in the copy number of tandem repeat sequences observed during the comparisons of full genome sequences produced from ASFVs isolated during different outbreaks. Therefore, consistent complete genome sequencing and comparative analysis of the sequence data are important to add innovative genomic markers that contribute to the delineation of ASFV phylogeny and molecular epidemiology during active circulation in the field. In this study, the molecular markers currently employed to assess the genotype II ASFVs circulating in Europe and Asia have been outlined. The application of each of these markers to differentiate between ASFVs from related outbreaks is described to implement a guideline to their suitability for analyzing new outbreaks. These markers do not signify the complete repertoire of genomic differences between ASFVs, but will be beneficial when analyzing the first outbreaks in a new region or a large number of samples. Furthermore, new markers must be determined via complete genome sequence analyses for enabling in-depth insights into the molecular epidemiology of ASFV.

In this study, we report on the full genome phylogenetic analysis of four ASFV isolates obtained from wild boars in Russia. These samples originated from two eastern and two western regions of Russia in 2019. Phylogenetic analysis indicated that the isolates were assigned to genotype II and grouped according to their geographical origins. The two eastern isolates shared 99.99% sequence identity with isolates from China, Poland, Belgium, and Moldova, whereas the western isolates had 99.98% sequence identity with isolates from Lithuania and the original Georgia 2007 isolate. Based on the full genome phylogenies, we identified three single locus targets, MGF-360-10L, MGF-505-9R, and I267L, that yielded the same resolving power as the full genomes. The ease of alignment and a high level of variation make these targets a suitable selection as additional molecular markers in future ASFV phylogenetic practices.

African swine fever virus (ASFV), classified as genotype II, was introduced into Georgia in 2007, and from there, it spread quickly and extensively across the Caucasus to Russia, Europe and Asia. The molecular epidemiology and evolution of these isolates are predominantly investigated by means of phylogenetic analysis based on complete genome sequences. Since this is a costly and time-consuming endeavor, short genomic regions containing informative polymorphisms are pursued and utilized instead. In this study, sequences of the central variable region (CVR) located within the B602L gene were determined for 55 ASFV isolates submitted from 526 active African swine fever (ASF) outbreaks occurring in 23 different regions across the Russian Federation (RF) between 2013 and 2017. The new sequences were compared to previously published data available from Genbank, representing isolates from Europe and Asia. The sequences clustered into six distinct groups. Isolates from Estonia clustered into groups 3 and 4, whilst sequences from the RF were divided into the remaining four groups. Two of these groups (5 and 6) exclusively contained isolates from the RF, while group 2 included isolates from Russia as well as Chechnya, Georgia, Armenia, Azerbaijan and Ukraine. In contrast, group 1 was the largest, containing sequences from the RF, Europe and Asia, and was represented by the sequence from the first isolate in Georgia in 2007. Based on these results, it is recommended that the CVR sequences contain significant informative polymorphisms to be used as a marker for investigating the epidemiology and spread of genotype II ASFVs circulating in the RF, Europe and Asia.

At present no effective measures for specific prevention and treatment of African swine fever have been developed. The control strategy for the disease is designed for rapid diagnosis of infected animals with subsequent slaughter and decontamination (stamping out). The present review deals with current epidemic situation for African swine fever and examines features of the virus genomics and genetic differentiation of the isolates. The Russian Federation has been ASF-infected since 2007. Since that time the disease has been one of the key problems in pig farming of this country inflicting great economic losses, both directly and indirectly. The disease continues to spread. In January 2014 African swine fever was introduced to Lithuania, then pervaded Poland, Latvia, Estonia, Romania, Belgium and Moldova. Since 2018 the disease outbreaks have been reported in Asia (China, Vietnam, and Mongolia). Specific structure of the virus and long genome, encoding genes with unknown function, and circulation of 24 genotypes and 9 serotypes of the virus hinder the development of ASF vaccine. The article shows that the use of many specific genetic markers during determination of relationship and study of pathways of ASF virus global spread is the most accurate method.

Introduction. African swine fever (ASF), sever hemorrhagic disease of swine caused by a large DNA virus of the Asfaviridae family.Since there are no effective and safe vaccines against ASF yet, it is urgent to study the functions of its proteins, which is applicable by analyzing the features of ASF virus replication in the presence of recombinant proteins in vitro.Purpose. To study the effect of ASFV recombinant proteins CD2v, pE248R and pX69R on the speed and level of reproduction of ASF virus in vitro. Thus, obtain the necessary knowledge to develop approaches for creating a vaccine against ASF.Materials and methods. ASFV isolate Krasnodar 07/17 and strain ASF/ARRIAH/CV-1 were used. Cloning of X69R, EP402R, and E248R genes was performed in the pJET1.2 / blunt vector and pCI-neo in E. coli JM-109 cells, according to the manufacturer's manual. Localization of recombinant proteins in CV-1 cell line carried out by direct immunofluorescence reaction (DIF) using polyclonal antibodies conjugated to FITC.The ASF virus reproduction level was assessed by hemadsorption reaction and qPCR kit (Central Research Institute of Epidemiology).Results. Recombinant plasmids pCI-neo / E248R, pCI-neo / EP402R and pCI-neo / X69R were constructed.The localization and the specificity of the obtained recombinant proteins CD2v, pE248R and pX69R was confirmed. It was established that these recombinant proteins induce the level of ASF virus reproduction on days 3-5 of the experiment by ~ 1.2-1.5 lgHADU50/cm3 in comparison with the negative control.Discussion. The data obtained demonstrate the important role of CD2v, pX69R and pE248R proteins in the reproduction of the virus, since they significantly affect its level. The exact function of pX69R protein was not determined, however, in the experiments its positive effect on ASF virus reproduction was established, manifested in an increase in its reproduction level.Conclusion. This methodology allows us to study the nature of the effect of proteins with unknown function on ASF virus replication.