Determination of reproductive properties of virulent and vaccine classical swine fever virus strains in primary and continuous cell cultures

Classical swine  fever  (CSF) is a highly dangerous porcine disease. CSF outbreaks are annually notified in several countries. Despite the availability of specific prevention tools, the disease spread risk still persists both at country level and at world level. Hence, the disease surveillance and eradication require highly sensitive methods for early diagnosis of the infection and for tests for the virus circulation in the environment.  Development of up-to-date  diagnostic methods is based on well-established  virus cultivation system; therefore, CSF virus reproduction enhancement,  tests of new cell lines without  endogenous  contamination  for their possible use are still of current importance. The said study was aimed at testing of primary and continuous cell cultures for their susceptibility to classical swine fever virus (vaccine virus strains and some field virus isolates recovered in the Russian Federation) and detection of the virus reproduction dynamics with real-time polymerase chain reaction with fluorescent hybridization probes used for detection. Virus replication intensity in primary and continuous cell cultures was also analyzed. The CSF virus was found incapable of replicating in some cell cultures without  its preliminary adaptation.  Primary porcine and lamb testicle cell cultures grown in minimal essential medium supplemented  with 10% normal CSFV-negative porcine serum instead  of fetal bovine serum were shown to be useful for the virus accumulation, both for vaccine strains and field isolates. Cultivation parameters and optimal minimal essential medium composition contributing to the 4–10-fold  increase in the virus accumulation  both in primary and continuous  cell cultures were determined

EFFECTS OF MODERATELY VIRULENT AFRICAN SWINE FEVER VIRUS ON INTERLEUKIN-10 PRODUCTION

A characteristic feature of African swine fever virus (ASFV) is the ability to escape from host immune response, affecting macrophages and replicating in them. Besides, ASFV - specific antibodies do not completely neutralize the virus. Cytokines are important factors for various viral infection pathologies. The virulence of ASFV isolates may depend on the capacity to regulate cytokine expression by macrophages. Thus, when comparing in vitro and in vivo cytokine production by macrophages, it was established that infection with low virulent virus isolates leads to an immune response with a predominance of cytokines involved in cellular immunity, such as INF-α and IL-12p40, as compared with infection with highly virulent isolates. The aim of this paper was to study the effect of African swine fever virus on the production of IL-10, a pleiotropic cytokine that inhibits synthesis of cytokines and shows a strong antiinflammatory effect. For this, 12 piglets were experimentally infected intramuscularly with a continuous cell culture-adapted ASFV isolate Vero25 at a dose of 10 HAdU per animal followed by control infection of surviving animals with the reference virus isolate Arm 07 at a dose of 1,000 HAdU per animal. Temperature measurements were taken and blood sampling to obtain serum was conducted during the experiment. IL-10 amount in blood sera was determined using Invitrogen test systems (Thermo Fisher, USA). A higher IL-10 level (15.8–173 pg/ml) was observed in blood sera of dead animals infected with a moderately virulent virus, as compared with surviving pigs (4–5 pg/ml). No correlation between the speed of appearance of specific antibodies and IL-10 serum levels has been established. No noticeable effect of the IL-10 serum level prior to infection on the survival rate of animals has been observed. Further studies are needed to establish a causal relationship, including study of the expression of various cytokines during infection with both low- and highly virulent virus isolates

ANALYSIS OF MONITORING STUDIES ON AFRICAN SWINE FEVER VIRUS DNA DETECTION CARRIED OUT IN 2017

The paper describes the results of testing of biomaterial from domestic pigs and wild boars by real-time PCR used for African swine fever virus genome detection, carried out in the FGBI “Federal Centre for Animal Health” (Vladimir). In 2017 8,500 samples from 44 subjects of the Russian Federation were tested within the framework of the state laboratory monitoring. African swine fever virus genome was detected in 504 samples. In 2017 ASF outbreaks were registered in the Urals and Siberian Federal Districts of the RF for the first time. The conducted research and persistent ASF infection in the territory of the RF have demonstrated the need for further surveillance in the populations of susceptible animals. Development, organization and implementation of the program for ASF spread surveillance in wild fauna remains a high priority. It is necessary to create and implement sampling schedules with uniform sampling of biomaterial and submission of the collected samples to the research laboratories for timely ASF outbreak containment at the regional level