Validation of a test system for African swine fever serodiagnosis using immunoblotting

Because of the lack of a vaccine, African swine fever (ASF, caused by African swine fever virus (ASFV) of Asfivirus genus, Asfarviridae family) control strategy is based on making a rapid and early diagnosis and taking strict veterinary and sanitary measures. In the Eastern Europe countries where the infection has currently spread, highly virulent isolates are usually detected (J.M. Sanchez-Vizcaino et al., 2013). In the laboratory diagnosis, polymerase chain reaction (PCR) and direct immunofluorescence method are predominantly used. However, since 2012, researchers have observed some alteration in biological and genetic properties of a number of ASFV isolates. Therefore, serological methods may become prevalent in the laboratory diagnosis as it was during an ASF epizooty in the Iberian Peninsula in 1960-1990. We have earlier reported the development of a test system for the disease immunoblotting serodiagnosis (Rec p30-IB) based on a recombinant structural ASFV protein p30 (A.S. Kazakova et al., 2014). In this paper, the Rec p30-IB test system validation is shown. The diagnostic sensitivity of the Rec p30-IB was of 99.3 %, and the specificity was 100 %. Antibodies against p30 were detected in blood serum and organ samples taken from domestic pigs or wild boars irrespective of the seroimmunotypic membership and the virulence levels of the ASFV strains. In the blood serum samples collected from domestic pigs infected with heterologous viruses, no false-positive results were seen. In the serum of domestic pigs which were survived after intramuscular injection of attenuated strains LK-111, KK-262/С, MK-200, FK-135, PSA-1-NH and SCA 2015 VNIIVViM at 103 to 104 HAU50/CPE50, antibodies to p30 were detected on day 7 to 10. For organ samples from domestic pigs that had died from ASF 5 to 10 days post intramuscular infection with highly virulent strains Lisbon-57, Mozambique-78 or Stavropol 01/08 at a dose of 103 HAE50, the antibodies to p30 were detected in 30 % of the animals. The validation results indicate that the Immunoblotting Test System for African Swine Fever Serodiagnosis (Rec p30-IB) can be used for laboratory practice and monitoring of blood sera and organ samples collected from ASFV-infected domestic pigs or wild boars.