Development of an indirect enzyme immunoassay based on recombinant capsid protein for the detection of antibodies to porcine circovirus type 2

Porcine circovirus type 2 (PCV2) is one of the most significant pathogens in the global pig industry. Due to the fact that the distinctive feature of porcine circovirus-associated diseases (PCVAD) is a chronic course, it is necessary to introduce effective serodiagnostics methods to determine viral kinetics in pig populations. The aim of the study was to develop an indirect enzyme-linked immunosorbent assay (ELISA) based on a recombinant capsid protein to detect antibodies to PCV2. At the first stage, the structure of the capsid protein was analyzed, based on which the dominant regions for antibody recognition were determined. These fragments were included in the multiepitope insert encoding the target diagnostic antigen with a molecular weight of 17,8 kDa. As a result of expression of the ORF-2 gene fragment in E. coli cells, a soluble protein was obtained and purified to an electrophoretically homogeneous state using metal chelate chromatography. Using this antigen, taking into account the recommendations of the World Organization for Animal Health (WOAH), the conditions for ELISA were optimized. A preliminary assessment of the analytical characteristics was carried out on a sample of known positive and negative blood sera of pigs, as well as 181 sera of pigs aged 3 to 9 months, collected from different farms in the Republic of Tatarstan. It was found that the average seroprevalence of PCV2 in individual pig populations was 72,9 % (95% CI: 66,0–78,9 %). However, to determine the dynamics of PCVAD in pig populations, further serological monitoring is necessary in combination with an assessment of the virological profile of the herd.