Generation of porcine circovirus type 4 virus-like particles and their use to detect serum antibodies

Abstract

Porcine Circovirus type 4 (PCV4), rst identi ed in 2019 as a newly emerging pathogen, has been found in several provinces of China, as well as in Korea and Thailand. Since PCV4 is not included in immunization programs, epidemiological investigations should be conducted for PCV4-positive antibodies detection.Virus-like particles (VLPs) are commonly employed for serological analysis of pathogen infections.However, there are no reports on using PCV4 VLPs in PCV4 infection investigation. In this study, we successfully generated self-assembled PCV4 VLPs using an E.coli expression system and puri ed the PCV4 VLPs through a two-step puri cation process. Subsequently, we utilized the puri ed VLPs as encapsulated antigens to develop an indirect ELISA. The established ELISA method showed high speci city, sensitivity, and repeatability, making it suitable for PCV4 antibodies investigation of serum samples. Finally, the ELISA was applied to detect 422 serum samples from regions in China, of which 134 tested positive. Therefore, PCV4-VLPs-based ELISA could effectively detect antibodies against PCV4 in serum samples, contributing to a better understanding of PCV4 epidemiology.

Identification of a conserved B-cell epitope on the capsid protein of porcine circovirus type 4

“…The PCV4 Cap proteins were successfully expressed using the prokaryotic system. The supernatant was collected and purified using two-step chromatography ( 31 ). The purified protein exhibited a molecular weight of approximately 27 kDa, as shown by the SDS-PAGE ( Fig.…”

“…After the initial immunization, the same doses of adjuvanted PCV4 VLPs were boosted twice at 14-day intervals. Following three times vaccinations, antibody titers against PCV4 VLPs in serum reached 1:51,200 as measured by PCV4-VLP-ELISA ( 31 ). One week after the last immunization, the mice were intraperitoneally boosted with 20 µg of PCV4 VLPs without adjuvant.…”

“…PCV4 Cap protein has been reported to interact with DDX21 and localize to the nucleus, a characteristic shared with other PCV Caps ( 29 ). Additionally, PCV4 virus-like particle (VLP) has a comparable structure and morphology to other PCVs, measuring ~20 nm ( 30 , 31 ). PCV4 VLP was also shown to enter PK-15 and 3D4/21 Cells, consistent with permissive cell lines of PCV2 ( 22 , 30 , 32 , 33 ).…”