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

Porcine circovirus type 4 (PCV4), first identified 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 detection of anti-PCV4 antibodies. Virus-like particles (VLPs) are frequently used for serological analysis of pathogen infections. However, there have been no reports on using PCV4 VLPs for serological investigation of PCV4 infection. In this study, we generated self-assembled PCV4 VLPs using an E. coli expression system, purified them using a two-step process, and used them to develop an indirect ELISA. This ELISA method was found to be highly specific, sensitive, and repeatable, making it suitable for PCV4 antibody detection in serum samples. Finally, the ELISA was used to analyze 422 serum samples collected from across several regions in China, 134 of which tested positive. Thus, the PCV4-VLP-based ELISA can effectively detect antibodies against PCV4 in serum samples, making it a useful tool for PCV4 epidemiology.