# Epidemiological Survey of Porcine Circovirus Types 2 and 3 in Liaoning Region of China and Preparation of Monoclonal Antibodies Against PCV3 Cap Protein

## TL;DR

This study examines the spread of PCV2 and PCV3 in pigs in Liaoning, China, and develops a monoclonal antibody for PCV3 detection.

## Contribution

The study reports the development of a specific monoclonal antibody against PCV3 Cap protein and provides updated epidemiological data from Liaoning.

## Key findings

- PCV2 and PCV3 positivity rates were 14.13% and 21.90%, with a 4.08% coinfection rate in Liaoning pig farms.
- All six Cap gene sequences were classified as PCV3b subtype, indicating a prevalent genetic variant.
- A monoclonal antibody (3E6) was successfully developed and showed specific reactivity with the PCV3 Cap protein.

## Abstract

Porcine circovirus (PCV) is a major viral pathogen associated with multiple systemic disorders in pigs, inflicting substantial economic losses on the global swine industry. In 2024, 1224 clinical samples were collected from 21 large-scale pig farms in Liaoning Province and detected for PCV2 and PCV3 using quantitative polymerase chain reaction (qPCR). The results demonstrated PCV2 and PCV3 positivity rates of 14.13% and 21.90%, respectively, with a coinfection rate of 4.08%. Six Cap gene sequences were obtained by PCR amplification and sequencing, and their sequences were classified as belonging to the PCV3b subtype. Furthermore, the PCV3 Cap protein was heterologously expressed in a prokaryotic system, an indirect ELISA was established, and a specific monoclonal antibody (3E6) targeting this protein was successfully developed. Collectively, this study elucidates the epidemiological characteristics and genetic evolutionary patterns of PCV in Liaoning Province, providing crucial theoretical support and experimental evidence for the prevention and control of PCV3, as well as for the development of diagnostic methods and vaccines against this virus.

Porcine circovirus (PCV) is a major viral pathogen associated with multiple systemic diseases in pigs, inflicting significant economic losses to the global swine industry. To investigate the epidemiology and genetic evolution of porcine circovirus in Liaoning Province, China, PCV was detected by qPCR in 1224 clinical samples. Subsequent genetic evolution analysis of the Cap gene was conducted, and an indirect ELISA and monoclonal antibody were established. The results demonstrated PCV2 and PCV3 positivity rates of 14.13% and 21.90%, respectively, with a coinfection rate of 4.08%. All six sequences were identified as belonging to the PCV3b subtype. A representative PCV3 strain was expressed in a prokaryotic expression system and used to immunize 6-week-old female BALB/c mice, resulting in serum antibody titers reaching 1:512,000. The positive hybridoma cell line 3E6 was selected and identified as expressing IgM heavy chains and κ light chains. The prepared monoclonal antibody 3E6 exhibited specific reactivity with the Cap protein. Collectively, this study elucidates the recent epidemiological status and evolutionary characteristics of PCV in pig populations in Liaoning Province, thereby providing an important theoretical basis and reference data for disease prevention, control, diagnosis, and vaccine development.