PCV2 infection causes:
- Post-Weaning Multisystemic Wasting Syndrome (PMWS)
- Porcine Dermatitis and Nephropathy Syndrome (PDNS)
- Porcine Respiratory Disease Complex (PRDC)
- Collectively called Porcine Circovirus Associated Diseases (PCVAD).
- Causes losses of several million dollars per year to the pork industry.
PCV2 is one of the smallest mammalian viruses with just two products:
The Capsid protein and the Rep and Rep’ proteins.
As can be seen below, PCV2a, 2b, 2c, and 2d display robust variation in the defined epitopes which complicates vaccine design.
Alignment and Epitope Map of PCV2 Capsid Protein
(You may click on image for enlargement.)
Although PCV2 has a DNA genome, it is subject to evolutionary emergence of antigenic variants that can escape immune pressure. Since the introduction of the first vaccine in 2006, the circulating strains have evolved from PCV2a to PCV2b to PCV2d and beyond. Several vaccines are available that do not stimulate protective immunity against continuously evolving antigenic variants. This tree was constructed from 105 capsid protein gene sequences.*
* From: Weissenbacher-Lang et al. BMC Veterinary Research (2020) 16:198