Fig. 1

Schematic representation of the CPV genome and its coding genes. CPV genomes range from 7.5 kb to 8.6 kb, reflecting variations in their genetic composition. Early genes (E1, E2, E4, E5, E6, E7) and late genes (L1, L2) perform essential functions in viral replication, immune evasion, and pathogenesis. E1 acts as a helicase, facilitating DNA unwinding and replication, while E2 regulates transcription, supports E1, and aids genome segregation. E4 contributes to genome amplification and viral release. E5 present only in several genotypes (e.g. CPV2, CPV11, CPV16, CPV19, and CPV20, is regarded to modulate growth factor receptors to enhance immune evasion and cell growth. E6 degrades the tumor suppressor protein p53, preventing apoptosis and enabling cell transformation, whereas E7 inactivates the Rb protein, driving the cell into S-phase for viral replication and oncogenesis. In the late phase, L1 forms the major capsid protein, assembling viral particles and eliciting immune responses, while L2, the minor capsid protein, assists in genome encapsidation and nucleus delivery. The coordination of these genes allows for the successful infection and propagation of CPVs