Cloning of the genome of a goose parvovirus vaccine strain SYG61v and rescue of infectious virions from recombinant plasmid in embryonated goose eggs

• We reported the complete genome sequence of the attenuated live vaccine strain SYG61v of GPV, whose parental strain SYG61 was the earliest GPV isolate in the world.
• By sequence comparison conducted between the SYG61v and four virulent strains, we identified common different amino acids in the Rep1 protein and the VP1 protein, respectively.
• We constructed the infectious clone plasmid of SYG61v.
• Infectious virions were rescued by transfection of plasmid pSYG61v in embryonated goose eggs.

The SYG61v is an attenuated goose parvovirus (GPV) that has been used as a vaccine strain in China. The genome of SYG61v was sequenced to attempt to identify the genetic basis for the attenuation of this strain. The entire genome consists of 5102 nucleotides (nts), with four nt deletions compared to that of virulent strain B. The inverted terminal repeats (ITR) are 442 nts in length, of which 360 nts form a stem region, and 43 nts constitute the bubble region. Although mutations were observed throughout the ITR, no mismatch was found in the stem. Alignment with other pathogenic GPV strains (B, 82-0321, 06-0329, and YZ99-5) indicated that there are 10 and 11 amino acid mutations in the Rep1 and VP1 proteins of SYG61v, respectively. The complete genome of SYG61v was cloned into the pBluescript II vector and an infectious plasmid pSYG61v was generated. Infectious progeny virus was successfully rescued through transfection of the plasmid pSYG61v in embryonated goose eggs and yielded viral titers similar to its parental virus, as evaluated by ELD50.