3.4 Analysis of sequence variation in the newly goat PRV strain
To further address the genetic characteristics of YNG strain, the major
viral immune (gB , gC , and gD ) and virulence gene
(gE and TK ) sequences were successfully amplified and
sequenced. The findings revealed that the lengths of gB ,gC , gD , gE and TK genes of YNG strain were
2745 bp, 1464 bp, 1209 bp, 1737 bp, and 1023 bp, respectively (GenBank
accession numbers: MW458931, MW392295, MW458932, MW458933, MW458934).
Sequence analysis results also showed that there existed continuous
nucleotides insertion encoding65AASTPAA71 in the gC gene in
comparison to referring PRV strains in genotype I, such as Bartha and
Becker strains (Fig. 4A ). Similarly, a 6-nucleotide deletion
(encoding 278SP279) in the gDgene was identified in YNG strain relative to classical PRV strains (eg.
Fa and Ea) prevalent in Chinese pig population before 2011, indicating
that YNG strain is a PRV variant (Fig. 4B ). Compared with other
referring variants, only few amino acid variations in gB gene of
YNG strain were identified, while no amino acid variations of TK ,gC , and gD genes were found. Notably, compared to other
PRV strains, a 3-nt deletion (encoding D at the position of 490) was
found in the gE gene of YNG strain and another variant PRV strain
(JX/CH/2016, Genbank number accession: MK806387) isolated in Guangdong
province, China (Fig. 4C ).
To define the evolutionary position of YNG strain among numerous
referring strains from different regions or hosts, gC andgE gene based phylogenetic trees were constructed, respectively
(Fig. 4D&E ). The results demonstrated that all PRV strains
prevalent in the world could be divided into two genotypes (genotype I
and II), and the genotype II was composed of classical PRV strains
prevalent before 2011 and variant PRV strains circulated after 2011 in
China. Notably, most of PRV strains isolated from different hosts (pigs,
dogs, wolves, sheep, foxes, human, etc.) prevalent in China, including
YNG strain, belonging to the genotype II, presented a random
distribution. Additionally, the phylogenetic position of YNG strain was
closer to these of variant PRV strains than classical PRV strains, and
far away from the traditional vaccine strains (such as Bartha) belonging
to the genotype I.