A Preliminary Study on Genetic Variation of g E Gene of an Epidemic Pseudorabies Virus Strain and Its Pathogenicity to Piglets

[Objective] This study aimed to investigate the genetic variation of g E gene of an epidemic pseudorabies virus（PRV） strain and its pathogenicity to piglets. [Method] By serial passage in Vero cells, a PRV strain was isolated from the brain tissues of stillborn fetuses delivered by sows with suspected PRV infection and preliminarily identified by PCR. g E gene of the isolated PRV strain was amplified and sequenced for phylogenetic analysis. In addition, the pathogenicity of the isolated PRV strain to 6-week-old piglets was evaluated. [Result] A PRV strain was successfully isolated and named PRV N5 B strain, which could proliferate in Vero cells and TCID50 of the 15 thgeneration virus liquid reached 10^7.125/0.1 ml. Specific bands could be amplified by PCR. g E gene in the isolated PRV strain was 1 740 bp in length. A phylogenetic tree was constructed based on full-length g E sequences, which showed that PRV N5 B strain and PRV strains isolated since 2012 were clustered into the same independent category and shared 99.7%-100% homology of nucleotide sequences. Compared with related sequences published previously, there were insertions of three consecutive bases at two loci. Animal experiments showed that intranasal inoculation of 6-week-old piglets with 2 ml of PRV N5 B strain（10^6/0.1 ml） led to a mortality rate of 100%. [Conclusion] In this study,genetic variability of g E gene in PRV N5 B isolate and its pathogenicity to piglets were analyzed, which provided a theoretical basis for the development of new vaccines to prevent and control porcine pseudorabies.

Genetic Variation of Porcine Circovirus Type 2 Isolate 201105ZJ

[Objective] This study aimed to investigate the genetic variation of porcine circovirus type 2 （PCV2） in China. [Method] The strain was isolated from infected samples by cel passage and preliminarily identified by PCR and IFA. Ful-length genome of the isolated strain was obtained by specific amplification for homology and phylogenetic analysis. [Result] A PCV2 strain was successful y isolated and named 201105ZJ, which could proliferate in PK15 cel lines. Specific fragments could be amplified by specific PCR assay. According to results of IFA assay, specif-ic immunofluorescence was observed; the TCID50 was low （102.67）; the ful-length genome sequence of the isolated strain was 1 768 bp, sharing 94.1%-96.8% ho-mology with 13 reference strains; to be specific, the isolated strain exhibited the highest homology of 96.8% with AF055392PCV2a; the isolated strain 201105ZJ and reference strain AF055392 belonged to genotype PCV2a, exhibiting a distant genetic relationship with genotype PCV2c. [Conclusion] Characteristics of genetic variation of PCV2 isolate 201105ZJ provided theoretical basis for vaccine development, investi-gation of PCV2 pathogenesis, and prevention and control of porcine circovirus-as-sociated diseases （PCVAD） in East China.

Identification of A Field Strain of Infectious Laryngotracheitis Virus Isolated from Jiangsu Province

[ Objective] To isolate and identify infectious laryngotracheitis virus （ILTV） from chickens. [ Method] Larynx, trachea, liver and other organs were collected from infectious laryngotracheitis （ILT）-suspected layers. And ILTV TK gene was amplified from these specimens by PCR for initial diagnosis. Virus fluid was isolated and inoculated into SPF chicken embryos via allantoic cavity and chorioallantoic membrane （CAM）, respectively. Hyaluronic acid in allantoic fluid was detected, and CAM lesions were observed. The definite diagnosis was performed through animal regression test. [Result] A 1.3 kbp fragment was amplified from larynx and its secretion of the ILT-suspected chickens. And its amino acid sequence had 98.5% homology to that of ILTV TKgene published in GenBank. After the chicken embryos were inoculated with the isolated ILFV fluid, pox spots, giant polynuclear syncytial cells having intranuclear inclusion bodies were observed in CAM. After being challenged by the IL TV fluid, the chickens showed typical respiratory symptoms and pathological changes of ILT. [Coudusion] A field strain named ILTV XZ09 was isolated from larynx and its secretion of ILT-suspected chickens.