Genetic variation, pathogenicity, and immunogenicity of highly pathogenic porcine reproductive and respiratory syndrome virus strain XH-GD at different passage levels.
Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important infectious diseases of swine worldwide. Immunization with an attenuated vaccine is considered an effective method for reducing the economic losses resulting from porcine reproductive and respiratory syndrome virus (PRRSV) infection. Several studies have shown that PRRSV can be attenuated by passage in Marc-145 cells, but it is still not clear whether this attenuation influences the immunogenicity of PRRSV and what the mechanism of attenuation is. In order to study the mechanism of attenuation and immunogenicity of highly pathogenic (HP) PRRSV, the HP-PRRSV strain XH-GD was serially 122 times passaged in Marc-145 cells. Genomic sequence comparisons were made at selected passages. To explore the differences in pathogenicity and immunogenicity at different passages, three passages (P5, P62 and P122) were selected for an animal challenge experiment, which showed that passage in Marc-145 cells resulted in attenuation of the virus. After 122 passages, 35 amino acid changes were observed in the structural proteins and non-structural proteins. The animal challenge experiment showed that pathogenicity decreased with increasing passage number. The N antibody level and specific neutralizing (SN) antibody titers also decreased with increasing passage number in the late stage of the animal experiment. This study indicated that the virulence of XH-GD was decreased by passage in Marc-145 cells and that overattenuation might influence the immunogenicity of virus. These results might contribute to our understanding of the mechanism of attenuation.
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Yao
Y
Chen
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Shuyi
S
He
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Long
L
Sun
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Yongfeng
Y
Luo
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Yankuo
Y
Sun
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Jiexiong
J
Xie
Guangdong Provincial Key Laboratory of Prevention and Control for Severe Clinical Animal Diseases, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Pei
P
Zhou
Guangdong Provincial Key Laboratory of Prevention and Control for Severe Clinical Animal Diseases, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China.
Shuo
S
Su
MOA Key Laboratory of Animal Vaccine Development, Ministry of China, College of Veterinary Medicine, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou, 510642, China. guihongzh@scau.edu.cn.
Guihong
G
Zhang
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D005260:Female; D014644:Genetic Variation; D008297:Male; D008969:Molecular Sequence Data; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity*; D016415:Sequence Alignment; D012692:Serial Passage; D013552:Swine; D014765:Viral Vaccines / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D014774:Virulence
D014765:Viral Vaccines