Assessment of the safety and efficacy of an attenuated live vaccine based on highly pathogenic porcine reproductive and respiratory syndrome virus.
The safety and efficacy of the JXA1-R vaccine, an attenuated strain of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV), were examined using an intramuscular challenge model in piglets. The JXA1-R vaccine was obtained by passing HP-PRRSV JXA1 through Marc-145 cells (82nd passage). Genomic sequence comparisons showed that strain JXA1-R and its parental strain, JXA1, differ by 47 amino acids, and most of these differences are scattered throughout the PRRSV genome. Four-week-old PRRSV-free piglets were inoculated intramuscularly with JXA1-R vaccine (10(3.0), 10(4.0), 10(5.0), 10(6.0), and 10(7.0) 50% tissue culture infective doses [TCID50]/ml for groups 1 to 5, respectively) and then challenged intramuscularly with the 5th passage virus of JXA1 virus (JXA1-F5, 3 ml × 10(4.5) TCID50/ml) 28 days after inoculation. The humoral immune response, swine growth, clinical signs, and differential organ lesions were monitored. The results showed that all vaccinated piglets had a perceptible humoral immune response to vaccination after day 7, which then promptly increased, almost reaching the maximum sample/positive (S/P) ratio value at 28 days postimmunization. Viremia detection indicated that the viral replication levels of the challenge virus in the immunized groups (immunization doses ≥10(4.0)/ml) were significantly lower than that of the virus-challenged unvaccinated control group. Piglets in groups 2 to 5 were effectively protected against lethal HP-PRRSV infection and did not show any obvious changes in body temperature or clinical signs of disease at any point during the experiment. However, two of five piglets in group 1 showed mild pathological lesions and transitory high fever. These results suggest that JXA1-R (TCID50/ml ≥10(4.0)) is sufficiently attenuated and can provide effective protection against the lethal wild-type HP-PRRSV.
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Xiuling
X
Yu
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Zhi
Z
Zhou
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Zhen
Z
Cao
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Jiajun
J
Wu
Bureau of Veterinary, Ministry of Agriculture, Beijing, China.
Zhongqiu
Z
Zhang
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Baiwan
B
Xu
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Chuanbin
C
Wang
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Dongmei
D
Hu
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Xiaoyu
X
Deng
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Wei
W
Han
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Xiaoxue
X
Gu
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Shuo
S
Zhang
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Xiaoxia
X
Li
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China.
Baoyue
B
Wang
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China zhaixy2010@sina.cn tiankg@263.net.
Xinyan
X
Zhai
OIE Porcine Reproductive and Respiratory Syndrome Reference Laboratory, China Animal Disease Control Center, Beijing, China National Research Center for Veterinary Medicine, Luoyang, Henan Province, China zhaixy2010@sina.cn tiankg@263.net.
Kegong
K
Tian
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D016679:Genome, Viral; D007273:Injections, Intramuscular; D008168:Lung / Q000473:pathology; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D017422:Sequence Analysis, DNA; D013552:Swine; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D014766:Viremia / Q000276:immunology
D000914:Antibodies, Viral; D014613:Vaccines, Attenuated; D014765:Viral Vaccines