Labarque G, Van Gucht S, Van Reeth K, Nauwynck H, Pensaert M
Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
Vet Microbiol. 2003 Sep 1;95(3):187-97. doi: 10.1016/s0378-1135(03)00157-3.
In this study, the efficacy of two attenuated porcine reproductive and respiratory syndrome virus (PRRSV) vaccines was assessed. The virological protection in the lungs of vaccinated pigs upon challenge was studied. Also, challenged pigs were exposed to lipopolysaccharide (LPS) to evaluate clinical protection. Six-week-old pigs were immunized intramuscularly with commercial vaccines based on either an attenuated American or an attenuated European virus strain. Non-immunized pigs and pigs intramuscularly inoculated with the virulent Lelystad strain were included as controls. Six weeks after immunization, pigs were challenged either intratracheally or intranasally with the Lelystad strain, and 3 and 6 days later intratracheally exposed to Escherichia coli LPS. After LPS administration, pigs were monitored for clinical signs. At 4 and 7 days after challenge, pigs were euthanized to determine virus quantities in broncho-alveolar lavage (BAL) fluids and in lungs. Challenge virus was recovered from three out of eight pigs that had been primo-inoculated with the Lelystad strain with titers ranging between 0.3 and 3.1 log(10). Fifteen out of sixteen pigs vaccinated with the attenuated American strain were positive for challenge virus and their mean virus titers were similar to those of non-immunized challenge controls. Eleven out of 16 pigs vaccinated with the attenuated European strain were positive for challenge virus and their mean virus titers were 2.0-2.5 log(10) lower than those of non-immunized challenge controls. Thus, the virological protection in the lungs of vaccinated pigs upon challenge was incomplete, but was more pronounced in the homologous situation. Clinical signs upon LPS exposure in both vaccinated groups were not reproducible in two experiments.
在本研究中，评估了两种减毒猪繁殖与呼吸综合征病毒（PRRSV）疫苗的效力。研究了接种疫苗的猪在攻毒后肺部的病毒学保护情况。此外，让攻毒后的猪接触脂多糖（LPS）以评估临床保护情况。六周龄的猪肌肉注射基于减毒美国毒株或减毒欧洲毒株的商业疫苗。未免疫的猪和肌肉接种强毒力莱利斯塔德毒株的猪作为对照。免疫六周后，猪通过气管内或鼻内途径用莱利斯塔德毒株攻毒，3天和6天后通过气管内途径接触大肠杆菌LPS。给予LPS后，监测猪的临床症状。攻毒后4天和7天，对猪实施安乐死以测定支气管肺泡灌洗（BAL）液和肺中的病毒量。从最初接种莱利斯塔德毒株的8头猪中的3头猪体内分离到攻毒病毒，滴度在0.3至3.1 log(10)之间。接种减毒美国毒株的16头猪中有15头攻毒病毒呈阳性，其平均病毒滴度与未免疫的攻毒对照相似。接种减毒欧洲毒株的16头猪中有11头攻毒病毒呈阳性，其平均病毒滴度比未免疫的攻毒对照低2.0 - 2.5 log(10)。因此，接种疫苗的猪在攻毒后肺部的病毒学保护是不完全的，但在同源情况下更为明显。在两个实验中，两个接种组在接触LPS后的临床症状均不可重复。
