Metcalfe Lucy, Chevalier Mathieu, Tiberghien Marie-Pascale, Jolivet Edmond, Huňady Milan, Timothy Sioned, Philippe-Reversat Corinne
Global Ruminant, Boehringer Ingelheim International, Ingelheim, Rheinland-Pfalz, Germany.
Boehringer Ingelheim, Lyon, France.
Vet Rec Open. 2020 Nov 6;7(1):e000429. doi: 10.1136/vetreco-2020-000429. eCollection 2020.
Two randomised controlled vaccination trials with artificial challenges were carried out in addition to a serological survey of levels of maternally derived antibodies (MDA) to parainfluenza type 3 virus (PI3V) and bovine respiratory syncytial virus (BRSV) in European calves.
Ten-day-old calves with and without MDA were included in the two vaccine trials.
Intranasal administration of a bivalent modified live (PI3V/BRSV) vaccine followed by artificial challenge approximately three months post vaccination.
The study aimed to assess the efficacy of a modified live respiratory vaccine, Bovalto Respi Intranasal (Boehringer Ingelheim). In order to assess the interference of MDA, both seropositive and seronegative calves were used.
PI3V and BRSV serological status was determined seven days before vaccination; calves without maternal antibodies became the MDA- vaccinates. Calves with MDA were ranked according to individual titres and allocated alternately to MDA+ vaccinate and MDA+ control groups.
Treatment was carried out by the unblinded study director. Animal care and veterinary examinations were conducted by personnel unaware of the treatments received. The serological survey used blood samples obtained from calves on commercial farms in five European countries, Germany, Spain, Italy, Ireland and the UK, to determine the levels of MDA to PI3V and BRSV in calves approximately two weeks of age.
A total of 36 calves were included in the two challenge studies and 32 of these completed the challenge studies. Twenty-one calves were included in the PI3V challenge study, with six of six MDA- and six of seven MDA+ vaccinated calves and five of five MDA+ unvaccinated control calves being challenged with PI3V. Fifteen calves were included in the BRSV challenge study, with five of five MDA- and five of five MDA+ vaccinated calves and five of five MDA+ unvaccinated control calves being challenged with BRSV.
For both challenges, clinical scores and nasal shedding were significantly higher in control animals compared with vaccinates (PI3V challenge: clinical scores P=0.001, nasal shedding P=0.001; BRSV challenge: clinical scores P=0.016, nasal shedding P=0.002) and not significantly different between MDA+ and MDA- vaccinated animals for both challenges (P>0.05). A total of 254 samples from six countries were tested in the serological survey of MDA.
The results of the challenge studies demonstrated the efficacy of the vaccine in the presence of BRSV and PI3V MDA under laboratory conditions. The field assessment confirmed that the MDA titres in the MDA+ calves corresponded to those typically found on farms.
除了对欧洲犊牛中针对3型副流感病毒（PI3V）和牛呼吸道合胞病毒（BRSV）的母源抗体（MDA）水平进行血清学调查外，还开展了两项人工攻毒的随机对照疫苗试验。
两项疫苗试验纳入了有和没有MDA的10日龄犊牛。
鼻内接种二价改良活疫苗（PI3V/BRSV），接种后约三个月进行人工攻毒。
该研究旨在评估一种改良活呼吸道疫苗Bovalto Respi Intranasal（勃林格殷格翰公司生产）的效力。为了评估MDA的干扰作用，使用了血清阳性和血清阴性的犊牛。
在接种疫苗前7天测定PI3V和BRSV血清学状态；没有母源抗体的犊牛成为接种MDA的组。有MDA的犊牛根据个体滴度进行排序，并交替分配到接种MDA+组和MDA+对照组。
由未设盲的研究负责人进行治疗。动物护理和兽医检查由不知道所接受治疗的人员进行。血清学调查使用从德国、西班牙、意大利、爱尔兰和英国这五个欧洲国家商业农场的犊牛采集的血样，以测定约两周龄犊牛中针对PI3V和BRSV的MDA水平。
两项攻毒研究共纳入36头犊牛，其中32头完成了攻毒研究。PI3V攻毒研究纳入21头犊牛，接种MDA的6头犊牛中的6头、接种MDA+的7头犊牛中的6头以及未接种的5头MDA+对照犊牛中的5头接受了PI3V攻毒。BRSV攻毒研究纳入15头犊牛，接种MDA的5头犊牛中的5头、接种MDA+的5头犊牛中的5头以及未接种的5头MDA+对照犊牛中的5头接受了BRSV攻毒。
对于两项攻毒试验，与接种疫苗的动物相比，对照动物的临床评分和鼻腔排菌量显著更高（PI3V攻毒：临床评分P = 0.001，鼻腔排菌量P = 0.001；BRSV攻毒：临床评分P = 0.016，鼻腔排菌量P = 0.002），并且在两项攻毒试验中，接种MDA+和MDA-的动物之间无显著差异（P>0.05）。在MDA的血清学调查中，对来自六个国家的总共254份样本进行了检测。
攻毒研究结果表明，在实验室条件下，该疫苗在存在BRSV和PI3V MDA的情况下有效。现场评估证实，接种MDA+的犊牛中的MDA滴度与农场中通常发现的滴度相符。
