Heckert R A, Saif L J, Mengel J P, Myers G W
Department of Veterinary Preventive Medicine, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691.
Am J Vet Res. 1991 May;52(5):700-8.
Ten colostrum-deprived calves were assigned to 1 of 2 treatment groups (5 calves/group), and fed colostrum that had either low (naturally infected cows) or high (immunized cows) antibody titers to bovine coronavirus (BCV). All calves were inoculated orally and intranasally with virulent BCV when they were 24 to 48 hours old and challenge exposed 21 days later. Blood, feces, nasal secretions, tears, saliva, and bronchoalveolar lavage (BAL) fluids were collected weekly from each calf for 5 weeks after inoculation. The titers to whole BCV or the relative amounts of isotype-specific antibodies to BCV structural proteins were evaluated in these samples by ELISA or immunoblotting, respectively. Both pools of colostrum contained primarily IgG1, IgG2, and IgA antibodies to the E2 and E3 BCV proteins. Calves fed the high-titer colostrum had correspondingly higher amounts of passive IgG1 and IgA antibodies to whole BCV and to the E2 and E3 BCV proteins in serum, feces, and BAL fluid at postinoculation week 1 than those calves fed low-titer colostrum. Active IgG1, IgA, and IgM antibody responses in serum and active IgA and IgM antibody responses in most mucosal secretions to whole BCV and to the E2 and E3 proteins were lower or delayed in calves fed high-titer colostrum, compared with responses in calves fed low-titer colostrum. In contrast, increased responses to the BCV N protein were observed in all samples (except in serum and BAL fluid) in the calves fed high-titer colostrum, compared with calves fed low-titer colostrum. Upon challenge exposure, responses to E2 and E3 BCV proteins in serum and BAL fluid were lower in the group fed high-titer colostrum, compared with those in the group fed low-titer colostrum. Our findings indicate that the level of passive immunity in calves at the time of BCV inoculation can influence the development of active antibody responses in serum, feces, and mucosal secretions to whole BCV and to some BCV proteins individually.
十头未摄入初乳的犊牛被分配到两个处理组中的一组（每组5头），并分别喂食对牛冠状病毒（BCV）抗体滴度低（自然感染的奶牛）或高（免疫的奶牛）的初乳。所有犊牛在24至48小时大时经口和鼻内接种强毒BCV，并在21天后进行攻毒暴露。接种后5周内每周从每头犊牛采集血液、粪便、鼻分泌物、眼泪、唾液和支气管肺泡灌洗（BAL）液。分别通过ELISA或免疫印迹法在这些样本中评估针对完整BCV的滴度或针对BCV结构蛋白的同型特异性抗体的相对量。两组初乳中主要都含有针对BCV E2和E3蛋白的IgG1、IgG2和IgA抗体。在接种后第1周，喂食高滴度初乳的犊牛血清、粪便和BAL液中针对完整BCV以及BCV E2和E3蛋白的被动IgG1和IgA抗体量相应地高于喂食低滴度初乳的犊牛。与喂食低滴度初乳的犊牛相比，喂食高滴度初乳的犊牛血清中的活性IgG1、IgA和IgM抗体反应以及大多数黏膜分泌物中针对完整BCV以及E2和E3蛋白的活性IgA和IgM抗体反应较低或延迟。相比之下，与喂食低滴度初乳的犊牛相比，喂食高滴度初乳的犊牛所有样本（血清和BAL液除外）中针对BCV N蛋白的反应增加。在攻毒暴露时，喂食高滴度初乳组血清和BAL液中针对BCV E2和E3蛋白的反应低于喂食低滴度初乳组。我们的研究结果表明，BCV接种时犊牛体内的被动免疫水平会影响血清、粪便和黏膜分泌物中针对完整BCV以及个别BCV蛋白的活性抗体反应的发展。
