El-Kanawati Z R, Tsunemitsu H, Smith D R, Saif L J
Department of Veterinary Preventive Medicine, Ohio State University, Wooster 44691, USA.
Am J Vet Res. 1996 Jan;57(1):48-53.
To investigate in vitro antigenic relations, in vivo cross-protection, and isotype antibody responses to a winter dysentery (WD) and calf diarrhea strain of bovine coronavirus (BCV). DESIGN AND ANIMALS: Gnotobiotic and colostrum-deprived calves were inoculated oronasally with a WD (DBA) or a calf diarrhea (DB2) BCV, and were challenge exposed with the heterologous BCV.
Nasal swab and feces specimens and blood samples were collected. Fecal and nasal specimens were assayed for BCV shedding by antigen-capture ELISA or immune electron microscopy. Bovine coronavirus antigens were detected in nasal epithelial cells by immunofluorescence. Antibody titers to BCV in serum were assayed by virus neutralization (VN), and BCV antibody isotype titers in feces and sera were quantitated by ELISA.
All calves developed diarrhea and shed BCV nasally and in feces, then recovered and were protected from BCV-associated diarrhea after challenge exposure with the heterologous BCV. After challenge exposure with either strain, fecal shedding of DBA was detected in 1 of 4 calves and nasal shedding of DB2 was detected in 2 of 4 calves. Immunoglobulin M was the principal coproantibody to BCV early, followed predominantly by IgA. Immunoglobulin G1 coproantibody titers to BCV were low, but increased after challenge exposure. Immunoglobulin G1 antibodies were predominant in serum. After challenge exposure, all serum antibody isotype titers increased except IgG2. The VN antibody responses paralleled serum IgG1 antibody responses.
Immunoglobulin A coproantibodies at challenge exposure were associated with protection against diarrhea. Nasal shedding of BCV after challenge exposure confirmed field data documenting reinfection of the respiratory tract of cattle, suggesting that, in closed herds, respiratory tract infections constitute a source of BCV transmission to cows (WD) or young calves.
研究牛冠状病毒（BCV）冬季痢疾（WD）株和犊牛腹泻株的体外抗原关系、体内交叉保护及同种型抗体反应。设计与动物：将无菌和初乳缺乏的犊牛经口接种WD（DBA）或犊牛腹泻（DB2）BCV株，并以异源BCV进行攻毒暴露。
采集鼻拭子、粪便标本和血液样本。通过抗原捕获ELISA或免疫电子显微镜检测粪便和鼻标本中的BCV排出情况。通过免疫荧光在鼻上皮细胞中检测牛冠状病毒抗原。通过病毒中和（VN）测定血清中针对BCV的抗体滴度，并通过ELISA定量粪便和血清中BCV抗体同种型滴度。
所有犊牛均出现腹泻，鼻和粪便中排出BCV，随后恢复，并在异源BCV攻毒暴露后免受与BCV相关的腹泻。用任一毒株攻毒暴露后，4头犊牛中有1头检测到DBA的粪便排出，4头犊牛中有2头检测到DB2的鼻排出。免疫球蛋白M早期是针对BCV的主要粪便抗体，随后主要是IgA。针对BCV的免疫球蛋白G1粪便抗体滴度较低，但在攻毒暴露后升高。免疫球蛋白G1抗体在血清中占主导。攻毒暴露后，除IgG2外，所有血清抗体同种型滴度均升高。VN抗体反应与血清IgG1抗体反应平行。
攻毒暴露时的免疫球蛋白A粪便抗体与预防腹泻有关。攻毒暴露后BCV的鼻排出证实了现场数据，记录了牛呼吸道的再感染，表明在封闭牛群中，呼吸道感染是BCV传播给母牛（WD）或幼犊的一个来源。
