Passive immune transfer (PIT) and dynamics of specific antibodies in calves naturally exposed to the respiratory viruses

ABSTRACT This research evaluated the PIT and the dynamics of specific antibody (Ab) for calves naturally exposed to the viral agents involved in Bovine Respiratory Disease (BRD). Nineteen Holstein calves fed colostrum from vaccinated donors for DRB. Serum samples were obtained before and after colostrum intake (48h) for serum neutralization (SN). Mean values (log2) detected after colostrum feeding were 11.5±1.6 (BVDV), 8.8 ±1.3 (BoHV-1) 5.5±1.6 (BRSV) and 8.4±1.5 (BPIV-3). Five calves were raised from birth to 240 days of life and presented a decrease in Ab titers for BVDV, BoHV-1 and BPIV-3 over time (P≤ 0.001). Infection rates from D14 to D240 were of 40% (2/5), 20% (1/5), 80% (4/5) and 60% (3/5), respectively for BVDV, BoHV-1, BRSV and BPIV-3. Most of the calves presented bronchopneumonia after seroconversion to the virus. Calves presented Ab for all viruses at 48 hours of life, however BRSV Ab titer were low. Levels and persistence of maternal antibody titers determined the susceptibility to viral infections.

摘要：本研究针对自然暴露于牛呼吸道疾病（Bovine Respiratory Disease, BRD）相关病毒的犊牛，评估了其被动免疫转移（PIT）与特异性抗体（specific antibody, Ab）的动态变化。本研究共纳入19头荷斯坦犊牛，其饲喂了来自针对DRB进行免疫的供体的初乳。分别于初乳摄入前及摄入后48小时采集血清样本，用于开展血清中和试验（serum neutralization, SN）。初乳饲喂后检测得到的以2为底的对数均值分别为：牛病毒性腹泻病毒（BVDV）11.5±1.6、牛疱疹病毒1型（BoHV-1）8.8±1.3、牛呼吸道合胞体病毒（BRSV）5.5±1.6以及牛副流感病毒3型（BPIV-3）8.4±1.5。选取5头犊牛从出生饲养至240日龄，其针对BVDV、BoHV-1及BPIV-3的抗体滴度随时间推移均出现显著下降（P≤0.001）。在第14日龄至第240日龄期间，BVDV、BoHV-1、BRSV及BPIV-3的感染率分别为40%（2/5）、20%（1/5）、80%（4/5）与60%（3/5）。多数犊牛在针对上述病毒发生血清转换后出现支气管肺炎。犊牛在出生后48小时即可检出针对所有受试病毒的抗体，但针对BRSV的抗体滴度较低。母源抗体滴度的水平与持续性，决定了犊牛对上述病毒感染的易感性。