The objective of this study was to compare immunological responses and lymphoid depletion in young, colostrum deprived calves following administration of vaccines containing modified-live bovine viral diarrhea virus (BVDV). A group of calves exposed to a typical virulence non-cytopathic (ncp) BVDV-2 field strain (ncp exposed) was included to compare responses of calves receiving vaccine to responses generated against a field strain (mimicking a natural infection). A negative control group administered a placebo was used in all comparisons. All vaccines used in the study were administered per manufacturer recommendations while ncp BVDV exposed calves received 5 ml intranasally (2.5 ml/nare; 4.2 × 10⁶ TCID₅₀/ml) of the BVDV-2 field strain. Samples collected at each time point included nasal swabs for virus detection, blood samples for complete blood counts and detection of viremia, PBMCs for flow cytometric analysis, serum for virus neutralization titers, and thymus tissue at necropsy for evaluation of lymphoid depletion. A measurable neutralizing BVDV titer was observed for all treatment groups excluding the control animals, which remained negative during the study period. Virus shedding was only detected from the ncp vaccinated and ncp exposed calves. A decline from baseline was observed for peripheral lymphocyte and CD4⁺ cells for the groups receiving the adjuvanted cytopathic (cp) vaccine, the double deleted genetically modified (ddGM) vaccine, the ncp vaccine and ncp exposed calves, but not for the control group or groups receiving cp vaccines. Thymus depletion was observed for the ncp vaccine and ncp exposed calves and to a lesser extent for the ddGM vaccine calves. Collectively, these data suggest that the virus biotype, method of attenuation, presentation, and use of adjuvant will influence vaccine impacts on lymphoid tissues and the immune response. As such, multiple variables should be considered when determining costs and benefits of vaccination.

这项研究的目的是比较在接种含有改良活牛病毒性腹泻病毒（BVDV）的疫苗后，初乳剥夺的幼小牛的免疫反应和淋巴消耗。包括一组暴露于典型毒力非细胞毒性（ncp）BVDV-2田间菌株（暴露于ncp）的牛犊，以比较接受疫苗的牛犊与针对田间菌株产生的应答（模拟自然感染）的反应。在所有比较中均使用给予安慰剂的阴性对照组。研究中使用的所有疫苗均按照制造商的建议进行管理，而暴露于ncp BVDV的犊牛经鼻腔接受5 ml（2.5 ml /鼻； 4.2×10 ⁶ TCID ₅₀/ ml）。在每个时间点收集的样本包括用于检测病毒的鼻拭子，用于全血细胞计数和病毒血症检测的血液样本，用于流式细胞术分析的PBMC，用于病毒中和滴度的血清以及在尸检时用于评估淋巴消耗的胸腺组织。对于除对照动物以外的所有治疗组均观察到可测量的中和BVDV滴度，在研究期间其保持阴性。仅从接种了ncp的小牛和暴露于ncp的小牛中检测到病毒脱落。外周血淋巴细胞和CD4 ^+较基线下降细胞用于接受辅助细胞病（cp）疫苗，双缺失基因修饰（ddGM）疫苗，ncp疫苗和ncp暴露小牛的组，但不适用于接受cp疫苗的对照组。观察到ncp疫苗和暴露于ncp的牛犊胸腺耗竭，而ddGM疫苗牛犊的胸腺耗竭程度较小。这些数据共同表明，病毒的生物型，减毒，呈递和佐剂的使用方法将影响疫苗对淋巴组织和免疫反应的影响。因此，在确定疫苗接种的成本和收益时应考虑多个变量。