Department of Population Health and Pathobiology, Veterinary School, North Carolina State University , Raleigh , NC , USA.
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University , College Station , TX , USA.
Avian Pathol. 2019 Dec;48(6):564-572. doi: 10.1080/03079457.2019.1643451. Epub 2019 Aug 7.
In previous studies, we have demonstrated that very virulent plus Marek's disease viruses (vv+MDV) are highly immunosuppressive in commercial meat-type chickens. The specific objectives of this work were to evaluate if vv+MDV immunosuppression (MDV-IS) is induced by reduction of lymphocyte responsiveness and/or viability. Three experiments were conducted to (i) compare vv+MDV 686 with a partially attenuated 686-BAC; (ii) compare vv+MDV strains (648A and 686) with vMDV (GA) and vvMDV (Md5); and (iii) compare chickens vaccinated with Md5-BACΔMEQ and with CVI988 + HVT. In each experiment, spleens were collected at 28-30 days post infection and lymphocytes were isolated and investigated in three ways: their proliferative response to Concanavalin A (ConA) was analysed by MTT proliferation assay; cell death, and expression of CD45 and MHC-I was studied by flow cytometry; and MHC-IA and β-2 microglobulin (B2M) expression was evaluated by real time RT-PCR. Splenocytes of chickens inoculated with vv+MDV were severely impaired to proliferate when exposed to ConA. Furthermore, vv+MDV induced severe splenocyte death that did not occur after infection with v or vvMDV strains. Vaccination with CVI988 + HVT, and at less level with Md5-BACΔMEQ reduced these negative effects. This is in contrast to our previous results in which Md5-BACΔMEQ but not CVI988 + HVT protected against MDV-IS suggesting that although cell death and decrease lymphocyte function seem to be related to MDV virulence and certainly will be associated with immunosuppression, they might not fully explain the previously reported MDV-IS. vv+MDV induces extensive death in splenocytes in meat-type chickens 28-30 dpi. vv+MDV impairs lymphocyte function in meat-type chickens 28-30 dpi. Vaccination protects against splenocyte death and reduced lymphocyte function. Cell lysis and reduced lymphocyte function do not fully explain MDV-IS.
在之前的研究中，我们已经证明了非常强毒型马立克氏病病毒（vv+MDV）在商业肉用型鸡中具有高度免疫抑制性。这项工作的具体目标是评估 vv+MDV 免疫抑制（MDV-IS）是否是通过淋巴细胞反应性和/或活力的降低而诱导的。进行了三项实验来：（i）比较 vv+MDV 686 与部分减毒的 686-BAC；（ii）比较 vv+MDV 株（648A 和 686）与 vMDV（GA）和 vvMDV（Md5）；（iii）比较接种 Md5-BACΔMEQ 和 CVI988+ HVT 的鸡。在每个实验中，在感染后 28-30 天收集脾脏，并通过三种方式分离淋巴细胞进行研究：通过 MTT 增殖测定分析它们对刀豆球蛋白 A（ConA）的增殖反应；通过流式细胞术研究细胞死亡以及 CD45 和 MHC-I 的表达；并通过实时 RT-PCR 评估 MHC-IA 和 β-2 微球蛋白（B2M）的表达。用 vv+MDV 接种的鸡的脾细胞在接触 ConA 时严重受损，无法增殖。此外，vv+MDV 诱导严重的脾细胞死亡，而在用 v 或 vvMDV 株感染后不会发生这种情况。用 CVI988+ HVT 接种，用 Md5-BACΔMEQ 接种程度较低，可降低这些负面影响。这与我们之前的结果形成对比，在之前的结果中，Md5-BACΔMEQ 而不是 CVI988+ HVT 可预防 MDV-IS，表明尽管细胞死亡和淋巴细胞功能下降似乎与 MDV 毒力有关，并且肯定与免疫抑制有关，但它们可能无法完全解释之前报道的 MDV-IS。vv+MDV 在 28-30dpi 的肉用型鸡中诱导大量脾细胞死亡。vv+MDV 在 28-30dpi 的肉用型鸡中损害淋巴细胞功能。接种可预防脾细胞死亡和淋巴细胞功能下降。细胞裂解和淋巴细胞功能下降不能完全解释 MDV-IS。
