Assessing the infiltration of immune cells in the upper trachea mucosa after infectious laryngotracheitis virus (ILTV) vaccination and challenge

The types of immune cells that populate the trachea after ILTV vaccination and infection have not been assessed. The objective of this study was to quantify CD4+, CD8α+, CD8β+, TCRγδ+, and MRC1LB+ cells that infiltrate the trachea after vaccination with chicken embryo origin (CEO), tissue culture origin (TCO), and recombinant herpesvirus of turkey-laryngotracheitis (rHVT-LT) vaccines, and after challenge of vaccinated and non-vaccinated chickens with a virulent ILTV strain. Eye-drop vaccination with CEO, or TCO, or in ovo vaccination with rHVT-LT did not alter the number of CD4+, CD8α+, CD8β+, TCRγδ+, and MRC1LB+ cells in the trachea. After challenge, the CEO vaccinated group of chickens showed swift clearance of the challenge virus, the mucosa epithelium of the trachea remained intact, and a limited number of CD4+, CD8α+, and CD8β+ cells were detected in the upper trachea mucosa. The TCO and rHVT-LT vaccinated groups of chickens showed narrow viral clearance with moderate disruption of the trachea epithelial integrity, and a significant increase in CD4+, CD8α+, CD8β+, and TCRγδ+ cells infiltrated the upper trachea mucosa. Non-vaccinated challenged chickens showed high levels of viral replication, the epithelial organization of the upper trachea mucosa was heavily disrupted, and the predominant infiltrates were CD4+, TCRγδ+, and MRC1LB+ cells. Hence, the very robust protection provided by CEO vaccination was characterized by minimal immune cell infiltration to the trachea mucosa. In contrast, partial protection induced by the TCO and rHVT-LT vaccines requires a prolonged period of T cell expansion to overcome the established infection in the trachea mucosa.

目前尚未有研究评估鸡传染性喉气管炎病毒（Infectious Laryngotracheitis Virus, ILTV）疫苗接种与攻毒后，气管内定植的免疫细胞类型。本研究旨在定量检测接种鸡胚源（chicken embryo origin, CEO）、组织培养源（tissue culture origin, TCO）及重组火鸡疱疹病毒-喉气管炎（recombinant herpesvirus of turkey-laryngotracheitis, rHVT-LT）疫苗后，以及免疫鸡与非免疫鸡经强毒ILTV攻毒后，气管内浸润的CD4⁺、CD8α⁺、CD8β⁺、TCRγδ⁺及MRC1LB⁺细胞数量。经眼滴接种CEO或TCO疫苗，或经卵内接种rHVT-LT疫苗，均未改变气管内CD4⁺、CD8α⁺、CD8β⁺、TCRγδ⁺及MRC1LB⁺细胞的数量。攻毒后，CEO疫苗免疫组鸡只可快速清除攻毒病毒，气管黏膜上皮保持完整，仅在上气管黏膜中检测到少量CD4⁺、CD8α⁺及CD8β⁺细胞。TCO与rHVT-LT疫苗免疫组鸡只的病毒清除效率有限，气管上皮完整性出现中度破坏，且上气管黏膜中浸润的CD4⁺、CD8α⁺、CD8β⁺及TCRγδ⁺细胞数量显著升高。非免疫攻毒组鸡只则表现出高水平的病毒复制，上气管黏膜的上皮结构严重受损，浸润的主要免疫细胞为CD4⁺、TCRγδ⁺及MRC1LB⁺细胞。由此可见，CEO疫苗所提供的极强保护力，其特征为气管黏膜仅出现极少量免疫细胞浸润。与之相反，TCO与rHVT-LT疫苗诱导的部分保护力，需要经过较长时间的T细胞扩增以清除气管黏膜内已建立的感染。