Lamontagne L, Page C, Larochelle R, Longtin D, Magar R
Dépt. des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888 Succ. Centre-Ville, Montréal, Quebec, Canada H3C 3P8.
Vet Immunol Immunopathol. 2001 Oct;82(3-4):165-82. doi: 10.1016/s0165-2427(01)00335-x.
Porcine reproductive and respiratory syndrome virus (PRRSV) induces a persistent viral infection associated with an inefficient humoral immune response. A study of lymphoid B cells and specific humoral immune response was performed in blood and several lymphoid organs collected from PRRSV experimentally-infected pigs. Groups of specific pathogen-free (SPF) pigs were infected with the LHVA-93-3 isolate of PRRSV, and blood, tonsils, spleen and mediastinal lymph nodes (MLN) were collected at various times postinfection (p.i.) (3-60 days). Lymphoid cells were isolated, immunolabeled for cytofluorometric determination of B cell percentages, used for counting specific anti-PRRSV antibody secreting B cells by an ELISPOT assay, or cultured for metabolic activity. The presence of anti-PRRSV antibodies in the serum of infected pigs was determined using a commercial ELISA assay. Virus detection was performed in all tissues, including lungs, by virus isolation and RT-PCR. The results show that percentages of B cells increased in tonsils as soon as 3 days until 17 days p.i. in PRRSV-infected pigs while they increased in spleen at 3 days p.i. only, due to an increase of larger Ig(high)-producing B cells. Metabolic activity of lymphoid cells from blood and spleen increased at 3 days p.i. only while lymphoid cells from tonsils and MLN transiently decreased at that time and increased thereafter up to 60 days p.i. Anti-PRRSV antibody-secreting B cells occurred in tonsils after 10 days p.i. and strongly increased up to 60 days p.i. However, specific anti-PRRSV-secreting B cells were detected in blood and spleen after 17 days p.i and in MLN only after 45 days p.i. Specific antibodies were detectable in serum at 10 days p.i., reached the maximum level at 45 days and remained high up to 60 days p.i. Infectious virus was detected in lungs and MLN as soon as 3 days p.i., and remained detectable up to 45 days p.i. in tonsils of one pig while viral RNA was detected in most organs up to 60 days p.i. In vitro experiments revealed that inactivated virus induced a stimulation of lymphoid cells isolated from PRRSV-infected pigs while it was cytotoxic for lymphoid cells from control pigs. Taken together, these results indicate that viral infection induced simultaneously a polyclonal activation of B cells, mainly in tonsils, and an exaggerated and prolonged specific humoral immune response due to persistent viral infection in lymphoid organs.
猪繁殖与呼吸综合征病毒（PRRSV）可引发持续的病毒感染，并伴有低效的体液免疫反应。本研究对从经PRRSV实验感染的猪身上采集的血液和多个淋巴器官中的B淋巴细胞及特异性体液免疫反应进行了研究。将特定病原体-free（SPF）猪分组，用PRRSV的LHVA - 93 - 3分离株进行感染，并在感染后不同时间点（3 - 60天）采集血液、扁桃体、脾脏和纵隔淋巴结（MLN）。分离淋巴细胞，进行免疫标记以通过细胞荧光测定法确定B细胞百分比，通过ELISPOT试验计数分泌特异性抗PRRSV抗体的B细胞，或进行培养以检测代谢活性。使用商业ELISA检测法测定感染猪血清中抗PRRSV抗体的存在情况。通过病毒分离和RT - PCR在包括肺在内的所有组织中进行病毒检测。结果显示，在PRRSV感染的猪中，感染后3天至17天，扁桃体中的B细胞百分比立即增加，而脾脏中仅在感染后3天B细胞百分比增加，这是由于产生较大Ig(高)的B细胞数量增加所致。血液和脾脏中的淋巴细胞代谢活性仅在感染后3天增加，而扁桃体和MLN中的淋巴细胞在此时短暂减少，之后直至感染后60天增加。感染后10天，扁桃体中出现分泌抗PRRSV抗体的B细胞，并在感染后60天强烈增加。然而，感染后17天在血液和脾脏中检测到分泌特异性抗PRRSV的B细胞，在MLN中仅在感染后45天检测到。感染后10天血清中可检测到特异性抗体，在45天达到最高水平，并在感染后60天一直保持高水平。感染后3天在肺和MLN中检测到传染性病毒，在一头猪的扁桃体中直至感染后45天仍可检测到，而在大多数器官中直至感染后60天可检测到病毒RNA。体外实验表明，灭活病毒可刺激从PRRSV感染猪分离的淋巴细胞，而对对照猪的淋巴细胞具有细胞毒性。综上所述，这些结果表明病毒感染同时诱导了B细胞的多克隆激活，主要发生在扁桃体中，并且由于淋巴器官中的持续病毒感染导致特异性体液免疫反应过度且延长。
