Department of Animal Health, NEIKER-Tecnalia, Derio, Bizkaia, Spain.
PLoS One. 2013 May 28;8(5):e64568. doi: 10.1371/journal.pone.0064568. Print 2013.
Mycobacterium avium subsp. paratuberculosis (MAP) infection causes a chronic granulomatous inflammatory regional enteritis in ruminants. Cell-mediated immune responses are assumed to be protective and therefore, to be associated with its more delimited lesion types, while humoral responses are mainly associated with diffuse histopathological lesions. However, this duality of immune responses has been recently questioned. The aim of this study was to assess the relationship between both types of immunological responses and the type and extension of intestinal lesions and the presence of MAP in bovine tissues. Standard histopathological examinations, two microbiological procedures (culture and real time PCR (rtPCR)), as well as MAP specific antibody and interferon gamma (IFN-γ) release assays (IGRA) were performed on tissues and blood of 333 slaughtered Holstein-Friesian animals. Paratuberculous lesions were observed in 176 (52.9%) of the animals and overall MAP detection rates were estimated at 13.5% and 28.5% for tissue culture and rtPCR, respectively. Unlike the relatively constant non-specific IFN-γ release, both the antibody levels and the specific IFN-γ release significantly increased with tissue damage. Delimited immunopathological forms, which accounted for 93.2% of all forms, were mostly related to positive testing in the IGRA (38.4%) whereas diffuse ones (6.8%) were associated with antibody seropositivity (91.7%). However, since the frequency of positive immune responses in both tests increased as the lesions severity increased, polarization of Th1/Th2 responses was less prominent than expected. MAP was detected in the majority of ELISA-positive animals (culture+: 90%, rtPCR+: 85%) but the bacteria was only confirmed in the 36.1% of IGRA-positive animals by any of the two microbiological tests. In terms of diagnosis, the antibody test was a good indicator of advanced tissue damage (diffuse forms), but the IGRA did not associate well with more delimited forms or with MAP detection.
分支杆菌 avium subsp. 副结核（MAP）感染引起反刍动物慢性肉芽肿性区域性肠炎。细胞介导的免疫反应被认为是保护性的，因此与更有限的病变类型相关，而体液反应主要与弥漫性组织病理学病变相关。然而，这种免疫反应的双重性最近受到了质疑。本研究旨在评估两种类型的免疫反应与肠道病变的类型和程度以及牛组织中 MAP 的存在之间的关系。对 333 头荷斯坦-弗里森屠宰动物的组织和血液进行了标准组织病理学检查、两种微生物学程序（培养和实时 PCR（rtPCR））以及 MAP 特异性抗体和干扰素 γ（IFN-γ）释放测定（IGRA）。在 176 头（52.9%）动物中观察到副结核病变，组织培养和 rtPCR 的总体 MAP 检测率分别估计为 13.5%和 28.5%。与相对恒定的非特异性 IFN-γ释放不同，抗体水平和特异性 IFN-γ释放均随组织损伤而显著增加。占所有形式 93.2%的限定性免疫病理学形式主要与 IGRA 检测呈阳性（38.4%）相关，而弥漫性形式（6.8%）与抗体血清阳性（91.7%）相关。然而，由于两种检测中阳性免疫反应的频率随着病变严重程度的增加而增加，Th1/Th2 反应的极化程度不如预期的明显。在 ELISA 阳性动物中，大多数（培养阳性：90%，rtPCR 阳性：85%）都检测到了 MAP，但在任何两种微生物学检测中，仅 36.1%的 IGRA 阳性动物证实了细菌的存在。就诊断而言，抗体试验是组织损伤（弥漫性病变）的良好指标，但 IGRA 与更有限的病变形式或 MAP 检测相关性不佳。
