NMO-IgG/anti-AQP4抗体的检测及其特异性的研究

Detection of NMO-IgG or anti-AQP4 antibodies:a specifity challenge

目的 NMO-IgG/anti-AQP4抗体已被多数研究证实为是视神经脊髓炎(NMO)或其疾病谱的一种特异性抗体。然而,该抗体的特异性尚未在中枢神经系统(CNS)感染性疾病中做过特异性的测试。本研究的目的是检测结核性脑膜炎(TBM)患者血清中是否有NMO-IgG/anti-AQP4抗体的表达,并和NMO疾病谱进行比较。方法建立常规NMO-IgG检测的间接免疫荧光法(IIF)和检测AQP4-Ab的细胞分析法(CBA)。IIF法以鼠脑为底物检测NMO-IgG,并测定其滴度,同时应用免疫双标法验证NMO-IgG与AQP4-Ab分布的一致性。应用CBA法检测患者血清中AQP4-Ab的表达情况。盲法检测血清172例,其中NMO24例,纵形扩展性脊髓炎(LETM)22例,多发性硬化(MS)30例,TBM46例,肺结核患者30例,健康对照20例;对其检测的阳性率进行分析。结果研究发现NMO-IgG/anti-AQP4抗体不仅存在于NMO疾病谱中,在TBM患者血清中也可以普遍检测到该抗体。NMO-IgG的血清阳性率分别为:TBM76.1%(35/46),NMO62.5%(15/24),LETM59.1%(13/22);TBM组抗体滴度明显高于NMO组和LETM组。CBA法检测的血清阳性率分别为:TBM91.3%(42/46),NMO91.7%(22/24),LETM86.4%(19/22)。肺结核、MS和健康对照血清阳性率很低。结论本研究结果显示,CNS结核感染可导致NMO-IgG/anti-AQP4抗体的产生。该发现使传统的NMO-IgG/AQP4-Ab为疾病特异性抗体的观念受到挑战,提示该抗体可能是反映CNS破坏性脱髓鞘的生物学标记。

Objective Antibody against aquaporin-4 （ AQP4） is a validated specific biomarker for the neuromyelitis optica （ NMO） spectrum disorders. However,the specifity of NMO-IgG/anti-AQP4 has not been systemically tested in CNS infectious diseases. This study was undertaken to investigate whether anti-AQP4 antibody is present in patients with tuberculous meningitis （ TBM） and to compare different assays for assessing the seroprevalence of anti-AQP4 antibodies in patients with TBM and NMO spectrum disorders. Methods We set up the conventional NMO-IgG assay,based on indirect immunofluorescent （ IIF） reactivity with mouse brain cryosections,and an AQP4-transfected cell-based assay （ CBA）. IIF we characterized further by dual immunostaining,and the antibody titers were also analyzed. Both assays were used in parallel to test seropositivity of masked serum samples from patients with neuromyelitis optica （ NMO,24） ,longitudinally extensive transverse myelitis （ LETM,22） ,multiple sclerosis （ MS,30） ,pulmonary tuberculosis （ PTB,30 ） ,tuberculosis meningitis （ TBM,46 ） and healthy controls （ HC,20 ）. Results Serum NMO-IgG/anti-AQP4 antibody was not exclusively restricted to patients with NMO spectrum disorders. The antibody was detected in the majority of serum samples from TBM patients,and titers ofanti-AQP4 IgG in TBM patients were higher than that in those with confirmed NMO and LTEM. Using the IIF assay,seropositivity rates for NMO-IgG were 76. 1% （ 35 /46） for TBM patients,62. 5% （ 15 /24） for NMO patients,and 59. 1% （ 13 /22） for LETM. Using cell-based assays we found antibodies to AQP4 in 91. 3% （ 42 /46） of TBM patients,91. 7% （ 22 /24） for NMO patients,and 86. 4% （ 19 /22） for LETM. PTB,MS,and HC all had low rates of anti-AQP4 IgG seropositivity in these assays. Conclusions The data we present suggests that aquaporin-4 autoimmunity may reflect a CNS mycobacteria-initiated immune response. This findings challenge the classic view that NMO-IgG is a disease-specific antibody,and suggests NMO-IgG/anti-AQP4 may be a marker of destructive demyelination.