Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.
Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, 9297University of Brescia, Brescia, Italy.
Clin Chem Lab Med. 2024 Feb 27;62(10):1980-1990. doi: 10.1515/cclm-2023-1348. Print 2024 Sep 25.
Alpha-1-antitrypsin deficiency is a genetic disorder caused by mutations in the gene encoding alpha-1-antitrypsin (AAT), the major serine protease inhibitor in plasma. Reduced AAT levels are associated with elevated risk of developing emphysema mainly due to uncontrolled activity of neutrophil elastase in the lungs. The prevalent Z-AAT mutant and many rare pathogenic AAT variants also predispose to liver disease due to their accumulation as polymeric chains in hepatocytes. Part of these polymers are secreted into the bloodstream and could represent biomarkers of intra-hepatic accumulation. Moreover, being inactive, they further lower lung protection against proteases. Aim of our study is to accurately quantify the percentage of circulating polymers (CP) in a cohort of subjects with different genotypes.
CP concentration was measured in plasma or Dried Blood Spot (DBS) by a sensitive sandwich ELISA based on capture by the polymer-specific 2C1 monoclonal antibody.
CP were significantly elevated in patients with the prevalent PISZ and PIZZ genotypes, with considerable intra-genotype variability. Notably, higher percentage of polymers was observed in association with elevated C-reactive protein. CP levels were also increased in carriers of the M variant, and of M, I, P and M in heterozygosity with Z-AAT.
These findings highlight the importance of implementing CP quantification in a clinical laboratory. Indeed, the variable amount of CP in patients with the same genotype may correlate with the variable severity of the associated lung and liver diseases. Moreover, CP can reveal the polymerogenic potential of newly discovered ultrarare AAT variants.
α-1-抗胰蛋白酶缺乏症是一种由编码α-1-抗胰蛋白酶（AAT）的基因突变引起的遗传疾病，AAT 是血浆中主要的丝氨酸蛋白酶抑制剂。AAT 水平降低与肺气肿发病风险增加有关，主要原因是肺部中性粒细胞弹性蛋白酶活性失控。常见的 Z-AAT 突变体和许多罕见的致病性 AAT 变体也易导致肝脏疾病，因为它们在肝细胞中积累为聚合链。这些聚合物的一部分被分泌到血液中，可能代表肝内蓄积的生物标志物。此外，由于它们无活性，进一步降低了肺对蛋白酶的保护作用。我们研究的目的是准确量化不同基因型患者循环聚合物（CP）的百分比。
通过基于聚合物特异性 2C1 单克隆抗体捕获的敏感夹心 ELISA 在血浆或干血斑（DBS）中测量 CP 浓度。
在常见的 PISZ 和 PIZZ 基因型患者中，CP 显著升高，且具有较大的基因型内变异性。值得注意的是，与 C 反应蛋白升高相关时，观察到更高比例的聚合物。M 变体携带者、M、I、P 和 M 杂合子与 Z-AAT 携带者的 CP 水平也升高。
这些发现强调了在临床实验室中实施 CP 定量的重要性。事实上，同一基因型患者中 CP 的不同含量可能与相关肺和肝病的不同严重程度相关。此外，CP 可以揭示新发现的超罕见 AAT 变体的聚合物生成潜力。
