Most species of the genus Bifidobacterium contain the gene cluster PFNA, which is presumably involved in the species-specific communication between bacteria and their hosts. The gene cluster PFNA consists of five genes including fn3, which codes for a protein containing two fibronectin type III domains. Each fibronectin domain contains sites similar to cytokine-binding sites of human receptors. Based on this finding we assumed that this protein would bind specifically to human cytokines in vitro. We cloned a fragment of the fn3 gene (1503 bp; 501 aa) containing two fibronectin domains, from the strain B. longum subsp. longum GT15. After cloning the fragment into the expression vector pET16b and expressing it in E. coli, the protein product was purified to a homogenous state for further analysis. Using the immunoferment method, we tested the purified fragment’s ability to bind the following human cytokines: IL-1β, IL-6, IL-10, TNFα. We developed a sandwich ELISA system to detect any specific interactions between the purified protein and any of the studied cytokines. We found that the purified protein fragment only binds to TNFα.

双歧杆菌属的大多数物种都包含基因簇PFNA，该基因簇可能与细菌与其宿主之间的物种特异性通讯有关。PFNA基因簇由五个基因组成，其中包括fn3，其编码包含两个纤连蛋白III型结构域的蛋白质。每个纤连蛋白结构域包含与人受体的细胞因子结合位点相似的位点。基于此发现，我们认为该蛋白在体外能与人细胞因子特异性结合。我们从长双歧杆菌菌株中克隆了含有两个纤连蛋白结构域的fn3基因片段（1503 bp；501aa）。长GT15。将片段克隆到表达载体pET16b中并在大肠杆菌中表达后，将蛋白产物纯化至均质状态以进行进一步分析。使用免疫发酵方法，我们测试了纯化的片段结合以下人类细胞因子的能力：IL-1β，IL-6，IL-10，TNFα。我们开发了一种夹心ELISA系统，以检测纯化的蛋白质与任何研究的细胞因子之间的任何特异性相互作用。我们发现纯化的蛋白片段仅结合TNFα。