ABSTRACT
Objective:To understand and determine the biological properties of Chlamydia pneumonia (Cpn) hypothetical protein Cpn0423 and the mechanisms of which involved in Cpn0423-induced inflammatory response. Methods:The biological properties of Cpn0423 gene were analyzed using bioinformatic software. The subcellular localization of nucleotide-binding oligomerization domain-like receptor 2 (NOD2) in bone marrow-derived macrophages (BMDMs) was detected by confocal microscope. NOD2-siRNA was used to inhibit the expression of NOD2 at mRNA level. Cpn0423-induced macrophage inflammatory protein 2 (MIP-2) and IL-6 production in BMDMs were detected by ELISA. PCR was performed to detect Cpn0423 DNA in bronchoalveolar lavage fluid (BALF) of Cpn-positive patients.Results:The homology between Cpn0423 and other type Ⅲ secretion system effector proteins of Chlamydia ranged from 85% to 93%. NOD2-siRNA could effectively inhibit the expression of NOD2 at mRNA level in BMDMs ( P<0.001). Moreover, Cpn0423-induced production of MIP-2 [(920.5±99.1) pg/ml vs (130.1±11.5) pg/ml, P<0.001] and IL-6 [(266.2±58.4) pg/ml vs (165.7±21.5) pg/ml, P<0.001] in BMDMs were decreased following NOD2-siRNA pre-treatment. Cpn0423 DNA was detected in the BAlF of 83.3% (10/12) of Cpn-positive cases, but not in Cpn-negative cases. Conclusions:Cpn0423 induced inflammatory response in host cells through NOD2 pathway, which was closely related to the chronic inflammatory injury caused by Cpn.