Houston Simon, Schovanek Ethan, Conway Kate M E, Mustafa Sarah, Gomez Alloysius, Ramaswamy Raghavendran, Haimour Ayman, Boulanger Martin J, Reynolds Lisa A, Cameron Caroline E
Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada.
Division of Allergy and Infectious Diseases, Department of Medicine, University of Washington, Seattle, WA, United States.
Front Microbiol. 2022 May 3;13:888525. doi: 10.3389/fmicb.2022.888525. eCollection 2022.
The etiological agent of syphilis, ssp. , is a highly invasive "stealth" pathogen that can evade the host immune response and persist within the host for decades. This obligate human pathogen is adept at establishing infection and surviving at sites within the host that have a multitude of competing microbes, sometimes including pathogens. One survival strategy employed by bacteria found at polymicrobial sites is elimination of competing microorganisms by production of antimicrobial peptides (AMPs). Antimicrobial peptides are low molecular weight proteins (miniproteins) that function directly via inhibition and killing of microbes and/or indirectly via modulation of the host immune response, which can facilitate immune evasion. In the current study, we used bioinformatics to show that approximately 7% of the proteome is comprised of miniproteins of 150 amino acids or less with unknown functions. To investigate the possibility that AMP production is an unrecognized defense strategy used by during infection, we developed a bioinformatics pipeline to analyze the complement of miniproteins of unknown function for the identification of potential AMPs. This analysis identified 45 AMP candidates; of these, Tp0451a and Tp0749 were subjected to further bioinformatic analyses to identify AMP critical core regions (AMPCCRs). Four potential AMPCCRs from the two predicted AMPs were identified and peptides corresponding to these AMPCCRs were experimentally confirmed to exhibit bacteriostatic and bactericidal activity against a panel of biologically relevant Gram-positive and Gram-negative bacteria. Immunomodulation assays performed under inflammatory conditions demonstrated that one of the AMPCCRs was also capable of differentially regulating expression of two pro-inflammatory chemokines [monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8)]. These findings demonstrate proof-of-concept for our developed AMP identification pipeline and are consistent with the novel concept that expresses AMPs to defend against competing microbes and modulate the host immune response.
梅毒病原体苍白密螺旋体亚种是一种具有高度侵袭性的“隐匿”病原体，它能够逃避宿主的免疫反应，并在宿主体内持续存在数十年。这种专性人类病原体善于在宿主体内存在大量竞争性微生物（有时包括病原体）的部位建立感染并存活。在多微生物部位发现的细菌所采用的一种生存策略是通过产生抗菌肽（AMPs）来消除竞争性微生物。抗菌肽是低分子量蛋白质（微型蛋白质），其功能直接通过抑制和杀死微生物和/或间接通过调节宿主免疫反应来实现，这可以促进免疫逃逸。在本研究中，我们使用生物信息学表明，在该蛋白质组中，约7%由150个氨基酸或更少且功能未知的微型蛋白质组成。为了研究产生AMPs是否是梅毒螺旋体在感染期间使用的一种未被认识的防御策略，我们开发了一种生物信息学流程，以分析功能未知的梅毒螺旋体微型蛋白质的互补序列，用于鉴定潜在的AMPs。该分析鉴定出45个梅毒螺旋体AMPs候选物；其中，Tp0451a和Tp0749进行了进一步的生物信息学分析，以鉴定AMPs关键核心区域（AMPCCRs）。从这两种预测的AMPs中鉴定出四个潜在的AMPCCRs，并且与这些AMPCCRs相对应的肽经实验证实对一组生物学相关的革兰氏阳性和革兰氏阴性细菌具有抑菌和杀菌活性。在炎症条件下进行的免疫调节试验表明，其中一个AMPCCRs还能够差异调节两种促炎趋化因子[单核细胞趋化蛋白-1（MCP-1）和白细胞介素-8（IL-8）]的表达。这些发现证明了我们开发的AMPs鉴定流程的概念验证，并且与梅毒螺旋体表达AMPs以抵御竞争性微生物并调节宿主免疫反应的新概念一致。
