Antimicrobial peptide LL-37 forms complex with bacterial DNA to facilitate blood translocation of bacterial DNA and aggravate ulcerative colitis

Bacterial DNA(bacDNA) is frequently found in serum of patient with ulcerative colitis(UC) and Crohn's disease, even blood bacterial culture is negative. How bacDNA evades immune elimination and is translocated into blood remain unclear. Here, we showed that bacDNA avoids elimination and disables bacteriakilling function of antimicrobial peptide LL-37(Cramp in mice) by forming complex with LL-37, which is inducible after culture with bacteria or bacterial products. Elevated LL-37-bacDNA complex was found in plasma and lesions of patients with UC. LL-37-bacDNA promoted inflammation by inducing Th1, Th2 and Th17 differentiation and activating toll-like receptor-9(TLR9). The complex also increased paracellular permeability, which possibly combines its inflammatory effects to promote local damage and bacDNA translocation into blood. Cramp-bacDNA aggravated mouse colitis severity while interference with the complex ameliorated the disease. The study identifies that inflammatogenic bacDNA utilizes LL-37 as a vehicle for blood translocation and to evade immune elimination. Additionally, bacteria may make a milieu by releasing bacDNA to utilize and resist host antimicrobial peptides as a ‘trojan horse'.

High-throughput screening and evaluation of repurposed drugs targeting the SARS-CoV-2 main protease

Dear editor,To date,a number of clinically approved drugs have been evaluated for potential to treat coronavirus disease 2019(COVID-19),such as lopinavir/ritonavir,hydroxychloroquine,cobicistat,and darunavir.Some of these drugs have been proven to be effective in vitro;however,clinical trials showed that none of these compounds led to a significant improvement in symptoms or length of hospitalization.Thus,it is essential and more reliable to start from a defined target to ide ntify can didate drugs.