A spacer design strategy for CRISPR-Cas12f1 with single-nucleotide polymorphism mutation resolution capability and its application in the mutations diagnosis of pathogens.

Infectious diseases remain a major global issue in public health. It is important to develop rapid, sensitive, and accurate diagnostic methods to detect pathogens and their mutations. Cas12f1 is an exceptionally compact RNA-guided nuclease and have the potential to fulfill the clinical needs. Based on the interaction between crRNA-SSDNA binary sequence and Cas12f1, here, we addressed the essential features that determine the recognition ability of CRISPR-Cas12f1 single-nucleotide polymorphism (SNP), such as the length of spacer region and the base pairing region that determines the trans-cleavage of ssDNA. A fine-tuning spacer design strategy is also proposed to enhance the SNP recognition capability of CRISPR-Cas12f1. The optimized spacer confers the Cas12f1 system a strong SNP identification capability for viral or bacterial drug-resistance mutations, with a specificity ratio ranging from 19.63 to 110.20 and an admirable sensitivity up to 100  copy/µL. Together, the spacer screening and CRISPR-Cas12f1 based SNP identification method, is sensitive and versatile, and will have a wide application prospect in pathogen DNA mutation diagnosis and other mutation profiling.

Inhibiting pyroptosis: novel immune evasion strategies for pathogens.

Pyroptosis is a type of programmed cell death mediated by the Gasdermin family. It is triggered in response to pathogen infection or other danger signals. The activation of Gasdermins leads to pyroptosis and the release of large amounts of inflammatory cytokines. Pyroptosis plays a crucial role in combating pathogen infections, as it helps to eliminate infected cells and activate the immune system. However, pathogens have already developed sophisticated strategies to evade or inhibit pyroptosis, allowing them to persist and facilitate infection. This review provides an overview of the discovery of pyroptosis and its importance in anti-infectious immunity. We also discuss several new strategies for inhibiting pyroptosis by pathogens. A thorough learning of the occurrence and regulation of pyroptosis may reveal the pathogenesis of related infectious diseases and contribute to developing effective anti-infective therapeutic strategies.

Mycobacterium tuberculosis Rv2387 Facilitates Mycobacterial Survival by Silencing TLR2/p38/JNK Signaling.

Mycobacterium tuberculosis (Mtb) can evade antimicrobial immunity and persist within macrophages by interfering with multiple host cellular functions through its virulence factors, causing latent tuberculosis. The Rv2387 protein has been identified as a putative effector that potentially participates in Mtb pathogenicity. To explore the role of the Rv2387 protein in host-mycobacteria interactions, we established recombinant M. smegmatis strains and RAW264.7 cell lines that stably express the Rv2387 protein. We found that this protein suppresses mycobacteria infection-induced macrophage apoptosis by inactivating caspase-3/-8, thus facilitating the intracellular survival of mycobacteria. In addition, Rv2387 inhibits the production of inflammatory cytokines in macrophages by specifically suppressing TLR2-dependent stimulation of p38 and JNK MAPK pathways. Moreover, we further determined that the Rv2387 protein conferred a growth advantage over recombinant M. smegmatis and suppressed the inflammatory response in a mouse infection model. Overall, these data suggested that Rv2387 facilitates mycobacteria to escape host immunity and might be an essential virulence factor in Mtb.

Deficiency of GntR Family Regulator MSMEG_5174 Promotes Mycobacterium smegmatis Resistance to Aminoglycosides via Manipulating Purine Metabolism.

The increasing incidence of drug-resistant tuberculosis is still an emergency for global public health and a major obstacle to tuberculosis treatment. Therefore, deciphering the novel mechanisms of mycobacterial antibiotic resistance is crucial for combatting the rapid emergence of drug-resistant strains. In this study, we identified an unexpected role of Mycobacterium smegmatis GntR family transcriptional regulator MSMEG_5174 and its homologous gene Mycobacterium tuberculosis Rv1152 in aminoglycoside antibiotic resistance. Deficiency of MSMEG_5174 rendered Mycobacterium smegmatis highly resistant to aminoglycoside antibiotic treatment, and ectopic expression of Rv1152 in MSMEG_5174 mutants restored antibiotic-induced bacterial killing. We further demonstrated that MSMEG_5174 negatively regulates the expression of purine metabolism-related genes and the accumulation of purine metabolites. Moreover, overexpression of xanthine dehydrogenase MSMEG_0871 or xanthine treatment elicited a significant decrease in aminoglycoside antibiotic lethality for Mycobacterium smegmatis. Together, our findings revealed MSMEG_5174 as a metabolic regulator and hint toward unexplored crosstalk between purine metabolism and antibiotic resistance.

Streptococcal pyrogenic exotoxin B cleaves GSDMA and triggers pyroptosis.

Gasdermins, a family of five pore-forming proteins (GSDMA-GSDME) in humans expressed predominantly in the skin, mucosa and immune sentinel cells, are key executioners of inflammatory cell death (pyroptosis), which recruits immune cells to infection sites and promotes protective immunity1,2. Pore formation is triggered by gasdermin cleavage1,2. Although the proteases that activate GSDMB, C, D and E have been identified, how GSDMA-the dominant gasdermin in the skin-is activated, remains unknown. Streptococcus pyogenes, also known as group A Streptococcus (GAS), is a major skin pathogen that causes substantial morbidity and mortality worldwide3. Here we show that the GAS cysteine protease SpeB virulence factor triggers keratinocyte pyroptosis by cleaving GSDMA after Gln246, unleashing an active N-terminal fragment that triggers pyroptosis. Gsdma1 genetic deficiency blunts mouse immune responses to GAS, resulting in uncontrolled bacterial dissemination and death. GSDMA acts as both a sensor and substrate of GAS SpeB and as an effector to trigger pyroptosis, adding a simple one-molecule mechanism for host recognition and control of virulence of a dangerous microbial pathogen.

The Lysosomal Rag-Ragulator Complex Licenses RIPK1 and Caspase-8-mediated Pyroptosis by Yersinia.

Host cells initiate cell death programs to limit pathogen infection. Inhibition of transforming growth factor-ß-activated kinase 1 (TAK1) by pathogenic Yersinia in macrophages triggers receptor-interacting serine/threonine-protein kinase 1 (RIPK1)-dependent caspase-8 cleavage of gasdermin D (GSDMD) and inflammatory cell death (pyroptosis). A genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) screen to uncover mediators of caspase-8-dependent pyroptosis identified an unexpected role of the lysosomal FLCN-FNIP2-Rag-Ragulator supercomplex, which regulates metabolic signalling and the mechanistic target of rapamycin complex 1 (mTORC1). In response to Yersinia infection, FADD, RIPK1 and caspase-8 were recruited to Rag-Ragulator, causing RIPK1 phosphorylation and caspase-8 activation. Pyroptosis activation depended on Rag GTPase activity and lysosomal tethering of Rag-Ragulator, but not mTORC1. Thus, the lysosomal metabolic regulator Rag-Ragulator instructs the inflammatory response to Yersinia.

Mycobacterial ethambutol responsive genes and implications in antibiotics resistance.

Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis (TB), remains a formidable threat in mortality and morbidity worldwide. Ethambutol (EMB) is one of the first-line drugs regimens for TB treatment. Arabinosyl transferases are established targets of EMB, which is involved in the biosynthesis of arabinogalactan (AG) and lipoarabinomannan (LAM). Mutations among embCAB operon are responsible for around 70% clinical EMB resistant M. tuberculosis. In this review, we summarised other potential factors associated with EMB resistance via analysing whole genome, proteome and transcriptome of M. tuberculosis exposed to EMB. This will help to design better diagnosis of EMB resistance.

Mycobacterium tuberculosis Rv0341 Promotes Mycobacterium Survival in In Vitro Hostile Environments and within Macrophages and Induces Cytokines Expression.

Mycobacterium tuberculosis represents an ancient deadly human pathogen that can survive and multiply within macrophages. The effectors are key players for the successful pathogenesis of this bacterium. M. tuberculosis open reading frame (ORF) Rv0341, a pathogenic mycobacteria-specific gene, was found to be upregulated in macrophages isolated from human tuberculosis granuloma and inside the macrophages during in vitro infection by M. tuberculosis. To understand the exact role of this gene, we expressed the Rv0341 gene in M. smegmatis, which is a non-pathogenic Mycobacterium. We found that Rv0341 expression can alter colony morphology, reduce the sliding capability, and decrease the cell wall permeability of M. smegmatis. Furthermore, Rv0341 remarkably enhanced M. smegmatis survival within macrophages and under multiple in vitro stress conditions when compared with the control strain. Ms_Rv0341 significantly induced expression of TNF-α, IL-1ß, and IL-10 compared with M. smegmatis harboring an empty vector. In summary, these data suggest that Rv0341 is one of the M. tuberculosis virulence determinants that can promote bacilli survival in harsh conditions and inside macrophages.

Gasdermins: pore-forming activities and beyond.

Gasdermins (GSDMs) belong to a protein superfamily that is found only in vertebrates and consists of GSDMA, GSDMB, GSDMC, GSDMD, DFNA5 (a.k.a. GSDME) and DFNB59 (a.k.a. Pejvakin (PJVK)) in humans. Except for DFNB59, all members of the GSDM superfamily contain a conserved two-domain structure (N-terminal and C-terminal domains) and share an autoinhibitory mechanism. When the N-terminal domain of these GSDMs is released, it possesses pore-forming activity that causes inflammatory death associated with the loss of cell membrane integrity and release of inflammatory mediators. It has also been found that spontaneous mutations occurring in the genes of GSDMs have been associated with the development of certain autoimmune disorders, as well as cancers. Here, we review the current knowledge of the expression profile and regulation of GSDMs and the important roles of this protein family in inflammatory cell death, tumorigenesis and other related diseases.

L-lysine potentiates aminoglycosides against Acinetobacter baumannii via regulation of proton motive force and antibiotics uptake.

Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is a leading cause of hospital- and community-acquired infections. Acinetobacter baumannii can rapidly acquire diverse resistance mechanisms and undergo genetic modifications that confer resistance and persistence to all currently used clinical antibiotics. In this study, we found exogenous L-lysine sensitizes Acinetobacter baumannii, other Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and a Gram-positive bacterium (Mycobacterium smegmatis) to aminoglycosides. Importantly, the combination of L-lysine with aminoglycosides killed clinically isolated multidrug-resistant Acinetobacter baumannii and persister cells. The exogenous L-lysine can increase proton motive force via transmembrane chemical gradient, resulting in aminoglycoside acumination that further accounts for reactive oxygen species production. The combination of L-lysine and antibiotics highlights a promising strategy against bacterial infection.

Multiple-Scales Integrative Analysis of MicroRNAs Unveils Biomarkers and Key Regulatory Connections for Hepatocellular Carcinoma.

Hepatocellular carcinoma is the sixth most common liver cancer worldwide and the third leading cause of cancer mortality. For these reasons, early diagnostic, prognostic, and therapeutic biomarkers are extremely urgent. MicroRNAs are small noncoding single-stranded RNA molecules that are reported to be involved in a variety of physiological and pathological processes during carcinogenesis. In this study, the expression characteristics, functions, and validated targets of microRNAs in HCC were summarized and potential microRNA biomarkers were confirmed from clinical specimens. Multiple-scales integrative analysis was used to predict the diagnostic, prognostic, and therapeutic potential of microRNAs in blood and tissue of HCC patients, providing novel insight into HCC diagnosis and treatment using microRNA biomarkers.

Stem Cell-Derived Hepatocyte-Like Cells as Model for Viral Hepatitis Research.

Viral hepatitis, the leading cause of liver diseases worldwide, is induced upon infection with hepatotropic viruses, including hepatitis A, B, C, D, and E virus. Due to their obligate intracellular lifestyles, culture systems for efficient viral replication are vital. Although basic and translational research on viral hepatitis has been performed for many years, conventional hepatocellular culture systems are not optimal. These studies have greatly benefited from recent efforts on improving cell culture models for virus replication and infection studies. Here we summarize the use of human stem cell-derived hepatocyte-like cells for hepatotropic virus infection studies, including the dissection of virus-host interactions and virus-induced pathogenesis as well as the identification and validation of novel antiviral agents.

PE_PGRS62 promotes the survival of Mycobacterium smegmatis within macrophages via disrupting ER stress-mediated apoptosis.

Mycobacterium tuberculosis, the leading causative agent of tuberculosis, remains one of the most deadly infectious pathogens. PE_PGRS proteins become a new focus as their species specificity in mycobacteria, especially in pathogenic mycobacteria. Despite intensive research, PE_PGRS proteins are still a mysterious aspect of mycobacterial pathogenesis with unknown mechanism. Herein, we focused on a PE_PGRS member from M. tuberculosis, PE_PGRS62, characterized by a surface-exposed protein function in disrupting phagolysosome maturation. Expression of PE_PGRS62 in Mycobacterium smegmatis, a nonpathogenic species naturally deficient in PE_PGRS genes, resulted in enhanced resistance to various in vitro stresses and cellular survival in macrophage. As a consequence, the cytokine profiles of macrophage were disturbed and cell apoptosis were inhibited via decreasing endoplasmic reticulum stress response.

Augmenter of Liver Regeneration Protects Against Acetaminophen-Induced Acute Liver Injury in Mice by Promoting Autophagy.

Most cases of acute liver failure are caused by acetaminophen (APAP) overdose. Oxidative stress is a key factor in APAP toxicity. Although augmenter of liver regeneration (ALR) has both antioxidative and antiapoptotic effects, its therapeutic potential in APAP hepatotoxicity remains unknown. The current study assessed the protective effects and associated mechanisms of ALR against APAP-induced acute liver injury in female BALB/c mice. We found that serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, intrahepatic hemorrhage and necrosis were increased at 3, 6, 12, 24, 48, and 72 h after 600 mg/kg APAP i.p. injection. During the early stages (before 12 h) of acute liver injury, ALR levels increased significantly, followed by a decrease to control level at 24 h after APAP administration. ALR treatment increased autophagosomes, promoted the conversion of LC3 I to LC3 II, and the degradation of p62. ALR attenuated APAP-stimulated increases in ALT, AST, myeloperoxidase (MPO), malondialdehyde (MDA), and reactive oxidative species (ROS) levels; intrahepatic hemorrhage; and necrosis as well as superoxide dismutase (SOD) and Glutathione (GSH) depletion. We found that APAP caused release of the mitochondrial intermembrane proteins apoptosis-inducing factor (AIF) and cytochrome c and that ALR inhibited this change. Meanwhile, ALR decreased expression of cleaved-caspase 3 and apoptotic cells. Subsequently, we investigated the significance of autophagy in APAP-induced acute liver injury by treatment with 3-methyladenine (3-MA), which were classical pharmaceuticals for suppressing autophagy. ALR directly induced autophagy flux; and the inhibition of autophagy reversed the beneficial effects of ALR on hepatotoxicity. Our findings suggest that ALR protects against APAP hepatotoxicity by activating the autophagy pathway.

Expression and regulatory networks of Mycobacterium tuberculosis PE/PPE family antigens.

PE/PPE family antigens are distributed mainly in pathogenic mycobacteria and serve as potential antituberculosis (TB) vaccine components. Some PE/PPE family antigens can regulate the host innate immune response, interfere with macrophage activation and phagolysosome fusion, and serve as major sources of antigenic variation. PE/PPE antigens have been associated with mycobacteria pathogenesis; pe/ppe genes are mainly found in pathogenic mycobacteria and are differentially expressed between Mtb and Mycobacterium bovis. PE/PPE proteins were essential for the growth of Mtb, and PE/PPE proteins were differentially expressed under a variety of conditions. Multiple mycobacterial-virulence-related transcription factors, sigma factors, the global transcriptional regulation factor Lsr2, MprAB, and PhoPR two-component regulatory systems, and cyclic adenine monophosphate-dependent regulators, regulate the expression of PE/PPE family antigens. Multiple-scale integrative analysis revealed the expression and regulatory networks of PE/PPE family antigens underlying the virulence and pathogenesis of Mtb, providing important clues for the discovery of new anti-TB measures.

The Biology and Role of Interleukin-32 in Tuberculosis.

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading cause of morbidity and mortality globally, with nearly 10.4 million new cases of incidence and over 1.7 million deaths annually. Drug-resistant M. tuberculosis strains, especially multidrug-resistant or extensively drug-resistant strains, have further intensified the problem associated with tuberculosis control. Host-directed therapy is a promising alternative for tuberculosis control. IL-32 is increasingly recognized as an important host molecule against tuberculosis. In this review, we highlight the proinflammatory properties of IL-32 and the mode of action of IL-32 in mycobacterial infections to inspire the development of novel immunity-based countermeasures and host-directed therapies against tuberculosis.

The parasite-derived rOv-ASP-1 is an effective antigen-sparing CD4+ T cell-dependent adjuvant for the trivalent inactivated influenza vaccine, and functions in the absence of MyD88 pathway.

Vaccination remains the most cost-effective biomedical approach for controlling influenza disease. In times of pandemics, however, these vaccines cannot be produced in sufficient quantities for worldwide use by the current manufacturing capacities and practices. What is needed is the development of adjuvanted vaccines capable of inducing an adequate or better immune response at a decreased antigen dose. Previously we showed that the protein adjuvant rOv-ASP-1 augments influenza-specific antibody titers and survival after virus challenge in both young adult and old-age mice when administered with the trivalent inactivated influenza vaccine (IIV3). In this study we show that a reduced amount of rOv-ASP-1, with 40-times less IIV3 can also induce protection. Apparently the potency of the rOv-ASP-1 adjuvanted IIV3 vaccine is independent of the IIV3-specific Th1/Th2 associated antibody responses, and independent of the presence of HAI antibodies. However, CD4+ T helper cells were indispensable for the protection. Further, rOv-ASP-1 with or without IIV3 elicited the increased level of various chemokines, which are known chemoattractant for immune cells, into the muscle 4 h after immunization, and significantly induced the recruitment of monocytes, macrophages and neutrophils into the muscles. The recruited monocytes had higher expression of the activation marker MHCII on their surface as well as CXCR3 and CCR2; receptors for IP-10 and MCP-1, respectively. These results show that the rOv-ASP-1 adjuvant allows substantial antigen sparing of IIV3 by stimulating at the site of injection the accumulation of chemokines and the recruitment of immune cells that can augment the activation of CD4+ T cell immune responses, essential for the production of antibody responses. Protection elicited by the rOv-ASP-1 adjuvanted IIV3 vaccine also appears to function in the absence of MyD88-signaling. Future studies will attempt to delineate the precise mechanisms by which the rOv-ASP-1 adjuvanted IIV3 vaccine works.

Quasispecies characters of hepatitis B virus in immunoprophylaxis failure infants.

Hepatitis B vaccination prevents 80-95% of transmission and reduces the incidence of HBV in children. The variations in the a determinant of HBV surface antigen (HBsAg) have been reported to be the most prevalent cause for vaccine or antibody escape. There is a conflicting evidence on as to whether escape mutants arise de novo in infected infants or whether the mutants, that have preexisted maternally, subsequently undergo selective replication in the infant under immune pressure. Here, we report that nearly 65% (55 of 85) vaccination failure in child patients has no amino acid substitution in a determinant as seen by Sanger sequencing. We further employed an Illumina sequencing platform-based method to detect HBV quasispecies in four immunoprophylaxis failure infants and their mothers. In our data, the substitution rate of amino acid located at a determinant is relatively low (< 10%), I/T126A, C124S, F134Y, K141Q, Q129H, D144A, G145V, and N146K, which showed no statistical difference to their mothers, proving that these vaccine escape mutants preexist maternally as minor variants. Besides that, bioinformatical analysis showed that the binding affinity of high variation epitopes (amino acid divergence in mother and their infants > 20%) to related HLA molecules was generally decreased, these traces of immune escape suggesting that immune pressure was present and was effective in all samples.

Comparative analysis of prophages in Streptococcus mutans genomes.

Prophages have been considered genetic units that have an intimate association with novel phenotypic properties of bacterial hosts, such as pathogenicity and genomic variation. Little is known about the genetic information of prophages in the genome of Streptococcus mutans, a major pathogen of human dental caries. In this study, we identified 35 prophage-like elements in S. mutans genomes and performed a comparative genomic analysis. Comparative genomic and phylogenetic analyses of prophage sequences revealed that the prophages could be classified into three main large clusters: Cluster A, Cluster B, and Cluster C. The S. mutans prophages in each cluster were compared. The genomic sequences of phismuN66-1, phismuNLML9-1, and phismu24-1 all shared similarities with the previously reported S. mutans phages M102, M102AD, and ϕAPCM01. The genomes were organized into seven major gene clusters according to the putative functions of the predicted open reading frames: packaging and structural modules, integrase, host lysis modules, DNA replication/recombination modules, transcriptional regulatory modules, other protein modules, and hypothetical protein modules. Moreover, an integrase gene was only identified in phismuNLML9-1 prophages.