Chronic Infection Model Research Articles

Prodigiosin as an Antibiofilm Agent against the Bacterial Biofilm-Associated Infection of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is known to generate bacterial biofilms that increase antibiotic resistance. With the increase of multi-drug resistance in recent years, the formulation of a new therapeutic strategy has seemed urgent. Preliminary findings show that Prodigiosin (PG), derived from chromium-resistant Serratia marcescens, exhibited efficient anti-biofilm activity against Staphylococcus aureus. However, its anti-biofilm activity against P. aeruginosa remains largely unexplored. The anti-biofilm activity of PG against three clinical single drug-resistant P. aeruginosa was evaluated using crystal violet staining, and the viability of biofilms and planktonic cells were also assessed. A model of chronic lung infection was constructed to test the in vivo antibiofilm activity of PG. The results showed that PG inhibited biofilm formation and effectively inhibited the production of pyocyanin and extracellular polysaccharides in vitro, as well as moderated the expression of interleukins (IL-1β, IL-6, IL-10) and tumor necrosis factor (TNF-α) in vivo, which might be attributed to the downregulation of biofilm-related genes such as algA, pelA, and pslM. These findings suggest that PG could be a potential treatment for drug-resistant P aeruginosa and chronic biofilm infections.

Unveiling the modulation of Pseudomonas aeruginosa virulence and biofilm formation by selective histone deacetylase 6 inhibitors.

Bacterial infections represent a key public health issue due to the occurrence of multidrug-resistant bacteria. Recently, the amount of data supporting the dynamic control of epigenetic pathways by environmental cues has triggered research efforts toward the clarification of their role in microbial infections. Among protein post-translational modifications, reversible acetylation is the most implicated in the feedback to environmental stimuli and in cellular homeostasis. Accordingly, the latest studies identified the histone deacetylase 6 (HDAC6) enzyme as a crucial player in the complex molecular machinery underlying bacterial clearance or killing. A very important milestone for the elucidation of the consequence of HDAC6 activity in bacterial infections is herein described, unveiling for the first time the role of a potent HDAC6 inhibitor in interfering with biofilm formation and modulating virulence factors of P. aeruginosa. We demonstrated that compound F2F-2020202 affected the production of some important virulence factors in P. aeruginosa, namely pyocyanin and rhamnolipids, clearly impairing its ability to form biofilm. Furthermore, evidence of possible QS involvement is supported by differential regulation of specific genes, namely RhlI, phAz1, and qsrO. The data herein obtained also complement and in part explain our previous results with selective HDAC6 inhibitors able to reduce inflammation and bacterial load in chronic infection models recapitulating the cystic fibrosis (CF) phenotype. This study fosters future in-depth investigation to allow the complete elucidation of the molecular mechanisms underlying HDAC6's role in bacterial infections.

Efficacy and Experience of Bacteriophages in Biofilm-Related Infections.

Bacterial infection has always accompanied human beings, causing suffering and death while also contributing to the advancement of medical science. However, the treatment of infections has become more complex in recent times. The increasing resistance of bacterial strains to antibiotics has diminished the effectiveness of the therapeutic arsenal, making it less likely to find the appropriate empiric antibiotic option. Additionally, the development and persistence of bacterial biofilms have become more prevalent, attributed to the greater use of invasive devices that facilitate biofilm formation and the enhanced survival of chronic infection models where biofilm plays a crucial role. Bacteria within biofilms are less susceptible to antibiotics due to physical, chemical, and genetic factors. Bacteriophages, as biological weapons, can overcome both antimicrobial resistance and biofilm protection. In this review, we will analyze the scientific progress achieved in vitro to justify their clinical application. In the absence of scientific evidence, we will compile publications of clinical cases where phages have been used to treat infections related to biofilm. The scientific basis obtained in vitro and the success rate and safety observed in clinical practice should motivate the medical community to conduct clinical trials establishing a protocol for the proper use of bacteriophages.

Neonatal CD8+ T Cells Resist Exhaustion during Chronic Infection.

Chronic viral infections, such as HIV and hepatitis C virus, represent a major public health problem. Although it is well understood that neonates and adults respond differently to chronic viral infections, the underlying mechanisms remain unknown. In this study, we transferred neonatal and adult CD8+ T cells into a mouse model of chronic infection (lymphocytic choriomeningitis virus clone 13) and dissected out the key cell-intrinsic differences that alter their ability to protect the host. Interestingly, we found that neonatal CD8+ T cells preferentially became effector cells early in chronic infection compared with adult CD8+ T cells and expressed higher levels of genes associated with cell migration and effector cell differentiation. During the chronic phase of infection, the neonatal cells retained more immune functionality and expressed lower levels of surface markers and genes related to exhaustion. Because the neonatal cells protect from viral replication early in chronic infection, the altered differentiation trajectories of neonatal and adult CD8+ T cells is functionally significant. Together, our work demonstrates how cell-intrinsic differences between neonatal and adult CD8+ T cells influence key cell fate decisions during chronic infection.

Prodrug nanotherapy demonstrates in vivo anticryptosporidial efficacy in a mouse model of chronic Cryptosporidium infection.

The gastrointestinal disease cryptosporidiosis, caused by the genus Cryptosporidium, is a common cause of diarrheal diseases in children, particularly in developing countries and frequently fatal in immunocompromised individuals. Cryptosporidium hominis (Ch)-specific bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) has been a molecular target for inhibitor design. (Note that this bifunctional enzyme has also been referred to as TS-DHFR in previous literature since the functional biochemical reaction first involves the conversion of methylene tetrahydrofolate to dihydrofolate at the TS site.) While nanomolar inhibitors of Ch DHFR-TS have been identified at the biochemical level, effective delivery of these compounds to achieve anticryptosporidial activity in cell culture and in vivo models of parasite infection remains a major challenge in developing new therapies. Previous studies, using a nanotherapy approach, have shown a promising Ch DHFR-TS inhibitor, 906, that can successfully target Cryptosporidium parasites in cell culture with nanomolar anticryptosporidial activity. This formulation utilized poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with 906 (NP-906) and conjugated with a Cryptosporidium monoclonal antibody (MAb) on the nanoparticle surface to specifically target the glycoprotein GP25-200 in excysting oocysts. However, a limitation for in vivo use is antibody susceptibility to gastric acidity. To address this gap, a prodrug diethyl ester form of 906 (MAb-NP-Prodrug) was synthesized that allowed higher compound loading in the MAb-coated PLGA nanoparticles. An oral formulation was prepared by loading lyophilized MAb-NP-Prodrug into gelatin capsules with an enteric coating for gastric stability. Proof-of-concept studies with this oral formulation demonstrated antiparasitic activity in a chronic mouse model of Cryptosporidium infection. Efficacy was observed after a low daily dose of 2 × 8 mg kg-1 for 5 days, when examined 6 and 20 days postinfection, offering a new avenue of drug delivery to be further explored.

Post-transcriptional control of the essential enzyme MurF by a small regulatory RNA in Brucella abortus.

Brucella abortus is a facultative, intracellular, zoonotic pathogen that resides inside macrophages during infection. This is a specialized niche where B. abortus encounters various stresses as it navigates through the macrophage. In order to survive this harsh environment, B. abortus utilizes post-transcriptional regulation of gene expression through the use of small regulatory RNAs (sRNAs). Here, we characterize a Brucella sRNAs called MavR (for MurF- and virulence-regulating sRNA), and we demonstrate that MavR is required for the full virulence of B. abortus in macrophages and in a mouse model of chronic infection. Transcriptomic and proteomic studies revealed that a major regulatory target of MavR is MurF. MurF is an essential protein that catalyzes the final cytoplasmic step in peptidoglycan (PG) synthesis; however, we did not detect any differences in the amount or chemical composition of PG in the ΔmavR mutant. A 6-nucleotide regulatory seed region within MavR was identified, and mutation of this seed region resulted in dysregulation of MurF production, as well as significant attenuation of infection in a mouse model. Overall, the present study underscores the importance of sRNA regulation in the physiology and virulence of Brucella.

Abstract PR01: Regulation of exhausted CD8+ T cell differentiation by IKZF transcription factors

Abstract CD8+ T cells are indispensable for pathogen and tumor clearance, although can induce immunopathology if left unrestricted. T cell exhaustion, progressively programmed in the context of persistent antigen exposure, ensures partial control while mitigating immunopathological risk. However, exhaustion is characterized by curtailed proliferative capacity, cytokine production and cytotoxic functions, which tumors and chronic pathogens exploit to persist. As such, transiently disrupting exhaustion has emerged as a therapeutic strategy for treating cancer. Exhausted cells transition through a range of differentiation states, from stem-like progenitors that mediate response to checkpoint blockade, through to terminal effector or exhausted cells. Understanding the molecular pathways moderating the exhausted states and promoting terminal exhaustion is essential for augmenting cancer immunotherapy. We identify IKZF transcription factors, Ikaros (IKZF1), Helios (IKZF2) and Aiolos (IKZF3), as key mediators of T cell exhaustion, using gene knock-out mice and a CRISPR-mediated genetic knock-out system in both chronic infection and tumor models. IKZF1 and IKZF3 are critical regulators of exhausted subset expansion, retention, phenotype and cytokine function. Strikingly, dual IKZF1 and IKZF3 ablation boosts the response of anti-tumor and anti-viral exhausted T cells, potentially via the formation of atypical exhausted T cell populations and the enrichment of functional exhausted subsets. Cumulatively, our data highlight a novel role for IKZF transcription factors in biasing exhausted T cell differentiation and provides potentially important clinical implications, directing future cancer immunotherapies targeting T cell exhaustion. Citation Format: Sinead M Reading, Isabelle Munoz, Maria Nogueira de Menezes, Nicole Y.L Saw, Krutika Ambani, Antonio Ahn, Simone Nussing, Sara Roth, Shienny Sampurno, Kelly M Ramsbottom, Joseph A Trapani, Kim L Good-Jacobson, Ricky W Johnstone, Shom Goel, Paul A Beavis, Ian A Parish. Regulation of exhausted CD8+ T cell differentiation by IKZF transcription factors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr PR01.

Thermostable Lactonases Inhibit Pseudomonas aeruginosa Biofilm: Effect In Vitro and in Drosophila melanogaster Model of Chronic Infection

Pseudomonas aeruginosa is one of the six antimicrobial-resistant pathogens known as “ESKAPE” that represent a global threat to human health and are considered priority targets for the development of novel antimicrobials and alternative therapeutics. The virulence of P. aeruginosa is regulated by a four-chemicals communication system termed quorum sensing (QS), and one main class of QS signals is termed acylhomoserine lactones (acyl-HSLs), which includes 3-Oxo-dodecanoil homoserine lactone (3-Oxo-C12-HSL), which regulates the expression of genes implicated in virulence and biofilm formation. Lactonases, like Paraoxonase 2 (PON2) from humans and the phosphotriesterase-like lactonases (PLLs) from thermostable microorganisms, are able to hydrolyze acyl-HSLs. In this work, we explored in vitro and in an animal model the effect of some lactonases on the production of Pseudomonas virulence factors. This study presents a model of chronic infection in which bacteria were administered by feeding, and Drosophila adults were treated with enzymes and the antibiotic tobramycin, alone or in combination. In vitro, we observed significant effects of lactonases on biofilm formation as well as effects on bacterial motility and the expression of virulence factors. The treatment in vivo by feeding with the lactonase SacPox allowed us to significantly increase the biocidal effect of tobramycin in chronic infection.

Microenvironment responsive charge-switchable nanoparticles act on biofilm eradication and virulence inhibition for chronic lung infection treatment

Chronic pulmonary infection caused by Pseudomonas aeruginosa (P. aeruginosa) is a common lung disease with high mortality, posing severe threats to public health. Highly resistant biofilm and intrinsic resistance make P. aeruginosa hard to eradicate, while powerful virulence system of P. aeruginosa may give rise to the recurrence of infection and eventual failure of antibiotic therapy. To address these issues, infection-microenvironment responsive nanoparticles functioning on biofilm eradication and virulence inhibition were simply prepared by electrostatic complexation between dimethylmaleic anhydride (DA) modified negatively charged coating and epsilon-poly(l-lysine) derived cationic nanoparticles loaded with azithromycin (AZI) (DA-AZI NPs). Charge reversal responsive to acidic condition enabled DA-AZI NPs to successively penetrate through both mucus and biofilms, followed by targeting to P. aeruginosa and permeabilizing its outer/inner membrane. Then in situ released AZI, which was induced by the lipase-triggered NPs dissociation, could easily enter into bacteria to take effects. DA-AZI NPs exhibited enhanced eradication activity against P. aeruginosa biofilms with a decrease of >99.999% of bacterial colonies, as well as remarkable inhibitory effects on the production of virulence factors and bacteria re-adhesion & biofilm re-formation. In a chronic pulmonary infection model, nebulization of DA-AZI NPs into infected mice resulted in prolonged retention and increased accumulation of the NPs in the infected sites of the lungs. Moreover, they significantly reduced the burden of P. aeruginosa, effectively alleviating lung tissue damages and inflammation. Overall, the proposed DA-AZI NPs highlight an innovative strategy for treating chronic pulmonary infection.

The impact of vaccine-linked chemotherapy on liver health in a mouse model of chronic Trypanosoma cruzi infection.

Chagas disease, chronic infection with Trypanosoma cruzi, mainly manifests as cardiac disease. However, the liver is important for both controlling parasite burdens and metabolizing drugs. Notably, high doses of anti-parasitic drug benznidazole (BNZ) causes liver damage. We previously showed that combining low dose BNZ with a prototype therapeutic vaccine is a dose sparing strategy that effectively reduced T. cruzi induced cardiac damage. However, the impact of this treatment on liver health is unknown. Therefore, we evaluated several markers of liver health after treatment with low dose BNZ plus the vaccine therapy in comparison to a curative dose of BNZ. Female BALB/c mice were infected with a bioluminescent T. cruzi H1 clone for approximately 70 days, then randomly divided into groups of 15 mice each. Mice were treated with a 25mg/kg BNZ, 25μg Tc24-C4 protein/ 5μg E6020-SE (Vaccine), 25mg/kg BNZ followed by vaccine, or 100mg/kg BNZ (curative dose). At study endpoints we evaluated hepatomegaly, parasite burden by quantitative PCR, cellular infiltration by histology, and expression of B-cell translocation gene 2(BTG2) and Peroxisome proliferator-activated receptor alpha (PPARα) by RT-PCR. Levels of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were quantified from serum. Curative BNZ treatment significantly reduced hepatomegaly, liver parasite burdens, and the quantity of cellular infiltrate, but significantly elevated serum levels of ALT, AST, and LDH. Low BNZ plus vaccine did not significantly affect hepatomegaly, parasite burdens or the quantity of cellular infiltrate, but only elevated ALT and AST. Low dose BNZ significantly decreased expression of both BTG2 and PPARα, and curative BNZ reduced expression of BTG2 while low BNZ plus vaccine had no impact. These data confirm toxicity associated with curative doses of BNZ and suggest that while dose sparing low BNZ plus vaccine treatment does not reduce parasite burdens, it better preserves liver health.

Immunomodulatory proteins from hookworms reduce cardiac inflammation and modulate regulatory responses in a mouse model of chronic Trypanosoma cruzi infection.

Hookworms are parasitic helminths that secrete a variety of proteins that induce anti-inflammatory immune responses, stimulating increased CD4 + Foxp3+ regulatory T cells and IL-10 production. Hookworm-derived recombinant proteins AIP-1 and AIP-2 have been shown to reduce inflammation in mouse models of inflammatory bowel disease and inflammatory airway disease by inducing CD4+Foxp3+ cells and IL-10 production. In contrast, chronic infection with the protozoal parasite Trypanosoma cruzi, the causative agent of Chagas disease, leads to chronic inflammation in tissues. Persistence of the parasites in tissues drives chronic low-grade inflammation, with increased infiltration of inflammatory cells into the heart, accompanied by increased production of inflammatory cytokines. There are no current antiparasitic drugs that effectively reduce or prevent chronic myocarditis caused by the onset of Chagas disease, thus new therapies are urgently needed. Therefore, the impact of AIP-1 and AIP-2 on myocarditis was investigated in a mouse model of chronic T. cruzi infection. Female BALB/c mice infected with bioluminescent T. cruzi H1 strain trypomastigotes for 70 days were treated once daily for 7 days with 1mg/kg AIP-1 or AIP-2 protein by intraperitoneal injection. Control mice were left untreated or treated once daily for 14 days with 25mg/kg aspirin in drinking water. At 84 days of infection, splenocytes, cardiac tissue and serum were collected for evaluation. Treatment with both AIP-1 and AIP-2 proteins significantly reduced cardiac cellular infiltration, and reduced cardiac levels of IFNγ, IL-6 and IL-2. AIP-2 treatment reduced cardiac expression of COX-2. Further, while incubation with AIP-1 and AIP-2 proteins did not induce a significant upregulation of an immunoregulatory phenotype in dendritic cells (DC), there was a modest upregulation of CD11c +CD11b+MHCII+SIRPα+ expression, suggesting a regulatory phenotype. Ex-vivo stimulation of splenocytes from the treatment groups with AIP-1 loaded DC induced reduced levels of cytotoxic and pro-inflammatory T cells, stimulation with AIP-2 loaded DC specifically induced enhanced levels of CD4+CD25+Foxp3+ regulatory T cells among treatment groups. All in vivo and in vitro results demonstrate that hookworm-derived AIP-1 and AIP-2 proteins reduce T. cruzi induced cardiac inflammation, possibly through multiple anti-inflammatory mechanisms.

Therapeutic vaccination with lentiviral vector in HBV-persistent mice and two inactive HBsAg carriers

Immunotherapy for chronic hepatitis B virus (HBV) infection has not yet demonstrated sufficient efficacy. We developed a non-integrative lentiviral-vectored therapeutic vaccine for chronic hepatitis B and tested its antiviral effects in HBV-persistent mice and two inactive HBsAg carriers. Lentiviral vectors (LVs) encoding the core, preS1, or large HBsAg (LHBs) proteins of HBV were evaluated for immunogenicity in HBV-naïve mice and therapeutic efficacy in a murine model of chronic HBV infection. In addition, two inactive HBsAg carriers each received two doses of 5×107 transduction units (TU) or 1×108 TU of lentiviral-vectored LHBs (LV-LHBs), respectively. The endpoints were safety, LHBs-specific T-cell responses, and serum HBsAg levels during a 24-week follow-up. In the mouse models, LV-LHBs was the most promising in eliciting robust antigen-specific T cells and in reducing the levels of serum HBsAg and viral load. By the end of the 34-week observation period, six out of ten (60%) HBV-persistent mice vaccinated with LV-LHBs achieved serum HBsAg loss and significant depletion of HBV-positive hepatocytes in the liver. In the two inactive HBsAg carriers, vaccination with LV-LHBs induced a considerable increase in the number of peripheral LHBs-specific T cells in one patient, and a weak but detectable response in the other, accompanied by a sustained reduction of HBsAg (-0.31 log10 IU/ml and -0.46 log10 IU/ml, respectively) from baseline to nadir. A lentiviral-vectored therapeutic vaccine for chronic HBV infection demonstrated the potential to improve HBV-specific T-cell responses and deplete HBV-positive hepatocytes, leading to a sustained loss or reduction of serum HBsAg. Chronic HBV infection is characterized by an extremely low number and profound hypo-responsiveness of HBV-specific T cells. Therapeutic vaccines are designed to improve HBV-specific T-cell responses. We show that immunization with a lentiviral-vectored therapeutic HBV vaccine was able to expand HBV-specific T cells invivo, leading to reductions of HBV-positive hepatocytes and serum HBsAg.

Discovery and characterization of antimycobacterial nitro-containing compounds with distinct mechanisms of action and in vivo efficacy.

Nitro-containing compounds have emerged as important agents in the control of tuberculosis (TB). From a whole-cell high-throughput screen for Mycobacterium tuberculosis (Mtb) growth inhibitors, 10 nitro-containing compounds were prioritized for characterization and mechanism of action studies. HC2209, HC2210, and HC2211 are nitrofuran-based prodrugs that need the cofactor F420 machinery for activation. Unlike pretomanid which depends only on deazaflavin-dependent nitroreductase (Ddn), these nitrofurans depend on Ddn and possibly another F420-dependent reductase for activation. These nitrofurans also differ from pretomanid in their potent activity against Mycobacterium abscessus. Four dinitrobenzamides (HC2217, HC2226, HC2238, and HC2239) and a nitrofuran (HC2250) are proposed to be inhibitors of decaprenyl-phosphoryl-ribose 2'-epimerase 1 (DprE1), based on isolation of resistant mutations in dprE1. Unlike other DprE1 inhibitors, HC2250 was found to be potent against non-replicating persistent bacteria, suggesting additional targets. Two of the compounds, HC2233 and HC2234, were found to have potent, sterilizing activity against replicating and non-replicating Mtb in vitro, but a proposed mechanism of action could not be defined. In a pilot in vivo efficacy study, HC2210 was orally bioavailable and efficacious in reducing bacterial load by ~1 log in a chronic murine TB infection model.

Biologically Relevant Murine Models of Chronic Pseudomonas aeruginosa Respiratory Infection.

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen and the leading cause of infection in patients with cystic fibrosis (CF). The ability of P. aeruginosa to evade host responses and develop into chronic infection causes significant morbidity and mortality. Several mouse models have been developed to study chronic respiratory infections induced by P. aeruginosa, with the bead agar model being the most widely used. However, this model has several limitations, including the requirement for surgical procedures and high mortality rates. Herein, we describe novel and adapted biologically relevant models of chronic lung infection caused by P. aeruginosa. Three methods are described: a clinical isolate infection model, utilising isolates obtained from patients with CF; an incomplete antibiotic clearance model, leading to bacterial bounce-back; and the establishment of chronic infection; and an adapted water bottle chronic infection model. These models circumvent the requirement for a surgical procedure and, importantly, can be induced with clinical isolates of P. aeruginosa and in wild-type mice. We also demonstrate successful induction of chronic infection in the transgenic βENaC murine model of CF. We envisage that the models described will facilitate the investigations of host and microbial factors, and the efficacy of novel antimicrobials, during chronic P. aeruginosa respiratory infections.

A novel rodent model of chronic spinal implant-associated infection

BACKGROUND CONTEXTBacterial infection of spinal instrumentation is a significant challenge in spinal fusion surgery. Although the intraoperative local application of powdered vancomycin is common practice for mitigating infection, the antimicrobial effects of this route of administration are short-lived. Therefore, novel antibiotic-loaded bone grafts as well as a reliable animal model to permit the testing of such therapies are needed to improve the efficacy of infection reduction practices in spinal fusion surgery. PURPOSEThis study aims to establish a clinically relevant rat model of spinal implant-associated infection to permit the evaluation of antimicrobial bone graft materials used in spinal fusion. STUDY DESIGNRodent study of chronic spinal implant-associated infection. METHODSInstrumentation anchored in and spanning the vertebral bodies of L4 and L5 was inoculated with bioluminescent methicillin-resistant Staphylococcus aureus bacteria (MRSA). Infection was monitored using an in vivo imaging system (IVIS) for 8 weeks. Spines were harvested and evaluated histologically, and colony-forming units (CFUs) were quantified in harvested implants and spinal tissue. RESULTSPostsurgical analysis of bacterial infection in vivo demonstrated stratification between MRSA and phosphate-buffered saline (PBS) control groups during the first 4 weeks of the 8-week infection period, indicating the successful establishment of acute infection. Over the 8-week chronic infection period, groups inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU demonstrated significantly higher bioluminescence than groups inoculated with PBS control (p = 0.009 and p = 0.041 respectively). Histological examination at 8 weeks postimplantation revealed the presence of abscesses localized to implant placement in all MRSA inoculation groups, with the most pervasive abscess formation in samples inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU. Quantification of CFU plated from harvested spinal tissue at 8 weeks post-implantation revealed the 1 × 105 MRSA CFU inoculation group as the only group with a significantly greater average CFU count compared to PBS control (p = 0.017). Further, CFU quantification from harvested spinal tissue was greater than CFU quantification from harvested implants across all inoculation groups. CONCLUSIONOur model demonstrated that the inoculation dosage of 1 × 105 MRSA CFU exhibited the most robust chronic infection within instrumented vertebral bodies. This dosage had the greatest difference in bioluminescence signal from control (p < 0.01), the lowest mortality (0% compared to 50% for samples inoculated with 1 × 106 MRSA CFU), and a significantly higher amount of CFUs from harvested spine samples than CFUs from control harvested spine samples. Further, histological analysis confirmed the reliability of this novel rodent model of implanted-associated infection to establish infection and biofilm formation of MRSA for all inoculation groups. CLINICAL SIGNIFICANCEThis model is intended to simulate the infection of instrumentation used in spinal fusion surgeries concerning implant locality and material. This model may evaluate potential antimicrobial and osteogenic biomaterials and investigate the relationship between implant-associated infection and failed fusion.

Inhibiting Quorum Sensing by Active Targeted pH-Sensitive Nanoparticles for Enhanced Antibiotic Therapy of Biofilm-Associated Bacterial Infections.

Inhibition of quorum sensing (QS) is considered as an effective strategy in combatting biofilm-associated bacterial infections. However, the application of quorum sensing inhibitors (QSI) is strongly restricted by poor water-solubility and low bioavailability. We herein fabricate pH-sensitive curcumin (Cur) loaded clustered nanoparticles with active targeting ability (denoted as anti-CD54@Cur-DA NPs) to inhibit QS for enhanced antibiotic therapy. Cur-DA NPs are first prepared through electrostatic interaction between Cur loaded amino-ended poly(amidoamine) dendrimer (PAMAM) and 2,3-dimethyl maleic anhydride (DA) modified biotin-poly(ethylene glycol)-polylysine (biotin-PEG-PLys). Anti-CD54@Cur-DA NPs are then obtained by the modification of Cur-DA NPs with anti-CD54. Cur loaded PAMAM can be released from Cur-DA NPs in acidic pH, leading to simultaneous charge reversal and size decrease, which is beneficial for biofilm penetration. Cur-DA NPs are hence much better in inhibiting QS than free Cur due to enhanced biofilm penetration. Compared to free Cur, Cur-DA NPs exhibit stronger capability in inhibiting the development of biofilm architecture and maturation, thus downregulating efflux pump-related genes and improving bactericidal performance of multiple antibiotics, including Penicillin G, ciprofloxacin, and tobramycin. Moreover, since anti-CD54 can selectively bind to inflamed endothelial cells, anti-CD54@Cur-DA NPs can be targeted accumulated in bacteria-infected tissues. The sequential treatment using anti-CD54@Cur-DA NPs and free antibiotics can effectively reduce bacterial burden and alleviate inflammation in a chronic lung infection model in vivo. This research provides an effective way to improve the therapeutic performance of QSI to enhance the anti-biofilm effects of antibiotics, which radiate a vitality of conventional antibiotics in treating biofilm-associated bacterial infections.

Peptide Supramolecular Hydrogels with Sustained Release Ability for Combating Multidrug-Resistant Bacteria.

Chronic wound infection caused by multidrug-resistant bacteria is a major threat globally, leading to high mortality rates and a considerable economic burden. To address it, an innovative supramolecular nanofiber hydrogel (Hydrogel-RL) harboring antimicrobial peptides was developed based on the novel arginine end-tagging peptide (Pep 6) from our recent study, triggering cross-linking. In vitro results demonstrated that Hydrogel-RL can sustain the release of Pep 6 up to 120 h profiles, which is biocompatible and exhibits superior activity for methicillin-resistant Staphylococcus aureus (MRSA) biofilm inhibition and elimination. A single treatment of supramolecular Hydrogel-RL on an MRSA skin infection model revealed formidable antimicrobial activity and therapeutic effects in vivo. In the chronic wound infection model, Hydrogel-RL promoted mouse skin cell proliferation, reduced inflammation, accelerated re-epithelialization, and regulated muscle and collagen fiber formation, rapidly healing full-thickness skin wounds. To show its vehicle property for wound infection combined therapy, etamsylate, an antihemorrhagic drug, was loaded into the porous network of Hydrogel-RL, which demonstrated improved hemostatic activity. Collectively, Hydrogel-RL is a promising clinical candidate agent for functional supramolecular biomaterials designed for combating multidrug-resistant bacteria and rescuing stalled healing in chronic wound infections.

Downregulation of miR‑7 and miR‑153 is involved in Helicobacterpylori CagA induced gastric carcinogenesis and progression.

Helicobacterpylori (H.pylori) infection plays a pivotal role in the development of gastric cancer (GC). However, the association between aberrant microRNAs (miRNAs/miRs) expression and H.pylori‑induced GC remains poorly understood. The present study reported that repeated infection of H.pylori caused the oncogenicity of GES‑1 cells in BALB/c Nude mice. miRNA sequencing revealed that both miR‑7 and miR‑153 were significantly decreased in the cytotoxin‑associated gene A (CagA) positive GC tissues and this was further confirmed in a chronic infection model of GES‑1/HP cells. Further biological function experiments and invivo experiments validated that miR‑7 and miR‑153 can promote apoptosis and autophagy, inhibit proliferation and inflammatory response in GES‑1/HP cells. All the associations between miR‑7/miR‑153 and their potential targets were revealed via bioinformatics prediction and dual‑luciferase reporter assay. Particularly, downregulation of both miR‑7 and miR‑153 obtained an improved sensitivity and specificity in diagnosing H.pylori (CagA+)‑induced GC. The present study identified that the combination of miR‑7 and miR‑153 may be regarded as novel therapeutic targets in H.pylori CagA (+)‑associated GC.

Chlamydia trachomatisinfection renders M2 generation to mediated immunosuppression.

Abstract Chlamydia trachomatis (C.tr) cause asymptomatic genital infections in women and is also a leading cause of preventable blindness. Limited mouse model of chronic C.tr infection are available to study the host immune response. We have developed BALB/c mice models of acute and chronic infections for C. trachomatisto explore the significance of macrophage-directed response in mediating immune activation/suppression. We observed that chronic and repeated infections accompanied abbrogated IFN-g and promoted enhanced TGF-β and IL-10 secretion. The signs of T cell exhaustion and anergy were also indicated during chronic and secondary infection. This skewed T cell response was established to be the regulated by alternatively-activated macrophages with low CD40 expression leading to sustained C. trachomatis genital infection. Macrophages under the influence of C. trachomatis infection or its secretome demonstrate an M2-macrophage subset phenotype which responded poorly to IFN-g owing to decreased IFNg-RI and IFNg-RII expression which correlated with decreased expression/release of MHC-II, CD40, iNOS and NO even following IFN-g treatment. Alternatively-activated M2 macrophages with low CD40 expression harbored high bacterial load and rendered the generation of immunosuppressive Th2 and Treg cells. Thus, C. trachomatis modulate the innate immune cells attenuating the anti-chlamydial functions of T cells in a manner that involves alleviated CD40 expression on macrophages.

PIM kinases are essential for CD8 T cell effector function and metabolism during chronic viral infection

Abstract The production of IL-21 by CD4 T cells is one mechanism by which CD8 T cells can sustain their effector functions, including increased metabolic demand, during chronic viral infection. However, signaling cascades downstream of IL-21 that control effector function in CD8 T cells remain incompletely understood. One such set of targets are the PIM kinases. This family of serine/threonine kinases functions downstream of IL-21 via JAK-STAT signaling and are involved in diverse cellular processes. Treatment of activated CD8 T cells with IL-21 induces expression of PIM1 kinase and phosphorylation of its targets S6 T372, 4EBP T37/42, and BAD S112, which promote transcription and inhibit apoptosis. Using the lymphocytic choriomeningitis virus (LCMV) Clone 13 mouse model of chronic infection, we show that virus-specific effector CD8 T cells display the highest expression of Pim1compared to exhausted and progenitor CD8 T cells at day 21 post-infection (p.i.). Infection of Pim1−/−mice with LCMV Clone 13 results in reduced virus-specific effector CD8 T cells and increased exhausted CD8 T cells at days 21–23 p.i. compared to wildtype controls. In addition, pharmacological inhibition of PIM kinases with AZD1208, a pan-PIM kinase inhibitor, in activated CD8 T cells results in compromised mitochondrial metabolism, which is essential for effector CD8 T cell function. Overall, our results suggest that PIM kinases are critical for effector CD8 T cell differentiation, function, and metabolism in the control of chronic viral infection. Supported by grants from NIH (R01 AI148403) and by an award from the Medical College of Wisconsin Center for Immunology.