Molecular basis determining species specificity for TLR2 inhibition by staphylococcal superantigen-like protein 3 (SSL3)

Interactions between Macrophages and Biofilm during Staphylococcus aureus-Associated Implant Infection: Difficulties and Solutions

Staphylococcus aureus (S. aureus) biofilm is the major cause of failure of implant infection treatment that results in heavy social and economic burden on individuals, families, and communities. Planktonic S. aureus attaches to medical implant surfaces where it proliferates and is wrapped by extracellular polymeric substances, forming a solid and complex biofilm. This provides a stable environment for bacterial growth, infection maintenance, and diffusion and protects the bacteria from antimicrobial agents and the immune system of the host. Macrophages are an important component of the innate immune system and resist pathogen invasion and infection through phagocytosis, antigen presentation, and cytokine secretion. The persistence, spread, or clearance of infection is determined by interplay between macrophages and S. aureus in the implant infection microenvironment. In this review, we discuss the interactions between S. aureus biofilm and macrophages, including the effects of biofilm-related bacteria on the macrophage immune response, roles of myeloid-derived suppressor cells during biofilm infection, regulation of immune cell metabolic patterns by the biofilm environment, and immune evasion strategies adopted by the biofilm against macrophages. Finally, we summarize the current methods that support macrophage-mediated removal of biofilms and emphasize the importance of considering multi-dimensions and factors related to implant-associated infection such as immunity, metabolism, the host, and the pathogen when developing new treatments.

Mechanisms of Toll-like receptor tolerance induced by microbial ligands

Some microorganisms can develop tolerance. On the one hand, it allows pathogenic microbes to escape immune surveillance, on the other hand, it provides the possibility to microbiota representatives to colonize different biotopes and build a symbiotic relationship with the host. Complex regulatory interactions between innate and adaptive immune systems as well as stimulation by antigens help microbes control and maintain immunological tolerance. An important role in this process belongs to innate immune cells, which recognize microbial components through pattern-recognition receptors. Toll-like receptors (TLRs) represent the main class of these receptors. Despite the universality of the activated signaling pathways, different cellular responses are induced by interaction of TLRs with microbiota representatives and pathogenic microbes, and they vary during acute and chronic infection. The research on mechanisms underlying the development of TLR tolerance is significant, as the above receptors are involved in a wide range of infectious and noninfectious diseases; they also play an important role in development of allergic diseases, autoimmune diseases, and cancers. The knowledge of TLR tolerance mechanisms can be critically important for development of TLR ligand-based therapeutic agents for treatment and prevention of multiple diseases.

Anti-PCSK9 monoclonal antibody attenuates high-fat diet and zymosan-induced vascular inflammation in C57BL/6 mice by modulating TLR2/NF-ƙB signaling pathway

Objectives

Excess intake of a high-fatty diet (HFD) together with zymosan administration mediates vasculitis response which leads to impaired serum lipid levels and causes arterial stiffness. In the development of new cholesterol-lowering medications, PCSK9 inhibitor (proprotein convertase subtilisin/kexin type 9) is an emerging therapeutic. The goal of the present study was to see whether anti-PCSK9 mAb1 might prevent vasculitis in C57BL/6 mice by blocking TLR2/NF-B activation in HFD and Zymosan-induced vasculitis.

Materials and Methods

Protein-protein molecular docking was performed to validate the binding affinity of anti-PCSK9 mAb1 against TLR2. Under the experimental study, mice were randomly allocated to the following groups: Group I: standard mice diet (30 days) + Zymosan vehicle (sterile PBS solution of 5mg/ml on 8^th day); Group II: HFD (30 days) + Zymosan ( single IP dose 80 mg/kg on day 8^th); Group III: HFD+Zymosan + anti-PCSK9 mAb1 (6 mg/kg, s.c. on 10^th and 20^th days); Group IV: HFD+Zymosan+anti-PCSK9 mAb1 (10 mg/kg, s.c. on 10^th and 20^th days).

Results

In comparison with the low dose of anti-PCSK9 mAb1 (6 mg/kg), the high dose of anti-PCSK9 mAb1 (10 mg/kg) together with HFD and Zymosan inhibited vasculitis more effectively by decreasing aortic TLR2 and NF-B levels, reducing serum TNF- and IL-6, and up-regulating liver LDLR levels, which down-regulated serum LDL-C and improved serum lipids levels. Histopathological studies showed that anti-PCSK9 mAb1 treatment reduced plaque accumulation in the aorta of mice.

Conclusion

These findings indicate that anti-PCSK9 mAb1 has therapeutic potential in reducing HFD and Zymosan-induced vascular inflammation.

Modulatory role of atorvastatin against high-fat diet and zymosan-induced activation of TLR2/NF-ƙB signaling pathway in C57BL/6 mice

OBJECTIVES

Accumulated evidence provides a strong connection between the immune system and vascular inflammation. The innate immune system's main sensors are toll-like receptors (TLRs). Zymosan (Zym), a fungal product, induces an inflammatory response via activating TLR2 of the immune system. Atorvastatin, a potent statin, possesses pleiotropic effects including immunomodulatory, lipid-lowering, and anti-inflammatory. Therefore, the current study aimed to evaluate the protective role of atorvastatin against a high-fat diet (HFD) and Zym-induced vascular inflammation in C57BL/6 mice via modulation of TLR2/NF-ƙB signaling pathway.

MATERIALS AND METHODS

In silico study was conducted to confirm the binding affinity of atorvastatin against TLR2. Under in vivo study, mice were divided into four groups: Normal control: normal standard chow-diet fed for 30 days + Zym vehicle (sterile PBS, 5 mg/ml on 8th day); HFD (30 days) + Zym (80 mg/kg, IP, on 8th day); HFD/Zym + atorvastatin vehicle (0.5% CMC, p.o., from 10th to 30th day); HFD/Zym + atorvastatin (3.6 mg/kg, p.o., from 10th to 30th day).

RESULTS

Atorvastatin treatment along with HFD and Zym inhibited vascular inflammation by suppressing the levels of aortic TLR2, cardiac NF-ƙB and decrease in serum TNF-α and IL-6. Further, there was an increase in hepatic LDLR levels, resulting in a decrease in serum LDL-C and an increase in HDL-C levels. Histopathological examination of the aorta showed a reduction in plaque accumulation with the atorvastatin-treated group as compared with HFD and Zym-treated group.

CONCLUSION

Atorvastatin attenuates vascular inflammation mediated by HFD and Zym through suppression of TLR2, NF-ƙB, TNF-α, IL-6, and upregulation of LDLR levels.

Interplay between ESKAPE Pathogens and Immunity in Skin Infections: An Overview of the Major Determinants of Virulence and Antibiotic Resistance

The skin is the largest organ in the human body, acting as a physical and immunological barrier against pathogenic microorganisms. The cutaneous lesions constitute a gateway for microbial contamination that can lead to chronic wounds and other invasive infections. Chronic wounds are considered as serious public health problems due the related social, psychological and economic consequences. The group of bacteria known as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) are among the most prevalent bacteria in cutaneous infections. These pathogens have a high level of incidence in hospital environments and several strains present phenotypes of multidrug resistance. In this review, we discuss some important aspects of skin immunology and the involvement of ESKAPE in wound infections. First, we introduce some fundamental aspects of skin physiology and immunology related to cutaneous infections. Following this, the major virulence factors involved in colonization and tissue damage are highlighted, as well as the most frequently detected antimicrobial resistance genes. ESKAPE pathogens express several virulence determinants that overcome the skin's physical and immunological barriers, enabling them to cause severe wound infections. The high ability these bacteria to acquire resistance is alarming, particularly in the hospital settings where immunocompromised individuals are exposed to these pathogens. Knowledge about the virulence and resistance markers of these species is important in order to develop new strategies to detect and treat their associated infections.