Immunomodulatory effects of recombinant lactoferrin during MRSA infection

Immunomodulation in Non-traditional Therapies for Methicillin-resistant Staphylococcus aureus (MRSA) Management

The rise of methicillin-resistant Staphylococcus aureus (MRSA) poses a significant challenge in clinical settings due to its ability to evade conventional antibiotic treatments. This overview explores the potential of immunomodulatory strategies as alternative therapeutic approaches to combat MRSA infections. Traditional antibiotics are becoming less effective, necessitating innovative solutions that harness the body's immune system to enhance pathogen clearance. Recent advancements in immunotherapy, including the use of antimicrobial peptides, phage therapy, and mechanisms of immune cells, demonstrate promise in enhancing the body's ability to clear MRSA infections. However, the exact interactions between these therapies and immunomodulation are not fully understood, underscoring the need for further research. Hence, this review aims to provide a broad overview of the current understanding of non-traditional therapeutics and their impact on immune responses, which could lead to more effective MRSA treatment strategies. Additionally, combining immunomodulatory agents with existing antibiotics may improve outcomes, particularly for immunocompromised patients or those with chronic infections. As the landscape of antibiotic resistance evolves, the development of effective immunotherapeutic strategies could play a vital role in managing MRSA infections and reducing reliance on traditional antibiotics. Future research must focus on optimizing these approaches and validating their efficacy in diverse clinical populations to address the urgent need for effective MRSA management strategies.

A review of the biological activities of lactoferrin: mechanisms and potential applications

Lactoferrin, a multifunctional iron-binding protein found in milk and other body fluids, possesses numerous biological activities. The functional activity of lactoferrin lies not only in its iron-binding capacity but also in the molecular mechanisms by which it can affect important chemical components in the host. However, the molecular mechanisms underlying these activities remain unelucidated. In this paper, we review the structure, properties, and contents of different lactoferrin milk sources. The different biological activities, namely antibacterial, antiviral, immunomodulatory, anti-inflammatory, bone regeneration, and improved metabolic disorder bioactivities, and the associated potential mechanisms of lactoferrin are summarized with the aim of providing a reference for the development of lactoferrin-related products.

Lactoferrin Binds through Its N-Terminus to the Receptor-Binding Domain of the SARS-CoV-2 Spike Protein

Since Coronavirus disease 2019 (COVID-19) still presents a considerable threat, it is beneficial to provide therapeutic supplements against it. In this respect, glycoprotein lactoferrin (LF) and lactoferricin (LFC), a natural bioactive peptide yielded upon digestion from the N-terminus of LF, are of utmost interest, since both have been shown to reduce infections of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus responsible for COVID-19, in particular via blockade of the virus priming and binding. Here, we, by means of biochemical and biophysical methods, reveal that LF directly binds to the S-protein of SARS-CoV-2. We determined thermodynamic and kinetic characteristics of the complex formation and mapped the mutual binding sites involved in this interaction, namely the N-terminal region of LF and the receptor-binding domain of the S-protein (RBD). These results may not only explain many of the observed protective effects of LF and LFC in SARS-CoV-2 infection but may also be instrumental in proposing potent and cost-effective supplemental tools in the management of COVID-19.

Nutraceutical and Health-Promoting Potential of Lactoferrin, an Iron-Binding Protein in Human and Animal: Current Knowledge

Lactoferrin is a natural cationic iron-binding glycoprotein of the transferrin family found in bovine milk and other exocrine secretions, including lacrimal fluid, saliva, and bile. Lactoferrin has been investigated for its numerous powerful influences, including anticancer, anti-inflammatory, anti-oxidant, anti-osteoporotic, antifungal, antibacterial, antiviral, immunomodulatory, hepatoprotective, and other beneficial health effects. Lactoferrin demonstrated several nutraceutical and pharmaceutical potentials and have a significant impact on improving the health of humans and animals. Lactoferrin plays a critical role in keeping the normal physiological homeostasis associated with the development of pathological disorders. The current review highlights the medicinal value, nutraceutical role, therapeutic application, and outstanding favorable health sides of lactoferrin, which would benefit from more exploration of this glycoprotein for the design of effective medicines, drugs, and pharmaceuticals for safeguarding different health issues in animals and humans.

Time to Kill and Time to Heal: The Multifaceted Role of Lactoferrin and Lactoferricin in Host Defense

Lactoferrin is an iron-binding glycoprotein present in most human exocrine fluids, particularly breast milk. Lactoferrin is also released from neutrophil granules, and its concentration increases rapidly at the site of inflammation. Immune cells of both the innate and the adaptive immune system express receptors for lactoferrin to modulate their functions in response to it. On the basis of these interactions, lactoferrin plays many roles in host defense, ranging from augmenting or calming inflammatory pathways to direct killing of pathogens. Complex biological activities of lactoferrin are determined by its ability to sequester iron and by its highly basic N-terminus, via which lactoferrin binds to a plethora of negatively charged surfaces of microorganisms and viruses, as well as to mammalian cells, both normal and cancerous. Proteolytic cleavage of lactoferrin in the digestive tract generates smaller peptides, such as N-terminally derived lactoferricin. Lactoferricin shares some of the properties of lactoferrin, but also exhibits unique characteristics and functions. In this review, we discuss the structure, functions, and potential therapeutic uses of lactoferrin, lactoferricin, and other lactoferrin-derived bioactive peptides in treating various infections and inflammatory conditions. Furthermore, we summarize clinical trials examining the effect of lactoferrin supplementation in disease treatment, with a special focus on its potential use in treating COVID-19.

Modulation of TDM-induced granuloma pathology by human lactoferrin: a persistent effect in mice

Lactoferrin (LTF), an iron binding protein, is known to exhibit immune modulatory effects on pulmonary pathology during insult-induced models of primary Mycobacterium tuberculosis (Mtb) infection. The effects of LTF correlate with modulation of the immune related development of the pathology, and altering of the histological nature of the physically compact and dense lung granuloma in mice. Specifically, a recombinant human version of LTF limits immediate progression of granulomatous severity following administration of the Mtb cell wall mycolic acid, trehalose 6,6'-dimycolate (TDM), in part through reduced pro-inflammatory responses known to control these events. This current study investigates a limited course of LTF to modulate not only initiation, but also maintenance and resolution of pathology post development of the granulomatous response in mice. Comparison is made to a fusion of LTF with the Fc domain of IgG2 (FcLTF), which is known to extend LTF half-life in circulation. TDM induced granulomas were examined at extended times post insult (day 7 and 14). Both LTF and the novel FcLTF exerted sustained effects on lung granuloma pathology. Reduction of pulmonary pro-inflammatory cytokines TNF-α and IL-1β occurred, correlating with reduced pathology. Increase in IL-6, known to regulate granuloma maintenance, was also seen with the LTFs. The FcLTF demonstrated greater impact than the recombinant LTF, and was superior in limiting damage to pulmonary tissues while limiting residual inflammatory cytokine production.

Eleutheroside K Isolated from Acanthopanax henryi (Oliv.) Harms Inhibits the Expression of Virulence-Related Exoproteins in Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus (S.) aureus (MRSA) is a representative pathogen that produces numerous virulence factors involving manifold cytotoxins and exotoxins. The present study was designed to investigate the influence of Eleutheroside K (ETSK), a single compound isolated from the leaves of Acanthopanax (A.) henryi (Oliv.) Harms, on the exotoxins secreted by MRSA. The transcription and translation of the exotoxins (α-hemolysin and staphylococcal enterotoxins) related to virulence in S. aureus were determined via quantitative RT-PCR and western blot analysis. The effect of ETSK on the production of tumor necrosis factor (TNF)-α was evaluated using enzyme-linked immunosorbent assay. As a result, ETSK at sub-MIC concentrations could reduce the protein expression of α-hemolysin and enterotoxin, and the expression of genes that regulate virulence factors was also inhibited. In addition, the TNF-inducing activity of S. aureus was attenuated by ETSK in a dose-dependent manner. These results revealed that ETSK not only reduced the protein and gene expression levels of related exotoxins but also suppressed the ability of S. aureus to induce macrophages to release cytokines. This study indicated that the inhibition of MRSA infection by ETSK may be achieved by reducing the virulence of S. aureus and highlighted the potential of ETSK as an innovative strategy for the prevention and treatment of MRSA infections.

The potential for Lactoferrin to reduce SARS-CoV-2 induced cytokine storm

The COVID-19 pandemic is a serious global health threat caused by severe acute respiratory syndrome of coronavirus 2 (SARS-CoV-2). Symptoms of COVID-19 are highly variable with common hyperactivity of immune responses known as a "cytokine storm". In fact, this massive release of inflammatory cytokines into in the pulmonary alveolar structure is a main cause of mortality during COVID-19 infection. Current management of COVID-19 is supportive and there is no common clinical protocol applied to suppress this pathological state. Lactoferrin (LF), an iron binding protein, is a first line defense protein that is present in neutrophils and excretory fluids of all mammals, and is well recognized for its role in maturation and regulation of immune system function. Also, due to its ability to sequester free iron, LF is known to protect against insult-induced oxidative stress and subsequent "cytokine storm" that results in dramatic necrosis within the affected tissue. Review of the literature strongly suggests utility of LF to silence the "cytokine storm", giving credence to both prophylactic and therapeutic approaches towards combating COVID-19 infection.

Antibacterial and Anti-biofilm Activity of the Human Breast Milk Glycoprotein Lactoferrin against Group B Streptococcus

Group B Streptococcus (GBS) is an encapsulated Gram-positive human pathogen that causes invasive infections in pregnant hosts and neonates, as well as immunocompromised individuals. Colonization of the human host requires the ability to adhere to mucosal surfaces and circumnavigate the nutritional challenges and antimicrobial defenses associated with the innate immune response. Biofilm formation is a critical process to facilitate GBS survival and establishment of a replicative niche in the vertebrate host. Previous work has shown that the host responds to GBS infection by producing the innate antimicrobial glycoprotein lactoferrin, which has been implicated in repressing bacterial growth and biofilm formation. Additionally, lactoferrin is highly abundant in human breast milk and could serve a protective role against invasive microbial pathogens. This study demonstrates that human breast milk lactoferrin has antimicrobial and anti-biofilm activity against GBS and inhibits its adherence to human gestational membranes. Together, these results indicate that human milk lactoferrin could be used as a prebiotic chemotherapeutic strategy to limit the impact of bacterial adherence and biofilm formation on GBS-associated disease outcomes.

Lactoferrin is a dynamic protein in human melioidosis and is a TLR4-dependent driver of TNF-α release in Burkholderia thailandensis infection in vitro

Melioidosis is an often-severe tropical infection caused by Burkholderia pseudomallei (Bp) with high associated morbidity and mortality. Burkholderia thailandensis (Bt) is a closely related surrogate that does not require BSL-3 conditions for study. Lactoferrin is an iron-binding glycoprotein that can modulate the innate inflammatory response. Here we investigated the impact of lactoferrin on the host immune response in melioidosis. Lactoferrin concentrations were measured in plasma from patients with melioidosis and following ex vivo stimulation of blood from healthy individuals. Bt growth was quantified in liquid media in the presence of purified and recombinant human lactoferrin. Differentiated THP-1 cells and human blood monocytes were infected with Bt in the presence of purified and recombinant human lactoferrin, and bacterial intracellular replication and cytokine responses (tumor necrosis factor-α (TNF-α), interleukin-1β and interferon-γ) were measured. In a cohort of 49 melioidosis patients, non-survivors to 28 days had significantly higher plasma lactoferrin concentrations compared to survivors (median (interquartile range (IQR)): 326 ng/ml (230-748) vs 144 ng/ml (99-277), p<0.001). In blood stimulated with heat-killed Bp, plasma lactoferrin concentration significantly increased compared to unstimulated blood (median (IQR): 424 ng/ml (349-479) vs 130 ng/ml (91-214), respectively; p<0.001). Neither purified nor recombinant human lactoferrin impaired growth of Bt in media. Lactoferrin significantly increased TNF-α production by differentiated THP-1 cells and blood monocytes after Bt infection. This phenotype was largely abrogated when Toll-like receptor 4 (TLR4) was blocked with a monoclonal antibody. In sum, lactoferrin is produced by blood cells after exposure to Bp and lactoferrin concentrations are higher in 28-day survivors in melioidosis. Lactoferrin induces proinflammatory cytokine production after Bt infection that may be TLR4 dependent.

Lactoferrin reduces mycobacterial M1-type inflammation induced with trehalose 6,6'-dimycolate and facilitates the entry of fluoroquinolone into granulomas

Primary infection with Mycobacterium tuberculosis (Mtb) results in the formation of a densely packed granulomatous response that essentially limits the entry and efficacy of immune effector cells. Furthermore, the physical nature of the granuloma does not readily permit the entry of therapeutic agents to sites where organisms reside. The Mtb cell wall mycolic acid, trehalose 6,6'-dimycolate (TDM), is a physiologically relevant molecule for modelling macrophage-mediated events during the establishment of the tuberculosis-induced granuloma pathogenesis. At present, there are no treatments for tuberculosis that focus on modulating the host's immune responses. Previous studies showed that lactoferrin (LF), a natural iron-binding protein proven to modulate inflammation, can ameliorate the cohesiveness of granuloma. This led to a series of studies that further examined the effects of recombinant human LF (rHLF) on the histological progression of TDM-induced pathology. Treatment with rHLF demonstrated significant reduction in size and number of inflammatory foci following injections of TDM, together with reduced levels pulmonary pro-inflammatory cytokines TNF-α and IL-1β. LF facilitated greater penetration of fluoroquinolone to the sites of pathology. Mice treated with TDM alone demonstrated exclusion of ofloxacin to regions of inflammatory response, whereas the animals treated with rHLF demonstrated increased penetration to inflammatory foci. Finally, recent findings support the hypothesis that this mycobacterial mycolic acid can specifically recruit M1-like polarized macrophages; rHLF treatment was shown to limit the level of this M1-like phenotypic recruitment, corresponding highly with decreased inflammatory response.

Iron Metabolism at the Interface between Host and Pathogen: From Nutritional Immunity to Antibacterial Development

Nutritional immunity is a form of innate immunity widespread in both vertebrates and invertebrates. The term refers to a rich repertoire of mechanisms set up by the host to inhibit bacterial proliferation by sequestering trace minerals (mainly iron, but also zinc and manganese). This strategy, selected by evolution, represents an effective front-line defense against pathogens and has thus inspired the exploitation of iron restriction in the development of innovative antimicrobials or enhancers of antimicrobial therapy. This review focuses on the mechanisms of nutritional immunity, the strategies adopted by opportunistic human pathogen Staphylococcus aureus to circumvent it, and the impact of deletion mutants on the fitness, infectivity, and persistence inside the host. This information finally converges in an overview of the current development of inhibitors targeting the different stages of iron uptake, an as-yet unexploited target in the field of antistaphylococcal drug discovery.

Antibacterial Activity and Pharmacokinetic Profile of a Promising Antibacterial Agent: 22-(2-Amino-phenylsulfanyl)-22-Deoxypleuromutilin

A new pleuromutilin derivative, 22-(2-amino-phenylsulfanyl)-22-deoxypleuromutilin (amphenmulin), has been synthesized and proved excellent in vitro and in vivo efficacy than that of tiamulin against methicillin-resistant Staphylococcus aureus (MRSA), suggesting this compound may lead to a promising antibacterial agent to treat MRSA infections. In this study, the effectiveness and safety of amphenmulin were further investigated. Amphenmulin showed excellent antibacterial activity against MRSA (minimal inhibitory concentration = 0.0156~8 µg/mL) and performed time-dependent growth inhibition and a concentration-dependent postantibiotic effect (PAE). Acute oral toxicity test in mice showed that amphenmulin was a practical non-toxic drug and possessed high security as a new drug with the 50% lethal dose (LD50) above 5000 mg/kg. The pharmacokinetic properties of amphenmulin were then measured. After intravenous administration, the elimination half-life (T1/2), total body clearance (Clβ), and area under curve to infinite time (AUC0→∞) were 1.92 ± 0.28 h, 0.82 ± 0.09 L/h/kg, and 12.23 ± 1.35 μg·h/mL, respectively. After intraperitoneal administration, the T1/2, Clβ/F and AUC0→∞ were 2.64 ± 0.72 h, 4.08 ± 1.14 L/h/kg, and 2.52 ± 0.81 μg·h/mL, respectively, while for the oral route were 2.91 ± 0.81 h, 6.31 ± 2.26 L/h/kg, 1.67 ± 0.66 μg·h/mL, respectively. Furthermore, we evaluated the antimicrobial activity of amphenmulin in an experimental model of MRSA wound infection. Amphenmulin enhanced wound closure and promoted the healing of wound, which inhibited MRSA bacterial counts in the wound and decreased serum levels of the pro-inflammatory cytokines TNF-α, IL-6, and MCP-1.

Innate Nutritional Immunity

Iron (Fe) is an essential micronutrient for both microbes and their hosts. The biologic importance of Fe derives from its inherent ability to act as a universal redox catalyst, co-opted in a variety of biochemical processes critical to maintain life. Animals evolved several mechanisms to retain and limit Fe availability to pathogenic microbes, a resistance mechanism termed "nutritional immunity." Likewise, pathogenic microbes coevolved to deploy diverse and efficient mechanisms to acquire Fe from their hosts and in doing so overcome nutritional immunity. In this review, we discuss how the innate immune system regulates Fe metabolism to withhold Fe from pathogenic microbes and how strategies used by pathogens to acquire Fe circumvent these resistance mechanisms.

Lactoferrin in a Context of Inflammation-Induced Pathology

Much progress has been achieved to elucidate the function of lactoferrin (LTF), an iron-binding glycoprotein, in the milieu of immune functionality. This review represents a unique examination of LTF toward its importance in physiologic homeostasis as related to development of disease-associated pathology. The immunomodulatory nature of this protein derives from its unique ability to "sense" the immune activation status of an organism and act accordingly. Underlying mechanisms are proposed whereby LTF controls disease states, thereby pinpointing regions of entry for LTF in maintenance of various physiological pathways to limit the magnitude of tissue damage. LTF is examined as a first line mediator in immune defense and response to pathogenic and non-pathogenic injury, as well as a molecule critical for control of oxidative cell function. Mechanisms of interaction of LTF with its receptors are examined, with a focus on protective effects via regulation of enzyme activities and reactive oxygen species production, immune deviation, and prevention of cell apoptosis. Indeed, LTF serves as a critical control point in physiologic homeostasis, functioning as a sensor of immunological performance related to pathology. Specific mediation of tissue pathophysiology is described for maintenance of intestinal integrity during endotoxemia, elicited airway inflammation due to allergens, and pulmonary damage during tuberculosis. Finally, the role of LTF to alter differentiation of adaptive immune function is examined, with specific recognition of its utility as a vaccine adjuvant to control subsequent lymphocytic reactivity. Overall, it is clear that while the ability of LTF to both sequester iron and to direct reactive oxygen intermediates is a major factor in lessening damage due to excessive inflammatory responses, further effects are apparent through direct control over development of higher order immune functions that regulate pathology due to insult and injury. This culminates in attenuation of pathological damage during inflammatory injury.

Preventive effects of the novel antimicrobial peptide Nal-P-113 in a rat Periodontitis model by limiting the growth of Porphyromonas gingivalis and modulating IL-1β and TNF-α production

Background

P-113 (AKRHHGYKRKFH-NH2) is a 12-amino-acid histidine-rich peptide derived from histatin 5 that is highly degradable in high salt concentrations and biological fluids such as serum, plasma and saliva. Nal-P-113, a novel antimicrobial peptide whose histidine residues are replaced by the bulky amino acids β-naphthylalanine, causes the antimicrobial peptide to retain its bactericidal activity even in physiological environments. This study evaluated the effect of the novel antimicrobial peptide Nal-P-113 in a rat periodontitis model and the mechanisms of action of Nal-P-113 for suppressing periodontitis.

Methods

Periodontitis was induced in mandibular first molars in rats receiving a ligature and infected with Porphyromonas gingivalis. Animals were randomly divided into six groups: a, P. gingivalis W83 alone; b, P. gingivalis W83 with 6.25 μg/mL of Nal-P-113; c, P. gingivalis W83 with 25 μg/mL of Nal-P-113; d, P. gingivalis W83 with 100 μg/mL of Nal-P-113; e, P. gingivalis W83 with 400 μg/mL of Nal-P-113; and f, control without P. gingivalis W83 or Nal-P-113. Morphometric analysis was used to evaluate alveolar bone loss. Microbiological assessment of the presence of Porphyromonas gingivalis and total bacteria was performed using absolute quantitative real-time PCR and scanning electron microscopy. Gingival tissue was collected for western blot and immunohistochemical assays of IL-1β and TNF-α levels.

Results

Alveolar bone loss was inhibited by 100 μg/mL or 400 μg/mL of Nal-P-113 compared to the control group (P < 0.05). Lower amounts of P. gingivalis and total bacteria were found in groups d and e compared with group a (P < 0.05). A decrease in the levels of IL-1β and TNF-α was detected in group d and group e compared to the control group (P < 0.05). The amount of P. gingivalis was positively correlated with IL-1β and TNF-α expression in periodontal tissue (P < 0.05).

Conclusions

Nal-P-113 exhibited protective effects on Porphyromonas gingivalis-induced periodontitis in rats by limiting the amount of bacteria and modulating IL-1β and TNF-α production. The use of Nal-P-113 in vivo might serve as a beneficial preventive or therapeutic approach for periodontitis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1931-9) contains supplementary material, which is available to authorized users.

Role of iron in the pathogenesis of respiratory disease

Iron is essential for many biological processes, however, too much or too little iron can result in a wide variety of pathological consequences, depending on the organ system, tissue or cell type affected. In order to reduce pathogenesis, iron levels are tightly controlled in throughout the body by regulatory systems that control iron absorption, systemic transport and cellular uptake and storage. Altered iron levels and/or dysregulated homeostasis have been associated with several lung diseases, including chronic obstructive pulmonary disease, lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis and asthma. However, the mechanisms that underpin these associations and whether iron plays a key role in the pathogenesis of lung disease are yet to be fully elucidated. Furthermore, in order to survive and replicate, pathogenic micro-organisms have evolved strategies to source host iron, including freeing iron from cells and proteins that store and transport iron. To counter these microbial strategies, mammals have evolved immune-mediated defence mechanisms that reduce iron availability to pathogens. This interplay between iron, infection and immunity has important ramifications for the pathogenesis and management of human respiratory infections and diseases. An increased understanding of the role that iron plays in the pathogenesis of lung disease and respiratory infections may help inform novel therapeutic strategies. Here we review the clinical and experimental evidence that highlights the potential importance of iron in respiratory diseases and infections.

Bovine lactoferrin free of lipopolysaccharide can induce a proinflammatory response of macrophages

Background

Lactoferrin (LF) is an 80 kDa glycoprotein which is known for its effects against bacteria, viruses and other pathogens. It also has a high potential in nutrition therapy and welfare of people and a variety of animals, including piglets. The ability to bind lipopolysaccharide (LPS) is one of the described anti-inflammatory mechanisms of LF. Previous studies suggested that cells can be stimulated even by LPS-free LF. Therefore, the aim of our study was to bring additional information about this possibility. Porcine monocyte derived macrophages (MDMF) and human embryonic kidney (HEK) cells were stimulated with unpurified LF in complex with LPS and with purified LF without bound LPS.

Results

Both cell types were stimulated with unpurified as well as purified LF. On the other hand, neither HEK0 cells not expressing any TLR nor HEK4a cells transfected with TLR4 produced any pro-inflammatory cytokine transcripts after stimulation with purified LF. This suggests that purified LF without LPS stimulates cells via another receptor than TLR4. An alternative, TLR4-independent, pathway was further confirmed by analyses of the NF-kappa-B-inducing kinase (NIK) activation. Western blot analyses showed NIK which activates different NFκB subunits compared to LF-LPS signaling via TLR4. Though, this confirmed an alternative pathway which is used by the purified LF free of LPS. This stimulation of MDMF led to low, but significant amounts of pro-inflammatory cytokines, which can be considered as a positive stimulation of the immune system.

Conclusion

Our results suggest that LF’s ability is not only to bind LPS, but LF itself may be a stimulant of pro-inflammatory pathways.

Mechanism of synergy between SIPI-8294 and β-lactam antibiotics against methicillin-resistant Staphylococcus aureus

SIPI-8294, as an erythromycin derivative, has only weak antibacterial effects on MRSA and MSSA. Interestingly, synergistic effect of SIPI-8294 with oxacillin was observed both in vitro and in vivo. Western blot and RT-PCR results demonstrate that mecA expressions were suppressed by SIPI-8294 in MRSA. Furthermore, the knock out of mecA in ATCC 43300 led to the loss of synergy of the combinations while mecA complemented strain showed almost the same synergistic capability compared to the wild type strain. However, the knock out of mecR1 and mecI in MRSA displayed no impact on the synergy of the combinations and the ability of SIPI-8294 to suppress mecA expression. In summary, our study has demonstrated that SIPI-8294 could dramatically reverse MRSA resistance to β-lactams both in vitro and in vivo owing to inhibiting mecA expression. However, mecR1 and mecI, as the pivotal regulatory genes of mecA, do not participate in SIPI-8294-mecA pathway. The research indicates that it may be a promising strategy for combating MRSA infections with the combinations of SIPI-8294 and β-lactam antibiotics. The research of the mechanism is important for structure modification and new drug development.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report on the mechanism of synergy between SIPI-8294 and β-lactams against MRSA on the molecular level. In this study, SIPI-8294 showed strong synergistic effects on β-lactam antibiotics both in vitro and in vivo owing to inhibiting mecA expression. As pivotal regulatory genes of mecA, mecR1 and mecI do not participate in SIPI-8294-mecA pathway and are not involved in the synergism of SIPI-8294 and β-lactams. The research indicates that it may be a promising strategy for combating MRSA infections with the combinations of SIPI-8294 and β-lactams. The research is important for structure modification and new drug development.

The Iron age of host-microbe interactions

Microbes exert a major impact on human health and disease by either promoting or disrupting homeostasis, in the latter instance leading to the development of infectious diseases. Such disparate outcomes are driven by the ever-evolving genetic diversity of microbes and the countervailing host responses that minimize their pathogenic impact. Host defense strategies that limit microbial pathogenicity include resistance mechanisms that exert a negative impact on microbes, and disease tolerance mechanisms that sustain host homeostasis without interfering directly with microbes. While genetically distinct, these host defense strategies are functionally integrated, via mechanisms that remain incompletely defined. Here, we explore the general principles via which host adaptive responses regulating iron (Fe) metabolism impact on resistance and disease tolerance to infection.

Effects of CHO-expressed recombinant lactoferrins on mouse dendritic cell presentation and function

Lactoferrin (LF), a natural iron-binding protein, has previously demonstrated effectiveness in enhancing the Bacillus Calmette-Guérin (BCG) tuberculosis vaccine. This report investigates immune modulatory effects of Chinese hamster ovary (CHO) cell-expressed recombinant mouse and human LFs on mouse bone marrow-derived dendritic cells (BMDCs), comparing homologous and heterologous functions. BCG-infected BMDCs were cultured with LF, and examined for class II presentation molecule expression. Culturing of BCG-infected BMDCs with either LF decreased the class II molecule-expressing population. Mouse LF significantly increased the production of IL-12p40, IL-1β and IL-10, while human LF-treated BMDCs increased only IL-1β and IL-10. Overlaying naïve CD4 T-cells onto BCG-infected BMDCs cultured with mouse LF increased IFN-γ, whereas the human LF-exposed group increased IFN-γ and IL-17 from CD4 T cells. Overlay of naïve CD8 T cells onto BCG-infected BMDCs treated with mouse LF increased the production of IFN-γ and IL-17, while similar experiments using human LF only increased IL-17. This report is the first to examine mouse and human recombinant LFs in parallel experiments to assess murine DC function. These results detail the efficacy of the human LF counterpart used in a heterologous system to understand LF-mediated events that confer BCG efficacy against Mycobacterium tuberculosis challenge.