Immunosuppressive activity of fosfomycin on human T-lymphocyte function in vitro

Fosfomycin modifies the replication kinetics of bovine alphaherpesvirus-1 and reduces the timing of its protein expression on bovine (MDBK) and human (SH-SY5Y) cell lines

Bovine alphaherpesvirus 1 (BoAHV-1) predisposes cattle to respiratory secondary bacterial infections, which can be treated with the broad-spectrum antibiotic fosfomycin. This drug also suppresses NF-kB activity and pro-inflammatory responses. Therefore, cattle may be exposed to an interaction between the virus and the antibiotic which may have effects on it. The aim of this study was to determine the effect of calcium fosfomycin (580 µg/mL) on BoAHV-1 (moi = 0.1) replication. Two cell lines (MDBK and SH-SY5Y) were used in this study. Our results show that fosfomycin has novel properties. By MTT assay we have shown that it is non-cytotoxic for any of the cell lines. Extracellular and intracellular viral titers demonstrated that fosfomycin has a cell-type and time-dependent effect on BoAHV-1 replication. By direct immunofluorescence it was shown that it reduces the timing of BoAHV-1 protein expression, and by qPCR, we found that its effect on NF-kB mRNA expression depends on the cell type.

Fosfomycin

The treatment of bacterial infections suffers from two major problems: spread of multidrug-resistant (MDR) or extensively drug-resistant (XDR) pathogens and lack of development of new antibiotics active against such MDR and XDR bacteria. As a result, physicians have turned to older antibiotics, such as polymyxins, tetracyclines, and aminoglycosides. Lately, due to development of resistance to these agents, fosfomycin has gained attention, as it has remained active against both Gram-positive and Gram-negative MDR and XDR bacteria. New data of higher quality have become available, and several issues were clarified further. In this review, we summarize the available fosfomycin data regarding pharmacokinetic and pharmacodynamic properties, the in vitro activity against susceptible and antibiotic-resistant bacteria, mechanisms of resistance and development of resistance during treatment, synergy and antagonism with other antibiotics, clinical effectiveness, and adverse events. Issues that need to be studied further are also discussed.

Novel inhaled combined antibiotic formulations in the treatment of Pseudomonas aeruginosa airways infections in cystic fibrosis

In cystic fibrosis, chronic airways infection caused by Pseudomonas aeruginosa can be treated with inhaled antibiotics such as inhaled tobramycin, aztreonam or colistin. However, biofilm formation induced by this bacterium can reduce the effectiveness of such therapies and can contribute to antibiotic resistance. Inhaled antibiotic combination might represent an optimal antibiofilm strategy in this setting. This review discusses the rationale for combining the antibiotics as well as some emerging or existing combinations. Most of the combinations except for fosfomycin/tobramycin are at an early stage of development. The latter combination was found to be effective in Phase II clinical studies and is planned to be tested in Phase III trials. The clinical data on long-term efficacy are currently missing, but the existing evidence as well as the unmet therapeutic need can prompt the further evaluation of such compounds.

Fosfomycin: Uses and potentialities in veterinary medicine

Fosfomycin (FOS) is a natural bactericidal broad-spectrum antibiotic which acts on proliferating bacteria by inhibiting cell wall and early murein/peptidoglycan synthesis. Bactericidal activity is evident against Gram positive and Gram negative bacteria and can also act synergistically with other antibiotics. Bacterial resistance to FOS may be natural or acquired. Other properties of this drug include inhibition of bacterial adhesion to epithelial cells, exopolysaccharide biofilm penetration, immunomodulatory effect, phagocytosis promotion and protection against the nephrotoxicity caused by other drugs. FOS has chemical characteristics not typically observed in organic phosphoric compounds and its molecular weight is almost the lowest of all the antimicrobials. It tends to form salts easily due to its acidic nature (disodium salt, for intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration; calcium and trometamol salt: for oral (PO) administration). FOS has a very low protein binding (<0.5%) which, along with its low molecular weight and water solubility, contributes to its good diffusion into fluids (cerebrospinal fluid, aqueous and vitreous humor, interstitial fluid) and tissues (placenta, bone, muscle, liver, kidney and skin/fat). In all species, important differences in the bioavailability have been found after administration in relation to the various derivatives of FOS salts. Pharmacokinetic profiles have been described in humans, chickens, rabbits, cows, dogs, horses and weaning piglets. The low toxicity and potential efficacy of FOS are the main factors that contribute to its use in humans and animals. Thus, it has been used to treat a broad variety of bacterial infections in humans, such as localized peritonitis, brain abscesses, severe soft tissue infections, cystitis and other conditions. In veterinary medicine, FOS is used to treat infectious diseases of broiler chickens and pigs. In broilers, it is administered for the treatment of E. coli and Salmonella spp. infections. In piglets, the drug is prescribed to treat a wide variety of bacterial infections. FOS penetration is demonstrated in phagocytic, respiratory (HEP-2) and intestinal (IPEC-J2) cells. Although not widely used in animals, the drug has shown good results in human medicine. The potentialities of FOS suggest that this drug is a promising candidate for the treatment of infections in veterinary medicine. For these reasons, the aim of this work is to provide animal health practitioners with information on a drug that is not extensively recognized.

In vitro activity of fosfomycin in combination with linezolid against clinical isolates of methicillin-resistant Staphylococcus aureus

The objective of this paper was to investigate the in vitro effects of fosfomycin combined with linezolid against methicillin-resistant Staphylococcus aureus (MRSA). A total of 102 MRSA isolates isolated from clinical specimens of human infections from three hospitals in China were studied. The microdilution checkerboard method was used to determine whether combinations act synergistically against these isolates. The susceptibility results for fosfomycin and linezolid were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. Synergy and indifference were defined as a fractional inhibitory concentration index of ⩽0.5 and >0.5 but ⩽4, respectively. The combination of fosfomycin and linezolid demonstrated the following interactions: 98.04% (100/102) synergism; 1.96% (2/102) indifference; no antagonism was seen. Thus, the combination between fosfomycin and linezolid shows synergism for most of the MRSA isolates tested in this study. If these findings are confirmed in further in vitro or in vivo studies, the above combination could be tested clinically for difficulty to treat MRSA infections, particularly those warranting prolonged oral therapy.

The revival of fosfomycin

Fosfomycin, originally named phosphonomycin, was discovered in Spain in 1969. There are three forms of fosfomycin: fosfomycin tromethamine (a soluble salt) and fosfomycin calcium for oral use, and fosfomycin disodium for intravenous use. Fosfomycin is a bactericidal antibiotic that interferes with cell wall synthesis in both Gram-positive and Gram-negative bacteria by inhibiting the initial step involving phosphoenolpyruvate synthetase. It has a broad spectrum of activity against a wide range of Gram-positive and Gram-negative bacteria. It is highly active against Gram-positive pathogens such as Staphylococcus aureus and Enterococcus, and against Gram-negative bacteria such as Pseudomonas aeruginosa and Klebsiella pneumoniae. Its unique mechanism of action may provide a synergistic effect to other classes of antibiotics including beta-lactams, aminoglycosides, and fluoroquinolones. Oral fosfomycin is mainly used in the treatment of urinary tract infections, particularly those caused by Escherichia coli and Enterococcus faecalis. Intravenous fosfomycin has been administered in combination with other antibiotics for the treatment of nosocomial infections due to multidrug-resistant (MDR) Gram-positive and Gram-negative bacteria. Fosfomycin has good distribution into tissues, achieving clinically relevant concentrations in serum, kidneys, bladder wall, prostate, lungs, inflamed tissues, bone, cerebrospinal fluid, abscess fluid, and heart valves. Fosfomycin is well tolerated, with a low incidence of adverse events. Further randomized controlled trials are needed in order to evaluate the efficacy of intravenous fosfomycin for the management of nosocomial infections due to MDR pathogens.

In vitro activity of two old antibiotics against clinical isolates of methicillin-resistant Staphylococcus aureus

The objective of this paper was to investigate the in vitro effects of fusidic acid combined with fosfomycin against methicillin-resistant Staphylococcus aureus (MRSA). In all, 196 MRSA strains isolated from three clinical specimens of human infections from hospitals in China were used in this study. The checkerboard method was used to determine whether combinations act synergistically against these strains. The susceptibility results for fusidic acid and fosfomycin were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. The combination of fusidic acid and fosfomycin demonstrated the following interactions: 87.76% (172/196) synergism, 12.24% (24/196) indifference and no antagonism was seen (minimum and maximum fractional inhibitory concentration index 0.14 and 0.75, respectively). Thus, combinations of fusidic acid and fosfomycin show synergism for most of the MRSA isolates tested in this study, and may be a future therapeutic alternative for infections caused by MRSA.

Fosfomycin suppresses RS-virus-induced Streptococcus pneumoniae and Haemophilus influenzae adhesion to respiratory epithelial cells via the platelet-activating factor receptor

Human respiratory syncytial virus (RSV) sometimes causes acute and severe lower respiratory tract illness in infants and young children. The platelet-activating factor (PAF) receptor, which is a receptor for Streptococcus pneumoniae and Haemophilus influenzae, is upregulated by RSV infection in the pulmonary epithelial cell line A549. Fosfomycin, an antimicrobial agent, significantly suppressed PAF receptor induction by RSV infection at the mRNA and cell surface expression levels. Fosfomycin also suppressed RSV-induced adhesion of fluorescence-labeled S. pneumoniae and H. influenzae cells, as determined by flow cytometry and fluorescence microscopy. The RSV-induced bacterial adhesion was suggested to be host-PAF-receptor and bacterial-phosphocholine mediated. Fosfomycin, which has been shown to exhibit antimicrobial and immunomodulatory activities, was found here to suppress adhesion by disease-causing bacteria. Thus, fosfomycin might prevent secondary bacterial infection during RSV infection.

Clinical significance of the pharmacokinetic and pharmacodynamic characteristics of fosfomycin for the treatment of patients with systemic infections

The advancing antimicrobial drug resistance in common bacterial pathogens, along with the relative shortage of new antibacterial agents, call for the re-evaluation of available therapeutic options. Fosfomycin is an established treatment option for uncomplicated urinary tract infections. Here we review and evaluate the main pharmacokinetic and pharmacodynamic parameters of intravenously administered fosfomycin with regard to its use for systemic infections. Fosfomycin is a relatively small, hydrophilic agent with almost negligible serum protein binding. It is excreted unchanged in urine, achieving high concentrations for a prolonged period. Fosfomycin has good distribution into tissues, achieving clinically relevant concentrations in sites such as serum, soft tissue, lungs, bone, cerebrospinal fluid and heart valves. Fosfomycin has shown antimicrobial activity against biofilms, particularly in combination with fluoroquinolones. It also exerts immunomodulatory effects, mainly on lymphocyte and neutrophil function. Potentially useful properties of fosfomycin regarding its use in combination regimens include reduction in the expression of certain penicillin-binding proteins and attenuation of nephrotoxicity caused by several antimicrobial agents. In conclusion, the pharmacokinetic and pharmacodynamic properties of fosfomycin do not preclude its use for various types of systemic infections and suggest further research on relevant clinical applications of this agent.

Synergistic effect of fosfomycin and arbekacin on a methicillin-resistant Staphylococcus aureus-induced biofilm in a rat model

Biofilms are a major concern for clinicians in the treatment of infectious disease because of the resistance to a wide range of antibiotics. Using a rat air pouch model, methicillin-resistant Staphylococcus aureus (MRSA) growing as a biofilm was treated with a combination of fosfomycin (FOM) and arbekacin (ABK) or by the agents alone. This model has the advantage of permitting frequent sampling of exudates for bacterial counts and anti-bacterial activity, and morphological examination of the biofilm structure and inflammatory process in the pouch tissues. A clear synergistic effect was observed in the rats treated with a combination of fosfomycin and arbekacin. Morphological studies using scanning electron microscopy and histological staining showed dramatic changes of the biofilm structure as well as the inflammatory response in the rats. These results suggested an enhancement of bactericidal activity of arbekacin penetrating through the biofilm layer by virtue of fosfomycin. A possible mechanism of the synergistic effect is discussed.

Effects of the macrolide antibiotic, midecamycin, on Staphylococcus aureus product-induced Th2 cytokine response in patients with atopic dermatitis

In the present study, the effects of the macrolide antibiotic, midecamycin (MDM), on the Th2 cytokine response induced by the Staphylococcus aureus products, staphylococcal enterotoxin B (SEB), lipoteichoic acid (LTA), and peptidoglycan (PEG), was investigated in human peripheral blood mononuclear cells (PBMCs) from patients with atopic dermatitis (AD). MDM inhibited SEB-induced mRNA expression of the Th2 cytokines interleukin-4 (IL-4) and IL-5 in PBMCs from patients with AD. Furthermore, MDM also suppressed LTA-induced or PEG-induced IL-5 mRNA expression in these patients. Inhibition of mRNA expression by MDM correlated with the synthesis of cytokines in PBMCs, indicating that MDM controls Th2 cytokine production. In addition, S. aureus strains isolated from skin lesions of patients with AD were particularly susceptible to MDM compared with gentamicin, which is used widely in Japan as an antibiotic ointment combined with steroid for topical application in AD. These results suggest that topical administration of MDM might be beneficial in AD lesions infected with S. aureus.

Effects of moxifloxacin in zymogen A or S. aureus stimulated human THP-1 monocytes on the inflammatory process and the spread of infection

Antimicrobial agents have been reported to exhibit immunomodulatory and anti-inflammatory activities, both in vivo and in vitro (e.g., in human lymphocytes, macrophages and monocytes). The effects of moxifloxacin on cytokine immunomodulatory mediators, free radical generation and hydrolytic enzyme activities in zymogen A-stimulated human THP-1 monocytes were evaluated. An increase in c-AMP levels, protein kinase C activity, and the release of nitric oxide and hydrogen peroxide with a decrease in pH occurred within the first hour. Further, the effects of moxifloxacin were reduced by agents which blocked the oxygen burst, lysosome-phagosome fusion, and the energy generation within the cell. After 4 h, there was a decrease in NAG and cathepsin D activities, lipid peroxidation and the release of pro-inflammatory cytokines. These data indicate that moxifloxacin may modify the acute-phase inflammatory responses through inhibition of cytokine release in monocytes. Moxifloxacin inhibited the release of TNFalpha, IL-1, IL-6, and IL-8 in a concentration-dependent manner across a range of 0.004 to 4 microg/mL. After 4 h, there was a decrease in the release of these cytokines, thus interfering with the inflammation process to reduce infection and its spread. The effects of moxifloxacin appear initially to activate monocytes to kill bacteria through the innate immune process by releasing ROS and lysosomal hydrolytic enzymes as well as phagocytosis of the organism. At a later time the bacteria are killed through a Bacterialstatic mechanism of protein synthesis inhibition and there is a reversal of the effects of moxifloxacin on cytokine release, free radical generation and hydrolytic enzymes so that lipid peroxidation and tissue destruction by the infection process is suppressed.

Effects of alatrofloxacin, the parental prodrug of trovafloxacin, on phagocytic, anti-inflammatory and immunomodulation events of human THP-1 monocytes

Alatrofloxacin functions similar to other fluoroquinolone antibiotics in that it not only has antibiotic activity to kill invading organisms by interfering with DNA synthesis, it possesses immunosuppressive activity. In the first hour after bacteria have been phagocytosed by THP-1 monocytes, the drug activates a lytic mechanism involving the release of c-AMP, tumor necrosis factor (TNFalpha), interleukin-1 (IL-1), IL-6 and nitric oxide, with elevations in lysosomal hydrolytic enzyme activities. This effect reverses between 2 and 4 h. At this time, all of these inflammatory processes are returned to normal values or below suggesting that alatrofloxacin reduces the spread of infection and destruction of tissue related to inflammation.

Fosfomycin inhibits NF-kappaB activation in U-937 and Jurkat cells

Fosfomycin exerts anti-inflammatory effects through inhibiting the production of proinflammatory cytokines. Transcription of the genes for these proinflammatory cytokines is regulated by NF-kappaB. We tested the hypothesis that fosfomycin inhibits the activation of NF-kappaB induced by tumor necrosis factor-alpha (TNF-alpha) in human monocytic U-937 cells, and a T cell line (Jurkat). Western blot analysis demonstrated that fosfomycin inhibits NF-kappaB activation in both cells. Flow cytometry revealed that fosfomycin suppresses NF-kappaB activation in both cells in a dose-related manner. These findings are consistent with the idea that fosfomycin suppresses the production of proinflammatory cytokines via inhibition of NF-kappaB activation.

Modulatory effect of fosfomycin on acute inflammation in the rat air pouch model

We examined the effect of fosfomycin (FOM) on the inflammatory response induced by carrageenan in the rat. Air pouches were induced subcutaneously on the backs of rats and injected with carrageenan. The rats were treated with either vehicle or FOM at a dose of 100 mg/kg 1 h before carrageenan challenge. After carrageenan challenge (48 h), the air pouches were removed and analyzed. The volume, protein amounts and cell counts in the exudate obtained from FOM-treated animals were significantly reduced compared with that from vehicle-treated animals. The contents of PGE(2) and TNF-alpha, and mRNA for cyclooxygenase-2 were also markedly suppressed in FOM-treated rats. Histological examination showed suppression of the inflammatory response in the pouch tissues from FOM-treated rats.

Mechanisms of clinically relevant drug interactions associated with tacrolimus

The clinical management of tacrolimus, a macrolide used as immunosuppressant after transplantation, is complicated by its narrow therapeutic index in combination with inter- and intraindividually variable pharmacokinetics. As a substrate of cytochrome P450 (CYP) 3A enzymes and P-glycoprotein, tacrolimus interacts with several other drugs used in transplantation medicine, which also are known CYP3A and/or P-glycoprotein inhibitors and/or inducers. In clinical studies, CYP3A/P-glycoprotein inhibitors and inducers primarily affect oral bioavailability of tacrolimus rather than its clearance, indicating a key role of intestinal P-glycoprotein and CYP3A. There is an almost complete overlap between the reported clinical drug interactions of tacrolimus and those of cyclosporin. However, in comparison with cyclosporin, only few controlled drug interaction studies have been carried out, but tacrolimus drug interactions have been extensively studied in vitro. These results are inconsistent and are of poor predictive value for clinical drug interactions because of false negative results. P-glycoprotein regulates distribution of tacrolimus through the blood-brain barrier into the brain as well as distribution into lymphocytes. Interaction of other drugs with P-glycoprotein may change tacrolimus tissue distribution and modify its toxicity and immunosuppressive activity. There is evidence that ethnic and gender differences exist for tacrolimus drug interactions. Therapeutic drug monitoring to guide dosage adjustments of tacrolimus is an efficient tool to manage drug interactions. In the near future, progress can be expected from studies evaluating potential pharmacokinetic interactions caused by herbal preparations and food components, the exact biochemical mechanism underlying tacrolimus toxicity, and the potential of inhibition of CYP3A and P-glycoprotein to improve oral bioavailability and to decrease intraindividual variability of tacrolimus pharmacokinetics.

Fosfomycin inhibits neutrophil function via a protein kinase C-dependent signaling pathway

We investigated effects of fosfomycin (FOM) on neutrophil function, specifically the oxidative burst and adhesion molecule expression (CD11b/CD18, or MAC-1) using flow cytometry assay. Preincubation of polymorphonuclear leukocytes (PMNL) with FOM from 1 to 100 microg/ml prior to stimulation by phorbol 12-myristate 13-acetate (PMA, 2 ng/ml) significantly suppressed the oxidative burst in a concentration-dependent manner. However, FOM did not affect the oxidative burst of PMNL stimulated by a chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (FMLP). Stimulation with PMA (2 ng/ml) caused a rapid up-regulation of CD11b surface expression on PMNL, followed by time-dependent loss of this receptor. FOM also suppressed loss of CD11b in PMNL stimulated by PMA. FOM then inhibits the PMA-induced oxidative burst and CD11b epitope loss in PMNL. The suppressive effect appears to be mediated by the protein kinase C-dependent signaling pathway.

Modulatory effect of macrolide antibiotics on the Th1- and Th2-type cytokine production

The effect of the macrolide antibiotics, clarithromycin, midecamycin acetate and josamycin, on the generation of Th1- and Th2-type cytokines by mitogen-stimulated human T lymphocytes was compared with that of fosfomycin. The following results were obtained. These drugs demonstrated potent inhibitory activity on the release and gene expression of TNF-alpha and IL-2. Their inhibitory effect on IFN-alpha, IL-4, IL-5, IL-6 was less marked. The release of IL-10 was poorly suppressed. Clarithromycin had the most potent inhibitory effect of the drugs used. The present results suggested that anti-bacterial agents might modify the host's immunological response by interfering with the activity of T helper cells.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Effects of aztreonam on natural immunity in mice

The influence of the dose and the duration of treatment with aztreonam, a monocyclic beta-lactam antibiotic, on the natural immune response of mice has been investigated. The results show the effects induced by the antibiotic on several immune parameters were affected by the duration of treatment. Thus, treatment with 28 mg/kg per day of aztreonam over 14 days increased every immune parameter tested, while treatment with 57 mg/kg per day of aztreonam for 7 days only enhanced the natural killer (NK) activity of splenocytes. Since aztreonam does not apparently impair the innate immune response, it might be a suitable therapy for the treatment of patients who are immunosuppressed.

Fosfomycin, an antibiotic, possessed TGF-beta-like immunoregulatory activities

The regulatory effects of fosfomycin (FOM) were correlated closely with the multifunction of TGF-beta in the modulation of immune responses in vivo and in vitro. LPS-induced polyclonal IgM and IgG antibody responses were depressed at 3 days after the initial culture and subsequently enhanced at day 10 by FOM or TGF-beta. Neither FOM nor TGF-beta inhibited LPS-induced IgA antibody responses, whereas dexamethasone (DX) reduced polyclonal IgM, IgG and IgA antibody responses wholly. The suppression of antibody responses and Mv1Lu cell proliferation induced by FOM or TGF-beta was partly overcome with soluble TFG-beta receptors (sRIII). Oral, i.v. and i.p. administration of FOM exhibited similar enhanced SRBC-specific antibody responses to that seen after oral administration of TGF-beta. The addition of FOM and latent TGF-beta inhibited the proliferation of Mv1Lu cells, but FOM did not lead to an increase in plasmin activities, which convert latent to active TGF-beta, and further the expression of TGF-beta receptors on the cell surface. In addition, FOM failed to enhance TGF-beta secretion. These findings suggest that immunomodulation of FOM results in increased sensitivity of cells to TGF-beta.

Fosfomycin (FOM: 1 R-2S-epoxypropylphosphonic acid) suppress the production of IL-8 from monocytes via the suppression of neutrophil function

We investigated the influence of fosfomycin (FOM) on the production and the mRNA expression of interleukin-8 (IL-8) by monocytes. In the incubation of whole blood stimulated by N-Formyl-Met-Leu-Phe (FMLP), FOM significantly suppressed the production and the mRNA expression of IL-8 by monocytes and its inhibitory action was concentration-dependent (FOM: 50-200 microg/ml). However, FOM did not influence the production and the mRNA expression of IL-8 in the incubation of fractionated mononuclear cell stimulated by FMLP. The supernatant of FMLP-stimulated polymorphonuclear leukocyte (PMNL) could induce the mRNA expression of IL-8 by monocyte. The supernatant of FMLP-stimulated PMNL which was pre-treated with FOM significantly (P < 0.05) inhibited the expression of IL-8 mRNA by monocyte. Moreover, FOM suppressed the production of leukotriene B4 (LTB4) from neutrophil in a concentration-dependent manner. When LTB4 was added to the fractionated mononuclear cells directory, the expression of IL-8 mRNA was enhanced (P < 0.05). The present study indicated that FOM suppress the production of LTB4 from neutrophils and suppress the expression of IL-8 mRNA by LTB4 from monocytes. It was also demonstrated that LTB4 produced by neutrophil is one of the factor which promotes the expression of IL-8 mRNA in monocytes.

Fosfomycin reduces CD15s-related antigen expression of Streptococcus pyogenes

We have previously shown the immunological mimicry of human sialyl-Lewis(x) (CD15s) by a surface antigen of Streptococcus pyogenes. This mimicking surface antigen may act as a ligand to the selectin family and may induce antibody production against CD15s on host cells, suggesting a possible role in the pathogenesis of S. pyogenes. In this study, the effects of antibiotics on the CD15s-related antigen expression of S. pyogenes were examined at a concentration below the MIC (sub-MIC). The amounts of CD15s on the surfaces of S. pyogenes cells and on the surfaces of S. pyogenes biofilms were determined by a whole-cell enzyme-linked immunosorbent assay and by laser scanning fluorescence microscopy, respectively, by using an anti-CD15s monoclonal antibody. At the sub-MICs, fosfomycin (1R,2S-1,2-epoxypropyl phosphonic acid), its enantiomer (1S,2R-1,2-epoxypropyl phosphonic acid), and benzylpenicillin significantly inhibited the CD15s expression of all strains studied. The effects of fosfomycin and its enantiomer on biofilms were also observed by scanning electron microscopy. Incubation of S. pyogenes with the sub-MIC of fosfomycin or its enantiomer, which has no antibacterial activity, reduced the amount of CD15s on the biofilm surface and made it smooth. These results suggest that fosfomycin or its enantiomer might be useful for preventing S. pyogenes adherence to human CD15s receptors and the resulting immunological pathogenicity.

Alteration of cytokine levels by fosfomycin and prednisolone in spontaneous proliferation of cultured lymphocytes from patients with HTLV-I-associated myelopathy (HAM/TSP)

Fosfomycin has recently been reported as an antibiotic with immunomodulatory activities. To evaluate the possibility of clinical administration of fosfomycin in patients with human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), the effects of this agent on the HTLV-I-induced in vitro phenomenon were studied. The influence of fosfomycin on in vitro spontaneous proliferation (SP) of peripheral blood mononuclear cells (PBMCs) from four patients with HAM/TSP was measured by thymidine incorporation into the cells, and the concentration of several cytokines in the culture supernatants was examined in three HAM/TSP patients. Enzyme-linked immunosorbent assays (ELISAs) were employed to detect the concentrations of interleukin-4 (IL-4), IL-6, IL-10, interferon-gamma (IFN-gamma), transforming growth factor-beta1 (TGF-beta1), and macrophage inflammatory protein-1alpha (MIP-1alpha). The data were compared to the changes by prednisolone which is known to regulate the HTLV-I-associated in vitro phenomenon and to have a therapeutic benefit in patients with HAM/TSP. Production of IL-6, IFN-gamma and MIP-1alpha from the spontaneously proliferating cells were demonstrated. Fosfomycin could not suppress the HTLV-I-associated SP, but had the properties to decrease the levels of TGF-beta1 and MIP-1alpha. It was also demonstrated that the concentrations of IFN-gamma and MIP-1alpha in the cultures in the presence of prednisolone were apparently decreased, suggesting a possible involvement of these cytokines in the pathogenesis of HAM/TSP. These findings support the hypothesis that fosfomycin may have immunomodulatory potentials in HTLV-I-related cellular interactions in a different manner from ordinary immunomodulatory agents.

Immunomodulating effect of fosfomycin on gut-derived sepsis caused by Pseudomonas aeruginosa in mice

We evaluated the protective effect of fosfomycin (FOM) and an enantiomer of fosfomycin [FOM (+); an isomer of FOM with no bactericidal activity] on murine gut-derived sepsis caused by Pseudomonas aeruginosa. Endogenous bacteremia was induced by administering cyclophosphamide (CY) and ampicillin to specific-pathogen-free mice fed P. aeruginosa. Treatment of mice with FOM at 250 mg/kg of body weight per day twice a day after the second CY administration significantly increased the survival rate compared to that for control mice treated with saline. Treatment with FOM (+) at 20 and 100 mg/kg also significantly increased the survival rate (from 30% for control mice to 80% for treated mice). The bacterial counts in the liver and blood were both significantly lower in FOM(+)-treated mice in comparison with those in liver and blood of saline-treated control mice. FOM(+) administration affected neither the bacterial colonization in the intestinal tract nor the leukocyte counts in the peripheral blood of the mice. After intravascular inoculation of P. aeruginosa, treatment of mice with FOM (+) did not enhance bacterial clearance from the blood of mice pretreated or not enhance bacterial clearance from the blood of mice pretreated or not pretreated with CY, FOM(+) significantly suppressed tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 levels in the serum of mice after gut-derived sepsis. These results indicate that both FOM and FOM(+) have protective effects against P. aeruginosa bacteremia, despite a lack of specific activity of FOM(+), and suggest that FOM may possess immunomodulating activity and that it induces a protective effect. The protective mechanism is speculated to be that FOM modulates the vivo production of inflammatory cytokines.

The immunomodulatory effects of antibiotics: in vitro and ex vivo investigations of 21 substances by means of the lymphocyte transformation test

Besides their antimicrobial activity antibiotics can modulate immune response. The paper provides original data about in vitro and in vivo influence of antibiotics on lymphocyte transformation test (LTT) and gives a comprehensive overview of literature data. In the study presented here the influence of several antimicrobial substances on unstimulated and PHA-stimulated lymphocyte transformation was investigated. The proliferative response was measured as (3H) thymidine uptake by lymphocytes. For initial screening the lymphocyte transformation test was performed on murine lymphocytes in vitro. As a whole 21 antimicrobial substances were tested including representative substances of the most important main groups. As a second step experiments were done with selected substances on human lymphocytes that had shown a distinct influence on murine cells in vitro. At therapeutic concentrations a pronounced stimulation of murine lymphocyte transformation was caused by carbapenems, aminothiazole cephalosporins and imidazoles. Purine analogs had only suppressive effects. However, the increased (3H) thymidine uptake in murine cells could not be regularly reproduced in human lymphocytes and in ex vivo experiments.

Modulatory effect of antibiotics on cytokine production by human monocytes in vitro

Some antimicrobial agents have been reported to modify the host immune and inflammatory responses both in vivo and in vitro. Fosfomycin (FOM) and clarithromycin (CAM) have immunomodulatory activity on human lymphocyte function. In the present study, we examined the effects of FOM and CAM on cytokine synthesis by lipopolysaccharide (LPS)-stimulated human monocytes in comparison with that of dexamethasone in vitro. The three drugs demonstrated positive or negative effects on the synthesis of various cytokines by LPS-primed monocytes. They suppressed the synthesis of tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-1 beta, the IL-1 receptor antagonist, and granulocyte-macrophage colony-stimulating factor in a concentration-dependent manner at concentrations between 1.6 and 40 micrograms/ml. On the contrary, the drugs showed different actions on the synthesis of IL-6 and IL-10. Namely, FOM enhanced both IL-6 and IL-10 synthesis, CAM enhanced only IL-10 synthesis, but dexamethasone deeply suppressed the synthesis of both cytokines. These data indicate that antibacterial agents may modify acute-phase inflammatory responses through their effects on cytokine synthesis by monocytes.

The effect of combination splenectomy and low-dose FK506 therapy on graft survival after liver allograft transplantation in rats

The effect of splenectomy on allograft survival was investigated using orthotopic liver transplantation in a rat experimental model (ACI rat liver grafted to LEW rat). Control rats without any immunosuppressive treatment died, on average, 10.4 +/- 1.4 days after operation. Splenectomy alone somewhat prolonged the survival (13.4 +/- 2.0 days), and low-dose FK506 therapy moderately prolonged it (22.7 +/- 7 days). The graft survival period was significantly prolonged (39.7 +/- 6.3 days) when them two treatments were combined. The elevation of cytotoxic antiallograft antibodies was suppressed by splenectomy but not by low-dose FK506 therapy. The development of jaundice was moderately suppressed by FK506 but not by splenectomy. There was no difference between the pattern of body weight decline in either of them two groups and that in control rats. When these two treatments were combined at the same time, the elevation of cytotoxic antibodies, development of jaundice and decline of body weight were suppressed. These data indicate that B cells play an important role in the acute rejection of the rat liver allograft at least partially via production of cytotoxic antiallograft antibody. Splenectomy or other immunosuppressive methods affecting B cells can be a supplement for immunosuppression when using reduced-dose FK506.

Immunomodulatory effects of three macrolides, midecamycin acetate, josamycin, and clarithromycin, on human T-lymphocyte function in vitro

The effect of three macrolide antibiotics, midecamycin acetate, josamycin, and clarithromycin, on human T-cell function was investigated in vitro. Midecamycin acetate and josamycin suppressed the proliferative response of peripheral blood mononuclear cells stimulated by polyclonal T-cell mitogens at concentrations between 1.6 and 8 micrograms/ml. At higher concentrations (40 to 200 micrograms/ml), all these drugs showed a marked inhibitory effect. At concentrations of 1.6 to 40 micrograms/ml, these drugs suppressed interleukin-2 (IL-2) production induced by mitogen-stimulated T cells, but not the expression of IL-2 receptor (CD25), in a dose-dependent manner. Therefore, the suppressive action on T-lymphocyte proliferation seems to be based on the ability of these drugs to inhibit IL-2 production by T cells. The drug also inhibited mixed lymphocyte reaction at the same concentrations. Combined treatment with these macrolides and the known immunosuppressants such as FK506 and cyclosporin A resulted in an increased inhibition of T-cell proliferation. The immunomodulatory properties of the antibiotics may have clinical relevance for modulation of the immune response in transplant patients and in patients with inflammatory diseases.