The human lactoferrin-derived peptide hLF1-11 primes monocytes for an enhanced TLR-mediated immune response.

Earlier we reported that the peptide corresponding to the first eleven N-terminal amino acids of human lactoferrin (hLF1-11) is active against multi-drug resistant pathogens in mice. The mechanisms underlying this anti-infective activity remain unclear. Since hLF1-11 is ineffective against pathogens at physiological salt concentrations and hLF1-11 directs differentiation of monocytes toward a macrophage subset with enhanced effector functions, we investigated the effects of hLF1-11 on human and murine monocytes. Results revealed that human and murine monocytes exposed for 1 h to hLF1-11 and then stimulated with the Toll-like receptor (TLR)-ligand LPS for 18 h, displayed enhanced cytokine and chemokine production as compared to control (peptide-treated) monocytes. We also found that expression of mRNA, cell-surface receptor expression, and NF-kappaB activation by hLF1-11-exposed human monocytes were enhanced as compared to control (peptide-treated) monocytes. Furthermore, the kinetics of the cytokine production was unchanged as mRNA levels and protein levels paralleled the enhanced response of hLF1-11-exposed monocytes to LPS. The cytokine production by human monocytes in response to TLR4, TLR5, and TLR7 stimulation, but not to TLR2 stimulation, was elevated by hLF1-11. In concordance, translocation of NF-kappaB subunits to the nucleus was enhanced in hLF1-11-exposed monocytes after TLR stimulation, except for TLR2, as compared to control (peptide-exposed) monocytes. In conclusion, monocytes were primed by hLF1-11 for an enhanced inflammatory response upon TLR4, TLR5, and TLR7 stimulation, but not TLR2 stimulation. Such effects of hLF1-11 on monocyte reactivity should be taken into account when considering the clinical development of this peptide for a therapeutic intervention in patients.

The pharmacology of radiolabeled cationic antimicrobial peptides.

Cationic antimicrobial peptides are good candidates for new diagnostics and antimicrobial agents. They can rapidly kill a broad range of microbes and have additional activities that have impact on the quality and effectiveness of innate responses and inflammation. Furthermore, the challenge of bacterial resistance to conventional antibiotics and the unique mode of action of antimicrobial peptides have made such peptides promising candidates for the development of a new class of antibiotics. This review focuses on antimicrobial peptides as a topic for molecular imaging, infection detection, treatment monitoring and additionally, displaying microbicidal activities. A scintigraphic approach to studying the pharmacokinetics of antimicrobial peptides in laboratory animals has been developed. The peptides were labeled with technetium-99m and, after intravenous injection into laboratory animals, scintigraphy allowed real-time, whole body imaging and quantitative biodistribution studies of delivery of the peptides to the various body compartments. Antimicrobial peptides rapidly accumulated at sites of infection but not at sites of sterile inflammation, indicating that radiolabeled cationic antimicrobial peptides could be used for the detection of infected sites. As the number of viable micro-organisms determines the rate of accumulation of these peptides, radiolabeled antimicrobial peptides enabled to determine the efficacy of antibacterial therapy in animals to be monitored as well to quantify the delivery of antimicrobial peptides to the site of infection. The scintigraphic approach provides to be a reliable method for investigating the pharmacokinetics of small cationic antimicrobial peptides in animals and offers perspective for diagnosis of infections, monitoring antimicrobial therapy, and most important, alternative antimicrobial treatment infections with multi-drug resistant micro-organisms in humans.

Synthetic peptides derived from human antimicrobial peptide ubiquicidin accumulate at sites of infections and eradicate (multi-drug resistant) Staphylococcus aureus in mice.

The presence and antimicrobial activity of antimicrobial peptides (AMPs) has been widely recognized as an evolutionary preserved part of the innate immune system. Based on evidence in animal models and humans, AMPs are now positioned as novel anti-infective agents. The current study aimed to evaluate the potential antimicrobial activity of ubiquicidin and small synthetic fragments thereof towards methicillin resistant Staphylococcus aureus (MRSA), as a high priority target for novel antibiotics. In vitro killing of MRSA by synthetic peptides derived from the alpha-helix or beta-sheet domains of the human cationic peptide ubiquicidin (UBI 1-59), allowed selection of AMPs for possible treatment of MRSA infections. The strongest antibacterial activity was observed for the entire peptide UBI 1-59 and for synthetic fragments comprising amino acids 31-38. The availability, chemical synthesis opportunities, and size of these small peptides, combined with their strong antimicrobial activity towards MRSA make these compounds promising candidates for antimicrobial therapy and detection of infections in man.

Beneficial effects of alkaline phosphatase in septic shock.

OBJECTIVE: Alkaline phosphatase may decrease the harmful effects of lipopolysaccharide by detoxifying lipid A. The aim of this study was to investigate whether administration of alkaline phosphatase is beneficial in a clinically relevant septic shock model. DESIGN: Interventional laboratory study. SETTING: University hospital animal research laboratory. SUBJECTS: Fourteen fasted, anesthetized, invasively monitored, mechanically ventilated, female sheep (27.6 +/- 3.9 kg). INTERVENTIONS: Each animal received 1.5 g/kg body weight of feces intraperitoneally to induce sepsis. Ringer's lactate and a 6% hydroxyethyl starch solution were infused throughout the experiment to prevent hypovolemia. Two hours after feces injection, animals were randomized to alkaline phosphatase (60 units/kg intravenous bolus followed by a continuous infusion of 20 units/kg/hr for a total of 15 hrs) or no alkaline phosphatase (control group). MEASUREMENTS AND MAIN RESULTS: All animals were studied until their spontaneous death or for a maximum of 30 hrs. Plasma alkaline phosphatase concentrations decreased in the control group but increased in the treatment group following alkaline phosphatase administration. In the treatment group, the Pao2/Fio2 ratio was higher (p < .05), blood interleukin-6 concentrations were lower (p < .05), and the survival time was longer (median time 23.8 vs. 17 .0 hrs, p < 0.05) than in the control group. There were no significant differences in systemic hemodynamics or diuresis. CONCLUSIONS: In this clinically relevant septic shock model, alkaline phosphatase administration improved gas exchange, decreased interleukin-6 concentrations, and prolonged survival time.

Bovine intestinal alkaline phosphatase attenuates the inflammatory response in secondary peritonitis in mice.

Lipopolysaccharide (LPS) contributes importantly to morbidity and mortality in sepsis. Bovine intestinal alkaline phosphatase (BIAP) was demonstrated to detoxify LPS through dephosphorylation. LPS injection combined with BIAP reduced inflammation and improved survival in various experimental settings. In this study, single-dose intravenous administration of BIAP (0.15 IU/g) was applied in a murine cecal ligation and puncture (CLP) model of polymicrobial sepsis. Saline was given as control (S group). Treatment with BIAP prior to CLP (prophylaxis; BIAP-P group) or shortly after (early treatment; BIAP-ET group) reduced cytokine concentrations in plasma and peritoneal lavage fluid (PLF). Tumor necrosis factor-alpha peak levels decreased from 170 pg/ml (S) to 57.5 (BIAP-P) and 82.5 (BIAP-ET) in plasma and in PLF from 57.5 pg/ml (S) to 35.3 (BIAP-P) and 16.8 (BIAP-ET) (all, P < 0.05). Peak interleukin-6 levels in plasma decreased from 19.3 ng/ml (S) to 3.4 (BIAP-P) and 11.5 (BIAP-ET) and in PLF from 32.6 ng/ml (S) to 13.4 (BIAP-P) and 10.9 (BIAP-ET) (all, P < 0.05). Macrophage chemoattractant protein 1 peak levels in plasma decreased from 2.0 ng/ml (S) to 1.0 (BIAP-P) and 0.7 (BIAP-ET) and in PLF from 6.4 (S) to 2.3 (BIAP-P) and 1.3 ng/ml (BIAP-ET) (all, P < 0.05). BIAP-treated groups showed decreased transaminase activity in plasma and decreased myeloperoxidase activity in the lung, indicating reduced associated hepatocellular and pulmonary damage. Survival was not significantly altered by BIAP in this single-dose regimen. In polymicrobial secondary peritonitis, both prophylactic and early BIAP treatment attenuates the inflammatory response both locally and systemically and reduces associated liver and lung damage.

Drug-induced autoantibody formation in mice: triggering by primed CD4+CD25- T cells, prevention by primed CD4+CD25+ T cells.

Although the ability of CD4+CD25+ T suppressor (Ts) cells to prevent experimental autoimmune diseases has been described, nothing is known concerning their role and mechanism of action in xenobiotic-induced autoimmunity. Procainamide, mercuric chloride, and gold(I) are three xenobiotics that can induce autoimmune reactions in humans and rodents. After the induction of IgG1 antinuclear autoantibodies (ANA) in mice treated with either of the above xenobiotics, adoptive transfer of their CD4+CD25+ T cells completely prevented ANA formation in recipients treated with the same xenobiotic; transfer of CD8+ T cells was ineffective. Furthermore, xenobiotic-primed CD4+CD25+ T cells could also partially prevent ANA formation in recipients treated with a different xenobiotic. CD4+CD25- T cells from xenobiotic-treated donors failed to suppress, but induced de novo IgG1 ANA formation in untreated recipients. Our findings suggest that during xenobiotic treatment T cell reactivity may spread from xenobiotic-induced, nucleoprotein-related neoantigens to peptides of the unaltered nucleoproteins.

Calf intestinal alkaline phosphatase, a novel therapeutic drug for lipopolysaccharide (LPS)-mediated diseases, attenuates LPS toxicity in mice and piglets.

It has been demonstrated that human placental alkaline phosphatase (HPLAP) attenuates the lipopolysaccharide (LPS)-mediated inflammatory response, likely through dephosphorylation of the lipid A moiety of LPS. In this study, it is demonstrated that also alkaline phosphatase derived from calf intestine (CIAP) is able to detoxify LPS. In mice administered CIAP, 80% of the animals survived a lethal Escherichia coli infection. In piglets, previous to LPS detoxification, the pharmacokinetic behavior of CIAP was studied. CIAP clearance was shown to be dose-independent and showed a biphasic pattern with an initial t1/2 of 3 to 5 min and a second phase t1/2 of 2 to 3 h. Although CIAP is cleared much faster than HPLAP, it attenuates LPS-mediated effects on hematology and tumor necrosis factor-alpha responses at doses up to 10 microg/kg in piglets. LPS-induced hematological changes were antagonized, and the tumor necrosis factor-alpha response was reduced up to 98%. Daily i.v. bolus administration of 4000 units CIAP, the highest dose used in the LPS intervention studies, in piglets for 28 days was tolerated without any sign of toxicity. Therefore, CIAP potentially encompasses a novel therapeutic agent in the treatment of LPS-mediated diseases. Based on the data mentioned above, human clinical trials have been initiated.

Allelic variants of drug metabolizing enzymes as risk factors in psoriasis.

The onset or exacerbation of psoriasis, a T-cell-dependent skin disease with autoimmune features, can be triggered by drugs such as antimalarials and beta-blockers. Xenobiotics may also play a role in idiopathic psoriasis. It has been hypothesized that different metabolic efficiencies caused by variant alleles of xenobiotic metabolizing enzymes could lead to the accumulation of xenobiotics or their reactive metabolites in target organs. Subsequently, neoantigens or cryptic peptides could be presented and initiate an aggressive T cell response. In this context, we analyzed a broad array of xenobiotic metabolizing enzymes in up to 327 Caucasian psoriasis patients and compared them to 235 control persons. Alleles tested include four phase I and three phase II enzymes. Significantly more carriers of the variant alleles of CYP1A1 (alleles *2A and *2C) were found in healthy controls than in patients, suggesting a protective role for these alleles. No significant difference between patients and controls could be found, however, for the other phase I alleles 1B1*1 and 1B1 *3, 2C19*1A and 2C19*2A, and 2E1*1A and 2E1*5B. Of the variant alleles coding for phase II enzymes only GSTM1, but not GSTT1 or NQOR, correlated with a risk to contract psoriasis. Some combinations of phase I and phase II enzymes suggested protective or risk-associated effects. Interestingly, heterozygosity for CYP2C19 alleles *1A and *2A was associated with increased risk for "late onset" psoriasis, whereas this genotype was protective for psoriatic arthritis. This is the first large-scale study on these enzymes and the results obtained support the concept that different activities of metabolizing enzymes can contribute to disease etiology and progression.

Cross-sensitization to haptens: formation of common haptenic metabolites, T cell recognition of cryptic peptides, and true T cell cross-reactivity.

To analyze T cell cross-reactivity to para-compounds, we established CD4(+) T cell hybridomas from mice immunized with adducts of self-globin and one of three different para-compounds: p-aminophenol, p-phenylenediamine, or Bandrowski's base. Some of the hybridomas obtained reacted not only to the immunizing antigen, but also to metabolically related para-compounds, bound to the same protein, thus suggesting formation of common metabolites. Other hybridomas cross-reacted to globin adducts of metabolically unrelated para-compounds, which denotes them as truly cross-reactive cells whose TCR failed to distinguish among the different haptens. One of these hybridomas also reacted against a non-haptenated, cryptic peptide of hemoglobin but not to the full-length native protein. As this hybridoma reacted even more strongly to the respective peptide after it was haptenated, recognition of the native, cryptic peptide was apparently due to true cross-reactivity. To conclude, true T cell cross-reactivity to haptens does occur, as well as the formation of a common reactive metabolite, and T cell recognition of cryptic self-peptides may underlie cross-sensitization to chemicals.