Abstracts of the 7th International Conference on Lactoferrin / Résumés de la 7e Conférence internationale sur la lactoferrine

The article presents abstracts on lactoferrin research. They include "Oral administration of lactoferrin raises NK cell activity in mice,"Comparison of antimicrobial activity between lactoferricin B 15 derivative and antibiotics" and "Batch extraction of lactoferrin from raw whole milk.

Lactoferrin. A natural glycoprotein involved in iron and inflammatory homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 µg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes

Human Milk Lactoferrin and Antibodies: Catalytic Activities, Complexes, and Other Features

Human milk is a source of biologically active proteins, including lactoferrin (LF) and antibodies (Abs). These proteins are considered as the most polyfunctional proteins of human milk. Apparently, human milk is not a simple mixture of proteins and peptides: recently it was shown that human milk contains stable supramolecular protein complex, composed of LF, α‐lactalbumin, milk albumin, β‐casein, IgG, and sIgA molecules. We believe that the whole set of different biological functions of the individual milk proteins is significantly supplemented by features of their complexes

Diverse structural approaches to haem appropriation by pathogenic bacteria

The critical need for iron presents a challenge for pathogenic bacteria that must survive in an environment bereft of accessible iron due to a natural low bioavailability and their host's nutritional immunity. Appropriating haem, either direct from host haemoproteins or by secreting haem-scavenging haemophores, is one way pathogenic bacteria can overcome this challenge. After capturing their target, haem appropriation systems must remove haem from a high-affinity binding site (on the host haemoprotein or bacterial haemophore) and transfer it to a binding site of lower affinity on a bacterial receptor. Structural information is now available to show how, using a combination of induced structural changes and steric clashes, bacteria are able to extract haem from haemophores, haemopexin and haemoglobin. This review focuses on structural descriptions of these bacterial haem acquisition systems, summarising how they bind haem and their target haemoproteins with particularly emphasis on the mechanism of haem extraction

Characterization of the Gonococcal Calprotectin Zn-Acquisition System, TdfH, and the Efficacy of Metal Starvation for Treating Gonococcal Disease

Abstract Characterization of the Gonococcal Calprotectin Zn-Acquisition System, TdfH, and the Efficacy of Metal Starvation for Treating Gonococcal Disease. By Michael T. Kammerman, B.S. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University Virginia Commonwealth University, 2020 Major Director: Cynthia Nau Cornelissen, Ph.D. Professor, Department of Microbiology and Immunology Neisseria gonorrhoeae, the bacterial agent that is responsible for the human disease gonorrhea, has had a steady increase in the number of infections per year. In 2018 the WHO estimated over 87 million infections occurred world-wide, and the CDC estimated that over 800,000 infections happened in the United States. Accompanying the increase in gonococcal infections per year is the increase in the number of antibiotic resistant isolates being recovered. The recent recovery of a gonococcal isolate that was resistant to the current CDC recommended dual-treatment, coupled with the lack of a preventative vaccine, marks the beginning of an era where there may be no effective treatments for gonococcal disease. The gonococcus possesses a conserved set of proteins that enables it to pirate metal ions from host proteins, and is essential in order for N. gonorrhoeae to establish an infection in the human urogenital tract. The importance of TdTs for gonococcal survival and their sequence conservation make them ideal candidates to be included in a gonococcal vaccine, or as targets for potential new therapeutics that are capable of disrupting the interaction with their ligands. In this study we developed a competition assay and probed gonococcal cells with either human (hCP) or mouse calprotectin (mCP) to determine if the gonococcus is species restricted for its ligand interaction. We also performed Isothermal Titration Calorimetry experiments to characterize the binding affinity between the gonococcal calprotectin (CP) binding protein TdfH and calprotectin. In this study we also continued a mutational and small molecule analysis of TbpA aimed at disrupting the interaction with its ligand, human transferrin (hTf). Finally, we investigated if the gonococcal efflux pump, MacA, was responsible for heme export via heme-dependent growth assays of a MacA deficient gonococcal strain. We report that the interaction between TdfH and hCP is high affinity and that the Zn piracy of TdfH occurs optimally at the non-canonical metal binding site of hCP known as site 1. We determined that multiple mutations, both in the loop 3 helix and in loop 2 of TbpA, minimally reduce the total binding of hTf, similar to what Cash et al. has previously described. A screening of a database of small molecules found that several first-generation small molecules were able to significantly reduce the ability of TbpA to interact with hTf. Finally, we found that the efflux pump MacA, does not meaningfully contribute to gonococcal heme export. However, more in-depth studies interrogating MacA substrates are still needed. These studies determined the species specificity of the gonococcal calprotectin binding protein and found that Zn- piracy occurs optimally from one specific site on hCP. This study also shows the promise in investing in new therapeutics that disrupt TdT function

Crystal structure of Pasteurella haemolytica ferric ion-binding protein a reveals a novel class of bacterial iron-binding proteins

Pasteurellosis caused by the Gram-negative pathogen Pasteurella haemolytica is a serious disease leading to death in cattle. To scavenge growth-limiting iron from the host, the pathogen utilizes the periplasmic ferric ion-binding protein A (PhFbpA) as a component of an ATP-binding cassette transport pathway. We report the 1.2-Angstrom structure of the iron-free (apo) form of PhFbpA, which is a member of the transferrin structural superfamily. The protein structure adopts a closed conformation, allowing us to reliably assign putative iron-coordinating residues. Based on our analysis, PhFbpA utilizes a unique constellation of binding site residues and anions to octahedrally coordinate an iron atom. A surprising finding in the structure is the presence of two formate anions on opposite sides of the iron-binding pocket. The formate ions tether the N- and C-terminal domains of the protein and stabilize the closed structure, also providing clues as to probable candidates for synergistic anions in the iron-loaded state. PhFbpA represents a new class of bacterial iron-binding proteins

Strategies for the inhibition of gingipains for the potential treatment of periodontitis and associated systemic diseases

Gingipains are the major virulence factors of Porphyromonas gingivalis, the main periodontopathogen. It is expected that inhibition of gingipain activity in vivo could prevent or slow down the progression of adult periodontitis. To date, several classes of gingipain inhibitors have been recognized. These include gingipain N-terminal prodomains, synthetic compounds, inhibitors from natural sources, antibiotics, antiseptics, antibodies, and bacteria. Several synthetic compounds are potent gingipain inhibitors but inhibit a broad spectrum of host proteases and have undesirable side effects. Synthetic compounds with high specificity for gingipains have unknown toxicity effects, making natural inhibitors more promising as therapeutic gingipain blockers. Cranberry and rice extracts interfere with gingipain activity and prevent the growth and biofilm formation of periodontopathogens. Although the ideal gingipain inhibitor has yet to be discovered, gingipain inhibition represents a novel approach to treat and prevent periodontitis. Gingipain inhibitors may also help treat systemic disorders that are associated with periodontitis, including cardiovascular disease, rheumatoid arthritis, aspiration pneumonia, pre-term birth, and low birth weight

Medical microbiology in dentistry

МИКРОБИОЛОГИЯСТОМАТОЛОГИЯСТОМАТОГНАТИЧЕСКИЕ БОЛЕЗНИУЧЕБНЫЕ ПОСОБИЯВключены разделы с информацией о наиболее распространенных стоматологических болезнях, ассоциированных с инфекциями, их патогенезе, лабораторной диагностике, профилактике и лечении

Functional characterization of Aggregatibacter actinomycetemcomitans QSEBC : a bacterial adrengeric receptor and global regulator of virulence.

In order for a pathogen to successfully colonize the host, it must be able to acquire essential nutrients and regulate gene expression to respond to environmental fluctuations. One mechanism bacteria have evolved in order to detect these fluctuations and respond is the two component signal transduction systems (TCS). Aggregatibacter actinomycetemcomitans, a dental commensal associated with localized aggressive periodontitis, contains a TCS designated QseBC that was previously shown to regulate expression of several iron acquisition genes, biofilm formation and virulence, but the activating signal was unknown []. QseBC is a conserved TCS in the Enterobacteriaceae and Pasteurellaceae, but the activating signal for QseC varies for each species [125]. The QseC in Escherichia coli responds to catecholamines whereas the QseC homolog (FirS) in Haemophilus influenzae responds to ferrous iron. Here we show that the activating signal for the A. actinomycetemcomitans QseC is a combination of iron and catecholamines (CAT-Fe). The sensing of the CAT-Fe complex leads to a significant stimulation of biofilm and planktonic growth, as well as induction of genes involved in anaerobic metabolism, electron transport and oxidative stress while down-regulating expression of genes involved in iron acquisition and fatty acid and LPS biosynthesis. Using a combination of RNA analysis and metabolomics, we identified an increased flux through the TCA cycle to pyruvate and then to anaerobic respiration and metabolism with exposure to CAT-Fe. Cells exposed to Cat-Fe also expressed higher levels of catalase and were more resistant than untreated cells to oxidative stress. Finally, QseB also appears to play a role in regulating the general stress response in A. actinomycetemcomitans since a ΔqseB mutant exhibits increased transcription of several stress response genes, including the Lon protease. Ectopic expression of lon resulted in an increase in transcription of ygiW-qseBC. Lon is involved in activating type II toxin/anti-toxin (TA) systems, one of which (D11S_2133-2134) was shown to be highly up-regulated during iron starvation. Further, it was found that ectopic expression of the putative anti-toxin D11S_2134 resulted in a significant increase in transcription of qseBC. Based on this data, it is likely that D11S_2133-2134 regulates expression of qseBC allowing QseBC and D11S_2133-2134 to tightly control iron acquisition and regulate adaptation to the host