Peptides (v.24, #11)

Introduction by Amram Mor (1645).

Evolution of primate θ-defensins: a serpentine path to a sweet tooth by Tung X Nguyen; Alex M Cole; Robert I Lehrer (1647-1654).
Retrocyclins (ancestral human θ-defensins) are cyclic antimicrobial octadecapeptides that interfere with viral uptake and protect human cells from infection by T- and M-tropic strains of HIV-1 in vitro. As are other θ-defensins, retrocyclins are lectins that bind gp120, CD4, and galactosylceramide—all of which are implicated in HIV-1 uptake. Although θ-defensin mRNA transcripts are present in human bone marrow, spleen, thymus, testis, and skeletal muscle, a premature stop codon aborts their translation. We found six θ-defensin (DEFT) genes in the human genome; five on chromosome 8p23 and one on chromosome 1. All six of these pseudogenes, as well as their homologues in chimpanzees and gorillas, contained the same premature stop codon mutation. Whereas we found intact DEFT genes in DNA from several Old World Monkeys, Hylobates syndactylus (a lesser ape) and orangutans, no homologues were present in DNA from six New World Monkeys and five prosimians. We conclude that DEFT genes and θ-defensins arose in Old World Monkeys by mutation of a pre-existing α-defensin gene. Although intact DEFT genes survive in some nonhuman primates, our hominid ancestors lost their ability to produce θ-defensins after the orangutan and hominid lineages diverged. It is possible (but may be difficult to prove) that this mutation rendered our species more susceptible to infection by HIV-1.
Keywords: Antimicrobial; Cyclic; Defensins; HIV-1; Lectin; Peptide;

Hagfish intestinal antimicrobial peptides are ancient cathelicidins by Thomas Uzzell; Ethan D Stolzenberg; Ann E Shinnar; Michael Zasloff (1655-1667).
Three potent broad-spectrum antimicrobial peptides (HFIAP-1, -2, and -3) isolated from intestinal tissues of Myxine glutinosa (Atlantic hagfish) are identified as ancient members of the cathelicidin family of antimicrobial peptides, hitherto known only from mammals. In situ hybridization reveals that HFIAPs are produced in nests of myeloid cells within the loose connective tissue of the gut wall, a tissue reminiscent of both gut-associated lymphoid tissue (GALT) and vertebrate spleen. We suggest that this tissue organization provides local defense of the hagfish gastrointestinal tract via innate immunity and possibly served as the architectural plan upon which the adaptive immune system evolved.
Keywords: Cathelicidin; Cystatin; Antimicrobial peptide; HFIAP; Hagfish; Myxine; Agnatha; GALT; Jaw hypothesis; Innate immunity; Indel;

Molecular strategies in biological evolution of antimicrobial peptides by Pierre Nicolas; Damien Vanhoye; Mohamed Amiche (1669-1680).
Gene-encoded antimicrobial peptides that protect the skin of hylid and ranin frogs against noxious microorganisms are processed from a unique family of precursor polypeptides with a unique pattern of conserved and variable regions opposite to that of conventional secreted peptides. Precursors belonging to this family, designated the preprodermaseptin, have a common N-terminal preproregion that is remarkably well conserved both within and between species, but a hypervariable C-terminal domain corresponding to antimicrobial peptides with very different lengths, sequences, charges and antimicrobial spectra. Each frog species has its own distinct panoply of 10–20 antimicrobial peptides so that the 5000 species of ranids and hylids may produce ∼100,000 different peptide antibiotics. The strategy that these frogs have evolved to generate this enormous array of peptides includes repeated duplications of a 150 million years old ancestral gene, focal hypermutation of the antimicrobial peptide domain maybe involving a mutagenic DNA polymerase similar to Escherichia coli Pol V, and subsequent actions of positive (diversifying) selection. The hyperdivergence of skin antimicrobial peptides can be viewed as the successful evolution of a multi-drug defense system that provides frogs with maximum protection against rapidly changing microbial biota and minimizes the chance of microorganisms developing resistance to individual peptides. The impressive variations in the expression of frog skin antimicrobial peptides may be exploited for discovering new molecules and structural motifs targeting specific microorganisms for which the therapeutic armamentarium is scarce.
Keywords: Antimicrobial peptides; Frog skin; Dermaseptins; Polypeptide precursor; Hypermutation; Pol V; Gene family; Signal peptide;

The relationship between peptide structure and antibacterial activity by Jon-Paul S Powers; Robert E.W Hancock (1681-1691).
Cationic antimicrobial peptides are a class of small, positively charged peptides known for their broad-spectrum antimicrobial activity. These peptides have also been shown to possess anti-viral and anti-cancer activity and, most recently, the ability to modulate the innate immune response. To date, a large number of antimicrobial peptides have been chemically characterized, however, few high-resolution structures are available. Structure–activity studies of these peptides reveal two main requirements for antimicrobial activity, (1) a cationic charge and (2) an induced amphipathic conformation. In addition to peptide conformation, the role of membrane lipid composition, specifically non-bilayer lipids, on peptide activity will also be discussed.
Keywords: Antimicrobial cationic peptide; Polyphemusin; Structure;

Cationic antibacterial peptides are produced in all living organisms and possess either selective activity toward a certain type of cell or microorganism, or a broad spectrum of activity toward several types of cells including prokaryotic and mammalian cells. In order to exert their activity, peptides first interact with and traverse an outer barrier, e.g., mainly LPS and peptidoglycan in bacteria or a glycocalix layer and matrix proteins in mammalian cells. Only then, can the peptides bind and insert into the cytoplasmic membrane. The mode of action of many antibacterial peptides is believed to be the disruption of the lipidic plasma membrane. Therefore, model phospholipid membranes have been used to study the mode of action of antimicrobial peptides. These studies have demonstrated that peptides that act preferentially on bacteria are also able to interact with and permeate efficiently anionic phospholipids, whereas peptides that lyse mammalian cells bind and permeate efficiently both acidic and zwitterionic phospholipids membranes, mimicking the plasma membranes of these cells. It is now becoming increasingly clear that selective activity of these peptides against different cells depends also on other parameters that characterize both the peptide and the target cell. With respect to the peptide’s properties, these include the volume of the molecule, its structure, and its oligomeric state in solution and in membranes. Regarding the target membrane, these include the structure, length, and complexity of the hydrophilic polysaccharide found in its outer layer. These parameters affect the ability of the peptides to diffuse through the cell’s outer barrier and to reach its cytoplasmic plasma membrane.
Keywords: Antimicrobial peptides; LPS; Peptidoglycan; Glycocalix layer; Model phospholipids membranes; Peptide–lipid interactions;

Interactions of antifungal plant defensins with fungal membrane components by Karin Thevissen; Kathelijne K.A. Ferket; Isabelle E.J.A. François; Bruno P.A. Cammue (1705-1712).
Plant defensins are small, basic, cysteine-rich peptides that are generally active against a broad spectrum of fungal and yeast species at micromolar concentrations. Some of these defensins interact with fungal-specific lipid components in the plasmamembrane. Structural differences of these membrane components between fungal and plant cells probably account for the selective activity of plant defensins against fungal pathogens and their nonphytotoxic properties. This review will focus on different classes of complex lipids in fungal membranes and on the selective interaction of plant defensins with these complex lipids.
Keywords: Plant defensin; Sphingolipid; Glucosylceramide; Neurospora crassa; Saccharomyces cerevisiae; Pichia pastoris; Candida albicans; Mode of action;

A peptidylprolyl cis/trans isomerase from Xenopus laevis skin: cloning, biochemical characterization and putative role in the secretion by Rossella Miele; Marina Borro; M.Luisa Mangoni; Maurizio Simmaco; Donatella Barra (1713-1721).
In amphibian skin secretions, a peptidylprolyl cis/trans isomerase activity was detected. A Xenopus laevis skin cDNA coding for this protein was cloned, sequenced and over-expressed in Escherichia coli. The primary structure of the protein shows extensive similarity with members of the cyclophilin A family. Catalytic parameters of the recombinant protein are similar to those of the human enzyme. The enzymatic activity is inhibited by cyclosporin A. Data suggesting that peptidylprolyl isomerization influences the biological activity of antibacterial peptides of amphibian origin are presented, and its putative role in the defence mechanism discussed.
Keywords: Peptidylprolyl cis/trans isomerase; Cyclophilin; Antimicrobial peptide; Amphibian skin; Innate immunity; Bombina orientalis; Xenopus laevis;

In vitro and in vivo antimicrobial activity of two α-helical cathelicidin peptides and of their synthetic analogs by Monica Benincasa; Barbara Skerlavaj; Renato Gennaro; Antonio Pellegrini; Margherita Zanetti (1723-1731).
Two α-helical antimicrobial peptides (BMAP-27 and -28) and four synthetic analogs were compared for in vitro and in vivo antimicrobial efficacy. All peptides proved active in vitro at micromolar concentrations against a range of clinical isolates, including antibiotic-resistant strains. BMAP-27 and two analogs were more effective towards Gram-negative, and BMAP-28 towards Gram-positive organisms. In addition, BMAP-28 provided some protection in vitro against human herpes simplex virus type 1 (HSV-1). The parent peptides and mBMAP-28 analog protected mice from lethal i.p. infections in an acute peritonitis model at peptide doses significantly lower than those toxic to the animals, suggesting a satisfactory therapeutic index.
Keywords: Cathelicidin peptide; α-Helical antimicrobial peptide; Synthetic analog; Antimicrobial activity; Clinical isolate; In vivo protection; Infection;

Two different propionicins produced by Propionibacterium thoenii P-127 by Galit Ben-Shushan; Varda Zakin; Natan Gollop (1733-1740).
The bacteriocin GBZ-1 was purified from the growth media of Propionibacterium thoenii P-127 and was found to have a molecular weight of 6000 Da. P. thoenii P-127 also known as the producer of the bacteriocin PLG-1 (MW 10 kDa). Under specific growth conditions, on semi-solid media, P. thoenii P-127 produced both PLG-1 and GBZ-1. The N-terminal of GBZ-1 was microsequenced, the gene was cloned and the DNA sequence was determined and identified. GBZ-1 is highly homologous to a protease-activated antimicrobial peptide (PAMP). In contrast to PAMP, it was purified in its active form and no protease digestion was required for its activation. The survival curve of indicator bacteria Lactobacillus delbrueckii subsp. lactic ATCC 4797 showed two phases. The fast phase of 20 min was followed by a slow phase. While bacterial survival was reduced by 2 logs during the fast phase, bacterial survival was reduced by additional 3 logs up to 200 min during the slow phase. GBZ-1 activity was affected by magnesium and its activity was completely abolished at 50 mM magnesium chloride. Other divalent cations had no effect on GBZ-1 activity of GBZ-1. To the best of our knowledge this is the first report of a bacterium producing two different bacteriocins under different growth conditions.
Keywords: Propionibacterium thoenii; PAMP; Bacteriocins;

Susceptibility of Treponema pallidum to host-derived antimicrobial peptides by David L Cox; Yongcheng Sun; Hsi Liu; Robert I Lehrer; William M Shafer (1741-1746).
LL-37 displays potent broad-spectrum activity against a number of pathogenic bacteria and is the only cathelicidin thus far identified in humans. In this study, we examined the capacity of human LL-37 and the similar CAP-18-derived peptide from rabbits to exert antimicrobial activity against the causative agent of syphilis, Treponema pallidum. We found that both peptides, as well as a truncated version of human LL-37 that contains its bactericidal domain, could exert rapid, but salt-sensitive antimicrobial activity against T. pallidum. Infectivity of T. pallidum in a rabbit model could effectively be blocked with the synthetic truncated LL-37-derived peptide WS22-N-amide.
Keywords: Antibacterial peptide; Outer membrane; WS22; Tissue culture; Spirochete;

Antiendotoxin activity of protegrin analog IB-367 alone or in combination with piperacillin in different animal models of septic shock by Andrea Giacometti; Oscar Cirioni; Roberto Ghiselli; Federico Mocchegiani; Claudio Viticchi; Fiorenza Orlando; Giuseppina D’Amato; Maria Simona Del Prete; Wojciech Kamysz; Jerzy Łukasiak; Vittorio Saba; Giorgio Scalise (1747-1752).
The therapeutic efficacy of protegrin peptide IB-367 was investigated in three rat models of septic shock: (i) rats injected intraperitoneally with 1 mg Escherichia coli 0111:B4 lipopolysaccharide, (ii) rats given an intraperitoneal injection of 2×1010  CFU of E. coli ATCC 25922, and (iii) rats in which intra-abdominal sepsis was induced via cecal ligation and puncture. All animals were randomized to receive parenterally isotonic sodium chloride solution, 1 mg/kg of IB-367, 60 mg/kg piperacillin and 1 mg/kg of IB-367 plus 60 mg/kg piperacillin. The peptide demonstrated lower level of antimicrobial activity than piperacillin, nevertheless it exhibited the dual properties of antimicrobial and antiendotoxin agent. Finally IB-367 and piperacillin association showed to be the most effective therapeutic approach.
Keywords: Protegrins; IB-367; Antimicrobial peptides; Endotoxin; Lipopolysaccharide; Septic shock;

Membrane binding and permeation by indolicidin analogs studied by a biomimetic lipid/polydiacetylene vesicle assay by Revital Halevy; Annett Rozek; Sofiya Kolusheva; Robert E.W. Hancock; Raz Jelinek (1753-1761).
Membrane binding and relative penetration of indolicidin analogs were studied using lipid/polydiacetylene (PDA) chromatic biomimetic membranes. Colorimetric and fluorescence analyses determined that an indolicidin analog with a proline and tryptophan residue substituted with lysines showed more pronounced bilayer surface interactions, while indolicidin and particularly an indolicidin analog in which all prolines were replaced with alanine residues exhibited deeper insertion into the lipid bilayer. The colorimetric data demonstrated that more pronounced blue-red transitions were observed when the chromatic vesicles incorporated lipopolysaccharide (LPS) within the lipid bilayer, indicating that LPS promoted preferred binding and incorporation of the peptides at the lipid/water interface. The fluorescence quenching experiments further confirmed this outcome. The results indicate that the antibacterial activity of indolicidin most likely requires initial binding to the LPS moieties within bacterial membranes, as well as disruption of the bilayer interface. The degree of hemolysis induced by the analogs, on the other hand, correlated to the extent of penetration into the hydrophobic core of the lipid assembly.
Keywords: Indolicidin; Antimicrobial peptides; Membranes; Colorimetric assays; Polydiacetylene; Fluorescence quenching; NBD; Dansyl–PMBN;

Antimicrobial polypeptides of the human colonic epithelium by Scott J. Howell; Dennis Wilk; Satya P. Yadav; Charles L. Bevins (1763-1770).
The lumen of the human colon is heavily colonized with microbes, but infections across its epithelial surface are infrequent. To address the hypothesis that antimicrobial polypeptides contribute to the barrier function of colonic epithelial cells, we examined cellular extracts from non-inflamed colonic mucosa using an antimicrobial assay. This approach yielded five polypeptides: three antimicrobials were previously identified as ribosomal polypeptides (L30, S19 and ubiquicidin), and two were members of the histone family (H1.5 and H2B). All exhibited bactericidal activity against Escherichia coli, and with the exception of S19, had been isolated by others based on their potent antimicrobial activity in other cells and tissues. These polypeptides normally reside inside cells and are proposed to contribute to the formation of the functional antimicrobial barrier of the colonic epithelium.
Keywords: Colon; Epithelia; Antimicrobial peptide; Ribosomal L30; Ribosomal S19; Ubiquicidin; Histone H1.5; Histone H2B;

Functional characterisation of the 1–18 fragment of esculentin-1b, an antimicrobial peptide from Rana esculenta by M.Luisa Mangoni; Daniela Fiocco; Giuseppina Mignogna; Donatella Barra; Maurizio Simmaco (1771-1777).
Esculentin-1 is a 46-amino acid residue peptide isolated from skin secretions of Rana esculenta, displaying the most potent antimicrobial activity among the bioactive molecules found in the secretion, with negligible effects on eukaryotic cell membranes. From skin secretions, the 19–46 fragment of esculentin-1, devoid of antibacterial activity, was also isolated. We studied in detail the activity of the N-terminal fragment (1–18) of esculentin-1 using a synthetic amidated analogue. The results show that this fragment is highly active against most bacterial and fungal species, although at a lower extent than the full-length peptide, being four-fold more potent against Phytophthora nicotianae. It has a reduced activity against human erythrocytes with respect to the full-length peptide. The killing curves in liquid medium are similar for the two molecules and the shorter peptide is able to increase the bacterial outer and inner membrane permeability. Overall these data indicate that the antimicrobial properties of esculentin-1 are exerted by its N-terminal 1–18 region and that the positively charged residue distribution as well as peptide length represent important determinants for cell selectivity.
Keywords: Esculentin; Antimicrobial peptide; Amphibian skin; Innate immunity; Rana esculenta;

The antibacterial peptide ceratotoxin A displays alamethicin-like behavior in lipid bilayers by Nathalie Saint; Laura Marri; Daniela Marchini; Gérard Molle (1779-1784).
Ceratotoxin A (CtxA), a 36-residue α-helical cationic peptide isolated from the medfly Ceratitis capitata, exhibits strong antibacterial activity. To determine its mode of action against bacteria, we investigated the behavior of ceratotoxin A by incorporating it into planar lipid bilayers. Macroscopic and single channel conductance experiments showed that ceratotoxin A forms voltage-dependent ion channels in bilayers according to the barrel-stave model. The characteristics of the channel suggest that the C-terminal regions form bundles of five or six helices embedded in the membrane, such that the N-terminal moieties lie on the polar side of the lipid bilayer.
Keywords: α-Helix; Amphipathy; Ion channel; Conductance; Barrel-stave; Pore-forming;

Detection of HBD1 peptide in peripheral blood mononuclear cell subpopulations by intracellular flow cytometry by Lisa K. Ryan; Gill Diamond; Sheela Amrute; Zhimin Feng; Aaron Weinberg; Patricia Fitzgerald-Bocarsly (1785-1794).
Production of human β-defensin1 (HBD1) in response to LPS in monocytes, myeloid dendritic cells and plasmacytoid dendritic cells (PDC) was examined. Since PDC make up only 0.1–0.5% of the peripheral blood mononuclear cell population, we developed a method to determine HBD1 peptide levels using four-color flow cytometry, which can examine several cell surface or intracellular markers at once. Coupled with intracellular flow cytometry, we determined that PDC and monocytes only made significant amounts of HBD1 when exposed to >50 ng/ml LPS for 2 h. This response was limited to monocytes when ultrapure LPS was used, and was inhibited in PDC by chloroquine treatment.
Keywords: β-Defensins; Lipopolysaccharide; Monocytes; Dendritic cells; Plasmacytoid dendritic cells; Flow cytometry; Chloroquine;

Quantitative interactions between cryptdin-4 amino terminal variants and membranes by Donald P Satchell; Tanya Sheynis; Sofiya Kolusheva; Jason Cummings; T.Kyle Vanderlick; Raz Jelinek; Michael E Selsted; Andre J Ouellette (1795-1805).
Paneth cells secrete α-defensins into the lumen from the base of small intestinal crypts, and cryptdin-4 (Crp4) is the most potent mouse α-defensin in vitro. Purified recombinant Crp4 and Crp4 variants with (des-Gly)-, (Gly1Val)-, (Gly1Asp)-, and (Gly1Arg)-substitutions were all bactericidal with Crp4 and (Gly1Arg)-Crp4 being slightly more active than other variants. Bactericidal activities correlated directly with permeabilization of live Escherichia coli, with equilibrium binding to E. coli membrane phospholipid bilayers and vesicles, and with induced graded fluorophore leakage from phospholipid vesicles. The Crp4 peptide N-terminus affects bactericidal activity modestly, apparently by influencing peptide binding to phospholipid bilayers and subsequent permeabilization of target cell membranes.
Keywords: Innate immunity; Paneth cells; Polymerase chain reaction; Recombinant peptide expression; α-Defensin; Reverse-phase high performance liquid chromatography; Matrix-assisted laser desorption time-of-flight mass spectrometry; Surface plasmon resonance; Lipid polydiacetylene vesicles; ANTS-DPX leakage; Antimicrobial peptide;

Peptide HP (2–20), A2KKVFKRLEKLFSKIQNDK20 , is a cationic antimicrobial peptide derived from the N-terminus of Helicobacter pylori ribosomal protein 1, HpRpL1. Native peptide HP (2–20) and its synthetic derivatives have been shown in vitro to exhibit potent killing activity against Gram-positive, Gram-negative and yeast cells, thus, making them promising candidates for treatment of polymicrobial infections. However, the therapeutic potential of peptide HP (2–20) or its synthetic derivatives in any animal model of either bacterial or fungal diseases has not yet been investigated. In this study, we demonstrate that synthetic peptide amide HP (2–20), administered in six doses (300 μg each; one intraperitoneal dose at the time of the infection, followed by five intravenous doses at 12 h intervals) to CBA/J male mice experimentally infected with a lethal inoculum (1×109  CFU) of Candida albicans, delayed the onset of disease, suppressed disease progression, and greatly increased survival rate and time (16.6% by day 14), as compared with the untreated infected control mice (100% mortality by day 5). Further, using isotonic buffer systems differing in ionic strength, peptide HP (2–20) was shown in vitro to exhibit an ionic strength-dependent hemolytic activity, previously not detected. Repeated intravenous administration of uninfected control CBA/J male mice with peptide HP (2–20), however, caused neither morbidity nor mortality. These findings strongly evidence the therapeutic efficacy and safety values of peptide HP (2–20) as a lead drug for the treatment of acquired candidiasis.
Keywords: Antibacterial peptide; Antifungal peptide; Antimicrobial peptide; Candidiasis;

Activity of dermaseptin K4-S4 against foodborne pathogens by Sima Yaron; Tali Rydlo; Dina Shachar; Amram Mor (1815-1821).
Dermaseptin S4 and its substituted derivative K4-S4 were investigated against various food-related pathogenic bacteria in culture media. K4-S4, but not the native peptide displayed significant growth inhibitory activity against all bacteria tested. Next, activity of K4-S4 against Escherichia coli O157:H7 was defined in terms of milieu dependencies. Salt-dependent kinetic studies in growth medium indicated that the peptide’s antibacterial activity is maintained at fairly high (up to 600 mM) NaCl concentrations but inhibited at higher concentrations. Similarly, antibacterial activity was reduced at high but not low pH conditions. Importantly, antibacterial activity was significantly maintained at temperatures lower than 37 °C and significantly enhanced at 42 °C. With respect to bactericidal kinetics, negative cultures were obtained in LB as well as in commercial apple juice, respectively, within 1 and 2 h treatment, at twice the minimal inhibitory concentration (MIC) value. Overall, the data collected is indicative of a certain interest for dermaseptin derivatives as potential food preservatives.
Keywords: Antimicrobial peptides; Foodborn pathogens; Food preservation;

Inhibition of Staphylococcus aureus pathogenesis in vitro and in vivo by RAP-binding peptides by Guang Yang; Huichai Cheng; Chuan Liu; Yanning Xue; Yaping Gao; Nongle Liu; Bo Gao; Dongping Wang; Shanru Li; Beifen Shen; Ningsheng Shao (1823-1828).
Staphylococcus aureus cause many diseases by producing toxins, whose synthesis is regulated by quorum-sensing mechanisms. S. aureus secretes a protein termed RNAIII activating protein (RAP) which autoinduces toxin production via the phosphorylation of is target protein TRAP. Mice vaccinated with RAP were protected from S. aureus infection, suggesting that RAP is an useful target for selecting potential therapeutic molecules to inhibit S. aureus pathogenesis. We show here that RAP (native and recombinant) was used to select RAP-binding peptides (RBPs) from a random 12-mer phage-displayed peptide library. Two RBPs were shown to inhibit RNAIII production in vitro (used a marker for pathogenesis). The peptide WPFAHWPWQYPR, which had the strongest inhibitory activity, was chemically synthesized and also expressed in Escherichia coli as a GST-fusion. Both synthetic peptide and GST-fusion peptide decreased RNAIII levels in a dose-dependent manner. The GST-fusion peptide was also shown to protect mice from a S. aureus infection in vivo (tested in a murine cutaneous S. aureus infection model). Our results suggest the potential use of RAP-binding proteins in treating clinical S. aureus infections.
Keywords: agr; RNAIII; Quorum-sensing; Cell–cell communication; Phage display; RAP; RIP;

Treatment efficacy of the lead RNAIII-inhibiting peptide YSPWTNF-NH2 in acquired Staphylococcus aureus sepsis: a histopathological assessment by Patrı́cia Damasceno Ribeiro; Osmar Damasceno Ribeiro; Ana Maria Marcolan; Enrique Medina-Acosta (1829-1836).
The quorum-sensing interfering RNAIII-inhibiting peptide (RIP) YSPXTNF and its synthetic analogues YSPWTNF and YSPITNF have been shown to prevent and suppress diseases caused by Staphylococcus aureus at different body sites in different animal models. This study was designed to investigate histopathologically the therapeutic efficacy of lead peptide RIP YSPWTNF-NH2 in the subcutaneous air sac murine model of acquired S. aureus sepsis. Two experimental protocols were evaluated: an infection/therapy protocol, for which twenty BALB/c mice per group were infected with a subcutaneous inoculum of S. aureus strain ATCC 25923 (2×109 colony forming units) that were either pretreated or not with 150 μg of peptide RIP, and a safety protocol, for which three uninfected mice per group received treatment with either 150 μg of peptide RIP or saline. Therapeutic efficacy was assessed by clinical examination for a period of 20 days and histopathology at 12, 24, 36, 48, 96 and 168 h after inoculation. Treatment safety was assessed histopathologically at 24, 48 and 264 h after inoculation. Subcutaneous administration of uninfected control mice with a single dose of peptide RIP YSPWTNF caused no significant histopathology in most organs examined, except for slight to moderate lung and liver congestions. In contrast to the situation with the untreated infected control group mice that presented with histopathological alterations consistent with the diagnosis of rapidly progressive and highly erosive disease (100% mortality by day 3), treatment of infected animals with peptide RIP YSPWTNF had a profound therapeutic effect on survival rate (67% by day 20) and on disease progression. The histopathological examination confirmed the clinical findings showing that extensive tissue damage at the site of the infection and in organs were greatly suppressed in the peptide RIP-treated animals.
Keywords: Quorum-sensing; RNAIII-inhibiting peptide; Therapeutic peptide; Staphylococcus-induced histopathology;