Clinical development of cationic antimicrobial peptides: from natural to novel antibiotics.

Over the past decade, levels of bacterial resistance to antibiotics have risen dramatically and "superbugs" resistant to most or all available agents have appeared in the clinic. Thus there is a growing need to discover and introduce new drugs. One potential source of novel antibiotics is the cationic antimicrobial peptides, which have been isolated from most living entities as components of their non-specific defenses against infectious organisms. Based on these natural templates, scores of structurally diverse antimicrobial cationic peptides have been designed, manufactured both chemically and biologically, and tested for activity against specific pathogens. A few of these peptide antibiotics have entered clinical trials to date, with mixed success. However, their diverse portfolio of structures, activity spectra, biological activities, and modes of action, provide substantial potential.

Structure and mechanism of action of an indolicidin peptide derivative with improved activity against gram-positive bacteria.

Indolicidin, an antimicrobial peptide with a unique amino acid sequence (ILPWKWPWWPWRR-NH(2)) is found in bovine neutrophils. A derivative of indolicidin, CP10A, has alanine residues substituted for proline residues and has improved activity against Gram-positive organisms. Transmission electron microscopy of Staphylococcus aureus and Staphylococcus epidermidis treated with CP10A showed mesosome-like structures in the cytoplasm. The peptide at 2-fold the minimal inhibitory concentration did not show significant killing of S. aureus ISP67 (a histidine, uridine, and thymidine auxotroph) but did show an early effect on histidine and uridine incorporation and, later, an effect on thymidine incorporation. Upon interaction with liposomes, detergents, and lipoteichoic acid, CP10A was shown by circular dichroism spectroscopy to undergo a change in secondary structure. Fluorescence spectroscopy indicated that the tryptophan residues were located at the hydrophobic/hydrophilic interface of liposomes and detergent micelles and were inaccessible to the aqueous quencher KI. The three-dimensional structure of CP10A in the lipid mimetic dodecylphosphocholine was determined using two-dimensional NMR methods and was characterized as a short, amphipathic helical structure, whereas indolicidin was previously shown to have an extended structure. These studies have introduced a cationic peptide with a unique structure and an ability to interact with membranes and to affect intracellular synthesis of proteins, RNA, and DNA.

Synergy of histone-derived peptides of coho salmon with lysozyme and flounder pleurocidin.

Recent research has identified endogenous cationic antimicrobial peptides as important factors in the innate immunity of many organisms, including fish. It is known that antimicrobial activity, as well as lysozyme activity, can be induced in coho salmon (Oncorhynchus kisutch) mucus after exposure of the fish to infectious agents. Since lysozyme alone does not have antimicrobial activity against Vibrio anguillarum and Aeromonas salmonicida, a four-step protein purification protocol was used to isolate and identify antibacterial fractions from bacterially challenged coho salmon mucus and blood. The purification consisted of extraction with hot acetic acid, extraction and concentration on a C(18) cartridge, gel filtration, and reverse-phase chromatography on a C(18) column. N-terminal amino acid sequence analyses revealed that both the blood and the mucus antimicrobial fractions demonstrated identity with the N terminus of trout H1 histone. Mass spectroscopic analysis indicated the presence of the entire histone, as well as fragments thereof, including a 26-amino-acid N-terminal segment. These fractions inhibited the growth of antibiotic-supersuscptible Salmonella enterica serovar Typhimurium, as well as A. salmonicida and V. anguillarum. Synthetic peptides identical to the N-terminally acetylated or C-terminally amidated 26-amino-acid fragment were inactive in antimicrobial assays, but they potentiated the antimicrobial activities of the flounder peptide pleurocidin, lysozyme, and crude lysozyme-containing extracts from coho salmon. The peptides bound specifically to anionic lipid monolayers. However, synergy with pleurocidin did not appear to occur at the cell membrane level. The synergistic activities of inducible histone peptides indicate that they play an important role in the first line of salmon defenses against infectious pathogens and that while some histone fragments may have direct antimicrobial effects, others improve existing defenses.

Antimicrobial peptides protect coho salmon from Vibrio anguillarum infections.

Fish losses from infectious diseases are a significant problem in aquaculture worldwide. Therefore, we investigated the ability of cationic antimicrobial peptides to protect against infection caused by the fish pathogen Vibrio anguillarum. To identify effective peptides for fish, the MICs of certain antimicrobial peptides against fish pathogens were determined in vitro. Two of the most effective antimicrobial peptides, CEME, a cecropin-melittin hybrid peptide, and pleurocidin amide, a C-terminally amidated form of the natural flounder peptide, were selected for in vivo studies. A single intraperitoneal injection of CEME did not affect mortality rates in juvenile coho salmon infected with V. anguillarum, the causative agent of vibriosis. Therefore, the peptides were delivered continuously using miniosmotic pumps placed in the peritoneal cavity. Twelve days after pump implantation, the fish received intraperitoneal injections of V. anguillarum at a dose that would kill 50 to 90% of the population. Fish receiving 200 microg of CEME per day survived longer and had significantly lower accumulated mortalities (13%) than the control groups (50 to 58%). Fish receiving pleurocidin amide at 250 microg per day also survived longer and had significantly lower accumulated mortalities (5%) than the control groups (67 to 75%). This clearly shows the potential for antimicrobial peptides to protect fish against infections and indicates that the strategy of overexpressing the peptides in transgenic fish may provide a method of decreasing bacterial disease problems.

A survey to identify potential outcome indicators for a hospital blood glucose monitoring program.

OBJECTIVE: A survey of operators of a bedside blood glucose monitoring (BGM) program at a tertiary health care institution was performed to identify potential outcome indicators for our quality assurance program. DESIGN AND METHODS: 170 surveys were randomly distributed to each nursing unit. The survey consisted of 20 questions on 4 pages. At the time of the survey, the BGM program consisted of 514 operators and 33 blood glucose meters on 17 inpatient nursing units servicing a total of 445 hospital beds. RESULTS: Seventy-eight percent of surveys were returned. Seventy-one percent of operators used the glucose meter at least once a week, 17% used it less than once a week, and 12% used it less than once a month. When asked how often they thought operators should perform BGM to ensure reliability, 65% stated "at least monthly," 8% said "bimonthly," and 27% said "3 to 4 times a year." In the previous 3 months, 59% of operators recalled "never having to repeat a BGM measurement with the glucose meter." 56% recalled "never having to confirm a BGM result by sending a venous sample to the central laboratory," 38% recalled "sending a venous sample once or twice;" 4% recalled "three or four times;" and 2% recalled "more than four times." Fifty-two percent recalled having to perform a stat analysis "less than once per month," 37% recalled "once or twice per month," and 11% recalled "once or twice per week." CONCLUSIONS: Through this survey we obtained information from our operators about the current functioning of our BGM program. Based on this information, we were able to develop a list of potential outcome indicators that we encourage health care institutions with BGM programs to consider incorporating in their quality assurance (QA) program.

The role of integrins and extracellular matrix in anchorage-independent growth of a mammary carcinoma cell line.

Anchorage-independent growth is a property of malignant cells. Extracellular matrix proteins are present in tumor spheroids but their function is not clearly defined. In this paper we show that a murine mammary carcinoma cell line, SP1, which expresses the fibronectin receptor alpha 5 beta 1 requires fibronectin for anchorage-independent growth in soft agar. Growth factors (hepatocyte growth factor and transforming growth factor-beta) also promote SP1 colony growth. In contrast, collagen types I and IV have an inhibitory effect on SP1 colony growth. A clone isolated from SP1 cells which expresses the collagen/laminin receptor alpha 2 beta 1 as well as the fibronectin receptor alpha 5 beta 1, demonstrates increased colony formation in the presence of fibronectin and collagen. These data suggest a role for both the alpha 5 beta 1 and alpha 2 beta 1 integrin receptors in the regulation of anchorage-independent growth of mammary carcinoma cells.