Activity of cathelicidin peptides against Chlamydia spp

Koala cathelicidin PhciCath5 has antimicrobial activity, including against Chlamydia pecorum

Devastating fires in Australia over 2019-20 decimated native fauna and flora, including koalas. The resulting population bottleneck, combined with significant loss of habitat, increases the vulnerability of remaining koala populations to threats which include disease. Chlamydia is one disease which causes significant morbidity and mortality in koalas. The predominant pathogenic species, Chlamydia pecorum, causes severe ocular, urogenital and reproductive tract disease. In marsupials, including the koala, gene expansions of an antimicrobial peptide family known as cathelicidins have enabled protection of immunologically naïve pouch young during early development. We propose that koala cathelicidins are active against Chlamydia and other bacteria and fungi. Here we describe ten koala cathelicidins, five of which contained full length coding sequences that were widely expressed in tissues throughout the body. Focusing on these five, we investigate their antimicrobial activity against two koala C. pecorum isolates from distinct serovars; MarsBar and IPTaLE, as well as other bacteria and fungi. One cathelicidin, PhciCath5, inactivated C. pecorum IPTaLE and MarsBar elementary bodies and significantly reduced the number of inclusions compared to the control (p<0.0001). Despite evidence of cathelicidin expression within tissues known to be infected by Chlamydia, natural PhciCath5 concentrations may be inadequate in vivo to prevent or control C. pecorum infections in koalas. PhciCath5 also displayed antimicrobial activity against fungi and Gram negative and positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Electrostatic interactions likely drive PhciCath5 adherence to the pathogen cell membrane, followed by membrane permeabilisation leading to cell death. Activity against E. coli was reduced in the presence of 10% serum and 20% whole blood. Future modification of the PhciCath5 peptide to enhance activity, including in the presence of serum/blood, may provide a novel solution to Chlamydia infection in koalas and other species.

Chlamydia trachomatis Plasmid Gene Protein 3 Is Essential for the Establishment of Persistent Infection and Associated Immunopathology

Chlamydia trachomatis can cause persistent infection that drives damaging inflammatory responses resulting in infertility and blindness. Little is known about chlamydial genes that cause persistence or factors that drive damaging pathology. In this work, we show that the C. trachomatis plasmid protein gene 3 (Pgp3) is the essential virulence factor for establishing persistent female genital tract infection and provide supportive evidence that Pgp3 functions similarly in a nonhuman primate trachoma model. We further show that persistent Ppg3-dependent infection drives damaging immunopathology. These results are important advances in understanding the pathophysiology of chlamydial persistence.

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that causes blinding trachoma and sexually transmitted disease afflicting hundreds of millions of people globally. A fundamental but poorly understood pathophysiological characteristic of chlamydial infection is the propensity to cause persistent infection that drives damaging inflammatory disease. The chlamydial plasmid is a virulence factor, but its role in the pathogenesis of persistent infection capable of driving immunopathology is unknown. Here, we show by using mouse and nonhuman primate infection models that the secreted plasmid gene protein 3 (Pgp3) is essential for establishing persistent infection. Ppg3-dependent persistent genital tract infection resulted in a severe endometritis caused by an intense infiltration of endometrial submucosal macrophages. Pgp3 released from the cytosol of lysed infected oviduct epithelial cells, not organism outer membrane-associated Pgp3, inhibited the chlamydial killing activity of antimicrobial peptides. Genetic Pgp3 rescue experiments in cathelin-related antimicrobial peptide (CRAMP)-deficient mice showed Pgp3-targeted antimicrobial peptides to subvert innate immunity as a pathogenic strategy to establish persistent infection. These findings provide important advances in understanding the role of Pgp3 in the pathogenesis of persistent chlamydial infection and associated immunopathology.

Antimicrobial peptides of the vaginal innate immunity and their role in the fight against sexually transmitted diseases

Some antimicrobial peptides (AMPs) are produced in the vaginal innate immune system and play an important role in protecting this organ against pathogenic agents. Moreover, sexually transmitted diseases have become a major problem in human societies and are rapidly spreading. The emergence of antibiotic-resistant microbes (superbugs) can pose a major threat to human societies and cause rapid spread of these diseases. Finding new antimicrobial compounds to fight superbugs is therefore essential. It has been shown that AMPs have good potential to become new antibiotics. The most important AMPs in the vaginal innate immune system are defensins, secretory leucocyte protease inhibitors, calprotectin, lysozyme, lactoferrin and elafin, which play an important role in host defence against sexually transmitted infections, modulation of immune responses and anticancer activities. Some AMPs, such as LL-37, magainin 2 and nisin, show both spermicidal and antimicrobial effects in the vagina. In this summary, we will discuss vaginal AMPs and continue to address some of the challenges of using peptides to control pathogens that are effective in sexually transmitted diseases.

Chlamydia trachomatis and Chlamydia pneumoniae Interaction with the Host: Latest Advances and Future Prospective

Research in Chlamydia trachomatis and Chlamydia pneumoniae has gained new traction due to recent advances in molecular biology, namely the widespread use of the metagenomic analysis and the development of a stable genomic transformation system, resulting in a better understanding of Chlamydia pathogenesis. C. trachomatis, the leading cause of bacterial sexually transmitted diseases, is responsible of cervicitis and urethritis, and C. pneumoniae, a widespread respiratory pathogen, has long been associated with several chronic inflammatory diseases with great impact on public health. The present review summarizes the current evidence regarding the complex interplay between C. trachomatis and host defense factors in the genital micro-environment as well as the key findings in chronic inflammatory diseases associated to C. pneumoniae.

Discovery of Antimicrobial Peptides in Cervical-Vaginal Fluid from Healthy Nonpregnant Women via an Integrated Proteome and Peptidome Analysis

Cervical-vaginal fluid (CVF) covers the lower part of the female reproductive system and functions in the homeostasis and immunity of the surrounding tissues. In contrast to the CVF proteome of both nonpregnant and pregnant women, the CVF peptidome has not been reported to date. In the current study, we identified 1087 proteins in CVF, of which 801 proteins were not previously identified in CVF proteomes. The presence of the tissue-specific proteins oviductal glycoprotein 1 and tubulin polymerization-promoting protein family member 3 strongly suggests that the tissues of the upper female reproductive tract contribute to the protein composition of CVF. The tremendous catalytic potential of CVF was highlighted by the identification of 85 proteases and the detection of pH-dependent trypsin-like proteolytic activity. Over 1000 endogenous peptides were detected in the CVF peptidome, and 39 peptides are predicted to have antimicrobial activity. The detailed proteomic and peptidomic analysis of CVF will further aid in the delineation of pathways related to reproduction, immunity and host defense, and assist in developing new biomarkers for malignant and other diseases of the female reproductive tract. Data are available via ProteomeXchange with identifiers PXD004450 (CVF peptidome) and PDX004363 (CVF proteome).

Activity of synthetic peptides against Chlamydia

The in vitro activity of six synthetic peptides against 36 strains of Chlamydia from different origins was investigated. Clavanin MO (CMO) proved to be the most active peptide, reducing the inclusion number of all Chlamydia strains from eight different species tested by ≥50% at 10 µg mL^-1 . Mastoparan L showed an equal activity against C. trachomatis, C. pneumoniae, C. suis, and C. muridarum, but did not exert any inhibitory effect against C. psittaci, C. pecorum, C. abortus, and C. avium even at 80 µg mL^-1 . These data suggest that CMO could be a promising compound in the prevention and treatment of chlamydial infections.

In vitro activity of a partially purified and characterized bark extract of Castanea sativa Mill. (ENC®) against Chlamydia spp

Castanea sativa Mill (ENC®), containing tannins against 33 Chlamydia strains, was compared to SMAP-29 with inhibitory effect against C. trachomatis and C. pneumoniae. The ENC® activity against Chlamydia spp. was evaluated determining the lowest concentration to achieve more than half reduction of intact chlamydial inclusions versus controls. ENC® reduced all Chlamydia strains tested at 1 µg/mL, while SMAP-29 induced reductions of C. trachomatis and C. pneumoniae infectivity at 10 µg/mL. A great reduction of C. trachomatis, C. pneumoniae, and C. abortus infectivity was achieved with a 10 µg/mL ENC® concentration, whereas their infectivity was almost inhibited at 100 µg/mL ENC® concentration.

Lead Discovery Strategies for Identification of Chlamydia pneumoniae Inhibitors

Throughout its known history, the gram-negative bacterium Chlamydia pneumoniae has remained a challenging target for antibacterial chemotherapy and drug discovery. Owing to its well-known propensity for persistence and recent reports on antimicrobial resistence within closely related species, new approaches for targeting this ubiquitous human pathogen are urgently needed. In this review, we describe the strategies that have been successfully applied for the identification of nonconventional antichlamydial agents, including target-based and ligand-based virtual screening, ethnopharmacological approach and pharmacophore-based design of antimicrobial peptide-mimicking compounds. Among the antichlamydial agents identified via these strategies, most translational work has been carried out with plant phenolics. Thus, currently available data on their properties as antichlamydial agents are described, highlighting their potential mechanisms of action. In this context, the role of mitogen-activated protein kinase activation in the intracellular growth and survival of C. pneumoniae is discussed. Owing to the complex and often complementary pathways applied by C. pneumoniae in the different stages of its life cycle, multitargeted therapy approaches are expected to provide better tools for antichlamydial therapy than agents with a single molecular target.

Natural Products for the Treatment of Chlamydiaceae Infections

Due to the global prevalence of Chlamydiae, exploring studies of diverse antichlamydial compounds is important in the development of effective treatment strategies and global infectious disease management. Chlamydiaceae is the most widely known bacterial family of the Chlamydiae order. Among the species in the family Chlamydiaceae, Chlamydia trachomatis and Chlamydia pneumoniae cause common human diseases, while Chlamydia abortus, Chlamydia psittaci, and Chlamydia suis represent zoonotic threats or are endemic in human food sources. Although chlamydial infections are currently manageable in human populations, chlamydial infections in livestock are endemic and there is significant difficulty achieving effective treatment. To combat the spread of Chlamydiaceae in humans and other hosts, improved methods for treatment and prevention of infection are needed. There exist various studies exploring the potential of natural products for developing new antichlamydial treatment modalities. Polyphenolic compounds can inhibit chlamydial growth by membrane disruption, reestablishment of host cell apoptosis, or improving host immune system detection. Fatty acids, monoglycerides, and lipids can disrupt the cell membranes of infective chlamydial elementary bodies (EBs). Peptides can disrupt the cell membranes of chlamydial EBs, and transferrins can inhibit chlamydial EBs from attachment to and permeation through the membranes of host cells. Cellular metabolites and probiotic bacteria can inhibit chlamydial infection by modulating host immune responses and directly inhibiting chlamydial growth. Finally, early stage clinical trials indicate that polyherbal formulations can be effective in treating chlamydial infections. Herein, we review an important body of literature in the field of antichlamydial research.

Recombinant Human Peptidoglycan Recognition Proteins Reveal Antichlamydial Activity

Peptidoglycan recognition proteins (PGLYRPs) are innate immune components that recognize the peptidoglycan and lipopolysaccharides of bacteria and exhibit antibacterial activity. Recently, the obligate intracellular parasite Chlamydia trachomatis was shown to have peptidoglycan. However, the antichlamydial activity of PGLYRPs has not yet been demonstrated. The aim of our study was to test whether PGLYRPs exhibit antibacterial activity against C. trachomatis Thus, we cloned the regions containing the human Pglyrp1, Pglyrp2, Pglyrp3, and Pglyrp4 genes for subsequent expression in human cell lines. We obtained stable HeLa cell lines that secrete recombinant human PGLYRPs into culture medium. We also generated purified recombinant PGLYRP1, -2, and -4 and confirmed their activities against Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria. Furthermore, we examined the activities of recombinant PGLYRPs against C. trachomatis and determined their MICs. We also observed a decrease in the infectious ability of chlamydial elementary bodies in the next generation after a single exposure to PGLYRPs. Finally, we demonstrated that PGLYRPs attach to C. trachomatis elementary bodies and activate the expression of the chlamydial two-component stress response system. Thus, PGLYRPs inhibit the development of chlamydial infection.

Amphipathic β2,2-Amino Acid Derivatives Suppress Infectivity and Disrupt the Intracellular Replication Cycle of Chlamydia pneumoniae

We demonstrate in the current work that small cationic antimicrobial β2,2-amino acid derivatives (Mw < 500 Da) are highly potent against Chlamydia pneumoniae at clinical relevant concentrations (< 5 μM, i.e. < 3.4 μg/mL). C. pneumoniae is an atypical respiratory pathogen associated with frequent treatment failures and persistent infections. This gram-negative bacterium has a biphasic life cycle as infectious elementary bodies and proliferating reticulate bodies, and efficient treatment is challenging because of its long and obligate intracellular replication cycle within specialized inclusion vacuoles. Chlamydicidal effect of the β2,2-amino acid derivatives in infected human epithelial cells was confirmed by transmission electron microscopy. Images of infected host cells treated with our lead derivative A2 revealed affected chlamydial inclusion vacuoles 24 hours post infection. Only remnants of elementary and reticulate bodies were detected at later time points. Neither the EM studies nor resazurin-based cell viability assays showed toxic effects on uninfected host cells or cell organelles after A2 treatment. Besides the effects on early intracellular inclusion vacuoles, the ability of these β2,2-amino acid derivatives to suppress Chlamydia pneumoniae infectivity upon treatment of elementary bodies suggested also a direct interaction with bacterial membranes. Synthetic β2,2-amino acid derivatives that target C. pneumoniae represent promising lead molecules for development of antimicrobial agents against this hard-to-treat intracellular pathogen.

Specific polymorphisms in the vitamin D metabolism pathway are not associated with susceptibility to Chlamydia trachomatis infection in humans

Chlamydia trachomatis is the most common sexually transmitted bacterium worldwide. Its often asymptomatic course of infection increases chances of transmission, and increases risk of late complications. Genetic variations in the host immune system are known to impact the course of infections. Recent studies have shown a positive impact of vitamin D on the regulation of the immune system. This study assesses the impact of eight polymorphisms in five genes [VDR (rs1544410 G > A, rs2228570 C > T), CYP27B1 (rs10877012 G > T), DHCR7 (rs7944926 G > A, rs3829251 G > A), GC (rs3755967) and CYP2R1 (rs10741657 G > A, rs2060793 G > A)] on susceptibility to Chlamydia infections in humans. These polymorphisms could influence protein expression or function, and thus influence the immune system. Samples of women visiting the STD outpatient clinic in South Limburg were genotyped using the Roche Lightcycler 480. In this study, we did not observe statistically significant differences between the genotype distributions of these polymorphisms in women with or without a Chlamydia infection. This suggests that VDR, CYP27B1, DHCR7, GC and CYP2R1 do not affect the susceptibility to Chlamydia infections. However, due to its pleiotropic nature in the immune system a role for the vitamin D pathway may not be excluded from the whole clinical course of Chlamydia infections (e.g. late complications), and further research is required.

The Potential Use of Natural and Structural Analogues of Antimicrobial Peptides in the Fight against Neglected Tropical Diseases

Recently, research into the development of new antimicrobial agents has been driven by the increase in resistance to traditional antibiotics and Emerging Infectious Diseases. Antimicrobial peptides (AMPs) are promising candidates as alternatives to current antibiotics in the treatment and prevention of microbial infections. AMPs are produced by all known living species, displaying direct antimicrobial killing activity and playing an important role in innate immunity. To date, more than 2000 AMPs have been discovered and many of these exhibit broad-spectrum antibacterial, antiviral and anti-parasitic activity. Neglected tropical diseases (NTDs) are caused by a variety of pathogens and are particularly wide-spread in low-income and developing regions of the world. Alternative, cost effective treatments are desperately needed to effectively battle these medically diverse diseases. AMPs have been shown to be effective against a variety of NTDs, including African trypanosomes, leishmaniosis and Chagas disease, trachoma and leprosy. In this review, the potential of selected AMPs to successfully treat a variety of NTD infections will be critically evaluated.

Antimicrobial host defence peptide, LL-37, as a potential vaginal contraceptive

STUDY QUESTION

Does antimicrobial peptide, LL-37, inhibit sperm fertilizing ability?

SUMMARY ANSWER

Our results indicate that LL-37 inhibits mouse and human sperm fertilizing ability.

WHAT IS KNOWN ALREADY

LL-37, a cationic antimicrobial peptide, exerts its microbicidal effects through the disruption of microbial cytoplasmic membranes following its interaction with microbial surface anionic phospholipids. ALL-38 (an LL-37 close analogue: LL-37 + Ala at the N-terminus) is produced in the vagina 2-6 h post-intercourse from its precursor hCAP-18, a seminal plasma component. At this time, motile sperm have already swum into the uterine cavity, thus unexposed to ALL-38. Since sperm contain a substantial amount of acidic sulfogalactosylglycerolipid (SGG) on their surface, treatment of sperm with LL-37 may cause their membrane disruption in an analogous manner to that occurring on microbial membranes.

STUDY DESIGN, SIZE AND DURATION

Mouse/human sperm treated (2-30 min) with LL-37 in a physiological concentration range (up to 10.8 µM) were assessed for SGG-dependent LL-37 binding, and parameters relevant to fertilizing ability, namely motility and intactness of the sperm acrosome and plasma membrane. Ability of mouse sperm to fertilize eggs in vitro was also evaluated. Each study was performed with greater than or equal to three different sperm samples. The efficacy of LL-37 to inhibit sperm fertilizing ability in vivo was determined in female mice (n = 26 each for LL-37 treatment and no treatment), using sperm retrieved from 26 males.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human sperm samples were donated by fertile men. LL-37 was chemically synthesized and was biotinylated for sperm binding studies. Sperm motility was assessed by videomicroscopy and the acrosomal status by Coomassie blue staining of acrosome-intact mouse sperm or the exposure of CD46, an inner acrosomal membrane protein, of acrosome reacted human sperm. Sperm membrane permeabilization/disruption was assessed by the loss of hypo-osmotic swelling response, an incorporation of Sytox Green (a membrane impermeable fluorescent DNA dye), and electron microscopy. Mouse IVF was scored by the presence of two pronuclei in eggs 6 h post-insemination. Ability of mouse sperm to fertilize eggs in vivo was determined by the pregnancy outcome of female mice injected transcervically with sperm with or without LL-37.

MAIN RESULTS AND THE ROLE OF CHANCE

Biotinylated LL-37 bound to both mouse and human sperm and the binding was partially dependent on sperm surface SGG. Mouse and human sperm became immotile and underwent a premature acrosome reaction upon treatment with LL-37 at 3.6 and 10.8 µM, respectively. The initial action of LL-37 on both mouse and human sperm appeared to be through permeabilization/disruption of sperm surface membranes evidenced by the loss of hypo-osmotic swelling response, Sytox Green staining and electron microscopy revealing ultrastructural damage. Mouse sperm treated with 3.6 µM LL-37 lost the ability to fertilize eggs both in vitro and in vivo. All 26 female mice inseminated with sperm and LL-37 did not become pregnant. No apparent damage to the reproductive tract was observed as revealed by histological characterization in LL-37-inseminated mice and these females resumed fecundity following mating with fertile males.

LIMITATIONS, REASONS FOR CAUTION

Direct demonstration that LL-37 treated human sperm fail to fertilize eggs was limited by legal restrictions on obtaining human eggs for such use.

WIDER IMPLICATIONS OF THE FINDINGS

Our results reveal selective inhibitory effects of LL-37 on sperm fertilizing ability in mice without apparent impairment to the female reproductive tract. LL-37 is therefore a promising candidate to be developed into a vaginal contraceptive with microbicidal activity.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Grand Challenges Explorations grant from the Bill & Melinda Gates Foundation (OPP1024509), Canadian Institutes of Health Research (MOP119438 & CCI82413) and International Collaboration and Exchanges NSFC of China (No.30611120525). There are no competing interests to declare.

Host defense peptides: general overview and an update on their activity against Chlamydia spp

Chlamydiae are obligate intracellular bacteria that cause serious diseases in a wide range of hosts. Chlamydia trachomatis is one of the leading sexually transmitted pathogens in the world. Because vaccines are not currently available, effective drugs are essential. In both animals and humans, chlamydial infections are often treated with tetracycline or its derivatives. A stable tetracycline-resistant phenotype was described in Chlamydia suis strains from pigs in the USA and in Europe. In humans, there are reports of tetracycline treatment failure and the in vitro adaptability of C. trachomatis to evolve to antibiotic resistance has been described, suggesting the pressing need to search for alternative and effective classes of antimicrobial drugs. Host defense peptides (HDPs) are known as direct antimicrobial agents as well as innate immune modulators. Being active against multidrug-resistant bacteria, HDPs are attractive candidates as templates for new drugs. A number of studies evaluated the activity of natural and synthetic HDPs against Chlamydia spp., showing C. trachomatis to be the most sensitive among chlamydia species tested. Protegrins and α-helical peptides were the most active among the HDPs assessed.

Activity of Cathelicidin Peptides against Simkania negevensis

The in vitro activity of six cathelicidin peptides against the reference strain Z of Simkania negevensis was investigated. Five peptides-PG-1, Bac7, SMAP-29, BMAP-27, and BMAP-28-proved to be active at very low concentrations (1 to 0.1 μg/mL), while LL-37 cathelicidin was ineffective even at a concentration of 100 μg/mL. In comparison to chlamydiae, S. negevensis proved to be more susceptible to the antimicrobial peptides tested.

Targeting bacterial membrane function: an underexploited mechanism for treating persistent infections

Persistent infections involving slow-growing or non-growing bacteria are hard to treat with antibiotics that target biosynthetic processes in growing cells. Consequently, there is a need for antimicrobials that can treat infections containing dormant bacteria. In this Review, we discuss the emerging concept that disrupting the bacterial membrane bilayer or proteins that are integral to membrane function (including membrane potential and energy metabolism) in dormant bacteria is a strategy for treating persistent infections. The clinical applicability of these approaches is exemplified by the efficacy of lipoglycopeptides that damage bacterial membranes and of the diarylquinoline TMC207, which inhibits membrane-bound ATP synthase. Despite some drawbacks, membrane-active agents form an important new means of eradicating recalcitrant, non-growing bacteria.

Porcine host defense peptides: expanding repertoire and functions

Host defense peptides (HDPs) are a large group of innate immune effectors that are also termed antimicrobial peptides. Because of the rapid progress that has been made in completing several animal genomes, many HDPs have been systemically defined using bioinformatic analysis and partially characterized using reverse genomic approaches. In pigs, about 30 HDPs have been identified and partially characterized relative to structure and function. Antimicrobial activity of porcine HDPs has been extensively evaluated against a broad spectrum of microorganisms in vitro and evaluated for their protective role in vivo. Increasing evidence indicates that HDPs are functionally differentiated during posttranslational and postsecretory processing, and that the structural units for antimicrobial and immunoregulatory functions are separate. These findings suggest promising new avenues for therapeutic drug design based on HDPs, including porcine HDPs. This review summarizes and discusses advances in porcine HDPs research during the last decade with an emphasis on the rapidly expanding profiles and biological functions.

The cell-penetrating peptide, Pep-1, has activity against intracellular chlamydial growth but not extracellular forms of Chlamydia trachomatis

OBJECTIVES

In the course of studies to identify novel treatment strategies against the pathogenic bacterium, Chlamydia, we tested the carrier peptide, Pep-1, for activity against an intracellular infection.

METHODS

Using a cell culture model of Chlamydia trachomatis infection, the effect of Pep-1 was measured by incubating the peptide with extracellular chlamydiae prior to infection, or by adding Pep-1 to the medium at varying times after infection, and assaying for inhibition of inclusion formation.

RESULTS

Pep-1 had a concentration-dependent effect on chlamydial growth with 100% inhibition of inclusion formation at 8 mg/L peptide. There was a window of susceptibility during the chlamydial developmental cycle with a maximal effect when treatment was begun within 12 h of infection. Pep-1 treatment caused a severe reduction in the production of infectious progeny even when started later, when the effect on inclusion formation was minimal. Furthermore, electron micrographs showed a paucity of progeny elementary bodies (EBs) in the inclusion. In contrast, pre-incubation of EBs with Pep-1 prior to infection did not affect inclusion formation. Taken together, these findings indicate that the antichlamydial effect was specific for the intracellular stage of chlamydial infection. By comparison, Pep-1 had no antimicrobial activity against Escherichia coli and Staphylococcus aureus or the obligate intracellular parasite, Toxoplasma gondii.

CONCLUSIONS

Pep-1 has antichlamydial activity by preventing intracellular chlamydial growth and replication but has no effect on extracellular chlamydiae.

Chlamydia trachomatis and Chlamydophila abortus induce the expression of secretory leukocyte protease inhibitor in cells of the human female reproductive tract

C. trachomatis and C. abortus are related Gram-negative intracellular bacteria that cause reproductive failure due to infertility (C. trachomatis) or abortion (C. abortus). These organisms target epithelial cells in the reproductive tract and/or placenta, but the innate immune mechanisms that lead to protection or pathology and disease are poorly understood. SLPI is an innate immune molecule which protects mucosal surfaces from infection and injury. C. trachomatis and C. abortus were found to induce SLPI mRNA and peptide expression in HeLa (cervical epithelium) and JEG-3 cells (trophoblast) respectively. Both cell lines constitutively expressed SLPI and, although infection enhanced this expression, killed organisms did not. These data demonstrate that Chlamydia/Chlamydophila grow in cells that express SLPI, suggesting that SLPI does not exert antimicrobial effects against these organisms. However, SLPI has multiple functions, and we speculate that it may play a role in controlling tissue inflammation and pathology.

Involvement of the antimicrobial peptide LL-37 in human atherosclerosis

OBJECTIVE

Antimicrobial peptides are effector molecules of the innate immune system. To understand the function of vascular innate immunity in atherosclerosis, we investigated the role of LL-37, a cathelicidin antimicrobial peptide, in the disease process.

METHODS AND RESULTS

Using real-time polymerase chain reaction, we found a 6-fold increase in human cationic antimicrobial protein 18/LL-37 transcript in human atherosclerotic lesions compared with normal arteries. Immunohistochemical analysis of atherosclerotic plaques showed that LL-37 was expressed mainly by macrophages and some endothelial cells. Western blot demonstrated existence of active LL-37 peptide and abundant proprotein in atheroma specimens. To understand the functional implication of LL-37 production in atherosclerosis, the transcription profile was assessed in endothelial cells treated with LL-37. Our data show that LL-37 induces expression of the adhesion molecule intercellular adhesion molecule-1 and the chemokine monocyte chemoattractant protein 1 in endothelial cells. Intriguingly, Chlamydia pneumoniae withstood the antimicrobial activity of LL-37 in vitro, although inflammatory response was induced on infection.

CONCLUSIONS

LL-37 is produced in atherosclerotic lesions, where it may function as an immune modulator by activating adhesion molecule and chemokine expression, thus enhancing innate immunity in atherosclerosis.