Activity Of Host Defense Peptides Research Articles

Effects of Escherichia coli LPS Structure on Antibacterial and Anti-Endotoxin Activities of Host Defense Peptides.

The binding of Host Defense Peptides (HDPs) to the endotoxin of Gram-negative bacteria has important unsolved aspects. For most HDPs, it is unclear if binding is part of the antibacterial mechanism or whether LPS actually provides a protective layer against HDP killing. In addition, HDP binding to LPS can block the subsequent TLR4-mediated activation of the immune system. This dual activity is important, considering that HDPs are thought of as an alternative to conventional antibiotics, which do not provide this dual activity. In this study, we systematically determine, for the first time, the influence of the O-antigen and Lipid A composition on both the antibacterial and anti-endotoxin activity of four HDPs (CATH-2, PR-39, PMAP-23, and PMAP36). The presence of the O-antigen did not affect the antibacterial activity of any of the tested HDPs. Similarly, modification of the lipid A phosphate (MCR-1 phenotype) also did not affect the activity of the HDPs. Furthermore, assessment of inner and outer membrane damage revealed that CATH-2 and PMAP-36 are profoundly membrane-active and disrupt the inner and outer membrane of Escherichia coli simultaneously, suggesting that crossing the outer membrane is the rate-limiting step in the bactericidal activity of these HDPs but is independent of the presence of an O-antigen. In contrast to killing, larger differences were observed for the anti-endotoxin properties of HDPs. CATH-2 and PMAP-36 were much stronger at suppressing LPS-induced activation of macrophages compared to PR-39 and PMAP-23. In addition, the presence of only one phosphate group in the lipid A moiety reduced the immunomodulating activity of these HDPs. Overall, the data strongly suggest that LPS composition has little effect on bacterial killing but that Lipid A modification can affect the immunomodulatory role of HDPs. This dual activity should be considered when HDPs are considered for application purposes in the treatment of infectious diseases.

Host defense peptides combined with MTA extract increase the repair in dental pulp cells: in vitro and ex vivo study

Host Defense Peptides (HDPs) have, in previous studies, been demonstrating antimicrobial, anti-inflammatory, and immunomodulatory capacity, important factors in the repair process. Knowing these characteristics, this article aims to evaluate the potential of HDPs IDR1018 and DJK-6 associated with MTA extract in the repair process of human pulp cells. Antibacterial activity of HDPs, MTA and HDPs combined with MTA in Streptococcus mutans planktonic bacteria and antibiofilm activity was evaluated. Cell toxicity was assayed with MTT and cell morphology was observed by scanning electron microscopy (SEM). Proliferation and migration of pulp cells were evaluated by trypan blue and wound healing assay. Inflammatory and mineralization related genes were evaluated by qPCR (IL-6, TNFRSF, DSPP, TGF-β). Alkaline phosphatase, phosphate quantification and alizarin red staining were also verified. The assays were performed in technical and biological triplicate (n = 9). Results were submitted for the calculation of the mean and standard deviation. Then, normality verification by Kolmogorov Smirnov test, analyzing one-way ANOVA. Analyses were considered at a 95% significance level, with a p-value < 0.05. Our study demonstrated that HDPs combined with MTA were able to reduce biofilms performed in 24 h and biofilm performed over 7 days S. mutans biofilm (p < 0.05). IDR1018 and MTA, as well as their combination, down-regulated IL-6 expression (p < 0.05). Tested materials were not cytotoxic to pulp cells. IDR1018 induced high cell proliferation and combined with MTA induced high cellular migration rates in 48 h (p < 0.05). Furthermore, the combination of IDR1018 and MTA also induced high expression levels of DSPP, ALP activity, and the production of calcification nodules. So, IDR-1018 and its combination with MTA could assist in pulp-dentine complex repair process in vitro.

Host defense peptides as immunomodulators: The other side of the coin

Host defense peptides (HDPs) exhibit a broad range of antimicrobial and immunomodulatory activities. In this sense, both functions are like different sides of the same coin. The direct antimicrobial side was discovered first, and widely studied for the development of anti-infective therapies. In contrast, the immunomodulatory side was recognized later and in the last 20 years the interest in this field has been continuously growing. Different to their antimicrobial activities, the immunomodulatory activities of host defense peptides are more effective in vivo. They offer a great opportunity for new therapeutic applications in the fields of anti-infective therapy, chronic inflammatory diseases treatment, novel vaccine adjuvants development and anticancer immunotherapy. These immune related functions of HDPs includes chemoattraction of leukocytes, modulation of inflammation, enhancement of antigen presentation and polarization of adaptive immune responses. Our attempt with this review is to make a careful evaluation of different aspects of the less explored, but attractive immunomodulatory side of the HDP functional coin.

Genetic diversity of Japanese quail cathelicidins

Japanese quail is a low-fat, meat-bird species exhibiting high disease resistance. Cathelicidins (CATHs) are host defense peptides conserved across numerous vertebrate species that play an important role in innate immunity. The activity of host defense peptides can be affected by amino acid substitutions. However, no polymorphisms in avian CATH genes have been reported to date. The aim of this study was to clarify the polymorphisms in CATHs in Japanese quail. DNA for genomic analyses was extracted from the peripheral blood of 99 randomly selected quail from 6 inbred lines. A total of 6, 4, 6, and 4 CjCATH1, -2, -3, and -B1 alleles were identified, respectively. Nine haplotypes, including 4 strain-specific haplotypes, were identified by combining alleles at the CjCATH1, -2, -3, and -B1 loci. In addition, 2 and 1 amino acid substitutions (I145F, Q148H, and P245H) predicted by PROVEAN and PolyPhen-2 to have deleterious effects were detected in CjCATH2 and -B1, respectively. Synthetic CjCATH2 and -B1 peptides exhibited greater antibacterial activity against Escherichia coli than chicken CATH2 and -B1, respectively. Furthermore, the CjCATHB1∗04 peptide exhibited less potent antimicrobial activity than other CjCATHB1 peptides examined. This is the first report of amino acid substitutions accompanied by changes in antibacterial activity in avian CATHs. These findings could be employed as indicators of improvements in innate immune response in poultry.

Toward insights on determining factors for high activity in antimicrobial peptides via machine learning.

The continued and general rise of antibiotic resistance in pathogenic microbes is a well-recognized global threat. Host defense peptides (HDPs), a component of the innate immune system have demonstrated promising potential to become a next generation antibiotic effective against a plethora of pathogens. While the effectiveness of antimicrobial HDPs has been extensively demonstrated in experimental studies, theoretical insights on the mechanism by which these peptides function is comparably limited. In particular, experimental studies of AMP mechanisms are limited in the number of different peptides investigated and the type of peptide parameters considered. This study makes use of the random forest algorithm for classifying the antimicrobial activity as well for identifying molecular descriptors underpinning the antimicrobial activity of investigated peptides. Subsequent manual interpretation of the identified important descriptors revealed that polarity-solubility are necessary for the membrane lytic antimicrobial activity of HDPs.

A defective release of host defense peptides is present in canine atopic skin

The use of dogs as animal model for human atopic dermatitis (AD) is well known. Striking similarities in the pathogenesis of AD have been demonstrated. Similar alteration of host defense peptides (HDP) have been identified in both species. However, the ultrastructural/molecular alterations associated with HDPs secretion in AD have not been elucidated. We were able to use a multidisciplinary approach to investigate the secretion of HDP in canine skin. The contemporary use of indirect immunofluorescence, ELISA and scanning immune-electron microscopy gave fundamental insights in the pathomechanism of HDP alteration in AD. An increased intracellular expression and a reduced secretion of HDPs is present in atopic skin. An increased presence of HDPs was seen on the surface of atopic skin. These results suggested a defective secretion and an increased adhesion of HDPs to atopic corneocytes might be the reason of the reduced killing activity of HDPs in AD.

Antimicrobial and immunomodulatory activity of host defense peptides, clavanins and LL-37, in vitro: An endodontic perspective

Endodontic treatment is mainly based on root canal disinfection and its failure may be motivated by microbial resistance. Endodontic therapy can be benefitted by host defense peptides (HDPs), which are multifunctional molecules that act against persistent infection and inflammation. This study aimed to evaluate the antimicrobial, cytotoxic and immunomodulatory activity of several HDPs, namely clavanin A, clavanin A modified (MO) and LL-37, compared to intracanal medication Ca(OH)2. HDPs and Ca(OH)2 were evaluated by: (1) antimicrobial assays against Candida albicans and Enterococcus faecalis, (2) cytotoxicity assays and (3) cytokine tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1α, IL-6, IL-10 and IL-12 and nitric oxide (NO) production by RAW 264.7 cells incubated with or without heat-killed (HK) C. albicans or E. faecalis combined or not with interferon-γ. The minimum inhibitory concentration (MIC) was established only for E. faecalis (LL-37, 57μM). Considering cytotoxicity, clavanin MO was able to reduce cell viability in many groups and demonstrated lowest LC50. The Ca(OH)2 up-regulated the production of MCP-1, TNF-α, IL-12 and IL-6 and down-regulated IL-1α, IL-10 and NO. Clavanins up-regulated the TNF-α and NO and down-regulated IL-10 production. LL-37 demonstrated up-regulation of IL-6 and TNF-α production and down-regulation in IL-10 and NO production. In conclusion, LL-37 demonstrated better antibacterial potential. In addition, Ca(OH)2 demonstrated a proinflammatory response, while the HDPs modulated the inflammatory response from non-interference with the active cytokines in the osteoclastogenesis process, probably promoting the health of periradicular tissues.

Tissue expression and antibacterial activity of host defense peptides in chicken.

BackgroundHost defence peptides are a diverse group of small, cationic peptides and are important elements of the first line of defense against pathogens in animals. Expression and functional analysis of host defense peptides has been evaluated in chicken but there are no direct, comprehensive comparisons with all gene family and individual genes.ResultsWe examined the expression patterns of all known cathelicidins, β-defensins and NK-lysin in multiple selected tissues from chickens. CATH1 through 3 were predominantly expressed in the bone marrow, whereas CATHB1 was predominant in bursa of Fabricius. The tissue specific pattern of β-defensins generally fell into two groups. β-defensin1-7 expression was predominantly in bone marrow, whereas β-defensin8-10 and β-defensin13 were highly expressed in liver. NK-lysin expression was highest in spleen. We synthesized peptide products of these gene families and analysed their antibacterial efficacy. Most of the host defense peptides showed antibacterial activity against E.coli with dose-dependent efficacy. β-defensin4 and CATH3 displayed the strongest antibacterial activity among all tested chicken HDPs. Microscopic analyses revealed the killing of bacterium by disrupting membranes with peptide treatment.ConclusionsThese results demonstrate dose-dependent antimicrobial effects of chicken HDPs mediated by membrane damage and demonstrate the differential tissue expression pattern of bioactive HDPs in chicken and the relative antimicrobial potency of the peptides they encode.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0866-6) contains supplementary material, which is available to authorized users.

Evasion of innate immunity by Yersinia pseudotuberculosis: LPS biosynthesis genes play a key role in inhibiting the antimicrobial effects of chemokines and other antimicrobial peptides (P1241)

Abstract Host defense peptides, including antimicrobial chemokines, play an essential role in protecting a wide variety of organisms from bacterial infection. In an effort to identify bacterial genes involved in resistance to antimicrobial chemokine mediated cell death we performed random transposon mutagenesis on a population of Yersinia pseudotuberculosis. Through the use of a novel flow cytometric assay these mutant bacteria were then screened for mutations which led to increased binding to the antimicrobial chemokine to the bacterium. Using this strategy we have screened thousands of mutant bacteria and identified several genes that when mutated lead to increased antimicrobial chemokine binding to and killing of bacteria. These genes, which when interrupted lead to increased susceptibility to antimicrobial chemokine mediated cell death, fall into several functional categories including efflux pups, transcriptional regulators and LPS biosynthesis related genes. Understanding how chemokines and other host defense peptides recognize and bind bacteria and how bacteria evade the antimicrobial activity of host defense peptides, could lead to novel drug targets that enhance the innate immune system. In short, the therapeutic use of AMCs to fight infections may be significantly enhanced by simultaneously targeting processes, such as lipopolysaccharide biosynthesis, that are required for resistance to these peptides.

Therapeutic Potential of Host Defense Peptides in Antibiotic-resistant Infections

The emergence of infections caused by multi-drug resistant (MDR) pathogens pose a major burden to modern healthcare. Exacerbating this issue is the substantial decline in development of new classes of antibiotics by pharmaceutical companies. This has led to renewed interest in the therapeutic potential of natural anti-infective agents such as host defense peptides (HDPs). The broad antimicrobial and immunomodulatory activities of HDPs and their synthetic derivatives, coupled with the fact that they do not readily induce microbial resistance, makes them extremely valuable leads in the development of new treatment strategies for MDR infections. This review examines our knowledge of the mechanisms behind multi-drug resistance as well as the properties of HDPs and their therapeutic potential, especially in the case of MDR infections. Challenges to their development as new therapeutics are also discussed.

Mechanisms and Modifications of Naturally Occurring Host Defense Peptides for Anti-HIV Microbicide Development

Despite advances in the treatment of HIV infection, heterosexual transmission of HIV remains high, and vaccines to prevent HIV acquisition have been unfruitful. Vaginal microbicides, on the other hand, have demonstrated considerable potential for HIV prevention, and a variety of compounds have been screened for their activity and safety as anti-HIV microbicides. Among these are the naturally occurring host defense peptides, small peptides from diverse lineages with intrinsic antiviral activity. Naturally occurring host defense peptides with anti-HIV activity are promising candidates for vaginal microbicide development. Their structural variance and accompanying mechanistic diversity provide a wide range of inhibitors whose antiviral activity can be exerted at nearly every stage of the HIV lifecycle. Additionally, peptide modification has been explored as a method for improving the anti-HIV activity of host defense peptides. Structure- and sequence-based alterations have achieved varying success in improving the potency and specificity of anti-HIV peptides. Overall, peptides have been discovered or engineered to inhibit HIV with therapeutic indices of > 1000, encouraging their advancement toward clinical trials. Here we review the naturally occurring anti-HIV host defense peptides, demonstrating their breadth of mechanistic diversity, and exploring approaches to enhance and optimize their activity in order to expedite their development as safe and effective anti-HIV vaginal microbicides.

Oncolytic Activities of Host Defense Peptides

Cancer continues to be a leading source of morbidity and mortality worldwide in spite of progress in oncolytic therapies. In addition, the incidence of cancers affecting the breast, kidney, prostate and skin among others continue to rise. Chemotherapeutic drugs are widely used in cancer treatment but have the serious drawback of nonspecific toxicity because these agents target any rapidly dividing cell without discriminating between healthy and malignant cells. In addition, many neoplasms eventually become resistant to conventional chemotherapy due to selection for multidrug-resistant variants. The limitations associated with existing chemotherapeutic drugs have stimulated the search for new oncolytic therapies. Host defense peptides (HDPs) may represent a novel family of oncolytic agents that can avoid the shortcomings of conventional chemotherapy because they exhibit selective cytotoxicity against a broad spectrum of malignant human cells, including multi-drug-resistant neoplastic cells. Oncolytic activity by HDPs is usually via necrosis due to cell membrane lysis, but some HDPs can trigger apoptosis in cancer cells via mitochondrial membrane disruption. In addition, certain HDPs are anti-angiogenic which may inhibit cancer progression. This paper reviews oncolytic HDP studies in order to address the suitability of selected HDPs as oncolytic therapies.

ChemInform Abstract: Antibiotic Activities of Host Defense Peptides: More to it than Lipid Bilayer Perturbation

AbstractReview: 81 refs.

Genotoxic and cytotoxic activity of host defense peptides against human soft tissue sarcoma in an in vitro model

Soft tissue sarcomas (STSs) are a heterogeneous group of rare, mesenchymal tumors. Treatment with common chemotherapeutic drugs is consistently associated with low response rates and high rates of adverse toxic effects. Host defense peptides (HDPs) are used as part of innate immunity, and many of them act by directly lysing the target cell membrane. Studies have demonstrated high selectivity of HDP analogs against malignant cells because of a relative abundance of negative charges in malignant cell membranes, compared to normal cells. Our aim was to assess the toxic efficacy of [D]-K6L9, [D]-K3H3L9, and Protegrin-1 against the fibrosarcoma cell line, HT1080, and primary human fibroblasts to analyze the potential of these peptides as therapeutic options against STSs. Cell proliferation of the fibrosarcoma cell line, HT1080, and human fibroblasts was determined in vitro after treatment with [D]-K6L9, [D]-K3H3L9, and Protegrin-1. Genotoxicity was examined on the basis of the mild alkali version of single-cell gel electrophoresis (comet assay). Doxorubicin, a commonly used STS chemotherapeutic agent, served as the control. The native HDP, Protegrin-1, could show a cytotoxic tendency against malignant cells, but no selectivity in genotoxic trials. The synthetic peptide, [D]-K6L9, could not show any selective oncolytic activity against sarcoma cells. [D]-K3H3L9 has shown a tendency for toxic selectivity against malignant cells. There is a potential of developing suitable oncolytic candidates with selectivity against malignant cells. [D]-K3H3L9 showed the first promising results, but there has to be further investigation to improve the therapeutic properties of HDPs.

Suppression of Soft Tissue Sarcoma Growth by a Host Defense-Like Lytic Peptide

BackgroundSoft tissue sarcoma (STS) is an anatomically and histologically heterogeneous neoplasia that shares a putative mesenchymal cell origin. The treatment with common chemotherapeutics is still unsatisfying because of association with poor response rates. Although evidence is accumulating for potent oncolytic activity of host defense peptides (HDPs), their potential therapeutic use is often limited by poor bioavailability and inactivation in serum. Therefore, we tested the designer host defense-like lytic D,L-amino acid peptide [D]-K3H3L9 on two STS cell lines in vitro and also in an athymic and syngeneic mouse model. In recent studies the peptide could show selectivity against prostate carcinoma cells and also an active state in serum.Methods In vitro the human synovial sarcoma cell line SW982, the murine fibrosarcoma cell line BFS-1 and primary human fibroblasts as a control were exposed to [D]-K3H3L9, a 15mer D,L-amino acid designer HDP. Cell vitality in physiological and acidic conditions (MTT-assay), cell growth (BrdU) and DNA-fragmentation (TUNEL) were investigated. Membrane damage at different time points could be analyzed with LDH assay. An antibody against the tested peptide and recordings using scanning electron microscopy could give an inside in the mode of action. In vivo [D]-K3H3L9 was administered intratumorally in an athymic and syngeneic (immunocompetent) mouse model with SW982 and BFS-1 cells, respectively. After three weeks tumor sections were histologically analyzed.ResultsThe peptide exerts rapid and high significant cytotoxicity and antiproliferating activity against the malignant cell lines, apparently via a membrane disrupting mode of action. The local intratumoral administration of [D]-K3H3L9 in the athymic and syngeneic mice models significantly inhibited tumor progression. The histological analyses of the tumor sections revealed a significant antiproliferative, antiangiogenic activity of the treatment group.ConclusionThese findings demonstrate the in vitro and in vivo oncolytic activity of [D]-K3H3L9 in athymic and syngeneic mouse models.

Molecular Basis for Anticancer Activity of Host Defense Peptides

The high toxicity of most anticancer chemotherapeutic drugs and their deactivation by multidrug resistant phenotypes motivated an extensive search for drugs with new modes of action. Host defense peptides (HDPs) represent a promising class of natural-source drugs with a distinct mode of action, decreased likelihood of resistance development, and low intrinsic cytotoxicity. However, the development of antitumoral HDP-based compounds has been hindered by poor understanding of the molecular mechanisms of the HDPs’ selective killing of cancer cells.

Antibiotic activities of host defense peptides: more to it than lipid bilayer perturbation

Defensins are small basic amphiphilic peptides (up to 5 kDa) that have been shown to be important effector molecules of the innate immune system of animals, plants and fungi. In addition to immune modulatory functions, they have potent direct antimicrobial activity against a broad spectrum of bacteria, fungi and/or viruses, which makes them promising lead compounds for the development of next-generation antiinfectives. The mode of antibiotic action of defensins was long thought to result from electrostatic interaction between the positively charged defensins and negatively charged microbial membranes, followed by unspecific membrane permeabilization or pore-formation. Microbial membranes are more negatively charged than human membranes, which may explain to some extent the specificity of defensin action against microbes and associated low toxicity for the host. However, research during the past decade has demonstrated that defensin activities can be much more targeted and that microbe-specific lipid receptors are involved in the killing activity of various defensins. In this respect, human, fungal and invertebrate defensins have been shown to bind to and sequester the bacterial cell wall building block lipid II, thereby specifically inhibiting cell wall biosynthesis. Moreover, plant and insect defensins were found to interact with fungal sphingolipid receptors, resulting in fungal cell death. This review summarizes the current knowledge on the mode of action and structure of defensins from different kingdoms, with specific emphasis on their interaction with microbial lipid receptors.

Stability, toxicity, and biological activity of host defense peptide BMAP28 and its inversed and retro‐inversed isomers

Host defense peptides (HDPs) contribute to immune defense through direct antimicrobial activity as well as modulation of host immune responses. While the antimicrobial activity of HDPs has been successfully exploited as topical antibiotics, their use as systemic immunomodulatory antimicrobials has been limited by their toxicity and biological instability. Peptide modification strategies to address these characteristics, while maintaining biological activity, are likely essential to capture the full therapeutic potential of HDPs. Here we investigate the stability, toxicity, and biological activity of the L, inversed (D), and retro-inversed (RI) isomers of BMAP28. The D and RI isomers both form symmetrically related structures to L BMAP28 and resist proteolytic degradation. With respect to toxicity, the considerable hemolytic activity of L BMAP28 is approximately halved with the D isomer and eliminated with RI BMAP28. Furthermore, while D BMAP28 maintains the same cytotoxicity profile against epithelial cells and monocytes as the natural peptide, RI BMAP28 is markedly less toxic against these cell types. As prophylactic antimicrobials, all three isomers significantly reduced bacterial loads [99.99% bacterial clearance by each peptide at the highest dose (20 mg kg(-1) )], when administered 18 h prior to challenge in a mouse model of peritoneal infection. This protection appears to be mediated through neutrophil recruitment and activation of macrophages for bacterial clearance. Collectively, the increased stability and retained biological activity of D and RI BMAP28 make these isomers attractive as antimicrobial therapeutics. In particular, the protection conferred by RI BMAP28, combined with its reduced toxicities, make it a strong candidate for further consideration.

Synthetic Cationic Peptide IDR-1002 Provides Protection against Bacterial Infections through Chemokine Induction and Enhanced Leukocyte Recruitment

With the rapid rise in the incidence of multidrug resistant infections, there is substantial interest in host defense peptides as templates for production of new antimicrobial therapeutics. Natural peptides are multifunctional mediators of the innate immune response, with some direct antimicrobial activity and diverse immunomodulatory properties. We have previously developed an innate defense regulator (IDR) 1, with protective activity against bacterial infection mediated entirely through its effects on the immunity of the host, as a novel approach to anti-infective therapy. In this study, an immunomodulatory peptide IDR-1002 was selected from a library of bactenecin derivatives based on its substantially more potent ability to induce chemokines in human PBMCs. The enhanced chemokine induction activity of the peptide in vitro correlated with stronger protective activity in vivo in the Staphylococcus aureus-invasive infection model, with a >5-fold reduction in the protective dose in direct comparison with IDR-1. IDR-1002 also afforded protection against the Gram-negative bacterial pathogen Escherichia coli. Chemokine induction by IDR-1002 was found to be mediated through a Gi-coupled receptor and the PI3K, NF-kappaB, and MAPK signaling pathways. The protective activity of the peptide was associated with in vivo augmentation of chemokine production and recruitment of neutrophils and monocytes to the site of infection. These results highlight the importance of the chemokine induction activity of host defense peptides and demonstrate that the optimization of the ex vivo chemokine-induction properties of peptides is a promising method for the rational development of immunomodulatory IDR peptides with enhanced anti-infective activity.

Inhibition of early steps in the lentiviral replication cycle by cathelicidin host defense peptides

BackgroundThe antibacterial activity of host defense peptides (HDP) is largely mediated by permeabilization of bacterial membranes. The lipid membrane of enveloped viruses might also be a target of antimicrobial peptides. Therefore, we screened a panel of naturally occurring HDPs representing different classes for inhibition of early, Env-independent steps in the HIV replication cycle. A lentiviral vector-based screening assay was used to determine the inhibitory effect of HDPs on early steps in the replication cycle and on cell metabolism.ResultsHuman LL37 and porcine Protegrin-1 specifically reduced lentiviral vector infectivity, whereas the reduction of luciferase activities observed at high concentrations of the other HDPs is primarily due to modulation of cellular activity and/ or cytotoxicity rather than antiviral activity. A retroviral vector was inhibited by LL37 and Protegrin-1 to similar extent, while no specific inhibition of adenoviral vector mediated gene transfer was observed. Specific inhibitory effects of Protegrin-1 were confirmed for wild type HIV-1.ConclusionAlthough Protegrin-1 apparently inhibits an early step in the HIV-replication cycle, cytotoxic effects might limit its use as an antiviral agent unless the specificity for the virus can be improved.