A synthetic peptide as a novel anticryptococcal agent

Bioactive peptides: an alternative therapeutic approach for cancer management

Cancer is still considered a lethal disease worldwide and the patients' quality of life is affected by major side effects of the treatments including post-surgery complications, chemo-, and radiation therapy. Recently, new therapeutic approaches were considered globally for increasing conventional cancer therapy efficacy and decreasing the adverse effects. Bioactive peptides obtained from plant and animal sources have drawn increased attention because of their potential as complementary therapy. This review presents a contemporary examination of bioactive peptides derived from natural origins with demonstrated anticancer, ant invasion, and immunomodulation properties. For example, peptides derived from common beans, chickpeas, wheat germ, and mung beans exhibited antiproliferative and toxic effects on cancer cells, favoring cell cycle arrest and apoptosis. On the other hand, peptides from marine sources showed the potential for inhibiting tumor growth and metastasis. In this review we will discuss these data highlighting the potential befits of these approaches and the need of further investigations to fully characterize their potential in clinics.

From antimicrobial to anticancer: the pioneering works of Prof. Luiz Rodolpho Travassos on bioactive peptides

Prof. Luiz Rodolpho Travassos, a distinguished Brazilian scientist, was instrumental in fostering an interdisciplinary research approach that seamlessly combined microbiology and oncology. This work has opened new pathways into the understanding of tumorigenesis and aided in the development of innovative therapeutic tools. One significant area of his work has been the exploration of bioactive peptides, many of which were first identified for their antimicrobial properties. These peptides demonstrate promise as potential cancer therapeutics due to their selectivity, cost-effectiveness, ease of synthesis, low antigenicity, and excellent tissue penetration. Prof. Travassos' pioneering work uncovered on the potential of peptides derived from microbiological sources, such as those obtained using phage display techniques. More importantly, in international cooperation, peptides derived from complementarity-determining regions (CDRs) that showed antimicrobial activity against Candida albicans further showed to be promising tools with cytotoxic properties against cancer cells. Similarly, peptides derived from natural sources, such as the gomesin peptide, not only had shown antimicrobial properties but could treat cutaneous melanoma in experimental models. These therapeutic tools allowed Prof. Travassos and his group to navigate the intricate landscape of factors and pathways that drive cancer development, including persistent proliferative signaling, evasion of tumor suppressor genes, inhibition of programmed cell death, and cellular immortality. This review examines the mechanisms of action of these peptides, aligning them with the universally recognized hallmarks of cancer, and evaluates their potential as drug candidates. It highlights the crucial need for more selective, microbiology-inspired anti-cancer strategies that spare healthy cells, a challenge that current therapies often struggle to address. By offering a comprehensive assessment of Prof. Travassos' innovative contributions and a detailed discussion on the increasing importance of microbiology-derived peptides, this review presents an informed and robust perspective on the possible future direction of cancer therapy.

Discovery of Simplified Sampangine Derivatives with Potent Antifungal Activities against Cryptococcal Meningitis

Cryptococcal meningitis (CM) is associated with high morbidity and mortality. Current antifungal drug therapy for CM has the following challenges: limited efficacy, significant side effects, emerging drug resistance, and unavailability in highly needed countries. There is an urgent need to develop novel CM therapeutic agents with a new mode of action. On the basis of the antifungal natural product sampangine, herein, novel simplified isoxazole derivatives were identified to possess excellent inhibitory activity against Cryptococcus neoformans (C. neoformans). Particularly, compound 9a was highly active (the minimum inhibitory concentration of 80% inhibition, MIC₈₀ = 0.031 μg/mL) and significantly inhibited biofilm formation, melanin, and urease production of C. neoformans. 9a had good blood-brain barrier (BBB) permeability and effectively reduced the brain fungal burden in a murine model of cryptococcosis. The antifungal mechanism of compound 9a was preliminarily investigated by transmission electron microscopy and flow cytometry. It was able to cause necrocytosis of C. neoformans cells and cell cycle arrest in the G1/S phase. Isoxazole compound 9a represents a promising lead compound for the development of novel CM therapeutic agents.

Immunotherapy of Fungal Infections

Fungal organisms are ubiquitous in the environment. Pathogenic fungi, although relatively few in the whole gamut of microbial pathogens, are able to cause disease with varying degrees of severity in individuals with normal or impaired immunity. The disease state is an outcome of the fungal pathogen's interactions with the host immunity, and therefore, it stands to reason that deep/invasive fungal diseases be amenable to immunotherapy. Therefore, antifungal immunotherapy continues to be attractive as an adjunct to the currently available antifungal chemotherapy options for a number of reasons, including the fact that existing antifungal drugs, albeit largely effective, are not without limitations, and that morbidity and mortality associated with invasive mycoses are still unacceptably high. For several decades, intense basic research efforts have been directed at development of fungal immunotherapies. Nevertheless, this approach suffers from a severe bench-bedside disconnect owing to several reasons: the chemical and biological peculiarities of the fungal antigens, the complexities of host-pathogen interactions, an under-appreciation of the fungal disease landscape, the requirement of considerable financial investment to bring these therapies to clinical use, as well as practical problems associated with immunizations. In this general, non-exhaustive review, we summarize the features of ongoing research efforts directed towards devising safe and effective immunotherapeutic options for mycotic diseases, encompassing work on antifungal vaccines, adoptive cell transfers, cytokines, antimicrobial peptides (AMPs), monoclonal antibodies (mAbs), and other agents.

Bioprotective Role of Yeasts

The yeasts constitute a large group of microorganisms characterized by the ability to grow and survive in different and stressful conditions and then to colonize a wide range of environmental and human ecosystems. The competitive traits against other microorganisms have attracted increasing attention from scientists, who proposed their successful application as bioprotective agents in the agricultural, food and medical sectors. These antagonistic activities rely on the competition for nutrients, production and tolerance of high concentrations of ethanol, as well as the synthesis of a large class of antimicrobial compounds, known as killer toxins, which showed clearly a large spectrum of activity against food spoilage microorganisms, but also against plant, animal and human pathogens. This review describes the antimicrobial mechanisms involved in the antagonistic activity, their applications in the processed and unprocessed food sectors, as well as the future perspectives in the development of new bio-drugs, which may overcome the limitations connected to conventional antimicrobial and drug resistance.

Antibodies as an unlimited source of anti-infective, anti-tumour and immunomodulatory peptides

Antibodies (Abs) are emerging as an important class of therapeutic agents for the treatment of various human diseases, often conjugated to drugs or toxic substances. In recent years, the incidence of cancer and infectious diseases has increased dramatically making it imperative to discover new effective therapeutic molecules. Among these, small peptides are arousing great interest. Synthetic peptides, representative of variable and constant region fragments of Abs, were proved to exert in vitro, ex vivo and/or in vivo anti-microbial, anti-viral, anti-tumour and/or immunomodulatory activities, mediated by different mechanisms of action and regardless of the specificity and isotype of the Ab. Some of these synthetic peptides possess the ability to spontaneously and reversibly self-assemble in an organised network of fibril-like structure. Ab fragments may represent a novel model of targeted anti-infective and anti-tumour auto-delivering drugs.

Structural and functional studies on a proline-rich peptide isolated from swine saliva endowed with antifungal activity towards Cryptococcus neoformans

A proline-rich peptide of 2733Da, isolated from pig parotid granule preparations was tested against different pathogenic fungi. It showed interesting antifungal activity towards a clinical isolate of Cryptococcus neoformans, with an EC(50) of 2.2μM. Neither cytotoxic nor haemolytic effects were observed towards mammalian cells. Circular dichroism and infrared spectroscopic studies showed that the peptide adopted a combination of polyproline type-II, β-turn and unordered conformations at physiological temperatures. Temperature dependent experiments evidenced a tendency to adopt a polyproline-II helix conformation. From experiments with lipid vesicles, Neutral Red Uptake (NRU), haemolytic assays, and confocal microscopy studies, it could be hypothesized that the peptide may exert its antifungal effect by interacting with an intracellular target rather than through membrane damage.

Antibody Peptide based antifungal immunotherapy

Fungal infections still represent relevant human illnesses worldwide and some are accompanied by unacceptably high mortality rates. The limited current availability of effective and safe antifungal agents makes the development of new drugs and approaches of antifungal vaccination/immunotherapy every day more needed. Among them, small antibody(Ab)-derived peptides are arousing great expectations as new potential antifungal agents. In this topic, the search path from the study of the yeast killer phenomenon to the production of Ab-derived peptides characterized by in vitro and in vivo fungicidal activity will be focused. In particular, Abs that mimic the antimicrobial activity of a killer toxin (“antibiobodies”) and antifungal peptides derived from antibiobodies (killer peptide) and other unrelated Abs [complementarity determining regions (CDR)-based and constant region (Fc)-based synthetic peptides] are described. Mycological implications in terms of reevaluation of the yeast killer phenomenon, roles of antibiobodies in antifungal immunity, of β-glucans as antifungal targets and vaccines, and of Abs as sources of an unlimited number of sequences potentially active as new immunotherapeutic tools against fungal agents and related mycoses, are discussed.

β-Actin-binding complementarity-determining region 2 of variable heavy chain from monoclonal antibody C7 induces apoptosis in several human tumor cells and is protective against metastatic melanoma

Complementarity-determining regions (CDRs) from monoclonal antibodies tested as synthetic peptides display anti-infective and antitumor activities, independent of the specificity of the native antibody. Previously, we have shown that the synthetic peptide C7H2, based on the heavy chain CDR 2 from monoclonal antibody C7, a mAb directed to a mannoprotein of Candida albicans, significantly reduced B16F10 melanoma growth and lung colony formation by triggering tumor apoptosis. The mechanism, however, by which C7H2 induced apoptosis in tumor cells remained unknown. Here, we demonstrate that C7H2 interacts with components of the tumor cells cytoskeleton, being rapidly internalized after binding to the tumor cell surface. Mass spectrometry analysis and in vitro validation revealed that β-actin is the receptor of C7H2 in the tumor cells. C7H2 induces β-actin polymerization and F-actin stabilization, linked with abundant generation of superoxide anions and apoptosis. Major phenotypes following peptide binding were chromatin condensation, DNA fragmentation, annexin V binding, lamin disruption, caspase 8 and 3 activation, and organelle alterations. Finally, we evaluated the cytotoxic efficacy of C7H2 in a panel of human tumor cell lines. All tumor cell lines studied were equally susceptible to C7H2 in vitro. The C7H2 amide without further derivatization significantly reduced lung metastasis of mice endovenously challenged with B16F10-Nex2 melanoma cells. No significant cytotoxicity was observed toward nontumorigenic cell lines on short incubation in vitro or in naïve mice injected with a high dose of the peptide. We believe that C7H2 is a promising peptide to be developed as an anticancer drug.

Killer peptide: a novel paradigm of antimicrobial, antiviral and immunomodulatory auto-delivering drugs

The incidence of life-threatening viral and microbial infections has dramatically increased over recent decades. Despite significant developments in anti-infective chemotherapy, many issues have increasingly narrowed the therapeutic options, making it imperative to discover new effective molecules. Among them, small peptides are arousing great interest. This review will focus in particular on a killer peptide, engineered from an anti-idiotypic recombinant antibody that mimics the activity of a wide-spectrum antimicrobial yeast killer toxin targeting β-glucan cell-wall receptors. The in vitro and in vivo antimicrobial, antiviral and immunomodulatory activities of killer peptide and its ability to spontaneously and reversibly self-assemble and slowly release its active dimeric form over time will be discussed as a novel paradigm of targeted auto-delivering drugs.

A synthetic peptide selectively kills only virulent Paracoccidioides brasiliensis yeasts

This work was conducted to identify virulence biomarkers for Paracoccidioides brasiliensis (Pb), the fungus responsible for Paracoccidioidomycosis (PCM), a systemic disease endemic in Latin America. Measurement of mortality showed that all B10.A mice were killed after 250 days by the virulent Pb18 isolate while only one of the mice that received the attenuated counterpart died. Also, number of lung CFUs from virulent Pb18 inoculated mice were much higher when these isolates were compared. Phage display methodology allowed selection of three phages that specifically bound to virulent Pb18. Variability of p04 phage binding to different Pb isolates were examples of variability of expression by the fungus of its binding molecule, strongly suggesting p04 as a biomarker of virulence. In vitro, its derived peptide pep04 killed only virulent fungi, and confocal microscopy showed that it was internalized only by the virulent isolate. Pep04 blocked establishment of Pb infection in mice and virulent Pb18 pre-incubated with p04 showed significantly inhibited lung infection. Furthermore, infected mice treated with p04 showed highly significant reduction in lung CFUs. These findings firmly establish p04 as a biomarker of Pb virulence. Therefore, after proper peptide engineering, p04 may become a useful adjuvant for the distressing treatment of PCM.

From Pichia anomala killer toxin through killer antibodies to killer peptides for a comprehensive anti-infective strategy

"Antibiobodies", antibodies (Abs) with antibiotic activity, internal image of a Pichia anomala killer toxin (PaKT) characterized by microbicidal activity against microorganisms expressing β-glucans cell-wall receptors (PaKTRs), were produced by idiotypic vaccination with a PaKT-neutralizing monoclonal Ab (PaKT-like Abs) or induced by a protein-conjugated β-glucan. Human natural PaKT-like Abs (PaKTAbs) were found in the vaginal fluid of women infected with KT-sensitive microorganisms. Monoclonal and recombinant PaKT-like Abs, and PaKTAbs proved to be protective against experimental candidiasis, cryptococcosis and aspergillosis. A killer decapeptide (KP), synthesized from the sequence of a recombinant PaKT-like Ab or produced in transgenic plants, showed a microbicidal activity in vitro, neutralized by β-glucans, a therapeutic effect in vivo, against experimental mucosal and systemic mycoses, and a prophylactic role in planta, against phytopathogenic microorganisms, respectively. KP showed fungicidal properties against all the defective mutants of a Saccharomyces cerevisiae library, inclusive of strains recognized to be resistant to conventional antifungal drugs. KP inhibited in vitro, ex vivo and/or in vivo HIV-1 and Influenza A virus replication, owing to down-regulation of CCR5 co-receptors, physical block of the gp120-receptor interaction and reduction in the synthesis of glycoproteins, HA and M1 in particular. KP modulated the expression of costimulatory and MHC molecules on murine dendritic cells, improving their capacity to induce lymphocyte proliferation. KP, proven to be devoid of cytotoxicity on human cells, showed self-assembly-releasing hydrogel-like properties, catalyzed by β 1,3 glucan. PaKT's biotechnological derivatives may represent the prototypes of novel antifungal vaccines and anti-infective drugs characterized by different mechanisms of action.

Antifungal and antitumor models of bioactive protective peptides

Peptides are remarkably reactive molecules produced by a great variety of species and able to display a number of functions in uni-and multicellular organisms as mediators, agonists and regulating substances. Some of them exert cytotoxic effects on cells other than those that produced them, and may have a role in controlling subpopulations and protecting certain species or cell types. Presently, we focus on antifungal and antitumor peptides and discuss a few models in which specific sequences and structures exerted direct inhibitory effects or stimulated a protective immune response. The killer peptide, deduced from an antiidiotypic antibody, with several antimicrobial activities and other Ig-derived peptides with cytotoxic activities including antitumor effects, are models studied in vitro and in vivo. Peptide 10 from gp43 of P. brasiliensis (P10) and the vaccine perspective against paracoccidioidomycosis is another topic illustrating the protective effect in vivo against a pathogenic fungus. The cationic antimicrobial peptides with antitumor activities are mostly reviewed here. Local treatment of murine melanoma by the peptide gomesin is another model studied at the Experimental Oncology Unit of UNIFESP.

Antibody complementarity-determining regions (CDRs): a bridge between adaptive and innate immunity

BACKGROUND

It has been documented that, independently from the specificity of the native antibody (Ab) for a given antigen (Ag), complementarity determining regions (CDR)-related peptides may display differential antimicrobial, antiviral and antitumor activities.

METHODOLOGY/PRINCIPAL FINDINGS

In this study we demonstrate that a synthetic peptide with sequence identical to V(H)CDR3 of a mouse monoclonal Ab (mAb) specific for difucosyl human blood group A is easily taken up by macrophages with subsequent stimulation of: i) proinflammatory cytokine production; ii) PI3K-Akt pathway and iii) TLR-4 expression. Significantly, V(H)CDR3 exerts therapeutic effect against systemic candidiasis without possessing direct candidacidal properties.

CONCLUSIONS/SIGNIFICANCE

These results open a new scenario about the possibility that, beyond the half life of immunoglobulins, Ab fragments may effectively influence the antiinfective cellular immune response in a way reminiscent of regulatory peptides of innate immunity.

Reversible self-assembly: a key feature for a new class of autodelivering therapeutic peptides

Effective delivery is a critical issue in the use of conventional free drugs. Studies on the structure-function relationship of a therapeutic antibody-derived candidacidal decapeptide (killer peptide, KP) revealed its ability to spontaneously and reversibly self-assemble in an organized network of fibril-like structures. This process is catalyzed by 1,3-beta-glucans. While the self-assembled state may provide protection against proteases and the slow kinetic of dissociation assures a release of the active dimeric form over time, the beta-glucan affinity is responsible for targeted delivery. Thus, KP represents a novel paradigm of targeted autodelivering drugs.

Therapeutic activity of an anti-idiotypic antibody-derived killer peptide against influenza A virus experimental infection

The in vitro and in vivo activities of a killer decapeptide (KP) against influenza A virus is described, and the mechanisms of action are suggested. KP represents the functional internal image of a yeast killer toxin that proved to exert antimicrobial and anti-human immunodeficiency virus type 1 (HIV-1) activities. Treatment with KP demonstrated a significant inhibitory activity on the replication of two strains of influenza A virus in different cell lines, as evaluated by hemagglutination, hemadsorption, and plaque assays. The complete inhibition of virus particle production and a marked reduction of the synthesis of viral proteins (membrane protein and hemagglutinin, in particular) were observed at a KP concentration of 4 microg/ml. Moreover, KP administered intraperitoneally at a dose of 100 microg/mice once a day for 10 days to influenza A/NWS/33 (H1N1) virus-infected mice improved the survival of the animals by 40% and significantly decreased the viral titers in their lungs. Overall, KP appears to be the first anti-idiotypic antibody-derived peptide that displays inhibitory activity and that has a potential therapeutic effect against pathogenic microorganisms, HIV-1, and influenza A virus by different mechanisms of action.

Antibody complementarity-determining regions (CDRs) can display differential antimicrobial, antiviral and antitumor activities

BACKGROUND

Complementarity-determining regions (CDRs) are immunoglobulin (Ig) hypervariable domains that determine specific antibody (Ab) binding. We have shown that synthetic CDR-related peptides and many decapeptides spanning the variable region of a recombinant yeast killer toxin-like antiidiotypic Ab are candidacidal in vitro. An alanine-substituted decapeptide from the variable region of this Ab displayed increased cytotoxicity in vitro and/or therapeutic effects in vivo against various bacteria, fungi, protozoa and viruses. The possibility that isolated CDRs, represented by short synthetic peptides, may display antimicrobial, antiviral and antitumor activities irrespective of Ab specificity for a given antigen is addressed here.

METHODOLOGY/PRINCIPAL FINDINGS

CDR-based synthetic peptides of murine and human monoclonal Abs directed to: a) a protein epitope of Candida albicans cell wall stress mannoprotein; b) a synthetic peptide containing well-characterized B-cell and T-cell epitopes; c) a carbohydrate blood group A substance, showed differential inhibitory activities in vitro, ex vivo and/or in vivo against C. albicans, HIV-1 and B16F10-Nex2 melanoma cells, conceivably involving different mechanisms of action. Antitumor activities involved peptide-induced caspase-dependent apoptosis. Engineered peptides, obtained by alanine substitution of Ig CDR sequences, and used as surrogates of natural point mutations, showed further differential increased/unaltered/decreased antimicrobial, antiviral and/or antitumor activities. The inhibitory effects observed were largely independent of the specificity of the native Ab and involved chiefly germline encoded CDR1 and CDR2 of light and heavy chains.

CONCLUSIONS/SIGNIFICANCE

The high frequency of bioactive peptides based on CDRs suggests that Ig molecules are sources of an unlimited number of sequences potentially active against infectious agents and tumor cells. The easy production and low cost of small sized synthetic peptides representing Ig CDRs and the possibility of peptide engineering and chemical optimization associated to new delivery mechanisms are expected to give rise to a new generation of therapeutic agents.

In vitro candidacidal activity of a synthetic killer decapeptide (KP) against Candida albicans cells adhered to resin acrylic discs

BACKGROUND

Oral Candida spp., and C. albicans in particular, are considered as important aetiological agents in the pathogenesis of denture-induced stomatitis. Several studies have reported that C. albicans is able to easily adhere to different medical devices, such as vascular and urinary catheters or acrylic denture surfaces, and that adhesion is a fundamental step in the initial pathogenic process of colonization and further possible infection. Recently, a synthetic decapeptide (KP) derived from the sequence of a single-chain recombinant anti-idiotypic antibody, acting as a functional internal image of a microbicidal, broad spectrum yeast killer toxin, has been reported to kill in vitro C. albicans cells and to exert a therapeutic activity against experimental mucosal and systemic candidiasis.

METHODS

The aim of this study was to evaluate, through a CFU assay, the candidacidal activity of KP on sanded acrylic resin discs, previously colonized by C. albicans cells.

RESULTS AND CONCLUSIONS

At 100 microg/ml KP showed over 90% of killing activity on C. albicans cells adhered to resin discs, when compared with a scramble peptide used as control. The results of this study suggest a potential effect of KP on C. albicans cells adhered on the surface of resin materials, such as prosthetic dentures.

Trichosporon insectorum sp. nov., a new anamorphic basidiomycetous killer yeast

Three killer yeasts, isolated from the gut of insects in Panama and artisanal cheese in Brazil, were shown to be related to the Ovoides clade of the genus Trichosporon. Sequencing of the D1/D2 region of the LSU rDNA and physiological characterization revealed a distinct taxonomic position in relation to known species of the genus. Conspecificity of the three killer isolates was reinforced by similar M13 fingerprinting and killer profiles. We propose a new species in this genus: Trichosporon insectorum. The type strain is CBS 10422(T) (syn. NRRL Y-48120). This anamorphic species produces arthroconidia but not appressoria, and its killer character seems to be associated with dsRNA.

Production of an antimicrobial substance against Cryptococcus neoformans by Paenibacillus brasilensis Sa3 isolated from the rhizosphere of Kalanchoe brasiliensis

An antifungal substance produced by Paenibacillus brasilensis strain Sa3 was preliminary characterized and showed to be stable after treatment with different enzymes and organic solvents and at a wide range of pH, and presented a molecular weight between 3 and 10 kDa. In vitro antagonism of this strain towards Cryptococcus neoformans was investigated by optical and electronic microscopic analyses and a fungicidal effect on C. neoformans was observed. Ultrastructural analysis showed intense changes on the fungus when it was paired cultured with strain Sa3, mainly the detachment of the capsule from the cell wall and the presence of altered organelles in the cytoplasm. This novel antifungal substance produced by P. brasilensis Sa3 may represent a new insight in antifungal therapy mainly against emergent fungi. Also, prospective studies on rhizobacteria of plants as Kalanchoe brasiliensis may offer a potential source for the discovery of bioactive compounds with medical value.

Inhibition of clinical and environmental Cryptococcus neoformans isolates by two Brazilian killer yeasts

Two killer yeast strains (HB55 and HB88) capable of inhibiting human pathogenic fungi were isolated from leaves of Hibiscus rosa-sinensis in Brazil. These isolates were identified by conventional methods and sequencing of the D1/D2 region of the 26S rDNA as Kodamaea ohmeri. They inhibited all Cryptococcus neoformans (vars. neoformans, grubii and gattii) strains tested, including reference, clinical and environmental isolates. The killer phenotype was not cured by thermal treatment.

A killer mimotope with therapeutic activity against AIDS-related opportunistic micro-organisms inhibits ex-vivo HIV-1 replication

OBJECTIVE

To verify whether a synthetic therapeutic killer decapeptide (KP), a functional mimotope of a yeast killer toxin with wide-spectrum microbicidal activity, inclusive of AIDS-related opportunistic micro-organisms, through interaction with beta-glucan receptors, which has been found to possess sequence homology with critical segments in gp160 V1/V2 and V3 loops, may also be inhibiting HIV-1 replication.

METHODS

Primary peripheral blood mononuclear cells (PBMCs) cultures established from HIV-1-infected patients were treated with KP in comparison with zidovudine and supernatants and cells were harvested for analysis of HIV RNA and proviral contents, respectively. Virus production in exogenous in-vitro PBMCs infection with lymphocytotropic and monocytotropic HIV-1 strains was also assessed in presence of KP by enzyme-linked immunosorbent assay HIV p24 gag antigen detection. The binding affinity of KP to CD4, CCR5 and CXCR4 was evaluated on CD4-CCR5 or CD4-CXCR4 transfected astroglioma cell lines.

RESULTS

KP was shown to be devoid of cytotoxicity on PBMCs and to inhibit HIV-1 replication in PBMCs of a patient in the acute phase of infection. The antiretroviral activity of KP, which proved to be more potent than zidovudine at micromolar concentrations, is abolished by beta 1,3-glucan but not by beta 1,6-glucan. Down-regulation of CCR5 co-receptor, and/or physical block of the gp120-receptor interaction are possible mechanisms of KP activity.

CONCLUSION

KP appears to be the first antibody-derived short peptide displaying an inhibitory activity against HIV-1 and related opportunistic micro-organisms by different mechanisms of action.

In vitro acanthamoebicidal activity of a killer monoclonal antibody and a synthetic peptide

OBJECTIVES

To evaluate the in vitro microbicidal activity against Acanthamoeba castellanii of a murine monoclonal anti-idiotypic antibody (KTmAb) and a synthetic killer mimotope (KP), which mimic a yeast killer toxin (KT) characterized by a wide spectrum of antimicrobial activity through interaction with specific cell wall receptors, mainly constituted by beta-glucans.

METHODS

Amoebicidal activity was investigated after incubation of trophozoites under different experimental conditions with laminarinase, KTmAb, KP and a scrambled decapeptide (SP). To confirm the specific interaction of KP with beta-glucans, the experiments were also carried out in the presence of laminarin (beta1-3-glucan) or pustulan (beta1-6-glucan); both glucan molecules were co-incubated with KP or SP.

RESULTS

KTmAb and KP exhibited a time-dependent killing activity, in comparison with SP or heat-inactivated KTmAb; this activity was completely abolished by pre-incubation with laminarin, but not by pustulan. Notably, in vitro amoebicidal activity was observed in the presence of laminarinase, an enzyme that specifically hydrolyses beta-glucans. Furthermore, KP specifically inhibited the growth of Acanthamoeba on infected contact lenses and the remaining adherent KP-treated trophozoites appeared strongly damaged.

CONCLUSIONS

The results indicate that the expression of beta1-3-glucan receptors in the cell membrane is probably modulated during cell growth of A. castellanii and is critical for the killing activity of KT-like molecules. Our data confirm the broad antimicrobial spectra of KTmAb and KP, emphasize the crucial role of beta1-3-glucan in microbial physiology and suggest the potential use of KTmAb and KP in the prevention and therapy of Acanthamoeba infections or in preventing Acanthamoeba contamination during storage of contact lenses.

Activity of an engineered synthetic killer peptide on Leishmania major and Leishmania infantum promastigotes

This study was undertaken to analyze the effect of an engineered, killer decapeptide (KP) on Leishmania major and Leishmania infantum promastigotes. The KP was synthesized on the basis of the sequence of a recombinant, single-chain anti-idiotypic antibody acting as a functional internal image of a yeast killer toxin. The evaluation of in vitro inhibitory activity of KP on L. major and L. infantum, release of intracellular green fluorescent protein (GFP) molecules by L. major, DNA fragmentation, and ultrastructural analysis (TEM) of L. infantum upon KP treatment were performed. KP presented antiproliferative and leishmanicidal activity with LC(50)/1 day of 58 and 72 microM for L. major and L. infantum, respectively. A dose-dependent decrease in proliferation and increase of killing of promastigotes was seen after KP treatment. No DNA fragmentation in L. infantum promastigotes or release of intracellular GFP molecules on peptide treatment of a GFP expressing L. major clone was demonstrated. Moreover the plasma-membrane was not disrupted, but, by TEM analysis, intracellular damage was observed.

Modulation of phenotype and function of dendritic cells by a therapeutic synthetic killer peptide

The strong microbicidal effects of an engineered synthetic killer peptide (KP), which functionally mimics a fungal killer toxin, have been demonstrated extensively. Beta-glucan has been identified as a receptor for KP on fungal cell walls. Although the direct microbicidal and related therapeutic effects have been studied in depth, no information currently exists about the interaction of KP with immune cells. In this study, we exploited the possibility of KP binding to different murine immune cell populations. The results demonstrate that KP binds selectively to dendritic cells (DC) and to a lesser extent, to macrophages but not to lymphocytes and neutrophils; KP binding possibly occurs through major histocompatibility complex (MHC) class II, CD16/32, and cellular molecules recognized by anti-specific intercellular adhesion molecule-grabbing nonintegrin R1 antibodies; and KP modulates the expression of costimulatory and MHC molecules on DC and improves their capacity to induce lymphocyte proliferation. These findings provide evidence that this synthetic KP interacts selectively with DC and modulating their multiple functions, might also serve to improve the immune antimicrobial response.

Production of an engineered killer peptide in Nicotiana benthamiana by using a potato virus X expression system

The decapeptide killer peptide (KP) derived from the sequence of a single-chain, anti-idiotypic antibody acting as a functional internal image of a microbicidal, broad-spectrum yeast killer toxin (KT) was shown to exert a strong microbicidal activity against human pathogens. With the aim to exploit this peptide to confer resistance to plant pathogens, we assayed its antimicrobial activity against a broad spectrum of phytopathogenic bacteria and fungi. Synthetic KP exhibited antimicrobial activity in vitro towards Pseudomonas syringae, Erwinia carotovora, Botrytis cinerea, and Fusarium oxysporum. KP was also expressed in plants by using a Potato virus X (PVX)-derived vector as a fusion to the viral coat protein, yielding chimeric virus particles (CVPs) displaying the heterologous peptide. Purified CVPs showed enhanced antimicrobial activity against the above-mentioned plant pathogens and human pathogens such as Staphylococcus aureus and Candida albicans. Moreover, in vivo assays designed to challenge KP-expressing plants (as CVPs) with Pseudomonas syringae pv. tabaci showed enhanced resistance to bacterial attack. The results indicate that the PVX-based display system is a high-yield, rapid, and efficient method to produce and evaluate antimicrobial peptides in plants, representing a milestone for the large-scale production of high-added-value peptides through molecular farming. Moreover, KP is a promising molecule to be stably engineered in plants to confer broad-spectrum resistance to phytopathogens.

Therapeutic potential of yeast killer toxin-like antibodies and mimotopes

This review focuses on the potential of yeast killer toxin (KT)-like antibodies (KTAbs), that mimic a wide-spectrum KT through interaction with specific cell wall receptors (KTR) and their molecular derivatives (killer mimotopes), as putative new tools for transdisease anti-infective therapy. KTAbs are produced during the course of experimental and natural infections caused by KTR-bearing micro-organisms. They have been produced by idiotypic vaccination with a KT-neutralizing mAb, also in their monoclonal and recombinant formats. KTAbs and KTAbs-derived mimotopes may exert a strong therapeutic activity against mucosal and systemic infections caused by eukaryotic and prokaryotic pathogenic agents, thus representing new potential wide-spectrum antibiotics.

In vitro activity of a monoclonal killer anti-idiotypic antibody and a synthetic killer peptide against oral isolates of Candida spp. differently susceptible to conventional antifungals

BACKGROUND/AIMS

A monoclonal killer anti-idiotypic antibody (mAbK10) and a synthetic killer peptide, acting as internal images of a microbicidal, wide-spectrum yeast killer toxin (KT) have been recently shown to express candidacidal in vitro and an in vivo therapeutic activity against experimental mucosal and systemic candidosis models caused by a reference strain of Candida albicans (10S).

MATERIAL AND METHODS

The in vitro candidacidal activity of mAbK10 and synthetic killer peptide was compared using a colony forming unit assay against a large number of isolates of different Candida spp., obtained from oral saliva of adult diabetic (type 1 and 2) and nondiabetic subjects from Parma (Italy) and London (UK).

RESULTS

Both the KT-mimics exerted a strong dose-dependent candidacidal activity, probably mediated by the interaction with beta-glucan KT receptors on target yeast cells, against all the tested strains, regardless of their species and pattern of resistance to conventional antifungal agents.

CONCLUSIONS

These observations open new perspectives in the design and production of candidacidal compounds whose mechanism reflects that exerted in nature by killer yeasts.

A preliminary analysis of the process of protein secretion and the diversity of putative secreted hydrolases encoded inAspergillus fumigatus: insights from the genome

The genome sequence of Aspergillus fumigatus has enabled the annotation of genes likely to encode secreted enzymes that may be important in underpinning the natural lifestyle of the fungus and its pathogenicity. We summarize the data from the genome sequence relevant to both the process of protein secretion and the predicted hydrolase enzymes secreted by A. fumigatus.