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Evidence from previous works disclosed the antimicrobial, antiviral, anti-tumour and/or immunomodulatory activity exerted, through different mechanisms of action, by peptides expressed in the complementarity-determining regions or even in the constant region of antibodies, independently from their specificity and isotype. Presently, we report the selection, from available databases, of peptide sequences encoded by immunoglobulin genes for the evaluation of their potential biological activities. Synthetic peptides representing the translated products of J lambda and J heavy genes proved to act in vitro against pathogenic fungi, entering yeast cells and causing their death, and exerted a therapeutic effect in a Galleria mellonella model of infection by Candida albicans. No haemolytic, cytotoxic and genotoxic effects were observed on mammalian cells. These findings raise the hypothesis that antibodies could be the evolutionary result of the adaptive combination of gene products ancestrally devoted to innate antimicrobial immunity.

The present work aims at investigating the mechanism of action of the Rb9 peptide, which contains the VHCDR 3 sequence of anti-sodium-dependent phosphate transport protein 2B (NaPi2B) monoclonal antibody RebMab200 and displayed antitumor properties. Short peptides corresponding to the hypervariable complementarity-determining regions (CDRs) of immunoglobulins have been associated with antimicrobial, antiviral, immunomodulatory and antitumor activities regardless of the specificity of the antibody. We have shown that the CDR derived peptide Rb9 induced substrate hyperadherence, inhibition of cell migration and matrix invasion in melanoma and other tumor cell lines. Rb9 also inhibited metastasis of murine melanoma in a syngeneic mouse model. We found that Rb9 binds to and interferes with Hsp90 chaperone activity causing attenuation of FAK-Src signaling and downregulation of active Rac1 in B16F10-Nex2 melanoma cells. The peptide also bound to an adhesion G-protein coupled receptor, triggering a concentration-dependent synthesis of cAMP and activation of PKA and VASP signaling as well as IP-3 dependent Ca2+ release. Hsp90 is highly expressed on the cell surface of melanoma cells, and synthetic agents that target Hsp90 are promising cancer therapeutic drugs. Based on their remarkable antitumor effects, the CDR-H3-derived peptides from RebMab200, and particularly the highly soluble and stable Rb9, are novel candidates to be further studied as potential antitumor drugs, selectively acting on cancer cell motility and invasion.

In recent years, the increase of invasive fungal infections and the emergence of antifungal resistance stressed the need for new antifungal drugs. Peptides have shown to be good candidates for the development of alternative antimicrobial agents through high-throughput screening, and subsequent optimization according to a rational approach. This review presents a brief overview on antifungal natural peptides of different sources (animals, plants, micro-organisms), peptide fragments derived by proteolytic cleavage of precursor physiological proteins (cryptides), synthetic unnatural peptides and peptide derivatives. Antifungal peptides are schematically reported based on their structure, antifungal spectrum and reported effects. Natural or synthetic peptides and their modified derivatives may represent the basis for new compounds active against fungal infections.

Antibody-derived peptides modulate functions of the immune system and are a source of anti-infective and antitumor substances. Recent studies have shown that they comprise amino acid sequences of immunoglobulin complementarity-determining regions, but also fragments of constant regions. VH CDR3 of murine mAb AC-1001 displays antimetastatic activities using B16F10-Nex2 murine melanoma cells in a syngeneic model. The peptide was cytotoxic in vitro in murine and human melanoma cells inducing reactive oxygen species (ROS) and apoptosis by the intrinsic pathway. Signs of autophagy were also suggested by the increased expression of LC3/LC3II and Beclin 1 and by ultrastructural evidence. AC-1001 H3 bound to both G- and F-actin and inhibited tumor cell migration. These results are important evidence of the antitumor activity of Ig CDR-derived peptides.

The synthetic peptide T11F (TCRVDHRGLTF), derived from the constant region of human IgM antibodies, proved to exert a significant activity in vitro against yeast strains, including multidrug resistant isolates. Alanine substitution of positively charged residues led to a decrease in candidacidal activity. A more dramatic reduction in activity resulted from cysteine replacement. Here, we investigated the conformational properties of T11F and its alanine-substituted derivatives by circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. Peptide interaction with Candida albicans cells was studied by confocal and scanning electron microscopy. T11F and most of its derivatives exhibited CD spectra with a negative band around 200 nm and a weaker positive band around 218 nm suggesting, together with NMR coupling constants, the presence of a polyproline II (PPII) helix, a conformational motif involved in a number of biological functions. Analysis of CD spectra revealed a critical role for phenylalanine in preserving the PPII helix. In fact, only the F11A derivative presented a random coil conformation. Interestingly, the loss of secondary structure influenced the rate of killing, which turned out to be significantly reduced. Overall, the obtained results suggest that the PPII conformation contributes in characterising the cell penetrating and fungicidal properties of the investigated peptides.

Microtubules are important drug targets in tumor cells, owing to their role in supporting and determining the cell shape, organelle movement and cell division. The complementarity-determining regions (CDRs) of immunoglobulins have been reported to be a source of anti-tumor peptide sequences, independently of the original antibody specificity for a given antigen. We found that, the anti-Lewis B mAb light-chain CDR1 synthetic peptide Rb44, interacted with microtubules and induced depolymerization, with subsequent degradation of actin filaments, leading to depolarization of mitochondrial membrane-potential, increase of ROS, cell cycle arrest at G2/M, cleavage of caspase-9, caspase-3 and PARP, upregulation of Bax and downregulation of Bcl-2, altogether resulting in intrinsic apoptosis of melanoma cells. The in vitro inhibition of angiogenesis was also an Rb44 effect. Peritumoral injection of Rb44L1 delayed growth of subcutaneously grafted melanoma cells in a syngeneic mouse model. L1-CDRs from immunoglobulins and their interactions with tubulin-dimers were explored to interpret effects on microtubule stability. The opening motion of tubulin monomers allowed for efficient L1-CDR docking, impairment of dimer formation and microtubule dissociation. We conclude that Rb44 VL-CDR1 is a novel peptide that acts on melanoma microtubule network causing cell apoptosis in vitro and melanoma growth inhibition in vivo.

The yeast Wickerhamomyces anomalus has been studied for its wide biotechnological potential, mainly for applications in the food industry. Different strains of W. anomalus have been isolated from diverse habitats and recently from insects, including mosquitoes of medical importance. This paper reports the isolation and phylogenetic characterization of W. anomalus from laboratory-reared adults and larvae of Phlebotomus perniciosus (Diptera: Psychodidae), a main phlebotomine vector of human and canine leishmaniasis. Of 65 yeast strains isolated from P. perniciosus, 15 strains were identified as W. anomalus; one of these was tested for the killer phenotype and demonstrated inhibitory activity against four yeast sensitive strains, as reported for mosquito-isolated strains. The association between P. perniciosus and W. anomalus deserves further investigation in order to explore the possibility that this yeast may exert inhibitory/killing activity against Leishmania spp.

Aflatoxins (AFs) are toxic, carcinogenic, immunosuppressive secondary metabolites produced by some Aspergillus species which colonize crops, including many dietary staple foods and feed components. AFB1 is the prevalent and most toxic among AFs. In the liver, it is biotransformed into AFM1, which is then excreted into the milk of lactating mammals, including dairy animals. AFM1 has been shown to be cause of both acute and chronic toxicoses. The presence of AFM1 in milk and dairy products represents a worldwide concern since even small amounts of this metabolite may be of importance as long-term exposure is concerned. Contamination of milk may be mitigated either directly, decreasing the AFM1 content in contaminated milk, or indirectly, decreasing AFB1 contamination in the feed of dairy animals. Current strategies for AFM1 mitigation include good agricultural practices in pre-harvest and post-harvest management of feed crops (including storage) and physical or chemical decontamination of feed and milk. However, no single strategy offers a complete solution to the issue.

ABSTRACT This review focuses on antibodies (Abs) and their function in immune protection, with particular emphasis on microbicidal Abs. Some aspects of Abs and Ab–drug conjugates as targeting therapeutic agents are also discussed. The main aim, however, is devoted to Ab-derived peptides modulating functions of the immune system and to the latest experimental evidence of Abs as a source of anti-infective and antitumor peptides derived from their complementarity determining regions and constant regions.

Synthetic peptides, representative of sequences related to the complementarity determining regions and constant region of antibodies, proved to exert in vitro, ex vivo and/or in vivo antimicrobial, antiviral, anti-tumour and/or immunomodulatory activities, conceivably mediated by different mechanisms of action and regardless of the specificity and isotype of the belonging immunoglobulin. Antibody-derived peptides can show intrinsic properties of self-aggregation in β structures, able to assemble on molecular targets and dissociate spontaneously, leading to the formation of hydrogels. Whilst the self-assembled state may provide protection against proteases and the slow kinetic of dissociation assures a release of the active form over time, the receptor affinity is responsible for targeted delivery. Peptides derived from single amino acid substitution of bioactive antibody fragments, adopted as surrogates of natural point mutations, displayed further differential biological activities. Overall, these observations allow to envisage that antibodies could represent an unlimited source of new anti-infective and anti-tumour peptides.

Mounting an effective immune response against cancer requires the activation of innate and adaptive immune cells. Metastatic melanoma is the most aggressive form of skin cancer. Immunotherapies that boost the activity of effector T cells have shown a remarkable success in melanoma treatment. Patients, however, can develop resistance to such therapies by mechanisms that include the establishment of an immune suppressive tumour microenvironment. Understanding how metastatic melanoma cells suppress the immune system is vital to develop effective immunotherapies against this disease. In this study, we find that the innate immune cells, macrophages and dendritic cells are suppressed in metastatic melanoma. The Ig-CDR-based peptide C36L1 is able to restore macrophages and dendritic cells’ immunogenic functions and to inhibit metastatic growth in vivo. Mechanistically, we found that C36L1 interferes with the MIF-CD74 tumour-innate immune cells immunosuppressive signalling pathway and thereby restores an effective anti-tumour immune response. C36L1 directly binds to CD74 on macrophages and dendritic cells, disturbing CD74 structural dynamics and inhibiting MIF signalling through CD74. Our findings suggest that interfering with MIF-CD74 immunosuppressive signalling in macrophages and dendritic cells using peptide-based immunotherapy can restore the anti-tumour immune response in metastatic melanoma. Our study provides the rationale for further development of peptide-based therapies to restore the anti-tumour immune response.

As implied by the idiotypic network theory, the interaction between the functional epitope of a microbicidal molecule (X) and its specific cell-wall receptor (RX) on sensitive microorganisms may be imaged by the bond between the idiotype (Id) of a neutralizing monoclonal antibody (anti-X Ab) and its anti-idiotype (anti-Id) X-like Ab (anti-anti-X Ab). Consequently, anti-X Ab Id may mimic RX acting as a vaccine (idiotypic vaccination) for the elicitation of protective anti-Id Abs with antibiotic activity (antibiobodies).

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.

In order to overcome the limitations inherent in current pharmacological treatments for Malassezia pachydermatis, the cause of otitis externa in dogs, the efficacy of a killer decapeptide (KP) was evaluated in vitro and in vivo. Sixteen dogs with naturally occurring M. pachydermatis otitis externa were enrolled, and the in vitro fungicidal activity of KP was evaluated using yeasts recovered from these animals. The therapeutic activity was evaluated in four groups of four animals each. The dogs were topically treated with KP (150 μl, 2 mg/ml) three times per week (group A) or every day (group B), treated with a scramble peptide every day (group C), or left untreated (group D). Assessment of clinical signs (pruritus, erythema, and lichenification and/or hyperpigmentation), expressed as mean of the total clinical index score (mTCIS), the population size of M. pachydermatis at the cytological examination (mean number of yeast cells at 40× magnification [mYC]), and culture testing (mean number of log10 CFU/swab [mCFU]), were conducted daily from the first day of treatment (T0) until two consecutive negative cultures (mCFU ≤ 2). KP showed an in vitro fungicidal effect against M. pachydermatis isolates, with an MFC90 value of 1 μg/ml. The mTCIS, mYC and mCFU were negative only in animals in group B after T8. Daily administration of KP for 8 days was safe and effective in controlling both clinical signs and the population size of M. pachydermatis causing otitis externa, thus offering an alternative to the currently available therapeutic or prophylactic protocols for recurrent cases of Malassezia otitis in dogs.

This research was aimed at the evaluation of the antimicrobial activity exerted by poultry protein hydrolyzates derived from industrial leftovers added to minced turkey meat, intended for the production of burgers for human consumption. Hydrolyzates were obtained through enzymatic hydrolysis from poultry bone and meat trimmings, as by-products from the poultry industry. Colony forming unit assays, under both laboratory and industrial conditions, were performed to assess microbial growth. Poultry protein hydrolyzates inhibited microbial growth occurring in semi-finished turkey meat during the normal retention period because of their water holding capacity resulting in a decreased water activity. Overall, the findings demonstrated that poultry protein hydrolyzates could decrease mesophilic, psychrophilic, and thermophilic bacterial growth for the entire product shelf-life. Bacterial growth inhibition obtained in minced turkey meat by addition of poultry protein hydrolyzates (1.5%), hygroscopic amino acids mixture (1.5%) or sodium chloride (1%) was similar. It is suggested that the use of hydrolyzates could allow the reduction of salt content in poultry meat based products leading to the production of low-sodium turkey food still maintaining acceptable sensory characteristics.

Candida albicans is a commensal organism, commonly inhabiting mucosal surfaces of healthy individuals, as a part of the resident microbiota. However, in susceptible hosts, especially hospitalized and/or immunocompromised patients, it may cause a wide range of infections. The presence of abiotic substrates, such as central venous or urinary catheters, provides an additional niche for Candida attachment and persistence, particularly via biofilm development. Furthermore, Candida biofilm is poorly susceptible to most antifungals, including azoles. Here we investigated the effects of a synthetic killer peptide (KP), known to be active in vitro, ex vivo and/or in vivo against different pathogens, on C. albicans biofilm. Together with a scrambled peptide used as a negative control, KP was tested against Candida biofilm at different stages of development. A reference strain, two fluconazole-resistant and two fluconazole-susceptible C. albicans clinical isolates were used. KP-induced C. albicans oxidative stress response and membrane permeability were also analysed. Moreover, the effect of KP on transcriptional profiles of C. albicans genes involved in different stages of biofilm development, such as cell adhesion, hyphal development and extracellular matrix production, was evaluated. Our results clearly show that the treatment with KP strongly affected the capacity of C. albicans to form biofilm and significantly impairs preformed mature biofilm. KP treatment resulted in an increase in C. albicans oxidative stress response and membrane permeability; also, biofilm-related genes expression was significantly reduced. Comparable inhibitory effects were observed in all the strains employed, irrespective of their resistance or susceptibility to fluconazole. Finally, KP-mediated inhibitory effects were observed also against a catheter-associated C. albicans biofilm. This study provides the first evidence on the KP effectiveness against C. albicans biofilm, suggesting that KP may be considered as a potential novel tool for treatment and prevention of biofilm-related C. albicans infections.

As implied by the idiotypic network theory, the interaction between the functional epitope of a microbicidal molecule (X) and its specific cell-wall receptor (RX) on sensitive microorganisms may be imaged by the bond between the idiotype (Id) of a neutralizing monoclonal antibody (anti-X Ab) and its anti-idiotype (anti-Id) X-like Ab (anti-anti-X Ab). Consequently, anti-X Ab Id may mimic RX acting as a vaccine (idiotypic vaccination) for the elicitation of protective anti-Id Abs with antibiotic activity (antibiobodies).

Background Studies on photodynamic inactivation against microorganisms had a great development in recent years. The aim of this work was to test the application of different laser wavelengths with or without different photosensitizing dyes on Candida albicans cells in vitro and in photodynamic therapy protocols in vivo in larvae of Galleria mellonella . Methods Laser application was realized on C. albicans cells suspended in saline solution or cultured on solid medium for the in vitro study, and in a model of G. mellonella candidal infection for the in vivo study. Three wavelengths (650, 405, and 532 nm) were used in continuous mode with different values of applied fluences: 10, 20 and 30 J/cm 2 for the in vitro study and 10 J/cm 2 for the in vivo study, without and with photosensitizing dyes. Results No growth inhibition was obtained on yeast cells in saline solution without photosensitizers. The maximum inhibition of growth (100%) was obtained with 405 nm diode laser and curcumin at any used fluence. No growth inhibition was observed for yeast cells cultured on solid medium after laser application without dyes. An inhibition was observed after laser application when curcumin and erythrosine were added to the medium. The survival curves of G. mellonella larvae infected with C. albicans with or without the different dyes and after laser application showed a statistically significant difference ( p Conclusions These results show the efficacy of photodynamic inactivation exploiting a suitable combination of light and dyes against C. albicans and the potential of photodynamic therapy for the treatment of candidal infections.

A phosphorylated peptide, named K40H, derived from the constant region of IgMs was detected in human serum by liquid chromatography coupled to high-resolution mass spectrometry. Synthetic K40H proved to exert a potent in vitro activity against fungal pathogens, and to inhibit HIV-1 replication in vitro and ex vivo. It also showed a therapeutic effect against an experimental infection by Candida albicans in the invertebrate model Galleria mellonella. K40H represents the proof of concept of the innate role that naturally occurring antibody fragments may exert against infectious agents, shedding a new light upon the posthumous role of antibodies and opening a new scenario on the multifaceted functionality of humoral immunity.

The present work aims at investigating the mechanism of action of the Rb9 peptide, which contains the V

Synthetic peptides encompassing sequences related to the complementarity-determining regions of antibodies or derived from their constant region (Fc peptides) were proven to exert differential antimicrobial, antiviral, antitumor, and/or immunomodulatory activities in vitro and/or in vivo , regardless of the specificity and isotype of the parental antibody. Alanine substitution derivatives of these peptides exhibited unaltered, increased, or decreased candidacidal activities in vitro . The bioactive IgG-derived Fc N10K peptide (NQVSLTCLVK) spontaneously self-assembles, a feature previously recognized as relevant for the therapeutic activity of another antibody-derived peptide. We evaluated the contribution of each residue to the peptide self-assembling capability by circular-dichroism spectroscopy. The interaction of the N10K peptide and its derivatives with Candida albicans cells was studied by confocal, transmission, and scanning electron microscopy. The apoptosis and autophagy induction profiles in yeast cells treated with the peptides were evaluated by flow cytometry, and the therapeutic efficacy against candidal infection was studied in a Galleria mellonella model. Overall, the results indicate a critical role for some residues in the self-assembly process and a correlation of that capability with the candidacidal activities of the peptides in vitro and their therapeutic effects in vivo .

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.

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.

"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.

Antibodies (Abs), often associated with antimicrobial and antitumor agents, have emerged as an important class of novel drugs for antigen-driven therapeutic purposes in diverse clinical settings, including oncology and infectious diseases. Abs commonly give rise in the treated host to anti-Ab responses, which may induce adverse reactions and limit their therapeutic efficacy. Their modular domain architecture has been exploited to generate alternative reduced formats (Fabs, scFvs, dAbs, minibodies, multibodies), essentially devoid of the Fc region. The presence of complementarity determining regions (CDRs) ensures the maintenance of selective binding to antigens and supports their use for biotechnological and therapeutic applications. Paradigmatic Abs mimicking the wide-spectrum antimicrobial activity of a yeast killer toxin (killer Abs) have revealed the existence of a family of Abs exerting a direct in vitro and/or in vivo microbicidal activity. Based on the variable sequence of an antiidiotypic recombinant killer Ab, CDR-related peptides have been synthesized, engineered by alanine-scanning and selected according to antimicrobial, antiviral and immunomodulatory properties. Irrespective of the native Ab specificity, synthetic CDRs from unrelated murine and human monoclonal Abs, have shown to display differential in vitro, in vivo and/or ex vivo antifungal (Candida albicans), antiviral (HIV-1) and antitumor (melanoma cells) activities. Alanine substitution of single residues of synthetic CDR peptides resulted in further differential increased/unaltered/decreased biological activity. The intriguing potential of Abs as source of antiinfective and antitumor therapeutics will be discussed, in light of recent advances in peptide design, stability and delivery.

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.

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 μg/ml. Moreover, KP administered intraperitoneally at a dose of 100 μg/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.

Antibiobodies are paradigmatic of yeast killer toxin (KT)-like antibodies (KAbs) mimicking the antimicrobial activity of KTs in the frame of the yeast killer phenomenon. Polyclonal, monoclonal and recombinant anti-idiotypic antibiobodies (anti-idiotypic KAbs), internal images of a wide-spectrum KT produced by the yeast Pichia anomala (PaKT), have been produced by immunization with the idiotype of a PaKT-neutralizing monoclonal antibody. Anti-idiotypic KAbs showed microbicidal activity against eukaryotic and prokaryotic pathogenic agents through the interaction with specific KT receptors (KTRs), putatively constituted by beta-glucans. Natural KAbs have been found in animals and humans experimentally or naturally infected by KTR-bearing microorganisms. Recombinant KAb-derived synthetic killer peptides showed further antiviral and immunomodulatory activities. The perspectives of KAbs and killer peptides as potential sources of novel therapeutic agents, and of KTRs and idiotypes as vaccines against infectious diseases are discussed.

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 μg/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.

Short peptide sequences from complementarity-determining regions (CDRs) of different immunoglobulins may exert anti-infective, immunomodulatory and antitumor activities regardless of the specificity of the original monoclonal antibody (mAb). In this sense, they resemble early molecules of innate immunity. C36L1 was identified as a bioactive light-chain CDR1 peptide by screening 19 conserved CDR sequences targeting murine B16F10-Nex2 melanoma. The 17-amino acid peptide is readily taken up by melanoma cells and acts on microtubules causing depolymerization, stress of the endoplasmic reticulum and intrinsic apoptosis. At low concentrations, C36L1 inhibited migration, invasion and proliferation of B16F10-Nex2 cells with cell cycle arrest at G2/M phase, by regulating the PI3K/Akt signaling axis involving Rho-GTPase and PTEN mediation. Peritumor injection of the peptide delayed growth of subcutaneously grafted melanoma cells. Intraperitoneal administration of C36L1 induced a significant immune-response dependent anti-tumor protection in a syngeneic metastatic melanoma model. Dendritic cells stimulated ex-vivo by the peptide and transferred to animals challenged with tumor cells were equally effective. The C36 VL CDR1 peptide is a promising microtubule-interacting drug that induces tumor cell death by apoptosis and inhibits metastases of highly aggressive melanoma cells.

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 μM 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.

The most common antifungal drugs in current clinical use for the treatment of oral candidosis are polyenes and azoles, mainly used topically. Poor glycaemic control in association with other local factors, such as the presence of oral dental prostheses, salivary pH, salivary flow rate and tobacco habits, may lead to the development of oral candidosis. Topical antifungal agents are frequently used to prevent the development of candidal infections in patients with poor metabolic control, particularly in the elderly wearing dentures. The aim of this study was to assess the antifungal susceptibility of Candida isolates to six antifungal agents using a commercially available kit, Fungitest. The isolated were collected from patients affected by diabetes mellitus from two different geographic localities (London, UK, and Parma, Italy) and from a group of healthy non-diabetic subjects. No differences in antifungal susceptibility to the six agents tested were observed between Candida isolates from diabetic and non-diabetic subjects. However, differences were observed between the two geographically different diabetes mellitus populations. Oral yeast isolates from diabetes mellitus patients in the UK more often displayed resistance or intermediate resistance to fluconazole (P=0.02), miconazole (P

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.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.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.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.