Engineered killer mimotopes: new synthetic peptides for antimicrobial therapy.

This review deals with a novel approach to produce synthetic antibiotic peptides (killer mimotopes), similar to those described for the conversion of epitopes into peptide mimotopes, allowing their use as surrogate vaccines. Synthetic peptides pertaining to the complementary determining regions (CDRs) of a recombinant antiidiotypic antibody (PaKTscFv), which mimic the wide spectrum of microbicidal activity of a killer toxin produced by the yeast Pichia anomala (PaKT), have proven to act as structural or functional mimotopes of PaKT. This activity appeared to be mediated by interaction with specific cell wall killer toxin receptors (KTRs), mainly constituted by beta glucans. Killer mimotopes have shown in vitro an impressive microbicidal activity against Candida albicans. They were adopted as a model of PaKT- and PaKTscFv-susceptible microorganisms. Optimization through alanine scanning led to the generation of an engineered decapeptide (KP) of a CDR-L1 pertaining antibody fragment with an enhanced in vitro microbicidal activity. It had a potent therapeutic effect against experimental vaginal and systemic candidiasis in normal and immunodeficient mice caused by flucanozole susceptible and resistant yeast isolates. KP exerted a microbicidal activity in vitro against multidrug-resistant eukaryotic and prokaryotic pathogenic microorganisms, which was neutralized by interaction with laminarin (beta 1,3-glucan). To our knowledge, KP represents the prototype of an engineered peptide fragment derived from a microbicidal recombinant antiidiotypic antibody. It is capable of exerting antimicrobial activity in vitro and a therapeutic effect in vivo presumably acting through interaction with the beta glucan KTR component in the cell walls of pathogenic microorganisms.

Biotechnological approaches to the production of idiotypic vaccines and antiidiotypic antibiotics.

The potential therapeutic activity of a killer toxin produced by the yeast Pichia anomala (PaKT) characterized by its wide spectrum of antimicrobial activity has been exploited through the simulation of its interaction with the specific cell wall receptor (KTR) of PaKT-sensitive microorganisms by the idiotypic network. Killer antiidiotypes (PaKTantiId) produced by idiotypic vaccination with a PaKT-neutralizing monoclonal antibody have proven to confer active and passive immunoprotection in experimental models of systemic and vaginal candidiasis. PaKTantiId-like human anti-KTR antibodies are naturally produced in infections caused by PaKT-sensitive microorganisms. PaKTantiId in its monoclonal and recombinant formats as well as expressed on human commensal bacteria have shown microbicidal activity in vitro and a therapeutic effect in experimental models of infection caused by PaKT-sensitive microorganisms. New perspectives of idiotypic vaccination and antiidiotypic antibiotic therapy and biotechnological approaches to the production of trandisease idiotypic vaccines and wide-spectrum antiidiotypic antibiotics (killer mimotopes) will be discussed as effective tools to fight epidemiologically important mucosal and systemic microbial infections.

Killer anti-idiotypes in the control of fungal infections.

Killer anti-idiotypes (KTantild) bear the internal image of a Pichia anomala toxin (KT), characterized by microbicidal activity against prokaryotic and eukaryotic pathogenic microorganisms presenting specific cell wall receptors (KTR). KTantiId produced by idiotypic vaccination with a KT-neutralizing monoclonal antibody confer active and passive immunoprotection in experimental models of systemic and vaginal candidiasis. KTantild-like human natural anti-KTR antibodies are produced in natural infections caused by KT-sensitive microorganisms. KTantiId in the monoclonal and recombinant forms show therapeutic activity in experimental vaginal candidiasis and Pneumocystis carinii pneumonia. Human commensal bacteria expressing KTantild or killer mimotopes synthesized from the sequence of KtantiId, may represent effective tools to combat fungal infections.

In vitro activity of monoclonal and recombinant yeast killer toxin-like antibodies against antibiotic-resistant gram-positive cocci.

BACKGROUND: Monoclonal (mAbKT) and recombinant single-chain (scFvKT) anti-idiotypic antibodies were produced to represent the internal image of a yeast killer toxin (KT) characterized by a wide spectrum of antimicrobial activity, including gram-positive cocci. Pathogenic eukaryotic and prokaryotic microorganisms, such as Candida albicans, Pneumocystis carinii, and a multidrug-resistant strain of Mycobacterium tuberculosis, presenting specific, although yet undefined, KT-cell wall receptors (KTR), have proven to be killed in vitro by mAbKT and scFvKT. mAbKT and scFvKT exert a therapeutic effect in vivo in experimental models of candidiasis and pneumocystosis by mimicking the functional activity of protective antibodies naturally produced in humans against KTR of infecting microorganisms. The swelling tide of concern over increasing bacterial resistance to antibiotic drugs gives the impetus to develop new therapeutic compounds against microbial threat. Thus, the in vitro bactericidal activity of mAbKT and scFvKT against gram-positive, drug-resistant cocci of major epidemiological interest was investigated. MATERIALS AND METHODS: mAbKT and scFvKT generated by hybridoma and DNA recombinant technology from the spleen lymphocytes of mice immunized with a KT-neutralizing monoclonal antibody (mAb KT4) were used in a conventional colony forming unit (CFU) assay to determine, from a qualitative point of view, their bactericidal activity against Staphylococcus aureus, S. haemolyticus, Enterococcus faecalis, E. faecium, and Streptococcus pneumoniae strains. These bacterial strains are characterized by different patterns of resistance to antibiotics, including methicillin, vancomycin, and penicillin. RESULTS: According to the experimental conditions adopted, no bacterial isolate proved to be resistant to the activity of mAbKT and scFvKT. CONCLUSIONS: scFvKT exerted a microbicidal activity against multidrug resistant bacteria, which may represent the basis for the drug modeling of new antibiotics with broad antibacterial spectra to tackle the emergence of microbial resistance.

A transphyletic anti-infectious control strategy based on the killer phenomenon.

A strategy for the prevention and control of candidiasis, pneumocystosis, and tuberculosis, based on the idiotypic network of the yeast killer effect has been envisaged. Anti-idiotypic antibodies representing the internal image of a candidacidal, pneumocysticidal, and mycobactericidal killer toxin from Pichia anomala and idiotypes of killer toxin-neutralizing monoclonal antibodies mimicking the specific cell wall receptor of sensitive microorganisms might provide a unique approach for engineering innovative antibiotics and vaccines active against taxonomically unrelated pathogenic microorganisms. The rationale of the strategy relies on a phenomenon of microbial competition which has been mutated by the immune system in the response to natural infections.