title: Peptide derived from anti-idiotypic single-chain antibody is a potent antifungal agent compared to its parent fungicide HM-1 killer toxin peptide.
abstract: Based on anti-idiotypic network theory in light of the need for new antifungal drugs, we attempted to identify biologically active fragments from HM-1 yeast killer toxin and its anti-idiotypic antibody and to compare their potency as an antifungal agent. Thirteen overlapping peptides from HM-1 killer toxin and six peptides from its anti-idiotypic single-chain variable fragment (scFv) antibodies representing the complementarity determining regions were synthesized. The binding affinities of these peptides were investigated and measured by Dot blot and surface plasmon resonance analysis and finally their antifungal activities were investigated by inhibition of growth, colony forming unit assay. Peptide P6, containing the potential active site of HM-1 was highly capable of inhibiting the growth of Saccharomyces cerevisiae but was less effective on pathogenic fungi. However, peptide fragments derived from scFv antibody exerted remarkable inhibitory effect on the growth of pathogenic strains of Candida and Cryptococcus species in vitro. One scFv-derived decapeptide (SP6) was selected as the strongest killer peptide for its high binding affinity and antifungal abilities on both Candida and Cryptococcus species with IC(50) values from 2.33 × 10(-7) M to 36.0 × 10(-7) M. SP6 peptide activity was neutralized by laminarin, a β-1,3-glucan molecule, indicating this peptide derived from scFv anti-idiotypic antibody retains antifungal activity through interaction with cell wall β-glucan of their target fungal cells. Experimental evidence strongly suggested the possibility of development of anti-idiotypic scFv peptide-based antifungal agents which may lead to improve therapeutics for the management of varieties of fungal infections.
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, Japan.
authors.forename: M Enamul
authors.initials: ME
authors.lastname: Kabir
authors.forename: Nurul
authors.initials: N
authors.lastname: Karim
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Krishnaswamy
authors.forename: Dakshnamurthy
authors.initials: D
authors.lastname: Selvakumar
authors.forename: Masahiko
authors.initials: M
authors.lastname: Miyamoto
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Furuichi
authors.forename: Tadazumi
authors.initials: T
authors.lastname: Komiyama
mesh_terms: D000595:Amino Acid Sequence; D000888:Antibodies, Anti-Idiotypic / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects; D055646:Killer Factors, Yeast / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D057127:Single-Chain Antibodies / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000935:Antifungal Agents; D055646:Killer Factors, Yeast; D010455:Peptides; D057127:Single-Chain Antibodies