JAC Advance Access originally published online on February 28, 2006
Journal of Antimicrobial Chemotherapy 2006 57(5):891-898; doi:10.1093/jac/dkl051
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In vitro acanthamoebicidal activity of a killer monoclonal antibody and a synthetic peptide
1 Department of Biomedical Sciences, Division of Experimental and Clinical Microbiology, University of Sassari, Viale S. Pietro 43/B, 07100 Sassari, Italy; 2 Department of Pharmaceutical Sciences, University of Sassari, Sassari, Italy; 3 Dipartimento di Patologia e Medicina di Laboratorio, Sezione di Microbiologia, University of Parma, Parma, Italy
Received 28 July 2005; returned 1 November 2005; revised 12 December 2005; accepted 5 February 2006
* Corresponding author. Tel: +39-079-228299; Fax: +39-079-228299; E-mail: fioripl{at}uniss.it
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 ß-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 ß-glucans, the experiments were also carried out in the presence of laminarin (ß1-3-glucan) or pustulan (ß1-6-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 ß-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 ß1-3-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 ß1-3-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.
Keywords: Acanthamoeba , antimicrobial peptides , anti-idiotypic antibodies , antibody-derived peptides , killer toxins