In vitro acanthamoebicidal activity of a killer monoclonal antibody and a synthetic peptide.
OBJECTIVE
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.
Fiori
Pier Luigi
PL
Department of Biomedical Sciences, Division of Experimental and Clinical Microbiology, University of Sassari, Viale S. Pietro 43/B, 07100 Sassari, Italy. fioripl@uniss.it
Mattana
Antonella
A
Dessì
Daniele
D
Conti
Stefania
S
Magliani
Walter
W
Polonelli
Luciano
L
D048248:Acanthamoeba castellanii / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D000563:Amebicides / Q000494:pharmacology*; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D002473:Cell Wall / Q000378:metabolism; D003261:Contact Lenses / Q000382:microbiology; D005936:Glucans; D055646:Killer Factors, Yeast; D051379:Mice; D009183:Mycotoxins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D011134:Polysaccharides / Q000494:pharmacology; D047071:beta-Glucans / Q000378:metabolism
D000563:Amebicides; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D005936:Glucans; D055646:Killer Factors, Yeast; D009183:Mycotoxins; D009842:Oligopeptides; D011134:Polysaccharides; D047071:beta-Glucans; C002076:pustulan; C008247:laminaran