Effects of magainins on ameba and cyst stages of Acanthamoeba polyphaga

Abstract

Amebic keratitis produced by Acanthamoeba spp. is an increasingly important ocular infection in extended-use contact lens wearers. Problems associated with the infection are compounded by the lack of effective and well-tolerated chemotherapeutic agents. The magainins, a group of naturally occurring and synthetic membrane-active peptide compounds, have been shown to be active in vitro against a clinical isolate ofAcanthamoeba polyphaga. Two magainins tested extensively had minimal inhibitory and minimal amebicidal values of 20 and 25 ,ug/ml for magainin MSI-103 and 25 and 40 ,ug/ml for magainin MSI-94, respectively. Both amebastatic and amebicidal activities are enhanced by combining the magainins with silver nitrate (200 ,ug/ml) and/or other marginally effective antimicrobial agents. These combinations have activity against both trophic and cystic stages in the Acanthamoeba life cycle and have promise as antimicrobial agents in the treatment of amebic keratitis.Acanthamoeba keratitis, a potentially sight-threatening disease, has been seen in recent years with increasing frequency (23). Initially recognized as a consequence of corneal trauma (12), recent infections have been increasingly associated with daily-wear soft contact lenses, hard lenses, gas-permeable hard lenses, and combined hard-soft lenses. Any departure from recommended contact lens care which exposes the lens or the lens case to a nonsterile environment contaminated with Acanthamoeba spp. can lead to clinical infection (14, 21). Pain and recurrent epithelial breakdown often accompany the course of the disease. Acanthamoeba keratitis is frequently misdiagnosed as a herpes simplex virus or bacterial keratitis, thus delaying the onset of appropriate therapy (4,11,20,27).The life cycle of Acanthamoeba spp. consists of the trophic ameba alternating with a dormant, thick-walled cyst. During infection, both cysts and trophozoites are found within the cornea (12,15

Structure–activity analysis of buforin II, a histone H2A-derived antimicrobial peptide: The proline hinge is responsible for the cell-penetrating ability of buforin II

“…All these results led us to synthesize a hybrid peptide BUF (5-13)[RLLR] 3 , which contains both the extended ␣-helical region containing a proline hinge, BUF (5-13), and three repeats of the regular ␣-helical motif RLLR. The hybrid peptide BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 showed stronger antimicrobial activity than did BUF (5-21) ( Table 3).…”

“…Designed synthetic buforin II analogs consisting of five repeats of the C-terminal regular ␣-helical motif RLLR or three repeats of RVHRLLR were also synthesized to evaluate the importance of the C-terminal amphipathic helix. In addition, to study the role of the extended ␣-helical region BUF (5-13) containing a proline hinge, we synthesized two hybrid peptides, BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 and BUF (5-13)MG (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 contained BUF (5-13) and three repeats of the regular ␣-helical motif RLLR.…”

“…In addition, to study the role of the extended ␣-helical region BUF (5-13) containing a proline hinge, we synthesized two hybrid peptides, BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 and BUF (5-13)MG (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 contained BUF (5-13) and three repeats of the regular ␣-helical motif RLLR. BUF (5-13)MG (1-14) consisted of BUF (5)(6)(7)(8)(9)(10)(11)(12)(13) and the N-terminal ␣-helix [MG (1)(2)(3)(4)(5)(6)…”

“…BUF (5)(6)(7)(8)(9)(10)(11)(12)(13)[RLLR] 3 contained BUF (5-13) and three repeats of the regular ␣-helical motif RLLR. BUF (5-13)MG (1-14) consisted of BUF (5)(6)(7)(8)(9)(10)(11)(12)(13) and the N-terminal ␣-helix [MG (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)] of magainin II.…”

“…In amphibians, which are rich in antimicrobial peptides, many amphipathic ␣-helical antimicrobial peptides [such as magainins (4), bombinins (5), buforins (6), and dermaseptin (7)] have been isolated from glands in the skin and gastrointestinal tract. These cationic ␣-helical peptides possess a broad range of antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi, as well as protozoa (8)(9)(10). The precise mechanism of the broadspectrum antimicrobial activity of these peptides is not yet fully understood.…”