April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
Comparison Of Pathogenic Potential Of Acanthamoeba Trophozoites, Immature Cysts And Mature Cysts
Author Affiliations & Notes
  • Zhiyi Cao
    Ophthalmology, Tufts University Medical School, Boston, Massachusetts
  • Noorjahan A. Panjwani
    Ophthalmology, Tufts University Medical School, Boston, Massachusetts
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 5807. doi:
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      Zhiyi Cao, Noorjahan A. Panjwani; Comparison Of Pathogenic Potential Of Acanthamoeba Trophozoites, Immature Cysts And Mature Cysts. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5807.

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Abstract

Purpose: : During the years 2003 to 2008, a substantial increase in the incidence of Acanthamoeba keratitis (AK) was noted in a number of countries. This rise has been associated at least in part, with the use of COMPLETE MoisturePLUS multipurpose solution that induces the encystment of Acanthamoeba parasites into immature/early stage cysts. In an effort to understand the possible reason for the recent increase in the AK, the goal of this study was to assess whether the pathogenic potential of immature cysts is greater than that of Acanthamoeba trophozoites and mature cysts.

Methods: : To determine whether the a major virulence protein of Acanthamoeba, the mannose-binding protein (MBP), that mediates the adhesion of amoebae to the surface of the cornea plays a role in the process of encystment, the trophozoites were incubated in the encystment medium in the presence and absence of α-mannose and the data were analyzed to determine whether inhibiting the function of the MBP by the competing sugar, mannose, prevents parasite encystment. In an effort to assess the pathogenic potential, the ability of Acanthamoeba trophozoites, immature cysts and mature cysts to withstand harsh conditions, bind to host cells and produce cytopathic effect was investigated.

Results: : The first step in the process of encystment, the clumping of the trophozoites, was inhibited by free mannose but not other irrelevant saccharides. This suggests that Acanthamoeba MBP plays a role in the process of encystment. Both immature cysts and trophozoites expressed MBP, adhered to corneal epithelial cells and produced cytopathic effect. However, immature cysts but not trophozoites were resistant to harsh conditions such as sonication. Although, mature cysts were resistant to harsh conditions, they expressed little MBP and did not bind to host cells or produced cytopathic effect

Conclusions: : Acanthamoeba MBP plays a role in the process of encystment. Immature cysts may be more pathogenic than trophozoites as they are resistant to harsh conditions and have retained the ability to produce cytopathic effect.

Keywords: Acanthamoeba • keratitis • microbial pathogenesis: experimental studies 
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