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N. A. Panjwani, C. Saravanan, Z. Cao, J. Kumar, J. Qiu, A. G. Plaut, D. S. Newburg; Milk Components Inhibit Acanthamoeba-Induced Cytopathic Effect in vitro. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4483.
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Acanthamoebae provoke a vision-threatening, corneal infection known as Acanthamoeba keratitis (AK). Despite the ubiquitous distribution of the parasite, the occurrence of AK is relatively low, and in immunocompetent individuals the only known tissue susceptible to infection by Acanthamoeba is cornea. It is thought that Acanthamoeba-specific IgA antibodies present in mucosal secretions such as human tears, milk and saliva provide protection by inhibiting the adhesion of the parasites to host cells. The goal of the present study was to determine whether human mucosal secretions have the potential to provide protection against Acanthamoeba-induced cytopathic effect (CPE) by an additional mechanism that is independent of IgA.
Breast milk was used as a model of human mucosal secretions. In vitro CPE assays were used to examine the CPE inhibitory effect of IgA-depleted milk and various milk fractions obtained by gel filtration. The activity of amoebic proteinases was examined by zymography.
The IgA-depleted milk inhibited the Acanthamoeba-induced CPE in a concentration-dependent manner. Milk proteins were fractionated into four major fractions by gel filtration on Sephadex G200 (F1 to F4). Of these four fractions, the CPE inhibitory activity was detected largely in fraction F3. In contrast, fractions F1, F2 or F4 lacked CPE inhibitory activity. Moreover, fraction F3 but not F1, F2 or F4 inhibited amoebic proteinases.
The above data in conjunction with the published findings showing that amoebic proteinases are responsible for the induction of Acanthamoeba CPE lead us to propose that human mucosal secretions have the potential to provide protection against Acanthamoeba-induced CPE by an additional mechanism that is independent of IgA and involves the inhibition of cytotoxic proteinases of amoebae.
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