Milk components inhibit Acanthamoeba-induced cytopathic effect.
OBJECTIVE
Acanthamoebae provoke a vision-threatening corneal infection known as Acanthamoeba keratitis (AK). It is thought that Acanthamoeba-specific IgA antibodies present in mucosal secretions such as human tears, milk, and saliva provide protection against infection by inhibiting the adhesion of parasites to host cells. The goal of the present study was to determine whether human mucosal secretions have the potential to provide protection against the Acanthamoeba-induced cytopathic effect (CPE) by an additional mechanism that is independent of IgA.


METHODS
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 amebic proteinases was examined by zymography.


RESULTS
IgA-depleted milk inhibited the Acanthamoeba-induced CPE in a concentration-dependent manner. Milk proteins were separated into four major fractions (F1-F4) by gel filtration. Of these four fractions, CPE inhibitory activity was detected largely in fraction F3. In contrast, fractions F1, F2, and F4 lacked CPE inhibitory activity. Moreover, fraction F3, but not F1, F2, or F4, inhibited amebic proteinases.


CONCLUSIONS
These data, in conjunction with published findings showing that amebic proteinases are responsible for the induction of Acanthamoeba CPE, led 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 that involves the inhibition of cytotoxic proteinases of amebae.
Saravanan
Chandrassegar
C
Department of Anatomy and Cell Biology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA.
Cao
Zhiyi
Z
Kumar
Janardan
J
Qiu
Jiazhou
J
Plaut
Andrew G
AG
Newburg
David S
DS
Panjwani
Noorjahan
N
D000048:Acanthamoeba / Q000187:drug effects* / Q000502:physiology*; D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D002850:Chromatography, Gel; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D019573:Epithelium, Corneal / Q000469:parasitology*; D005260:Female; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000502:physiology; D008858:Microscopy, Phase-Contrast; D008894:Milk Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D008895:Milk, Human / Q000502:physiology*; D008970:Molecular Weight; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors; D011817:Rabbits
D007071:Immunoglobulin A, Secretory; D008894:Milk Proteins; D015800:Protozoan Proteins