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Amoebicidal Activity of Milk, Apo-lactoferrin, sIgA and Lysozyme

Nidia León-Sicairos, DSc; Departamento de Biología Celular, Centro de Investigación y de Estudios, Avanzados del I.P.N. Apdo. 14-740, México, D. F. 07000, México; Hospital Pediátrico de Sinaloa, Depto. Investigación, Blvd. Constitución s/n, Col. Almada, Culiacán, Sinaloa 80200, México
Fernando López-Soto, MSc; Departamento de Biología Celular, Centro de Investigación y de Estudios, Avanzados del I.P.N. Apdo. 14-740, México, D. F. 07000, México
Magda Reyes-López, BSc; Departamento de Biología Celular, Centro de Investigación y de Estudios, Avanzados del I.P.N. Apdo. 14-740, México, D. F. 07000, México
Delfino Godínez-Vargas, MSc; Departamento de Biología Celular, Centro de Investigación y de Estudios, Avanzados del I.P.N. Apdo. 14-740,México, D. F. 07000, México
Cynthia Ordaz-Pichardo, DSc; Unidad Académica Multidisciplinaria Reynosa-Aztlán, Universidad Autónoma de Tamaulipas, Calle 16 y Lago de Chapala, Col. Aztlán, Reynosa, Tamps. 88710, México
Mireya de la Garza, DSc; Departamento de Biología Celular, Centro de Investigación y de Estudios, Avanzados del I.P.N. Apdo. 14-740, México, D. F. 07000, México

Reprint Requests: Mireya de la Garza, DSc, Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del I.P.N., Apdo. 14-740, México, D.F. 07000, México, Tel: 52-55-50613987, Fax: 52-55-50613393, Email: mireya{at}cell.cinvestav.mx

Objectives: To identify amoebicidal components in human milk and the effect of iron on the amoebicidal activity.

Design: Investigation in axenic cultures of Entamoeba histolytica trophozoites.

Methods: Amoebas were treated with 5%–20% of human, bovine and swine milk, with 10% of human milk fractions (i.e., casein, proteins except casein and fat) or with 1 mg/ml of human milk apo-lactoferrin, human secretory immunoglobulin type A (sIgA) and chicken egg-white lysozyme (i.e., purified proteins). Milk proteins were detected using immunoblot. Confocal microscopy was used to define the interaction of milk proteins (100 µM each) and amoebas. Experiments were done at least three times in triplicate, and mean and standard deviations were calculated.

Results: Human and bovine milk were amoebicidal showing a concentration-dependent effect. The amoebicidal effect was increased in the absence of iron. Milk protein fractions, with the exception of casein, were the components responsible for the amoebicidal activity found. Apo-lactoferrin, sIgA and lysozyme were identified in the amoebicidal milk protein fraction. Apo-lactoferrin showed the major amoebicidal effect. These proteins, either alone or in combination, showed a killing effect on the trophozoites. They bound to the amoebic membrane causing cell rounding, lipid disruption and damage.

Conclusions: Milk proteins such as apo-lactoferrin, sIgA and lysozyme are able to kill Entamoeba histolytica trophozoites. This study confirms the importance of feeding breast milk to newborns.

Key Words: Amoebicidal • Apo-lactoferrin • Entamoeba histolytica • Lysozyme • Milk • sIgA