Abstract
Objectives: Human milk contains immunomodulatory proteins that support infant immune development. Conventionally, human donor human milk is treated with Holder pasteurization (HoP) which can inactivates various bioactive proteins, including many related to immune function. The loss of immunomodulatory proteins in donor human milk may result in a reduced ability to protect preterm infants. Therefore, there is a critical need for alternative methods to better preserving its immune-related proteins. Our objective was to evaluate whether human milk treated with high pressure processing (HPP) or ultraviolet-C (UV-C) retains more immunomodulatory activity compared with HoP.
Methods: The capacity of intact soluble proteins extracted from raw, HPP (500 MPa for 9 min), UV-C (12,000 J/L) and HoP-processed milk to modulate inflammatory responses in lipoploysaccharide-challenged macrophages was evaluated. The relative abundance of proteins in differently processed milk was determined via LC-MS/MS-based proteomics.
Results: Protein extracted from raw, HPP-processed, UV-C-processed human donor milk, but not HoP-processed human donor milk, at 0.5 and 1 mg/mL significantly reduced IL-8 levels compared to the control. When the protein concentration was increased to 2 mg/mL, all groups significantly reduced IL-8 levels with Raw, UV-C attenuated more IL8 than HoP. For TNFα, no effect was observed for all protein samples at 0.5 mg/mL. Protein extracts from Raw milk, HPP- and UV-C-treated milk at 1 and 2 mg/mL showed a stronger attenuation effect on TNFα secretion compared to that from HoP-treated milk. Relative proteomic data revealed that ten proteins were significantly lower in HoP but not in HPP and UV-C compared with Raw, including lactoferrin, macrophage mannose receptor 1, sulfhydryl oxidase 1, monocyte differentiation antigen CD14, immunoglobulin heavy constant gamma 1, phosphatidylethanolamine-binding protein 1, tissue alpha-L-fucosidase, alcohol dehydrogenase [NADP(+)], synaptic vesicle membrane protein VAT-1 homolog and calmodulin.
Conclusions: HPP and UV-C are superior to HoP in preserving the immunomodulatory protein profile and activity of donor human milk.