Erratum: Characterization of Human Breast Milk Leukocytes and Their Potential Role in Cytomegalovirus Transmission to Newborns

<b><i>Background:</i></b> Breast milk is the primary source of cytomegalovirus (CMV) transmission to newborns and premature infants. The role of cell-free milk whey in virus transmission is well understood, yet the knowledge about the role of milk cells in this process is scarce. <b><i>Objective:</i></b> To preliminarily characterize different breast milk cell types during various stages of lactation to evaluate their potential role in the transmission of CMV. <b><i>Materials and Methods:</i></b> Breast milk cells of 18 lactating and 3 CMV-seropositive mothers of preterm infants were isolated and characterized for expression of myeloid markers by flow cytometry. In parallel, cytospin preparations were stained with α-naphthyl acetate esterase to identify milk macrophages and describe the dynamic changes of the macrophage-granulocyte population during lactation. The influence of different time points of lactation was analyzed by FACS analysis of double-stained (CD15/CD66b) milk cells. To characterize CMV target cells in breast milk, we enriched CD14+ cells by MACS (Miltenyi) and monitored cell fractions using CMV IEEx4 nested PCR and pp67 CMV RNA by NASBA. <b><i>Results:</i></b> Virolactia, viral DNAlactia, and viral pp67 late mRNA could be detected in breast milk cells only in defined time periods. Granulocytes and macrophages demonstrated an inverse dynamic with neutrophils predominating in the early stages (&lt;30 days postpartum) and macrophages in later stages (&gt;60 days postpartum) of lactation. Enrichment of CD14-positive cells resulted in viral DNA and pp67 late mRNA detection. <b><i>Conclusions:</i></b> Granulocytes and monocytes/macrophages are the predominating cell populations in breast milk with changing frequencies during early lactation. These results demonstrate that CD14-positive breast milk cells seem to be one of the target cells for CMV in breast milk.

<b><i>研究背景：</i></b> 母乳是巨细胞病毒（cytomegalovirus, CMV）传播给新生儿与早产儿的主要途径。目前学界已明确无细胞母乳清液在病毒传播中的作用，然而对于母乳细胞在该传播过程中所发挥的作用却知之甚少。<b><i>研究目的：</i></b> 本研究旨在对泌乳不同阶段的各类母乳细胞进行初步鉴定，以评估其在CMV传播过程中的潜在作用。<b><i>材料与方法：</i></b> 本研究分离了18名泌乳女性及3名CMV血清阳性的早产儿母亲的母乳细胞，并通过流式细胞术（flow cytometry）分析髓系标志物的表达情况。同时，采用乙酸α-萘酯酶染色对细胞离心涂片标本进行染色，以鉴定母乳巨噬细胞，并描绘泌乳过程中巨噬细胞-粒细胞群体的动态变化。随后，通过对双标记（CD15/CD66b）母乳细胞进行荧光激活细胞分选（fluorescence-activated cell sorting, FACS）分析，探究泌乳不同时间点的影响。为鉴定母乳中的CMV靶细胞，本研究通过美天旎磁活化细胞分选（magnetic-activated cell sorting, MACS）系统富集CD14⁺细胞，并分别采用CMV IEEx4巢式聚合酶链式反应（nested polymerase chain reaction, nested PCR）与核酸序列依赖扩增（nucleic acid sequence-based amplification, NASBA）技术，检测细胞组分中的CMV IEEx4与pp67 CMV RNA。<b><i>研究结果：</i></b> 乳汁病毒血症、病毒DNA血症以及病毒pp67晚期mRNA仅能在特定时间段的母乳细胞中被检测到。粒细胞与巨噬细胞呈现此消彼长的动态变化：泌乳早期（产后<30天）以中性粒细胞为主，泌乳后期（产后>60天）则以巨噬细胞为主。富集CD14阳性细胞后，可检测到病毒DNA与pp67晚期mRNA。<b><i>研究结论：</i></b> 粒细胞与单核细胞/巨噬细胞是母乳中的主要细胞群体，其在泌乳早期的占比会发生动态变化。本研究结果表明，CD14阳性母乳细胞或是母乳中CMV的靶细胞之一。