Table_1_Durable antibody and effector memory T cell responses in breastmilk from women with SARS-CoV-2.xlsx

BackgroundGiven that only 25% of pregnant women elect to receive a COVID-19 vaccine, maternal SARS-CoV-2 infection remains an important route of conferring protective passive immunity to breastfed infants of mothers who are not vaccinated.
MethodsWe enrolled 30 lactating participants between December 2020 and March 2021 who had a positive PCR-test and their first COVID-19 symptoms within the previous 21 days. Participants were asked to provide serial bilateral milk samples at 12 timepoints (~ every 3 days) over a period of 35 days. A second set of samples was collected at least four months after the beginning of the first set. Participants also were asked to provide their dried blood spots and infant stool samples. All samples were tested for receptor-binding domain (RBD)-specific immunoglobulin (Ig)A, IgG, and IgM. Milk samples were assessed for neutralizing ability against the spike protein and four SARS-CoV-2 variants: D614G, Alpha (B.1.1.7), Beta (B.1.351), and Gamma (P.1). Permeability of the breast epithelium was assessed by measuring the sodium to potassium ions (Na:K) in milk. Using flow cytometry, memory CD4 and CD8 T cells (CD45RO+ and CCR7+/-) and mucosal-homing CD4 and CD8 T cells (CD103+) were determined in cells from milk expressed at 35 days and at least 4 months after their first milk donation.
ResultsMilk antibodies from SARS-CoV-2 positive participants neutralized the spike complex. Milk from 73, 90, and 53% of participants had binding reactivities to RBD-specific IgA, IgG, and IgM, respectively. In contrast to blood spots, which showed increased levels of IgG, but not IgA or IgM, the COVID-19 response in milk was associated with a robust IgA response. Twenty-seven percent of participants had increased breast-epithelium permeability, as indicated by Na:K ≥ 0.6. The percentage of CD45RO+CCR7- effector-memory T cells in the day ≥120 milk samples was significantly higher than day 35 samples (P< 0.05).
ConclusionsAntibodies in milk from participants with recent SARS-CoV-2 infection and those who recovered can neutralize the spike complex. For the first time we show that breastmilk T cells are enriched for mucosal memory T cells, further emphasizing the passive protection against SARS-CoV-2 conferred to infants via breastmilk.

背景：仅有25%的孕妇选择接种新型冠状病毒肺炎（COVID-19）疫苗，因此母体感染严重急性呼吸综合征冠状病毒2（SARS-CoV-2）仍是为未接种疫苗的母乳喂养婴儿提供保护性被动免疫的重要途径。
方法：本研究于2020年12月至2021年3月期间纳入30名哺乳期参与者，所有参与者的聚合酶链式反应（PCR）检测结果均呈阳性，且在入组前21天内首次出现COVID-19相关症状。要求参与者在35天周期内的12个时间节点（约每3天一次）采集系列双侧乳汁样本；在第一组样本采集完成至少4个月后，采集第二组样本。此外，参与者还需提供干血斑样本以及婴儿粪便样本。所有样本均针对受体结合域（RBD）特异性免疫球蛋白A（IgA）、免疫球蛋白G（IgG）及免疫球蛋白M（IgM）进行检测。对乳汁样本开展中和活性评估，检测其针对刺突蛋白及四种SARS-CoV-2变异株（D614G、Alpha（B.1.1.7）、Beta（B.1.351）及Gamma（P.1））的中和能力。通过检测乳汁中钠钾离子比（Na:K）评估乳腺上皮通透性。采用流式细胞术，对采集于第35天以及首次捐乳后至少4个月的乳汁细胞进行分析，检测记忆性CD4 T细胞、CD8 T细胞（CD45RO+且CCR7+/-）以及黏膜归巢CD4 T细胞、CD8 T细胞（CD103+）的比例。
结果：SARS-CoV-2感染阳性参与者的乳汁抗体可中和刺突复合物。分别有73%、90%及53%的参与者的乳汁样本对RBD特异性IgA、IgG及IgM具有结合活性。与干血斑样本仅表现为IgG水平升高（IgA及IgM水平无显著变化）不同，乳汁中的COVID-19免疫应答以显著的IgA应答为特征。27%的参与者出现乳腺上皮通透性升高，表现为Na:K≥0.6。在采集于入组后≥120天的乳汁样本中，CD45RO+CCR7-效应记忆T细胞的比例显著高于第35天的乳汁样本（P<0.05）。
结论：近期感染SARS-CoV-2以及已康复参与者的乳汁中的抗体可中和刺突复合物。本研究首次证实母乳中富含黏膜记忆T细胞，进一步强调了母乳为婴儿提供的针对SARS-CoV-2的被动免疫保护作用。