RE: Double insurance of holder pasteurization and human milk itself to guarantee the safety of breastfeeding
References
4. Fan HH, Wang LQ, Liu WL, et al. Repurposing of clinically approved drugs for treatment of coronavirus disease 2019 in a 2019-novel coronavirus-related coronavirus model. Chin Med J (Engl) 2020. 133:1051-1056.
5. Fan H, Hong B, Luo Y, et al. The effect of whey protein on viral infection and replication of SARS-CoV-2 and pangolin coronavirus in vitro. Signal Transduct Target Ther 2020. 5:275.
6. Chambers C, Krogstad P, Bertrand K, et al. Evaluation for SARS-CoV-2 in Breast Milk From 18 Infected Women. JAMA 2020. 324:1347-1348.
7. Centeno-Tablante E, Medina-Rivera M, Finkelstein JL, et al. Transmission of SARS-CoV-2 through breast milk and breastfeeding: a living systematic review. Ann N Y Acad Sci 2020. doi:10.1111/nyas.14477.
8. WHO Breastfeeding and COVID-19 for health care workers. May 12, 2020. https://www.who.int/docs/default-source/maternal-health/faqs-breastfeeding-and-covid-19.pdf?sfvrsn=d839e6c0_5.
With great interest we read the article by Unger et al in CMAJ [1]. This work highlighted pasteurization by the Holder method (62.5 °C for 30 min) resulted in complete SARS-CoV-2 inactivation in human milk. In this study, the authors did not see complete inactivation of SARS-CoV-2 in media without human milk (positive control) after pasteurization, which differs from the previous report [2]. Actually, we had similar findings with the authors, and SARS-CoV-2 related coronavirus GX_P2V isolated from pangolin [3, 4] could not be completely inactivated after pasteurization at 62.5 °C for 30 minutes.
As shown in the article, the infectivity of SARS-CoV-2 decreased by about 1 log after incubation with human milk for 30 minutes, which leads the author to speculate that breast milk might have some antiviral activity to SARS-CoV-2. Interestingly, our cover story paper recently published in Signal Transduction and Targeted Therapy showed that in Vero E6 and A549 cell lines, the viral entry and replication of SARS-CoV-2 and pangolin coronavirus GX_P2V could be inhibited significantly, and even completely blocked after incubation with human milk [5]. This is consistent with the epidemiological data that even SARS-CoV-2 RNA were detected in some breast milk samples of mothers infected with SARS-CoV-2, no infectious virus particles have been found to date [6, 7].
Further mechanistic study showed that the whey protein in breast milk could not only block the binding of ACE2 and spike protein of SARS-CoV-2, but also strongly inhibit the activity of SARS-CoV-2 RNA dependent RNA polymerase (RdRp) in a dose-dependent manner, which were crucial for virus entry and viral RNA replication, respectively [5].
Overall, we support the opinion raised by the authors that holder pasteurization is effective in inactivating SARS-CoV-2, and more importantly, breast milk itself including whey protein can effectively block the SARS-CoV-2 infection. All these data suggest that mothers who are positive for COVID-19 should be encouraged to continue breastfeeding [8].
References
1. Unger S, Christie-Holmes N, Guvenc F, et al. Holder pasteurization of donated human milk is effective in inactivating SARS-CoV-2. CMAJ. 2020. 192(31): E871-E874.
2. Chin AW, Chu J, Perera M, et al. Stability of SARS-CoV-2 in different environmental conditions. Lancet Microbe 2020;1:e10.
3. Lam TT, Jia N, Zhang YW, et al. Identifying SARS-CoV-2-related coronaviruses in Malayan pangolins. Nature 2020. 583:282-285.