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Background Since the outbreak of COVID-19, many put their hopes in the rapid development of effective immunizations. For now patient isolation, physical distancing and good hygiene are the sole measures for prevention. Processed breast milk with antibodies against SaRS-CoV-2 may serve as additional protection. We aimed to determine the presence and neutralization capacity of antibodies against SaRS-CoV-2 in breastmilk of mothers who have recovered from COVID-19. Methods This prospective case control study included lactating mothers, recovered from (suspected) COVID-19 and healthy controls. Serum and breastmilk was collected. To assess the presence of antibodies in breastmilk and serum, we used multiple complementary assays, namely ELISA with the SARS-CoV-2 spike protein, SARS-CoV-2 receptor binding domain (RBD) and with the SARS-CoV-2 nucleocapsid (N) protein for IgG and bridging ELISA with the SARS-CoV-2 RBD and N protein for total Ig. To assess the effect of pasteurization breastmilk was exposed to Holder Pasteurization and High Pressure Pasteurization. Results Breastmilk contained antibodies against SARS-CoV-2 using any of the assays in 24 out of 29 (83%) proven cases, in six out of nine (67%) suspected cases and in none of the 13 controls. In vitro neutralization of SARS-CoV-2 clinical isolate virus strain was successful in a subset of serum (13%) and milk samples (26%). Although after pasteurization of the milk SARS-CoV-2 antibodies were detected with both methods of pasteurization, virus neutralizing capacity of those antibodies was only retained with the HPP approach. Conclusion Breastmilk of mothers who recovered from COVID-19 contains significant amounts of IgA against SARS-CoV-2, both before and after pasteurization. Key Points Question Does breastmilk of mothers who have recovered from coronavirus disease 2019 (COVID-19) contain antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)? Findings We provide multiple lines of evidence on the presence of a variety of antibodies against SARS-CoV-2, with no such antibodies present in the controls. These antibodies are capable of neutralizing a clinical isolate of SARS-CoV-2 in vitro. We furthermore show that high pressure pasteurization hardly affects antibody levels and efficacy. Meaning Breastmilk, obtained from mothers who have recovered from COVID-19, may serve as a safe and widely applicable preventive strategy for vulnerable high risk populations

Milk serum contains many immune-active proteins that are sensitive to heat treatment. This study compared the effects of thermal (63 °C, 30 min; 72 °C, 15 s; 85 °C, 5 min) and non-thermal (ultraviolet-C, UV-C; thermo-ultrasonication, TUS) treatments on bovine milk serum proteins by using label-free LC-MS/MS-based proteomics. UV-C (4500 J/L) and TUS (60 W, 6 min) treatments achieved a 5log microbial reduction as determined by plate counting. Proteomics showed that e.g., complement proteins, xanthine dehydrogenase/oxidase, and fatty acid-binding protein decreased significantly (p˂0.05, |fold change|˃1) after thermal treatments, and almost no lactoferrin, immunoglobulin, and lactoperoxidase was retained after heating at 85 °C for 5 min, whereas these proteins were mostly retained after non-thermal treatments. Most of these heat-sensitive proteins were located in membrane and extracellular regions and were involved in cellular and metabolic processes, response to stimulus, binding, immune process and catalytic functions. Finally, part of the proteomics results were verified by ELISA. This study thus provided insights for the development of optimized thermal and novel non-thermal treatments for dairy processing. Industrial relevance As alternatives to thermal processing technique, UV-C and ultrasonication showed a great potential in the processing of milk. This study not only showed that UV-C and ultrasonication were able to largely reduce the microbial load of raw milk, but also better retained the immune-related milk serum proteins than thermal processing, especially for the UV-C treatment. ELISA assays also demonstrated that the LC-MS/MS based proteomics technology used in this study was a robust method for quantifying damage to the milk serum proteome upon processing. Taken together, this study provided insights for development of optimized thermal and novel non-thermal techniques for dairy processing.