Functional Antibodies Against SARS-CoV-2 Receptor Binding Domain Variants with Mutations N501Y or E484K in Human Milk from COVID-19-Vaccinated, -Recovered, and -Unvaccinated Women.

Background: New variants are evolving in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and receptor binding domain (RBD) mutations have been associated with a higher capacity to evade neutralizing antibodies (NAbs). We aimed at determining the impact of COVID-19 vaccine and infection on human milk antibody titers and activity against the RBD mutations from SARS-CoV-2 variants of concern. Materials and Methods: Milk samples were collected from 19 COVID-19 vaccinated women, 10 women who had a positive COVID-19 PCR test, and 13 unvaccinated women. The titers and NAbs of secretory IgA (SIgA)/IgA, secretory IgM (IgM)/IgM, and IgG against SARS-CoV-2 RBD with mutations N501Y or E484K were measured by using ELISA and a surrogate virus neutralization assay. Results: The titers of human milk IgG against N501Y were higher in the COVID-19 vaccine group than in the no-vaccine group but comparable with the COVID-19 PCR group. Other antibody titers did not differ between the three groups. The titers of SIgA/IgA were higher than those of SIgM/IgM and IgG in all three groups. The titers of SIgM/IgM and the inhibition of NAbs were higher against the mutation E484K than N501Y. Milk NAb did not differ between the three groups, but the inhibition of NAb against binding of the two mutant RBD proteins to their receptor was higher in the COVID-19 vaccine and PCR groups than in milk from prepandemic women. Conclusions: COVID-19 vaccination and exposure of mothers to SARS-CoV-2 influenced the titers and NAbs in breast milk against the variants of concern.

Receptor-binding Domain Severe Acute Respiratory Syndrome Coronavirus 2-specific Antibodies in Human Milk From Mothers With Coronavirus Disease 2019 Polymerase Chain Reaction or With Symptoms Suggestive of Coronavirus Disease 2019.

ABSTRACT: This study aims to compare the receptor-binding domain (RBD) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody titers in human milk between mothers with a confirmed coronavirus disease 2019 (COVID-19) polymerase chain reaction (PCR) test and mothers with viral symptoms suggestive of COVID-19. The area under the curve (AUC) for RBD SARS-CoV-2-specific secretory immunoglobulin A (SIgA)/immunoglobulin A (IgA), secretory immunoglobulin M (SIgM)/immunoglobulin M (IgM), immunoglobulin G (IgG), and free secretory components (fSC) in milk samples from eight mothers with a confirmed COVID-19 PCR, eight mothers with viral symptoms (no PCR testing), and six unexposed mothers (pre-pandemic 2018). AUCs of RBD SARS-CoV-2-specific SIgA/IgA, SIgM/IgM, IgG, and fSC in milk samples were comparable between mothers with confirmed COVID-19 PCR and mothers with viral symptoms of suggestive COVID-19. AUCs of RBD-specific SIgA/IgA, IgG, and fSC were higher in the COVID-19-exposed group than in the unexposed group, and SIgM/IgM tended to be higher in the exposed mothers. In conclusion, women with viral symptoms suggestive of COVID-19 could secrete antibodies and fSC specific to SARS-CoV-2 in human milk.

Influence of Previous COVID-19 and Mastitis Infections on the Secretion of Brain-Derived Neurotrophic Factor and Nerve Growth Factor in Human Milk.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) play a critical role in neurodevelopment, where breast milk is a significant dietary source. The impact of previous COVID-19 infection and mastitis on the concentration of BDNF and NGF in human milk was investigated. METHODS: Concentrations of BDNF and NGF were measured via ELISA in human milk samples collected from 12 mothers with a confirmed COVID-19 PCR, 13 mothers with viral symptoms suggestive of COVID-19, and 22 unexposed mothers (pre-pandemic Ctl-2018). These neurotrophins were also determined in 12 mothers with previous mastitis and 18 mothers without mastitis. RESULTS: The NGF concentration in human milk was lower in the COVID-19 PCR and viral symptoms groups than in the unexposed group, but BDNF did not differ significantly. Within the COVID-19 group, BDNF was higher in mothers who reported headaches or loss of smell/taste when compared with mothers without the respective symptom. BDNF was lower in mothers with mastitis than in mothers without mastitis. CONCLUSIONS: Previous COVID-19 and mastitis infections changed differently the secretion of NGF and BDNF in human milk. Whether the changes in NGF and BDNF levels in milk from mothers with infection influence their infant's development remains to be investigated.

Human Milk Antibodies Against S1 and S2 Subunits from SARS-CoV-2, HCoV-OC43, and HCoV-229E in Mothers with A Confirmed COVID-19 PCR, Viral SYMPTOMS, and Unexposed Mothers.

BACKGROUND: Preexisting immunity to SARS-CoV-2 could be related to cross-reactive antibodies to common human-coronaviruses (HCoVs). This study aimed to evaluate whether human milk antibodies against to S1 and S2 subunits SARS-CoV-2 are cross-reactive to S1 and S2 subunits HCoV-OC43 and HCoV-229E in mothers with a confirmed COVID-19 PCR test, in mothers with previous viral symptoms during COVID-19 pandemic, and in unexposed mothers; Methods: The levels of secretory IgA (SIgA)/IgA, secretory IgM (SIgM)/IgM, and IgG specific to S1 and S2 SARS-CoV-2, and reactive to S1 + S2 HCoV-OC43, and HCoV-229E were measured in milk from 7 mothers with a confirmed COVID-19 PCR test, 20 mothers with viral symptoms, and unexposed mothers (6 Ctl1-2018 and 16 Ctl2-2018) using ELISA; Results: The S2 SARS-CoV-2 IgG levels were higher in the COVID-19 PCR (p = 0.014) and viral symptom (p = 0.040) groups than in the Ctl1-2018 group. We detected a higher number of positive correlations between the antigens and secretory antibodies in the COVID-19 PCR group than in the viral symptom and Ctl-2018 groups. S1 + S2 HCoV-OC43-reactive IgG was higher in the COVID-19 group than in the control group (p = 0.002) but did not differ for the other antibodies; Conclusions: Mothers with a confirmed COVID-19 PCR and mothers with previous viral symptoms had preexisting human milk antibodies against S2 subunit SARS-CoV-2. Human milk IgG were more specific to S2 subunit SARS-CoV-2 than other antibodies, whereas SIgA and SIgM were polyreactive and cross-reactive to S1 or S2 subunit SARS-CoV-2.