SARS-CoV-2 Antibodies in Breastmilk Three and Six Months Postpartum in Relation to the Trimester of Maternal SARS-CoV-2 Infection-An Exploratory Study.

The immune system of neonates is immature and therefore knowledge of possible early-life protection against SARS-CoV-2 infection, such as breastfeeding, is of great importance. Few studies have investigated the presence and duration of SARS-CoV-2 antibodies in breastmilk in relation to the trimester of maternal infection during pregnancy, and none with successful participation from all three trimesters. This study has dual objectives (1) in relation to the trimester of infection to examine the frequency, concentration and duration of IgA and IgG antibodies in breastmilk and blood serum in the third and sixth month post-partum in former SARS-CoV-2-infected mothers and (2) to examine the association in pediatric emergency admission of children within the first six months of life compared to children of non-SARS-CoV-2-infected women. The first objective is based on a prospective cohort and the second is based on a nested case-control design. The study participants are women with a former SARS-CoV-2 infection during pregnancy, whose serology IgG tests at delivery were still positive. Maternal blood and breastmilk samples were collected at three and six months postpartum. Serum IgA frequency three months pp was 72.7% (50%, 90% and 60% in the first, second and third trimester) and 82% six months pp (67%, 91% and 82% in the first, second and third trimester). Breastmilk IgA frequency three months pp was 27% (16.6%, 36% and 20% in first, second and third trimester) and 28% six months pp (0%, 38% and 28% in the first, second and third trimester). The highest IgA concentration in breastmilk was found six months post-partum with infection in the third trimester. Serum IgA was detectable more than 400 days post infection, and serum IgG above threshold was found 430 days after date of infection. We found no correlation between serum IgA and breastmilk IgA, nor between serum IgG and breastmilk IgA regardless of the trimester of infection.

Cross-species comparison of pregnancy-induced GDF15.

Growth differentiation factor 15 (GDF15) is a stress-induced cytokine. Although the exact physiological function of GDF15 is not yet fully comprehended, the significant elevation of circulating GDF15 levels during gestation suggests a potential role for this hormone in pregnancy. This is corroborated by genetic association studies in which GDF15 and the GDF15 receptor, GDNF family receptor alpha like (GFRAL) have been linked to morning sickness and hyperemesis gravidarum (HG) in humans. Here, we studied GDF15 biology during pregnancy in mice, rats, macaques, and humans. In contrast to macaques and humans, mice and rats exhibited an underwhelming induction in plasma GDF15 levels in response to pregnancy (∼75-fold increase in macaques vs. ∼2-fold increase in rodents). The changes in circulating GDF15 levels were corroborated by the magnitude of Gdf15 mRNA and GDF15 protein expression in placentae from mice, rats, and macaques. These species-specific findings may help guide future studies focusing on GDF15 in pregnancy and on the evaluation of pharmacological strategies to interfere with GDF15-GFRAL signaling to treat severe nausea and HG.NEW & NOTEWORTHY In the present study pregnancy-induced changes in circulating growth differentiation factor 15 (GDF15) in rodents, rhesus macaques, and humans are mapped. In sum, it is demonstrated that humans and macaques exhibit a tremendous increase in placental and circulating GDF15 during pregnancy. In contrast, GDF15 is negligibly increased in pregnant mice and rats, questioning a physiological role for GDF15 in pregnancy in rodents.