Placental transfer of SARS-CoV-2 specific antibodies from mothers to newborns

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There is transfer of SARS-CoV-2-specific antibodies from mothers to newborns, according to new research presented at SMFM’s 2021 Virtual Annual Meeting.

Previous studies have found that patients infected with SARS-CoV-2 develop high titers of IgG antibodies targeting the Spike (S) protein within the few weeks of infection. Researchers from the Herold Lab at Albert Einstein College of Medicine and Montefiore Medical Center in The Bronx, NY conducted a study to assess and quantify the transfer of these specific IgG antibodies from mothers to infants.

The study included 42 dyads (pregnant patients and their newborns) who were diagnosed with SARS-CoV-2 by PCR assay on nasopharyngeal swabs. Blood was collected from pregnant mothers during admission for delivery and cord blood samples at time of delivery.

Of the 42 women, 16 (38.1%) were diagnosed with SARS-CoV-2 at least 7 days before delivery, and 26 (61.9%) were diagnosed less than 7 days before delivery. All samples were assayed via Multiplex assay for anti-Spike IgM and IgG. Results showed that the anti-Spike IgG were higher in pregnant women who had been diagnosed 7 days or more before delivery when compared to those diagnosed for less than 7 days before delivery, but the concentration of IgM antibodies between both groups was similar.

The IgG antibodies were actively transported across placenta as evidenced by the findings of similar concentration of IgG specific anti-Spike antibodies in the mothers’ and cord blood in those diagnosed >7 days before delivery, but the cord blood levels were lower in those who had been diagnosed within 7 days.

In addition, the neutralizing activity of the antibodies, an important defense against infection, was significantly lower in the pregnant women who had been diagnosed <7 days before delivery and was significantly lower in the cord blood in both groups; suggesting a time sensitive production of this subset of Spike-specific antibodies.

According to their research, transfer and production of the SARS-CoV-2-specific antibodies seems to be dependent on timing of infection. Patients infected with SARS-CoV-2 for a longer period of time before delivery, transfer more antibodies and, specifically, more neutralizing antibodies, to their newborns.