290 - Screening for SARS-CoV-2 Antibodies in Cord Blood to Identify Neonates with In-Utero SARS-CoV-2 Infections

Poster Number: 290
Publication Number: 290.226

Amy Yeh, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States; Allison Bearden, Keck School of Medicine of the University of Southern California, south pasadena, CA, United States; Olivier Pernet, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States; Manoj Biniwale, USC Keck School of Medicine, Los Angeles, CA, United States; Steven Balog, Keck School of Medicine of the University of Southern California, Lancaster, CA, United States; jay p. hudgins, LAC+USC Medical center, Los Angeles, CA, CA, United States; Rangasamy Ramanathan, Keck School of Medicine of USC, Los Angeles, CA, United States; Andrea A. Kovacs, USC, Los Angeles, CA, United States

Background: Although screening for SARS-CoV-2 infection is performed at delivery, there are limited data on rates of mother-to-child transmission (MTCT), as screening is not typically done in earlier stages of pregnancy. Thus, rates of MTCT with undiagnosed, asymptomatic, or symptomatic infections during pregnancy are unknown and are likely greater than current estimates of 4-8%.

Objective: To estimate history of maternal infection and identify possible in-utero SARS-CoV-2 infections through antibody screening of cord blood using a sensitive multiplex antibody assay (Luminex™ xMAP®).

Design/Methods: Cord bloods were collected at LAC+USC Medical Center from October to December 2021 and evaluated for SARS-CoV-2 specific IgG using the Luminex™ xMAP® SARS-CoV-2 Multi-Antigen Antibody EUA Assay that detects antibodies to SARS-CoV-2 antigens N, RBD and S1. Mean Fluorescence Intensity (MFI) can differentiate between natural infection (positive for both N and RBD or S) and vaccine response (positive for RBD or S only). Results were analyzed using the Luminex™ xPonent EUA software using the MPMultiCoV2 protocol. A subset of positive samples were assessed for IgM and IgA antibodies (N, S1, S/RBD) using a modified version of the Luminex™ assay.

Results: Over 200 samples have been collected to date from the first 3 months of this study. Among 100 samples analyzed, 78 (78%) were anti-RBD IgG positive (RBD MFI >700) indicating immunity to SARS-CoV-2 due to either previous infection or vaccination of the mother (Image 1). Importantly, 18 of these 78 (23%) were also anti-N IgG positive suggesting past maternal infection. These 18 were assessed for IgM and IgA antibodies. One of the 18 samples showed high levels of anti-RBD IgM (RBD MFI >5000) and elevated IgA (RBD MFI >200) suggesting recent in-utero transmission and two other samples showed moderate levels of anti-RBD IgM and high levels of IgA (RBD MFI >900 and 300), also indicative of an in-utero transmission, giving a MTCT rate of 17% (Image 2).Conclusion(s): Among 100 cord blood samples, 78% had anti-RBD antibodies indicative of past maternal infection and/or vaccination and 23% had past infection. IgM and/or IgA antibodies were present in three out of 18 (17%) samples with maternal past infection indicating in-utero infection and/or transmission. Cord blood screening is a potential tool to identify SARS-CoV-2 infected and/or exposed neonates who can then be followed for long-term consequences of MTCT of SARS-CoV-2.
Image 1: IgG Antibodies in Cord Blood from 100 Participants
Image 2: Anti-RBD IgA and IgM Antibodies in 18 Participants with Past SARS-CoV-2 Infection