Persistence of anti-spike antibody in samples from 6-month infants
correlates with anti-S IgG placental transfer ratio in a Brazilian
Cohort
Abstract
The precise effects of infection and maternal vaccination during
pregnancy on the fetus remain uncertain. Therefore, this study aims to
investigate the immunological responses triggered by SARS-CoV-2 exposure
or vaccination in pregnant women. However, we also evaluated the
vertical antibody transmission and the persistence of immunity in
infants up to six months post-birth. The study recruited pregnant women
admitted for labor and delivery in Fortaleza, Brazil, between January
2021 and March 2022. Participants aged 18 or older with flu-like
symptoms were included. Nasopharyngeal swabs and blood samples were
collected for COVID-19 testing and antibody detection for the viral
Nucleocapsid (N) and Spike (S) of SARS-CoV-2. Participants were
categorized as Unvaccinated or Vaccinated, and further divided based on
PCR test results. Blood or plasma samples were collected at birth and
from infants at six months postpartum. We included 76 mother-infant
dyads, 11 in the unvaccinated/PCR-/IgG+, 39 in the unvaccinated/PCR+, 20
in the vaccinated/PCR- and 6 in the vaccinated/PCR+. Analysis of
maternal serological profiles showed no significant differences in
anti-N IgG levels between unvaccinated and vaccinated groups. However,
anti-S IgG titers were significantly higher in vaccinated mothers. The
ratio of anti-S IgG antibody transfer from vaccinated mothers to infants
was notably higher, especially in the Unvaccinated/PCR+ group compared
to the Vaccinated/PCR- group. Furthermore, infants born to vaccinated
mothers maintained seroconversion at six months, while those born to
unvaccinated mothers did not. Maternal vaccination, particularly during
the second trimester, results in a significantly higher transplacental
transfer ratio. This leads to elevated anti-S IgG antibody levels in
cord blood and infants at six months of age. The study emphasizes the
importance of vaccination protocols in optimizing antibody transfer and
persistence.