Kinetics of neutralizing and binding antibody responses following Zika virus infection during pregnancy: A nested analysis of participants from the microcephaly epidemic research group (MERG) and Zika in infants and pregnancy (ZIP) cohorts.

ZIKV infection during pregnancy can result in Congenital Zika Syndrome (CZS) in the newborn. Nevertheless, diagnosing ZIKV infection during pregnancy remains challenging, and the kinetics of the serological response to acute infection remains insufficiently reported in the literature. Using samples collected longitudinally from two cohorts of pregnant women in Brazil, this study aims to estimate the timeframe to reach anti-ZIKV immunoglobulin (IgM) negativity. Additionally, it seeks to describe the positivity of IgM, IgG3, and neutralizing antibodies based on the interval between symptom onset and testing in symptomatic pregnant women. In the cohort of pregnant women who tested ZIKV IgM-positive, the probability of IgM seroreversion after the initial detection. was 40% by 3 months, 75% by 6 months, and 85% by 12 months. Moreover, we observed a decreasing trend in the percentage of ZIKV-positive women with detectable ZIKV-specific IgM antibodies over the 12 months after infection, peaking at 8.1% 1 to 2-months after symptom onset and declining to 1.1% by 4 to 5-months after symptom onset. In contrast, IgG3 and neutralizing antibody detection remained stable over the observation period, with approximately <6% and 50% remaining detectable, respectively. This study adds to the body of evidence on the behavior of the antibody responses in a population of women infected with ZIKV during pregnancy. The findings advance understanding of the probability of seroconversion and seroreversion using different immune markers in ZIKV-infected pregnant women, and have the potential to improve the design of maternal screening and surveillance strategies for ZIKV.