2805. Kinetics of Anti-Zika Virus (ZIKV) Antibodies after Acute Infection in Pregnant Women

BACKGROUND: The kinetics and specificity of anti-ZIKV antibodies after acute ZIKV infection is not well known, especially in areas where different flaviviruses circulate. The objective of this study was to describe the kinetics of anti-ZIKV antibodies in pregnant women in whom an acute ZIKV infection was identified during pregnancy. METHODS: Within a cohort of pregnant women living in Guadeloupe and exposed to ZIKV during the 2016 zika outbreak, we identified 65 women who presented with an acute, symptomatic PCR-confirmed ZIKV infection at various times of their pregnancy, with a known date of first Zika symptom. Anti-ZIKV neutralizing antibodies (using a Virus Neutralisation Test (VNT)) and anti-ZIKV NS1 antibodies (using IgM and IgG ELISA Euroimmun® kits) were searched for on frozen serum samples obtained from blood drawn at the time of delivery in all women and at various times between acute infection and delivery in 23 women. RESULTS: Patients’ mean age was 30 years and ZIKV infection had occurred during the first, second, and third trimester of pregnancy in 14 (21%), 35 (54%), and 16 (25%) women, respectively. ZIKV serology on delivery samples was positive in 65/65 (100%; one-sided 97.5% CI: 94.4%–100%) women by both VNT and IgG ELISA assays and in 5/65 (8%) women by IgM ELISA assay. In these 5 cases, median time between first symptom and sampling date was 36 days. Results of ELISA assays on the intermediate samples were as follows: IgG antibodies were negative in all 5 samples that had been drawn within 7 days of first symptom and positive in the 18 samples that had been drawn afterwards; IgM antibodies were positive in 10 of the 19 samples that had been drawn within 3 months of first symptom and negative in 2 of the 4 samples that had been drawn afterwards. CONCLUSION: After acute ZIKV infection, IgG antibodies developed and remained detectable until delivery by a commercially available ELISA assay in all women tested. These antibodies were specific of ZIKV, with concomitantly positive VNT results. From these findings, the absence of ZIKV antibodies at delivery would strongly indicate the absence of infection during pregnancy. DISCLOSURES: All authors: No reported disclosures.