PLOS Neglected Tropical Diseases, March 11, 2019

Priscila M. S. Castanha, Wayner V. Souza, Cynthia Braga, Thalia Velho Barreto de Araújo, Ricardo A. A. Ximenes, Maria de Fátima P. M. Albuquerque, Ulisses R. Montarroyos, Demócrito B. Miranda-Filho, Marli T. Cordeiro, Rafael Dhalia, Ernesto T. A. Marques Jr., Laura C. Rodrigues, Celina M. T. Martelli, Microcephaly Epidemic Research Group


Laboratory confirmation of Zika virus (ZIKV) infection during pregnancy is challenging due to cross-reactivity with dengue virus (DENV) and limited knowledge about the kinetics of anti-Zika antibody responses during pregnancy. We described ZIKV and DENV serological markers and the maternal-fetal transfer of antibodies among mothers and neonates after the ZIKV microcephaly outbreak in Northeast Brazil (2016). We included 89 microcephaly cases and 173 neonate controls at time of birth and their mothers. Microcephaly cases were defined as newborns with a particular head circumference (2 SD below the mean). Two controls without microcephaly were matched by the expected date of delivery and area of residence. We tested maternal serum for recent (ZIKV genome, IgM and IgG3 anti-NS1) and previous (ZIKV and DENV neutralizing antibodies [NAbs]) markers of infection. Multiple markers of recent or previous ZIKV and DENV infection in mothers were analyzed using principal component analysis (PCA). At delivery, 5.6% of microcephaly case mothers and 1.7% of control mothers were positive for ZIKV IgM. Positivity for ZIKV IgG3 anti-NS1 was 8.0% for case mothers and 3.5% for control mothers. ZIKV NAbs was slightly higher among mothers of cases (69.6%) than that of mothers of controls (57.2%; p = 0.054). DENV exposure was detected in 85.8% of all mothers. PCA discriminated two distinct components related to recent or previous ZIKV infection and DENV exposure. ZIKV NAbs were higher in newborns than in their corresponding mothers (p<0.001). We detected a high frequency of ZIKV exposure among mothers after the first wave of the ZIKV outbreak in Northeast Brazil. However, we found low sensitivity of the serological markers to recent infection (IgM and IgG3 anti-NS1) in perinatal samples of mothers of microcephaly cases. Since the neutralization test cannot precisely determine the time of infection, testing for ZIKV immune status should be performed as early as possible and throughout pregnancy to monitor acute Zika infection in endemic areas.

Author summary

The epicenter of the ZIKV epidemic was located in Northeast Brazil (2015/16) and was followed by a space and time cluster of congenital microcephaly cases. This region is also a dengue hyperendemic setting. Laboratory confirmation of ZIKV infection during pregnancy is challenging due to cross-reactivity with other flaviviruses, especially dengue. The neutralization test, which is the gold standard to discriminate between these viruses, is time-consuming, performed in few laboratories and does not define the time when the infection occurred. This study described the serological markers of ZIKV and DENV among participants (mothers and neonates) of a microcephaly case-control study conducted in Northeast Brazil (2016). Our results showed a strikingly high frequency of ZIKV exposure among mothers after the first wave of the ZIKV outbreak in this setting. Additionally, ZIKV and DENV immune status, as detected by the neutralization test, showed distinct patterns among pregnant women in this endemic area. We detected a low frequency of serological markers of recent ZIKV infection in samples collected just after delivery, highlighting the need for screening for ZIKV immune status in the early stage and throughout pregnancy to monitor congenital ZIKV syndrome.

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