The Zika virus outbreak in Latin America has affected over 60 million people up to now. The infection can have potentially fatal consequences for pregnant women and their unborn children: many children have subsequently been born with malformations of the head (microcephaly). A particularly high incidence of these Zika-associated malformations exists in northeastern Brazil. Scientists tried to find out the reasons for this regional cluster and discovered a surprising protective factor.

A suspected cofactor

Dengue viruses, which are widespread in Latin America and cause dengue fever, were suspected cofactors. Initially, the scientists suspected that the antibodies humans produce against the dengue virus contribute to the fetal damage caused in later Zika infection. It has been known for a long time that these antibodies can enhance subsequent dengue infections under certain conditions.

However, in the case of Zika, the opposite seems to be the case. «Surprisingly, our study has shown that a previous dengue infection can protect against Zika-associated damage,» emphasizes Drexler.

The study

As a first step to investigating the interactions between dengue and Zika viruses, the genomes of all known dengue viruses in Brazil were compared to each other. This was to enable the researchers to find out whether perhaps dengue viruses in northeastern Brazil had caused different immunity compared to the immunity observed in other regions in Brazil over the last decades. In addition, the scientists conducted extensive serological tests in Salvador, Brazil: Samples from a case-control study were tested for antibodies against four different dengue serotypes. Samples from 29 mothers who had undergone Zika infection during pregnancy and gave birth to children with microcephaly were investigated. Samples from 108 mothers who also had undergone Zika infection during pregnancy but gave birth to healthy children were used as controls. In this project, scientists from the Charite — Universitatsmedizin Berlin collaborated closely with the Federal University of Bahia and the Institute of Virology of the Bonn University Medical Centre.

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Materials provided by German Center for Infection Research. Note: Content may be edited for style and length.