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Study indicates the need to revise the protocol for detecting Zika in placenta

Publicado em 20 maio 2020

Study indicates the need to revise the protocol for detecting Zika in placenta  Science Codex

Shortly after the explosion in microcephaly cases caused by Zika virus in Brazil in 2015-16, several scientific studies were published with evidence that the pathogen is capable of crossing the human placenta, the organ that keeps the fetus connected to the mother's body during pregnancy. From then on, the states began following a protocol established by the National Ministry of Health requiring collection of placental samples to help diagnose the disease in women with symptoms during pregnancy.

However, according to a group of Brazilian researchers at the University of Campinas (UNICAMP) who have studied emerging viruses with São Paulo Research Foundation - FAPESP's support, the official protocol in place nationwide should be reformulated. As they recently reported in Frontiers in Microbiology, it is crucial to ensure that samples are representative and properly stored and transported to obtain trustworthy results in detecting the virus in the placenta.

The report concludes that Zika virus can indeed infect different regions of the placenta in pregnant women, such as the umbilical cord, amniotic membrane, chorionic plate, chorionic villi and basal plate.

This discovery suggests that diagnostic tests should take several placental regions into consideration to assure adequate representativeness and more accurate results. "The protocol currently in force says each sample should be 1 cubic centimeter in size but doesn't specify the placental regions to be analyzed," said molecular biologist José Luiz Proença Módena, who heads the Emerging Virus Research Laboratory (LEVE) at UNICAMP's Institute of Biology and is one of the authors of the report.

The study analyzed 17 placental samples from women who gave birth at the Women's Hospital (CAISM) run by UNICAMP. Fourteen tested positive for Zika virus using a real-time PCR kit developed by the researchers. The PCR method detects RNA from the virus in the samples tested.

"We collected four fragments from all placental regions for each patient, including the umbilical cord," Módena said. The women had symptoms of the disease during pregnancy, such as fever and rash, or delivered babies with microcephaly in 2016 or 2017. According to Módena, the collection of several placental fragments increases the chances of detecting Zika because some regions of the placenta contain more viruses than others.

The researchers were surprised to find that placental samples from the same patients tested negative when analyzed using the health ministry's protocol by the Adolfo Lutz Institute (IAL), the main reference laboratory for epidemiological surveillance in the state of São Paulo. "This problem highlights the urgency of changing the currently required method," Módena said.

In response to inquiries by Agência FAPESP, IAL's press office stated that placental samples continue to be tested in compliance with the official protocol, and there are no plans to change this procedure at the moment. For Módena, the urgent need to increase laboratory testing to detect the novel coronavirus…