Ciencia Brasil , São Paulo, Viernes, 11 de marzo de 2016 a las 09:21

Researchers create method to detect zika virus in transfusion blood

The São Paulo blood bank will use a test developed with support from FAPESP to screen blood for use in pregnant women and intrauterine transfusions

AGÊNCIA FAPESP/DICYT A method of detecting the presence of zika virus in blood used for transfusions has been developed as part of a project supported by FAPESP and coordinated by José Eduardo Levi, head of the Department of Molecular Biology at São Paulo’s blood bank, Fundação Pró-Sangue, linked to the São Paulo State Department of Health and the University of São Paulo’s Medical School (FM-USP) in Brazil.

 

According to Levi, the methodology will initially be indicated only for screening of blood used in transfusions for pregnant women and in intrauterine transfusions, in which blood is transfused directly into the fetus. The initiative is a precautionary measure because it has not yet been confirmed that transmission of the virus via transfusion is hazardous to unborn babies.

 

“Protecting pregnant women and fetuses is the top priority as far as zika is concerned,” he said. “It evidently wouldn’t be a good idea to use blood that just might carry the virus in these cases, so we decided to develop a test for use on the very few blood bags that are allocated to these two groups. In fact, they correspond to only 0.16% of the blood bank’s entire inventory.”

 

Since the start of the zika epidemic in Brazil in 2015, the blood bank of the University of Campinas (UNICAMP) in São Paulo State has confirmed two cases of transmission by blood transfusion.

 

Dengue virus is known to be transmissible by transfusion. According to Levi, during epidemic peak periods, approximately 1% of blood donors are estimated to be positive for dengue virus, but laboratory screening tests are not performed on blood bags.

 

“This has never been considered a problem, since most of the time the person who receives the transfusion doesn’t develop the disease,” he said. “No severe cases of transfusional dengue have ever been detected in Brazil. This first recipient contaminated with zika in Campinas didn’t display any symptoms of the disease, although the presence of zika virus in his blood was confirmed.” The second patient died from gun wounds that led to the need for a transfusion.

 

“Generally speaking,” Levi continued, “there’s no evidence as yet that zika is a problem from the standpoint of transfusion, except for pregnant women. For example, we don’t know if zika acquired via transfusion can cause microcephaly, although we believe it’s highly likely.”

 

Levi is also a professor at the University of São Paulo’s Tropical Medicine Institute (IMT-USP) and a member of the Zika Network, set up on an emergency basis in December 2015 and headed by Paolo Zanotto, a professor at the same university’s Biomedical Science Institute (ICB-USP). The network’s remit is to address issues relating to the zika epidemic and the growing number of associated microcephaly cases.

 

“A FAPESP-supported project dedicated to preventing transfusional transmission of malaria in São Paulo State was already under way. In December, we applied for additional funding, which was used to develop the zika virus detection test,” Levi said.

 

The methodology combines real-time polymerase chain reaction (PCR), a molecular biology technique, with assay protocols developed by the US Centers for Disease Control & Prevention (CDC) to detect zika virus.

 

“The CDC’s protocols recommend specific reagents, primers and probes that have already been tested and approved for zika virus detection using real-time PCR. We’ve made a few adaptations to the protocols here at the São Paulo blood bank,” Levi said.

 

The methodology was validated with positive controls isolated from laboratory-grown viruses used to confirm that it did indeed detect zika virus. The controls were supplied by researchers belonging to the Zika Network.

 

“After that, we also validated it in plasma from the recipient contaminated by transfusion, kindly supplied by Dr. Marcelo Addas from UNICAMP’s blood bank. This was successful, and we’ve now distributed the method to everyone in the Zika Network. They’re free to use it as deemed appropriate,” Levi said.

 

Given the lack of evidence regarding the importance of screening all donated blood for the presence of zika virus, Levi indicated that it would not be possible or necessary to include the test in the routines of all Brazilian blood banks.

 

“We’re closely watching the evolution of the epidemic,” he said. “If evidence is found that this is necessary, we’ll strenuously pursue more resources, but for now we believe it’s prudent to screen only these two small groups.”