A test that detects antibodies to Zika virus in samples of high specificity blood serum ̵
The method was developed by Brazilian scientists. The technology company Inovatech developed the test in collaboration with scientists from the Biomedical Institute of the University of São Paulo (ICB-USP) and the Research Foundation São Paulo (FAPESP) The Butantan Institute
"We are in the final stages of developing a serological test to detect immunoglobulin G (IgG) antibodies that remain in the organism for many years after infection, ensuring lifelong immunity, and we expect it to be approved for sale in the second half of this year, "said Danielle Bruna Leal de Oliveira, researcher at the ICB USP Clinical and Molecular Virology Laboratory and Project Leader.
Since the establishment of the Zika Virus Research Network in 2016 In São Paulo (Speech Zika), which is supported by FAPESP, the development of this type of diagnostic method has been considered a priority.
A tool of this kind, the scientists say, is essential for answering several strategic questions for any action plan against the disease: what is the exact size of the epidemic (more specifically, between the cases of dengue and Zika, both current and ongoing) previous outbreaks)? What share of pregnant women is infected (and thus immune)? How many women risk the birth of babies with neurological problems due to a congenital infection?
"The idea is to include this test in the prenatal investigation process," Oliveira said. "If we can, pregnant women with a negative result [meaning they have never been infected] will take more precautions, such as avoiding travel to high-risk areas and using insect repellent." Meanwhile, those who are immune can stop worrying do." 19659005] According to Oliveira, currently available diagnostic tests either work only in the acute phase of infection – as is the case with the molecular method (real-time PCR) and chromatography, which detect viral RNA in the blood – or with Zika antibodies demonstrate low specificity.
"The specificity of the serological tests currently on the market is in the 69% -75% range, so there is a 25% probability of a false positive finding if the patient has been infected with dengue virus in the past "The specificity of our test is 93% for Zika," said Oliveira.
The test developed by Inovatech, like its predecessor, is based on a method known as ELISA, an acronym for enzyme-linked immunosorbent adsorption Microtiter plate with 96 tiny wells attached to a human immune system recognized viral protein.
The wells are filled with blood serum of up to 94 patients, with two or more reserved for controls IgG are liable in case of previous contact with Zika Antibodies to the viral protein, which is later detected by a colorimetric assay (positive and negative samples get different colors).
"One of the difficulties associated with the method is that the commonly used viral protein NS1 is very similar in all flaviviruses [the family Flaviridae includes dengue, Zika and yellow fever, among others] .To solve this problem, we used a revised version of the protein, wherein we selected only the Zika-specific part of the molecule, "explained Oliveira. This "shortened" version of NS1 (δNS1) was developed by Luis Carlos de Souza Ferreira and his team of ICB-USP.
To further reduce the risk of cross-fertilization with dengue viruses, Inovatech researchers added another step to the test. Before the blood serum of patients in contact with δNS1 is brought into the ELISA plate, it is exposed to the proteins of dengue virus to extract all antibodies against this pathogen from the samples.
"The downside is that it takes a bit longer to get a result – about three hours, compared to two hours and twenty minutes for conventional ELISA – but we're working on a way to make it faster with it the goal that it should be faster than the standard method "
Selected in a Call for Proposals (in Portuguese), which in 2016 under an agreement between FAPESP and FINEP The Oliveira-coordinated project, the Brazilian Innovation Agency, aims to develop a rapid, cost-effective serological test for the detection of IgG and IgM (immunoglobulin M) that remains in the organism up to about four months after the end of the infection  "We focused on IgG in 2017, and this year we are focusing on developing a method of detection from IgM, "said Oliveira.
Her group is supported by ICB USP researchers Edison Luiz Durigon and Luiz Carlos Ferreira, as well as researchers from Roxane Piazza and Viviane Botosso from the Butantan Institute.
Although the time needed to achieve a result needs to be further reduced, the cost-effective part of the project goal has been achieved. Oliveira estimates the cost of detecting IgG to be around BRL 10-12 per patient (now about $ 3.00-3.70).
Inovatech has also taken another important step in bringing its product to market: It has obtained a Manufacturing Best Practice (BPF) certificate from ANVISA, the National Health Inspectorate. The first approaches for experimental use are already being prepared.
New test expands window for accurate detection of Zika