Relevância da validação de um ensaio Sorológico usado para diagnóstico diferencial de Zika vírus

Abstract

The Zika Virus (ZIKV) outbreak is no longer a public health emergency in Brazil, but the sequels of the first event will still resonate over a long period. The main clinical symptoms are: macular or maculopapular rash with pruritus, headache, arthralgia, myalgia, prostration, non-purulent conjunctivitis, and may or may not be associated with low fever. There are several social and economic impacts due to the 2015 ZIKV outbreak in Brazil, such as microcephaly and Guillain-Barrè syndrome. GBS is an inflammatory neurological complication that can happen after ZIKV infection, usually diagnosed by the symptoms presented by the patient, such as weakness in the muscles, loss of sensation in the extremities and decreased reflexes. DENV and ZIKV are RNA virus closely related. They share at least 41% similarity in the amino acid sequence of protein E, the first to be recognized by the body during infection. The main cross reaction that can occur in infections by DENV and ZIKV is Antibody-Dependent Enhancement (ADE). This phenomenon can cause severe infection, bringing even lethal consequences, as in the case of Dengue Hemorrhagic Fever, in the DENV infection. The differentiation between ZIKV and DENV, made only by clinical diagnosis is not reliable. Laboratory diagnosis is essential for this differentiation, especially in cases of convalescence stage of the disease. Cross reactions with other Flaviviruses are common, due to the genetic similarity between viruses. Real-time PCR is performed during the acute phase of the disease, restricted to a period of 3 to 5 days. Serological tests are performed both in the acute phase (IgM type antibodies) and in the convalescence phase (IgG type antibodies). The development of an ELISA kit is done in three stages: Development, Optimization and Validation. The validation phase checks the kit's performance for sensitivity, specificity and accuracy. This study aims to establish the differentiation of the Zika virus diagnosis, by structuring an immunoenzymatic assay, ELISA methodology, for the detection of IgG class antibodies. Most ELISA tests are imported from other countries, since Brazil does not produce them domestically or have lower quality than imported products. This means lower cost for laboratories and higher quality for national products. The kit's Linearity and Accuracy has been proven. The Analytical Sensitivity of the kit was 97.8% adjusted. The Analytical Specificity was 100%. There was no cross reaction with anti-DENV antibodies in any of the samples analyzed.