Like twins who look almost identical save for subtle distinguishing features, viruses belonging to the same genus can be difficult to tell apart. For instance, the Zika virus, which surfaced as a global public health threat in 2016, belongs to the Flaviviridae family and is very similar to dengue virus and yellow fever virus.
One method used to diagnose virus infections is serology, which detects antibodies against a specific virus in infected patients’ specimens. However, flavivirus infections are notoriously known to elicit antibodies that are cross-reactive towards the different flavivirus subtypes, thus hindering the development of Zika virus diagnostic tools.
Now, scientists led by Lisa F.P. Ng at the Singapore Immunology Network (SIgN) have identified Zika virus-specific epitopes—short protein sequences on the Zika virus to which antibodies bind—to increase the accuracy of serological testing for the virus. The research was carried out in collaboration with colleagues at the University of Campinas, Brazil, the country at the epicenter of the 2016 pandemic.
“We obtained serum samples from Zika virus- and dengue virus-infected patients and screened them against Zika, dengue and yellow fever virus peptide libraries,” Ng said. This screening process revealed four peptides (ZIKV E peptide 27, ZIKV E peptide 29, ZIKV NS1 peptide 86 and ZIKV NS1 peptide 117) that are specifically recognized by antibodies in Zika virus-infected patient samples from Brazil but not antibodies in dengue-virus infected ones.
Of the four epitopes, one was bound only by antibodies found in the sera of pregnant women. “This is an important finding as it shows the effect of pregnancy on the immune response and epitope-antibody recognition,” Ng noted. The mechanism of why and how pregnant women produce a separate, unique antibody response to the Zika virus remains unknown.
Beyond facilitating the development of diagnostic tools, the identification of Zika virus-specific epitopes could lead to vaccines against the Zika virus. Given the neurological complications and congenital abnormalities known to be associated with Zika virus infection, a vaccine against the disease is urgently needed. “It would be of interest to test the protective efficacy of the epitopes as vaccines in pre-clinical models,” Ng added.
The A*STAR-affiliated researchers contributing to this research are from the Singapore Immunology Network (SIgN).