An article by Maha A Elbadry
Four years after the first whistle blow of microcephaly associated with Zika virus infections and science is still scratching its metaphoric head trying to figure out how zika virus works. Though reports of outbreaks have receded since the epidemic of the Americas in 2014-2016, the threat it poses on pregnant women -being an endemic virus- remains severely high. The challenge with zika is that majority of infections are asymptomatic, it is difficult to identify if women living in endemic areas are infected or not, since 80% of the cases will not show any signs of illness.
The ZIKAction consortium is making a strong effort to study the effect of asymptomatic zika virus infections in pregnant women and health outcomes on their babies. Since roughly 80% of all infections do not produce symptoms, it is very difficult to detect infection using molecular diagnostic methods. The best approach would be to flip the coin and look for antibody response in patients. If antibodies for zika virus is detected, then evidence of exposure can be confirmed. Antibody response can even differentiate between very recent infection (within 7-15) days post infection, to relatively recent infection (6-9 months) post infection, depending on the type of antibodies being targeted.
Though this seems like a golden solution to the problem of zika detection, particularly when randomly applied to high risk population such as pregnant women, the assays remain challenging. Zika virus belongs to a family of viruses (Flaviviridae) that share some commonality in their proteins, one can think of zika, dengue and West Nile virus as relatives or first-degree cousins. Such similarity in the virus genetic structure makes the immune response to them occasionally non-specific. For years now, since the Americas outbreak in 2016, different laboratories around the world are tirelessly working to design the perfect assay that will detect the right antibody for zika and does not cause cross reaction with any of its virus relatives.
The Emerging Pathogens Institute (EPI) at University of Florida (UF) has joined this race by providing valuable input on the quality of the available assays by comparing two newly established serological assay to detect zika previous exposure. EPI/UF have a well-defined cohort population that they are working with in Haiti under the umbrella of the ZIKAction Consortium. A team of nurses under the supervision of Mr. Rigan Louis are following pregnant women in two local Haitian maternity clinic/hospital, collecting blood samples every trimester to look for presence of antibodies for zika virus. Now that proper samples from highly endemic area such as Haiti is being properly collected and available, a team of scientists from UF did an extensive search for newly developed assays to detect immune response to zika virus. The EPI/UF team have visited Nicaragua, Brazil and Hamburg, where three of the best available assays that are still under validation have been developed and tested. The UF team will be using their cohort specimens from Haiti to compare the assays side by side, in addition to running a more comprehensive – yet hard to commercialize- laboratory test in an attempt to answer the big question, are any of those assays good enough to be recommended for zika diagnosis.
Maha A Elbadry is a Postdoctoral Associate at the Emerging Pathogens Institute (EPI) at the University of Florida (UF).
