Antibody-based assay from Humabs BioMed SA and UC Berkeley differentiates Zika virus infections from other diseases caused by flaviviruses.

Epidemiologists have known about the Zika virus since 1947 when it was discovered in monkeys in Uganda. Aedes mosquitoes transmit the Zika virus, as well as the dengue fever, yellow fever, and chikungunya viruses. Outbreaks were limited to Africa until 2007, but the Zika virus has since spread to the Americas and Asia-Pacific, according to the World Health Organization. One of the chief concerns about the Zika virus is its ability to be transmitted to unborn fetuses, which often suffer from birth defects.

The Zika virus is a flavivirus, as is the dengue virus. One of the challenges to accurately determining the number of Zika infections, the incidence of congenital Zika syndrome in babies born to infected women and the types of neurological complications associated with Zika virus infections, has been the cross reactivity among flaviviruses and their co-circulation. While there are assays to detect the Zika virus, they generally are effective during a short period of time and have minimal capability of differentiating the virus from other flaviviruses.

Swiss biopharmaceutical company Humabs BioMed SA has developed an antibody-based assay referred to as NS1 blockade-of-binding (BOB) ELISA that has been shown to overcome these challenges. The ability of the assay to differentiate Zika virus infections from other flaviviruses, such as dengue, was demonstrated by researchers at the University of California, Berkeley led by Professor Eva Harris and in cooperation with laboratories in Nicaragua, Brazil, Italy, the UK and Switzerland.

The key to the successful evaluation was access to well-characterized, time-matched samples taken from Zika patients with or without prior exposure to dengue virus and samples from dengue patients infected once, or more than once, with different dengue virus serotypes. The patients and travelers who provided the samples either lived in or traveled to areas known to have both high levels of Zika virus present and be endemic for other flaviviruses.

The NS1 BOB ELISA assay was developed using Humabs’ proprietary CellClone discovery technology. The company generated a ZIKV nonstructural protein 1(NS1)-specific human monoclonal antibody for the assay, which measures the presence of plasma or serum antibodies in immune individuals that are able to block the binding of a labeled monoclonal antibody to coated Zika virus NS1.

"These results support that the antibody-based assay that we have developed is highly effective in detecting both recent and past Zika virus infections and in discriminating Zika from other flavivirus infections,” said Dr. Davide Corti, Chief Scientific Officer of Humabs BioMed. “This novel assay has the potential to become an effective, simple and low-cost solution for Zika surveillance program, prevalence studies and clinical intervention trials in flavivirus-endemic areas."

Added Professor Harris, Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley: "It is very exciting to finally have a robust, high-throughput assay with such high sensitivity and specificity to distinguish Zika virus infections in dengue-endemic countries; we have already applied it to large age-stratified serosurveys and spatial analysis of Zika virus infection in Nicaragua, advancing scientific research while providing critical data to public health authorities in real time."