SAN FRANCISCO, July 19 (Xinhua) -- An antibody-based test, developed by researchers at the University of California, Berkeley, and Humabs BioMed SA, a private biotechnology company, is able to determine if a person's infection is from the Zika virus or another virus of the same family, such as dengue and West Nile viruses.
Hailed by the researchers as the best-to-date test in differentiating Zika virus infections from infections caused by similar viruses, the new assay has very high sensitivity (91.8 percent) and specificity (95.9 percent) for identifying Zika virus infections, and is currently in the licensing process.
Assays already exist to detect Zika virus infection, a mosquito-borne disease, but they either work only shortly after infection or are poor at differentiating Zika from other flaviviruses. The limited ability of assays has led to difficulty in determining the prevalence of Zika virus infections, the incidence of congenital Zika syndrome and the frequency of neurological complications associated with Zika virus infections.
"The whole world has been in urgent need of a serological method to distinguish dengue virus from Zika virus infections, and this the first to have such high sensitivity and specificity in dengue-endemic regions," said Eva Harris, UC Berkeley professor in the Division of Infectious Diseases and Vaccinology at the School of Public Health and co-author of a paper published online this week in the journal Proceedings of the National Academy of Sciences.
The assay was developed using detailed patient samples from Harris's collaborative studies in Nicaragua, which included multiple, longitudinal samples from Zika patients, with or without prior exposure to dengue virus, and samples from dengue patients infected either once or more than once with different types of the dengue virus. Obtained from a 14-year study of a cohort of children whose previous viral infection histories were well documented, these samples were key to the research, because prior dengue virus infections can cross-react and confound many current Zika antibody-based assays.
Having a thoroughly analyzed pool of patient samples helped the researchers characterize and avoid this cross-reactivity.
Utilizing its proprietary CellClone discovery technology, Humabs generated a new human antibody to the Zika virus, which the company then used to develop the assay.
The assay is based on a well-established approach to detecting viral infections, but the new antibody and protocol give it superior sensitivity and specificity, two key assay metrics.
The assay was implemented in five countries and tested using a large number of clinical samples from travelers and patients living in areas with a high level of exposure to Zika virus and other flaviviruses. The study data indicate that when it was run on patients infected with Zika virus and also on a control group of 540 patients infected by other flaviviruses or other viruses, plus healthy donors, the specificity was 95.9 percent.
"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," Davide Corti, senior vice president and chief scientific officer of Humabs BioMed, which is based in Bellinzona, Switzerland, was quoted as saying in a news release from UC Berkeley.