The Zika virus (ZIKV) continues to loom in the international sphere of world health, and researchers are exploring potential strategies for treatment and prevention of the disease, even as they seek a better understanding of its effects on prenatal development, which include fetal microcephaly, restriction of intrauterine growth and other birth defects in both humans and mice. In response to concerns about the continuing spread and devastating consequences of ZIKV, many regulatory bodies and research groups have accelerated development of a vaccine for the virus. Now, in an 'accelerated article preview,' Nature has published a research letter from scientists of Walter Reed Army Institute of Research (Silver Spring, MD), University of São Paulo (Brazil), the Beth Israel Deaconess Medical Center (Boston, MA) and Harvard Medical School (Cambridge, MA) that describes the early fruits of this accelerated effort.

This team, led by senior author Dan Barouch, used Balb/c mice in preclinical challenge tests to assess the efficacy of two vaccines: a DNA vaccine and a purified inactivated virus vaccine ( Nature doi:10.1038/nature18952; published online 28 June 2016). The DNA vaccine works by introducing custom-designed plasmids that encode for antigens of known proteins in ZIKV; once injected, these plasmids are taken up by nearby cells, which thereafter directly express the engineered antigen and induce a corresponding immunological response. By contrast, the inactivated virus vaccine was developed by purifying ZIKV from inoculated cells and inactivating the virus with formalin; once injected, the inactivated viral particles themselves induce an immunological response without causing infection. Notably, both of these platforms have been used previously to develop vaccines for other viruses of ZIKV's genus, called flaviviruses.

When mice were infected intravenously with active viral particles, those that had received a single immunization with the DNA vaccine were completely protected against the ZIKV challenge, whereas sham-vaccinated controls showed 6 days of detectable viremia. Similarly, mice that received an intramuscular injection of the purified inactivated virus showed complete protection during a ZIKV challenge, although this vaccine was less effective when administered by subcutaneous injection.

The authors prudently note that such success in a mouse model cannot be interpreted to forecast success with humans, but this remains an indisputably positive advancement toward the development of a ZIKV vaccine. In a press release, Barouch acknowledged the encouraging results of his team's work, noting, “We hope that this news will electrify and galvanize the vaccine effort against Zika virus.”