NS1 DNA Vaccination Found Protective Against Zika

Researchers at the University of Adelaide in Australia announced they created a novel DNA vaccine candidate that can neutralize the Zika virus in mice.

This pre-clinical study published on December 11, 2019, showed the importance of using NS1 as a target for protective T cell-based Zika virus (ZIKV) vaccines.

This is important early research since there is no licensed vaccine available to protect people against a Zika infection.

This study evaluated 3 different ZIKV NS1 DNA vaccine candidates using an immunocompetent mouse model. 

The researchers injected the DNA vaccine into the ears of young albino mice. Each mouse received 3-doses of the vaccine over the course of several weeks. 

By the end of the study, the DNA vaccine had generated a strong immune response that helped protect the mice against the Zika virus.

These researchers demonstrated that effective secretion of NS1 is critical for immunogenicity, showing that NS1 alone can confer protection against systemic ZIKV infection and that this protection is T cell-mediated. 

The importance of this mice study is it ‘bridges a major gap in the understanding of how ZIKV NS1 vaccine regulates CMI responses and protection in an immunocompetent host.

But based on these results, researchers are one step closer to finding a way to protect the global population from the Zika virus.

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A recent study in naïve IFNAR−/− mice challenged with ZIKV demonstrated that CD4+ T cells are required for protection against a lethal ZIKV challenge in this model.

However, human CD4+ T cell response to ZIKV was shown to target epitopes in both structural and nonstructural proteins, with the most ID epitopes located in E, NS1, and NS5.

The Zika virus is a flavivirus generally transmitted to humans via the bite of infected Aedes aegypti mosquitoes. 

Human-to-human transmission of ZIKV has been established, with ZIKV being the only known arbovirus that is transmitted sexually with persistence in the reproductive tissues of both males and females for prolonged periods of time.

Historically, ZIKV infections were considered asymptomatic and self-limiting and were associated with the development of Guillain-Barré syndrome in adults, which can result in paralysis.

The explosive spread of ZIKV in the Americas from 2015 to 2016 was causally associated with serious birth defects in infants born to mothers infected during pregnancy, including microcephaly and a range of neurological abnormalities and birth defects termed congenital Zika syndrome.

In a recent NEJM editorial published on October 9, 2019, researchers said ‘We're in a quiet phase with Zika, but it will strike again.’

‘Since the Zika epidemic of 2015 and 2016 sickened thousands of people in the Americas, researchers have attempted to answer key questions about this harmful flavivirus.’

‘Although the effect of sexual transmission in areas in which the virus is endemic is difficult to assess, estimates are that 1 percent of ZIKV infections reported in Europe and the United States were acquired through sexual transmission.’

ZIKV RNA has been detected in semen, by reverse-transcriptase–polymerase-chain-reaction assay, up to 370 days after onset of illness.

And the maternal-fetal transmission of ZIKV may occur in all trimesters of pregnancy, whether infection in the mother is symptomatic or asymptomatic. 

Vertical transmission has been estimated to occur in 26 percent of fetuses of ZIKV-infected mothers in French Guiana, a percentage similar to transmission percentages that have been observed for other congenital infections.

In addition, 45 percent of the fetuses that were exposed to ZIKV by vertical transmission had no signs or symptoms of congenital Zika syndrome in the first week of life.

A study involving pregnant women from Rio de Janeiro, Brazil, used a broader definition for ZIKV-associated outcomes and identified adverse outcomes in 42 percent of fetuses and infants exposed to the virus.

Although ZIKV infection in any trimester of pregnancy may cause congenital Zika syndrome, the risk is greatest with infections occurring in the first trimester.

Neonatal mortality in the first week of life among infants with congenital Zika syndrome may be as high as 4 to 7 percent.

This finding underscores the need for long-term surveillance of children born to mothers with ZIKV infection.

The full spectrum and risk of congenital Zika syndrome, therefore, remain incompletely delineated, concluded this NEJM editorial. 

Zika virus vaccine news published by Zika News.