The Zika vaccine demonstrates its effectiveness in preventing the virus

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A breakthrough Zika vaccine has been proven to effectively prevent the Zika virus in preclinical animal studies.

The new Zika vaccine was developed at the Walter Reed Institute of Research (WRAIR), in collaboration with the Trudeau Institute and the Texas Biomedical Research Institute’s Southwest National Primate Research Center (SNPRC). In their research, the Zika vaccine prevented the virus from spreading from mother to fetus.

In-Jeong Kim, PhD, viral immunologist at the Trudeau Institute and first author of the paper, said: “The vaccine has been shown to be safe for non-pregnant humans, but of course we need to know if it is safe and effective for those most at risk: pregnant women and their fetuses. Our proof-of-concept studies conducted at Trudeau and Texas Biomed show very promising results that the vaccine given before pregnancy will provide high levels of protection for mothers and babies.

The results of the study are published in the journal npj Vaccines.

Fight against epidemics

Brazil and several other South American countries were devastated by the Zika virus epidemic of 2015-2016, leading to a wave of miscarriages and congenital disabilities – called congenital Zika syndrome, including abnormally small heads and disorders of neurological development. This led the World Health Organization (WHO) to declare the Zika outbreak a public emergency threat of international concern.

Jean Patterson, PhD, virologist at Texas Biomed and lead author of the paper, commented, “It is important to test vaccines before the next big outbreak because there will be another one. Zika is part of a family of viruses known to go through cycles. These viruses tend to spread rapidly in naïve populations that have never been exposed to the virus before; then the infections go down for years because most people have been exposed. As more and more people are born, there is a new group of naïve individuals in whom the virus can once again wreak havoc. We want to help break this cycle.

Zika vaccine development

The team developed their purified and inactivated Zika vaccine (ZPIV) using the same technology used to make a Japanese encephalitis vaccine, and it has been shown to effectively clear the virus from blood in non-human animals. pregnant. Additionally, it has been shown to be safe and elicit a protective immune response in Phase 1 human trials.

However, for ethical and safety reasons, the team could not perform rigorous testing to prove that the Zika vaccine protects pregnant women and their fetuses from infections and serious malformations. Nevertheless, the researchers evaluated the vaccine in pregnant mice and marmosets, where it prevented 80% of fetal malformations, and antibodies capable of neutralizing the virus were detected in fetal blood samples eight days after infection.

“We were able to detect maternal antibodies in the fetus during pregnancy, and the results suggest that antibodies play a critical role in protecting fetuses against Zika virus,” Kim said.

Marmosets are more susceptible to the Zika virus than other non-human primates, with previous investigations showing that fetuses were aborted within two weeks of maternal infection. In contrast, in the study, four marmosets received the Zika vaccine before becoming pregnant and then were exposed to the Zika virus, with only one of their 12 offspring testing positive, showing over 90% efficacy.

Patterson said: “Because the animals became pregnant at different times, our study was able to show that the vaccine confers protection for at least 18 months after vaccination, which is important for showing long-lasting immunity.”

The team is now looking to investigate what happens when the Zika vaccine is given during pregnancy in marmosets.

Kayvon Modjarrad, MD, PhD, who directs the U.S. military’s Zika vaccine program and is the director of emerging infectious diseases at WRAIR, said, “These studies add to the evidence that the Zika vaccine developed by WRAIR not only protects animals against Zika virus infection. , but also birth defects that mimic what has been seen in humans. Together with early phase clinical trials, we believe these data provide further confirmation that this vaccine platform is a viable approach to countering the lingering threat of Zika.

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Sara H. Byrd