Two Zika vaccines effectively passed Zika immunity from a vaccinated mother to newborn mice, thereby successfully protecting them from neurological defects associated with the virus, according to a research paper published in EBioMedicine.
One of the vaccines was delivered using a microneedle array, which is essentially a small patch affixed to the skin that delivers the vaccine through tiny dissolving crystals. The other vaccine was delivered via traditional needle delivery and used an adenovirus, or common cold, to present Zika to the immune system. Both vaccines were designed to use proteins on the outer shell of the virus to create an antigen and incite a reaction from the body's immune system.
For the study, three groups of five female mice were either administered one of the two vaccines or given a saline solution placebo. Two weeks after the initial vaccination, mice were given a booster shot of whatever vaccine they'd received. Blood samples were extracted and tested at two week intervals from the date of initial immunization forward. Mice vaccinated with the traditional needle vaccine displayed immunity after two weeks. Mice treated with the microneedle array experienced immunity after six weeks.
Five weeks after immunization, the vaccinated female mice mated with unvaccinated males. Additionally, because mice do not experience the birth defect microcephaly, the newborn mice were all exposed to the Zika virus one week after birth. All of the pups from mothers immunized with adenovirus Zika vaccine and 50 percent of the pups from the mothers who were administered the microneedle array vaccine survived infection. Only 12.5 percent of the newborn mice from mothers in the saline solution control group survived. All mice pups in the control group displayed signs of neurological damage. Five of six pups born to females in the microneedle array cohort also experienced neurological damage, though it was less severe than those experienced among the placebo control group.
While none of the adenovirus vaccine pups experienced neurological defects, that particular vaccine is less likely to be successful in people because the vast majority of humanity has had an adenovirus cold, which would prohibit the vaccine from developing effective Zika antibodies.
"We decided to move forward with the microneedle array Zika vaccine and have since developed a promising, second-generation vaccine," said the study's senior author Andrea Gambotto, MD, associate professor of surgery at the University of Pittsburgh School of Medicine. "We are hopeful, now that Congress has approved the $1.1 billion bill to provide funding for Zika prevention and research, that we'll be able to do larger-scale studies to evaluate and develop this vaccine for possible human clinical trials in the future."
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