Scientists Using Cloned Zika to Find a Vaccine

(CN) — Federal researchers have cloned an epidemic strain of the Zika virus, giving biologists a way to test vaccines and strategies to stop the pandemic.

In a study published Tuesday in the journal mBio, researchers at the National Institutes of Health detailed their attempts to clone a strain of the virus. The cloned virus replicated successfully in multiple cell lines, including brain and placenta cells, which are particularly vulnerable to damage stemming from Zika.

"Our goal is to create long-term immunity after one short immunization," study leader Alexander Pletnev said.

Pletnev's group wants to create a live, unnaturally thin vaccine similar to the ones used in humans to fight viruses like yellow fever, polio and Japanese encephalitis.

After completing their lab studies, the team recently began studying the cloned virus using mice. Pletnev invited other researchers to use his lab's Zika clone to investigate — and ultimately stop — the harm caused by the mosquito-borne virus.

Zika was initially identified in Uganda nearly 70 years ago, but only became a widespread issue after nations in the Caribbean and Latin America began experiencing active local transmission in early 2015.

In February 2016, the World Health Organization declared the pandemic a public health emergency. The U.S. Centers for Disease Control and Prevention reported the first case of local transmission within the continental U.S. in Wynwood, a neighborhood in North Miami.

The virus can also be transmitted through sexual contact.

Viruses are often unpredictable, which makes it challenging for scientists to determine how to stop them.

Zika is a flavivirus, a group of viruses that also includes yellow fever, dengue and West Nile. While flaviviruses each have a single strand of RNA, they're difficult to manipulate and clone.

Using the tools of reverse genetics, biologists can study single-stranded RNA by using viral complementary DNA, or cDNA.

Pletnev's team has worked on other flaviviruses, including a vaccine for West Nile virus that is currently in clinical trials, and has worked on developing vaccines for different strains of encephalitis.

Pressure continues to mount in the search for a reliable Zika vaccine, as scientists continue to uncover evidence of Zika's connection to different congenital disorders.

In a special report also published Tuesday, researchers presented the spectrum of imaging findings in babies and fetuses infected with Zika, which detailed pre- and postnatal brain defects from the virus.

"Microcephaly is just one of several radiological features," said the report's lead author, Fernanda Tovar-Moll.

Zika appears to be most dangerous when transmitted from a pregnant mother to her fetus during the first trimester of pregnancy, increasing the likelihood of severe fetal brain defects in like microcephaly — a congenital disorder that also leads to an abnormally small head, due to an underdeveloped brain.

"The first trimester is the time where infection seems to be riskiest for the pregnancy," said study co-author Deborah Levine. "From an imaging standpoint, the abnormalities in the brain are very severe when compared to other congenital infections."

While the media have primarily focused on microcephaly, the team noted that there is a variety of brain abnormalities that can be found in fetuses exposed to the virus, including brain stem abnormalities, calcifications, and a condition called ventriculomegaly where fluid-filled spaces in the brain are enlarged.

Some babies infected with Zika may not have a small head size if the ventricles remain excessively enlarged, according to the team's report.

Levine's team performed a retrospective review of imaging and autopsy findings associated with congenital Zika infections found in northeastern Brazil, where the infection rate has been particularly high.

Between June 2015 and May 2016, 438 patients in Brazil were referred to the Instituto de Pesquisa in Campina Grande state Paraiba due to rash during pregnancy or suspected central nervous system abnormalities.

Of this group, the researchers identified 17 fetuses or newborns of women who had imaging at the institute, as well as documented Zika infection in fluid or tissue, and 28 fetuses or newborns with brain findings suspicious for Zika infection with intracranial calcifications.

Ninety percent of the confirmed Zika group and 79 percent of the presumed Zika group had abnormalities of the corpus callosum — a large nerve fiber bundle that enables communication between the left and right hemispheres of the brain.

All but one had cortical migrational abnormalities, which means the neurons did not travel to their appropriate destination in the brain.

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