GeoVax pushes ahead in Zika vaccine realm with promising preclinical data

A new Zika vaccine candidate by GeoVax showed promise in preclinical tests on mice, and the company believes it could become "the best solution" to the disease.

GeoVax developed a new mouse model with the CDC and scientists at the agency inoculated those mice with a lethal neuroadapted Zika virus. All mice that received a single dose of the GeoVax vaccine before the test survived, while all unvaccinated ones died within a week.

With the above data, the company now expects to initiate human trials in 18 months.

Though the preclinical data are encouraging, several other Zika vaccine candidates have also posted the same or similar results in animals. But Atlanta-based GeoVax argues that their version, dubbed GEO-ZM02, "potentially offers the best solution to safely protect at-risk populations from the Zika epidemic," GeoVax CSO Farshad Guirakhoo, Ph.D., said in a statement.

Guirakhoo’s confidence lies in the company’s modified vaccinia virus Ankara (MVA) platform, which can help produce non-infectious virus-like particles in the vaccinated subject. The process resembles a natural infection, and has shown to be safe and able to stimulate antibody and T-cell responses through previous clinical trials of an HIV vaccine, and in preclinical trials of an Ebola vaccine candidate tested in rhesus monkeys.

To Guirakhoo, the vaccine’s technology has a better safety profile. All other current Zika candidates, including inactivated, live attenuated and DNA vaccines, use the structural envelope proteins for their construct, he said, citing a study published in Science magazine last year.

The problem with that approach, said Guirakhoo, is that it has the risk of enhancing other flavivirus infections, such as dengue virus, in vaccinated subjects, a phenomenon called antibody dependent enhancement (ADE). However, the GeoVax version utilizes another protein called non-structural 1 (NS1), which hasn’t shown to be involved in ADE, according to Guirakhoo.

Besides, the nature of the NS1 protein gives the vaccine potential to block the transmission of the Zika virus in mosquitoes, Guirakhoo said, citing a Nature Microbiology article published last June.

Moreover, in this recently conducted preclinical testing, GEO-ZM02 was effective in just a single dose. That regime, if it continues to show strong efficacy on humans, could be convenient for fighting the virus in regions with limited resources.

About 40 Zika candidate vaccines are currently under development, according to the World Health Organization. Some promising shots include a DNA vaccine by Inovio and a Zika purified inactivated virus vaccine that Sanofi is working on with U.S. Army’s Walter Reed and Brazil’s vaccine research organization Fiocruz.