Successful Zika Virus Vaccine on Monkeys Gives Hope

The Zika virus is — as far as we know so far — symptomless to the carrier. Its real impact comes when the infection from a pregnant woman is transferred to her foetus leading to severe brain damage and birth defects. It’s spread by mosquitos and there has been no breakthrough in medication or — possibly more importantly — a vaccination for the virus. But with the World Health Organisation saying that the Zika epidemic is a public health emergency there may be hope according to an article published in the journal Science.

Monkey vaccines

Researchers have discovered three vaccines that achieved complete protection against the Zika virus when tested in monkeys. One of the vaccines actually protected the monkeys from two strains of the infection — one from Brazil and one from Puerto Rico — while the other two vaccines were tested against a Brazilian strain.

The rhesus monkeys have been used for testing because they are the “best model we have”, according to Dr. Dan Barouch, of Beth Israel Deaconess Medical Centre. Non-human primates give the most accurate indication of whether the vaccine will be effective on humans. Consequently, when the primate trials are successful, it gives “substantial optimism moving into human trials”, says Barouch.

PIV vs DNA

Other than being tested on two strains, what sets the first vaccine apart is that it’s made from a purified and inactivated form of the virus (PIV). While the other vaccines are crafted from DNA, the PIV vaccine is made by growing the virus in a controlled, laboratory environment, before killing it and purifying it. It’s a tried and tested method, according to researchers at the Walter Reed Army Institute of Research, which is more likely “to go the distance”.

The US Government and US Pharmaceutical firm, Inovio have begun human safety trials for two of the DNA-based vaccines. However, a DNA-based vaccine has never been licensed for use in humans before — while testing for the PIV vaccine on humans will begin in October.

Vector-borne vs blood-borne

Like many other viruses, Zika is vector-borne — in this instance it is transmitted by infected arthropod species. Other viruses, like HIV and hepatitis B, are blood-borne. They are spread through contamination by blood and other bodily fluids.

The team used affinity chromatography to separate immunoglobulin G (IgG) from the plasma of monkeys vaccinated with the PIV vaccine. IgG is a type of antibody — in fact it is the most common type of antibody found in humans. The separation of immunoglobulin from plasma using affinity chromatography is discussed in the article, CaptureSMB for Efficient Affinity Purification of Monoclonal Antibodies.

The IgG was then infused into mice and monkeys which were then exposed to Zika virus. The team found that some of the mice and monkeys — those receiving a higher vaccine dose — were protected from Zika virus. As the virus slowly spreads from South America — with cases being reported in Europe and the US — this is timely news indeed.