DNA Vaccine Candidates For Zika Found Safe

Zika DNA vaccines found to be immunogenic, but the greatest effects were seen given in split doses via needle-free injection

pregnant women, looking at sky

The Zika virus is challenging the scientific community to produce a vaccine that addresses this 70-year-old pathogen.

Although symptoms of Zika virus infection are typically mild, infection during pregnancy is now associated with microcephaly, a life-long condition impacting children.

The development of Zika vaccines is ongoing by several organizations but remain in the clinical trial process.

In a recent study, two DNA vaccines candidates were found to be safe, with most adverse events being mild.

DNA vaccines are safe and immunogenic for many pathogens, including flaviviruses like Zika, although none has been licensed for use in human beings, according to research published in The Lancet.

Both of these DNA vaccines were found to be immunogenic, but the greatest effects were seen with candidate VRC5283, given in split doses via needle-free injection.

Multiple studies have shown that needle-free injectors augment DNA vaccine response, possibly by increased dispersion of injectate or through tissue disruption that increases immunogenicity.

The clinical trial VRC5283 deployed needle-free delivery, and produced 6 times higher response, than a single-dose delivery, via needle and syringe.

One hundred percent (100%) of participants who received the vaccine by needle-free injection in split doses had detectable antibody responses, produced neutralizing antibodies, and had the highest T-cell responses.

The VRC5283 vaccine candidate has advanced to phase 2 efficacy testing.

"We are pleased that the PharmaJet device boosted immunogenicity in this Zika virus vaccine clinical trial and we look forward to participating in the next stage of development," said Ron Lowy, CEO, PharmaJet Inc, said in a press release. 

The established manufacturing technologies, previous data on toxicity and safety, inherent DNA stability, and ability to elicit antibody and CD8 T-cell responses make DNA vaccines an attractive option for rapidly responding to emerging infectious diseases.

Previously unknown sequelae of Zika virus infection, most notably congenital abnormalities, served as the impetus for accelerated vaccine development. The Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA, has experience in developing vaccines to protect against emerging infectious diseases, in general, especially against flaviviruses.

These clinical trials are registered with ClinicalTrials.gov, numbers NCT02840487 and NCT02996461.

These researchers did not declare any conflicts of interest: MRG is the principal investigator of VRC 319. GLC is the principle investigator of VRC 320. CSH, LAH, SE, MAM, NGR, KEL, GEC, and BSG were study investigators. ZH did the statistical analysis. GY, RSR, NB, IJG, JHC, SS, CL, RMS, JRM, BSG, TCP, JEL, and GLC designed the clinical trials. MRG, FM, JGS, LN, CSH, LAH, IJG, SE, MAM, NGR, KEL, and GEC collected data. MRG, KVH, KMM, JHC, RTB, BMF, KB, RSP, DNG, CRD, KAD, JRM, BSG, TCP, JEL, and GLC analysed and interpreted the data. All authors contributed to the writing of the report and approved the final version.