Thermostable, Oral Zika Vaccine Candidate Produced Positive Study Results

The journal ScienceDirect recently published results from an early-stage, innovative Zika virus vaccine candidate, OraPro-Zika.

On April 6, 2023, this study addressed several challenging features attributed to vaccinology.

First, developing a thermostable vaccine negates the need for a "cold chain." And second, the potential to deliver the vaccine orally.

Having demonstrated that iosBio's OraPro-Zika vaccine provided a measurable efficacy in the murine models, they performed a challenge study in NHP to investigate the potential clinical utility.

In this setting, enteric-coated capsules were given orally, negating the need for stomach acid neutralization.

Upon vaccination, a significant rise in anti-Zika IgG was evident after the first dose concordant with our murine model.

Furthermore, the level of IgG was similar to that in convalescent serum from NHP previously infected with the Zika virus.

Most strikingly, in challenge studies, convalescent and OraPro-Zika vaccinated animals showed no evidence of replicative Zika virus. In contrast, the placebo-vaccinated cohort showed full-blown infection, which modeled the disease pathology as it was rectified by day 8 of the study.

While we hypothesize the immune protection in our model systems is potential via a mucosal root, our study is limited and does not define cellular mechanisms or sIgA.

Nonetheless, IgG and challenge studies remain the gold standard for vaccine efficacy.

In summary, these researchers showed that an orally administered Ad5- vaccine encoding genes for the Zika envelope (Env) and NS1 proteins induced a specific immune response that reduced Zika infection in both murine and NHP models and remained thermally stable for over 109 days at 25 °C.

This preliminary study with OraPro-Zika suggests oral administration of a non-replicating adenovirus vector protects against challenge and warrants further investigation to establish a mode of action.

These authors declared various industry relationships, and Innovate UK supported the study.

Updated May 10, 2023 - Reassigned domain.