Scientists at the National Institute of Allergy and Infectious Diseases have been working on a new HIV vaccine, which has showed promise in initial studies with mice and monkeys. Their results show that the novel vaccine was safe and promoted the desired antibody and cellular immune responses against a HIV-like virus (an extremely similar virus).
For the study the researchers first tested the mRNA vaccine on mice, with results showing that after two injections, neutralizing antibodies were produced. With successful initial results, researchers then moved onto testing in macaques monkeys. First they primed the immune system with a vaccine modified to optimise antibody creation, following with multiple booster inoculations delivered over the course of a year.
The vaccine delivers coded instructions for making two of the key HIV proteins, known as ‘Env’ and ‘Gag’. The researchers used multiple variants of the virus to activate antibodies against the more commonly shared regions of the ‘Env’ protein, rather than covering the more variable different regions, that change with each virus strain.
Results showed that the vaccine was well tolerated in the macaques monkeys, even at higher dosage levels. At week 58, all the vaccinated monkeys had developed neutralising antibodies against 12 diverse HIV strains. Side effects were mild and temporary, with the most common side effect being loss of appetite.
At week 60, the researchers then exposed the monkeys on a weekly basis to SHIV (in simple the monkey adapted version of the virus). Findings revealed that monkeys who had taken thirteen weekly inoculations, two of seven remained uninfected, whilst other immunised monkeys had a delay of infection by an average of eight weeks. However, for the unimmunised monkeys, they became infected at around the three week mark.
"We are now refining our vaccine protocol to improve the quality and quantity of the VLPs produced. This may further increase vaccine efficacy and thus lower the number of prime and boost inoculations needed to produce a robust immune response. If confirmed safe and effective, we plan to conduct a Phase 1 trial of this vaccine platform in healthy adult volunteers," said Dr. Lusso
After careful analysis of the data gathered, the scientists concluded that overall, the monkeys who received a priming vaccine followed by multiple booster vaccinations had a 79% lower per-exposure risk to the virus, in comparison to unvaccinated candidates. With promising initial results, researchers hope to continue their work in further trials to create a highly effective vaccine for the future.