Infection protection based on approved viral vectors-Development and research of transmission-blocking malaria vaccine

A. Construction of viral vector vaccines: Regarding viral vector A, there has been success in constructing two new types of vaccines with modified promoters in addition to the initial type. As a result of in vitro expression analysis test in mammalian cells, one of the new strains was confirmed to have stronger antigen expression from the early stage of gene introduction than the others. Three types of viral vector B have already been produced, and all of them were able to be prepared in amounts that could be used in animal experiments.

B, C. Vaccine immunity and verification of efficacy: In addition to the Balb/c mice used for conventional verification, the efficacy of the early-type vaccine was also evaluated in outbred ICR mice. In both cases of Balb/c and ICR, 90% or more protective effect was obtained against challenge infection test with recombinant murine malaria parasite. All mice that were protected from infection by the vaccine did not develop symptoms and survived. When Balb/c mice immunized with the same vaccine were forcibly infected with erythrocytic protozoa to investigate whether they could be transmitted to Anopheles mosquitoes, no oocysts were formed. On the other hand, when non-vaccinated mice were similarly sucked, an average of more than 100 oocysts were formed per mosquito. That is, the suppression rate of oocyst formation was 100%, and a strong propagation blocking effect was confirmed.

D. Immune response analysis: Both Balb/c and ICR induced more than 500,000-fold antigen-specific antibody titers 30 days after the final immunization. Long-term monitoring of the antibody titer after immunization showed that the antibody titer peaked at 1,000,000-fold or more 45 days after the final immunization, and although it gradually decreased thereafter, it was maintained at 400,000-fold or more even 210 days after the final immunization. On the other hand, in the case of the adenovirus-based conventional vaccine used as a control group, the antibody titer was about 40% of the above vaccine group at any time.

Project details

Vaccines (Immune Correlates)

Apr 2021 — Mar 2024

$34,603

Japan