Poster Presentation 8th Australasian Vaccines & Immunotherapeutics Development Meeting 2020

 Effective targets of cross-species protective immunity against malaria identified by proteome-wide screening (#202)

Denise Doolan 1 , Mengistu Sedi 1 , Carla Proietti 1 , Daniel Browne 1 , Claire Loiseau 1 , David Pattinson 1
  1. Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia

Vaccines against many diseases caused by complex pathogens are still not available despite intense research. The genome, proteome and transcriptome of a number of these challenging pathogens have been now elucidated, and provide the foundation for systematic genome-based approaches to identify target antigens for rational vaccine design. Using malaria as a model complex pathogen, we have developed and applied a strategy using T cell epitope prediction algorithms in reverse to identify and prioritize from the complete Plasmodium falciparum parasite proteome the subset of key antigens targeted by T cell responses from individuals with clinical immunity to malaria. We have also pursued proteome-wide screening using protein microarrays and sera from malaria-immune individuals to identify antigens targeted by antibody responses. Integrating our proteome-wide datasets showed that antigens preferentially recognized by T cells are distinct from antibody targets, suggesting that different vaccine approaches and antigen targets are required depending on whether antibodies or T cells are the desired vaccination outcome. Specific genomic, structural or physiochemical attributes could distinguish T cell versus antibody targets, facilitating the development of a predictive algorithm for immune class. Fourteen of the most highly ranked P. falciparum T cell antigens were evaluated for immunogenicity and capacity to protect against stringent cross-species P. yoelii parasite challenge in mice. Three immunization regimens were explored: homologous DNA-DNA, heterologous DNA-Adenovirus, and an innovative prime-target regimen designed to induce sustained T cell responses in the liver. Many of our novel P. falciparum antigens were effective targets of cross-species protective immunity, as evidenced by sterile infection-blocking immunity, reduction in liver-stage and blood-stage parasite burden or delay to onset of parasitemia. We have down-selected for clinical development a subset of antigens with maximum likelihood of inducing strain-transcending and cross-species protective immunity against malaria in humans. Such a rationally-designed genome-based vaccine would be expected to protect against all strains and all species of malaria.