Evaluation of Immunodominant fragments of PfGARP for malaria vaccine development - Project Summary Malaria affects almost half the world’s population and causes more than half a million deaths annually. Children with underdeveloped immune systems in malaria-endemic areas have the highest mortality rate but no vaccine candidates are explicitly identified for this group. Global efforts to control the disease have had limited success, with no blood-stage vaccine being approved yet. However, the WHO recommends two sporozoite protein-based vaccines, RTS, S/AS01, and R21/Matrix-M, for human use but achieving broad implementation and evaluation of global efficacy remains a challenge. Therefore, there is an urgent unmet need to discover new vaccine candidates or improve the efficacy of known antigens to develop a new generation of malaria vaccines for children. Previous studies in our lab identified a novel vaccine candidate, PfGARP, using phase display screening of malaria-resistant children's serum and P. falciparum T7 Phage-based cDNA library. Our work has culminated in the discovery of Pf Glutamic Acid Rich Protein A (PfGARP-A) and a comprehensive, full-length Research Article in Raj et al. Nature, 2020. During the screening phase of our approach, we identified antigens from C- terminus regions of PfGARP overlapping with each other and interacting only with the antibodies from the plasma of malaria-resistant children. The above findings indicate that the lower molecular weight recombinant PfGARP (rPfGARP) antigens might have the crucial domain for functional antibodies and can generate growth inhibition activity comparable to PfGARP-A. In our preliminary approach, we immunized the mice (n=5/antigen) with DNA vaccine using the smaller fragments of the immunodominant regions as PfGARP-B, PfGARP-C, PfGARP-D, and a 324 bp N-terminus fragment of PfGARP (PfGARP-E as negative control) and harvested polyclonal serum. Our preliminary data demonstrate that polyclonal serum generated against PfGARP-B and PfGARP-C in mice specifically interacts with P. falciparum in western blot, flow cytometry, Immunofluroscent microscopy, and shows significant parasite-killing activity in growth inhibition assay (GIA) comparable to PfGARP-A. The study aims to develop human- usable recombinant protein and LNP-mRNA-based platforms for PfGARP-B & C antigens using in vitro assays and humanized murine model (in vivo) against P. falciparum, the deadly human malaria parasite. These studies will form the core supporting data for further development of the lower molecular weight rPfGARP antigens, which could help reduce the production cost and make it easier to use with other blood stage proteins as fusion antigens with the ultimate goal of an efficacious malaria vaccine for humans that has better efficacy against children.
