The role of natural killer cells and antibodies in protection from malaria

Project Summary / Abstract Malaria causes large numbers of deaths per year including 200,000 miscarriages due to placental malaria. We lack an effective malaria vaccine partially because we do not fully understand the mechanism of antibody mediated protection. Antibodies are predominantly thought to be effective through blocking mechanisms. However, we hypothesize that protective antibodies in Plasmodium infection bind infected RBC surface proteins for recognition and killing by natural killer (NK) cells. We have data showing that NK cells inhibit the growth of Plasmodium in vitro through antibody dependent cellular cytotoxicity (ADCC). We went on to show that a subset of NK cells, γ neg NK cells, have enhanced ADCC function and abundance of γ neg NK cells correlates with reduced parasitemia and protection from malaria in a large endemic malaria cohort. This proposal aims to understand how these γ neg NK cells increase function and abundance in the context of malaria infection. We will test the CD16 cascade with CRISPR/Cas9 ablations to understand why γ neg NK cells have enhanced ADCC function. We will use CRISPR/Cas9 to ablate effector and adhesion molecules to understand how NK cells inhibit the growth of Plasmodium. We will also test the underlying mechanism of malaria exposure that drives the increase in γ neg NK cells and test if γ neg NK cells expand with ADCC and malarial cytokine signals. We also aim to define NK cell ADCC protective mechanisms against the placental malaria target Var2CSA. Var2CSA is a protein on the surface of the infected RBC that adheres to the placenta and can cause miscarriages. We will test if antibodies that are good at generating NK cell ADCC responses increase with Var2CSA exposure and correlate with protective pregnancy outcomes in human and monkey samples. We will also test previously identified and novel monoclonal antibodies for NK cell ADCC function and dissect the features that generate a strong NK ADCC response. These aims in total will create a body of work that will contribute to the development of better vaccines and therapeutics for malaria. This would change vaccine targets to be proteins on the surface of infected RBCs instead of invasion proteins, predictive efficacy readouts would include NK cell ADCC assays, and antibodies developed here may be future immune therapies.