Immunity to liver-stage malaria

Malaria, caused by Plasmodium species, is an unresolved global health burden. Although insecticide treated bed nets and antimalarial drugs have reduced the incidence and severity of malaria in some regions, >200,000,000 cases still occur annually with >400,000 fatalities, most of which occur in young children in sub-Saharan Africa. Thus, effective vaccines remain an as yet unrealized but critical goal to combat the global threat of malaria. However, development of potent and translatable vaccines against malaria has been hampered by the incomplete understanding of the mechanisms by which the immune system can be trained to control Plasmodium infections. CD8 T cell immunity to liver-stage (LS) malaria has been studied for for ~13 years. During this time, study of the immunity against whole parasite immunizations (RAS and late-arresting GAP) and studied epitope-specific prime-boost immunization strategies that were capable of generating sterilizing immunity to sporozoite challenge in mice. A major finding from the latter studies was that sterilizing immunity occurred when the immunization generated circulating malaria-specific memory CD8 T cells (hereon called Tcircm) that exceeded a large, but definable frequency.

Large numbers of epitope-specific CD8 T cells were found to be present in the livers of immunized mice. In contrast, studies from different groups showed that sterilizing RAS immunization generated relatively small Tcircm responses, although these responses were enriched in the liver. This apparent conundrum was recently explained by the discovery that RAS immunization generates a very potent liver CD8 T resident memory population (from here, called liver Trm) that is essential for sterilizing immunity in this vaccination model. Trm, occupy many tissues and play important roles in tissue specific immunity. These findings have galvanized the malaria field to focus on novel immunization strategies to generate Trm to improve LS vaccines. While the importance of liver Trm in RAS vaccine induced protection from Plasmodium cannot be overstated, it remains unclear to what degree, if any, Tcircm contribute to protection against LS infection. Here, in unpublished preliminary data, evidence is provided that Tcircm can indeed provide protective immunity against LS Plasmodium infection using an as yet undefined mechanism for rapid recruitment to the liver. The project will address these goals with the following Specific Aims: SA 1. Determine the mechanisms underlying rapid recruitment of Tcircm to the liver SA 2. Dissect the mechanisms of liver-stage protection by Tcircm SA 3. Determine if and how Tcircm cooperate with Trm in control of liver-stage malaria

Project details

Vaccines (Immune Correlates)

Jan 2022 — Dec 2026

$1.12M

United States