T Cell-Based Vaccines: Hope for Malaria Elimination

Abstract

Among the numerous infectious diseases, malaria still remains the main cause of morbidity and mortality across the world. Every year more than 200 million cases are registered and death toll is of around 4,00,000. The emergence of insecticide and drug resistance has surged an alarming situation to find an effective means to tackle it. From various approaches used for reducing the damage created by malaria to the society, developing effective vaccine has gained the attention of scientific community. The large genome size (24 MB), heterogeneity of the genes, complex life cycle in two different hosts, and expression of wide range of these genes are claimed to hinder the malaria vaccine development. It requires good understanding of the host-pathogen interaction and its correlation with the sterile protection. Recently, subunit vaccine have shown certain promising responses; however, the currently in use of RTS,S vaccine has failed to generate the long-term sterile protection as well as effector memory CD8+T cells. However, the success of sterile protection through vaccination has been proven long back by experimental approaches, where it could be achieved using irradiated sporozoites (RAS) in rodents and humans. Similarly, GAP (genetically attenuated parasite) and CPS (chloroquine chemoprophylaxis with Plasmodium sporozoites) have been shown to induce sterile immunity. Despite all the developments, generation of species and stage specific-CD8+ T cell responses has been modest. In order to generate long-lasting immune response, particularly, liver-stage specific-CD8+ T cells, it is indeed required to study the CD8+ T cell epitope repertoire and its implications on the host immune system. In this chapter we will discuss the current status of T cell-based vaccines and the challenges associated with it.