The Case for Exploiting Cross-Species Epitopes in Malaria Vaccine Design

Abstract

The infection dynamics between different species of Plasmodium that infect the same human host can both suppress and exacerbate disease. This could arise from inter-parasite interactions, such as competition, from immune regulation, or both. The occurrence of protective, cross-species (heterologous) immunity is an unlikely event, especially considering that strain-transcending immunity within a species is only partial despite lifelong exposure to that species. Here we review the literature in humans and animal models to identify the contexts where heterologous immunity can arise, and which antigens may be involved. From the perspective of vaccine design, understanding the mechanisms by which exposure to an antigen from one species can elicit a protective response to another species offers an alternative strategy to conventional approaches that focus on immunodominant antigens within a single species. The underlying hypothesis is that certain epitopes are conserved across evolution, in sequence or in structure, and shared in antigens from different species. Vaccines that focus on conserved epitopes may overcome the challenges posed by polymorphic immunodominant antigens; but to uncover these epitopes requires approaches that consider the evolutionary history of protein families across species. The key question for vaccinologists will be whether vaccines that express these epitopes can elicit immune responses that are functional and contribute to protection against Plasmodium parasites.

Plasmodium vivax malaria serological exposure markers: assessing the degree and implications of cross-reactivity with P. knowlesi

“…P. vivax MSP1-19 was a vaccine candidate 40 , though has not progressed to clinical trials 41 . There remains interest in this candidate 42, 43 , and the high levels of cross-reactivity in our study with P. knowlesi suggest that potential cross-species immunity could be possible 15 . Recent work has used P. knowlesi as a model for screening inhibitory activity of P. vivax antibodies 44 .…”

A T-Cell Epitope-Based Multi-Epitope Vaccine Designed Using Human HLA Specific T Cell Epitopes Induces a Near-Sterile Immunity against Experimental Visceral Leishmaniasis in Hamsters

“…This points toward the conserved nature of high-affinity epitopes across species. The hypothesis of specific epitopes, both conformational and linear, being conserved through evolution and shared in antigens from different species, have been validated by different publications [91][92][93][94].…”

A T-Cell Epitope-Based Multi-Epitope Vaccine Designed Using Human HLA Specific T Cell Epitopes Induces Sterile Immunity against Experimental Visceral Leishmaniasis in Hamsters

“…Our study further raises the question regarding epitope representation on MHC molecule, since the epitope identification done on human MHC-binding based selection, showed their ability to raise a T cellbased immunity in hamster model also, points towards the conserved nature of high-affinity epitopes across species. The hypothesis of specific epitopes, both conformational and linear, being conserved through evolution and shared in antigens from different species, have been validated by different publications [91][92][93][94].…”