Malaria is a major human health problem and is responsible for over 2 million 
deaths per year. It is caused by a number of species of the genus Plasmodium, 
and Plasmodium falciparum is the causative agent of the most lethal form. 
Consequently, the development of a vaccine against this parasite is a priority. 
There are a number of stages of the parasite life cycle that are being targeted 
for the development of vaccines. Important candidate antigens include proteins 
on the surface of the asexual merozoite stage, the form that invades the host 
erythrocyte. The development of methods to manipulate the genome of Plasmodium 
species has enabled the construction of gain-of-function and loss-of-function 
mutants and provided new strategies to analyse the role of parasite proteins. 
This has provided new information on the role of merozoite antigens in 
erythrocyte invasion and also allows new approaches to address their potential 
as vaccine candidates.