Research Themes

Main Research Themes

• Developmental biology and genetics of malaria parasites
• Identification and analysis of drug and vaccine target proteins
• Analysis of parasite-host(cell) interactions
• Generation and analysis of genetically attenuated parasites

Research areas

In the Leiden malaria Research Group a rodent malaria parasite (Plasmodium berghei) is used as a research model for human malaria infections. Rodent malaria parasites are practical model organisms for the experimental study of human malaria. These parasites have proved to be analogous to the malarias of man and other primates in most essential aspects of structure, physiology and life cycle. Our research interests and areas of expertise are:

• Technologies for the genetic modification of malaria parasites (developmental biology and functional analysis of target-proteins)
• Genome organisation and chromosome size polymorphism (genome plasticity, comparative genomics)
• Biology of RNA metabolism and post-transcriptional control of gene expression
• Post-genomic technologies to identify and validate new drug and vaccine targets (microarrays, proteomics)
• Biology of host-parasite and vector-parasite interactions
• Generation and analysis of genetically attenuated parasites
• Anti-malarial drug testing

The Plasmodium berghei rodent model

A malaria parasite of rodents, Plasmodium berghei, is used as the research model in our laboratory. This model has been developed into a sophisticated and functional system for molecular and cellular studies. It is recognised as a valuable model in view of:

• The high similarity between human malaria parasites and P. berghei (for example in genome organisation, the genetic make-up, the molecular basis of drug-sensitivity and in vaccine target proteins
• The simple and safe manipulation of the complete lifecycle
• In vitro cultures for production and manipulation of the parasites
• The availability of the genome sequence, transcriptome and proteome databases and technologies for genetic modification
• The availability of (genetically modified) mutant parasites including parasite lines expressing reporter genes such as GFP and Luciferase
• The availability of rodent hosts with characterised genetic backgrounds including transgenic lines.

P. berghei and genetic modification

The P. berghei-research model has significantly contributed to the introduction and application of advanced molecular techniques in malaria research. A major breakthrough was the development of technologies for the genetic modification of malaria parasites that has been pioneered in Leiden. These technologies open an entirely new range of methods for the investigation of developmental biology of malaria parasites and functional analysis of proteins that are targets for vaccines and new drugs.
In our laboratory a number of mutant, transgenic lines of P. berghei have been made through targeted disruption of genes and through introduction of reporter genes such as Green Fluorescence Protein and Luciferase. Most of these lines are available on request (see also research model).

P. berghei: genomics and post-genomics research

The increasing availability of genome sequence information of different malaria parasites has revealed the similarity between the genomes of human malaria parasites and rodent malaria parasites. Therefore we can use the knowledge of the genome of the rodent parasite P. berghei in a gene discovery program to discover and characterize new vaccine candidates and drug targets.
Detailed transcriptome analysis of various developmental stages (distinct time-points during asexual and sexual development in blood) of the P. berghei have been conducted using microarray chips. Differential transcription profiles have been generated and are available here. Proteome analysis studies have been performed in collaboration with Prof. Matthias Mann (Odense, Denmark) and Dr. Edwin lasonder (Nijmegen, The Netherlands), on uniquely acquired life cycle stages (i.e. separated male and female mature P. berghei gametocytes, purified merozoites of different species of Plasmodium; sporozoites). This analysis has been performed using Liquid Chromatography Tandem Mass Spectrometry (LC-MSMS) and the resulting spectra analysed using the MASCOT algorithm. Proteomes generated from different samples have informed targeted gene disruption studies aimed at looking at function of proteins at different points of parasite development; lists of proteins identified by this analysis  can be found here.

P. berghei: Identification and analysis of targets for vaccines and drugs

The P. berghei research model and the development of methods for genetic modification of P. berghei enables the functional analysis of vaccine candidate antigens and investigation of parameters involved in the effective presentation of these antigens so that protective immune responses may be elicited. Several surface proteins that are seen as major vaccine candidate antigens are under investigation at the gene and protein level in our laboratory. 

P. berghei: Anti-malarial drug testing

The P. berghei research model has been optimised for testing new anti-malarial drugs. It is one of the few malaria models available in which anti-malarial efficacy and stage-specific activity can be directly assessed in vitro and compared with the in vivo activity.