Antigen discovery team (DISCOVERY)

(for a list of the members of this research team, click here)

The work of the DISCOVERY team focuses on identifying which types of the parasite proteins PfEMP1 and RIFINs can be associated with severe malaria disease in children and considered for vaccine development.

About one million African children die from malaria every year. The severity of malaria infections in part depend on which type of the parasitic protein PfEMP1 is expressed on the surface of the infected red blood cells. The protein mediates binding to human receptors on the vascular lining allowing parasites to sequester in the peripheral circulation. Thereby parasites avoid passage through the spleen, where they would be destroyed. Natural immunity to malaria is mediated through antibodies to PfEMP1. Even though it takes years of exposure to develop an immunity that protects against non severe febrile malaria, protection against severe malaria and malaria deaths is acquired after a few infections. This implies that parasites causing severe malaria syndromes express a limited set of semi-conserved PfEMP1s and that it is feasible to make a vaccine based on these molecules if they can be identified. Therefore hopes for a malaria vaccine based on PfEMP1 proteins have been raised. 

PfEMP1 are large proteins comprised of an extracellular polymorphic part and a conserved intracellular part. Each parasite genome contains about 60 PfEMP encoding var genes. However, the large global sequence variation among PfEMP1 molecules has caused great difficulties in executing and interpreting studies on PfEMP1.

The work of the discovery group can be organised into following topics.

Understanding the sequence variation of P. falciparum variant gene families var/PfEMP1 and rif/RIFINs

To define which PfEMP1 types are associated with severe disease in children, evidently it is important to understand how to classify var/PfEMP1 sequences. Thus, in order to understand the global variation of PfEMP1 types, state of the art as well as customized bioinformatic analysis tools are being applied to describe the variant gene families of P. falciparum. See var/PfEMP1 sequence analysis database here.

Identifying var/PfEMP1 variants associated with severe malaria disease – PfEMP1 antibody acquisition in malaria endemic populations.

Based on the sequence variation analysis described above we have aimed to produce recombinant proteins covering all PfEMP1 types in order to test which part or type of PfEMP1, natural acquired immunity is directed towards. Currently, proteins are expressed in the Baculo virus expression system and antibody levels in immune individuals are tested to these proteins in a flow based multiplex Luminex system.

Identifying var/PfEMP1 variants associated with severe malaria disease – var expression in patient isolates.

The var/PfEMP1 expression by parasites collected from malaria patients are investigated using QPCR primers specific to different types of PfEMP1 and by next generation sequencing technologies. Also, surface expression of proteins is tested using antibodies generated from recombinant PfEMP1 proteins. 

Model parasite lines

Model parasite lines expressing relevant PfEMP1 types are generated in vitro and their human endothelial cell adhesion phenotype investigated. Using these parasite lines and adhesion assays, antibodies to different PfEMP1 protein constructs can be tested in order to define good vaccine constructs.

Master students with a natural science background can carry out their project with the DISCOVERY team. The team also train technicians. The methods we use include:

Bioinformatics, Real-time RT-PCR, FLX-454 and Solexa sequencing, Flow cytometry,  Confocal imaging,  genetic engineering,  Protein expression, Protein purification, Binding inhibition assays, Biosensor assays, Multiplex analysis (Luminex), animal immunizations, culturing and manipulations of malaria parasites and field work in Tanzania. For additional details regarding methodologies, please click here.

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For general information about the DISCOVERY team, please contact Thomas Lavstsen