Research Article: From genomic to LC-MS/MS evidence: Analysis of PfEMP1 in Benin malaria cases

Date Published: June 28, 2019

Publisher: Public Library of Science

Author(s): Claire Kamaliddin, David Rombaut, Emilie Guillochon, Jade Royo, Sem Ezinmegnon, Gino Agbota, Stéphanie Huguet, Sayeh Guemouri, Céline Peirera, Romain Coppée, Cédric Broussard, Jules M. Alao, Agnès Aubouy, François Guillonneau, Philippe Deloron, Gwladys I. Bertin, Takafumi Tsuboi.

http://doi.org/10.1371/journal.pone.0218012

Abstract

PfEMP1 is the major protein from parasitic origin involved in the pathophysiology of severe malaria, and PfEMP1 domain subtypes are associated with the infection outcome. In addition, PfEMP1 variability is endless and current publicly available protein repositories do not reflect the high diversity of the sequences of PfEMP1 proteins. The identification of PfEMP1 protein sequences expressed with samples remains challenging. The aim of our study is to identify the different PfEMP1 proteins variants expressed within patient samples, and therefore identify PfEMP1 proteins domains expressed by patients presenting uncomplicated malaria or severe malaria in malaria endemic setting in Cotonou, Benin.

We performed a multi-omic approach to decipher PfEMP1 expression at the patient’s level in different clinical settings. Using a combination of whole genome sequencing approach and RNA sequencing, we were able to identify new PfEMP1 sequences and created a new custom protein database. This database was used for protein identification in mass spectrometry analysis.

The differential expression analysis of RNAsequencing data shows an increased expression of the var domains transcripts DBLα1.7, DBLα1.1, DBLα2 and DBLβ12 in samples from patients suffering from Cerebral Malaria compared to Uncomplicated Malaria. Our approach allowed us to attribute PfEMP1 sequences to each sample and identify new peptides associated to PfEMP1 proteins in mass spectrometry.

We highlighted the diversity of the PfEMP1 sequences from field sample compared to reference sequences repositories and confirmed the validity of our approach. These findings should contribute to further vaccine development strategies based on PfEMP1 proteins.

Partial Text

Through its asexual development in human erythrocytes, Plasmodium falciparum grows and reshapes its host cell. Parasite proteins exported at the host cell surface mediate infected erythrocyte’s adhesion to the host’s endothelium that leads to hypoxia, occlusion and endothelial activation. In cerebral malaria (CM) pathophysiology, the sequestration of infected erythrocytes (iE) in the brain capillaries is believed to trigger coma and brain swelling [1].

The evolution of P. falciparum infection from uncomplicated forms of the disease to cerebral malaria, the most fatal, is a complex phenomenon [44]. There are strong evidences that the PfEMP1 proteins are involved in the disease progression since they allow the parasite to bind to host endothelium [10]. It is believed that a distinct subset of PfEMP1 proteins is involved in severe malaria [23,45], most likely by providing to the parasite the ability to sequester to a given receptor. However, PfEMP1 identification in natural infection remained challenging, due to the large size of PfEMP1 and their high sequences diversity. Recently, Jespersen et al [23] provided a new insight towards var genes sequences expression analysis in patient’s sample using transcript reconstruction after DBLα barcoding. They confirmed the preferential expression of CIDRα associated with EPCR binding in severe malaria patients. In addition, Tonkin Hill et al performed a de novo reconstruction of var genes from patient’s isolates [28].

 

Source:

http://doi.org/10.1371/journal.pone.0218012