Cloning, Sequence Analysis, and Expression of CIDR1α-PfEMP1 from Indonesian Plasmodium Falciparum Isolate

Abstract

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is an antigenic protein which is expressed in the erythrocytic phase of P. falciparum life cycle and plays an essential role in severe malaria pathogenesis. It is encoded by the var gene family and consists of cysteine-rich interdomain region (CIDR) and Duffy-binding-like (DBL) domains. This research aimed to clone, analyze, and express the CIDR1α-PfEMP1 from Indonesian P. falciparum isolate. The specific CIDR1α domain was amplified from malaria patients. The amplicon was ligated into pET-30a and transformed into Escherichia coli BL21(DE3). Sequencing result of plasmid clones confirmed 100% homology with the sequence of the CIDR1α domain. BLAST analysis showed that the sequence had high similarity to Plasmodium sp. gorilla clade G1 from Africa and P. falciparum isolate from Tanzania, East Africa. Translation using ExPASy Translate Tool resulted in a truncated protein consisting of 99 amino acids. Western blot analysis using anti-His-6-tag antibody showed that the recombinant protein was a 17.5 kDa fusion protein and clearly expressed as a soluble protein when induced with 0.1 mM isopropylthio-β-galactoside (IPTG) for ≥8 hours at room temperature. As much as 45.4% of amino acids showed 100% homology with other human-infecting P. falciparum isolates. The sequence was predicted to have B-cell epitope based on immune epitope database. In conclusion, Indonesian CIDR1α-PfEMP1 isolate had high similarity to primate and human-infecting Plasmodium spp. isolates. The recombinant protein was expressed as a fusion protein. Its structure prediction showed that the sequences have B-cell epitope, implicating its potency in inducing antibodies. Further studies should be established to develop its potency as a vaccine candidate.