Production and Molecular Characterization of Plasmodium falciparum Recombinant Circumsporozoite Protein with 37 NANP and 4 NVDP Epitopes

Abstract

Malaria is caused by the protozoan parasite Plasmodium, the leading cause of death amongst the parasitic diseases. The disease is transmitted to human by the bites of female Anopheles mosquitoes. According to the World Health Organization (WHO) data, there were an estimated 214 million malaria cases and estimated 438.000 deaths occurred worldwide, in 2015. It is observed that 90% of all the deaths due to malaria occur in Africa. 78% of these cases were children who are under five years old. Intensive malaria interventions helped to reduce malaria incidence by 37% between 2000 and 2015. Malaria is a curable disease if diagnosed and treated promptly and correctly. Drug resistance has developed against almost all anti-malarial drugs and an effective vaccine against malaria has not been developed yet. Vaccine studies initiated 40 years ago by sterile immunity against falciparum malaria through immunization by exposure to 1000 irradiated mosquitoes. Complex structures, complicated life cycles and various antigenic structures of Plasmodium species make vaccination studies difficult. Circumsporozoite protein (CSP), the most extensively studied protein is also present in the content of the vaccine candidate RTS,S which is currently closest to get license. CSP was the first described Plasmodium antigen because of its important role during initiation of the parasitic infection. CSP is the major surface coat protein of Plasmodium parasite. CSP is a soluble protein and recombinant form of the CSP can be produced in Escherichia coli. NANP repeat region is a target site for host antibodies. Recently many DNA, RNA and protein vaccine candidates are being developed against malaria. According to WHO, in the next 20 years period, malaria vaccine can be developed. In this study we aimed to produce recombinant CSP (rCSP). Initially, P.falciparum CSP gene was amplified by PCR. CSP gene was cloned in to the pJET cloning vector. The gene subcloned to the pET100 protein expression vector. E.coli cells were used for protein expression. After this process, purification and endotoxin removal protocols were performed. As a result, 1182 bp CSP gene was obtained from P.falciparum genomic DNA. Accuracy of cloning and DNA sequence of the CSP gene was determined with DNA sequence analysis. The gene sequence was recorded to the GenBank with a registration no KT315396. rCSP was expressed in E.coli cells. The existence of rCSP was verifiedwith Western Blot method and was purified and removed from endotoxins. rCSP aminoacid sequence and 3D shape was obtained.We believe that the production of recombinant CSP will enable us to contribute to the further malaria vaccine studies in our laboratory and country.