Abstract
Vaccine trials and cohort studies in Plasmodium falciparum endemic areas indicate that naturally-acquired and vaccine-induced antibodies to merozoite surface protein 2 (MSP2) are associated with resistance to malaria. These data indicate that PfMSP2 has significant potential as a component of a multi-antigen malaria vaccine. To overcome challenges encountered with subunit malaria vaccines, we established that the use of highly immunogenic rPfMSP8 as a carrier protein for leading vaccine candidates rPfMSP119 and rPfs25 facilitated antigen production, minimized antigenic competition and enhanced induction of functional antibodies. We applied this strategy to optimize a rPfMSP2 (3D7)-based subunit vaccine by producing unfused rPfMSP2 or chimeric rPfMSP2/8 in Escherichia coli. rPfMSP2 formed fibrils, which induced splenocyte proliferation in an antigen receptor-independent, TLR2-dependent manner. However, fusion to rPfMSP8 prevented rPfMSP2 amyloid-like fibril formation. Immunization of rabbits elicited high-titer anti-PfMSP2 antibodies that recognized rPfMSP2 of the 3D7 and FC27 alleles, as well as native PfMSP2. Competition assays revealed a difference in the specificity of antibodies induced by the two rPfMSP2-based vaccines, with evidence of epitope masking by rPfMSP2-associated fibrils. Rabbit anti-PfMSP2/8 was superior to rPfMSP2-elicited antibody at opsonizing P. falciparum merozoites for phagocytosis. These data establish rPfMSP8 as an effective carrier for a PfMSP2-based subunit malaria vaccine.
Highlights
Throughout the past several years, great progress has been made towards the goal of malaria elimination and eventual eradication with the widespread implementation of a number of control strategies[1]
The mature coding sequence of the 3D7 allele of the pfmsp[2] gene was codon harmonized for expression in E. coli using previously established algorithms[45]
The codon harmonized synthetic gene was directionally subcloned into the pET28-MCS-PfMSP8(CΔS) expression vector to facilitate production of two recombinant PfMSP2-based antigens: an unfused rPfMSP2 antigen (25 kDa) and a chimeric rPfMSP2/8 antigen (68 kDa, Fig. 1A)
Summary
Throughout the past several years, great progress has been made towards the goal of malaria elimination and eventual eradication with the widespread implementation of a number of control strategies[1]. Data from the most recent World Malaria Report indicate that the preceding decline in clinical cases of malaria and malaria-related deaths is beginning to level off in most regions and is even showing signs of reversal in others These data are concerning and are likely a result of increases in drug-resistant parasites and insecticide-resistant mosquitoes, along with the challenge of sustaining multiple control programs in endemic areas[1]. Through genetic fusion of the blood-stage vaccine candidate, PfMSP119, to the N-terminus of the conserved, highly immunogenic PfMSP8, we were able to produce high yields of chimeric rPfMSP1/8 antigen with properly folded EGF-like domains. This chimeric antigen approach prevented antigenic competition and the vaccine elicited high-titer antibodies specific for conformation-dependent, protective epitopes of PfMSP11916. The success with chimeric rPfMSP1/8 and rPfs25/8 vaccines with respect to production, folding, immunogenicity and induction of functional antibodies, prompted us to evaluate PfMSP8 as a fusion partner for another leading blood-stage vaccine candidate, P. falciparum MSP2
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
