Construction, Expression, and Evaluation of the Naturally Acquired Humoral Immune Response against Plasmodium vivax RMC-1, a Multistage Chimeric Protein

Abstract

The PvCelTOS, PvCyRPA, and Pvs25 proteins play important roles during the three stages of the P. vivax lifecycle. In this study, we designed and expressed a P. vivax recombinant modular chimeric protein (PvRMC-1) composed of the main antigenic regions of these vaccine candidates. After structure modelling by prediction, the chimeric protein was expressed, and the antigenicity was assessed by IgM and IgG (total and subclass) ELISA in 301 naturally exposed individuals from the Brazilian Amazon. The recombinant protein was recognized by IgG (54%) and IgM (40%) antibodies in the studied individuals, confirming the natural immunogenicity of the epitopes that composed PvRMC-1 as its maintenance in the chimeric structure. Among responders, a predominant cytophilic response mediated by IgG1 (70%) and IgG3 (69%) was observed. IgM levels were inversely correlated with age and time of residence in endemic areas (p < 0.01). By contrast, the IgG and IgM reactivity indexes were positively correlated with each other, and both were inversely correlated with the time of the last malaria episode. Conclusions: The study demonstrates that PvRMC-1 was successfully expressed and targeted by natural antibodies, providing important insights into the construction of a multistage chimeric recombinant protein and the use of naturally acquired antibodies to validate the construction.

Immunogenicity of PvCyRPA, PvCelTOS and Pvs25 chimeric recombinant protein of Plasmodium vivax in murine model

“…This research tackles three key challenges: 1) Finding better ways to assess vaccine potential before expensive clinical trials, which is due to P. vivax’s inability to grow long-term in the lab makes traditional methods even more difficult; 2) Identifying new vaccine targets/novel proteins that could trigger a protective immune response and; 3) improving existing vaccine candidates to maximize their effectiveness. In this scenario, we recently designed a chimeric protein called PvRMC-1, combining conserved epitopes of three known P. vivax proteins (PvCyRPA, PvCelTOS, and Pvs25) that were recognized by the immune system of naturally exposed individuals ( 13 ). Given that the epitope selection, construct design, recombinant expression, and structural identity were conducted in this previous work, here we aimed to evaluate the immunogenicity of PvRMC-1 formulated in different adjuvants using non-humanized murine models, complementing and validating this chimeric protein as a potential vaccine candidate.…”

“…PvRMC-1 design, topology, and successful expression in Escherichia coli were described earlier ( 13 ). Briefly, the chimeric recombinant protein was designed with four T-cell epitopes and two B-cell epitopes from PvCelTOS, two linear B-cell epitopes from Pvs25, and a 255 amino acid sequence containing both B- and T-cell epitopes of PvCyRPA, encompassing the entire protein.…”

“…Given the complexity of the Plasmodium spp. life cycle, the optimal vaccine design should address all stages ( 13 , 14 ). The prevailing belief is that a vaccine capable of inducing immunogenic responses across multiple stages of parasite development would provide superior protection.…”

“…Recently, we designed and expressed a P. vivax recombinant modular chimeric protein (PvRMC-1) composed of the main antigenic regions of these vaccine candidates ( 13 ). The protein was successfully expressed and the predicted structure retained the stage-specific epitopes.…”

“…Moreover, in addition to the antigenicity confirmation by IgG and IgM antibody recognition, the PvRMC-1 seroprevalence in a population naturally exposed to malaria revealed a high frequency of total antibody responders, predominantly displaying cytophilic IgG1. Indeed recent infected individuals presented higher antibody response, suggesting the potential of this antigen as a successful immunogen ( 13 ). However, conclusive insights into the immunogenicity of PvRMC-1 will not be achieved without immunization studies in animal models.…”