Vaccine Containing the Three Allelic Variants of the Plasmodium vivax Circumsporozoite Antigen Induces Protection in Mice after Challenge with a Transgenic Rodent Malaria Parasite

Abstract

Plasmodium vivax is the most common species that cause malaria outside of the African continent. The development of an efficacious vaccine would contribute greatly to control malaria. Recently, using bacterial and adenoviral recombinant proteins based on the P. vivax circumsporozoite protein (CSP), we demonstrated the possibility of eliciting strong antibody-mediated immune responses to each of the three allelic forms of P. vivax CSP (PvCSP). In the present study, recombinant proteins representing the PvCSP alleles (VK210, VK247, and P. vivax-like), as well as a hybrid polypeptide, named PvCSP-All epitopes, were generated. This hybrid containing the conserved C-terminal of the PvCSP and the three variant repeat domains in tandem were successfully produced in the yeast Pichia pastoris. After purification and biochemical characterization, they were used for the experimental immunization of C57BL/6 mice in a vaccine formulation containing the adjuvant Poly(I:C). Immunization with a recombinant protein expressing all three different allelic forms in fusion elicited high IgG antibody titers reacting with all three different allelic variants of PvCSP. The antibodies targeted both the C-terminal and repeat domains of PvCSP and recognized the native protein on the surface of P. vivax sporozoites. More importantly, mice that received the vaccine formulation were protected after challenge with chimeric Plasmodium berghei sporozoites expressing CSP repeats of P. vivax sporozoites (Pb/PvVK210). Our results suggest that it is possible to elicit protective immunity against one of the most common PvCSP alleles using soluble recombinant proteins expressed by P. pastoris. These recombinant proteins are promising candidates for clinical trials aiming to develop a multiallele vaccine against P. vivax malaria.

Protective Malaria Vaccine in Mice Based on the Plasmodium vivax Circumsporozoite Protein Fused with the Mumps Nucleocapsid Protein

“…When challenged with a transgenic parasite (Pb/PvVK210), 4/6 mice demonstrated protective immune responses. In comparison to the controls, the immunized group displayed a 20-fold reduction in the liver parasite burden [22].…”

“…The gene sequences encoding recombinant PvCSP proteins NLP-CSP CT and NLP-CSP R were synthesized using codon optimization for expression in P. pastoris (GenScript, Piscataway, NJ, USA). Both proteins contained the three variant tandem repeats domains of PvCSP [22] fused with the mumps virus nucleocapsid protein (UniProtKB/Swiss-Prot: AFO62160) sequence. The NLP-CSP CT protein also contained the conserved C-terminal of PvCSP following the repeats domains.…”

“…After a washing step with PBS-T, peroxidase-labeled goat anti-mouse IgG (Sigma, St. Louis, MO, USA) was added to each well at a 1:3000 dilution. The OPD/acid stop system was then used to determine anti-PvCSP titers based on the highest dilution of sera yielding an A 492 value higher than 0.1 [22].…”

“…In addition to the conserved domains, our research group has developed recombinant vaccine formulations targeting all three variants of P. vivax CSP capable of eliciting immune responses in mice in the last few years [21]. These constructs have been expressed in both prokaryotic [21] and eukaryotic (yeast) systems [22,23]. The recombinant protein PvCSP-All CT has been found to be highly immunogenic in mice when administered with Poly (I:C) adjuvant.…”

São Paulo School of Advanced Sciences on Vaccines: an overview

“…In addition, the use of a stabilized form of Poly (I:C), Poly-ICLC (Synthetic dsRNA + polylysine + carboxymethycellulose), also known as Hiltonol or Oncovir, combined with NY-ESO-1 for breast cancer treatment in patients with high risk of recurrence or widespread metastases, had encouraging outcomes [110]. Preclinical trials of vaccine formulations with adjuvant Poly (I:C) or Poly-ICLC against Flu [111,112], Ebola [113], and Malaria [114] have shown augmented cellular responses. The Poly-ICLC treatment alone also demonstrated some degree of protection against some respiratory viral diseases and cancers [115,116], but the mechanisms remain elusive.…”