Synthetic DNA Vaccines Adjuvanted with pIL-33 Drive Liver-Localized T Cells and Provide Protection from Plasmodium Challenge in a Mouse Model

Abstract

tr (A.S.I.A.) † These authors contributed equally to this work and are presented in alphabetical order.Abstract: The need for a malaria vaccine is indisputable. A single vaccine for Plasmodium pre-erythrocytic stages targeting the major sporozoite antigen circumsporozoite protein (CSP) has had partial success. Additionally, CD8+ T cells targeting liver-stage (LS) antigens induced by live attenuated sporozoite vaccines were associated with protection in human challenge experiments. To further evaluate protection mediated by LS antigens, we focused on exported pre-erythrocytic proteins (exported protein 1 (EXP1), profilin (PFN), exported protein 2 (EXP2), inhibitor of cysteine proteases (ICP), transmembrane protein 21 (TMP21), and upregulated in infective sporozoites-3 (UIS3)) expressed in all Plasmodium species and designed optimized, synthetic DNA (synDNA) immunogens. SynDNA antigen cocktails were tested with and without the molecular adjuvant plasmid IL-33. Immunized animals developed robust T cell responses including induction of antigen-specific liver-localized CD8+ T cells, which were enhanced by the co-delivery of plasmid IL-33. In total, 100% of mice in adjuvanted groups and 71%-88% in non-adjuvanted groups were protected from blood-stage disease following Plasmodium yoelii sporozoite challenge. This study supports the potential of synDNA LS antigens as vaccine components for malaria parasite infection.

An Attenuated HSV-1-Derived Malaria Vaccine Expressing Liver-Stage Exported Proteins Induces Sterilizing Protection against Infectious Sporozoite Challenge

“…Importantly, the three LS exported proteins used in this study were selected based on a previous study, which showed their potential induction of CD8 T cells and their role in conferring sterile protection against infectious sporozoites when tested individually [5]. Despite the fact that the correlates of protection for each of the LS exported proteins in this viral vaccine were not tested, it will be the goal of future studies to identify the correlates of protection for the antigens presented by this vaccine.…”

“…VC2 is safe and immunogenic in mice, guinea pigs, and non-human primates [4]. To produce a malaria vaccine, we selected the highly conserved malaria parasite proteins EXP1 (exported protein 1), TMP21 (transmembrane protein 21) and UIS3 (upregulated in infectious sporozoites), as they were the best LS exported protein candidates that showed, individually, the best results in protecting immunized mice against an infectious sporozoite challenge, and eliciting CD8 T cells in a previous DNA immunization study from our lab [5]. However, the best protection against a challenge was achieved when the three proteins were combined in intramuscular DNA immunization [5]; therefore, here, they were selected in a combination of three recombinant viral vaccines, each expressing one of the selected LS exported antigens.…”

“…To produce a malaria vaccine, we selected the highly conserved malaria parasite proteins EXP1 (exported protein 1), TMP21 (transmembrane protein 21) and UIS3 (upregulated in infectious sporozoites), as they were the best LS exported protein candidates that showed, individually, the best results in protecting immunized mice against an infectious sporozoite challenge, and eliciting CD8 T cells in a previous DNA immunization study from our lab [5]. However, the best protection against a challenge was achieved when the three proteins were combined in intramuscular DNA immunization [5]; therefore, here, they were selected in a combination of three recombinant viral vaccines, each expressing one of the selected LS exported antigens. We specifically chose highly conserved and low-molecular-mass malaria parasite LS exported antigens with the rationale that (i) the export of these antigens at or beyond the parasitophorous vacuolar membrane (PVM) makes them more likely to be presented via the MHC I of infected hepatocytes; (ii) these proteins are of relatively low molecular mass, enabling their efficient expression as fusion proteins with the HSV-1 VP26 tegument protein; (iii) these proteins are expressed in Plasmodium species during early to mid LS development, allowing for the possibility that effector CD8+ T cells could target infected hepatocytes before merozoites are formed, preventing clinical malaria [5,6].…”

“…However, the best protection against a challenge was achieved when the three proteins were combined in intramuscular DNA immunization [5]; therefore, here, they were selected in a combination of three recombinant viral vaccines, each expressing one of the selected LS exported antigens. We specifically chose highly conserved and low-molecular-mass malaria parasite LS exported antigens with the rationale that (i) the export of these antigens at or beyond the parasitophorous vacuolar membrane (PVM) makes them more likely to be presented via the MHC I of infected hepatocytes; (ii) these proteins are of relatively low molecular mass, enabling their efficient expression as fusion proteins with the HSV-1 VP26 tegument protein; (iii) these proteins are expressed in Plasmodium species during early to mid LS development, allowing for the possibility that effector CD8+ T cells could target infected hepatocytes before merozoites are formed, preventing clinical malaria [5,6]. To this end, we generated three unique HSV-1 viruses expressing each of the malaria antigens.…”

Harnessing Recent Advances in Synthetic DNA and Electroporation Technologies for Rapid Vaccine Development Against COVID-19 and Other Emerging Infectious Diseases

“…Co-delivery of IL-2, for example, was observed to improve the immunogenicity of DNA vaccines against SARS-CoV S and N proteins, influenza H1N1 hemagglutinin and neuraminidase, and HIV gp120 and Nef (92)(93)(94). Co-delivery of DNA vaccine against liver-stage malaria antigens with IL-33 was found to improve liver-localized CD8+ T-cell responses and confer improved protection to mice from Plasmodium challenge (95). Co-administration of IL-36γ, on the other hand, was found to improve immune responses induced by DNA-encoded Zika, HIV and influenza vaccines, and reduced dose requirement of DNA vaccines in mice to protect against ZIKV challenge (96).…”