Identification of Novel Pre-Erythrocytic Malaria Antigen Candidates for Combination Vaccines with Circumsporozoite Protein

PLoS One. 2016 Jul 19;11(7):e0159449. doi: 10.1371/journal.pone.0159449. eCollection 2016.

Abstract

Malaria vaccine development has been hampered by the limited availability of antigens identified through conventional discovery approaches, and improvements are needed to enhance the efficacy of the leading vaccine candidate RTS,S that targets the circumsporozoite protein (CSP) of the infective sporozoite. Here we report a transcriptome-based approach to identify novel pre-erythrocytic vaccine antigens that could potentially be used in combination with CSP. We hypothesized that stage-specific upregulated genes would enrich for protective vaccine targets, and used tiling microarray to identify P. falciparum genes transcribed at higher levels during liver stage versus sporozoite or blood stages of development. We prepared DNA vaccines for 21 genes using the predicted orthologues in P. yoelii and P. berghei and tested their efficacy using different delivery methods against pre-erythrocytic malaria in rodent models. In our primary screen using P. yoelii in BALB/c mice, we found that 16 antigens significantly reduced liver stage parasite burden. In our confirmatory screen using P. berghei in C57Bl/6 mice, we confirmed 6 antigens that were protective in both models. Two antigens, when combined with CSP, provided significantly greater protection than CSP alone in both models. Based on the observations reported here, transcriptional patterns of Plasmodium genes can be useful in identifying novel pre-erythrocytic antigens that induce protective immunity alone or in combination with CSP.

MeSH terms

  • Animals
  • Antibodies, Protozoan / immunology*
  • Antibodies, Protozoan / therapeutic use
  • Antigens, Protozoan / immunology
  • Female
  • Humans
  • Malaria Vaccines / genetics
  • Malaria Vaccines / immunology*
  • Malaria Vaccines / therapeutic use
  • Malaria, Falciparum / drug therapy*
  • Malaria, Falciparum / immunology
  • Malaria, Falciparum / parasitology
  • Mice
  • Mice, Inbred C57BL
  • Plasmodium falciparum / immunology
  • Plasmodium falciparum / pathogenicity
  • Plasmodium yoelii / immunology
  • Protozoan Proteins / immunology*
  • Vaccines, DNA / genetics
  • Vaccines, DNA / immunology
  • Vaccines, DNA / therapeutic use

Substances

  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Malaria Vaccines
  • Protozoan Proteins
  • Vaccines, DNA
  • circumsporozoite protein, Protozoan

Grants and funding

The work was funded in part by the PATH Malaria Vaccine Initiative, by the Intramural Research Program of NIAID, NIH and the Military Infectious Diseases Research Program of Walter Reed Army Institute of Research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.