Characterization of Plasmodium berghei Pbg37 as Both a Pre- and Postfertilization Antigen with Transmission-Blocking Potential

Infect Immun. 2018 Jul 23;86(8):e00785-17. doi: 10.1128/IAI.00785-17. Print 2018 Aug.


Transmission-blocking vaccines (TBVs) interrupting malaria transmission are an integrated tool for malaria eradication. We characterized a sexual-stage-specific gene (PBANKA_060330) from Plasmodium berghei and studied its potential for use as a TBV. This gene, referred to as pbg37, encodes a protein of 37 kDa with a signal peptide and multiple transmembrane domains and is preferentially expressed in gametocytes. A recombinant Pbg37 (rPbg37) protein targeting the N-terminal 63 amino acids (amino acids 26 to 88) expressed in bacteria elicited strong antibody responses in mice. Western blotting demonstrated Pbg37 expression in gametocytes, zygotes, and, to a lesser extent, ookinetes and its predominant association with the membranes of gametocytes. Indirect immunofluorescence assay showed an abundant surface localization of Pbg37 on gametes and zygotes but reduced amounts on retorts and ookinetes. Knockout of pbg37pbg37) led to a considerable reduction in gametocytemia, which translated into a ~92.1% decrease in the oocyst number in mosquitoes. Deletion of pbg37 had a more substantial influence on the development and maturation of microgametocytes. As a result, the Δpbg37 lines exhibited a higher female/male gametocyte ratio, fewer mature male gametocytes, and defects in the exflagellation of mature microgametocytes. To test the transmission-blocking potential of Pbg37, an in vitro ookinete assay showed that the major inhibitory effects of anti-Pbg37 antiserum were on the exflagellation and fertilization processes. Direct feeding of mosquitoes on mice immunized with rPbg37 or a control protein showed that rPbg37-immunized and P. berghei-infected mice had a significant reduction (49.1%) in oocyst density compared to the controls. The conservation of this gene in Plasmodium warrants further investigations in human malaria parasites.

Keywords: Plasmodium berghei; gamete; gametocyte; ookinete; postfertilization; prefertilization; transmission-blocking vaccine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Protozoan / blood
  • Antibody Formation
  • Blotting, Western
  • Disease Models, Animal
  • Disease Transmission, Infectious / prevention & control*
  • Female
  • Fluorescent Antibody Technique, Indirect
  • Gene Deletion
  • Gene Expression Profiling
  • Malaria / prevention & control*
  • Malaria Vaccines / administration & dosage
  • Malaria Vaccines / genetics
  • Malaria Vaccines / immunology*
  • Male
  • Membrane Proteins / analysis
  • Membrane Proteins / immunology
  • Mice, Inbred BALB C
  • Mosquito Vectors / parasitology
  • Parasite Load
  • Parasitemia
  • Plasmodium berghei / chemistry
  • Plasmodium berghei / genetics
  • Plasmodium berghei / immunology*
  • Protozoan Proteins / analysis
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology*
  • Vaccines, Synthetic / administration & dosage
  • Vaccines, Synthetic / genetics
  • Vaccines, Synthetic / immunology
  • Virulence


  • Antibodies, Protozoan
  • Malaria Vaccines
  • Membrane Proteins
  • Protozoan Proteins
  • Vaccines, Synthetic