title: Characterization of a Plasmodium berghei sexual stage antigen PbPH as a new candidate for malaria transmission-blocking vaccine.
abstract: BACKGROUND
  Transmission-blocking vaccines (TBVs) are a promising strategy for malaria control and elimination. However, candidate TBV antigens are currently limited, highlighting the urgency of identifying new antigens for TBV development.
  
  
  METHODS
  Using a combination of bioinformatic analysis and functional studies in the rodent malaria model Plasmodium berghei, we identified a conserved Plasmodium protein PbPH (PBANKA_041720) containing a pleckstrin homology (PH) domain. The expression of PbPH was detected by Western blot and indirect immunofluorescence assay (IFA). The function of PbPH was tested by genetic knockout. The TB activity was confirmed by in vitro ookinete conversion assay and mosquito feeding.
  
  
  RESULTS
  PbPH was detected in Western blot as highly expressed in sexual stages (gametocytes and ookinetes). IFA revealed localizations of PbPH on the surface of gametes, zygotes, and ookinetes. Deletion of the pbph gene did not affect asexual growth, but significantly reduced the formation of gametocytes, ookinetes, and oocysts, indicating that PbPH protein is required for parasite sexual development. Recombinant PbPH expressed and purified from bacteria elicited strong antibody responses in mice and the antibodies significantly inhibited exflagellation of male gametocytes and formation of ookinetes in a concentration-dependent manner. Mosquito feeding experiments confirmed that mosquitoes fed on mice immunized with PbPH had 13 % reduction in the prevalence of infection and almost 48 % reduction in oocyst density.
  
  
  CONCLUSIONS
  Pbph is a highly conserved Plasmodium gene and is required for parasite sexual development. PbPH protein is expressed on the surface of gametes and ookinetes. Immunization of mice against the recombinant PbPH protein induced strong antibody responses that effectively reduced the formation of male gametes and ookinetes in vitro and blocked transmission of the parasites to mosquitoes. These results highlight PbPH as a potential TBV candidate that is worth future investigations in human malaria parasites.
authors.affiliation: Department of Pathogen Biology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China.|College of Animal Husbandry and Veterinary, Liaoning Medical University, Jinzhou, Liaoning, 121001, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Kou
authors.affiliation: Department of Pathogen Biology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China.
authors.forename: Wenqi
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Department of Pathogen Biology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Du
authors.affiliation: Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Pathogen Biology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China.
authors.forename: Meilian
authors.initials: M
authors.lastname: Wang
authors.affiliation: Dalian Institute of Biotechnology, Dalian, Liaoning, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Fan
authors.affiliation: Department of Entomology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Liwang
authors.initials: L
authors.lastname: Cui
authors.affiliation: Department of Pathogen Biology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China. enjieluo@hotmail.com.
authors.forename: Enjie
authors.initials: E
authors.lastname: Luo
authors.affiliation: Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, Liaoning, 110001, China. ymcao@mail.cmu.edu.cn.
authors.forename: Yaming
authors.initials: Y
authors.lastname: Cao
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D015153:Blotting, Western; D019295:Computational Biology; D004195:Disease Models, Animal; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D019084:Fluorescent Antibody Technique, Indirect; D055786:Gene Knockout Techniques; D008288:Malaria / Q000517:prevention & control*; D017780:Malaria Vaccines / Q000276:immunology* / Q000302:isolation & purification*; D051379:Mice; D010962:Plasmodium berghei / Q000276:immunology* / Q000502:physiology; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D000953:Antigens, Protozoan; D017780:Malaria Vaccines; D015800:Protozoan Proteins
keywords: Gametocyte; Malaria; Ookinete; PH domain protein; Plasmodium berghei; Sexual development; Transmission-blocking vaccine