title: Radiation-induced cellular and molecular alterations in asexual intraerythrocytic Plasmodium falciparum.
abstract: BACKGROUND
  γ-irradiation is commonly used to create attenuation in Plasmodium parasites. However, there are no systematic studies on the survival, reversion of virulence, and molecular basis for γ-radiation-induced cell death in malaria parasites.
  
  
  METHODS
  The effect of γ-irradiation on the growth of asexual Plasmodium falciparum was studied in erythrocyte cultures. Cellular and ultrastructural changes within the parasite were studied by fluorescence and electron microscopy, and genome-wide transcriptional profiling was performed to identify parasite biomarkers of attenuation and cell death.
  
  
  RESULTS
  γ-radiation induced the death of P. falciparum in a dose-dependent manner. These parasites had defective mitosis, sparse cytoplasm, fewer ribosomes, disorganized and clumped organelles, and large vacuoles-observations consistent with "distressed" or dying parasites. A total of 185 parasite genes were transcriptionally altered in response to γ-irradiation (45.9% upregulated, 54.1% downregulated). Loss of parasite survival was correlated with the downregulation of genes encoding translation factors and with upregulation of genes associated with messenger RNA-sequestering stress granules. Genes pertaining to cell-surface interactions, host-cell remodeling, and secreted proteins were also altered.
  
  
  CONCLUSIONS
  These studies provide a framework to assess the safety of γ-irradiation attenuation and promising targets for genetic deletion to produce whole parasite-based attenuated vaccines.
authors.affiliation: Division of Bacterial, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, USA.
authors.forename: Miranda S
authors.initials: MS
authors.lastname: Oakley
authors.forename: Noel
authors.initials: N
authors.lastname: Gerald
authors.forename: Vivek
authors.initials: V
authors.lastname: Anantharaman
authors.forename: Yamei
authors.initials: Y
authors.lastname: Gao
authors.forename: Victoria
authors.initials: V
authors.lastname: Majam
authors.forename: Babita
authors.initials: B
authors.lastname: Mahajan
authors.forename: Phuong Thao
authors.initials: PT
authors.lastname: Pham
authors.forename: Leda
authors.initials: L
authors.lastname: Lotspeich-Cole
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Myers
authors.forename: Thomas F
authors.initials: TF
authors.lastname: McCutchan
authors.forename: Sheldon L
authors.initials: SL
authors.lastname: Morris
authors.forename: L
authors.initials: L
authors.lastname: Aravind
authors.forename: Sanjai
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D019295:Computational Biology; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation; D004912:Erythrocytes / Q000469:parasitology* / Q000648:ultrastructure; D005720:Gamma Rays; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D058977:Molecular Sequence Annotation; D020411:Oligonucleotide Array Sequence Analysis; D010963:Plasmodium falciparum / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects* / Q000648:ultrastructure; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D015800:Protozoan Proteins; D016053:RNA, Protozoan