title: Do Toxoplasma gondii RH strain tachyzoites evolve during continuous passage?
abstract: OBJECTIVE
  To examine three lineages of Toxoplasma gondii RH strain in terms of performance in the dye test, culture, and gene expression.
  
  
  METHODS
  Historical data (culture growth and performance in the dye test) from three lineages of RH strain tachyzoites (B, J, and Q) that had been continuously cultured in HeLa cells was assessed. Tachyzoite harvests obtained during continuous cell culture were retrieved from liquid nitrogen and cultured in HeLa cells, providing mRNA that was extracted and used to study gene expression using random amplified polymorphic DNA analysis at different stages of lineage adaptation to continuous culture.
  
  
  RESULTS
  The B and Q lineages consistently produced tachyzoites that were successfully used in the dye test and their gene expression was stable after multiple passages. The J lineage had unpredictable growth, tachyzoites unsuitable for use in the dye test, and changing gene expression with multiple passage.
  
  
  CONCLUSIONS
  This study has explained some anomalies in the performance of different stocks of T gondii, and suggests that lineages that are still evolving in cell culture should be avoided.
authors.affiliation: Scottish Toxoplasma Reference Laboratory, Raigmore Hospital, Inverness IV2 3UJ, UK. microbiology@haht.scot.nhs.uk
authors.forename: S
authors.initials: S
authors.lastname: Mavin
authors.forename: A W L
authors.initials: AW
authors.lastname: Joss
authors.forename: J
authors.initials: J
authors.lastname: Ball
authors.forename: D O
authors.initials: DO
authors.lastname: Ho-Yen
mesh_terms: D000818:Animals; D018076:DNA, Complementary / Q000096:biosynthesis; D016054:DNA, Protozoan / Q000096:biosynthesis; D015870:Gene Expression; D017125:Genes, Protozoan; D006367:HeLa Cells; D006801:Humans; D019105:Random Amplified Polymorphic DNA Technique / Q000379:methods; D014122:Toxoplasma / Q000145:classification / Q000235:genetics / Q000254:growth & development*
chemical_list: D018076:DNA, Complementary; D016054:DNA, Protozoan