title: Genetic recombination between human and animal parasites creates novel strains of human pathogen.
abstract: Genetic recombination between pathogens derived from humans and livestock has the potential to create novel pathogen strains, highlighted by the influenza pandemic H1N1/09, which was derived from a re-assortment of swine, avian and human influenza A viruses. Here we investigated whether genetic recombination between subspecies of the protozoan parasite, Trypanosoma brucei, from humans and animals can generate new strains of human pathogen, T. b. rhodesiense (Tbr) responsible for sleeping sickness (Human African Trypanosomiasis, HAT) in East Africa. The trait of human infectivity in Tbr is conferred by a single gene, SRA, which is potentially transferable to the animal pathogen Tbb by sexual reproduction. We tracked the inheritance of SRA in crosses of Tbr and Tbb set up by co-transmitting genetically-engineered fluorescent parental trypanosome lines through tsetse flies. SRA was readily transferred into new genetic backgrounds by sexual reproduction between Tbr and Tbb, thus creating new strains of the human pathogen, Tbr. There was no evidence of diminished growth or transmissibility of hybrid trypanosomes carrying SRA. Although expression of SRA is critical to survival of Tbr in the human host, we show that the gene exists as a single copy in a representative collection of Tbr strains. SRA was found on one homologue of chromosome IV in the majority of Tbr isolates examined, but some Ugandan Tbr had SRA on both homologues. The mobility of SRA by genetic recombination readily explains the observed genetic variability of Tbr in East Africa. We conclude that new strains of the human pathogen Tbr are being generated continuously by recombination with the much larger pool of animal-infective trypanosomes. Such novel recombinants present a risk for future outbreaks of HAT.
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom.
authors: Wendy
authors: W
authors: Gibson
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom; Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol, United Kingdom.
authors: Lori
authors: L
authors: Peacock
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom; Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol, United Kingdom.
authors: Vanessa
authors: V
authors: Ferris
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom.
authors: Katrin
authors: K
authors: Fischer
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom.
authors: Jennifer
authors: J
authors: Livingstone
authors: School of Biological Sciences University of Bristol, Bristol, United Kingdom.
authors: James
authors: J
authors: Thomas
authors: Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol, United Kingdom.
authors: Mick
authors: M
authors: Bailey
mesh_terms: D000351:Africa, Eastern / Q000453:epidemiology; D000818:Animals; D003433:Crosses, Genetic; D005453:Fluorescence; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics*; D013045:Species Specificity; D016833:Trypanosoma brucei rhodesiense / Q000235:genetics*; D014353:Trypanosomiasis, African / Q000453:epidemiology* / Q000469:parasitology*
chemical_list: D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; C403774:serum resistance associated protein, Trypanosoma brucei