title: Heterologous expression of the filarial nematode alt gene products reveals their potential to inhibit immune function.
abstract: BACKGROUND
  Parasites exploit sophisticated strategies to evade host immunity that require both adaptation of existing genes and evolution of new gene families. We have addressed this question by testing the immunological function of novel genes from helminth parasites, in which conventional transgenesis is not yet possible. We investigated two such novel genes from Brugia malayi termed abundant larval transcript (alt), expression of which reaches ~5% of total transcript at the time parasites enter the human host.
  
  
  RESULTS
  To test the hypothesis that ALT proteins modulate host immunity, we adopted an alternative transfection strategy to express these products in the protozoan parasite Leishmania mexicana. We then followed the course of infection in vitro in macrophages and in vivo in mice. Expression of ALT proteins, but not a truncated mutant, conferred greater infectivity of macrophages in vitro, reaching 3-fold higher parasite densities. alt-transfected parasites also caused accelerated disease in vivo, and fewer mice were able to clear infection of organisms expressing ALT. alt-transfected parasites were more resistant to IFN-gamma-induced killing by macrophages. Expression profiling of macrophages infected with transgenic L. mexicana revealed consistently higher levels of GATA-3 and SOCS-1 transcripts, both associated with the Th2-type response observed in in vivo filarial infection.
  
  
  CONCLUSIONS
  Leishmania transfection is a tractable and informative approach to determining immunological functions of single genes from heterologous organisms. In the case of the filarial ALT proteins, our data suggest that they may participate in the Th2 bias observed in the response to parasite infection by modulating cytokine-induced signalling within immune system cells.
authors.affiliation: Institute of Immunology and Infection Research, University of Edinburgh, UK. n.gomez@ed.ac.uk
authors.forename: Natalia
authors.initials: N
authors.lastname: Gomez-Escobar
authors.forename: Clare
authors.initials: C
authors.lastname: Bennett
authors.forename: Lidia
authors.initials: L
authors.lastname: Prieto-Lafuente
authors.forename: Toni
authors.initials: T
authors.lastname: Aebischer
authors.forename: Clare C
authors.initials: CC
authors.lastname: Blackburn
authors.forename: Rick M
authors.initials: RM
authors.lastname: Maizels
mesh_terms: D000818:Animals; D017178:Brugia malayi / Q000235:genetics* / Q000502:physiology; D002460:Cell Line; D005260:Female; D005368:Filariasis / Q000235:genetics / Q000276:immunology* / Q000469:parasitology*; D005786:Gene Expression Regulation / Q000502:physiology; D017238:Genes, Helminth / Q000502:physiology*; D015801:Helminth Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D007165:Immunosuppression Therapy; D007894:Leishmania mexicana / Q000235:genetics / Q000502:physiology; D016773:Leishmaniasis, Cutaneous / Q000235:genetics / Q000276:immunology* / Q000469:parasitology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA
chemical_list: D015801:Helminth Proteins