title: Biological and immunological characterization of recombinant Yellow Fever 17D viruses expressing a Trypanosoma cruzi Amastigote Surface Protein-2 CD8+ T cell epitope at two distinct regions of the genome.
abstract: BACKGROUND
  The attenuated Yellow fever (YF) 17D vaccine virus is one of the safest and most effective viral vaccines administered to humans, in which it elicits a polyvalent immune response. Herein, we used the YF 17D backbone to express a Trypanosoma cruzi CD8+ T cell epitope from the Amastigote Surface Protein 2 (ASP-2) to provide further evidence for the potential of this virus to express foreign epitopes. The TEWETGQI CD8+ T cell epitope was cloned and expressed based on two different genomic insertion sites: in the fg loop of the viral Envelope protein and the protease cleavage site between the NS2B and NS3. We investigated whether the site of expression had any influence on immunogenicity of this model epitope.
  
  
  RESULTS
  Recombinant viruses replicated similarly to vaccine virus YF 17D in cell culture and remained genetically stable after several serial passages in Vero cells. Immunogenicity studies revealed that both recombinant viruses elicited neutralizing antibodies to the YF virus as well as generated an antigen-specific gamma interferon mediated T-cell response in immunized mice. The recombinant viruses displayed a more attenuated phenotype than the YF 17DD vaccine counterpart in mice. Vaccination of a mouse lineage highly susceptible to infection by T. cruzi with a homologous prime-boost regimen of recombinant YF viruses elicited TEWETGQI specific CD8+ T cells which might be correlated with a delay in mouse mortality after a challenge with a lethal dose of T. cruzi.
  
  
  CONCLUSIONS
  We conclude that the YF 17D platform is useful to express T. cruzi (Protozoan) antigens at different functional regions of its genome with minimal reduction of vector fitness. In addition, the model T. cruzi epitope expressed at different regions of the YF 17D genome elicited a similar T cell-based immune response, suggesting that both expression sites are useful. However, the epitope as such is not protective and it remains to be seen whether expression of larger domains of ASP-2, which include the TEWETGQI epitope, will elicit better T-CD8+ responses to the latter. It is likely that additional antigens and recombinant virus formulations will be necessary to generate a protective response.
authors.affiliation: Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Laboratório de Biologia Molecular de Flavivírus, Rio de Janeiro, Fundação Oswaldo Cruz, Avenida Brasil 4365, Manguinhos, Rio de Janeiro, RJ, 21045-900, Brazil.
authors.forename: Raquel T
authors.initials: RT
authors.lastname: Nogueira
authors.forename: Alanderson R
authors.initials: AR
authors.lastname: Nogueira
authors.forename: Mirian C S
authors.initials: MC
authors.lastname: Pereira
authors.forename: Maurício M
authors.initials: MM
authors.lastname: Rodrigues
authors.forename: Ricardo
authors.initials: R
authors.lastname: Galler
authors.forename: Myrna C
authors.initials: MC
authors.lastname: Bonaldo
mesh_terms: D000818:Animals; D014355:Chagas Disease / Q000276:immunology* / Q000469:parasitology / Q000517:prevention & control; D002522:Chlorocebus aethiops; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology*; D005260:Female; D015870:Gene Expression; D005822:Genetic Vectors / Q000235:genetics* / Q000276:immunology; D016679:Genome, Viral; D006801:Humans; D051379:Mice; D008805:Mice, Inbred A; D009439:Neuraminidase / Q000235:genetics* / Q000276:immunology*; D014349:Trypanosoma cruzi / Q000235:genetics / Q000276:immunology; D014709:Vero Cells; D015005:Yellow fever virus / Q000235:genetics* / Q000276:immunology
chemical_list: D018984:Epitopes, T-Lymphocyte; C493236:ASP-2 protein, Trypanosoma cruzi; D009439:Neuraminidase