title: A FashiLymphoproliferative Phenotype Reveals Non-Apoptotic Fas Signaling in HTLV-1-Associated Neuroinflammation.
abstract: Human T-cell lymphotropic virus (HTLV)-1 was the first human retrovirus to be associated to cancer, namely adult T-cell leukemia (ATL), but its pathogenesis remains enigmatic, since only a minority of infected individuals develops either ATL or the neuroinflammatory disorder HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). A functionalFAS-670 polymorphism in an interferon (IFN)-regulated STAT1-binding site has been associated to both ATL and HAM/TSP susceptibility. FashiT stem cell memory (Tscm) cells have been identified as the hierarchical apex of ATL, but have not been investigated in HAM/TSP. In addition, bothFASandSTAT1have been identified in an IFN-inducible HAM/TSP gene signature, but its pathobiological significance remains unclear. We comprehensively explored Fas expression (protein/mRNA) and function in lymphocyte activation, apoptosis, proliferation, and transcriptome, in PBMC from a total of 47 HAM/TSP patients, 40 asymptomatic HTLV-1-infected individuals (AC), and 58 HTLV-1 -uninfected healthy controls. Fas surface expression followed a two-step increase from HC to AC and from AC to HAM/TSP. In HAM/TSP, Fas levels correlated positively to lymphocyte activation markers, but negatively to age of onset, linking Fashicells to earlier, more aggressive disease. Surprisingly, increased lymphocyte Fas expression in HAM/TSP was linked to decreased apoptosis and increased lymphoproliferation uponin vitroculture, but not to proviral load. This Fashiphenotype is HAM/TSP-specific, since bothex vivoandin vitroFas expression was increased as compared to multiple sclerosis (MS), another neuroinflammatory disorder. To elucidate the molecular mechanism underlying non-apoptotic Fas signaling in HAM/TSP, we combined transcriptome analysis with functional assays, i.e., blocking vs. triggering Fas receptorin vitrowith antagonist and agonist-, anti-Fas mAb, respectively. Treatment with agonist anti-Fas mAb restored apoptosis, indicating biased, but not defective Fas signaling in HAM/TSP.In silicoanalysis revealed biased Fas signaling toward proliferation and inflammation, driven by RelA/NF-κB. Correlation of Fas transcript levels with proliferation (but not apoptosis) was confirmed in HAM/TSPex vivotranscriptomes. In conclusion, we demonstrated a two-step increase in Fas expression, revealing a unique Fashilymphocyte phenotype in HAM/TSP, distinguishable from MS. Non-apoptotic Fas signaling might fuel HAM/TSP pathogenesis, through increased lymphoproliferation, inflammation, and early age of onset.
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven , Leuven , Belgium.
authors.forename: Soraya Maria
authors.initials: SM
authors.lastname: Menezes
authors.affiliation: Department of Microbiology, Immunology & Tropical Medicine, The George Washington University , Washington, DC , USA.
authors.forename: Fabio E
authors.initials: FE
authors.lastname: Leal
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven , Leuven , Belgium.
authors.forename: Tim
authors.initials: T
authors.lastname: Dierckx
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium; LIMI, Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Khouri
authors.affiliation: LIMI, Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ) , Salvador , Brazil.
authors.forename: Daniele
authors.initials: D
authors.lastname: Decanine
authors.affiliation: LIMI, Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ) , Salvador , Brazil.
authors.forename: Gilvaneia
authors.initials: G
authors.lastname: Silva-Santos
authors.affiliation: LIMI, Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ) , Salvador , Brazil.
authors.forename: Saul V
authors.initials: SV
authors.lastname: Schnitman
authors.affiliation: Bahiana School of Medicine and Public Health , Salvador , Brazil.
authors.forename: Ramon
authors.initials: R
authors.lastname: Kruschewsky
authors.affiliation: Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia , Lima , Peru.
authors.forename: Giovanni
authors.initials: G
authors.lastname: López
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium; Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Carolina
authors.initials: C
authors.lastname: Alvarez
authors.affiliation: Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia , Lima , Peru.
authors.forename: Michael
authors.initials: M
authors.lastname: Talledo
authors.affiliation: Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru; Departamento de Enfermedades Infecciosas, Tropicales y Dermatológicas, Hospital Cayetano Heredia, Lima, Peru.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gotuzzo
authors.affiliation: Department of Microbiology, Immunology & Tropical Medicine, The George Washington University , Washington, DC , USA.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Nixon
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven , Leuven , Belgium.
authors.forename: Jurgen
authors.initials: J
authors.lastname: Vercauteren
authors.affiliation: INSERM UMR1043 and Pôle des Neurosciences, Hôpital Purpan, Université de Toulouse , Toulouse , France.
authors.forename: David
authors.initials: D
authors.lastname: Brassat
authors.affiliation: INSERM UMR1043 and Pôle des Neurosciences, Hôpital Purpan, Université de Toulouse , Toulouse , France.
authors.forename: Roland
authors.initials: R
authors.lastname: Liblau
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium; Center for Global Health and Tropical Medicine, Unidade de Microbiologia, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, Portugal.
authors.forename: Anne Mieke
authors.initials: AM
authors.lastname: Vandamme
authors.affiliation: Bahiana School of Medicine and Public Health , Salvador , Brazil.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Galvão-Castro
authors.affiliation: Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, KU Leuven , Leuven , Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Van Weyenbergh
keywords: Fas/CD95; HTLV-1-associated myelopathy/tropical spastic paraparesis; NF-κB; apoptosis; interferon; lymphoproliferative disease; multiple sclerosis; proliferation