title: Study of the anti-JCV antibody levels in a Spanish multiple sclerosis cohort.
abstract: BACKGROUND
  One of the risk factor to develop progressive multifocal leukoencephalopathy (PML) among natalizumab-treated patients is the presence and high levels of anti-JCV antibodies. Our purpose was to test the association of different clinical and demographic variables with the presence and levels of anti-JCV antibodies in a Spanish cohort of patients with multiple sclerosis (MS) during natalizumab treatment.
  
  
  METHODS
  All patients with MS from two hospitals with at least one measure of the anti-JCV antibodies levels (2011-2014) were recruited, among them were two PML cases. Anti-JCV antibody levels were assessed using two-step ELISA.
  
  
  RESULTS
  A total of 1061 patients (16·3% natalizumab-treated) participated in this study. The seropositivity rate of anti-JCV antibodies was 58·2%. It increased with age (Pcorrected= 0·00005) and was lower among HLA-DRB1*15:01 carriers (Pcorrected= 0·049). The two patients with PML were HLA-DRB1*15:01 carriers. We had at least three quarterly anti-JCV antibody measurements (index value) from 137 patients, whose levels did not increase during natalizumab treatment. However, 5·8% of these patients had an increase of the index value higher of one point in a maximum of 6 months, something that was more frequently observed (P = 0·054) among patients treated with immunosuppressant prior to natalizumab onset.
  
  
  CONCLUSIONS
  Old age and HLA-DRB1*15:01 were the factors that influence positively and negatively, respectively, our anti-JCV antibody prevalence, although our both PML cases were HLA-DRB1*15:01carriers. Most of our patients showed a stable anti-JCV antibody index values during natalizumab treatment.
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: María I
authors.initials: MI
authors.lastname: Dominguez-Mozo
authors.affiliation: Hospital Universitario Virgen Macarena, Sevilla, Spain.
authors.forename: Macarena
authors.initials: M
authors.lastname: Rus
authors.affiliation: Immunology Department, Hospital Clínico San Carlos, IdISSC, Madrid, Spain.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Santiago
authors.affiliation: Hospital Universitario Virgen Macarena, Sevilla, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Izquierdo
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Casanova
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Victoria
authors.initials: V
authors.lastname: Galan
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: M Angel
authors.initials: MA
authors.lastname: Garcia-Martinez
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Arias-Leal
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: García-Montojo
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Pérez-Pérez
authors.affiliation: Hospital Universitario Quirón Salud Madrid, Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Arroyo
authors.affiliation: Neurology Department, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Alvarez-Lafuente
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000627:therapeutic use*; D007577:JC Virus / Q000276:immunology*; D007968:Leukoencephalopathy, Progressive Multifocal / Q000276:immunology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000188:drug therapy / Q000276:immunology*; D000069442:Natalizumab / Q000627:therapeutic use*; D013030:Spain
chemical_list: D000914:Antibodies, Viral; D007155:Immunologic Factors; D000069442:Natalizumab
keywords: Anti-JC virus antibodies; multiple sclerosis; natalizumab; progressive multifocal leukoencephalopathy