title: A prospective study of Chlamydia pneumoniae infection and risk of MS in two US cohorts.
abstract: BACKGROUND
  Chlamydia pneumoniae (Cpn) has been proposed as a possible etiologic agent in multiple sclerosis (MS). However, previous studies were cross-sectional and could not assess whether Cpn infection preceded the onset of MS.
  
  
  METHODS
  The authors conducted a prospective nested case-control study among 3 million US Army personnel and 121,466 members of the Kaiser Permanente Medical Care Program (KPMCP) cohort. Serum samples collected prior to onset of MS symptoms were available for 83 MS cases in the Army and 46 in the KPMCP cohort. Two controls were matched to each case on age, sex, and date of blood collection. Microimmunofluorescence was used to measure serum immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody titers to Cpn; IgG titers > or 1:16 were considered positive for past Cpn infection.
  
  
  RESULTS
  Seropositivity for Cpn was not significantly associated with risk of MS in either cohort (Army: OR = 1.0; 95% CI 0.6, 1.8; KPMCP: OR = 1.5; 95% CI 0.7, 3.1) or in the pooled analysis (OR = 1.2; 95% CI 0.8, 1.9). Serum levels of anti-Cpn IgG antibody were also not associated with an increased risk of MS in the Army (OR for a fourfold difference in antibody titers = 0.9; 95% CI 0.7, 1.2) or in the pooled analysis (OR = 1.2; 95% CI 0.9, 1.4), but a significant increase in risk was seen in the KPMCP cohort (OR = 1.7; 95% CI 1.2, 2.5). The difference between these results in the Army and the KPMCP cohort was significant (p = 0.01).
  
  
  CONCLUSIONS
  Neither Cpn seropositivity nor serum anti-Cpn IgG antibody titers predicted risk of developing MS. However, due to the heterogeneity of results between cohorts, we cannot exclude the possibility that infection with Cpn may modify the risk of MS.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Munger
authors.forename: G N
authors.initials: GN
authors.lastname: DeLorenze
authors.forename: L I
authors.initials: LI
authors.lastname: Levin
authors.forename: M V
authors.initials: MV
authors.lastname: Rubertone
authors.forename: J H
authors.initials: JH
authors.lastname: Vogelman
authors.forename: C A
authors.initials: CA
authors.lastname: Peck
authors.forename: R W
authors.initials: RW
authors.lastname: Peeling
authors.forename: N
authors.initials: N
authors.lastname: Orentreich
authors.forename: A
authors.initials: A
authors.lastname: Ascherio
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood; D002140:California / Q000453:epidemiology; D016022:Case-Control Studies; D023521:Chlamydophila Infections / Q000453:epidemiology* / Q000276:immunology; D016993:Chlamydophila pneumoniae / Q000276:immunology; D015331:Cohort Studies; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D006279:Health Maintenance Organizations; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D008889:Military Personnel; D009103:Multiple Sclerosis / Q000453:epidemiology* / Q000276:immunology; D011446:Prospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G