title: Alternative complement pathway deregulation is correlated with dengue severity.
abstract: BACKGROUND
  The complement system, a key component that links the innate and adaptive immune responses, has three pathways: the classical, lectin, and alternative pathways. In the present study, we have analyzed the levels of various complement components in blood samples from dengue fever (DF) and dengue hemorrhagic fever (DHF) patients and found that the level of complement activation is associated with disease severity.
  
  
  RESULTS
  Patients with DHF had lower levels of complement factor 3 (C3; p = 0.002) and increased levels of C3a, C4a and C5a (p<0.0001) when compared to those with the less severe form, DF. There were no significant differences between DF and DHF patients in the levels of C1q, immunocomplexes (CIC-CIq) and CRP. However, small but statistically significant differences were detected in the levels of MBL. In contrast, the levels of two regulatory proteins of the alternative pathway varied widely between DF and DHF patients: DHF patients had higher levels of factor D (p = 0.01), which cleaves factor B to yield the active (C3bBb) C3 convertase, and lower levels of factor H (p = 0.03), which inactivates the (C3bBb) C3 convertase, than did DF patients. When we considered the levels of factors D and H together as an indicator of (C3bBb) C3 convertase regulation, we found that the plasma levels of these regulatory proteins in DHF patients favored the formation of the (C3bBb) C3 convertase, whereas its formation was inhibited in DF patients (p<0.0001).
  
  
  CONCLUSIONS
  The data suggest that an imbalance in the levels of regulatory factors D and H is associated with an abnormal regulation of complement activity in DHF patients.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
authors.forename: Eduardo J M
authors.initials: EJ
authors.lastname: Nascimento
authors.forename: Ana M
authors.initials: AM
authors.lastname: Silva
authors.forename: Marli T
authors.initials: MT
authors.lastname: Cordeiro
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Brito
authors.forename: Laura H V G
authors.initials: LH
authors.lastname: Gil
authors.forename: Ulisses
authors.initials: U
authors.lastname: Braga-Neto
authors.forename: Ernesto T A
authors.initials: ET
authors.lastname: Marques
mesh_terms: D000293:Adolescent; D000328:Adult; D003167:Complement Activation; D003165:Complement System Proteins / Q000378:metabolism*; D003715:Dengue / Q000378:metabolism / Q000503:physiopathology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D003165:Complement System Proteins
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