title: Hepatitis B infection is associated with asymptomatic malaria in the Brazilian Amazon.
abstract: BACKGROUND
  Areas that are endemic for malaria are also highly endemic for hepatitis B virus (HBV) infection. Nevertheless, it is unknown whether HBV infection modifies the clinical presentation of malaria. This study aimed to address this question.
  
  
  RESULTS
  An observational study of 636 individuals was performed in Rondônia, western Amazon, Brazil between 2006 and 2007. Active and passive case detections identified Plasmodium infection by field microscopy and nested Polymerase Chain Reaction (PCR). HBV infections were identified by serology and confirmed by real-time PCR. Epidemiological information and plasma cytokine profiles were studied. The data were analyzed using adjusted multinomial logistic regression. Plasmodium-infected individuals with active HBV infection were more likely to be asymptomatic (OR: 120.13, P<0.0001), present with lower levels of parasitemia and demonstrate a decreased inflammatory cytokine profile. Nevertheless, co-infected individuals presented higher HBV viremia. Plasmodium parasitemia inversely correlated with plasma HBV DNA levels (r = -0.6; P = 0.0003).
  
  
  CONCLUSIONS
  HBV infection diminishes the intensity of malaria infection in individuals from this endemic area. This effect seems related to cytokine balance and control of inflammatory responses. These findings add important insights to the understanding of the factors affecting the clinical outcomes of malaria in endemic regions.
authors.affiliation: Centro de Pesquisas Gonçalo Moniz, Fundação Oswaldo Cruz, Salvador, Brazil.
authors.forename: Bruno B
authors.initials: BB
authors.lastname: Andrade
authors.forename: Cristiane J N
authors.initials: CJ
authors.lastname: Santos
authors.forename: Luís M
authors.initials: LM
authors.lastname: Camargo
authors.forename: Sebastião M
authors.initials: SM
authors.lastname: Souza-Neto
authors.forename: Antonio
authors.initials: A
authors.lastname: Reis-Filho
authors.forename: Jorge
authors.initials: J
authors.lastname: Clarêncio
authors.forename: Vitor R R
authors.initials: VR
authors.lastname: Mendonça
authors.forename: Nívea F
authors.initials: NF
authors.lastname: Luz
authors.forename: Erney P
authors.initials: EP
authors.lastname: Camargo
authors.forename: Aldina
authors.initials: A
authors.lastname: Barral
authors.forename: Antônio A M
authors.initials: AA
authors.lastname: Silva
authors.forename: Manoel
authors.initials: M
authors.lastname: Barral-Netto
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D006509:Hepatitis B / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens; D006515:Hepatitis B virus / Q000235:genetics; D006801:Humans; D008288:Malaria / Q000150:complications* / Q000821:virology; D008297:Male; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000472:pathogenicity*; D010966:Plasmodium vivax / Q000472:pathogenicity*; D012307:Risk Factors; D055815:Young Adult
chemical_list: D016207:Cytokines; D004279:DNA, Viral; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens