title: Filariasis attenuates anemia and proinflammatory responses associated with clinical malaria: a matched prospective study in children and young adults.
abstract: BACKGROUND
  Wuchereria bancrofti (Wb) and Mansonella perstans (Mp) are blood-borne filarial parasites that are endemic in many countries of Africa, including Mali. The geographic distribution of Wb and Mp overlaps considerably with that of malaria, and coinfection is common. Although chronic filarial infection has been shown to alter immune responses to malaria parasites, its effect on clinical and immunologic responses in acute malaria is unknown.
  
  
  RESULTS
  To address this question, 31 filaria-positive (FIL+) and 31 filaria-negative (FIL-) children and young adults, matched for age, gender and hemoglobin type, were followed prospectively through a malaria transmission season. Filarial infection was defined by the presence of Wb or Mp microfilariae on calibrated thick smears performed between 10 pm and 2 am and/or by the presence of circulating filarial antigen in serum. Clinical malaria was defined as axillary temperature ≥37.5°C or another symptom or sign compatible with malaria infection plus the presence of asexual malaria parasites on a thick blood smear. Although the incidence of clinical malaria, time to first episode, clinical signs and symptoms, and malaria parasitemia were comparable between the two groups, geometric mean hemoglobin levels were significantly decreased in FIL- subjects at the height of the transmission season compared to FIL+ subjects (11.4 g/dL vs. 12.5 g/dL, p<0.01). Plasma levels of IL-1ra, IP-10 and IL-8 were significantly decreased in FIL+ subjects at the time of presentation with clinical malaria (99, 2145 and 49 pg/ml, respectively as compared to 474, 5522 and 247 pg/ml in FIL- subjects).
  
  
  CONCLUSIONS
  These data suggest that pre-existent filarial infection attenuates immune responses associated with severe malaria and protects against anemia, but has little effect on susceptibility to or severity of acute malaria infection. The apparent protective effect of filarial infection against anemia is intriguing and warrants further study in a larger cohort.
authors.affiliation: Faculty of Medicine, Pharmacy and Dentistry, University of Bamako, Bamako, Mali.
authors.forename: Housseini
authors.initials: H
authors.lastname: Dolo
authors.forename: Yaya I
authors.initials: YI
authors.lastname: Coulibaly
authors.forename: Benoit
authors.initials: B
authors.lastname: Dembele
authors.forename: Siaka
authors.initials: S
authors.lastname: Konate
authors.forename: Siaka Y
authors.initials: SY
authors.lastname: Coulibaly
authors.forename: Salif S
authors.initials: SS
authors.lastname: Doumbia
authors.forename: Abdallah A
authors.initials: AA
authors.lastname: Diallo
authors.forename: Lamine
authors.initials: L
authors.lastname: Soumaoro
authors.forename: Michel E
authors.initials: ME
authors.lastname: Coulibaly
authors.forename: Seidina A S
authors.initials: SA
authors.lastname: Diakite
authors.forename: Aldiouma
authors.initials: A
authors.lastname: Guindo
authors.forename: Michael P
authors.initials: MP
authors.lastname: Fay
authors.forename: Simon
authors.initials: S
authors.lastname: Metenou
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
authors.forename: Amy D
authors.initials: AD
authors.lastname: Klion
mesh_terms: D000293:Adolescent; D000740:Anemia / Q000209:etiology / Q000473:pathology*; D000818:Animals; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000097:blood*; D005260:Female; D005368:Filariasis / Q000150:complications* / Q000276:immunology / Q000473:pathology*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D015994:Incidence; D008288:Malaria / Q000150:complications* / Q000276:immunology / Q000473:pathology*; D008297:Male; D008302:Mali; D008366:Mansonella / Q000302:isolation & purification; D010961:Plasmodium / Q000302:isolation & purification; D011446:Prospective Studies; D014958:Wuchereria bancrofti / Q000302:isolation & purification; D055815:Young Adult
chemical_list: D016207:Cytokines; D006454:Hemoglobins