title: Protective Effect of Chronic Schistosomiasis in Baboons Coinfected with Schistosoma mansoni and Plasmodium knowlesi.
abstract: Malaria and schistosomiasis coinfections are common, and chronic schistosomiasis has been implicated in affecting the severity of acute malaria. However, whether it enhances or attenuates malaria has been controversial due the lack of appropriately controlled human studies and relevant animal models. To examine this interaction, we conducted a randomized controlled study using the baboon (Papio anubis) to analyze the effect of chronic schistosomiasis on severe malaria. Two groups of baboons (n = 8 each) and a schistosomiasis control group (n = 3) were infected with 500 Schistosoma mansoni cercariae. At 14 and 15 weeks postinfection, one group was given praziquantel to treat schistosomiasis infection. Four weeks later, the two groups plus a new malaria control group (n = 8) were intravenously inoculated with 10(5) Plasmodium knowlesi parasites and monitored daily for development of severe malaria. A total of 81% of baboons exposed to chronic S. mansoni infection with or without praziquantel treatment survived malaria, compared to only 25% of animals infected with P. knowlesi only (P = 0.01). Schistosome-infected animals also had significantly lower parasite burdens (P = 0.004) than the baboons in the P. knowlesi-only group and were protected from severe anemia. Coinfection was associated with increased spontaneous production of interleukin-6 (IL-6), suggesting an enhanced innate immune response, whereas animals infected with P. knowlesi alone failed to develop mitogen-driven tumor necrosis factor alpha and IL-10, indicating the inability to generate adequate protective and balancing immunoregulatory responses. These results indicate that chronic S. mansoni attenuates the severity of P. knowlesi coinfection in baboons by mechanisms that may enhance innate immunity to malaria.
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.|University of Copenhagen, Copenhagen, Denmark.
authors.forename: Ruth K
authors.initials: RK
authors.lastname: Nyakundi
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Onkoba
authors.initials: O
authors.lastname: Nyamongo
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Jeneby
authors.initials: J
authors.lastname: Maamun
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Mercy
authors.initials: M
authors.lastname: Akinyi
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Isaac
authors.initials: I
authors.lastname: Mulei
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Idle O
authors.initials: IO
authors.lastname: Farah
authors.affiliation: Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: D'Arbra
authors.initials: D
authors.lastname: Blankenship
authors.affiliation: Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Grimberg
authors.affiliation: University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jann
authors.initials: J
authors.lastname: Hau
authors.affiliation: Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Indu
authors.initials: I
authors.lastname: Malhotra
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
authors.forename: Hastings
authors.initials: H
authors.lastname: Ozwara
authors.affiliation: Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: King
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya tkariuki@africaonline.co.ke.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Kariuki
mesh_terms: D000818:Animals; D060085:Coinfection / Q000469:parasitology* / Q000473:pathology*; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D008288:Malaria / Q000473:pathology* / Q000517:prevention & control*; D008297:Male; D010215:Papio; D059208:Parasite Load; D016790:Plasmodium knowlesi / Q000302:isolation & purification; D012550:Schistosoma mansoni / Q000302:isolation & purification; D012552:Schistosomiasis / Q000150:complications* / Q000473:pathology*; D016019:Survival Analysis
chemical_list: D016207:Cytokines