title: Changes in antigen-specific cytokine and chemokine responses to Plasmodium falciparum antigens in a highland area of Kenya after a prolonged absence of malaria exposure.
abstract: Individuals naturally exposed to Plasmodium falciparum lose clinical immunity after a prolonged lack of exposure. P. falciparum antigen-specific cytokine responses have been associated with protection from clinical malaria, but the longevity of P. falciparum antigen-specific cytokine responses in the absence of exposure is not well characterized. A highland area of Kenya with low and unstable malaria transmission provided an opportunity to study this question. The levels of antigen-specific cytokines and chemokines associated in previous studies with protection from clinical malaria (gamma interferon [IFN-γ], interleukin-10 [IL-10], and tumor necrosis factor alpha [TNF-α]), with increased risk of clinical malaria (IL-6), or with pathogenesis of severe disease in malaria (IL-5 and RANTES) were assessed by cytometric bead assay in April 2008, October 2008, and April 2009 in 100 children and adults. During the 1-year study period, none had an episode of clinical P. falciparum malaria. Two patterns of cytokine responses emerged, with some variation by antigen: a decrease at 6 months (IFN-γ and IL-5) or at both 6 and 12 months (IL-10 and TNF-α) or no change over time (IL-6 and RANTES). These findings document that P. falciparum antigen-specific cytokine responses associated in prior studies with protection from malaria (IFN-γ, TNF-α, and IL-10) decrease significantly in the absence of P. falciparum exposure, whereas those associated with increased risk of malaria (IL-6) do not. The study findings provide a strong rationale for future studies of antigen-specific IFN-γ, TNF-α, and IL-10 responses as biomarkers of increased population-level susceptibility to malaria after prolonged lack of P. falciparum exposure.
authors: Department of Biomedical Sciences and Technology, School of Public Health and Community Development, Maseno University, Maseno, Kenya Kenya Medical Research Institute (KEMRI)-University of Minnesota Malaria Project, Center for Global Health Research, KEMRI, Kisumu, Kenya.
authors: Lyticia A
authors: LA
authors: Ochola
authors: Kenya Medical Research Institute (KEMRI)-University of Minnesota Malaria Project, Center for Global Health Research, KEMRI, Kisumu, Kenya Department of Zoology, Faculty of Science, Maseno University, Maseno, Kenya.
authors: Cyrus
authors: C
authors: Ayieko
authors: Department of Immunology, School of Medicine, Moi University, Eldoret, Kenya.
authors: Lily
authors: L
authors: Kisia
authors: Department of Medical Physiology, School of Medicine, Maseno University, Maseno, Kenya.
authors: Ng'wena G
authors: NG
authors: Magak
authors: Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors: Estela
authors: E
authors: Shabani
authors: Department of Biomedical Sciences and Technology, School of Public Health and Community Development, Maseno University, Maseno, Kenya.
authors: Collins
authors: C
authors: Ouma
authors: Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA ccj@umn.edu.
authors: Chandy C
authors: CC
authors: John
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000953:Antigens, Protozoan / Q000276:immunology*; D018925:Chemokines / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology; D016753:Interleukin-10 / Q000276:immunology; D015848:Interleukin-5 / Q000276:immunology; D007630:Kenya; D016778:Malaria, Falciparum / Q000276:immunology*; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D055815:Young Adult
chemical_list: D000953:Antigens, Protozoan; D018925:Chemokines; D016207:Cytokines; D015848:Interleukin-5; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D007371:Interferon-gamma