Cytokine profiles in adults with imported malaria: insights from the PALUREA cohort study

The increase in worldwide travel is making imported malaria a growing health concern in nonendemic countries. Most data on the pathophysiology of malaria come from endemic areas. Little is known about cytokine profiles during imported malaria. We report cytokine profiles in adults with Plasmodium falciparum malaria included in PALUREA, a prospective cohort study conducted in France between 2006 and 2010. The patients were classified as having uncomplicated malaria (UM) or severe malaria (SM), with this last further categorized as very severe malaria (VSM) or less severe malaria (LSM). At hospital admission, eight blood cytokines were assayed in duplicate using Luminex technology: interleukin (IL)-1, IL-1{beta}, IL-2, IL-4, IL-10, tumor necrosis factor (TNF), interferon (IFN){gamma}, and macrophage migration inhibitory factor (MIF). These assays were repeated on days 1 and 2 in the SM group. Of the 278 patients, 134 had UM and 144 SM. At hospital admission, over half the patients had undetectable levels of IL-1, IL-1 {beta}, IL-2, IL-4, IFN {gamma}, and TNF, while IL-10 and MIF were significantly higher in the SM vs. the UM group. Higher IL-10 was significantly associated with higher parasitemia (R=0.32 [0.16-0.46]; P=0.0001). In the SM group, IL-10 elevation persisting from admission to day 2 was significantly associated with subsequent nosocomial infection. Of eight tested cytokines, only MIF and IL-10 were associated with disease severity in adults with imported P. falciparum malaria. At admission, many patients had undetectable cytokine levels, suggesting that circulating cytokine assays may not be helpful as part of the routine evaluation of adults with imported malaria. Author SummaryPlasmodium falciparum malaria is increasingly common in nonendemic areas. Improved understanding of its pathophysiology might help to decrease mortality. We therefore routinely assayed eight cytokines in 278 adults with imported P. falciparum malaria at hospital admission; in the group with severe malaria (n=144), we repeated the assays on the next two days. The cytokine levels were often undetectable, suggesting that cytokine storm might not be a driving mechanism at the time of clinical presentation. IL-10 and macrophage migration inhibitory factor (MIF) were significantly higher in the group with severe vs. uncomplicated disease. Thus, the roles for these two cytokines in severe malaria, may deserve further investigation. A complicating factor is that greater IL-10 elevation may be a response to a heavy parasite burden and/or may promote parasite replication. IL-10 elevation that persisted over the first 2 days after admission was significantly associated with subsequent nosocomial infections in the group with severe malaria suggesting its possible role in acquired immune suppression syndrome.