Pro‐inflammatory cytokines induced by glycosylphosphatidylinositols (GPIs) of Plasmodium falciparum contribute to malaria pathogenesis and hence, the naturally acquired anti‐GPI antibody thought to provide protection against severe malaria (SM) by neutralizing the stimulatory activity of GPIs. In previous studies, the anti‐GPI antibody levels increased with age in parallel with the development of acquired immunity, and high levels of anti‐GPI antibodies were associated with mild malaria (MM) cases. In the present study, the relationship between the levels of pro‐inflammatory cytokines and anti‐GPI IgG antibody responses, parasitemia, and the clinical outcomes were evaluated in SM and mild malaria (MM) patients. Sera from a total of 110 SM and 72 MM cases after excluding of ineligible patients were analyzed for the levels of anti‐GPI antibodies, IgG subclasses, and cytokine responses by ELISA. While the total anti‐GPI antibody levels were similar in overall SM and MM groups, they were significantly higher in surviving SM patients than in fatal SM cases. In the case of cytokines, the TNF‐α and IL‐6 levels were significantly higher in SM compared to MM, whereas the IL‐10 levels were similar in both groups. The data presented here demonstrate that high levels of the circulatory pro‐inflammatory, TNF‐α, and IL‐6, are indicators of malaria severity, whereas anti‐inflammatory cytokine IL‐10 level does not differentiate SM and MM cases. Further, among SM patients, relatively low levels of anti‐GPI antibodies are indicators of fatal outcomes compared to survivors, suggesting that anti‐GPI antibodies provide some level of protection against SM fatality.

Merozoite surface proteins (MSPs) are critical for parasite invasion; they represent attractive targets for antibody-based protection against clinical malaria. To identify protection-associated target MSPs, the present study analysed antibody responses to whole merozoite extract (ME) and to defined MSP recombinant antigens in hospitalized patients from a low endemic urban area as a function of disease severity (mild versus cerebral malaria). Sera from 110 patients with confirmed severe cerebral malaria (CM) and 91 patients with mild malaria (MM) were analysed (mean age = 29 years) for total and subclass immunoglobulin (Ig)G to ME and total IgG to MSP1p19, MSP2, MSP3, MSP4 and MSP5 by enzyme-linked immunosorbent assay (ELISA). Functional antibody responses were evaluated using the antibody-dependent respiratory burst (ADRB) assay in a subset of sera. There was a trend towards higher IgG1 and IgG4 levels to ME in CM compared to MM; only ME IgM responses differed significantly between fatal and surviving CM patients. Increased prevalence of IgG to individual MSPs was found in the CM compared to the MM group, including significantly higher levels of IgG to MSP4 and MSP5 in the former. Sera from fatal (24·5%) versus surviving cases showed significantly lower IgG to MSP1p19 and MSP3 (P < 0·05). ADRB assay readouts correlated with high levels of anti-MSP IgG, and trended higher in sera from patients with surviving compared to fatal CM outcome (P = 0·07). These results document strong differential antibody responses to MSP antigens as targets of protective immunity against CM and in particular MSP1p19 and MSP3 as prognostic indicators.

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P. falciparum malaria continues as the serial killer of over a million lives yearly, mainly for children in sub-Saharan Africa. For severe malaria, we are still on the quest for a prognostic marker of fatal outcome. We analysed the association between serum levels of Procalcitonin (PCT), a marker of septic inflammation, and clinical outcome in Senegalese patients admitted with confirmed cerebral malaria in the intensive care facility of Hopital Principal. A total of 98 patients living in the hypoendemic urban area of Dakar, Senegal, were enrolled during transmission seasons. Levels of PCT were compared between surviving vs the 26.5 % fatal cases in blood samples of the 3 days following hospitalisation. Mean PCT levels were elevated in patients with active infection, with a large range of values (0.1 to 280 nanog per mL), significantly higher on day 0 in fatal cases than in surviving (53.6 vs 27.3; P=0.01). No exact individual threshold level could indicate occurrence of fatality, however mortality could be most accurately predicted by PCT level above 69 nanog per ML and there was a very clear different profile of evolution of PCT levels on the 3 days of observation decreasing early from day 1 in surviving patients (P<10–3), contrary to fatal cases. These results indicate that PCT kinetic rather than intrinsic level could be of use to predict a reduced risk of fatality in patient with cerebral malaria and could serve as potential predicting marker for severe malaria

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