Distinct Biomarker Profiles Distinguish Malawian Children with Malarial and Non-malarial Sepsis

Increased interleukin-6 levels associated with malaria infection and disease severity: a systematic review and meta-analysis

Interleukin-6 (IL-6) is generated by immune cells during infection with malaria parasites and they are associated with the immunopathogenesis of malaria. The present systematic review and meta-analysis aimed to compare the differences in IL-6 levels between several groups of patients with malaria and healthy control groups. The systematic review was registered at PROSPERO with a registration number: CRD42021290753. Systematic literature searches were conducted in PubMed, Web of Science, and Scopus until November 7, 2021 to obtain studies that documented IL-6 levels in patients with malaria. The quality of the included studies was assessed using critical appraisal tools from the Joanna Briggs Institute. Differences in the mean IL-6 levels among patients with: (1) severe and non-severe malaria, (2) uncomplicated malaria and controls, (3) uncomplicated and asymptomatic malaria, (4) asymptomatic malaria and healthy controls, and (5) those that died or survived were estimated using a random-effects model. Forty-three of 1,969 studies were included in the systematic review. Results of the meta-analysis showed that patients with severe malaria had higher mean IL-6 levels than those with non-severe malaria [P = 0.04, weight mean difference (WMD) = 96.63 pg/mL, 95% confidence interval (CI) = 0.88 − 19.38 pg/mL, I² = 99.9%, 13 studies]. Patients with uncomplicated malaria had higher mean IL-6 levels than the controls (P < 0.001, WMD = 42.86 pg/mL, 95% CI = 30.17 − 55.56 pg/mL, I² = 100%, 17 studies). No differences in the mean levels of IL-6 were found between patients with uncomplicated malaria and those with asymptomatic malaria (P = 0.063, WMD = 42.07 pg/mL, 95% CI =  − 2.23 pg/mL to − 86.37 pg/mL, I² = 99.1%, 8 studies), or between patients with asymptomatic malaria and healthy controls (P = 0.45, WMD = 1.67 pg/mL, 95% CI =  − 2.73 pg/mL to − 6.07 pg/mL, I² = 98.1%, 2 studies). A higher mean level of IL-6 was observed in patients who died compared with the levels of those who survived (P = 0.007, WMD = 1,399.19 pg/mL, 95% CI = 384.16 − 2,414.2 pg/mL, I² = 93.1%, 4 studies). Our meta-analysis of the pooled evidence can be used to guide future studies in which IL-6 levels are measured during malaria outbreaks to monitor malaria severity. Heterogeneity of the effect estimate among the included studies was the main limitation of this analysis. In conclusion, significantly increased levels of IL-6 were observed in patients with severe malaria compared with those in patients with non-severe malaria, which indicates that IL-6 is a candidate marker for severe malaria. Future studies should investigate the sensitivity and specificity of increased IL-6 levels to determine the effectiveness of assessments of IL-6 levels monitoring of malaria infection and severity.

Malaria-induced bacteremia as a consequence of multiple parasite survival strategies

Globally, malaria continues to be an enormous public health burden, with concomitant parasite-induced damage to the gastrointestinal (GI) barrier resulting in bacteremia-associated morbidity and mortality in both adults and children. Infected red blood cells sequester in and can occlude the GI microvasculature, ultimately leading to disruption of the tight and adherens junctions that would normally serve as a physical barrier to translocating enteric bacteria. Mast cell (MC) activation and translocation to the GI during malaria intensifies damage to the physical barrier and weakens the immunological barrier through the release of enzymes and factors that alter the host response to escaped enteric bacteria. In this context, activated MCs release Th2 cytokines, promoting a balanced Th1/Th2 response that increases local and systemic allergic inflammation while protecting the host from overwhelming Th1-mediated immunopathology. Beyond the mammalian host, recent studies in both the lab and field have revealed an association between a Th2-skewed host response and success of parasite transmission to mosquitoes, biology that is evocative of parasite manipulation of the mammalian host. Collectively, these observations suggest that malaria-induced bacteremia may be, in part, an unintended consequence of a Th2-shifted host response that promotes parasite survival and transmission. Future directions of this work include defining the factors and mechanisms that precede the development of bacteremia, which will enable the development of biomarkers to simplify diagnostics, the identification of therapeutic targets to improve patient outcomes and better understanding of the consequences of clinical interventions to transmission blocking strategies.

Novel Biomarkers Differentiating Viral from Bacterial Infection in Febrile Children: Future Perspectives for Management in Clinical Praxis

Differentiating viral from bacterial infections in febrile children is challenging and often leads to an unnecessary use of antibiotics. There is a great need for more accurate diagnostic tools. New molecular methods have improved the particular diagnostics of viral respiratory tract infections, but defining etiology can still be challenging, as certain viruses are frequently detected in asymptomatic children. For the detection of bacterial infections, time consuming cultures with limited sensitivity are still the gold standard. As a response to infection, the immune system elicits a cascade of events, which aims to eliminate the invading pathogen. Recent studies have focused on these host–pathogen interactions to identify pathogen-specific biomarkers (gene expression profiles), or “pathogen signatures”, as potential future diagnostic tools. Other studies have assessed combinations of traditional bacterial and viral biomarkers (C-reactive protein, interleukins, myxovirus resistance protein A, procalcitonin, tumor necrosis factor-related apoptosis-inducing ligand) to establish etiology. In this review we discuss the performance of such novel diagnostics and their potential role in clinical praxis. In conclusion, there are several promising novel biomarkers in the pipeline, but well-designed randomized controlled trials are needed to evaluate the safety of using these novel biomarkers to guide clinical decisions.

C-Reactive Protein for the Early Assessment of Non-Malarial Febrile Patients: A Retrospective Diagnostic Study

Biomarkers, especially CRP, have demonstrated their relevance to differentiate viral from bacterial infection, even though a reliable threshold is far to being found. In low- and middle-income countries, affordable and user-friendly rapid diagnostic tests based on biomarkers can be widely adopted to help health workers in the management of non-malarial fever. The primary objective of this study is to assess the best CRP cut-off to distinguish viral from bacterial infections. Other biomarkers were evaluated for the same purpose, alone or in combination with CRP. We retrospectively collected data from two referral hospital departments for infectious and tropical diseases in Italy. Areas under the ROC curve (AUC) were calculated and then compared using the DeLong test. Overall, we included 1193 febrile cases (viral 20.74% vs. bacterial 79.25%). We also collected malaria (n = 202) and intestinal parasite (n = 186) cases to establish their impact on biomarkers. CRP had the best accuracy in differentiating viral from bacterial infections. The best performance of CRP was a cut-off of 11 mg/L. All other biomarkers studied had significantly lower accuracy. Median CRP values were within the normal ranges in parasitic infections, while they were higher in malaria. None of the combinations of CRP with other biomarkers significantly increased the accuracy of CRP alone.

Usefulness of C-Reactive Protein and Other Host BioMarker Point-of-Care Tests in the Assessment of Non-Malarial Acute Febrile Illnesses: A Systematic Review with Meta-Analysis

In low- and middle-income countries, in resource-limited settings, the implementation of diagnostic tools discriminating bacterial from nonbacterial fever is a matter of primary concern. The introduction of malaria rapid diagnostic tests highlighted the need for point-of-care tests (POCTs) supporting clinical decision-making for non-malarial febrile illnesses. The purpose of this work was to review the use of host biomarker POCTs for the assessment of acute non-malarial fever in resource-constraint settings. Specific objectives were as follows: 1) to estimate the accuracy of such tests in differentiating fever of bacterial from nonbacterial origin and 2) to assess the impact of host biomarkers on antibiotic prescription and clinical outcome. We conducted a systematic review searching PubMed, Embase, the Cochrane Library, and Bireme. The protocol was registered with PROSPERO (n CRD42019141735). Data on the accuracy of C-reactive protein (CRP) for the detection of bacterial infections were meta-analyzed using the hierarchical summary receiver operating characteristic model, obtaining a summary ROC (SROC). We identified 2,192 articles, eight of which were included in the review. Among the different biomarkers evaluated, CRP was the one most frequently studied. The SROC presented an area under the curve = 0.77 (CI: 0.73-0.81), which indicates good accuracy to distinguish bacterial from nonbacterial infections. However, the optimal cutoff of CRP could not be assessed, and we found insufficient evidence about its impact on antibiotic prescription and clinical outcome. The role of CRP and other host biomarker POCTs for the assessment of acute non-malarial febrile illnesses in resource-constraint settings deserves further studies.