Serum Angiopoietin-1 and -2 Levels Discriminate Cerebral Malaria from Uncomplicated Malaria and Predict Clinical Outcome in African Children

BACKGROUND: Limited tools exist to identify which individuals infected with Plasmodium falciparum are at risk of developing serious complications such as cerebral malaria (CM). The objective of this study was to assess serum biomarkers that differentiate between CM and non-CM, with the long-term goal of developing a clinically informative prognostic test for severe malaria. METHODOLOGY/PRINCIPAL FINDINGS: Based on the hypothesis that endothelial activation and blood-brain-barrier dysfunction contribute to CM pathogenesis, we examined the endothelial regulators, angiopoietin-1 (ANG-1) and angiopoietin-2 (ANG-2), in serum samples from P. falciparum-infected patients with uncomplicated malaria (UM) or CM, from two diverse populations--Thai adults and Ugandan children. Angiopoietin levels were compared to tumour necrosis factor (TNF). In both populations, ANG-1 levels were significantly decreased and ANG-2 levels were significantly increased in CM versus UM and healthy controls (p<0.001). TNF was significantly elevated in CM in the Thai adult population (p<0.001), but did not discriminate well between CM and UM in African children. Receiver operating characteristic curve analysis showed that ANG-1 and the ratio of ANG-2:ANG-1 accurately discriminated CM patients from UM in both populations. Applied as a diagnostic test, ANG-1 had a sensitivity and specificity of 100% for distinguishing CM from UM in Thai adults and 70% and 75%, respectively, for Ugandan children. Across both populations the likelihood ratio of CM given a positive test (ANG-1<15 ng/mL) was 4.1 (2.7-6.5) and the likelihood ratio of CM given a negative test was 0.29 (0.20-0.42). Moreover, low ANG-1 levels at presentation predicted subsequent mortality in children with CM (p = 0.027). CONCLUSIONS/SIGNIFICANCE: ANG-1 and the ANG-2/1 ratio are promising clinically informative biomarkers for CM. Additional studies should address their utility as prognostic biomarkers and potential therapeutic targets in severe malaria

Purified Vero cell rabies vaccine and human diploid cell strain vaccine: comparison of neutralizing antibody responses to post-exposure regimens.

Neutralizing antibody responses to conventional rabies post-exposure regimens of human diploid cell strain vaccine (HDCSV) and the new purified Vero cell rabies vaccine (PVRV) were compared in 58 healthy Thai veterinary students. The geometric mean titres (GMTs) of the group given HDCSV were slightly higher than those given PVRV, but on day 28 the peak GMTs of the two groups were statistically similar. The early antibody response to PVRV was unaffected by the addition of passive immunization, whereas the level of HDCSV response was reduced on day 14, so that there was no difference on that day between the GMTs of the two vaccine groups given HRIG. However, by day 91 the GMT of those given PVRV and HRIG was lower than in those given HDCSV alone or with HRIG. The appearance of antibody was less rapid than was observed in previous studies using multiple-site intradermal vaccination. Side effects were trivial. Our results confirm the promise of this new, potentially more economical tissue culture vaccine, but they suggest that the regimen could be improved

Results of a multivariate logistic regression model to predict CM (versus UM) in two diverse patient populations.

*<p>baseline comparator group.</p>**<p>Adjusted odds ratio represents the incremental odds of CM for every unit increase (1 ng/mL) in the ANG-1 level.</p

Optimal cut-off values (95% CI) for each test and sensitivity (SEN), specificity (SPEC), positive likelihood ratio (LR(+)) and negative likelihood ratio (LR(−)) at the chosen cut-off value comparing uncomplicated malaria with cerebral malaria patients.

*<p>significantly different from 1 (p<0.05).</p

Biomarker levels in serum of healthy controls (HC), uncomplicated malaria patients (UM) and cerebral malaria patients (CM) from adult Thai patients and pediatric Ugandan patients.

<p>Values are presented as median (range).</p

Comparison of angiopoeitin-1 and -2 levels with TNF in adult malaria patients from Thailand.

<p>A. Serum concentrations of angiopoietin-1 (ANG-1), angiopoietin-2 (ANG-2), the ratio of ANG-2∶ANG-1 (RATIO, expressed as log base 10) and tumour necrosis factor (TNF) were measured in 10 healthy controls (HC), 25 consecutive uncomplicated malaria (UM) patients, and in consecutive 25 cerebral malaria (CM) patients. B. Receiver operating characteristic curves (blue line) were generated for each test to compare CM with UM patients, with the null hypothesis (green line) that area under the curve equals 0.5.</p