Publications

The increasing prevalence in Southeast Asia of Plasmodium falciparum infections with delayed parasite clearance rates, following treatment of malaria patients with the artemisinin derivative artesunate, highlights an urgent need to identify which of the currently available artemisinin-based combination therapies (ACTs) are most suitable to treat populations with emerging artemisinin resistance. Here, we demonstrate that the rodent Plasmodium berghei SANA strain has acquired artemisinin resistance following drug pressure, as defined by reduced parasite clearance and early recrudescence following daily exposure to high doses of artesunate or the active metabolite dihydroartemisinin. Using the SANA strain and the parental drug-sensitive N strain, we have interrogated the antimalarial activity of five ACTs, namely, artemether-lumefantrine, artesunate-amodiaquine, artesunate-mefloquine, dihydroartemisinin-piperaquine, and the newest combination artesunate-pyronaridine. By monitoring parasitemia and outcome for 30 days following initiation of treatment, we found that infections with artemisinin-resistant P. berghei SANA parasites can be successfully treated with artesunate-pyronaridine used at doses that are curative for the parental drug-sensitive N strain. No other partner drug combination was as effective in resolving SANA infections. Of the five partner drugs tested, pyronaridine was also the most effective at suppressing the recrudescence of SANA parasites. These data support the potential benefit of implementing ACTs with pyronaridine in regions affected by artemisinin-resistant malaria.

Fluorescence optical detection in sedimentation velocity analytical ultracentrifugation allows the study of macromolecules at nanomolar concentrations and below. This has significant promise, for example, for the study of systems of high-affinity protein interactions. Here we describe adaptations of the direct boundary modeling analysis approach implemented in the software SEDFIT that were developed to accommodate unique characteristics of the confocal fluorescence detection system. These include spatial gradients of signal intensity due to scanner movements out of the plane of rotation, temporal intensity drifts due to instability of the laser and fluorophores, and masking of the finite excitation and detection cone by the sample holder. In an extensive series of experiments with enhanced green fluorescent protein ranging from low nanomolar to low micromolar concentrations, we show that the experimental data provide sufficient information to determine the parameters required for first-order approximation of the impact of these effects on the recorded data. Systematic deviations of fluorescence optical sedimentation velocity data analyzed using conventional sedimentation models developed for absorbance and interference optics are largely removed after these adaptations, resulting in excellent fits that highlight the high precision of fluorescence sedimentation velocity data, thus allowing a more detailed quantitative interpretation of the signal boundaries that is otherwise not possible for this system.

BACKGROUND

Growth differentiation factor 15 (GDF-15) is a relatively new biomarker that predicts mortality in patients with chronic stable angina or acute coronary syndrome. However, the association of GDF-15 with cardiovascular (CV) events and the mechanisms of this association are not well understood.

METHODS

We measured plasma GDF-15 and cardiac disease severity in 984 patients with stable ischemic heart disease who were recruited for the Heart and Soul Study between September 2000 and December 2002. Subsequent CV events (myocardial infarction, stroke, and CV death), hospitalization for heart failure, and all-cause mortality were determined by chart review during an average of 8.9-year follow-up.

RESULTS

Each doubling in GDF-15 was associated with a 2.5-fold increased rate of CV events (hazard ratio [HR] 2.53, 95% CI 2.13-3.01, P < .001). This association persisted after extensive adjustment for covariates including comorbid conditions, measures of cardiac disease severity, cardiac function, inflammatory markers, and adipokines (HR 1.44, 95% CI 1.11-1.87, P < .01). Participants who had GDF-15 levels in the highest tertile had higher mortality compared with those in the lowest tertile (HR 2.73, 95% CI 1.80-4.15, P ≤ .001 adjusted for all covariates). Addition of GDF-15 to existing risk factors resulted in a 50% change in net reclassification of patients' risk for mortality.

CONCLUSIONS

Higher levels of GDF-15 are associated with major CV events in patients with stable ischemic heart disease. This suggests that GDF-15 is capturing an element of risk not explained by other known risk factors.