Relevance of Plasmodium falciparum Biomarkers in the Treatment and Control of Malaria

Abstract

We report here a dual-ELISA method to measure Malaria biomarkers concurrently in the same aliquot of blood sample. A correlation between the parasite numbers and ELISA values determined and the figures were used to establish a standard graph. Thick blood smears prepared from spiked blood samples were also Giemsa stained and parasite density determined by microscopy (It was thereby possible to undertake an objective comparison between lactate dehydrogenase and histidine- rich- proteins levels assessed by ELISA and parasite density determined by microscopy from the same spiked aliquot). The presence of lactate dehydrogenase and histidine- rich- proteins is localized and visualized by fluorescent antibody techniques. Twenty-two patient blood samples were retrospectively analyzed for the levels of pLDH and HRPs and their level was quantified in each blood sample. Fresh blood samples from malaria patients seeking care at a healthcare facility in an endemic area were then collected and separated into plasma and infected red blood cells and parasitemia levels determined. The biomarkers which were released into plasma from circulating and sequestered parasites provide a more accurate picture and indicate degree of disease severity. Since lactate dehydrogenase is known to have a short half-life compared to the histidine-rich proteins, its plasma level is believed to reflect on the number of metabolically active parasites more accurately and more reliable indicator of clinical outcome. In contrast, histidine -rich proteins accumulate in plasma and measurable levels persist long after patients have been treated and parasites cleared from their system. Best practice may now call for a pre-eminent role for microscopy and PCR in plasmodium species confirmation, a continued role for newer histidine-rich protein assays in epidemiological studies and control, and the preferential use of parasite lactate dehydrogenase in the clinical management of the disease. Data presented here from spiked blood samples as well as naturally infected patient samples provide evidence that by splitting whole blood samples into RBC-pellet and plasma, determination of parasite biomarkers in split sample fractions gives a true picture of malaria parasites present in humans and this may improve the accuracy of models that attempt to predict parasite burdens more accurately, and so clinical correlations.