Metabolomic analysis of urine samples of vivax malaria in-patients for biomarker identification

Plasmodium vivax is the most dominating species in the Indian subcontinent among the five Plasmodium species causing malarial infection in humans. This species is generally believed to be benign and classically thought to cause uncomplicated clinical infection that rarely leads to death or other complication. However, recent studies have shown incidences of P. vivax infection leading to severe complications and even death. To understand the biochemical changes at the pathway level and the modality through which the host recovers from the infection, we monitored the small molecular weight metabolites of urine samples of hospital in-patients undergoing treatment for vivax malaria. Metabolomics, involving H-1 NMR spectra of urine samples subjected to multivariate statistical analyses, was employed for this purpose. Urine metabolic profiles were used to identify putative biomarkers and establishing correlation with parasite count in the peripheral blood. The untreated malaria patients (day1) exhibited altered excretion of taurine, hippurate, citrate, glycine, 3-methylhistidine and alanine in comparison to the self-control profile on day30. The day1-4 urine metabolite profiles are distinct from day5 and day30 profiles. The latter two profiles are indistinguishable. Temporal trajectories of urinary metabolites indicated an inflection point on day3. The day1 H-1 NMR profiles, distinct from the profiles of viral fever patients, correlated with the parasitemia levels in the patients and could in fact be used to gauge the anemia status of the patients. This study demonstrates the potential of urine metabolic profiling in understanding the pathophysiology of P. vivax infection and in non-invasive disease diagnosis.