A Metabolite-Based Resistance Mechanism Against Malaria.

Whether jaundice, a common presentation of ( .) malaria (1-3) arising from the accumulation of circulating bilirubin, represents an adaptive or maladaptive response to spp. infection is not understood (1-3). We found that asymptomatic infection was associated with a >10-fold higher ratio of unconjugated bilirubin over parasite burden, compared to symptomatic malaria. Genetic suppression of bilirubin synthesis by biliverdin reductase A (BVRA) (4) increased parasite virulence and malaria mortality in mice. Accumulation of unconjugated bilirubin in plasma, via genetic inhibition of hepatic conjugation by UDP glucuronosyltransferase family 1 member A1 (UGT1A1) ( ), was protective against malaria in mice. Unconjugated bilirubin inhibited proliferation in red blood cells (RBC) via a mechanism that suppressed mitochondrial pyrimidine synthesis. Moreover, unconjugated bilirubin inhibited hemozoin (Hz) crystallization and compromised the parasite's food vacuole. In conclusion, jaundice represents a metabolic response to . infection that limits malaria severity.