Yellow fever (YF) is a
viral hemorrhagic fever that typically involves the liver. Brazil recently experienced its largest recorded YF outbreak, and the disease was fatal in more than a third of affected individuals, mostly because of
acute liver failure. Affected individuals are generally treated only supportively, but during the recent Brazilian outbreak, selected patients were treated with
liver transplant. We took advantage of this clinical experience to better characterize the clinical and pathological features of YF-induced
liver failure and to examine the mechanism of hepatocellular injury in YF, to identify targets that would be amenable to therapeutic intervention in preventing progression to
liver failure and death. Patients with YF
liver failure rapidly developed massive
transaminase elevations, with
jaundice, coagulopathy,
thrombocytopenia, and usually
hepatic encephalopathy, along with pathological findings that included microvesicular steatosis and lytic
necrosis. Hepatocytes began to express the type 3
isoform of the
inositol trisphosphate receptor (ITPR3), an intracellular
calcium (Ca2+) channel that is not normally expressed in hepatocytes. Experiments in an animal model, isolated hepatocytes, and liver-derived cell lines showed that this new expression of ITPR3 was associated with increased nuclear Ca2+ signaling and hepatocyte proliferation, and reduced steatosis and cell death induced by the YF virus. Conclusion:
Yellow fever often induces
liver failure characterized by massive hepatocellular damage plus steatosis. New expression of ITPR3 also occurs in YF-infected hepatocytes, which may represent an endogenous protective mechanism that could suggest approaches to treat affected individuals before they progress to
liver failure, thereby decreasing the mortality of this disease in a way that does not rely on the costly and limited resource of
liver transplantation.