Hepatitis E virus infection (HEV) is a major cause of acute viral hepatitis in the developing world. The immunopathology of HEV infections has not yet been elucidated. The virus is noncytopathic, and therefore, liver injury may be attributed to immune-mediated damage by cytotoxic T cells and natural killer cells. Therefore, we studied the nature of immune cells involved in HEV-induced liver damage using immunohistochemistry in liver biopsies taken from patients with HEV-induced acute liver failure and demonstrated a significant infiltration of activated CD8(+) T cells containing granzymes. These findings suggest the possible involvement of cytotoxic T cells in disease pathogenesis during HEV infection.

BACKGROUND Hepatitis E virus (HEV) is a virus of emerging importance to transfusion medicine as studies on blood donors and other populations demonstrate that the prevalence of endemic cases is higher than previously recognized and the risk to vulnerable transfusion recipients is not insignificant. STUDY DESIGN AND METHODS We carried out an HEV prevalence study on 13,993 Canadian blood donors with polymerase chain reaction (PCR) testing on all donors and antibody testing on a subset of 4102 donors. HEV antibody–positive and age‐ and sex‐matched antibody‐negative donors were invited to participate in a scripted telephone interview about risk factors. RESULTS There were no PCR‐positive samples found (95% confidence interval [CI], 0%‐0.026%). The seroprevalence of HEV in our tested population was 5.9% (95% CI, 5.16%‐6.59%). HEV antibody positivity was associated with male sex and increasing age. In case‐control analysis history of living outside Canada (odds ratio [OR], 2.9; 95% CI, 1.56‐5.32) and contact with farm animals (OR, 1.5; 95% CI, 1.01‐2.28) were associated with HEV seropositivity. CONCLUSION This is the largest data set to date on HEV infection in Canada. Results suggest low lifetime exposure to HEV and that infectious donations are rare.