Human herpesvirus-6 and liver transplantation

Acute hepatitis with periportal confluent necrosis associated with human herpesvirus 6 infection in liver transplant patients

OBJECTIVES

To correlate human herpesvirus 6 (HHV-6) viral load with pathologic features in graft acute hepatitis of unknown origin.

METHODS

Liver frozen samples from 26 patients with graft hepatitis of unknown origin were available for HHV-6 DNA quantification.

RESULTS

In 10 (38.5%) of 26 liver samples, HHV-6 DNA was detectable, with a median viral load of 3.84 log10 copies/10⁶ cells. Confluent periportal necrosis was observed in 4 of 10 patients and associated with high viral load. These 4 patients responded to antiviral therapy. Mild unspecific hepatitis was observed in 4 patients with low intragraft viral load and in 2 patients with high viral load in a context of deep immunosuppression. Patients with HHV-6-negative graft hepatitis disclosed lobular necrotico-inflammatory activity without periportal necrosis.

CONCLUSIONS

Our study provides data supporting the pathogenic role of HHV-6 for liver allografts. The presence of confluent periportal necrosis could be a clue for prompt diagnosis of HHV-6-induced graft hepatitis.

Overview: cytomegalovirus and the herpesviruses in transplantation

Herpesviruses infect most animal species. Infections due to the eight human herpesviruses (HHV) are exacerbated by immunosuppression in organ transplantation. The special features of the herpesvirus life cycle include the ability to establish latent, nonproductive infection and the life-long capacity for reactivation to productive, lytic infection. Interactions between latent virus and the immune system determine the frequency and severity of symptomatic infections. The immunologic and cellular effects of herpesvirus infections contribute to risk for opportunistic infections and graft rejection. Among the most important advances in transplantation are laboratory assays for the diagnosis and monitoring of herpesvirus infections and antiviral agents with improved efficacy in prophylaxis and therapy. For herpes simplex virus, varicella zoster virus and cytomegalovirus, these advances have significantly reduced the morbidity of infection. The syndromes of EBV-associated posttransplant lymphoproliferative disorders (PTLD) and Kaposi's sarcoma remain important complications of immunosuppression. The epidemiology and essential biology of human herpesvirus is reviewed.