Reappearance of hepatitis D virus (HDV) replication in chronic hepatitis B virus carrier chimpanzees rechallenged with HDV.

Four chronic hepatitis B virus (HBV) carrier chimpanzees, which had apparently cleared hepatitis D virus (HDV) after a first experimental challenge with HDV, were reinoculated with a homologous strain of HDV. All animals had reappearance of low levels of serum HDV RNA and transient, mild alanine aminotransferase (ALT) elevations, which in two cases correlated with HDV RNA positivity. Plasmas obtained from two chimpanzees after rechallenge were inoculated into two other chronic HBV carrier animals that had recovered from a previous HDV infection. A similar reappearance of HDV RNA in serum (without ALT elevation) was noticed. These same plasmas, however, when inoculated into a chronic HBV carrier chimpanzee never exposed to HDV caused a severe acute hepatitis D. Rechallenge with HDV in chimpanzees apparently recovered from a first HDV infection resulted in the reappearance of HDV replication, sometimes associated with hepatitis. This can be interpreted as reinfection with HDV, but other explanations are possible. Although the serum level of HDV RNA observed after rechallenge with HDV is low, its transmission to individuals susceptible to HDV infection can result in severe acute hepatitis D.