HDV LACKING HBV CAN INFECT HUMAN HEPATOCYTES IN THE LIVER OF CHIMERIC uPA/SCID MICE AND PERSIST FOR AT LEAST SIX WEEKS BEFORE BEING RESCUED BY SUPERINFECTION WITH HBV

Aims: HDV replication leads to RNA-editing, accumulation of the large HDAg,down-regulation of RNA accumulation and appearance of non-infectious HDV RNAs.However, clinical studies show that HDV can replicate at high levels in infected humansfor years in the setting of low HBV replication. Aim of this study was to determinewhether HDV replication and accumulation can persist in the absence of HBV andwhether infectious HDV can be rescued by super-infection with HBV. Methods: HDV,lacking HBV, was assembled in transfected cells, concentrated, and used to infect 9human chimeric uPA/SCID mice (50μl at 10E8 copies/ml per mouse). After 3 (n=3) or6 weeks (n=3) mice were super-infected with patient-derived HBV-DNA positive serum(30μl at 10E8 copies/ml), while 3 mice were sacrificed to ascertain establishment ofHDV mono-infection. Serological and intrahepatic viral loads were measured by qRTPCR.Presence of HBsAg, HBcAg, HDAg and cell death (TUNEL, Anti-Caspase3)was ascertained by immunohistochemistry. Results: HDAg was detected in 0.1–1% ofhuman hepatocytes in mice sacrificed 3 weeks post HDV inoculation (n=3). FollowingHBV super-infection, development of HBV and HDV viremias (up to 10E7 HBV-DNAand 10E8 HDV-RNA copies/ml) were observed in all mice. The increase of HDAgpositivehuman hepatocytes in livers of mice sacrificed 15 weeks post HDV infectionshowed not only survival but also in vivo spreading of HDV. Cell death markers werenegative in HDV mono-infected human hepatocytes, indicating that intracellular HDVreplication did not cause evident hepatocyte death. Conclusions: HDV particles,lacking HBV, were not only able to infect human hepatocytes in vivo, but could persistintrahepatically for at least 6 weeks before being rescued by HBV super-infection.Our findings suggest that efficient conversion of a latent HDV mono-infection to aproductive HBV/HDV co-infection may contribute to the persistence of HDV even inpatients with low HBV replication.

HBV - HDV - uPA/SCID