Novel Woodchuck Hepatitis Virus (WHV) Transgene Mouse Models Show Sex-Dependent WHV Replicative Activity and Development of Spontaneous Immune Responses to WHV Proteins

Abstract

HBV has a very narrow host range and can infect only humans and higher primates such as chimpanzees (3, 4). However, experiments using chimpanzees are costly and require both scientific and ethical justification. HBV transgenic (Tg) mice have allowed examination of the influence of viral and host factors on HBV pathogenesis and replication and assessment of the antiviral potential of pharmacological agents (5). For example, the transfer of HBsAg-specific CD8 ϩ T cells into these mice led to the inhibition of HBV replication in the liver by a noncytolytic mechanism (6), leading to the important hypothesis that the antiviral cytokines IFN-␥ and tumor necrosis factor alpha are major mediators of noncytolytic inhibition of HBV replication (7). Furthermore, activation of innate immune responses in HBV Tg mice by Toll-like receptor (TLR) ligands also inhibits HBV replication (8). Thus, the HBV Tg mouse model was and remains a useful research tool to study HBV infection. However, as HBV Tg mice are immunologically tolerant to HBV proteins (5, 9), obvious disease-related phenotypes have not been observed. On the other hand, HBsAg is supposed to play an important role in HBV persistence and hepatocarcinogenesis (10). The presence of HBsAg may inhibit host immune responses and facilitate HBV persistence (11, 12). Therefore, transgenic mice replicating HBV but lacking small HBs expression represent an interesting model for studies of the role of HBsAg in HBV persistence, hepatocarcinogenesis, and antiviral immune responses (13).Woodchuck hepatitis virus (WHV) is a member of the Hepadnaviridae family and was discovered in 1978 (14). WHV causes acute and chronic infections in woodchucks (Marmota monax) similar to HBV infections in humans. The woodchuck model has been proven to be an informative model for studies of hepadnaviral infection and pathogenesis and for the screening and development of antiviral drugs (15). Despite the establishment of immunological assays and tools for the woodchuck model during the last years, immunological studies in outbred and immunogenetically uncharacterized woodchucks are still difficult (16,17). Therefore, it was desirable to have a WHV Tg mouse model that would allow the determination of immunological parameters and complement infection experiments in woodchucks.In the present study, we report the establishment of two WHV Tg mouse strains, one with a wild-type WHV genome and the other with a WHV genome harboring artificially introduced stop codons in the coding region of WHV surface anti-

Low hepatitis B virus–specific T‐cell response in males correlates with high regulatory T‐cell numbers in murine models

“…We recently showed that therapeutic vaccination elicits potent CD8 + T‐cell responses and reduces WHV replication in 1217 Wtg mice . We also observed gender‐related differences in WHV replication in these Tg mice . Therefore, we chose this mouse model to study the impact of gender on the efficacy of a therapeutic vaccination against hepadnaviral infection.…”

“…In this strain WHV particles are not shed into the bloodstream. Male WtgS – mice show stronger WHV replication in the liver than females and elevated ALT levels (http://onlinelibrary.wiley.com/doi/10.1002/hep.29155/suppinfo). Male and female WtgS – mice were immunized with the heterologous DNA prime‐AdV boost regimen as described above (Fig.…”

“…C57BL/6 male and female mice (genotype H‐2 b/b ) at the age of 9 to 10 weeks were purchased from Harlan Winkelmann Laboratories (Borchen, Germany) or inbred. WHV transgenic mice lineages carrying WHV wild‐type (strain 1217, Wtg) and a mutated transgenome lacking the L‐, M‐ and S‐WHsAg (strain 1281, WtgS – ) were created on C57BL/6 background (genotype H‐2 b/b ) and previously characterized . WHV tg mice were 10 to 12 weeks old at the beginning of experiments.…”

“…Hydrodynamic injection (HI) with the HBV genome results in transient HBV replication in the mouse liver and viral clearance within 2‐4 weeks, thereby mimicking acute HBV infection . Woodchuck hepatitis virus (WHV) transgenic (Tg) mice (Wtg) served as a model of persistent hepadnaviral infection and were used to test therapeutic vaccination approaches . Both models showed gender‐related differences in hepadnaviral replication that reflect the situation in humans: viral replication was higher in males than in females .…”

“…Woodchuck hepatitis virus (WHV) transgenic (Tg) mice (Wtg) served as a model of persistent hepadnaviral infection and were used to test therapeutic vaccination approaches . Both models showed gender‐related differences in hepadnaviral replication that reflect the situation in humans: viral replication was higher in males than in females . Therefore, we explored these mouse models to study the gender‐related differences in the virus‐specific immune responses and therapeutic vaccination.…”