No abstract

The antiviral T cell failure of patients with chronic hepatitis B virus (HBV) infection was suggested to be caused by a T cell stimulation defect of dendritic cells (DC). To address this hypothesis, monocyte derived DC (MDDC) of patients with chronic or resolved acute HBV infection and healthy controls were studied phenotypically by FACS analyses and functionally by mixed lymphocyte reaction, ELISA, ELISpot and proliferation assays of MDDC cultures or co-cultures with an allogeneic HBc-specific Th cell clone. HBV infection of MDDC was studied by quantitative PCR. MDDC from HBV patients seemed to be infected by the HBV, showed a reduced surface expression of HLA DR and CD40 and exhibited a reduced secretion of IL12p70 in response to HBcAg but not to LPS, as compared to control MDDC. However, after cytokine induced maturation, MDDC from HBV patients revealed an unimpaired phenotype. Moreover, the T cell stimulatory capacity of HBV-DC was intact, since (i) the induction of allospecific proliferative and IFN-c responses was not affected in HBV-MDDC, and (ii) HLA DR7 restricted stimulation of an allogeneic HBc-specific Th cell clone was not impaired by HBV-MDDC compared to control MDDC. It is hypothesized that HBV infection of DC might lead to minor phenotypic and functional alterations without significantly affecting their antiviral Th cell stimulatory capacity.

No abstract

Hepatitis B Virus (HBV) transgenic mice replicating the viral genome at high level but lacking expression of the small envelope protein (HBsAg) have been produced using a terminally redundant viral DNA construct (HBV 1.4). The generation of viable infectious progeny was dependent on sex and age of mice. Viral mRNA was abundant in liver and kidneys and at low levels in other organs of the mice. No viral particles or HBV envelope proteins could be detected in sera of mice. Despite expression of non-secreted LHBs and MHBs proteins in the liver, there was no accumulation of viral particles in the endoplasmic reticulum of hepatocytes and no necroinflammatory hepatitis was observed. Therefore, these mice represent an excellent model for studies of the role of HBsAg in viral assembly, antiviral immune responses, the further understanding of HBV immunopathogenesis, and the development of antiviral vaccines.

Using the murine B16F1 melanoma, we compared a CTL -versus helper T cell ( TH ) -directed vaccination approach. Mice were either orally vaccinated with attenuated Salmonella typhimurium ( SL ) or subcutaneously with dendritic cells ( DCs ) loaded with gp100 peptides predicted to bind to H2 -Kb / H2 -Db molecules. SL were transformed with the murine gp100 cDNA ( SL -gp100 ) or with a fusion construct of gp100 and a fragment of invariant chain cDNA ( SL -gp100 / Ii ). Transcription of these genes in vivo has been readily observed in monocytes and DC. Retardation of B16F1 growth was more efficiently achieved by vaccination with SLgp100 than with DC. Vaccination with SL -gp100 / Ii aiming at preferential presentation by MHC II molecules provided some further improvement due to a stronger expansion of TH and CTL. The importance of help was further sustained by a prolongation of the survival time when mice concomitantly received IL2. Notably, prophylactic, compared to therapeutic, vaccination had no additional impact on survival time / rate. This was due to a striking decrease in frequencies of gp100 -specific TH, CTL, and cytokine -expressing cells during tumor growth. Thus, the efficacy of vaccination was limited by tumor -induced immunosuppression. Our data demonstrate the oral route of vaccination via Salmonella as a most convenient transfer regimen and confirm the superiority of protocols aiming at preferential activation of TH. Cancer Gene Therapy ( 2001 ) 8, 599 -611