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As a major cause of acute and chronic liver disease as well as hepatocellular carcinoma, hepatitis B virus (HBV) continues to pose significant health problems world-wide. Recombinant hepatitis B vaccines based on adenovirus vectors have been developed to address global needs for effective control of hepatitis B infection. Although considerable progress has been made in the construction of recombinant adenoviruses that express large amounts of HBV gene products, preclinical immunogenicity and efficacy testing of candidate vaccines has remained difficult due to the lack of a suitable animal model. We demonstrate here that chimpanzees are susceptible to enteric infection by human adenoviruses type 7 (Ad7) and type 4 (Ad4) following oral administration of live virus. Moreover, after sequential oral immunization with Ad7- and Ad4-vectored vaccines containing the hepatitis B surface antigen (HBsAg) gene, significant antibody responses to HBsAg (anti-HBs) were induced in two chimpanzees. After challenge with heterologous HBV, one chimpanzee was protected from acute hepatitis and the other chimpanzee experienced modified HBV-induced disease. These data demonstrate the feasibility of using orally administered recombinant adenoviruses as a general approach to vaccination.

Negative and positive selection procedures were used to establish whether the strong proliferative response of T cells to M1sa determinants is H-2 restricted. After negative selection of H-2 determinants in vivo, it was shown that T cells give high primary mixed lymphocyte reactions in vitro to M1sa determinants presented on H-2-incompatible stimulator cells. Other studies demonstrated that (a) negative selection of T cells to M1sa determinants on H-2-incompatible cells removed T cells with specificity for M1sa-bearing H-2-compatible cells, and (b) T cells primed in vitro or in vivo to M1sa determinants on H-2-compatible cells gave high secondary responses to M1sa determinants presented either on H-2-compatible or H-2-incompatible stimulator cells. From these data we conclude that T cells recognize M1sa determinants per se rather than an association of M1sa plus self or allo-H-2 determinants.

Liver, pancreas, and kidney from Pekin ducks infected with duck hepatitis B virus (DHBV) were assayed for the presence of both viral antigen and replication-specific forms of viral nucleic acid. In young congenitally infected ducks, antigen was detectable in hepatocytes and bile duct epithelia, in kidney glomeruli and tubular epithelia, and in cells localized to pancreatic acini. In older experimentally infected ducks, antigen was detectable in hepatocytes, in glomeruli and tubular epithelia, and in cells localized to presumptive pancreatic alpha-islets. All but the glomeruli-associated viral antigen appeared to be localized to the cytoplasm of antigen-positive cells. Much of the glomeruli-associated antigen appeared to be extracellular and was detected in glomeruli that were positive for the accumulation of immunoglobulin, observations suggestive of the deposition of viral antigen-antibody complexes. As analyzed with bulk tissue, replication-specific forms of viral nucleic acid were detectable in liver and pancreas from the young congenitally infected ducks and in liver and kidney from the older experimentally infected ducks.

The hepatitis B-like viruses have a approximately 3.2 kilobase, partially double-stranded DNA genome that is held in a circular conformation by a cohesive overlap between the 5' ends of the two strands. In addition, a protein is covalently bound to the 5' end of the minus strand of virion DNA. The sequence of the cohesive overlap region and its location relative to open reading frames and to the initiation site for minus-strand DNA synthesis, which occurs by reverse transcription of viral RNA, were investigated in duck hepatitis B virus. The 5' ends of virion DNA were mapped by restriction endonuclease analysis of labeled virion DNA, S1 nuclease digestion, and primer extension, using avian myeloblastosis virus DNA polymerase. The cohesive overlap region was shown to be 69 +/- 4 base pairs in length. It contained a 10-base pair inverted repeat in approximately the middle and a 12-base pair direct repeat near each end. The apparent initiation site of reverse transcription was determined by partial sequence analysis of dideoxynucleotide-truncated minus-strand DNA intermediates and comparison of their lengths with the length of a known DNA sequence. It mapped within two to four nucleotides of the 5' end of the minus strand of virion DNA. The results are consistent with the interpretation that the 5' end of the minus strand of virion DNA is the origin of reverse transcription and that the protein covalently bound to virion DNA is the primer of reverse transcription.

Using recombinant adenoviral vectors, we expressed and characterized the large, middle, and major envelope proteins of hepatitis B virus (HBV). Cells infected with the recombinant adenovirus which contained the large envelope gene (HS1.HP) expressed predominantly large envelope and small but detectable quantities of middle (4%) and major (6%) envelope proteins in the cell lysate. No HBV envelope proteins were detected in the culture medium from HS1.HP-infected cells. Cells infected with recombinant adenovirus which contained the middle envelope gene (HS2.HP) expressed and secreted the middle and major envelope proteins in a molar ratio of 3:1. Cells infected with the recombinant adenovirus which contained the major envelope gene (HS.HP) expressed and secreted major envelope proteins. The HBV envelope proteins secreted by cells infected with either HS2.HP or HS.HP were assembled in 22-nm particles, as shown by velocity sedimentation rate determination, buoyant densities, and electron microscopy. Cells coinfected with a recombinant adenovirus which contained the large envelope gene and with either HS2.HP or HS.HP expressed similar quantities of the large, middle, and major envelope proteins in the cell lysates. Secretion of the major and middle envelope proteins was inhibited more than 95% by the presence of the large envelope proteins. These results suggest that differential biosynthesis, transport, and processing of the envelope proteins occur during HBV infection, allowing efficient assembly and secretion of virions and hepatitis B surface antigen particles.

Analysis of duck hepatitis B viral DNA by gel electrophoresis, Southern blotting, and binding to benzoylated naphthoylated DEAE-cellulose showed that a protein is bound to the minus-strand virion DNA as well as to the full-length single strand, minus-strand species, and minus-strand DNA intermediates isolated from replicating complexes present in infected duck liver. By utilizing a modified dideoxynucleotidyl sequencing method, it was shown that the protein is covalently bound to the smallest detectable growing strands (ca. 30 bases) and that minus-strand synthesis begins at a unique site. These results support the notion that the protein may function as a primer for synthesis of the minus-strand DNA.

A high proportion of T cell clones derived from bulk cultures selected to M1s a,d determinants were found to have joint specificity for allo-H-2 determinants, and vice versa. Significantly, the patterns of H-2 alloreactivity shown by clones selected to M1sa,b determinants appeared to be random. The possible implications of these findings are discussed.

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The effect of selective PDE-I (vinpocetine), PDE-III (milrinone, CI-930), PDE-IV (rolipram, nitroquazone), and PDE-V (zaprinast) isozyme inhibitors on TNF-α and IL-1β production from LPS stimulated human monocytes was investigated. The PDE-IV inhibitors caused a concentration dependent inhibition of TNF-α production, but only partially inhibited IL-1β at high concentrations. High concentrations of the PDE-III inhibitors weakly inhibited TNF-α, but had no effect on IL-1β production. PDE-V inhibition was associated with an augmentation of cytokine secretion. Studies with combinations of PDE isozyme inhibitors indicated that PDE-III and PDE-V inhibitors modulate rolipram's suppression of TNF production in an additive manner. These data confirm that TNF-α and IL-1β production from LPS stimulated human monocytes are differentially regulated, and suggest that PDE-IV inhibitors have the potential to suppress TNF levels in man.