Search

Adenovirus types 4 and 7 are currently used as live oral vaccines for prevention of acute respiratory disease caused by these adenovirus serotypes. To investigate the concept of producing live recombinant vaccines using these serotypes, adenovirus types 4 (Ad4) and 7 (Ad7) were constructed that produce HBsAg upon infection of cell cultures. Ad4 recombinants were constructed that express HBsAg from a cassette inserted 135 bp from the right-hand terminus of the viral genome. The cassette contained the Ad4 major late promoter followed by leader 1 of the tripartite leader, the first intervening sequence between leaders 1 and 2, leaders 2 and 3, the HBsAg gene, and tandem polyadenylation signals from the Ad4 E3B and hexon genes. Using this same cassette, a series of Ad4 recombinants expressing HBsAg were constructed with deletions in the intervening sequence between leaders 1 and 2 to evaluate the contribution of the downstream control elements more precisely. Inclusion of regions located between +82 and +148 as well as +148 and +232 resulted in increases in expression levels of HBsAg in A549-infected cells by 22-fold and 44-fold, respectively, over the levels attained by an adenovirus recombinant retaining only sequences from +1 to +82, showing the importance of these elements in the activation of the major late promoter during the course of a natural Ad4 viral infection. Parallel increases were also observed in steady-state levels of cytoplasmic HBsAg-specific mRNA. When similar Ad7 recombinant viruses were constructed, these viruses also expressed 20-fold more HBsAg due to the presence of the intron. All Ad4 and Ad7 recombinants produced HBsAg particles containing gp27 and p24 which were secreted in the medium. When dogs were immunized intratracheally with one of these Ad7 recombinants, they seroconverted to both Ad7 and HBsAg to a high level.

Complementary DNA was synthesized from the double-stranded RNA of the Wa strain of human rotavirus and inserted into the bacterial plasmid pBR322. Clones which contained the gene that codes for the viral glycoprotein (VP7) were identified and the nucleotide sequence was determined. The gene was 1062 base pairs in length with an open reading frame which coded for 326 amino acids. Two potential glycosylation sites were found as well as two hydrophobic regions at the N-terminus of the polypeptide. The untranslated regions at the 5′ and 3′ ends were 48 base pairs and 33 base pairs long, respectively. Only one nucleotide at position 493 differed from the sequence of the Wa VP7 gene described by Richardson et al. (1984, J. Virol. 51, 860–862). A strong prokaryotic promoter sequence was also found between residues 434 and 462. A comparison of the amino acid sequence of the Wa strain (serotype 1) to the Hu/5 strain of human rotavirus (serotype 2) and SA11, the simian rotavirus (serotype 3), revealed a high degree of homology (79.1% and 83.1%, respectively) between the serotypes, suggesting that rotavirus serotypes are stable. The hydrophilic regions of VP7 of the three serotypes were identified and compared for homology. Four of these regions showed variation between serotypes.