The entire genome of human hepatitis B virus (HBV) occurring in Latvia was sequenced. This sequence, which is 3182 nucleotides long. was compared with the other previously published HBV genomes and was shown to share maximum homology with HBV subtype ayw DNA. The coordinates of 4 main open reading frames as well as hairpin structures are very well conserved in the two genomes. The distribution of nucleotide substitutions among different HBV genomes suggests that the open reading frames P and X can fultil a coding function. On the basis of primary stucture comparison for hepadnaviral DNAs several evolutionary conclusions can be drawn. Hepatitis B virusDNA sequence

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Insertion of foreign oligopeptide sequences (4G50 amino acids in length) into the Pro144 position of hepatitis B core antigen (HBcAg) leads to the formation of chimeric capsids in Escherichia co/i cells. These capsids are morphologically and immunogically similar to native HBcAg, but expose the inserted oligopeptides on their outer surface and exhibit antigenic and immunogenic characteristics of the latter. As a source of model antigenic determinants, the appropriate DNA copies excised from cloned viral genes such as the pm-S region of hepatitis B virus, the transmembrane protein gp41 of human immunodeficiency virus 1 and the envelope protein gp51 of bovine leukemia virus have been used. The localization of the inserted antigenic determinants on the surface of chimeric capsids does not depend on the presence or absence of the arginine-rich, 39 amino acidlong C terminus of HBcAg.Hepatitis B core antigen; PreS region; Human immunodeficiency virus-l transmembrane protein gp41; Bovine leukemia virus envelope protein gp51; Antigenic determinant

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