Abstract: The invention provides a method for the synthesis of DNA based on a cyclic mechanism of combining deoxyoligonucleotides comprising combining: (a) a series of unique single-stranded deoxypolynucleotides, each having a 5' sequence which, when in double-stranded form, can be enzymatically treated to form a unique 3' single-stranded protrusion for selective cyclic hybridization with another unique single-stranded deoxypolynucleotide of the series; (b) a unique deoxypolynucleotide having a 3' sequence which can selectively hybridize with one of the unique single-stranded deoxypolynucleotides of (a); (c) a polymerase which can direct the formation of double-stranded deoxypolynucleotides from the single-stranded deoxypolynucleotides; and (d) an enzyme which can form a unique single-stranded 3' protrusion from the double-stranded deoxypolynucleotides; under conditions which hybridize the unique single-stranded deoxypolynucleotides in a cyclic manner to form the DNA.

Abstract: Reagents and methods for the detection of a marker which is associated with severe forms of hepatitis delta virus infection are described. A vaccine comprising immunogenically active HDAg' polypeptides is also described.