RNA phage Q beta coat protein as a carrier for foreign epitopes.

The Q beta gene C has been proposed as a new carrier for the exposure of foreign peptide sequences. Contrary to well-known 'display vectors' on the basis of coat proteins of RNA phage group I, group III phage Q beta-based vectors suggested application of the 195-amino acid extension of coat protein (CP) within the so-called A1 protein for insertion of the appropriate immunological epitopes. 'Mosaic' capsids presenting model hepatitis B virus preS1 and HIV-1 gp120 epitopes and formed by Q beta CP together with A1-derived proteins were obtained as a result of (1) suppression of leaky UGA stop codon of the CP gene and (2) simultaneous expression of 'pure' CP and full-length A1-derived genes obtained after the changing of CP-terminating UGA to strong UAA stop codon or sense GGA codon, respectively.

Determination of the minimal length of preS1 epitope recognized by a monoclonal antibody which inhibits attachment of hepatitis B virus to hepatocytes.

The minimal amino acid sequence sufficient to be recognized efficiently by virus-attachment inhibiting murine monoclonal anti-preS1 antibody MA18/7 has been determined. We have constructed a recombinant gene library using the cloned coat protein gene of Escherichia coli RNA bacteriophage fr as a carrier. Different fragments of preS1 region from cloned hepatitis B virus (HBV) genomes, subtype ayw and adw, were inserted at position 2 of the 129 amino acid-long fr coat protein gene in the appropriate E. coli expression vectors. Fine mapping of preS1 epitope recognized by MA18/7 was accomplished by bidirectional shortening of the preS1 within original recombinant preS-fr coat protein genes with Bal31 exonuclease. Immunoblot analysis of the obtained recombinant protein library revealed that the tetrapeptide Asp-Pro-Ala-Phe (DPAF), located at the position preS(31-34) and conserved in all known HBV genomes, is sufficient to bind MA18/7 antibody. Recognition of the preS1 region by MA18/7 occurred irrespective of the amino acid context surrounding this DPAF tetrapeptide. Further shortening of this minimal epitope from the left or from the right side completely prevented antibody binding in immunoblots.

Subtype ayw variant of hepatitis B virus. DNA primary structure analysis.

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 suggest that the open reading frames P and X can fulfil a coding function. On the basis of primary structure comparison for hepadnaviral DNAs several evolutionary conclusions can be drawn.

The structure of cloned 3'-terminal RNA region of bovine leukemia virus (BLV).

cDNA synthesized on the bovine leukemia virus RNA template has been cloned in the pBR322 Pst I site. Colony hybridization with BLV RNA fragments and oligo (dT) has revealed a clone with cDNA insert containing 660 3'-terminal nucleotides of the BLV genome. The nucleotide sequence of the insert corresponding to U3 and R regions of the long terminal repeats (LTR) of viral genome has been determined. BLV U3, like U3 of other retroviruses, presumably contains promoter. The unusually long R region (about 230 bp), a certain homology with ATLV U3-R and some other structural features allow to group BLV LTR together with ATLV LTR in a separate class of retroviral LTR.