Characterization of a strain-specific monoclonal antibody to hepatitis delta virus antigen

Sequences of the hepatitis delta virus (HDV) vary to different degrees amon g isolates. A monoclonal antibody, designated as HP6A1, against the antigen of HDV (HDAg) has been characterized for its specificity. HP6A1 bound to H DAg of isolate 25 (genotype I) that was used for immunization, but not to o thers of both genotypes I and II. The epitope recognized by HP6A1 was then determined by a phage library displaying various heptapeptides. A consensus peptide deduced has the best match with that of residues 4-10 of HDAg (iso late 25). To confirm the phage mapping result, Escherichia coil recombinant proteins containing different lengths and various segments of HPAg (isolat e 25) were constructed. The shortest HDAg segment contained in the fusion p rotein that reacted with HP6A1 was residues 1-10. When this peptide was add ed to the N-terminus of a heterologous protein engineered for eucaryotic ex pression, the fusion protein was detected by HP6A1. It is concluded that HP 6A1 recognizes an epitope located at the N-terminus of HDAg (isolate 25). S ince viruses of quasi-species exist in natural infections, a question of ho w different viral strains interact in vivo remains to be explored. The high ly specific MAb opens a possibility to examine the fate of one strain in th e presence of other related species in a cell transfection system. (C) 2000 Elsevier Science B.V. All rights reserved.