Immunoreactive domains and integrin-binding motifs in adenovirus Penton base capsomer

A panel of nine independent mouse monoclonal antibodies (MAbs) against pent on base capsomers of subgenus C adenovirus serotypes 2 (Ad2) and 5 (Ad5) we re isolated and characterized. Two of them (1D2 and 5A5), raised against Ad 5 virion as the immunogen, bound to sodium dodecyl sulfate (SDS)-resistant and subgenus C-specific epitopes that were not present in subgenus B Ad3 pe nton base. The 1D2 and 5A5 epitopes were mapped to two distinct regions tha t did not belong to the main variable region carrying the integrin-binding RGD motif at position 340. For the other seven MAbs, raised against recombi nant Ad2 penton base protein (9S-pentamers), the epitopes were sensitive to SDS-denaturation, but reacted with native Ad2, Ad5, and Ad3 penton base. T he epitopes recognized by the nine MAbs and by polyclonal antipenton base a ntibodies defined three major immunoreactive regions. One (I) mapped to the N-terminal domain (residues 116-165); the other two regions were almost sy mmetrically disposed on both sides of the integrin-binding RGD motif at pos ition 340, within residues 248-270 (II), and within residues 368-427 (III) in the C-terminal domain. Region II overlapped the fiber-binding site in pe nton base (residues 254-260). None of the MAbs showed any detectable virus neutralization effect, but they all slightly augmented the efficiency of Ad -mediated gene transfer. Although none of their epitopes included the RGD-3 40 tripeptide, substitutions of the arginine residue in the RGD motif aboli shed the reactivity of six individual and distant epitopes, suggesting a ma jor conformational role for the RGD-containing domain.