Antigenic analysis of chimeric and truncated G proteins of respiratory syncytial virus.

Extensive antigenic variation occurs on the attachment glycoprotein G between the two major respiratory syncytial (RS) virus groups. Restriction fragment exchanges were performed among regions of the group A and group B G protein cDNAs to produce chimeric molecules to use in a study of the antigenic structure of the G protein. Proteins were expressed from these chimeric cDNAs using the vaccinia virus T7 bacteriophage polymerase system. Region 1 [A1 or B1, G protein amino acids (aa) 1 to 173] included the cytoplasmic and transmembrane domains and part of the ectodomain, region 2 (A2, aa 174 to 214 in the group A; or B2, aa 174 to 215 in the group B G protein) included the central portion of the ectodomain, and region 3 (A3, aa 215 to 298 in the group A; or B3, aa 216 to 292 in the group B G protein) included the C-terminal region of the ectodomain. The chimeric proteins comprised regions A1B2B3, B1A2A3, A1A2B3, and B1B2A3. Truncated proteins were also produced and consisted of regions A1A2, B1B2, A1, and B1. The expressed proteins were tested by immunofluorescence for reactivity with group-cross-reactive or group-specific G protein monoclonal antibodies (MAbs). Most group-cross-reactive MAbs required the presence of G protein regions 1 or 2 for reactivity. G protein MAbs specific for either group A or group B were dependent on the presence of regions 1, 2, or 3 for reactivity. Thus, each of the three regions of the G protein were found to play a role in reactivity with MAbs, including for each region MAbs with neutralizing activity against RS virus.