The respiratory syncytial virus subgroup B attachment glycoprotein: analysis of sequence, expression from a recombinant vector, and evaluation as an immunogen against homologous and heterologous subgroup virus challenge.

The attachment glycoprotein G of respiratory syncytial (RS) virus is important in both the antigenic and molecular diversity of the RS viruses. Previous work has shown that the glycoprotein G of a subgroup A RS virus expressed from a recombinant vaccinia virus provides significant protection against homologous but not heterologous subgroup virus challenge. We undertook the cDNA cloning and nucleotide sequencing of the G mRNA of a subgroup B RS virus (8/60) to extend molecular comparisons of the G protein both within and between subgroups. We also tested the ability of a subgroup B G protein to provide protection against challenge by A or B subgroup viruses. Sequence analysis showed a deduced amino acid sequence having a single major open reading frame encoding a protein of 292 amino acids with an elevated serine and threonine (30%) and proline (9%) content. The 8/60 G differed from a subgroup A virus (A2) G protein with only a 56% amino acid identity while the 8/60 G shared a 98% amino acid identity with the G protein of another subgroup B virus (18537). The 8/60 G cDNA was placed in a vaccinia virus vector (vvGB) which was shown to express the 8/60 G protein. Cotton rats immunized intradermally with vvGB and later challenged intranasally with 8/60 RS virus had a significant reduction in viral titers in the lungs relative to control animals whereas similarly immunized animals were not protected against heterologous subgroup challenge. Our results indicate that a RS virus subunit vaccine containing the G protein would require both A and B subgroup G proteins to afford protection against viruses of both subgroups.