Conserved cysteine residues within the attachment G glycoprotein of respiratory syncytial virus play a critical role in the enhancement of cytotoxic T-lymphocyte responses

Abstract

The cytotoxic T-lymphocyte (CTL) response plays an important role in the control of respiratory syncytial virus (RSV) replication and the establishment of a Th1-CD4+ T cell response against the virus. Despite lacking Major Histocompatibility Complex I (MHC I)-restricted epitopes, the attachment G glycoprotein of RSV enhances CTL activity toward other RSV antigens, and this effect depends on its conserved central region. Here, we report that RSV-G can also improve CTL activity toward antigens from unrelated pathogens such as influenza, and that a mutant form of RSV-G lacking four conserved cysteine residues at positions 173, 176, 182, and 186 fails to enhance CTL responses. Our results indicate that these conserved residues are essential for the wide-spectrum pro-CTL activity displayed by the protein.

Prophylaxis with a Respiratory Syncytial Virus (RSV) Anti-G Protein Monoclonal Antibody Shifts the Adaptive Immune Response to RSV rA2-line19F Infection from Th2 to Th1 in BALB/c Mice

“…It also is consistent with a recent report by Jorquera et al that described the response in mice to a nanoparticle G peptide vaccine that includes the binding site for MAb 131-2G. In this report, RSV-challenged mice vaccinated with the nanoparticle peptide vaccine compared to an intact G vaccine had a higher percentage of M2 [82][83][84][85][86][87][88][89][90] tetramer-positive T cells in the lung and in the spleen (36). They also noted nanoparticle-vaccinated mice had more IFN-␥ than IL-4-expressing T cells (Th1-type response) in splenocytes stimulated with the M2 [82][83][84][85][86][87][88][89][90] peptide.…”

“…In this report, RSV-challenged mice vaccinated with the nanoparticle peptide vaccine compared to an intact G vaccine had a higher percentage of M2 [82][83][84][85][86][87][88][89][90] tetramer-positive T cells in the lung and in the spleen (36). They also noted nanoparticle-vaccinated mice had more IFN-␥ than IL-4-expressing T cells (Th1-type response) in splenocytes stimulated with the M2 [82][83][84][85][86][87][88][89][90] peptide. In contrast, there were more IL-4-than IFN-␥-expressing T cells (Th2-type response) in mice vaccinated with intact G.…”

“…The G protein specifically has been associated with suppressing a number of immune responses, including induction of Toll-like receptor 3 (TLR3) or 4, IFN-␤ (81), proinflammatory responses of lung epithelial cells (82), lymphoproliferation (83), and activation of dendritic cells (84,85). G has also been noted to downregulate type I IFN production by inducing suppression of cytokine signaling (SOCS) (86) and to enhance cytotoxic T cell responses (87,88).…”

“…The spleen cells (1 ϫ 10 6 cells/well) were incubated for 6 h at 37°C in 96-well culture plates in the presence of RSV peptides for CD4 or CD8 epitopes. The CD4 peptide is aa 183 to 197 of the A2 G protein (44), the CD8 peptide (M2 [82][83][84][85][86][87][88][89][90] ) is aa 82 to 90 of the A2 M2 protein (45), and the ovalbumin control peptide is at aa 323 to 339 (46). The stimulated spleen cells (1 ϫ 10 6 cells/well) were treated with brefeldin A (BD GolgiPlug, San Jose, CA) for the last 4 h, incubated with FcR-blocking antibody (anti-CD16/CD32), and then stained for surface markers (Table 1).…”

“…For the tetramer studies, we stained unstimulated splenocytes with the M2 [82][83][84][85][86][87][88][89][90] tetramer that is specific for the immune dominant MHC class I H-2Kd restricted epitope (SYIGSINNI) of the RSV M2-1 protein (45) (Fig. 5).…”