Atypical Pulmonary Eosinophilia Is Mediated by a Specific Amino Acid Sequence of the Attachment (G) Protein of Respiratory Syncytial Virus

Abstract

We analyzed the immune responses evoked by a series of overlapping peptides to better understand the molecular basis for respiratory syncytial virus (RSV) G protein–induced eosinophilia in BALB/c mice. In vitro stimulation of spleen cells from natural G protein–primed mice showed dominant proliferative and cytokine (interferon [IFN]-γ and interleukin [IL]-5) responses to a peptide encompassing amino acids 184–198. Mice vaccinated with peptide 184– 198 conjugated to keyhole limpet hemocyanin showed significant pulmonary eosinophilia (39.5%) after challenge with live RSV. In contrast, mice immunized with a peptide (208–222) conjugate associated with induction of IFN-γ secreting spleen cells did not exhibit pulmonary eosinophilia after challenge. The in vivo depletion of CD4+ cells abrogated pulmonary eosinophilia in mice vaccinated with the peptide 184–198 conjugate, whereas the depletion of CD8+ cells had a negligible effect. Therefore, we have identified an association between peptide 184– 198 of natural G protein and the CD4+ T cell–mediated induction of pulmonary eosinophilia after live RSV challenge. Out of 43 human donors, 6 provided peripheral blood mononuclear cells that showed reactivity to G protein from RSV A2, 3 of which responded to peptide 184– 198. The results have important implications for the development of a vaccine against RSV.

Characterization of Recombinant Respiratory Syncytial Viruses with the Region Responsible for Type 2 T-Cell Responses and Pulmonary Eosinophilia Deleted from the Attachment (G) Protein

“…However, the complete absence of G protein severely restricted replication in vivo and thus limited the potential of the rRSV strain as a vaccine. Alternatively, efficacious immunity was observed (47) following immunization of BALB/c mice with vaccinia virusexpressed G protein in which the region shown to be responsible for eosinophilia was altered by a frameshift (50,55). Following challenge with the Long strain of RSV, eosinophilia was not observed.…”

The Attachment (G) Glycoprotein of Respiratory Syncytial Virus Contains a Single Immunodominant Epitope That Elicits Both Th1 and Th2 CD4+ T Cell Responses

“…In addition, analysis of several RSV G protein frameshift mutants has revealed that a particular region spanning aa 193-205 of the G protein is required to induce pulmonary eosinophilia, a process that is dependent on CD4 ϩ T cell recognition of G (22). Furthermore, a separate study established that immunization of BALB/c mice with a peptide derived from aa 184 -198 of the G protein led to the development of pulmonary eosinophilia after intranasal infection with RSV (23). Finally, recent studies from our laboratory have demonstrated that both Th1 and Th2 CD4 ϩ T cells are elicited to a single RSV G-derived peptide encompassing aa 183-197 (24).…”

Respiratory syncytial virus (RSV) fusion protein expressed by recombinant Sendai virus elicits B-cell and T-cell responses in cotton rats and confers protection against RSV subtypes A and B

“…It is now proposed that the formalin inactivated RSV vaccine elicited little neutralizing antibody, explaining the lack of protection. Moreover, in subsequent research studies, animals inoculated with the formalin-inactivated vaccine and challenged with RSV experienced severe lung inflammatory responses characterized by a skewed CD4+ T-cell response (in the absence of neutralizing antibodies) and the influx of eosinophils in the lung [5][6][7][8][9][10][11]. The importance of B-cell responses to protection has been demonstrated by a number of passive protection studies using RSVneutralizing immune globulin and humanized monoclonal antibodies [1;12-14].…”