Immune responses to the nonglycosylated ectodomain of respiratory syncytial virus attachment glycoprotein mediate pulmonary eosinophilia in inbred strains of mice with different MHC haplotypes

Development of subunit vaccines against respiratory syncytial virus (RSV) for naive human infants is hindered by concerns that immunization with the fusion or attachment (G) proteins will elicit polarized Type 2 T cell responses and cause immunopotentiation upon subsequent natural infection. We investigated the regions of G protein responsible for inducing a Type 2 T cell phenotype in inbred mice of different MHC haplotype toward development of vaccines with improved safety. As demonstrated by IL-5-dependent pulmonary eosinophilia after challenge and serum anti-G protein IgG1 to IgG2 ratios, highly purified native G protein sensitized all strains for a Type 2 T cell phenotype. Stimulation of G protein-primed splenocytes with synthetic overlapping peptides indicated that the nonglycosylated ectodomain was primarily responsible. Respectively the recall responses of BALB/c (H2(d)), C57BL/6 (H-2(b)), SJL (H-2(s)), and C3H/HeJ (H-2(k)) mice were directed against epitopes within peptides spanning amino acids 184-198 (pep(184-198)), 168-181 (pep(168-181)) or 171-185 (pep(171-185)), 176-190 (pep(176-190)), and 104-118 (pep(104-118)) or 159-173 (pep(159-173)). Injection of pep(184-198) conjugated to KLH (pep(184-198)-KLH) primed H2(d) [BALB/c, B6.C-H2(d)/bBy], but not H-2(b) [C57Bl/6, C.B10-H2(b)/LiMcd] mice for pulmonary eosinophilia. Sensitization with a peptide-KLH conjugate encompassing amino acids 149-200 (pep(149-200)-KLH) further confirmed that Type 2 T cell responses in BALB/c, C57BL/6 and SJL, but not C3H/HeJ mice were induced by the nonglycosylated ectodomain of G protein. These data are important for design of safe and efficacious subunit and attenuated vaccines for RSV.