Induction of balanced immunity in BALB/c mice by vaccination with a recombinant fusion protein containing a respiratory syncytial virus G protein fragment and a CTL epitope

Respiratory syncytial virus (RSV), an important pathogen of the lower respiratory tract, is responsible for severe illness both in new born and young children and in elderly people. However, development of a RSV vaccine has been hampered by the outcome of the infant trials in the 1960s with a formalin-inactivated RSV (FI-RSV) preparation. Previous studies in mice indicated that G protein immunization resulted in antibody and Th2-type response and failed to induce MHC I-restricted CD8+ T-cell response. Vaccines designed to induce CD8+ T-cell along with antibody response might be ideal. In the present report, a fusion protein G1F/M2 containing a RSV-G protein fragment (G: 125–225 amino acid) and a CD8+ T-cell epitope from RSV-M2 protein was investigated. G1F/M2 was cloned, expressed in E. coli, purified and renaturated. In BALB/c mice, G1F/M2 induced not only humoral immunity but also cellular immunity. In addition, interestedly, G1F/M2 elicited balanced IgG1/IgG2a response. These results suggest that the fusion protein G1F/M2 is potential as a RSV subunit vaccine.