|Heers Dack, Kristen|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2004
Publication Date: 8/1/2004
Citation: Elliott, M.B., Pryharski, K.S., Yu, Q., Boutilier, L.A., Campeol, N., Melville, K., Laughlin, T.S., Gupta, C.K., Lerch, R.A., Randolph, V.B., Lapierre, N.A., Heers Dack, K.M., Hancock, G.E. 2004. Characterization of recombinant respiratory syncytial viruses with the attachment (G) protein deleted of the region responsible for type 2 T cell responses and pulmonary eosinophilia. Journal of Virology. 78:8446-8454. Interpretive Summary: Human respiratory syncytial virus (RSV) is a leading viral cause of severe lower respiratory tract disease, including bronchiolitis and pneumonia, in young infants, aged adults and patients with abnormal immunity. It is estimated that lower respiratory tract disease caused by RSV is responsible for 90% of bronchiolitis in infancy and 50% of all cases of pneumonia during the first 2 years of life. Clearly, there is a great need for vaccine development to prevent the disease. Killed RSV, subunit and live-attenuated RSV have been tested as vaccine candidates. Unfortunately, none of them is acceptable as a commercial vaccine. One of the reasons for the failure is that these vaccine candidates cause unbalanced T cells responses against subsequent RSV infection, which contribute to harmful airway inflammation. In this study, by using a reverse genetics technology we generated two recombinant RSV strains with deletions in the middle region of the attachment G protein. We characterized the G internal deletion mutants in mice as well as in human lung epithelial cells to see if the mutants reduce the unbalance T cells responses against the G protein. The results showed that both rRSV strains replicated in the respiratory tract of mice and cell culture, induced neutralization antibody response at a similar level to their parent virus and contributed to a 3.9 log10 reduction in wild-type RSV 4 days after challenge. Importantly, pulmonary eosinophilia, a indication of unbalance T cells responses, was significantly diminished in mice primed with native G protein and challenged with either rRSV G internal deletion mutants. These findings are important for attenuated RSV vaccine development.
Technical Abstract: It is essential that preventative vaccines for respiratory syncytial virus (RSV) elicit balanced T cell responses. Immune responses dominated by type 2 T cells against RSV antigens are believed to cause exaggerated respiratory tract disease and may also contribute to unwanted inflammation in the airways that predispose infants for wheeze through adolescence. Herein we report on the construction and characterization of recombinant RSV (rRSV) strains deleted of amino acids 151-221 (rA2cpDG150-222) or 178-219 (rA2cpDG177-220) of the attachment (G) glycoprotein. The central ectodomain was chosen for modification because a peptide spanning amino acids 149 to 200 of G protein was recently shown to prime several strains of naïve inbred mice for polarized type 2 T cell responses, and peripheral blood T cells from most human donors recognize epitopes within this region. Quantitative PCR demonstrated that synthesis of nascent rRSV genomes in human lung epithelial cell lines was similar to parent virus (cp-RSV). Plaque assays further indicated that rRSV replication was not sensitive to 37 degrees C, but pinpoint morphology was observed at 39oC. Both rRSV strains replicated in the respiratory tract of BALB/c mice and elicited serum neutralization and anti-F protein IgG titers that were equivalent to cp-RSV and contributed to a 3.9 log10 reduction in RSV A2 4 days after challenge. Importantly, pulmonary eosinophilia was significantly diminished in BALB/c mice primed with native G protein and challenged with either rA2cpDG150-222 or rA2cpDG177-220. These findings are important for attenuated RSV vaccine development.