Vaccination with RSV M209-223 peptide promotes a protective immune response associated with reduced pulmonary inflammation.

Respiratory syncytial virus (RSV) is the most common etiologic agent in severe infections of the lower respiratory tract in children with a high mortality rate. However, there are still no licensed vaccines for RSV. In this study, we investigated a putative vaccine based on M209-223 peptide. Mice vaccinated with M209-223 peptide expanded M209-223-specific effector CD4+ T cells upon infection. Vaccination resulted in increased numbers of regulatory T cells (Treg) and Th1 cells, and decreased numbers of Th2 cells. In addition, vaccination with M209-223 peptide, protected mice from infection and prevented lung inflammation, leading to increase in IL-10 and IFN-γ production by lung CD4+ T cells. Treg depletion with anti-CTLA4 antibodies abrogated protection induced by peptide vaccination. Our results support vaccination with M209-223 peptide as an important strategy to generate protection, both systemic and local, by memory RSV-specific CD4+ T cells in mice. Contrarily to inactivated RSV particles, M209-223 peptide vaccination is capable of not only promoting viral clearance, but also reducing inflammatory processes in lungs upon infection.