T Cell Immunity to Measles Viral Proteins in Infants and Adults after Measles Immunization

Vaccination of infants against measles remains of global importance, and proposed new vaccine strategies include the use of measles proteins or synthetic peptides as immunogens. We studied cell-mediated immunity to whole measles antigen and measles proteins in immune adults and infants after measles vaccine. Further, we measured CD8⁺ T cell responses to peptide pools corresponding to the nucelocapsid (N) measles protein in adults given measles vaccine. Cell-mediated immune responses to three of four measles proteins were equivalent to those against whole measles antigen in immune adults. Responses to the fusion (F) protein were lower in infants compared to whole measles antigen (p ≤ 0.03). Infant responses to both whole measles antigen and the F protein were lower compared with these responses in adults (p ≤ 0.001). CD8⁺ T cell responses to N peptide pools varied, and differed between immune HLA-A2–positive individuals compared with naive and HLA-A2-negative subjects after measles vaccination. The measles-specific T cell adaptive response of infants is limited compared to adults, including responses to the F protein.