Molecular aspects of immune recognition of cytomegalovirus

The studies discussed in this presentation have shown that CD8 T lymphocytes have a primary role in conferring resistance to MCMV in the immunocompetent BALB/c mouse. In the presence of selective CD8 deficiency, however, other mechanisms, apparently mediated by the CD4 T-cell subset, contribute in a compensatory fashion to antiviral immunity. The protective CTL response to MCMV, at least in BALB/c mice, is elicited by a single epitope encoded by the major ie 1 and expressed in protein pp89. The epitope itself contains 18 amino acids, only five of which are the minimum for CTL recognition. Substitutions within a nonapeptide sequence that is part of the pp89 epitope identified two positions that are critical for TCR binding by clone IE1 CTLs. Polyclonal CTLs, in contrast, respond to either the native nonapeptide or any of the substituted variants that were tested, which suggests a certain degree of degeneracy in the specificity of the physiologic immune response.