IMMUNODOMINANCE OF A SINGLE CTL EPITOPE IN A PRIMATE SPECIES WITH LIMITED MHC CLASS-I POLYMORPHISM

MHC class I molecules play a crucial role in immunity to viral infecti ons by presenting viral peptides to cytotoxic T lymphocytes. One of th e hallmarks of MHC class I genes in outbred populations is their extra ordinary polymorphism, yet the significance of this diversity is poorl y understood, Certain species with reduced MHC class I diversity, such as the cotton-top tamarin (Saguinus oedipus), are more susceptible to fatal viral infections. To explore the relationship between this prim ate's limited MHC class ! diversity and its susceptibility to viruses, we infected five cotton-top tamarins with influenza virus, Every tama rin recognized the same immunodominant CTL epitope of the influenza nu cleoprotein. Surprisingly, this nucleoprotein peptide was bound by Sao e-G08, an MHC class I molecule expressed by every cotton-top tamarin, Two tamarins also made a subdominant response to an epitope of the ma trix (M1) protein, This peptide appeared to be bound by another common MHC class 1 molecule, With the exception of an additional subdominant response to the polymerase (PB2) protein in one individual, no other influenza-specific CTL responses were detected, In populations or spec ies with limited MHC class I polymorphism like the cotton-top tamarin, a dependence on shared MHC class I molecules may enhance susceptibili ty to viral infection, since viruses that evade MHC class I-restricted . recognition in one individual will likely evade recognition in the m ajority of individuals.