Cytotoxic T cell response to Mengo virus in mice: effector cell phenotype and target proteins.

The Mengo virus specific cytotoxic T lymphocyte (CTL) response was investigated after intraperitoneal infection of mice with the attenuated Mengo virus strain vMC24. A high level of CTL activity was detected in spleen cell cultures obtained from infected C3H/HeJ (H-2k) or C57BL/6 (H-2b) mice after a secondary in vitro stimulation with Mengo virus-infected cells. The CTL activity, which was MHC class I-restricted, was shown to be mediated by CD8+ T cells. Recombinant vaccinia viruses that expressed capsid proteins VP0, VP1 or VP3 were produced and used to identify the protein(s) recognized by the Mengo virus-specific CTLs. In both C3H/HeJ and C57BL/6 mice, analysis of CTL activity against target cells expressing each capsid protein showed that VP0 was the only capsid protein recognized by the CD8+ CTLs. The CTL epitope(s) could be further located in the C-terminal half of VP0, i.e. in capsid protein VP2. Moreover, using unlabelled target cells expressing VP0 as cold competitors, we were able to almost completely inhibit recognition and lysis of Mengo virus-infected cells by specific CD8+ CTLs. Thus, the CTL response directed against VP2 was immunodominant in both C3H/HeJ- and C57BL/6-infected mice.