title: Cross-reactivities in memory cytotoxic T lymphocyte recognition of heterologous viruses.
abstract: Analyses of the relationships between different viruses and viral proteins have focused on homologies between linear amino acid sequences, but cross-reactivities at the level of T cell recognition may not be dependent on a conserved linear sequence of several amino acids. The CTL response to Pichinde virus (PV) and vaccinia virus (VV) in C57BL/6 mice previously immunized with lymphocytic choriomeningitis virus (LCMV) included the reactivation of memory cytotoxic T lymphocyte (CTL) specific to LCMV. Limiting dilution assays (LDA) demonstrated that at least part of this reactivation of memory cells in LCMV-immune mice related to cross-reactivity at the clonal level, even though acute infections with these viruses in nonimmune mice elicited CTL responses that did not cross-react in conventional bulk CTL assays. Precursor CTL (pCTL) to LCMV were generated in splenic leukocytes from LCMV-immune mice acutely infected with PV or VV when stimulated in vitro with only the second virus but not with uninfected peritoneal exudate cells (PECs). Cytotoxicity mediated by LCMV-specific CTL clones activated by PV infection was greatly inhibited by anti-CD8 antibody, suggesting that these memory CTL clones recognizing LCMV-infected targets were of low affinity. LCMV-immune splenocytes stimulated in vitro with PV or VV demonstrated a low but significant precursor frequency (p/f) to the heterologous viruses, and splenocytes from PV- or VV-immune mice when stimulated in vitro against LCMV generated a low but significant p/f to LCMV. Short-term CTL clones cross-reactive between LCMV and PV were derived from splenic leukocytes from LCMV-immune mice acutely infected with PV. To distinguish whether the cross-reactivity was directed against a viral peptide or a virus-induced endogenous cellular neoantigen, we demonstrated that a pCTL frequency to PV about 1/4-1/7 that of the frequency to LCMV could be generated from LCMV-immune splenic leukocytes stimulated with the immunodominant LCMV NP peptide. A partially homologous PV peptide generated from the equivalent site to the LCMV NP peptide did not sensitize targets to lysis by either LCMV- or PV-specific CTLs, suggesting that the cross-reactivity in killing was not due to evolutionarily conserved equivalent sequences. Experiments also indicated that prior immunity to one virus could modulate future primary immune responses to a second virus. Elevated pCTL frequencies to PV were seen after acute PV infection of LCMV-immune mice, and elevated pCTL frequencies to LCMV were seen after acute LCMV infection of PV- and VV-immune mice.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Pathology, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: L K
authors.initials: LK
authors.lastname: Selin
authors.forename: S R
authors.initials: SR
authors.lastname: Nahill
authors.forename: R M
authors.initials: RM
authors.lastname: Welsh
mesh_terms: D000818:Animals; D001483:Base Sequence; D016827:CD8 Antigens / Q000276:immunology; D002461:Cell Line, Transformed; D003429:Cross Reactions; D003602:Cytotoxicity, Immunologic; D007156:Immunologic Memory; D007694:Killer Cells, Natural / Q000276:immunology; D008212:Lymphocyte Depletion; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology; D018052:Pichinde virus / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D013997:Time Factors; D014616:Vaccinia virus / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D016827:CD8 Antigens; D009842:Oligopeptides; D014765:Viral Vaccines