Naive antigen-specific T cells respond to viral antigen in vivo and protect the host from MCMV infection during GVHD. BALB/c (non-GVHD) and DBA/2 (GVHD) were transplanted with BALB/c BM (5 × 106) and CD3+ T (2.5 × 106) cells. (A-D) CD8+ T cells were collected from CL4 TCR-transgenic mice, labeled with CFSE and adoptively transferred to BALB/c (non-GVHD) or DBA/2 (GVHD) mice 4 weeks after transplantation. The proliferation of CL4 CD8+ T cells was measured 3 days after (A) administration of 1 µg CL4 peptide IV, or (B) 4 days after infection with 5 × 103 pfu MCMV-HA, a recombinant MCMV expressing the CL4 epitope. (C) The number of transferred CL4 CD8+ T cells was determined in the spleen for each group. (D) Both groups of mice were infected with 5 × 103 pfu MCMV-HA and viral loads in the liver at day 6 PI determined by plaque assay. (E-G) DBA/2 mice were transplanted with BALB/c BM (5 × 106) and CD3+ T (2.5 × 106) cells. One group received 1 × 106 CL4 CD8+ T cells at the time of transplant (CL4 transplant), 1 group received 1 × 106 CL4 CD8+ T cells 4 weeks later (CL4 preinfection), and 1 group did not receive CL4 CD8+ T cells. All 3 groups of mice were infected with 1 × 104 pfu (E) or 5 × 103 pfu (F) MCMV-HA 4 weeks after transplantation. (E) CL4 CD8+ T cells in the spleen were enumerated at 7 days PI. (F) Viral loads in the liver, as measured by plaque assay, and (G) survival were compared in mice that received CL4 cells or were left untreated. (A-C) n = 3 to 4 mice per group; (D) n = 5 to 6 mice per group; (E-G) 3 to 5 mice per group. Data in D-G are representative of at least 2 independent experiments. *P = .01-.05; **P = .001-.01; ***P = .0001-.001.
