Determination of antigen-specific CTL induced by the gene vaccine in vitro with MHC pentamer / 中华检验医学杂志

ABSTRACT

Objective To determine the antigen-specific CTL in PBMC induced by a fusional family-gene vaccine of the immunoglobulin heavy chain variable gene framework region combined with the sequence of cytokine CM-CSF in vitro with MHC pentamer. Methods Peripheral blood samples were collected from two healthy donors and two patients. One was follicular lymphoma and another was hair cell leukemia. PBMC were isolated by density gradient centrifugalization with Ficoll and then subsequently differentiated into immature DCs (imDCs) induced by recombinant human GM-CSF and recombinant human IL-4. Gene gun was used to deliver the plasmids of the gene vaccine or the control plasmids into the imDCs. RT-PCR and ELISA assay were used to detect IgHVl-GM-CSF mRNA and GM-CSF in order to validate the transfection of the vaccine. After adding the cytokine cocktail, the imDCs became mature DCs. Then the mature DCs were co-cultured with lymphocytes from the blood samples for the induction of the antigen-specific CTL. The cultured cells were classified into vaccine group and control group and harvested at different time points of 0 d,7d, 17 d and 24 d after transfection. The subset of CD3+CD8+ T cells was analyzed by FCM assay. Finally, the CTL levels were detected with fluorescently labeled MHC pentamer antibody targeting vaccine epitopes. Results With the induction of cytokines, the imDCs with typical morphology were generated in PBMC. After delivering, the efficient expressions of the vaccine in the imDCs were determined by RT-PCR. And ELISA results also confirmed that GM-CSF was produced at a level of (28 ±6) ng/106 cells of the imDCs loaded with the vaccine, which was significantly different from that of control group (10 ± 3) ng/106 cells (t = 5. 191, P <0.01). FCM assay result showed that the CD3+ CD8+ T cells increased in a stepwise pattern during the culture. For control group, the levels at 0 d,7d, 17d and 24 d were ( 34. 24 ± 2. 72 )% , (46.06 ± 3.08)%, ( 65. 34 ± 4. 26 )% and (73.86 ±4.85 )% , respectively. For vaccine group, the results were (32. 28 ± 2. 08 ) % , (45. 32 ± 3. 81)% , ( 63. 37 ± 4. 21)% and (75. 01 ±3. 20)%. The differences between each time point had statistical significance (F = 176. 966 ,P <0.01) ,but there was no statistical differences between vaccine group and control group ( F = 0.657,P>0.05). The MHC pentamer analysis showed that the DCs loaded with IgHV1-GM-CSF fusional vaccine could efficiently induce the antigen-specific CTL response and the CTL levels increased gradually with the culture time, with the highest level of 4. 36% in the lymphoma blood and 3. 89% in the hair cell leukemia blood. Conclusions MHC pentamer assay could efficiently determine the antigen-specific CTLs response induced by the gene vaccine of family IgHV frame region in vitro. It could be a useful method for monitoring of anti-tumor cell immunity and evaluating of diagnosis and prognosis of the tumors in clinical application.