| BackgroundAfter primary infection in the immunocompetent population, human cytomegalovirus (HCMV) can persist latently in myeloid cells, smooth muscle cells, endothelial cells and other cells. Latent HCMV tends to be susceptible to reactivation and may cause lethal pneumonia and hepatitis in the immunosuppressed individuals. Especially in patients undergoing allogeneic haematopoietic stem cell transplantation (allo-HSCT), HCMV reactivation is a frequent complication. Virus-specific cellular responses, in particular CD8+T cells, play a critical role in the control of the virus replication and in the prevention of HCMV-related diseases. Therefore, the evaluation of the frequency and function of HCMV-specific CD8+T cells after allo-HSCT may be an important part for preventing HCMV reactivation and thus contributes to investigate the mechanism of HCMV-specific T-cell immune responses. Methods and Objectives21HLA-A*0201recipients following allo-HSCT in our hospital were enrolled from September2009to October2012. A total of484ethylenediaminetetraacetic acid (EDTA)-anticoagulant peripheral blood samples were taken at1-week intervals after engraftment when patients were hospitalised. Samples from follow-up outpatients were obtained monthly or tri-monthly. HCMV pp65antigenaemia was evaluated using an indirect enzyme immunohistochemical method. Pre-transplant HCMV serostatus was tested by detecting HCMV-specific immunoglobulin G/M (IgG/IgM) antibody using an enzyme-linked immunosorbent assay (ELISA). HLA-peptide pentamer staining assay was used to determine the frequency of pp65495-503-specific CD8+T cells. IFN-γ-enzyme-linked immunospot (IFN-γ-ELISPOT) assay was used to analyze the function of pp65495-503-specific CD8+T cells. The quantitative and functional evaluation of HCMV-specific CD8+T cells in controlling HCMV reactivation was performed in order to elucidate the mechanism of HCMV-specific T-cell immune responses in recipients after allo-HSCT.Results1. The absolute number of pp65495-503-specific CD8+T cells did not differ significantly (p>0.05) between positive antigenaemia and negative antigenaemia with a mean of54.5/μl and40.5/μl, respectively, in21HLA-A*0201patients after allo-HSCT.2. The level of pp65495-503-specific CD8+T cells>20/μl of peripheral blood was maintained90days after transplantation.3. There was a significant difference in the spot count of IFN-γ-secreting T cells between positive antigenaemia (mean,507/2.5×105PBMCs) and negative antigenaemia (mean,216/2.5×105PBMCs; p<0.05). Conclusions1. pp65495-503-specific CD8+T cells may not be sufficient to prevent the occurrence of HCMV antigenaemia in recipients after allo-HSCT.2. The combination of pentamer and ELISPOT assays may be valuable for evaluating HCMV-specific CD8+T cells. |
