Mixed vs full donor engraftment early after hematopoietic cell transplant: Impact on incidence and control of cytomegalovirus infection

Modulation of cytomegalovirus immune evasion identifies direct antigen presentation as the predominant mode of CD8 T-cell priming during immune reconstitution after hematopoietic cell transplantation

Cytomegalovirus (CMV) infection is the most critical infectious complication in recipients of hematopoietic cell transplantation (HCT) in the period between a therapeutic hematoablative treatment and the hematopoietic reconstitution of the immune system. Clinical investigation as well as the mouse model of experimental HCT have consistently shown that timely reconstitution of antiviral CD8 T cells is critical for preventing CMV disease in HCT recipients. Reconstitution of cells of the T-cell lineage generates naïve CD8 T cells with random specificities among which CMV-specific cells need to be primed by presentation of viral antigen for antigen-specific clonal expansion and generation of protective antiviral effector CD8 T cells. For CD8 T-cell priming two pathways are discussed: "direct antigen presentation" by infected professional antigen-presenting cells (pAPCs) and "antigen cross-presentation" by uninfected pAPCs that take up antigenic material derived from infected tissue cells. Current view in CMV immunology favors the cross-priming hypothesis with the argument that viral immune evasion proteins, known to interfere with the MHC class-I pathway of direct antigen presentation by infected cells, would inhibit the CD8 T-cell response. While the mode of antigen presentation in the mouse model of CMV infection has been studied in the immunocompetent host under genetic or experimental conditions excluding either pathway of antigen presentation, we are not aware of any study addressing the medically relevant question of how newly generated naïve CD8 T cells become primed in the phase of lympho-hematopoietic reconstitution after HCT. Here we used the well-established mouse model of experimental HCT and infection with murine CMV (mCMV) and pursued the recently described approach of up- or down-modulating direct antigen presentation by using recombinant viruses lacking or overexpressing the central immune evasion protein m152 of mCMV, respectively. Our data reveal that the magnitude of the CD8 T-cell response directly reflects the level of direct antigen presentation.

[Impact of poor graft function on cytomegalovirus pneumonia in patients who have undergone haploidentical stem cell transplantation]

Objective: To retrospectively analyze the impact of primary PGF on CMV pneumonia in patients who have undergone haplo-HSCT. Methods: The clinical data of 122 patients who underwent haplo-HSCT at the Peking University Institute of Hematology from 2011-2012 were retrospectively reviewed. The incidence rate of CMV pneumonia between PGF and good graft function (GGF) was compared, and the factors were analyzed. In addition, outcomes in PGF patients with CMV pneumonia have been described. Results: Total 122 patients were retrospectively reviewed, and of these, 26 (21.3% ) had PGF, while 96 (78.7% ) had GGF. In addition, 15 patients had CMV pneumonia, and the median time to the development of CMV pneumonia was 103 (31-262) days; the 1-year cumulative incidence of CMV pneumonia was 12.3% (95% CI 6.2% -18.4% ) . In patients with primary PGF and GGF after Haplo-HSCT, the incidence of CMV pneumonia was 30.8% (8/26) and 7.3% (7/96) , respectively (P=0.002) . Moreover, 24 patients had CMV viremia (92.3% ) , while of the 96 GGF patients, 79 (82.3% ) had CMV viremia (P=0.212) . In multivariate analysis, the results showed that primary PGF had a significant influence on CMV pneumonia (P=0.005) . Compared with those without CMV pneumonia, patients with CMV pneumonia had poorer overall survival 37.3% (95% CI 11.2% -63.4% ) vs. 78.9% (95% CI 72.0% -87.6% ) (χ(2)=16.361, P<0.001) . The 1-year overall survival (OS) was 25.0% (95% CI 0% -55.0% ) and 50.0% (95% CI 26.9% -73.1% ) (χ(2)=4.656, P=0.031) in PGF patients with (8/26) and without (18/26) CMV pneumonia. Conclusion: The incidence of cytomegalovirus pneumonia in patients with primary poor graft function increases and the survival rate decreases.

Incidence of viral and fungal complications after utilization of alternative donor sources in hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) remains the only curable option for adult patients with hematologic malignancies. According to guidelines published by the American Society for Transplantation and Cellular Therapy, allogeneic HCT should be offered to all intermediate- and high-risk patients with acute leukemia. While matched-related donor (MRD) grafts continue to be the preferred stem cell source for allogeneic HCT, studies comparing MRD grafts to matched-unrelated donor (MUD) grafts showed comparable outcomes in patients with acute leukemia. Unfortunately, for those without a suitable matched-related graft, the probability of finding a suitable matched-unrelated donor varies significantly depending on racial and ethnic background. With allogeneic HCT procedures increasing year after year due to the increased availability of suitable donors, each of these alternative donor sources merits special clinical considerations, specifically with regard to infections. Infections remain a significant cause of morbidity and mortality after allogeneic transplant, especially in those receiving alternative donor grafts. Due to the high-risk nature associated with these donor grafts, it is important to understand the true risk of developing infectious complications. While there are a multitude of infections that have been described in patients post-allogeneic HCT, this review seeks to focus on the incidence of cytomegalovirus (CMV) and invasive fungal infections (IFI) in adult patients receiving alternative donor source transplantation for hematologic malignancies.