Rapid monitoring of immune reconstitution after allogeneic stem cell transplantation - a comparison of different assays for the detection of cytomegalovirus-specific T cells

Expansion of effector memory Vδ2neg γδ T cells associates with cytomegalovirus reactivation in allogeneic stem cell transplant recipients

Background

Cytomegalovirus (CMV) reactivation is a significant concern following allogeneic stem cell transplantation. While previous research has highlighted the anti-CMV reactivation effect of γδ T cells in immunocompromised transplant patients, their characterization in recipients at high risk of CMV reactivation remains limited.

Methods

This study focused on D+/R+ recipients (where both donor and recipient are CMV seropositive) at high risk of CMV reactivation. We analyzed 28 patients who experienced CMV recurrence within 100 days post-allogeneic hematopoietic stem cell transplantation, along with 36 matched recipients who did not experience CMV recurrence. Clinical data from both groups were compared, and risk factors for CMV reactivation were identified. Additionally, CMV viral load was measured, and flow cytometric analysis was conducted to assess changes in peripheral blood γδ T cell proportions, subpopulation distribution, and differentiation status. We also analyzed the CDR3 repertoire of the TCR δ chain in different γδ T cell subsets. Functional analysis was performed by measuring the lysis of CMV-infected cells upon stimulation.

Results

CMV reactivation post-transplantation was associated with acute graft-versus-host disease (aGvHD) and reactivation of non-CMV herpesviruses. Notably, CMV reactivation led to sustained expansion of γδ T cells, primarily within the Vδ2neg γδ T cell subpopulation, with a trend toward differentiation from Naive to effector memory cells. Analysis of the δ chain CDR3 repertoire revealed a delay in the reconstitution of clonal diversity in Vδ2neg γδ T cells following CMV reactivation, while Vδ2pos T cells remained unaffected. Upon stimulation with CMV-infected MRC5 cells, the Vδ2neg γδ T cell subpopulation emerged as the primary effector cell group producing IFN-γ and capable of lysing CMV-infected cells. Moreover, our findings suggest that NKG2D is not necessary involved in Vδ2neg γδ T cell-mediated anti-CMV cytotoxicity.

Conclusion

This study provides novel insights into the role of γδ T cells in the immune response to CMV reactivation in transplantation recipients at high risk of CMV infection. Specifically, the Vδ2neg γδ T cell subpopulation appears to be closely associated with CMV reactivation, underscoring their potential role in controlling infection and reflecting CMV reactivation in HSCT patients.

Cytomegalovirus Cell-mediated Immunity Assays in Pediatric Transplantation

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in pediatric transplantation. However, currently utilized CMV prevention paradigms have limitations, leading to research aimed at novel strategies for mitigation of CMV infection. Cell-mediated immunity (CMI) is crucial in controlling CMV infection and the use of CMV-specific CMI assays to guide prevention and treatment of CMV infection in both solid organ transplant and hematopoietic cell transplant recipients shows great promise. In this article, we review the immune response to CMV infection to highlight the rationale for CMI assays, describe available commercial assays and strategies for their use, and summarize relevant literature regarding the use of CMI assays in transplant recipients.

Donor CMV-specific cytotoxic T lymphocytes successfully treated drug-resistant cytomegalovirus encephalitis after allogeneic hematopoietic stem cell transplantation

Background: Cytomegalovirus (CMV) infection of the central nervous system (CNS) is a rare but life-threatening complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT).Cases presentation: Two patients with drug-resistant CMV encephalitis after allo-HSCT were successfully treated with donor CMV-specific cytotoxic T lymphocytes (CTLs). In the first case, a 27-year-old male who received haploidentical transplantation to treat T-cell acute lymphoblastic leukemia (T-ALL), developed CMV encephalitis during the time of the ganciclovir maintenance treatment. After intravenous foscarnet and donor CMV-specific CTLs, CMV-DNA of CSF became undetectable and the abnormal signs of brain magnetic resonance imaging (MRI) were limited. Another case, a 57-year-old female with acute myeloid leukemia (AML) who underwent haploidentical transplantation, also developed CMV encephalitis during the maintenance treatment of the ganciclovir. After administering donor CMV-specific CTLs intrathecally, the CMV load of the CSF decreased.Conclusions: The intravenous/intratheca administration of donor CMV-specific CTLs may be a safe and effective treatment for CMV encephalitis, especially for patients who suffered from drug-resistant CMV infection.

Identifying Cytomegalovirus Complications Using the Quantiferon-CMV Assay After Allogeneic Hematopoietic Stem Cell Transplantation

Background

A simple test to identify recovery of CMV-specific T-cell immunity following hematopoietic stem cell transplantation (HSCT) could assist clinicians in managing CMV-related complications.

Methods

In an observational, multicenter, prospective study of 94 HSCT recipients we evaluated CMV-specific T-cell immunity at baseline, 3, 6, 9, and 12 months after transplant using the Quantiferon-CMV, an enzyme-linked immunosorbent spot assay (ELISpot), and intracellular cytokine staining.

Results

At 3 months after HSCT, participants who developed CMV disease (n = 8) compared with CMV reactivation (n = 26) or spontaneous viral control (n = 25) had significantly lower CD8+ T-cell production of interferon-γ (IFN-γ) in response to CMV antigens measured by Quantiferon-CMV (P = .0008). An indeterminate Quantiferon-CMV result had a positive predictive value of 83% and a negative predictive value of 98% for identifying participants at risk of further CMV reactivation. Participants experiencing CMV reactivation compared with patients without CMV reactivation had a reduced proportion of polyfunctional (IFN-γ+/tumor necrosis factor α-positive) CD4+ and CD8+ T cells and a higher proportion of interleukin 2-secreting cells (P = .01 and P = .002, respectively).

Conclusions

Quantifying CMV-specific T-cell immunity after HSCT can identify participants at increased risk of clinically relevant CMV-related outcomes.

Relationship between T-cell receptor beta chain sequences and human cytomegalovirus infection in allogeneic hematopoietic stem cell transplant recipients

In the present study, clonal amplifications of T-cell receptor β variable (TCR BV) linked to human cytomegalovirus (HCMV) infection were detected in recipients of allogeneic hematopoietic stem cell transplants (HSCT), and certain relationships between them were identified. Furthermore, the relationship between TCR BV sequences and HCMV infections was investigated. The results indicated that the 3 recipients of HSCT had monoclonal expansion of specific TCR BV clones following HSCT. Among these recipients, 2 suffered from pp65 and immediate early (IE) antigenemia. These patients demonstrated preferential expansion of TCR BV9 (QVRGGTDTQ) and TCR BV11 (VATDFQ). The remaining recipient did not express TCR BV9 and TCR BV11, nor did this individual have pp65 and IE antigenemia. These results suggest that expression of TCR BV9 and TCR BV11 may be associated with HCMV antigenemia, and may be involved in the immune response. The amino acid sequences 'QVRGGTDTQ' and 'VATDFQ' may be involved in HCMV reactivation in patients who have undergone HSCT. Assessment of the TCR BV families may provide valuable insight into HCMV pathogenesis and may aid in the diagnosis and therapy for HSCT recipients infected with HCMV.

Enzyme-Linked Immunosorbent Spot Assay for the Detection of Wilms' Tumor 1-Specific T Cells Induced by Dendritic Cell Vaccination

BACKGROUND

Despite recent advances in cancer immunotherapy and the development of various assays for T cell assessment, a lack of universal standards within immune monitoring remains. The objective of this study was to evaluate the enzyme-linked immunosorbent spot (ELISpot) assay in comparison with major histocompatibility complex-tetramer analysis in the context of dendritic cell (DC)-based cancer immunotherapy.

METHODS

The ELISpot assay was performed on peripheral blood mononuclear cells to assess reproducibility, daily precision, and linearity using HLA-A*24:02-restricted Cytomegalovirus peptide. Wilms' tumor 1 (WT1) antigen-specific cytotoxic T cells were then evaluated by both the ELISpot assay and WT1 tetramer analysis in peripheral blood from 46 cancer patients who received DC vaccinations pulsed with human leukocyte antigen (HLA)-A*24:02-restricted modified WT1 peptides.

RESULTS

The ELISpot assay was proven to have reproducibility (coefficient of variation (CV) ranged from 7.4% to 16.3%), daily precision (CV ranged from 5.0% to 17.3%), and linearity (r = 0.96-0.98). WT1-specific immune responses were detected by the ELISpot assay in 34 out of 46 patients (73.9%) post-vaccination. A Spearman's rank-correlation coefficient of 0.82 between the ELISpot assay and WT1 tetramer analysis was obtained.

CONCLUSION

This is the first report of a comparison of an ELISpot assay and tetramer analysis in the context of dendritic cell (DC)-based cancer immunotherapy. The ELISpot assay has reproducibility, linearity, and excellent correlation with the WT1 tetramer analysis. These findings suggest that the validated ELISpot assay is useful to monitor the acquired immunity by DC vaccination targeting WT1.

Trypanosoma-Cruzi Cross-Reactive Antibodies Longitudinal Follow-Up: A Prospective Observational Study in Hematopoietic Stem Cell Transplantation

Antibodies named TcCRA "Trypanosoma cruzi Cross Reactive Antibodies" were detected in 47% of blood donors from French population unexposed to the parasite. In order to evaluate the passive or active transmissibility of TcCRA and further characterize its role and etiology, we have conducted a study in a cohort of 47 patients who underwent allogeneic Hematopoietic Stem Cell Transplantations (allo-HSCT). Donors and recipients were tested for TcCRA prior to transplantation. Recipients were further tested during follow-up after transplantation. Demographical, clinical and biological data were collected. Our primary end-point was to assess the risk of TcCRA acquisition after transplantation. During this initial analysis, we observed no seroconversion in patients receiving cells from TcCRA negative donors (n = 23) but detected seroconversion in 4 out of 24 patients who received hematopoietic stem cells from positive donors. Here, we are discussing possible scenarios to explain TcCRA-immune status in recipient after transplantation.

CMV reactivation drives posttransplant T-cell reconstitution and results in defects in the underlying TCRβ repertoire

Although cytomegalovirus (CMV) reactivation has long been implicated in posttransplant immune dysfunction, the molecular mechanisms that drive this phenomenon remain undetermined. To address this, we combined multiparameter flow cytometric analysis and T-cell subpopulation sorting with high-throughput sequencing of the T-cell repertoire, to produce a thorough evaluation of the impact of CMV reactivation on T-cell reconstitution after unrelated-donor hematopoietic stem cell transplant. We observed that CMV reactivation drove a >50-fold specific expansion of Granzyme B(high)/CD28(low)/CD57(high)/CD8(+) effector memory T cells (Tem) and resulted in a linked contraction of all naive T cells, including CD31(+)/CD4(+) putative thymic emigrants. T-cell receptor β (TCRβ) deep sequencing revealed a striking contraction of CD8(+) Tem diversity due to CMV-specific clonal expansions in reactivating patients. In addition to querying the topography of the expanding CMV-specific T-cell clones, deep sequencing allowed us, for the first time, to exhaustively evaluate the underlying TCR repertoire. Our results reveal new evidence for significant defects in the underlying CD8 Tem TCR repertoire in patients who reactivate CMV, providing the first molecular evidence that, in addition to driving expansion of virus-specific cells, CMV reactivation has a detrimental impact on the integrity and heterogeneity of the rest of the T-cell repertoire. This trial was registered at www.clinicaltrials.gov as #NCT01012492.

CMV specific cytokine release assay in whole blood is optimized by combining synthetic CMV peptides and toll like receptor agonists

BACKGROUND

Interferon gamma release assays (IGRAs) are widely used to detect pathogen specific cellular immunity. Cytomegalovirus (CMV) is the foremost problematic viral infection in immunocompromised patients such as transplant or HIV infected patients. CMV antibody ELISAs are not able to predict CMV specific cellular immunity during immunosuppression. We developed a CMV specific IGRA comparing synthetic CMV peptides, native lysate and recombinant antigen. In addition, TLR agonists were tested to enhance CMV antigen immunogenicity.

METHODS

397 healthy controls (HC) were stratified according to CMV IgM and IgG serostatus and subsequently tested for IFNγ- and IL2-secretion in whole blood after challenge with synthetic, native or recombinant CMV antigens and TLR agonists by ELISA. The selected TLR agonists were lipopolysaccharide (LPS), lipoteichoic acid (LTA), peptidoglycan (PGN), zymosan (Zym), polyinosinic-polycytidylic acid (Poly(I:C)), flagellin (Fla), R848, loxoribine (Lox) and bropirimine (Bro).

RESULTS

Synthetic pp65 peptides elicited strong IFNγ responses in CMV seropositive, but not seronegative HC (6418 vs. 13 pg/ml). Native lysates and recombinant pp65 induced equally high IFNγ responses in seropositive (35,877 and 26,428 pg/ml) and increased background IFNγ expression in seronegative HC (43 and 1148 pg/ml). Diagnostic sensitivity and specificity with regard to anti-CMV serology reached 100% for synthetic pp65 and native CMV lysate, but 57% and 100% for recombinant pp65, respectively. TLR agonists LTA and Poly(I:C) augmented IFNγ responses after challenge with synthetic pp65 peptide, native lysate or recombinant pp65 in seropositive HC. Seronegative HC remained unaffected. IL2 production was negligible compared to IFNγ.

CONCLUSION

IGRAs using synthetic CMV peptides or native lysate showed the best cytokine signal to noise ratio compared to recombinant antigen and TLR agonists LTA and Poly(I:C) constitute potential costimulating reagents.