Clinical aspects of CMV infection after stem cell transplantation

Early detection, reactivation of cytomegalovirus DNA & immediate early (IE)-mRNA expression in hematopoietic stem cell-transplant patients

BACKGROUND

Human cytomegalovirus (HCMV) reactivation is a major cause of morbidity and mortality among stem cell transplant recipients post-transplantation.

AIM

HCMV immediate-early messenger RNA (IE-mRNA) was evaluated as marker of post-transplant HCMV reactivation in bone marrow transplant recipients.

METHOD

ology: An in-house real-time reverse transcriptase PCR targeting IE-mRNA was developed to estimate HCMV mRNA levels post-transplantation. Blood samples collected in K2-EDTA tubes from patients (n = 162) admitted with Department of Clinical Hematology were transported in cold condition for routine HCMV DNA screening. For HCMV IE-mRNA quantification, peripheral blood mononuclear cells (PBMCs) were separated from whole blood and stored in RNA later at -70 °C until testing. Samples were collected weekly once for first 3 weeks post-transplantation and thereafter from week 4-12, samples were collected twice weekly. A total of 2467 samples were collected from 162 study participants.

RESULTS

Thirty five patients (21.6 %) had post-transplant HCMV reactivation. Twenty five patients with complete follow-up were selected for monitoring HCMV DNA. HCMV IE-mRNA PCR was performed for 15 patients and 7(46.6 %) patients had detectable mRNA levels. HCMV IE-mRNA was detected in all patients with increasing HCMV DNA levels except for one patient in whom IE-mRNA appeared 3 days before HCMV DNA was detected. One patient had detectable HCMV IE-mRNA during declining HCMV DNA level. However the patient showed an increased HCMV DNA one week later, indicating the importance of HCMV mRNA in predicting HCMV replication.

CONCLUSION

Quantification of HCMV IE-mRNA may be a valuable tool to predict progression of HCMV infection post-transplantation, with further prospective studies needed for validation.

Prognosis of Human Cytomegalovirus in Cancer Patients Undergoing Chemotherapeutic Treatment in Egypt and an Emergent Prevalence of Glycoprotein B-5

The human cytomegalovirus (HCMV) is a global opportunistic β-herpes virus causing severe diseases in immune-compromised patients, such as malignant tumor patients, especially those undergoing chemotherapeutic treatment. This study aimed to determine the prevalence of HCMV-DNA in chemotherapeutic treatment naive cancer patients, and after chemotherapy, to compare between conventional nested PCR and ELISA techniques for the detection of HCMV, and to detect glycoprotein B genotypes. Plasma and serum samples before and after three chemotherapy cycles were collected from 49 chemotherapy-naive cancer patients. DNA was extracted from plasma samples using QIAamp® DNA Mini kit. HCMV-DNA was detected using a nested PCR technique. Multiplex nested PCR was used for HCMV-glycoprotein B (gB) genotyping. HCMV-IgG and -IgM were detected using ELISA technique. Thirty one (63.3 %) of the 49 plasma samples of the chemotherapy-naïve cancer patients were positive for HCMV-DNA; 21 of which remained positive after chemotherapy. However, 18 samples were negative of which 16 became positive after chemotherapy. gB-5 was the most common glycoprotein genotype detected (80.6 %), followed by gB-1, gB-3, gB-4, and gB-2. HCMV IgG was detected in the 49 serum samples of chemotherapy-naïve patients, and after exposure to chemotherapy. HCMV-DNA is commonly identified in cancer patients. Its detection after chemotherapy exposure may suggest HCMV reactivation. The most common genotype detected in cancer patients in Egypt is gB-5 in contrast to earlier research. IgG was detected in all patients. This indicates that HCMV is endemic in Egypt, necessitating the development of public awareness campaigns about HCMV infection and preventive strategies.

Public T-Cell Receptors (TCRs) Revisited by Analysis of the Magnitude of Identical and Highly-Similar TCRs in Virus-Specific T-Cell Repertoires of Healthy Individuals

Since multiple different T-cell receptor (TCR) sequences can bind to the same peptide-MHC combination and the number of TCR-sequences that can theoretically be generated even exceeds the number of T cells in a human body, the likelihood that many public identical (PUB-I) TCR-sequences frequently contribute to immune responses has been estimated to be low. Here, we quantitatively analyzed the TCR-repertoires of 190 purified virus-specific memory T-cell populations, directed against 21 epitopes of Cytomegalovirus, Epstein-Barr virus and Adenovirus isolated from 29 healthy individuals, and determined the magnitude, defined as prevalence within the population and frequencies within individuals, of PUB-I TCR and of TCR-sequences that are highly-similar (PUB-HS) to these PUB-I TCR-sequences. We found that almost one third of all TCR nucleotide-sequences represented PUB-I TCR amino-acid (AA) sequences and found an additional 12% of PUB-HS TCRs differing by maximally 3 AAs. We illustrate that these PUB-I and PUB-HS TCRs were structurally related and contained shared core-sequences in their TCR-sequences. We found a prevalence of PUB-I and PUB-HS TCRs of up to 50% among individuals and showed frequencies of virus-specific PUB-I and PUB-HS TCRs making up more than 10% of each virus-specific T-cell population. These findings were confirmed by using an independent TCR-database of virus-specific TCRs. We therefore conclude that the magnitude of the contribution of PUB-I and PUB-HS TCRs to these virus-specific T-cell responses is high. Because the T cells from these virus-specific memory TCR-repertoires were the result of successful control of the virus in these healthy individuals, these PUB-HS TCRs and PUB-I TCRs may be attractive candidates for immunotherapy in immunocompromised patients that lack virus-specific T cells to control viral reactivation.

Multipotent Stromal Cells and Viral Interaction: Current Implications for Therapy

Multipotent stromal cells (MSCs) are widely utilized in therapy for their immunomodulatory properties, but their usage in infectious viral diseases is less explored. This review aimed to collate the current novel use of MSCs in virus-associated conditions, including MSC's susceptibility to virus infection, antiviral properties of MSCs and their effects on cell-based immune response and implementation of MSC therapy in animal models and human clinical trials of viral diseases. Recent discoveries shed lights on MSC's capability in suppressing viral replication and augmenting clearance through enhancement of antiviral immunity. MSC therapy may maintain a crucial balance between aiding pathogen clearance and suppressing hyperactive immune response.

Therapeutic Vaccination of Hematopoietic Cell Transplantation Recipients Improves Protective CD8 T-Cell Immunotherapy of Cytomegalovirus Infection

Reactivation of latent cytomegalovirus (CMV) endangers the therapeutic success of hematopoietic cell transplantation (HCT) in tumor patients due to cytopathogenic virus spread that leads to organ manifestations of CMV disease, to interstitial pneumonia in particular. In cases of virus variants that are refractory to standard antiviral pharmacotherapy, immunotherapy by adoptive cell transfer (ACT) of virus-specific CD8+ T cells is the last resort to bridge the "protection gap" between hematoablative conditioning for HCT and endogenous reconstitution of antiviral immunity. We have used the well-established mouse model of CD8+ T-cell immunotherapy by ACT in a setting of experimental HCT and murine CMV (mCMV) infection to pursue the concept of improving the efficacy of ACT by therapeutic vaccination (TherVac) post-HCT. TherVac aims at restimulation and expansion of limited numbers of transferred antiviral CD8+ T cells within the recipient. Syngeneic HCT was performed with C57BL/6 mice as donors and recipients. Recipients were infected with recombinant mCMV (mCMV-SIINFEKL) that expresses antigenic peptide SIINFEKL presented to CD8+ T cells by the MHC class-I molecule Kb. ACT was performed with transgenic OT-I CD8+ T cells expressing a T-cell receptor specific for SIINFEKL-Kb. Recombinant human CMV dense bodies (DB-SIINFEKL), engineered to contain SIINFEKL within tegument protein pUL83/pp65, served for vaccination. DBs were chosen as they represent non-infectious, enveloped, and thus fusion-competent subviral particles capable of activating dendritic cells and delivering antigens directly into the cytosol for processing and presentation in the MHC class-I pathway. One set of our experiments documents the power of vaccination with DBs in protecting the immunocompetent host against a challenge infection. A further set of experiments revealed a significant improvement of antiviral control in HCT recipients by combining ACT with TherVac. In both settings, the benefit from vaccination with DBs proved to be strictly epitope-specific. The capacity to protect was lost when DBs included the peptide sequence SIINFEKA lacking immunogenicity and antigenicity due to C-terminal residue point mutation L8A, which prevents efficient proteasomal peptide processing and binding to Kb. Our preclinical research data thus provide an argument for using pre-emptive TherVac to enhance antiviral protection by ACT in HCT recipients with diagnosed CMV reactivation.

Immunodominant Cytomegalovirus Epitopes Suppress Subdominant Epitopes in the Generation of High-Avidity CD8 T Cells

CD8⁺ T-cell responses to pathogens are directed against infected cells that present pathogen-encoded peptides on MHC class-I molecules. Although natural responses are polyclonal, the spectrum of peptides that qualify for epitopes is remarkably small even for pathogens with high coding capacity. Among those few that are successful at all, a hierarchy exists in the magnitude of the response that they elicit in terms of numbers of CD8⁺ T cells generated. This led to a classification into immunodominant and non-immunodominant or subordinate epitopes, IDEs and non-IDEs, respectively. IDEs are favored in the design of vaccines and are chosen for CD8⁺ T-cell immunotherapy. Using murine cytomegalovirus as a model, we provide evidence to conclude that epitope hierarchy reflects competition on the level of antigen recognition. Notably, high-avidity cells specific for non-IDEs were found to expand only when IDEs were deleted. This may be a host’s back-up strategy to avoid viral immune escape through antigenic drift caused by IDE mutations. Importantly, our results are relevant for the design of vaccines based on cytomegaloviruses as vectors to generate high-avidity CD8⁺ T-cell memory specific for unrelated pathogens or tumors. We propose the deletion of vector-encoded IDEs to avoid the suppression of epitopes of the vaccine target.

Magnitude of Off-Target Allo-HLA Reactivity by Third-Party Donor-Derived Virus-Specific T Cells Is Dictated by HLA-Restriction

T-cell products derived from third-party donors are clinically applied, but harbor the risk of off-target toxicity via induction of allo-HLA cross-reactivity directed against mismatched alleles. We used third-party donor-derived virus-specific T cells as model to investigate whether virus-specificity, HLA restriction and/or HLA background can predict the risk of allo-HLA cross-reactivity. Virus-specific CD8^pos T cells were isolated from HLA-A^*01:01/B^*08:01 or HLA-A^*02:01/B^*07:02 positive donors. Allo-HLA cross-reactivity was tested using an EBV-LCL panel covering 116 allogeneic HLA molecules and confirmed using K562 cells retrovirally transduced with single HLA-class-I alleles of interest. HLA-B^*08:01-restricted T cells showed the highest frequency and diversity of allo-HLA cross-reactivity, regardless of virus-specificity, which was skewed toward multiple recurrent allogeneic HLA-B molecules. Thymic selection for other HLA-B alleles significantly influenced the level of allo-HLA cross-reactivity mediated by HLA-B^*08:01-restricted T cells. These results suggest that the degree and specificity of allo-HLA cross-reactivity by T cells follow rules. The risk of off-target toxicity after infusion of incompletely matched third-party donor-derived virus-specific T cells may be reduced by selection of T cells with a specific HLA restriction and background.

Flow cytometric measurement of STAT5 phosphorylation in cytomegalovirus-stimulated T cells

Cytomegalovirus (CMV)-specific T cells expand with CMV reactivation and are probably prerequisite for control and protection. Given the critical role STAT5A phosphorylation (pSTAT5A) in T cell proliferation, this study presents a simple and sensitive flow cytometric-based pSTAT5A assay to quickly identify CMV-specific T cell proliferation. We determined pSTAT5A in T cells treated with CMV-specific peptide mix (pp65 + IE1 peptides) from 20 healthy adult subjects and three immunodeficient patients with CARMIL-2 mutation. After stimulation, the percentage of pSTAT5A⁺ T cells in CMV-seropositive (CMV⁺ ) subjects significantly increased from 3.0% ± 1.9% (unstimulated) to 11.4% ± 5.9% (stimulated) for 24 h. After 7 days of stimulation, the percentage of expanded T cells amounted to 26% ± 17.2%. Conversely, the percentage of pSTAT5A⁺ T cells and T cell proliferation from CMV-seronegative (CMV^- ) subjects hardly changed (from 3.0% ± 1.3% to 3.7% ± 1.8% and from 4.3% ± 2.1% to 5.7% ± 1.7%, respectively). We analyzed the correlation between the percentage of pSTAT5A⁺ T cells versus (1) CMV-IgG concentrations versus (2) the percentage of expanded T cells and versus (3) the percentage of initial CMV-specific T cells. In immunodeficient patients with CARMIL-2 mutation, CMV-specific pSTAT5A and T cell proliferation were completely deficient. In conclusion, flow cytometric-based pSTAT5A assay represents an appropriate tool to quickly identify CMV-specific T cell proliferation and helps to understand dysfunctions in controlling other pathogens. Flow cytometric-based pSTAT5A assay may be a useful test in clinical practice and merits further validation in large studies.

Presence of Parvovirus B19 but Not Herpesvirus Genome in Acute Skin Rash after Allogeneic Stem Cell Transplantation Correlates with Outcome

INTRODUCTION

Skin rash is a first symptom of acute graft-versus-host disease (GvHD) after allogeneic stem cell transplantation (ASCT) but can also be caused by viruses. The relevance of virus DNA analyses in skin rash for diagnosis and clinical outcome is unknown.

OBJECTIVES

To record the frequencies of detection of herpes and parvovirus B19 (ParvoB19) DNA in skin rash within 100 days after ASCT and to analyze their relevance for diagnosis, clinical course, and non-relapse mortality (NRM).

METHODS

We retrospectively identified 55 patients with virus DNA analysis for CMV, EBV, HHV6, HHV8, HSV, VZV, or ParvoB19. We assessed the rate of virus DNA detection and studied associations with histological diagnosis, virus DNA from concomitantly analyzed blood, clinical presentation, exanthema treatment, and NRM.

RESULTS

CMV, EBV, HHV6, HHV8, HSV, VZV and ParvoB19 DNA were detected in 12.5, 11.8, 10, 0, 0, 2.9, and 26.7% of exanthemas. Histopathological diagnosis was not associated with virus polymerase chain reaction (PCR) results. Detection of CMV, EBV, or HHV6 DNA but not ParvoB19 in skin and blood was associated with PCR results (p = 0.016; p < 0.001; p = 0.067; p = n.a.). Detection of CMV, EBV, HHV6, or ParvoB19 DNA in the skin was not significantly associated with patient, ASCT, or GvHD characteristics. Detection of ParvoB19 but not herpes virus DNA was associated with less immunosuppressive treatment (p = 0.015) and lower NRM (p = 0.041). In multivariate analyses, detection of ParvoB19 was associated with a lower NRM.

CONCLUSIONS

Detection of ParvoB19 DNA in exanthema after ASCT might be associated with lower NRM.

Cytomegalovirus glycoprotein B and N genotypes in pediatric recipients of the hematopoietic stem cell transplant

Clinical significance of the cytomegalovirus (CMV) genotypes in patients undergoing allogeneic hematopoietic stem cell transplant (HSCT) has been evaluated mostly in adults. The studies of diverse CMV glycoprotein B (gB) and N (gN) genotype variants in transplanted children and adolescents are lacking. We analyzed the investment of gB and gN genotype variants in the HSCTed children and their relation to clinical complications and disease outcome. The cohort included forty two pediatric recipients of the HSCT. Patients positive for CMV DNAemia (24/42, 57.1%) were genotyped. The gB4 and gN1 genotype variants predominated and were evidenced in 7/18 (38.9%) and 9/19 (47.4%) patients, respectively. The graft-versus-host disease (GvHD) predominated in children with viremia (p < 0.05). Frequencies of the gB and gN genotypes contrasted those reported in recent studies. The GvHD scaled strongly with CMV reactivation whereas viral loads were uncorrelated to medical complications and treatment outcomes.

Enhancement of Antigen Presentation by Deletion of Viral Immune Evasion Genes Prevents Lethal Cytomegalovirus Disease in Minor Histocompatibility Antigen-Mismatched Hematopoietic Cell Transplantation

Hematoablative treatment followed by hematopoietic cell transplantation (HCT) for reconstituting the co-ablated immune system is a therapeutic option to cure aggressive forms of hematopoietic malignancies. In cases of family donors or unrelated donors, immunogenetic mismatches in major histocompatibility complex (MHC) and/or minor histocompatibility (minor-H) loci are unavoidable and bear a risk of graft-vs.-host reaction and disease (GvHR/D). Transient immunodeficiency inherent to the HCT protocol favors a productive reactivation of latent cytomegalovirus (CMV) that can result in multiple-organ CMV disease. In addition, there exists evidence from a mouse model of MHC class-I-mismatched GvH-HCT to propose that mismatches interfere with an efficient reconstitution of antiviral immunity. Here we used a mouse model of MHC-matched HCT with C57BL/6 donors and MHC-congenic BALB.B recipients that only differ in polymorphic autosomal background genes, including minor-H loci coding for minor-H antigens (minor-HAg). Minor-HAg mismatch is found to promote lethal CMV disease in absence of a detectable GvH response to an immunodominant minor-HAg, the H60 locus-encoded antigenic peptide LYL8. Lethality of infection correlates with inefficient reconstitution of viral epitope-specific CD8⁺ T cells. Notably, lethality is prevented and control of cytopathogenic infection is restored when viral antigen presentation is enhanced by deletion of immune evasion genes from the infecting virus. We hypothesize that any kind of mismatch in GvH-HCT can induce "non-cognate transplantation tolerance" that dampens not only a mismatch-specific GvH response, which is beneficial, but adversely affects also responses to mismatch-unrelated antigens, such as CMV antigens in the specific case, with the consequence of lethal CMV disease.

The CD4+ T Cell Response to Human Cytomegalovirus in Healthy and Immunocompromised People

While CD8+ T cells specific for human cytomegalovirus (HCMV) have been extensively studied in both healthy HCMV seropositive carriers and patients undergoing immunosuppression, studies on the CD4+ T cell response to HCMV had lagged behind. However, over the last few years there has been a significant advance in our understanding of the importance and contribution that CMV-specific CD4+ T cells make, not only to anti-viral immunity but also in the potential maintenance of latently infected cells. During primary infection with HCMV in adults, CD4+ T cells are important for the resolution of symptomatic disease, while persistent shedding of HCMV into urine and saliva is associated with a lack of HCMV specific CD4+ T cell response in young children. In immunosuppressed solid organ transplant recipients, a delayed appearance of HCMV-specific CD4+ T cells is associated with prolonged viremia and more severe clinical disease, while in haematopoietic stem cell transplant recipients, it has been suggested that HCMV-specific CD4+ T cells are required for HCMV-specific CD8+ T cells to exert their anti-viral effects. In addition, adoptive T-cell immunotherapy in transplant patients has shown that the presence of HCMV-specific CD4+ T cells is required for the maintenance of HCMV-specific CD8+ T cells. HCMV is a paradigm for immune evasion. The presence of viral genes that down-regulate MHC class II molecules and the expression of viral IL-10 both limit antigen presentation to CD4+ T cells, underlining the important role that this T cell subset has in antiviral immunity. This review will discuss the antigen specificity, effector function, phenotype and direct anti-viral properties of HCMV specific CD4+ T cells, as well as reviewing our understanding of the importance of this T cell subset in primary infection and long-term carriage in healthy individuals. In addition, their role and importance in congenital HCMV infection and during immunosuppression in both solid organ and haemopoietic stem cell transplantation is considered.

Insufficient Antigen Presentation Due to Viral Immune Evasion Explains Lethal Cytomegalovirus Organ Disease After Allogeneic Hematopoietic Cell Transplantation

Reactivation of latent cytomegalovirus (CMV) poses a clinical problem in transiently immunocompromised recipients of hematopoietic cell (HC) transplantation (HCT) by viral histopathology that results in multiple organ manifestations. Compared to autologous HCT and to syngeneic HCT performed with identical twins as HC donor and recipient, lethal outcome of CMV infection is more frequent in allogeneic HCT with MHC/HLA or minor histocompatibility loci mismatch between donor and recipient. It is an open question if a graft-vs.-host (GvH) reaction exacerbates CMV disease, or if CMV exacerbates GvH disease (GvHD), or if interference is mutual. Here we have used a mouse model of experimental HCT and murine CMV (mCMV) infection with an MHC class-I mismatch by gene deletion, so that either HCT donor or recipient lack a single MHC class-I molecule, specifically H-2 Ld. This particular immunogenetic disparity has the additional advantage that it allows to experimentally separate GvH reaction of donor-derived T cells against recipient's tissues from host-vs.-graft (HvG) reaction of residual recipient-derived T cells against the transplanted HC and their progeny. While in HvG-HCT with Ld-plus donors and Ld-minus recipients almost all infected recipients were found to control the infection and survived, almost all infected recipients died of uncontrolled virus replication and consequent multiple-organ viral histopathology in case of GvH-HCT with Ld-minus donors and Ld-plus recipients. Unexpectedly, although anti-Ld-reactive CD8+ T cells were detected, mortality was not found to be associated with GvHD histopathology. By comparing HvG-HCT and GvH-HCT, investigation into the mechanism revealed an inefficient reconstitution of antiviral high-avidity CD8+ T cells, associated with lack of formation of protective nodular inflammatory foci (NIF) in host tissue, selectively in GvH-HCT. Most notably, mice infected with an immune evasion gene deletion mutant of mCMV survived under otherwise identical GvH-HCT conditions. Survival was associated with enhanced antigen presentation and formation of protective NIF by antiviral CD8+ T cells that control the infection and prevent viral histopathology. This is an impressive example of lethal viral disease in HCT recipients based on a failure of the immune control of CMV infection due to viral immune evasion in concert with an MHC class-I mismatch.

Identification of the best-suited donor for generating virus-specific T cells

BACKGROUND AND OBJECTIVES

Administration of virus-specific T cells (VSTs) is a viable antiviral treatment strategy after allogeneic HSCT, even if conventional therapies fail. Third-party donors are often chosen for the generation of the VST product. The eligibility of the donor has to be tested in a rigorous donor screening procedure, since the isolation technology only targets pre-existing VSTs.

MATERIALS AND METHODS

In a period of 3 years, we performed 32 VST treatments for 28 patients. Targeting four different viruses, 284 healthy individuals underwent 417 donor screening procedures. VSTs were counted by flow cytometry detecting interferon-gamma (IFN-γ) producing T cells. Generation of the VSTs was performed from leukapheresis products in a fully automated and closed system using magnetic cell separation.

RESULTS

The mean circulating VST frequencies ranged from 0·006% to 0·328%. The average yield of viable VSTs in the product was 1·83·10₆ cells, while the average VST dose calculated for the patient's body weight was 4·63·10₄ /kg. The mean purity - percentage of VSTs within the T cells - of all T-cell products was 62·9%. Correlation was identified between the frequency of the VSTs in the peripheral blood of the donor and the VST numbers of the end product; the strongest correlation was seen for CMV.

CONCLUSION

This paper focuses on the T-cell donors, highlighting some key points on the donor selection process. Based on the findings in connection with the CMV therapies, peripheral VST seems to be the best predictor of the VST content of the final product administered to the patient.

Robust Identification of Suitable T-Cell Subsets for Personalized CMV-Specific T-Cell Immunotherapy Using CD45RA and CD62L Microbeads

Viral infections and reactivations remain a serious obstacle to successful hematopoietic stem cell transplantation (HSCT). When antiviral drug treatment fails, adoptive virus-specific T-cell transfer provides an effective alternative. Assuming that naive T cells (T_N) are mainly responsible for GvHD, methods were developed to generate naive T-cell-depleted products while preserving immune memory against viral infections. We compared two major strategies to deplete potentially alloreactive T cells: CD45RA and CD62L depletion and analyzed phenotype and functionality of the resulting CD45RA^-/CD62L^- naive T-cell-depleted as well as CD45RA⁺/CD62L⁺ naive T-cell-enriched fractions in the CMV pp65 and IE1 antigen model. CD45RA depletion resulted in loss of terminally differentiated effector memory T cells re-expressing CD45RA (T_EMRA), and CD62L depletion in loss of central memory T cells (T_CM). Based on these differences in target cell-dependent and target cell-independent assays, antigen-specific T-cell responses in CD62L-depleted fraction were consistently 3⁻5 fold higher than those in CD45RA-depleted fraction. Interestingly, we also observed high donor variability in the CD45RA-depleted fraction, resulting in a substantial loss of immune memory. Accordingly, we identified donors with expected response (DER) and unexpected response (DUR). Taken together, our results showed that a naive T-cell depletion method should be chosen individually, based on the immunophenotypic composition of the T-cell populations present.

Quantiferon-Cytomegalovirus assay: A potentially useful tool in the evaluation of CMV-specific CD8+ T-cell reconstitution in pediatric hematopoietic stem cell transplant patients

Pediatric HSCT recipients are at high risk for CMV reactivation due to their immature immune system and therapy following transplantation. Reconstitution of CMV-specific T-cell immunity is associated with control and protection against CMV. The clinical utility of monitoring CMV-specific CMI to predict CMV viremia in pediatric HSCT patients using the Quantiferon-CMV (QIAGEN^® ) test was investigated prospectively. Thirty-seven pediatric allogeneic HSCT recipients were enrolled from 3/2010-6/2012. CMV viremia was detected via weekly real-time PCR. The Quantiferon-CMV test was conducted pretransplant, early after transplantation, 30, 90, 180, 270, and 360 days post-transplantation. The incidence of CMV viremia was 51% (19/37) with half of the episodes within ≤30 days post-transplant. Fifteen patients showed CMV-specific immunity (average of 82 days). The cumulative incidence of CMV reactivation in patients who developed CMV-specific immunity was lower than those who did not (15% vs 53%; P = .023). The ROC statistical analysis showed that the AUC was 0.725 in predicting viremia, for Quantiferon-CMV test. In this cohort, the Quantiferon-CMV assay was a valuable method for identifying pediatric HSCT patients at high risk for CMV viremia, suggesting potential clinical utility to individualize patient's management post-transplant.

Cytomegalovirus induces HLA-class-II-restricted alloreactivity in an acute myeloid leukemia cell line

Cytomegalovirus (HCMV) reactivation is found frequently after allogeneic hematopoietic stem cell transplantation (alloSCT) and is associated with an increased treatment-related mortality. Recent reports suggest a link between HCMV and a reduced risk of cancer progression in patients with acute leukemia or lymphoma after alloSCT. Here we show that HCMV can inhibit the proliferation of the acute myeloid leukemia cell line Kasumi-1 and the promyeloid leukemia cell line NB4. HCMV induced a significant up-regulation of HLA-class-II-molecules, especially HLA-DR expression and an increase of apoptosis, granzyme B, perforin and IFN-γ secretion in Kasumi-1 cells cocultured with peripheral blood mononuclear cells (PBMCs). Indolamin-2,3-dioxygenase on the other hand led only to a significant dose-dependent effect on IFN-γ secretion without effects on proliferation. The addition of CpG-rich oligonucleotides and ganciclovir reversed those antiproliferative effects. We conclude that HCMV can enhance alloreactivity of PBMCs against Kasumi-1 and NB4 cells in vitro. To determine if this phenomenon may be clinically relevant further investigations will be required.

Specific Adoptive T-Cell Therapy for Viral and Fungal Infections

Despite advances in anti-infective agents, viral and fungal infections after hematopoietic stem cell transplantation (HSCT) continue to cause life-threatening complications that limit the success of HSCT. Early adoptive T-cell immunotherapy studies showed that administration of allogeneic virus-specific cytotoxic T lymphocytes (vCTL) can prevent and control viral infections and reconstitute antiviral immunity to cytomegalovirus (CMV) and Epstein-Barr virus (EBV). Advances in immunobiology, in vitro culture technology, and current good manufacturing practice (cGMP) have provided opportunities for advancing adoptive cell therapy for viral infections: (1) T cells have been expanded targeting multiple pathogens; (2) vCTL production no longer requires viral infection or viral vector transduction of antigen-presenting cells (APCs); (3) the source of lymphocytes is no longer restricted to donors who are immune to the pathogens; (4) naive T cells have been redirected with chimeric antigen receptor T cells (CARTs) or armed with bispecific antibody-armed T cells (BATs) to mediate vCTL activity; (5) these technologies could be combined to targeted multiple viral or fungal pathogens; and (6) pathogen-specific T-cell products manufactured from third parties and banked for “off-the-shelf” use post-HSCT may soon become a reality.

Mechanisms of human cytomegalovirus infection with a focus on epidermal growth factor receptor interactions

Human cytomegalovirus (HCMV) is a widespread opportunistic herpesvirus that causes severe diseases in immunocompromised individuals. It has a high prevalence worldwide that is linked with socioeconomic factors. Similar to other herpesviruses, HCMV has the ability to establish lifelong persistence and latent infection following primary exposure. HCMV infects a broad range of cell types. This broad tropism suggests that it may use multiple receptors for host cell entry. The identification of receptors used by HCMV is essential for understanding viral pathogenesis, because these receptors mediate the early events necessary for infection. Many cell surface components have been identified as virus receptors, such as epidermal growth factor receptor (EGFR), which is characterized by tyrosine kinase activity and plays a crucial role in the control of key cellular transduction pathways. EGFR is essential for HCMV binding, signaling, and host cell entry. This review focuses on HCMV infection via EGFR on different cell types and its implications for the cellular environment, viral persistence, and infection.

The human cytomegalovirus glycoprotein pUL11 acts via CD45 to induce T cell IL-10 secretion

Human Cytomegalovirus (HCMV) is a widespread pathogen, infection with which can cause severe disease for immunocompromised individuals. The complex changes wrought on the host's immune system during both productive and latent HCMV infection are well known. Infected cells are masked and manipulated and uninfected immune cells are also affected; peripheral blood mononuclear cell (PBMC) proliferation is reduced and cytokine profiles altered. Levels increase of the anti-inflammatory cytokine IL-10, which may be important for the establishment of HCMV infections and is required for the development of high viral titres by murine cytomegalovirus. The mechanisms by which HCMV affects T cell IL-10 secretion are not understood. We show here that treatment of PBMC with purified pUL11 induces IL-10 producing T cells as a result of pUL11 binding to the CD45 phosphatase on T cells. IL-10 production induced by HCMV infection is also in part mediated by pUL11. Supernatants from pUL11 treated cells have anti-inflammatory effects on untreated PBMC. Considering the mechanism, CD45 can be a positive or negative regulator of TCR signalling, depending on its expression level, and we show that pUL11 also has concentration dependent activating or inhibitory effects on T cell proliferation and on the kinase function of the CD45 substrate Lck. pUL11 is therefore the first example of a viral protein that can target CD45 to induce T cells with anti-inflammatory properties. It is also the first HCMV protein shown to induce T cell IL-10 secretion. Understanding the mechanisms by which pUL11-induced changes in signal strength influence T cell development and function may provide the basis for the development of novel antiviral treatments and therapies against immune pathologies.

Cytomegalovirus-Specific T Cells Isolated by IFN-γ Secretion Assay Do Not Induce Significant Graft-Versus-Host Reactions In Vitro

BACKGROUND

Graft-versus-host (GvH) disease (GvHD) remains a serious concern for patients undergoing antiviral cellular therapy. Despite the major improvements in cellular immunotherapy, the immunogenicity of virus-specific T cells has not yet been fully defined. This present study aims to examine how cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CTLs) respond to allogeneic antigen stimulation and whether they give rise to GvHD target tissue damage.

METHODS

Cytomegalovirus-specific CTLs were isolated by the IFN-γ secretion assay (gamma-catch) from healthy seropositive volunteers and expanded in vitro. The levels of intracellular IFN-γ, cytotoxic activity, IFN-γ and granzyme B secretion, and CD25 expression were measured using flow cytometry (fluorescence-activated cell sorting). The ability of CMV-CTLs to induce GvHD target tissue damage was evaluated using the human in vitro skin explant assay (skin explant assay).

RESULTS

Cytomegalovirus-specific CTLs responded specifically to CMV-phosphoprotein 65 stimulation by secreting IFN-γ and killing virus peptide loaded autologous phytohemagglutinin (PHA) blasts. Compared with unselected peripheral blood mononuclear cells, CMV-CTLs induced significantly less severe cutaneous GvH tissue damage. This observation coincided with low levels of CD25 expression, as well as IFN-γ and granzyme B secretion after allogeneic antigen stimulation in both the mixed lymphocyte reaction and in the skin explant assay.

CONCLUSIONS

Cytomegalovirus-specific CTLs isolated by the IFN-γ secretion assay from HLA-unmatched healthy donors exhibited a high level of anti-CMV potency without inducing significant cutaneous GvH tissue damage in vitro. This finding provides novel evidence supporting the safe use of in vitro expanded CMV-CTLs as an antiviral therapy in transplant patients with refractory CMV infections.

Clinical Usefulness of Monitoring Cytomegalovirus-Specific Immunity by Quantiferon-CMV in Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Recipients

Cytomegalovirus (CMV) is a well-established cause of morbidity and mortality in pediatric recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). CD8⁺ T-cells are important for controlling CMV infection. We conducted a prospective pilot study to investigate the clinical utility of measuring the CMV-specific T-cell immune response using the QuantiFERON-CMV assay (QF-CMV) in pediatric allo-HSCT recipients. Overall, 16 of 25 (64%) patients developed CMV infection. QF-CMV was evaluated in these 16 patients during the early and late phases of the first CMV infection post allo-HSCT. Whereas the initial QF-CMV results during the early phase of CMV infection did not correlate with the course of the corresponding infection, the QF-CMV results post resolution of the first CMV infection correlated with the recurrence of CMV infection until 12 months post allo-HSCT; no recurrent infections occurred in the four QF-CMV-positive patients, while recurrent infections manifested in five of eight QF-CMV-negative (62.5%) and all three QF-CMV-indeterminate patients (P=0.019). In spite of the small number of patients examined, this study supports the potential application of monitoring CMV-specific T-cell immunity using the QF-CMV assay to predict the recurrence of CMV infection in pediatric allo-HSCT recipients.

Application of autologous hematopoietic stem cell transplantation for pemphigus

BACKGROUND

Pemphigus is a rare and fatal autoimmune disease for which the treatment options are limited. This study aimed to evaluate the efficacy of autologous peripheral hematopoietic stem cell transplantation (APHSCT) for pemphigus.

METHODS

We conducted APHSCT for 12 pemphigus patients (seven males and five females, mean age 23.8 years) with life-threatening complications or who responded poorly to conventional therapy. Peripheral blood stem cells were mobilized with cyclophosphamide, granulocyte colony-stimulating factor, and rituximab, and purified autologous CD34⁺ stem cells were infused. Overall survival rate, progression-free survival, and adverse events were recorded.

RESULTS

With a mean follow-up period of 80.3 months, overall survival and complete clinical remission rates were 92% (11/12) and 75% (9/12), respectively. Adverse effects included pyrexia, allergy, infection, and elevation of enzymes. Only one patient died of severe sepsis and multiple organ failure 2 months after APHSCT.

CONCLUSION

Overall APHSCT is a promising therapeutic option for pemphigus.

Immunity to Infections after Haploidentical Hematopoietic Stem Cell Transplantation

The advantage of using a Human Leukocyte Antigen (HLA)-mismatched related donor is that almost every patient who does not have an HLA-identical donor or who urgently needs hematopoietic stem cell transplantation (HSCT) has at least one family member with whom shares one haplotype (haploidentical) and who is promptly available as a donor. The major challenge of haplo-HSCT is intense bi-directional alloreactivity leading to high incidences of graft rejection and graft-versus-host disease (GVHD). Advances in graft processing and pharmacologic prophylaxis of GVHD have reduced these risks and have made haplo-HSCT a viable alternative for patients lacking a matched donor. Indeed, the haplo-HSCT has spread to centers worldwide even though some centers have preferred an approach based on T cell depletion of G-CSF-mobilized peripheral blood progenitor cells (PBPCs), others have focused on new strategies for GvHD prevention, such as G-CSF priming of bone marrow and robust post-transplant immune suppression or post-transplant cyclophosphamide (PTCY). Today, the graft can be a megadose of T-cell depleted PBPCs or a standard dose of unmanipulated bone marrow and/or PBPCs. Although haplo-HSCT modalities are based mainly on high intensity conditioning regimens, recently introduced reduced intensity regimens (RIC) showed promise in decreasing early transplant-related mortality (TRM), and extending the opportunity of HSCT to an elderly population with more comorbidities. Infections are still mostly responsible for toxicity and non-relapse mortality due to prolonged immunosuppression related, or not, to GVHD. Future challenges lie in determining the safest preparative conditioning regimen, minimizing GvHD and promoting rapid and more robust immune reconstitution.

Exogenous TNFR2 activation protects from acute GvHD via host T reg cell expansion

Activation of TNFR2 with a novel agonist expands T reg cells in vivo and protects allo-HCT recipients from acute GvHD while sparing antilymphoma and antiinfectious properties of transplanted donor T cells.

Donor CD4⁺Foxp3⁺ regulatory T cells (T reg cells) suppress graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HCT [allo-HCT]). Current clinical study protocols rely on the ex vivo expansion of donor T reg cells and their infusion in high numbers. In this study, we present a novel strategy for inhibiting GvHD that is based on the in vivo expansion of recipient T reg cells before allo-HCT, exploiting the crucial role of tumor necrosis factor receptor 2 (TNFR2) in T reg cell biology. Expanding radiation-resistant host T reg cells in recipient mice using a mouse TNFR2-selective agonist before allo-HCT significantly prolonged survival and reduced GvHD severity in a TNFR2- and T reg cell–dependent manner. The beneficial effects of transplanted T cells against leukemia cells and infectious pathogens remained unaffected. A corresponding human TNFR2-specific agonist expanded human T reg cells in vitro. These observations indicate the potential of our strategy to protect allo-HCT patients from acute GvHD by expanding T reg cells via selective TNFR2 activation in vivo.

Matched unrelated donor transplants-State of the art in the 21st century

Hematopoietic stem cell transplantation (HSCT) is the therapy of choice in many hematological malignant and non-malignant diseases by using human leukocyte antigen (HLA)-matched siblings as stem cell source but only one third of the patients will have HLA-matched siblings. Hence, physicians rely on the availability of matched unrelated donors (URD). The possibility of finding a matched URD is now more than 70% due to continuous expansion of URD registries around the world. The use of URD in adult patients is steadily increasing and in the last 8 years has superseded the numbers of matched sibling donor transplants and has become the most commonly used stem cell source. There is also an increasing trend to use peripheral blood (PB) stem cells rather than bone marrow (BM) stem cells. Outcomes following URD transplants depend mainly upon the indication and urgency of transplant, age and comorbidities of recipients, cytomegalovirus (CMV) matching/mismatching between donor and the recipient, and degree of HLA matching. In some studies outcome of unrelated stem cell transplants in terms of treatment-related mortality (TRM), disease-free survival (DFS), and overall survival (OS) is comparable to sibling donors.

Addition of varicella zoster virus-specific T cells to cytomegalovirus, Epstein-Barr virus and adenovirus tri-specific T cells as adoptive immunotherapy in patients undergoing allogeneic hematopoietic stem cell transplantation

BACKGROUND AIMS

Virus-specific T-cell immunotherapy is emerging as a promising management strategy for virus infections in patients after hematopoietic stem cell transplant (HSCT). Here we present outcomes of 10 adult patients who received multi-virus-specific T cells prophylactically after HSCT.

METHODS

Donor-derived cytomegalovirus (CMV)-, Epstein-Barr virus (EBV)-, adenoviral- and varicella zoster virus (VZV)-specific T cells were generated in a single culture and administered to HSCT patients at a dose of 2 × 10(7)/m(2) virus-specific T cells at a median of 63 days post-transplant. Patients were monitored for 12 months for evidence of viral reactivation and graft-versus-host disease.

RESULTS

There was no acute infusion-related toxicity. Six patients developed CMV reactivation after T-cell infusion with a median peak CMV DNA titer of 600 copies per milliliter, and 1 received CMV-specific pharmacotherapy post-infusion. No EBV, adenoviral or VZV reactivation or disease was reported. Using interferon-γ Elispot analysis on post-infusion samples, we identified anti-viral immunity against all viruses including VZV. Three patients (30%) developed grade II-IV acute graft-versus-host disease.

CONCLUSIONS

This is the first description of the use of a multi-virus-specific T-cell product containing cells specific for VZV after allogeneic HSCT. The T-cell product appears safe in the setting of HSCT and confirms our previous findings regarding CMV control and treatment. A larger study with longer follow-up is required to determine the efficacy of VZV-specific T cells given prophylactically in controlling episodes of herpes zoster and disseminated varicella infection after cessation of prophylactic anti-viral treatment.

Abundant cytomegalovirus (CMV) reactive clonotypes in the CD8(+) T cell receptor alpha repertoire following allogeneic transplantation

Allogeneic stem cell transplantation is potentially curative, but associated with post-transplantation complications, including cytomegalovirus (CMV) infections. An effective immune response requires T cells recognizing CMV epitopes via their T cell receptors (TCRs). Little is known about the TCR repertoire, in particular the TCR-α repertoire and its clinical relevance in patients following stem cell transplantation. Using next-generation sequencing we examined the TCR-α repertoire of CD8(+) T cells and CMV-specific CD8(+) T cells in four patients. Additionally, we performed single-cell TCR-αβ sequencing of CMV-specific CD8(+) T cells. The TCR-α composition of human leucocyte antigen (HLA)-A*0201 CMVpp65- and CMVIE -specific T cells was oligoclonal and defined by few dominant clonotypes. Frequencies of single clonotypes reached up to 11% of all CD8(+) T cells and half of the total CD8(+) T cell repertoire was dominated by few CMV-reactive clonotypes. Some TCR-α clonotypes were shared between patients. Gene expression of the circulating CMV-specific CD8(+) T cells was consistent with chronically activated effector memory T cells. The CD8(+) T cell response to CMV reactivation resulted in an expansion of a few TCR-α clonotypes to dominate the CD8(+) repertoires. These results warrant further larger studies to define the ability of oligoclonally expanded T cell clones to achieve an effective anti-viral T cell response in this setting.

Appearance of cytomegalovirus-specific T-cells predicts fast resolution of viremia post hematopoietic stem cell transplantation

BACKGROUND

Cytomegalovirus (CMV) specific T-cells are known to provide long-term control of CMV reactivation, which is a frequent complication of hematopoietic stem cell transplantation. We have studied 58 pediatric patients after hematopoietic stem cell transplantation who suffered from CMV reactivation to reveal which functional T cell subset is best correlating with successful reactivation resolution and which protects from reactivation episode.

METHODS

Detection of 30 combinatorial subsets of four types of response to ex vivo CMV stimulation (IFNγ secretion, IL-2 secretion, CD40L upregulation and degranulation) that were detectable on either CD8+ or CD4+ T cells through flow cytometry intracellular cytokine staining was used.

RESULTS

We found that the presence of CD8+ dual positive (IFNγ+ and IL-2+) cells is the most accurate functional parameter that can predict fast resolution of CMV reactivation. Next, we show that the presence of CD8+ dual positive (IFNγ+ and IL-2+) and CD8+ IFNγ+ cells provides a protective effect (a hazard risk of 0.28 (confidence interval 0.18 - 0.43) and 0.45 (CI 0.27 - 0.75), respectively) and the presence of corticotherapy increases the risk of reactivation (HR 2.47 (CI 1.82-3.36)). Thus, a patient without corticotherapy and with both of the critical T cell subsets present has a cumulative 19.6 times lower risk of developing CMV reactivation than a patient on corticotherapy and without CD8+ dual positive (IFNγ+ and IL-2+) or CD8+ IFNγ+ cells.

CONCLUSIONS

We have established parameters of CMV specific functional response ex vivo that can be used in assisting clinical management of patients with CMV reactivation. © 2015 International Clinical Cytometry Society.

The immune response to cytomegalovirus in allogeneic hematopoietic stem cell transplant recipients

Approximately, up to 70 % of the human population is infected with cytomegalovirus (CMV) that persists for life in a latent state. In healthy people, CMV reactivation induces the expansion of CMV-specific T cells up to 10 % of the entire T cell repertoire. On the contrary, CMV infection is a major opportunistic viral pathogen that remains a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Due to the delayed CMV-specific immune recovery, the incidence of CMV reactivation during post-transplant period is very high. Several methods are currently available for the monitoring of CMV-specific responses that help in clinical monitoring. In this review, essential aspects in the immune recovery against CMV are discussed to improve the better understanding of the immune system relying on CMV infection and, thereby, helping the avoidance of CMV disease or reactivation following hematopoietic stem cell transplantation with severe consequences for the transplanted patients.

Reactivation of Human Herpes Virus-6 After Pediatric Stem Cell Transplantation: Risk Factors, Onset, Clinical Symptoms and Association With Severity of Acute Graft-Versus-Host Disease

BACKGROUND AND METHODS

To study clinical symptoms, timing and consequences of human herpesvirus-6 (HHV-6) reactivation after pediatric allogeneic stem cell transplantation (SCT), HHV-6 was investigated by plasma polymerase chain reaction in a cohort of 106 pediatric SCT recipients.

RESULTS

HHV-6 viremia was detected post-SCT in 48% of the patients with a median time of onset at 20 days after SCT. In week 3 and 4 post-SCT, HHV-6 is the most common infectious agent detected. In up to 30% of the patients with fever of unknown origin, HHV-6 was the only detected infectious agent to explain fever. Patients transplanted with an unrelated donor or receiving serotherapy were at increased risk of HHV-6 reactivation. The onset of HHV-6 reactivation coincided with the appearance of lymphocytes and monocytes in peripheral blood. Treatment with alemtuzumab (MabCampath) delayed both lymphocyte and monocyte engraftment and, concomitantly, onset of HHV-6 reactivation was delayed in those cases. HHV-6 reactivation was not associated with an increased incidence of acute graft-versus-host disease (GvHD). However, progression to grade II-IV GvHD was in 9 of 10 patients associated with HHV-6 reactivation before GvHD (P = 0.006) and HHV-6 was the only infection with such an association.

CONCLUSIONS

HHV-6 frequently reactivates after pediatric SCT around the time of mononuclear cell engraftment and is associated with an increased severity of GvHD. HHV-6 may explain fever of unknown origin in 30% of the patients early after SCT. Assessment of HHV-6 reactivation in patients early after SCT can be instrumental for clinical decision making.

Mechanism of tumor remission by cytomegalovirus in a murine lymphoma model: evidence for involvement of virally induced cellular interleukin-15

A murine model of B and T cell lymphomas in recipients after hematoablative conditioning for hematopoietic cell transplantation (HCT) has previously revealed a tumor-repressive, metastasis-inhibiting function of murine cytomegalovirus (mCMV). More recently, this prediction from the experimental model was put on trial in several clinical studies that indeed gave evidence for a lower incidence of tumor relapse associated with early reactivation of latent human cytomegalovirus (hCMV) after allogeneic HCT in patients treated against different types of hematopoietic malignancies, including lymphoma and acute as well as chronic leukemias. Due to the limitations inherent to clinical studies, the tumor-repressive role of hCMV remained observational with no approach to clarify mechanisms. Although the tumor-repressive mechanisms of mCMV and hCMV may differ and depend on the type of tumor, experimental approaches in the murine model might give valuable hints for concepts to follow in clinical research. We have previously shown for the liver-adapted A20-derived B cell lymphoma E12E that mCMV does not infect the lymphoma cells for causing cell death by viral cytopathogenicity but triggers tumor-selective apoptosis at a tissue site of tumor metastasis distant from a local site of infection. This finding suggested involvement of a cytokine that triggers apoptosis, directly or indirectly. Here we used a series of differential high-density microarray analyses to identify cellular genes whose expression is specifically upregulated at the site of virus entry only by viruses capable of triggering lymphoma cell apoptosis. This strategy identified interleukin-15 (IL-15) as most promising candidate, eventually confirmed by lymphoma repression with recombinant IL-15.

Cooperation between Epstein-Barr virus immune evasion proteins spreads protection from CD8+ T cell recognition across all three phases of the lytic cycle

CD8+ T cell responses to Epstein-Barr virus (EBV) lytic cycle expressed antigens display a hierarchy of immunodominance, in which responses to epitopes of immediate-early (IE) and some early (E) antigens are more frequently observed than responses to epitopes of late (L) expressed antigens. It has been proposed that this hierarchy, which correlates with the phase-specific efficiency of antigen presentation, may be due to the influence of viral immune-evasion genes. At least three EBV-encoded genes, BNLF2a, BGLF5 and BILF1, have the potential to inhibit processing and presentation of CD8+ T cell epitopes. Here we examined the relative contribution of these genes to modulation of CD8+ T cell recognition of EBV lytic antigens expressed at different phases of the replication cycle in EBV-transformed B-cells (LCLs) which spontaneously reactivate lytic cycle. Selective shRNA-mediated knockdown of BNLF2a expression led to more efficient recognition of immediate-early (IE)- and early (E)-derived epitopes by CD8+ T cells, while knock down of BILF1 increased recognition of epitopes from E and late (L)-expressed antigens. Contrary to what might have been predicted from previous ectopic expression studies in EBV-negative model cell lines, the shRNA-mediated inhibition of BGLF5 expression in LCLs showed only modest, if any, increase in recognition of epitopes expressed in any phase of lytic cycle. These data indicate that whilst BNLF2a interferes with antigen presentation with diminishing efficiency as lytic cycle progresses (IE>E>>L), interference by BILF1 increases with progression through lytic cycle (IE Collapse

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MESH Headings

• Antigen Presentation/immunology
• Blotting, Western
• CD8-Positive T-Lymphocytes/immunology
• Deoxyribonucleases/immunology
• Epstein-Barr Virus Infections/immunology
• Gene Knockdown Techniques
• Herpesvirus 4, Human/immunology
• Humans
• Immune Evasion/immunology
• Real-Time Polymerase Chain Reaction
• Receptors, G-Protein-Coupled/immunology
• Viral Matrix Proteins/immunology
• Viral Proteins/immunology

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Grants

• 15032 Cancer Research UK
• MR/J002046/1 Medical Research Council
• G0901755 Medical Research Council
• C5575/A15032 Cancer Research UK

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Affiliation(s)

Laura L. Quinn School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Jianmin Zuo School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Rachel J. M. Abbott School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Claire Shannon-Lowe School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Rosemary J. Tierney School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Andrew D. Hislop School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom
Martin Rowe School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham, United Kingdom

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A registry of HLA-typed donors for production of virus-specific CD4 and CD8 T lymphocytes for adoptive reconstitution of immune-compromised patients

BACKGROUND

Virus-specific CD4 and CD8 T lymphocytes from HLA-matched donors are effective for treatment and prophylaxis of viral infections in immune-compromised recipients of hematopoietic stem cell transplant recipients. Adoptive immune reconstitution is based on selection of specific T cells or on generation of specific T-cell lines from the graft donor. Unfortunately, the graft donor is not always immune to the relevant pathogen or the graft donor may not be available (registry-derived or cord blood donors).

STUDY DESIGN AND METHODS

Since the possibility of using T cells from a third-party subject is now established, we screened potential donors for T-cell responses against cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus, the viruses most frequently targeted by adoptive immune reconstitution. Specific T-cell responses against viral antigens were analyzed in 111 donors using a miniaturized interferon-γ release assay.

RESULTS

Responders to CMV were 64%, to EBV 40%, and to adenovirus 51%. Simultaneous responders to the three viruses were 49%. CMV-specific CD4 and CD8 T-cell lines could be generated from 11 of 12 donors defined as positive responders according to the T-cell assay.

CONCLUSIONS

These data demonstrate that a large fraction of volunteers can be recruited in a donor registry for selection or expansion of virus specific T cells and that our T-cell assay predicts the donors' ability to give rise to established T-cell lines endowed with proliferative potential and effector function for adoptive immune reconstitution.

Infectious complications of stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is an accepted treatment for a variety of hematologic malignancies. The profound immunosuppression these patients experience adversely affects their risk of infection. This risk is much higher than in the general population and requires aggressive diagnostic and therapeutic interventions. The chapter will outline the major infections after HSCT.

T-cell therapy for cytomegalovirus infection

PURPOSE OF REVIEW

Human cytomegalovirus (CMV) reactivation and disease remains one of the major complications after allogeneic haemopoietic stem cell transplantation. Cell-mediated immunity is essential in counteracting CMV infection as evident by detection of high frequencies of CMV-specific CD8 and CD4 lymphocytes among the healthy CMV-seropositive individuals. Adoptive transfer of CMV-specific T cells to speed up reconstitution of CMV-specific immunity potentially offers clinical protection and reduces drug toxicities as well as outgrowth of drug-resistant strains from prolonged antiviral therapy.

RECENT FINDINGS

Different strategies to generate CMV-specific T cell have been explored. Similarly, vast diversities in term of cell dose and composition of the cellular product have been infused into small cohorts of patients. To date, a number of phase I/II clinical trials have demonstrated the feasibility of adoptive transferred CMV-specific T cells as prophylaxis, pre-emptive or therapeutic measure. In general, all these strategies showed variable degrees of efficacy without obvious adverse event particularly with regard to the induction of graft-versus-host disease.

SUMMARY

In this review, we would like to give a comprehensive synopsis regarding therapeutic application of CMV-specific T cells in fighting CMV infection.

Mast cells expedite control of pulmonary murine cytomegalovirus infection by enhancing the recruitment of protective CD8 T cells to the lungs

The lungs are a noted predilection site of acute, latent, and reactivated cytomegalovirus (CMV) infections. Interstitial pneumonia is the most dreaded manifestation of CMV disease in the immunocompromised host, whereas in the immunocompetent host lung-infiltrating CD8 T cells confine the infection in nodular inflammatory foci and prevent viral pathology. By using murine CMV infection as a model, we provide evidence for a critical role of mast cells (MC) in the recruitment of protective CD8 T cells to the lungs. Systemic infection triggered degranulation selectively in infected MC. The viral activation of MC was associated with a wave of CC chemokine ligand 5 (CCL5) in the serum of C57BL/6 mice that was MC-derived as verified by infection of MC-deficient Kit^W-sh/W-sh “sash” mutants. In these mutants, CD8 T cells were recruited less efficiently to the lungs, correlating with enhanced viral replication and delayed virus clearance. A causative role for MC was verified by MC reconstitution of “sash” mice restoring both, efficient CD8 T-cell recruitment and infection control. These results reveal a novel crosstalk axis between innate and adaptive immune defense against CMV, and identify MC as a hitherto unconsidered player in the immune surveillance at a relevant site of CMV disease.

Being strategically located beneath endothelial and epithelial surfaces, mast cells (MC) serve as sentinels for invading pathogens at host-environment boundaries as part of the innate defense against infection. Host genetic resistance against cytomegaloviruses (CMV) is largely determined by the innate immune response, but an implication of MC in the adaptive immune defense against CMV has not been considered so far and is almost impossible to address in human infection. Using murine CMV as a model that in the past has already pioneered the discovery of fundamental principles in CMV-host interactions, our data reveal MC as central part of a novel crosstalk-axis between the innate and adaptive immune response to CMV. We found that upon host infection MC become rapidly activated and promote the recruitment of protective CD8 T cells to the lungs, a noted critical site of CMV pathogenesis in humans as well as in the mouse model. Enhanced tissue infiltration of CD8 T cells results in a reduced peak viral load and a faster clearance of productive infection. Realizing the importance of MC in the control of pulmonary CMV infection may help to develop new strategies for preventing CMV pneumonia by MC supplementation in recipients of hematopoietic cell transplantation.

CMV serostatus still has an important prognostic impact in de novo acute leukemia patients after allogeneic stem cell transplantation: a report from the Acute Leukemia Working Party of EBMT

We analyzed the prognostic impact of donor and recipient cytomegalovirus (CMV) serostatus in 16,628 de novo acute leukemia patients after allogeneic stem cell transplantation (allo-SCT). Compared with CMV-seronegative recipients who underwent allograft from a CMV-seronegative donor, cases of CMV seropositivity of the donor and/or the recipient showed a significantly decreased 2-year leukemia-free survival (44% vs 49%, P < .001) and overall survival (50% vs 56%, P < .001), and increased nonrelapse mortality (23% vs 20%, P < .001). Both groups showed a comparable relapse incidence and 2-year probability of graft-versus-host disease. The negative prognostic effects of CMV seropositivity of the donor and/or the recipient (vs CMV seronegativity of both) were significantly stronger for acute lymphoblastic leukemia (ALL) than for acute myeloid leukemia (AML), resulting in a markedly reduced 2-year overall survival (46% vs 55% for ALL compared with 52% vs 56% for AML). The important prognostic impact of donor/recipient CMV serostatus remained in a multivariate Cox regression analysis including the other prognostic variables. We conclude that donor and/or recipient CMV seropositivity is still associated with an adverse prognosis in de novo acute leukemia patients after allo-SCT despite the implementation of sophisticated strategies for prophylaxis, monitoring, and (preemptive) treatment of CMV.

CMV-, EBV- and ADV-specific T cell immunity: screening and monitoring of potential third-party donors to improve post-transplantation outcome

Adoptive immunotherapy with virus-specific T lymphocytes can efficiently reconstitute antiviral immunity against cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus (ADV) without causing acute toxicity or increasing the risk of graft-versus-host disease. To gain insight into antiviral T cell repertoires and to identify the most efficient antigens for immunotherapy, the frequencies of CMV-, EBV- and ADV-specific T cells in 204 HLA-typed healthy donors were assessed using viral peptides and peptide pools. Confirmatory testing for CMV serology by Western blot technique revealed 19 of 143 (13%) false-positive results. We observed highly significant individual and overall differences in T cell frequencies against CMV, EBV, and ADV antigens, whereas antigen-specific T cells were detected in 100% of CMV- seropositive donors, 73% of EBV- seropositive donors, and 73% of ADV-seropositive donors. At least 124 (61%) potential T cell donors were identified for each virus. Among the tested antigens, frequencies for CMVpp65 and EBVBZLF1 peptide pools were highest. Short-term in vitro peptide stimulation revealed that a donor response to a certain ADV- and EBV-derived peptide may not be determined without prior stimulation. A modified granzyme B ELISpot was used to detect T cell specificity and alloreactivity. Treatment with allogeneic virus-specific cytotoxic T lymphocytes from seropositive third-party donors may be a feasible therapeutic option for infections following cord-blood stem cell transplantation or hematopoietic stem cell transplantation from virus-seronegative donors.