Adoptive transfer of pp65-specific T cells for the treatment of chemorefractory cytomegalovirus disease or reactivation after haploidentical and matched unrelated stem cell transplantation. Blood. 2010;116:4360-4367. [PMID: 20625005 DOI: 10.1182/blood-2010-01-262089]

Haploidentical transplantation for hematologic malignancies: where do we stand?

The fundamental obstacle to the successful application of partially HLA-mismatched related donor, or HLA-haploidentical stem cell transplantation, is the strength of the host and donor T-cell response to allogeneic HLA molecules, which results in increased incidences of graft failure, GVHD, and nonrelapse mortality. The holy grail of haplo-SCT is to mitigate host-versus-graft and graft-versus-host responses while preserving immune responses to infection and the patient's malignancy. Two strategies have been taken to achieve this goal. The first strategy is to supplement a T cell–depleted graft with pathogen-specific T cells or populations of T cells in which alloreactivity can be controlled. The second strategy is to eliminate alloreactive T cells selectively from a T cell–replete graft. Substantial progress has been made with both approaches so that the safety of haplo-SCT now approaches that of SCT using grafts of umbilical cord blood or from HLA-matched donors. In light of the rapid and near universal availability of HLA-haploidentical related donors, it should now be possible to identify and mobilize a donor for every patient referred for allogeneic SCT. Prospective comparisons between haploidentical SCT and unrelated donor SCT should be performed to identify the most efficacious approach to alternative donor transplantation.

Adoptive transfer of epstein-barr virus (EBV) nuclear antigen 1-specific t cells as treatment for EBV reactivation and lymphoproliferative disorders after allogeneic stem-cell transplantation

PURPOSE

Reactivation of Epstein-Barr virus (EBV) after allogeneic stem-cell transplantation (SCT) can lead to severe life-threatening infections and trigger post-transplantation lymphoproliferative disease (PTLD). Since EBV-specific T cells could prevent PTLD, cellular immunotherapy has been a promising treatment option. However, generation of antigen-specific T-cell populations has been difficult within a short time frame.

PATIENTS AND METHODS

To improve availability in urgent clinical conditions, we developed a rapid protocol for isolation of polyclonal EBV nuclear antigen 1 (EBNA-1) -specific T cells by using an interferon gamma (IFN-γ) capture technique.

RESULTS

We report on the use of adoptive transfer of EBNA-1-specific T cells in 10 pediatric and adult patients with EBV viremia and/or PTLD after SCT. No acute toxicity or graft-versus-host disease (GVHD) of more than grade 2 occurred as a result of adoptive T-cell transfer. In vivo expansion of transferred EBNA-1-specific T cells was observed in eight of 10 patients after a median of 16 days following adoptive transfer that was associated with clinical and virologic response in seven of them (70%). None of the responders had EBV-associated mortality. Within clinical responders, three patients were disease free by the day of last follow-up (2 to 36 months), three patients died of other infectious complications, and one patient died as a result of relapse of malignancy. EBV-related mortality was observed in two of 10 patients, and another patient had ongoing viremia without clinical symptoms at last follow-up.

CONCLUSION

Adoptive ex vivo transfer of EBNA-1-specific T cells is a feasible and well-tolerated therapeutic option, representing a fast and efficient procedure to achieve reconstitution of antiviral T-cell immunity after SCT.

Immune reconstitution and strategies for rebuilding the immune system after haploidentical stem cell transplantation

Haploidentical hematopoietic stem cell transplantation is a curative alternative option for patients without an otherwise suitable stem cell donor. In order to prevent graft-versus-host disease (GvHD), different in vitro and in vivo T cell-depletion strategies have been developed. A delayed immune reconstitution is common to all these strategies, and an impaired immune function after haploidentical transplantation with subsequent infections is a major cause of deaths in these patients. In addition to in vitro and in vivo T cell-depletion methods, posttransplant strategies to rapidly rebuild the immune system have been introduced in order to improve the outcome. Advances in in vitro and in vivo T cell-depletion methods, and adoptive transfer of immune cells of the innate and specific immune system, will contribute to reduce the risk of GvHD, lethal infections, and the risk of relapse of the underlying malignant disease.

Cytotoxic T lymphocytes for the treatment of viral infections and posttransplant lymphoproliferative disorders in transplant recipients

PURPOSE OF REVIEW

The continuous and successful expansion of organ transplants is unfortunately associated with increased incidence of severe opportunistic viral infections and Epstein-Barr virus (EBV)-related lymphomas secondary to immunosuppression. Here, we review the strengths and limitations of T-cell-based strategies used to treat viral infections in immunocompromised individuals.

RECENT FINDINGS

While current antiviral drugs are often suboptimal because of associated toxicities, a promising approach in the management of infections with viruses like cytomegalovirus (CMV), adenovirus (AdV) and EBV is the adoptive transfer of T cells targeting these viruses that can be directly isolated from the peripheral blood of the donor or expanded ex vivo prior to infusions in patients.

SUMMARY

T-cell-based immunotherapies are now being included in the clinical practice of transplant recipients to prevent and treat infections and complications associated with CMV, AdV and EBV. Improvement of current limitations will enable the extension of these approaches to all patients at risk and to other clinically relevant viruses and pathogens that are emerging as significant complications for immunocompromised patients.

Immune control in the absence of immunodominant epitopes: implications for immunotherapy of cytomegalovirus infection with antiviral CD8 T cells

Adoptive transfer of virus-specific donor-derived CD8 T cells is a therapeutic option to prevent cytomegalovirus (CMV) disease in recipients of hematopoietic cell transplantation. Due to their high coding capacity, human as well as animal CMVs have the potential to encode numerous CD8 T cell epitopes. Although the CD8 T cell response to CMVs is indeed broadly specific in that it involves epitopes derived from almost every open reading frame when tested for cohorts of immune CMV carriers representing the polymorphic MHC/HLA distribution in the population, the response in any one individual is directed against relatively few epitopes selected by the private combination of MHC/HLA alleles. Of this individually selected set of epitopes, few epitopes are 'immunodominant' in terms of magnitude of the response directed against them, while others are 'subdominant' according to this definition. In the assumption that 'immunodominance' indicates 'relevance' in antiviral control, research interest was focused on the immunodominant epitopes (IDEs) and their potential use in immunotherapy and in vaccines. The murine model has provided 'proof of concept' for the efficacy of CD8 T cell therapy of CMV infection. By experimental modulation of the CD8 T cell 'immunome' of murine CMV constructing an IDE deletion mutant, we have used this established cytoimmunotherapy model (a) for evaluating the actual contribution of IDEs to the control of infection and (b) for answering the question whether antigenicity-determining codon polymorphisms in IDE-encoding genes of CMV strains impact on the efficacy of CD8 T cell immunotherapy in case the donor and the recipient harbor different CMV strains.

Parameters determining the efficacy of adoptive CD8 T-cell therapy of cytomegalovirus infection

Reactivation of latent cytomegalovirus (CMV) in the transient state of immunodeficiency after hematopoietic cell transplantation (HCT) is the most frequent and severe viral complication endangering leukemia therapy success. By infecting the bone marrow (BM) stroma of the transplantation recipient, CMV can directly interfere with BM repopulation by the transplanted donor-derived hematopoietic cells and thus delay immune reconstitution of the recipient. Cytopathogenic virus spread in tissues can result in CMV disease with multiple organ manifestations of which interstitial pneumonia is the most feared. There exists a 'window of risk' between hematoablative treatment and reconstitution of antiviral immunity after HCT, whereby timely reconstitution of antiviral CD8 T cells is a recognized positive prognostic parameter for the control of reactivated CMV infection and prevention of CMV disease. Supplementation of endogenous reconstitution by adoptive cell transfer of 'ready-to-go' effector and/or memory virus epitope-specific CD8 T cells is a therapeutic option to bridge the 'window of risk.' Preclinical research in murine models of CMV disease has been pivotal by providing 'proof of concept' for a benefit from CD8 T-cell therapy of HCT-associated CMV disease (reviewed in Holtappels et al. Med Microbiol Immunol 197:125-134, 2008). Here, we give an update of our previous review with focus on parameters that determine the efficacy of adoptive immunotherapy of CMV infection by antiviral CD8 T cells in the murine model.

Antigen presentation under the influence of 'immune evasion' proteins and its modulation by interferon-gamma: implications for immunotherapy of cytomegalovirus infection with antiviral CD8 T cells

Cytomegalovirus (CMV) disease with multiple organ manifestations is the most feared viral complication limiting the success of hematopoietic cell transplantation as a therapy of hematopoietic malignancies. A timely endogenous reconstitution of CD8 T cells controls CMV infection, and adoptive transfer of antiviral CD8 T cells is a therapeutic option to prevent CMV disease by bridging the gap between an early CMV reactivation and delayed endogenous reconstitution of protective immunity. Preclinical research in murine models has provided 'proof of concept' for CD8 T-cell therapy of CMV disease. Protection by CD8 T cells appears to be in conflict with the finding that CMVs encode proteins that inhibit antigen presentation to CD8 T cells by interfering with the constitutive trafficking of peptide-loaded MHC class I molecules (pMHC-I complexes) to the cell surface. Here, we have systematically explored antigen presentation in the presence of the three currently noted immune evasion proteins of murine CMV in all possible combinations and its modulation by pre-treatment of cells with interferon-gamma (IFN-γ). The data reveal improvement in antigen processing by pre-treatment with IFN-γ can almost overrule the inhibitory function of immune evasion molecules in terms of pMHC-I expression levels capable of triggering most of the specific CD8 T cells, though the intensity of stimulation did not retrieve their full functional capacity. Notably, an in vivo conditioning of host tissue cells with IFN-γ in adoptive cell transfer recipients constitutively overexpressing IFN-γ (B6-SAP-IFN-γ mice) enhanced the antiviral efficiency of CD8 T cells in this transgenic cytoimmunotherapy model.

T-cell therapy in the treatment of post-transplant lymphoproliferative disease

Post-transplant lymphoproliferative diseases (PTLD) associated with Epstein-Barr virus (EBV) infection often develop after organ and haematopoietic stem-cell transplantation. These lymphoproliferative diseases are tumours that usually express all latent EBV viral proteins, and are therefore amenable to T-cell-based immune therapies, such as donor lymphocyte infusions and the adoptive transfer of EBV-specific cytotoxic T lymphocytes. In this Review, we describe current approaches of T-cell-based therapies to treat PTLD, and describe strategies that improve the feasibility of such treatment.

Molecular diagnosis and management of viral infections in hematopoietic stem cell transplant recipients

Viral infections after allogeneic hematopoietic stem cell transplantation (HSCT) are important complications associated with high morbidity and mortality. In this setting, reactivations of persisting latent viral pathogens from donor and/or recipient cells play a central role whereas the sterile environment of transplant units renders new infections less likely. The viruses currently regarded as most relevant in the HSCT setting include particularly the herpes virus family--specifically cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6 (HHV-6)--as well as human adenoviruses (AdVs) and the polyoma virus BK (BKV). Timely detection and monitoring of virus copy numbers are prerequisites for successful preemptive treatment approaches. Pre- and post-transplant surveillance by sensitive and quantitative molecular methods has therefore become an essential part of the diagnostic routine. In this review, we discuss diagnostic aspects and the clinical management of the most important viral infections in HSCT recipients, with a focus on pediatric patients.

Rapidly generated multivirus-specific cytotoxic T lymphocytes for the prophylaxis and treatment of viral infections

Severe and fatal viral infections remain common after hematopoietic stem cell transplantation. Adoptive transfer of cytotoxic T lymphocytes (CTLs) specific for Epstein–Barr virus (EBV), cytomegalovirus (CMV), and adenoviral antigens can treat infections that are impervious to conventional therapies, but broader implementation and extension to additional viruses is limited by competition between virus-derived antigens and time-consuming and laborious manufacturing procedures. We now describe a system that rapidly generates a single preparation of polyclonal (CD4⁺ and CD8⁺) CTLs that is consistently specific for 15 immunodominant and subdominant antigens derived from 7 viruses (EBV, CMV, Adenovirus (Adv), BK, human herpes virus (HHV)-6, respiratory syncytial virus (RSV), and Influenza) that commonly cause post-transplant morbidity and mortality. CTLs can be rapidly produced (10 days) by a single stimulation of donor peripheral blood mononuclear cells (PBMCs) with a peptide mixture spanning the target antigens in the presence of the potent prosurvival cytokines interleukin-4 (IL4) and IL7. This approach reduces the impact of antigenic competition with a consequent increase in the antigenic repertoire and frequency of virus-specific T cells. Our approach can be readily introduced into clinical practice and should be a cost-effective alternative to common antiviral prophylactic agents for allogeneic hematopoietic stem cell transplant (HSCT) recipients.

Therapeutic strategies for the prevention and treatment of cytomegalovirus infection

INTRODUCTION

CMV remains a significant cause of morbidity and mortality in immunosuppressed patients, particularly following allogeneic haematopoietic transplantation. This reflects the inability of depressed host immunity to contain viral replication, principally through the loss of T-cell function. There is a clear rationale for the restoration of CMV-specific immunity using adoptive T-cell immunotherapy.

AREAS COVERED

This review analyses current treatment strategies for prophylaxis and preemptive treatment of CMV with a particular focus on patients following allogeneic haematopoietic transplantation. The main emphasis of this review is the role of adoptive T-cell therapy, particularly some of the newer direct selection technologies that allow the rapid generation of a GMP-compliant cellular product. Relevant studies were selected from PubMed. Search terms: allogeneic transplant, cytomegalovirus, multidrug-resistant virus, adoptive T-cell therapy.

EXPERT OPINION

A number of early studies showed that T-cell therapies can be delivered safely and are efficacious. However, they relied on culture techniques that make wider application difficult. Newer direct selection techniques have allowed production of cellular products more rapidly, cheaply, and to GMP standards. Clinical trials will help define the role of these cellular products, which have the potential to alter our entire approach to the treatment of CMV infection.

Complications of immunosuppressive/immunomodulatory therapy in neurological diseases

OPINION STATEMENT

The first critical step in the appropriate treatment of neurological infectious disease accompanying immunosuppressive states or immunomodulatory medication is to properly identify the offending organism. Broadly immunosuppressive conditions will predispose to both common and uncommon infectious diseases. There are substantial differences between neurological infectious disorders complicating disturbances of the innate immunity (neutrophils, monocytes and macrophages) and those due to abnormal adaptive immunity (humoral and cellular immunity). Similarly, there are differences in the types of infections with impaired humoral immunity compared to disturbed cellular immunity and between T- and B-cell disorders. HIV/AIDS has been a model of acquired immunosuppression and the nature of opportunistic infections with which it has been associated has been well characterized and generally correlates well with the degree of CD4 lymphopenia. Increasingly, immunotherapies target specific components of the immune system, such as an adhesion molecule or its ligand or surface receptors on a special class of cells. These targeted perturbations of the immune system increase the risk of particular infectious diseases. For instance, natalizumab, an α4β1 integrin inhibitor that is highly effective in multiple sclerosis, increases the risk of progressive multifocal leukoencephalopathy for reasons that still remain unclear. It is likely that other therapies that result in a disruption of a specific component of the immune system will be associated with other unique opportunistic infections. The risk of multiple simultaneous neurological infections in the immunosuppressed host must always be considered, particularly with a failure to respond to a therapeutic regimen. With respect to appropriate and effective therapy, diagnostic accuracy assumes primacy, but occasionally broad spectrum therapy is necessitated. For a number of opportunistic infectious disorders, particularly some viral and fungal diseases, antimicrobial therapy remains inadequate.

Monitoring and managing viral infections in pediatric renal transplant recipients

Viral infections remain a significant cause of morbidity and mortality following renal transplantation. The pediatric cohort is at high risk of developing virus-related complications due to immunological naiveté and the increased alloreactivity risk that requires maintaining a heavily immunosuppressive environment. Although cytomegalovirus is the most common opportunistic pathogen seen in transplant recipients, numerous other viruses may affect clinical outcome. Recent technological advances and novel antiviral therapy have allowed implementation of viral and immunological monitoring protocols and adoption of prophylactic or preemptive treatment approaches in high-risk groups. These strategies have led to improved viral infection management in the immunocompromised host, with significant impact on outcome. We review the major viral infections seen following kidney transplantation and discuss strategies for preventing and managing these pathogens.

Generation and administration of HA-1-specific T-cell lines for the treatment of patients with relapsed leukemia after allogeneic stem cell transplantation: a pilot study

Since HA-1-specific T cells have been shown to make a significant contribution to the clinical responses in patients with relapsed leukemia, we investigated the feasibility of adoptive transfer of in vitro induced HA-1-specific CD8 positive T cells to patients with relapsed leukemia after allogeneic stem cell transplantation. The in vitro generation of clinical grade HA-1-specific T-cell lines from HA-1 negative donors was seen to be feasible and 3 patients were treated with HA-1-specific T-cell lines. No toxicity after infusion was observed. Although in one patient, during a period of stable disease, HA-1-specific T cells could be detected in the peripheral blood and bone marrow, these patients had no clear clinical response.

New strategies for haploidentical transplantation

Haploidentical transplantation in children opens the possibility to offer this treatment to every child with an otherwise incurable disease, such as some hematological or oncological malignancies, inborn or acquired bone marrow-failure syndromes, hemoglobinopathies, immunodeficiencies, or other genetic diseases. Although initial attempts at haploidentical transplantation were associated with a high transplant-related mortality, recent insights into the biology of haploidentical transplantation, the availability of effective in vivo large-scale graft-manipulation technology, and improved supportive care strategies have led to and are still leading to significantly better outcomes of haploidentical transplantation as compared with previous decades. In addition, expensive and time-consuming searches for matched unrelated donors (MUDs) as well as the expensive establishment and maintenance of cord blood banks are not necessary. Moreover, the worldwide donor registries comprise mainly donors of Caucasian origin and patients of non-Caucasian origin have a lower chance of finding a MUD. Therefore, haploidentical transplantation allows the treatment of children independently of their ethnic background in a timely fashion according to the status of their underlying disease.

Human cytomegalovirus-specific T-cell immune reconstitution in preemptively treated heart transplant recipients identifies subjects at critical risk for infection

Human cytomegalovirus (CMV) infection represents a major threat for heart transplant recipients (HTXs). CMV-specific T cells effectively control virus infection, and thus, assessment of antiviral immune recovery may have clinical utility in identifying HTXs at risk of infection. In this study, 10 CMV-seropositive (R(+)) pretransplant patients and 48 preemptively treated R(+) HTXs were examined before and after 100 days posttransplant. Preemptive treatment is supposed to favor the immune recovery. CMV DNAemia and gamma interferon enzyme-linked immunosorbent spot (ELISPOT) assay were employed to assess the viremia and immune reconstitution. HTXs could be categorized into three groups characterized by high (>100), medium (50 to 100), and low (<50) spot levels. Early-identified high responders efficiently controlled the infection and also maintained high immunity levels after 100 days after transplant. No episodes of grade ≥2R rejection occurred in the high responders. Midresponders were identified as a group with heterogeneous trends of immune reconstitution. Low responders were 41% and 21% of HTXs before and after 100 days posttransplant, respectively. Low responders were associated with a higher incidence of infection. The effect of viremia on immune recovery was investigated: a statistically significant inverse correlation between magnitude of viremia and immune recovery emerged; in particular, each 10-fold increase in viremia (>4 log(10) DNAemia/ml) was associated with a 36% decrease of the ELISPOT assay spot levels. All episodes of high viremia (>4 log(10) DNAemia/ml) occurred from 1 to 60 days after transplant. Thus, the concomitant evaluation of viremia and CMV immune reconstitution has clinical utility in identifying HTXs at risk of infection and may represent a helpful guide in making therapeutic choices.

Clinical evaluation of safety and immunogenicity of PADRE-cytomegalovirus (CMV) and tetanus-CMV fusion peptide vaccines with or without PF03512676 adjuvant

BACKGROUND

It has been reported that cytomegalovirus (CMV) pp65-specific T cells can protect hematopoietic cell transplant (HCT) recipients from CMV complications. Two candidate CMV peptide vaccines composed of the HLA A*0201 pp65(495-503) cytotoxic CD8(+) T-cell epitope fused to 2 different universal T-helper epitopes (either the synthetic Pan DR epitope [PADRE] or a natural Tetanus sequence) were clinically evaluated for safety and ability to elicit pp65 T cells in HLA A*0201 healthy volunteers.

METHODS

Escalating doses (0.5, 2.5, 10 mg) of PADRE or Tetanus pp65(495-503) vaccines with (30 adults) or without (28 adults) PF03512676 adjuvant were administered by subcutaneous injection every 3 weeks for a total of 4 injections.

RESULTS

No serious adverse events were reported, although vaccines used in combination with PF03512676 had enhanced reactogenicity. Ex vivo responses were detected by flow cytometry exclusively in volunteers who received the vaccine coadministered with PF03512676. In addition, using a sensitive in vitro stimulation system, vaccine-elicited pp65(495-503) T cells were expanded in 30% of volunteers injected solely with the CMV peptides and in all tested subjects receiving the vaccines coinjected with PF03512676.

CONCLUSIONS

Acceptable safety profiles and vaccine-driven expansion of pp65(495-503) T cells in healthy adults support further evaluation of CMV peptide vaccines combined with PF03512676 in the HCT setting.

CLINICAL TRIALS REGISTRATION

NCT00722839.

The immune response to human CMV

This review will summarize and interpret recent literature regarding the human CMV immune response, which is among the strongest measured and is the focus of attention for numerous research groups. CMV is a highly prevalent, globally occurring infection that rarely elicits disease in healthy immunocompetent hosts. The human immune system is unable to clear CMV infection and latency, but mounts a spirited immune-defense targeting multiple immune-evasion genes encoded by this dsDNA β-herpes virus. Additionally, the magnitude of cellular immune response devoted to CMV may cause premature immune senescence, and the high frequencies of cytolytic T cells may aggravate vascular pathologies. However, uncontrolled CMV viremia and life-threatening symptoms, which occur readily after immunosuppression and in the immature host, clearly indicate the essential role of immunity in maintaining asymptomatic co-existence with CMV. Approaches for harnessing the host immune response to CMV are needed to reduce the burden of CMV complications in immunocompromised individuals.

Critical role of perforin-dependent CD8+ T cell immunity for rapid protective vaccination in a murine model for human smallpox

Vaccination is highly effective in preventing various infectious diseases, whereas the constant threat of new emerging pathogens necessitates the development of innovative vaccination principles that also confer rapid protection in a case of emergency. Although increasing evidence points to T cell immunity playing a critical role in vaccination against viral diseases, vaccine efficacy is mostly associated with the induction of antibody responses. Here we analyze the immunological mechanism(s) of rapidly protective vaccinia virus immunization using mousepox as surrogate model for human smallpox. We found that fast protection against lethal systemic poxvirus disease solely depended on CD4 and CD8 T cell responses induced by vaccination with highly attenuated modified vaccinia virus Ankara (MVA) or conventional vaccinia virus. Of note, CD4 T cells were critically required to allow for MVA induced CD8 T cell expansion and perforin-mediated cytotoxicity was a key mechanism of MVA induced protection. In contrast, selected components of the innate immune system and B cell-mediated responses were fully dispensable for prevention of fatal disease by immunization given two days before challenge. In conclusion, our data clearly demonstrate that perforin-dependent CD8 T cell immunity plays a key role in MVA conferred short term protection against lethal mousepox. Rapid induction of T cell immunity might serve as a new paradigm for treatments that need to fit into a scenario of protective emergency vaccination.

Prophylactic use of vaccinia virus allowed eradication of human smallpox, one of the greatest successes in medicine. However there are concerns that variola virus, the infectious agent of smallpox, may be used as bioterroristic weapon and zoonotic monkeypox or cowpox remain threatening infections in humans. Thus, new developments of safe and rapidly protecting orthopoxvirus-specific vaccines have been initiated. The candidate vaccine modified vaccinia virus Ankara (MVA) was recently shown to protect against lethal systemic poxvirus disease even when applied shortly before or after infection of mice with ectromelia virus, the probably best animal model for human smallpox. Surprisingly, little is known about the protective mechanism of early immune responses elicited against orthopoxvirus infections. Here, we used the mousepox model to analyze the immunological basis of rapidly protective MVA vaccination. In contrast to common understanding of orthopoxvirus vaccine efficacy relying mainly on antibody mediated immunity, we observed unimpaired protection also in absence of B cells. Surprisingly, rapid protection by vaccination with MVA or conventional vaccinia virus was solely dependent on T cells, irrespective of the route of injection. Thus, our study suggests a key role for T cell immunity in rapidly protective immunization against orthopoxviruses and potentially other infectious agents.

Natural and adoptive T-cell immunity against herpes family viruses after allogeneic hematopoietic stem cell transplantation

Reactivated infections with herpes family-related cytomegalovirus, Epstein-Barr virus and varicella zoster virus are serious and sometimes life-threatening complications for patients undergoing allogeneic hematopoietic stem cell transplantation. The pathogenesis of these infections critically involves the slow and inefficient recovery of antiviral T-cell immunity after transplantation. Although efficient drugs to decrease viral load during this vulnerable period have been developed, long-term control of herpes viruses and protection from associated diseases require the sufficient reconstitution of virus-specific memory T cells. To heal the deficiency by immunotherapeutic means, numerous research groups have developed antiviral vaccines and strategies based on the adoptive transfer of virus-specific T cells. This article summarizes the substantial progress made in this field during the past two decades and gives future perspectives about challenges that need to be addressed before antigen-specific immunotherapy against herpes family viruses can be implemented in general clinical practice.

Targeting cytomegalovirus-infected cells using T cells armed with anti-CD3 × anti-CMV bispecific antibody

Human cytomegalovirus (CMV) reactivation and infection can lead to poor outcomes after allogeneic stem cell transplantation. We hypothesized that anti-CD3 activated T cells (ATCs) armed with chemically heteroconjugated anti-CD3 × polyclonal anti-CMV bispecific antibody (CMVBi) will target and eliminate CMV-infected cells. Arming doses of CMVBi as low as 0.01 ng/10(6) ATCs was able to mediate specific cytotoxicity (SC) directed at CMV-infected target cells significant above unarmed ATCs at mutiplicities of infection (MOI) between 0.01 and 1. At effector-to-target ratios (E:T) of 25:1, 12.5:1, 6.25:1, and 3.125:1, armed ATCs significantly enhanced killing of CMV-infected targets compared with unarmed ATCs. At an MOI of 1.0, the mean % SC directed at CMV-infected targets cells for CMVBi-armed ATCs at E:T of 3.12, 6.25, and 12.5 were 79%, 81%, and 82%, respectively; whereas the mean % SC for unarmed ATCs at the same E:T were all <20%. ATCs, Cytogam(®), or CMVBi alone did not lyse uninfected or CMV-infected targets. Co-cultures of CMVBi-armed ATCs with CMV-infected targets induced cytokine and chemokine release from armed ATCs. This nonmajor histocompatibility complex restricted strategy for targeting CMV could be used to prevent or treat CMV infections after allogeneic stem cell transplantation or organ transplantation.

Complications, Diagnosis, Management, and Prevention of CMV Infections: Current and Future

Although major progress has been made in the prevention of CMV disease after hematopoietic cell transplantation (HCT), specific problems remain and available antiviral agents are associated with major toxicities. This article reviews current aspects of CMV diagnosis, prevention, and treatment in HCT recipients and defines areas of unmet medical need.

Induction of antiviral cytotoxic T cells by plasmacytoid dendritic cells for adoptive immunotherapy of posttransplant diseases

Virus-associated hematologic malignancies (EBV lymphoproliferative disease) and opportunistic infections (CMV) represent a major cause of hematopoietic stem cell and solid organ transplantation failure. Adoptive transfer of antigen-specific T lymphocytes appears to be a major and successful immunotherapeutic strategy, but improvements are needed to reliably produce high numbers of virus-specific T cells with appropriate requirements for adoptive immunotherapy that would allow extensive clinical use. Since plasmacytoid dendritic cells (pDCs) are crucial in launching antiviral responses, we investigated their capacity to elicit functional antiviral T-cell responses for adoptive cellular immunotherapy using a unique pDC line and antigens derived from Influenza, CMV and EBV viruses. Stimulation of peripheral blood mononuclear cells from HLA-A*0201(+) donors by HLA-A0201 matched pDCs pulsed with viral-derived peptides triggered high levels of multi-specific and functional cytotoxic T-cell responses (up to 99% tetramer(+) CD8 T cells) in vitro. Furthermore, the central/effector memory cytotoxic T cells elicited by the pDCs strongly display antiviral activity upon adoptive transfer into a humanized mouse model that mimics a virus-induced malignancy. We provide a simple and potent method to generate virus-specific CTL with the required properties for adoptive cellular immunotherapy of post-transplant diseases.

Haploidentical hematopoietic transplantation: current status and future perspectives

For patients with hematologic malignancies at high risk of relapse who do not have matched donors, a suitable alternative stem cell source is the HLA-haploidentical 2 or 3-loci mismatched family donor who is readily available for nearly all patients. Transplantation across the major HLA barrier is associated with strong T-cell alloreactions, which were originally manifested as a high incidence of severe GVHD and graft rejection. The present review shows how these obstacles to successful transplantation were overcome in the last 15 years, making full haplotype-mismatched transplantation a clinical reality that provides similar outcomes to transplantation from matched unrelated donors. The review also discusses the advantages and drawbacks of current options for full haplotype-mismatched transplantation and highlights innovative approaches for re-building immunity after transplantation and improving survival.

Biomarkers in T cell therapy clinical trials

T cell therapy represents an emerging and promising modality for the treatment of both infectious disease and cancer. Data from recent clinical trials have highlighted the potential for this therapeutic modality to effect potent anti-tumor activity. Biomarkers, operationally defined as biological parameters measured from patients that provide information about treatment impact, play a central role in the development of novel therapeutic agents. In the absence of information about primary clinical endpoints, biomarkers can provide critical insights that allow investigators to guide the clinical development of the candidate product. In the context of cell therapy trials, the definition of biomarkers can be extended to include a description of parameters of the cell product that are important for product bioactivity.

This review will focus on biomarker studies as they relate to T cell therapy trials, and more specifically: i. An overview and description of categories and classes of biomarkers that are specifically relevant to T cell therapy trials, and ii. Insights into future directions and challenges for the appropriate development of biomarkers to evaluate both product bioactivity and treatment efficacy of T cell therapy trials.

Engineering T cells specific for a dominant severe acute respiratory syndrome coronavirus CD8 T cell epitope

Severe acute respiratory syndrome (SARS) is a highly contagious and life threatening disease, with a fatality rate of almost 10%. The etiologic agent is a novel coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV), with animal reservoirs found in bats and other wild animals and thus the possibility of reemergence. In this study, we first investigated at 6 years postinfection whether SARS-specific memory T cells persist in SARS-recovered individuals, demonstrating that these subjects still possess polyfunctional SARS-specific memory CD4+ and CD8+ T cells. A dominant memory CD8+ T cell response against SARS-CoV nucleocaspid protein (NP; amino acids 216 to 225) was then defined in SARS-recovered individuals carrying HLA-B*40:01, a HLA-B molecule present in approximately one-quarter of subjects of Asian ethnicities. To reconstitute such a CD8+ T cell response, we isolated the alpha and beta T cell receptors of the HLA-B*40:01-restricted SARS-specific CD8+ T cells. Using T cell receptor gene transfer, we generated SARS-specific redirected T cells from the lymphocytes of normal individuals. These engineered CD8+ T cells displayed avidity and functionality similar to that of natural SARS-specific memory CD8+ T cells. They were able to degranulate and produce gamma interferon, tumor necrosis factor alpha, and macrophage inflammatory proteins 1α and 1β after antigenic stimulation. Since there is no effective treatment against SARS, these transduced T cells specific for an immunodominant SARS epitope may provide a new avenue for treatment during a SARS outbreak.

Generation of a multipathogen-specific T-cell product for adoptive immunotherapy based on activation-dependent expression of CD154

Viral and fungal infections remain a leading cause of mortality in patients after hematopoietic stem cell transplantation (HSCT). Adoptive transfer of multipathogen-specific T cells is promising in restoring immunity and thereby preventing and treating infections, but approaches are currently limited because of time-consuming and laborious procedures. Therefore, we investigated a new strategy to simultaneously select T cells specific for viral and fungal pathogens based on activation-dependent expression of CD154. Single- and multipathogen-specific T-cell lines with high specificity for adenovirus (AdV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), Candida albicans, and/or Aspergillus fumigatus could be readily generated within 14 days irrespective of the precursor frequency. The T-cell lines responded reproducibly to endogenously processed antigen and specifically proliferated upon antigenic stimulation. Although isolation based on CD154 favors enrichment of CD4+ T cells, AdV-, EBV- and CMV-specific CD8+ T cells could be expanded and demonstrated lysis of target cells. Conversely, T cell–mediated alloreactivity was almost abrogated compared with the starting fraction. This selection and/or expansion strategy may form the basis for future adoptive immunotherapy trials in patients at risk for multiple infections and may be translated to other antigens.

Adoptive Immunotherapy after Allogeneic Hematopoietic Progenitor Cell Transplantation: New Perspectives for Transfusion Medicine

SUMMARY: Allogeneic hematopoietic progenitor cell transplantation (HPCT) is a crucial therapeutic option in hematological malignancies, and the graft-versus-leukemia (GvL) effect builds the cornerstone of a long-lasting remission. Cyto-toxic T cells are known to be the primary effector cells in GvL. They recognize minor histocompatibility antigens (mHags) and tumor/leukemia-associated antigens. In case of disease relapse after HPCT, donor lymphocyte infusion (DLI) is an important treatment option for re-induction of remission. However, both treatments, HPCT and DLI carry the risk of morbidity and mortality due to graft-versus-host disease (GvHD) and severe infections. Therefore, the development of targeted adoptive immunotherapy with a lower risk of GvHD is needed, and several study groups are working on that topic.

Prophylactic transfer of BCR-ABL–, PR1-, and WT1-reactive donor T cells after T cell–depleted allogeneic hematopoietic cell transplantation in patients with chronic myeloid leukemia

Donor lymphocyte infusions have been effective in patients with chronic myeloid leukemia (CML) relapsing after allogeneic stem cell transplantation, but their use is associated with the risk of graft-versus-host disease. We investigated the effects of prophylactic infusion of in vitro-generated donor T cells reactive against peptides derived from CML-associated antigens. Fourteen CML patients received conditioning therapy followed by CD34+-selected peripheral blood stem cells from matched siblings (n = 7) or unrelated (n = 7) donors. Donor-derived mature dendritic cells generated in vitro from CD14+ monocytes were loaded with human leukocyte Ag-restricted peptides derived from PR1, WT1, and/or B-cell receptor–ABL and used to repetitively stimulate donor CD8+ T cells in the presence of IL-2 and IL-7. Stimulated T cells were infused 28, 56, and 112 days after transplantation. Thirteen patients are alive and 7 remain in molecular remission (median follow-up, 45 months). Interestingly, all 4 patients receiving CD8+ T cells displaying marked cytotoxic activity in vitro and detectable peptide-reactive CD8+ T cells during follow-up have not experienced graft-versus-host disease or relapse. Our study reveals that prophylactic infusion of allogeneic CD8+ T cells reactive against peptides derived from CML-associated antigens is a safe and promising therapeutic strategy. This trial was registered at www.clinicaltrials.gov as #NCT00460629.

CD8+ T cell differentiation in the aging immune system: until the last clone standing

A substantial deterioration of the naïve CD8(+) T cell pool occurs regularly in humans beyond the age of 65 years. While recall responses to pathogens encountered during youth or adulthood are largely uncompromised, the de novo generation of memory responses by aged naïve CD8(+) T cells is perturbed. In recent years evidence has accumulated that the diminished responsiveness of naïve CD8(+) T cells in aged humans and other mammals coincides with a progressive loss of naïve T cell receptor (TCR) repertoire diversity. In this review we focus on thymic involution and chronic latent viral infections as key factors driving the reduction in naïve TCR repertoire diversity. We present novel insights gained by studying the antigen-driven differentiation of single CD8(+) T cells in young hosts and discuss possible implications of these insights for therapeutic support of the thinned-out clonal T cell repertoire of the elderly by vaccination or adoptive cell therapy.

Virus-specific T cells for therapy--approaches, problems, solutions

Adoptive T cell therapy is the transfer of T cells to a patient in order to combat disease. This procedure is mainly being used but not limited to the treatment of viral infections and malignancies including virus-associated tumors. Depending on the clinical context, the T cell donor may be the same patient or another donor, usually a healthy person. Recent research is centered on the use of antigen-specific T cells, but T cells of uncharacterized specificity can be successfully used in some clinical conditions where target antigens are not known. Depending on underlying scientific hypotheses and preferred technologies, the therapeutic T cells may be anything from monoclonal to highly polyclonal; they may be specific for one epitope, several epitopes from one antigen, or various antigens; they may have been selected during the preparation process for their specificity, their functional capacity, their survival and proliferation in vitro, or the expression of surface markers associated with desirable functional properties. In this minireview, we give a brief overview on selected approaches, problems and solutions in adoptive T cell therapy. We focus on an area where T cell therapy has been particularly successful but is still calling for improvement: herpesviral disease in patients after transplantation.

Cytomegalovirus: pathogen, paradigm, and puzzle

Human cytomegalovirus (CMV), one of the eight herpesviruses that commonly infect humans, is best known for its propensity to cause disease in immunocompromised patients, especially transplant recipients, patients with advanced AIDS, and congenitally infected newborns. Advances in molecular virology coupled with improvements in diagnostic methods and treatment options have vastly improved our understanding of and ability to manage CMV, but many uncertainties remain, including the mechanisms of persistence and pathogenesis and its hypothesized roles in a variety of human illnesses. Here we review recent advances that are reshaping our view and approach to this fascinating virus.