Immunotherapy to reconstitute immunity to DNA viruses

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

Recovery of cytomegalovirus (CMV)-specific immunity after hematopoietic cell transplantation (HCT) is essential in controlling CMV infection. We hypothesize that mixed donor engraftment as measured by chimerism at day 30 in CMV D(+) HCTs and full chimerism in CMV D(-) HCTs will be predictive of CMV reactivation. Prospectively collected data for 407 CMV R+ HCT recipients transplanted from 2006 to 2014 at the University of Minnesota were retrospectively analyzed. Full and mixed donor engraftment were defined as ≥95% or <95% donor cells at day 30, respectively. Source of engraftment determination included preferentially peripheral blood CD3 fraction, then myeloid cell fraction (CD15+), then bone marrow. In 407 CMV R+ subjects, 77% (n = 313) were CMV D(-) cells from umbilical cord blood (n = 209), peripheral blood (n = 58) or marrow (n = 46). Fifty three per cent received reduced intensity conditioning (RIC). At day +30, full donor engraftment was seen in 82% of myeloablative and 55% of RIC transplants. The cumulative incidence of CMV infection 1-year after transplant was not different in patients with full (54%, n = 276) or mixed (53%, n = 131) donor engraftment. Control of CMV did not significantly differ among the two groups. In multiple regression analysis, there was no significant association between donor engraftment (mixed or full) and incidence or control of CMV.

Generation of HIV-1-specific T cells by electroporation of T-cell receptor RNA

BACKGROUND

HIV-1-specific cytotoxic T lymphocytes, which recognize conserved epitopes of the virus, are correlated with prolonged survival of infected individuals. Unfortunately, most HIV-1-infected patients are unable to generate such an immune response. Antigen-specific cytotoxic T lymphocytes can be generated by T-cell receptor transfer. This is commonly done by retroviral transduction, which is complicated and poses the threat of stable genetic alteration of autologous cells.

METHODS

We reprogrammed primary CD8+ T cells by electroporation of RNA, which encoded an HIV-1-pol- and an HIV-1-gag-specific T-cell receptor recognizing the human leukocyte antigen-A2 restricted epitopes ILKEPVHGV and SLYNTVATL, respectively.

RESULTS

These reprogrammed cells specifically produced the proinflammatory cytokines interleukin-2, tumor necrosis factor-alpha, and interferon-gamma after stimulation with target cells that presented the corresponding peptides, and were able to lyse these targets efficiently and specifically. The lytic avidities of the HIV-1-pol- and HIV-1-gag-TCR-RNA-electroporated CD8+ T cells were within the same range than those of the parental cytotoxic T lymphocytes. Most importantly, HIV-1-gag-reprogrammed T cells recognized target cells that presented endogenously processed antigen, which resulted in cytokine production and lysis.

CONCLUSION

It is shown here for the first time that functional transfer of virus-specific T-cell receptors by RNA electroporation is feasible, and represents an innovative, safe, and easy method to generate virus-specific T cells, avoiding the risks of retroviral transduction.

Induction of therapeutic T-cell responses to subdominant tumor-associated viral oncogene after immunization with replication-incompetent polyepitope adenovirus vaccine

The EBV-encoded latent membrane proteins (LMP1 and LMP2), which are expressed in various EBV-associated malignancies have been proposed as a potential target for CTL-based therapy. However, the precursor frequency for LMP-specific CTL is generally low, and immunotherapy based on these antigens is often compromised by the poor immunogenicity and potential threat from their oncogenic potential. Here we have developed a replication- incompetent adenoviral vaccine that encodes multiple HLA class I-restricted CTL epitopes from LMP1 and LMP2 as a polyepitope. Immunization with this polyepitope vaccine consistently generated strong LMP-specific CTL responses in HLA A2/K(b) mice, which can be readily detected by both ex vivo and in vivo T-cell assays. Furthermore, a human CTL response to LMP antigens can be rapidly expanded after stimulation with this recombinant polyepitope vector. These expanded T cells displayed strong lysis of autologous target cells sensitized with LMP1 and/or LMP2 CTL epitopes. More importantly, this adenoviral vaccine was also successfully used to reverse the outgrowth of LMP1-expressing tumors in HLA A2/K(b) mice. These studies demonstrate that a replication-incompetent adenovirus polyepitope vaccine is an excellent tool for the induction of a protective CTL response directed toward multiple LMP CTL epitopes restricted through common HLA class I alleles prevalent in different ethnic groups where EBV-associated malignancies are endemic.

Dendritic cells initiate immune control of epstein-barr virus transformation of B lymphocytes in vitro

The initiation of cell-mediated immunity to Epstein-Barr virus (EBV) has been analyzed with cells from EBV-seronegative blood donors in culture. The addition of dendritic cells (DCs) is essential to prime naive T cells that recognize EBV-latent antigens in enzyme-linked immunospot assays for interferon γ secretion and eradicate transformed B cells in regression assays. In contrast, DCs are not required to control the outgrowth of EBV-transformed B lymphocytes from seropositive donors. Enriched CD4⁺ and CD8⁺ T cells mediate regression of EBV-transformed cells in seronegative and seropositive donors, but the kinetics of T-dependent regression occurs with much greater speed with seropositives. EBV infection of DCs cannot be detected by reverse transcription–polymerase chain reaction with primers specific for mRNA for the EBNA1 U and K exons. Instead, DCs capture B cell debris and generate T cells specific for EBV latency antigens. We suggest that the cross-presentation of EBV-latent antigens from infected B cells by DCs is required for the initiation of EBV-specific immune control in vivo and that future EBV vaccine strategies should target viral antigens to DCs.

Respiratory virus infections in the immunocompromised host

The number of immunocompromised children in the population is increasing for a variety of reasons. Common respiratory viruses acquired in the community or in the hospital setting include the ortho- and paramyxoviruses and may cause severe lower respiratory tract disease in these children. Measles is again becoming a threat. Particularly in transplant patients, Herpes group viruses and adenoviruses, often part of a reactivation illness, can cause potentially life-threatening disease. The use of rapid molecular diagnostic techniques and an increasing array of antiviral therapies can help ensure a good outcome in many cases, although controlled clinical trial data are often lacking. Immunotherapeutic strategies using specific antibodies or cytotoxic T cells are being developed and are likely to have an increasing role in prophylaxis and pre-emptive therapy in the future. The development and introduction of vaccines against common respiratory diseases will help reduce the risks faced by these susceptible children.

Therapeutic LMP1 polyepitope vaccine for EBV-associated Hodgkin disease and nasopharyngeal carcinoma

Development of an epitope-based vaccination strategy designed to enhance Epstein-Barr virus (EBV)-specific CD8(+) cytotoxic T lymphocytes (CTLs) is increasingly being considered as a preferred approach for the treatment of EBV-associated relapsed Hodgkin disease (HD) and nasopharyngeal carcinoma (NPC). EBV-encoded latent membrane proteins, LMP1 and LMP2, are the only target antigens available for therapeutic augmentation of CTL responses in patients with HD and NPC. Here, we describe preclinical studies using a recombinant poxvirus vaccine that encodes a polyepitope protein comprising 6 HLA A2-restricted epitopes derived from LMP1. Human cells infected with this recombinant polyepitope construct were efficiently recognized by LMP1-specific CTL lines from HLA A2 healthy individuals. Furthermore, immunization of HLA A2/K(b) mice with this polyepitope vaccine consistently generated strong LMP1-specific CTL responses to 5 of the 6 epitopes, which were readily detected by both ex vivo and in vitro assays. More important, this polyepitope vaccine successfully reversed the outgrowth of LMP1-expressing tumors in HLA A2/K(b) mice. These studies provide an important platform for the development of an LMP-based polyepitope vaccine as an immunotherapeutic tool for the treatment of EBV-associated HD and NPC.

Cellular therapy for haematological malignancies

The aim of this review was to summarize the recent progress made in the field of cellular therapeutics in haematological malignancy. The review also examined the role that the National Transfusion Services might play in the manufacture of new cellular therapeutic agents, given both their expertise in the safe provision of blood products and their possession of accredited cell manipulation facilities. Cellular therapy is entering an era in which novel cellular products will find increasing clinical use, particularly in the areas of haematopoietic stem cell transplantation and immunotherapy. The production of novel cell-based therapies, both in Europe and North America, is now under strict regulatory control and therefore collaboration with the National Transfusion Services in the manufacture of these agents may well be beneficial if the production standards demanded by the regulatory authorities are to be fulfilled.

Clinical developments in reduced intensity haematopoietic stem cell transplantation

Reduced intensity conditioning regimens prior to allogeneic haematopoietic stem cell transplantation (HSCT) were first described in the 1970s, and have developed rapidly over the past few years to become an important consideration as immunological therapy for patients with haematological and selected solid organ malignancies. This is especially the case for patients considered ineligible for conventional allogeneic HSCT due to age or medical contraindications. With the development of minimally toxic conditioning regimens, additional potential applications include the provision of normal haematopoietic repopulating cells to patients who have an inherited gene defect such as an haemoglobinopathy or an inborn error of metabolism. Intensive investigation in stem cell research promises to provide dramatic new insights into human biology, paving the way for new therapeutic approaches to malignant and inherited disorders.

T-cell therapy of leukemia

BACKGROUND

The demonstration that immune-mediated elimination of leukemia contributes to the success of allogeneic hematopoietic stem cell transplantation (HSCT) has renewed interest in the development of immune-based therapies that might be used to augment the antileukemic effect of HSCT or in patients who are not receiving HSCT.

METHODS

The authors reviewed studies that have analyzed the mechanisms that may be operative in T-cell recognition of leukemia after allogeneic HSCT, identified candidate target antigens for immunotherapy of leukemia in transplant and nontransplant patients, and evaluated expression of candidate antigens on leukemic progenitors.

RESULTS

A large number of potential targets for T-cell therapy or vaccination have now been identified in human leukemia. Studies to evaluate novel immune-based therapies are now being initiated.

CONCLUSIONS

The rapid pace of progress in cellular and molecular immunology has identified new opportunities for developing T-cell therapy or vaccination for leukemia. Obstacles must be addressed before these approaches can be applied broadly, but the promising results of preclinical studies suggest continued efforts in this area will result in the establishment of immunotherapy as a useful modality in clinical practice.