Synthetic modified vaccinia Ankara vaccines confer cross-reactive and protective immunity against mpox virus

BACKGROUND

Although the mpox global health emergency caused by mpox virus (MPXV) clade IIb.1 has ended, mpox cases are still reported due to low vaccination coverage and waning immunity. COH04S1 is a clinically evaluated, multiantigen COVID-19 vaccine candidate built on a fully synthetic platform of the highly attenuated modified vaccinia Ankara (MVA) vector, representing the only FDA-approved smallpox/mpox vaccine JYNNEOS. Given the potential threat of MPXV resurgence and need for vaccine alternatives, we aimed to assess the capacity COH04S1 and its synthetic MVA (sMVA) backbone to confer MPXV-specific immunity.

METHODS

We evaluated orthopoxvirus-specific and MPXV cross-reactive immune responses in samples collected during a Phase 1 clinical trial of COH04S1 and in non-human primates (NHP) vaccinated with COH04S1 or its sMVA backbone. MPXV cross-reactive immune responses in COH04S1-vaccinated healthy adults were compared to responses measured in healthy subjects vaccinated with JYNNEOS. Additionally, we evaluated the protective efficacy of COH04S1 and sMVA against mpox in mpox-susceptible CAST/EiJ mice.

RESULTS

COH04S1-vaccinated individuals develop robust orthopoxvirus-specific humoral and cellular responses, including cross-reactive antibodies to MPXV-specific virion proteins as well as MPXV cross-neutralizing antibodies in 45% of the subjects. In addition, NHP vaccinated with COH04S1 or sMVA show similar MPXV cross-reactive antibody responses. Moreover, MPXV cross-reactive humoral responses elicited by COH04S1 are comparable to those measured in JYNNEOS-vaccinated subjects. Finally, we show that mice vaccinated with COH04S1 or sMVA are protected from lung infection following challenge with MPXV clade IIb.1.

CONCLUSIONS

These results demonstrate the capacity of sMVA vaccines to elicit cross-reactive and protective orthopox-specific immunity against MPXV, suggesting that COH04S1 and sMVA could be developed as bivalent or monovalent mpox vaccine alternatives against MPXV.

Recurrent SARS-CoV-2 mutations at Spike D796 evade antibodies from pre-Omicron convalescent and vaccinated subjects

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineages of the Omicron variant rapidly became dominant in early 2022 and frequently cause human infections despite vaccination or prior infection with other variants. In addition to antibody-evading mutations in the receptor-binding domain, Omicron features amino acid mutations elsewhere in the Spike protein; however, their effects generally remain ill defined. The Spike D796Y substitution is present in all Omicron sub-variants and occurs at the same site as a mutation (D796H) selected during viral evolution in a chronically infected patient. Here, we map antibody reactivity to a linear epitope in the Spike protein overlapping position 796. We show that antibodies binding this region arise in pre-Omicron SARS-CoV-2 convalescent and vaccinated subjects but that both D796Y and D796H abrogate their binding. These results suggest that D796Y contributes to the fitness of Omicron in hosts with pre-existing immunity to other variants of SARS-CoV-2 by evading antibodies targeting this site.IMPORTANCESevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved substantially through the coronavirus disease 2019 (COVID-19) pandemic: understanding the drivers and consequences of this evolution is essential for projecting the course of the pandemic and developing new countermeasures. Here, we study the immunological effects of a particular mutation present in the Spike protein of all Omicron strains and find that it prevents the efficient binding of a class of antibodies raised by pre-Omicron vaccination and infection. These findings reveal a novel consequence of a poorly understood Omicron mutation and shed light on the drivers and effects of SARS-CoV-2 evolution.

Stimulation of Potent Humoral and Cellular Immunity via Synthetic Dual-Antigen MVA-Based COVID-19 Vaccine COH04S1 in Cancer Patients Post Hematopoietic Cell Transplantation and Cellular Therapy

Hematopoietic cell transplantation (HCT) and chimeric antigen receptor (CAR)-T cell patients are immunocompromised, remain at high risk following SARS-CoV-2 infection, and are less likely than immunocompetent individuals to respond to vaccination. As part of the safety lead-in portion of a phase 2 clinical trial in patients post HCT/CAR-T for hematological malignancies (HM), we tested the immunogenicity of the synthetic modified vaccinia Ankara-based COVID-19 vaccine COH04S1 co-expressing spike (S) and nucleocapsid (N) antigens. Thirteen patients were vaccinated 3-12 months post HCT/CAR-T with two to four doses of COH04S1. SARS-CoV-2 antigen-specific humoral and cellular immune responses, including neutralizing antibodies to ancestral virus and variants of concern (VOC), were measured up to six months post vaccination and compared to immune responses in historical cohorts of naïve healthy volunteers (HV) vaccinated with COH04S1 and naïve healthcare workers (HCW) vaccinated with the FDA-approved mRNA vaccine Comirnaty® (Pfizer, New York, NY, USA). After one or two COH04S1 vaccine doses, HCT/CAR-T recipients showed a significant increase in S- and N-specific binding antibody titers and neutralizing antibodies with potent activity against SARS-CoV-2 ancestral virus and VOC, including the highly immune evasive Omicron XBB.1.5 variant. Furthermore, vaccination with COH04S1 resulted in a significant increase in S- and N-specific T cells, predominantly CD4+ T lymphocytes. Elevated S- and N-specific immune responses continued to persist at six months post vaccination. Furthermore, both humoral and cellular immune responses in COH04S1-vaccinated HCT/CAR-T patients were superior or comparable to those measured in COH04S1-vaccinated HV or Comirnaty®-vaccinated HCW. These results demonstrate robust stimulation of SARS-CoV-2 S- and N-specific immune responses including cross-reactive neutralizing antibodies by COH04S1 in HM patients post HCT/CAR-T, supporting further testing of COH04S1 in immunocompromised populations.

Vaccine-induced spike- and nucleocapsid-specific cellular responses maintain potent cross-reactivity to SARS-CoV-2 Delta and Omicron variants

Cell-mediated immunity may contribute to providing protection against SARS-CoV-2 and its variants of concern (VOC). We developed COH04S1, a synthetic multiantigen modified vaccinia Ankara (MVA)-based COVID-19 vaccine that stimulated potent spike (S) and nucleocapsid (N) antigen-specific humoral and cellular immunity in a phase 1 clinical trial in healthy adults. Here, we show that individuals vaccinated with COH04S1 or mRNA vaccine BNT162b2 maintain robust cross-reactive cellular immunity for six or more months post-vaccination. Although neutralizing antibodies induced in COH04S1- and BNT162b2-vaccinees showed reduced activity against Delta and Omicron variants compared to ancestral SARS-CoV-2, S-specific T cells elicited in both COH04S1- and BNT162b2-vaccinees and N-specific T cells elicited in COH04S1-vaccinees demonstrated potent and equivalent cross-reactivity against ancestral SARS-CoV-2 and the major VOC. These results suggest that vaccine-induced T cells to S and N antigens may constitute a critical second line of defense to provide long-term protection against SARS-CoV-2 VOC.

COVID-19 vaccination elicits an evolving, cross-reactive antibody response to epitopes conserved with endemic coronavirus spike proteins

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Many vaccinated subjects are previously naive to SARS-CoV-2; however, almost all have previously encountered other coronaviruses (CoVs), and the role of this immunity in shaping the vaccine response remains uncharacterized. Here, we use longitudinal samples and highly multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes, in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes shows a delayed but progressive increase following vaccination, we observe distinct kinetics for the endemic CoV homologs at conserved sites in Spike S2: these become detectable sooner and decay at later time points. Using homolog-specific antibody depletion and alanine-substitution experiments, we show that these distinct trajectories reflect an evolving cross-reactive response that can distinguish rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

Pre-clinical data supporting immunotherapy for HIV using CMV-HIV-specific CAR T cells with CMV vaccine

T cells engineered to express HIV-specific chimeric antigen receptors (CARs) represent a promising strategy to clear HIV-infected cells, but to date have not achieved clinical benefits. A likely hurdle is the limited T cell activation and persistence when HIV antigenemia is low, particularly during antiretroviral therapy (ART). To overcome this issue, we propose to use a cytomegalovirus (CMV) vaccine to stimulate CMV-specific T cells that express CARs directed against the HIV-1 envelope protein gp120. In this study, we use a GMP-compliant platform to engineer CMV-specific T cells to express a second-generation CAR derived from the N6 broadly neutralizing antibody, one of the broadest anti-gp120 neutralizing antibodies. These CMV-HIV CAR T cells exhibit dual effector functions upon in vitro stimulation through their endogenous CMV-specific T cell receptors or the introduced CARs. Using a humanized HIV mouse model, we show that CMV vaccination during ART accelerates CMV-HIV CAR T cell expansion in the peripheral blood and that higher numbers of CMV-HIV CAR T cells were associated with a better control of HIV viral load and fewer HIV antigen p24⁺ cells in the bone marrow upon ART interruption. Collectively, these data support the clinical development of CMV-HIV CAR T cells in combination with a CMV vaccine in HIV-infected individuals.

COVID-19 vaccination recruits and matures cross-reactive antibodies to conserved epitopes in endemic coronavirus Spike proteins.. [PMID: 35118479 PMCID: PMC8811912 DOI: 10.1101/2022.01.24.22269542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Most vaccinated subjects are naïve to SARS-CoV-2, however almost all have previously encountered other coronaviruses (CoVs) and the role of this immunity in shaping the vaccine response remains uncharacterized. Here we use longitudinal samples and highly-multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes and in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes showed a delayed but progressive increase following vaccination, we observed distinct kinetics for the endemic CoV homologs at two conserved sites in Spike S2: these became detectable sooner, and decayed at later timepoints. Using homolog-specific depletion and alanine-substitution experiments, we show that these distinctly-evolving specificities result from cross-reactive antibodies as they mature against rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

Cost analysis of ganciclovir and foscarnet in recipients of allogeneic hematopoietic cell transplant with cytomegalovirus viremia

BACKGROUND

Ganciclovir (GCV) and foscarnet (FOS) are the most commonly used antivirals for preemptive treatment of cytomegalovirus (CMV) viremia in recipients of allogeneic hematopoietic cell transplantation (alloHCT). The current literature indicates similar efficacy between these agents. Thus, the primary consideration for choice of initial anti-CMV treatment is the safety profile, time period after alloHCT, and concern of myelosuppression or renal dysfunction.

METHODS

Herein, we retrospectively reviewed medical records of 124 alloHCT recipients who received GCV or FOS between April 27, 2014, and December 31, 2015, during the first year post-transplant. Healthcare resource use included drug, hospitalization, home health, dialysis, and growth factor costs.

RESULTS

Total duration of therapy was longer in the GCV group (37 days vs 28 days, P = .21) but hospitalization days were similar (9 days) in both groups. The total treatment cost was significantly lower in the GCV group ($38 100 vs $59 400, P < .05).

CONCLUSION

Preemptive anti-CMV therapy is associated with major healthcare resource costs, which were greater in patients who required FOS than those who were treated with GCV.

Influence of donor KIR genotypes on reduced relapse risk in acute myelogenous leukemia after hematopoietic stem cell transplantation in patients with CMV reactivation

Multiple retrospective studies have demonstrated an association between cytomegalovirus (CMV) reactivation and reduced risk of AML relapse. However, the potential mechanism explaining this association remains elusive. We investigated a homogeneous cohort of 288 adult patients with AML in remission who received allogeneic hematopoietic stem cell transplantation (HCT) from matched sibling/unrelated donors between 1995 and 2011. The 5-year cumulative incidence of relapse was greater in patients without CMV reactivation compared with those with reactivation (30.2% vs. 12.1%, p = 0.001) in a landmark analysis. In multivariate analyses CMV reactivation was independently associated with reduced relapse risk (HR: 0.49 [0.25-0.95], p = 0.036) and increased non-relapse mortality (26.5% vs. 13.1%, p = 0.002) resulting in similar 5-year overall survival (64.5% vs. 59.1%, p = 0.8). In further subgroup analyses the protective effect of CMV reactivation was significant in patients who received HCT from donors with KIR Bx compared to KIR AA (11.7% vs. 29.5%, p = 0.01). Likewise, the protective effect of CMV reactivation was more significant when the donors had 2DS1 activating KIR (11.5% vs. 30.7%, p = 0.05) compared with those without 2DS1 (14.3% vs. 27.5%, p = 0.12). Our data independently confirmed the association between CMV reactivation and AML relapse, suggesting the involvement of donor KIR genotypes and NK cell-mediated graft-versus-leukemia effect.

A fifty-year odyssey: prospects for a cytomegalovirus vaccine in transplant and congenital infection

INTRODUCTION

It has been almost fifty years since the Towne strain was used by Plotkin and collaborators as the first vaccine candidate for cytomegalovirus (CMV). While that approach showed partial efficacy, there have been a multitude of challenges to improve on the promise of a CMV vaccine. Efforts have been dichotomized into a therapeutic vaccine for patients with CMV-infected allografts, either stem cells or solid organ, and a prophylactic vaccine for congenital infection.

AREAS COVERED

This review will evaluate research prospects for a therapeutic vaccine for transplant recipients that recognizes CMV utilizing primarily T cell responses. Similarly, we will provide an extensive discussion on attempts to develop a vaccine to prevent the manifestations of congenital infection, based on eliciting a humoral anti-CMV protective response. The review will also describe newer developments that have upended the efforts toward such a vaccine through the discovery of a second pathway of CMV infection that utilizes an alternative receptor for entry using a series of antigens that have been determined to be important for prevention of infection.

EXPERT COMMENTARY

There is a concerted effort to unify separate therapeutic and prophylactic vaccine strategies into a single delivery agent that would be effective for both transplant-related and congenital infection.

Role of Nursing Competencies for Accelerating Clinical Trials in Stem Cell Clinics

The California Institute for Regenerative Medicine has formed a group of clinics called the Alpha Stem Cell Clinics Network. Its goal is to accelerate clinical trials of stem cell‐based therapies for diseases with unmet medical needs. In this report, we describe our experience in establishing an Alpha Stem Cell Clinic at City of Hope. Implementation and integration of the clinic into the existing institutional structures required collaboration and cooperation with clinical trial units, nursing administration, and creation of new positions. The highlight of this process and the centerpiece to our success has been the definition of the role of the “hybrid nurse,” a person with nursing competencies in both clinical care and research. stemcellstranslationalmedicine2018;7:6–10

Abstract Video Link: https://youtu.be/WOeZrNyXkGU

Preclinical development and qualification of ZFN-mediated CCR5 disruption in human hematopoietic stem/progenitor cells

Gene therapy for HIV-1 infection is a promising alternative to lifelong combination antiviral drug treatment. Chemokine receptor 5 (CCR5) is the coreceptor required for R5-tropic HIV-1 infection of human cells. Deletion of CCR5 renders cells resistant to R5-tropic HIV-1 infection, and the potential for cure has been shown through allogeneic stem cell transplantation with naturally occurring homozygous deletion of CCR5 in donor hematopoietic stem/progenitor cells (HSPC). The requirement for HLA-matched HSPC bearing homozygous CCR5 deletions prohibits widespread application of this approach. Thus, a strategy to disrupt CCR5 genomic sequences in HSPC using zinc finger nucleases was developed. Following discussions with regulatory agencies, we conducted IND-enabling preclinical in vitro and in vivo testing to demonstrate the feasibility and (preclinical) safety of zinc finger nucleases-based CCR5 disruption in HSPC. We report here the clinical-scale manufacturing process necessary to deliver CCR5-specific zinc finger nucleases mRNA to HSPC using electroporation and the preclinical safety data. Our results demonstrate effective biallelic CCR5 disruption in up to 72.9% of modified colony forming units from adult mobilized HSPC with maintenance of hematopoietic potential in vitro and in vivo. Tumorigenicity studies demonstrated initial product safety; further safety and feasibility studies are ongoing in subjects infected with HIV-1 (NCT02500849@clinicaltrials.gov).

Viraemia, immunogenicity, and survival outcomes of cytomegalovirus chimeric epitope vaccine supplemented with PF03512676 (CMVPepVax) in allogeneic haemopoietic stem-cell transplantation: randomised phase 1b trial

BACKGROUND

Patients seropositive for cytomegalovirus (CMV) and undergoing allogeneic haemopoietic stem-cell transplantation (HCT) are at risk for CMV reactivation. Stimulating viral immunity by vaccination might achieve CMV viraemia control without the need for antiviral agents. CMVPepVax is a chimeric peptide composed of a cytotoxic CD8 T-cell epitope from CMV pp65 and a tetanus T-helper epitope. It is formulated with the adjuvant PF03512676, a Toll-like receptor 9 agonist, which augments cellular immunity. We aimed to assess safety, immunogenicity, and possible clinical benefit of the CMVPepVax vaccine in patients undergoing HCT.

METHODS

We did a randomised, open-label, phase 1b trial at one transplant centre in the USA. Eligible patients were CMV-seropositive, positive for HLA-A*0201, aged 18-75 years, and undergoing HCT from a matched-related or matched-unrelated donor. Patients were reassessed for eligibility on day 28 after HCT. We randomly allocated patients to either the CMVPepVax vaccine or observation, in blocks stratified by CMV donor serostatus. CMVPepVax was administered subcutaneously on days 28 and 56. The primary outcome was safety, which consisted of secondary graft failure, grade III-IV acute GVHD, non-relapse mortality by day 100, serious adverse events related to the vaccine (judged by the data and safety monitoring committee [DSMC]) grade 3-4 adverse events related to the vaccine (judged by the DSMC) within 2 weeks of vaccination, and development of double-strand (ds) DNA autoantibodies. Statistical analyses included all randomised patients and were done per-protocol. This study is registered with ClinicalTrials.gov, number NCT01588015. This trial is closed to accrual and the final analysis is presented in this report.

FINDINGS

Between Oct 31, 2012, and Nov 5, 2014, 36 eligible patients were allocated to either CMVPepVax (n=18) or observation (n=18), with no adverse effect on HCT (no secondary graft failures in either group) or cases of acute GVHD (seven patients assigned vaccine and six under observation had acute GVHD of grade 2 or less), and no unexpected adverse events. Compared with observation, better relapse-free survival was recorded in patients allocated the vaccine (seven vs one; hazard ratio [HR] 0·12, 95% CI 0·01-0·94; p=0·015). No patients had non-relapse mortality by day 100. One serious adverse event (grade 1 fever) was attributed to CMVPepVax but resolved within 48 h. Four patients assigned the vaccine had a serious adverse event, which was unrelated to the vaccine (grade 3 thrombocytopenia, grade 3 device-related infection, grade 2 nausea, and grade 1 fever), compared with nine patients under observation (grade 4 maculopapular rash, grade 3 nausea, grade 3 infection, grade 3 thrombotic thrombocytopenic purpurea, grade 2 nausea, grade 2 generalised muscle weakness, grade 2 infection, grade 1 fever, and grade 1 fatigue; p=0·16). 54 grade 3-4 adverse events were reported in patients assigned the vaccine compared with 91 in patients who were under observation (p=0·2). No patients had grade III-IV acute GVHD or developed dsDNA autoantibodies.

INTERPRETATION

The results show safety and immunogenicity of the CMVPepVax vaccine. The prospect of substantial clinical benefits warrant testing in a phase 2 trial.

FUNDING

National Cancer Institute.

CMVpp65 Vaccine Enhances the Antitumor Efficacy of Adoptively Transferred CD19-Redirected CMV-Specific T Cells

PURPOSE

T cells engineered with chimeric antigen receptors (CAR) recognizing CD19 can induce complete remission of B-cell malignancies in clinical trials; however, in some disease settings, CAR therapy confers only modest clinical benefit due to attenuated persistence of CAR T cells. The purpose of this study was to enhance persistence and augment the antitumor activity of adoptively transferred CD19CAR T cells by restimulating CAR(+) T cells through an endogenous cytomegalovirus (CMV)-specific T-cell receptor.

EXPERIMENTAL DESIGN

CMV-specific T cells from CMV seropositive healthy donors were selected after stimulation with pp65 protein and transduced with clinical-grade lentivirus expressing the CD19R:CD28:ζ/EGFRt CAR. The resultant bispecific T cells, targeting CMV and CD19, were expanded via CD19 CAR-mediated signals using CD19-expressing cells.

RESULTS

The bispecific T cells proliferated vigorously after engagement with either endogenous CMVpp65 T-cell receptors or engineered CD19 CARs, exhibiting specific cytolytic activity and IFNγ secretion. Upon adoptive transfer into immunodeficient mice bearing human lymphomas, the bispecific T cells exhibited proliferative response and enhanced antitumor activity following CMVpp65 peptide vaccine administration.

CONCLUSIONS

We have redirected CMV-specific T cells to recognize and lyse tumor cells via CD19CARs, while maintaining their ability to proliferate in response to CMV antigen stimulation. These results illustrate the clinical applications of CMV vaccine to augment the antitumor activity of adoptively transferred CD19CAR T cells in patients with B-cell malignancies.

HIV-associated non-Hodgkin lymphoma: viral origins and therapeutic options

HIV infection is associated with an increased risk of malignancy, especially B-cell lymphoid malignancies. Many of these lymphomas are further driven by concomitant infection with viruses such as Epstein-Barr virus or Human Herpesvirus 8, the latter being implicated in uncommon types of lymphomas seen in the setting of HIV-1 infection. Treatment outcomes have improved due to infusional chemotherapy, high-dose chemotherapy, and effective antiretroviral therapy. Successful functional cure of HIV-1 infection has been demonstrated with the use of allogeneic hematopoietic stem cell transplantation. This result spurred a change in the field of HIV-1 management so that, ultimately, the goals of therapy would shift from not only curing the underlying lymphoma, but also curing the HIV-1 infection. Treatment options will be discussed with an emphasis on hematopoietic cell-based therapy for the underlying HIV infection.

Practical considerations in gene therapy for HIV cure

Despite the success of antiretroviral therapy in suppressing HIV-1 replication and extending the life of HIV-1 infected individuals, this regimen is associated with risks for non-AIDS morbidity and mortality, requires life commitment, and has a high cost. In this context, gene therapy approaches that have the potential to cure HIV-1 infection present a clear option for eradication of the virus in the next decades. Gene therapy must overcome concerns related to its applicability to HIV-1 infection, the safety of cytotoxic conditioning required for cell-based approaches, clinical trial design, selection of gene-modified cells, and the restrictive cost of manufacturing and technology. These concerns are discussed herein in the context of the most relevant gene therapy studies conducted so far in HIV/AIDS.

Detection and preliminary characterization of CD8+T lymphocytes specific for Wilms' tumor antigen in patients with non-Hodgkin lymphoma

Wilms' tumor antigen (WT1) is overexpressed in many different solid tumors and hematologic malignancies. However, little is known about WT1 expression or WT1-specific immune responses in patients with non-Hodgkin lymphoma (NHL). In a cross-sectional survey study, we investigated the immune recognition of WT1 by patients with NHL. Utilizing a WT1 overlapping peptide library, we discovered that a large percentage of patients with NHL of all grades maintain WT1-specific T cells. Ex vivo frequencies of these T cells measured from unfractionated samples by the CD137 activation marker assay were high in many patients (some > 1% CD8+). Using standard in vitro techniques we discovered that they were cytotoxic to WT1 peptide library-loaded T2 cells and WT1 antigen-primed autologous Epstein-Barr virus-transformed B cell lines (EBV-LCLs) and expressed interferon gamma (IFN-γ). In addition, we detected WT1 mRNA transcripts in diseased lymph node tissues of patients with NHL utilizing real-time quantitative polymerase chain reaction (RT-qPCR) technology. These results are the first example of strong T cell reactivity against WT1 in patients with NHL which also demonstrate strong cytotoxicity against peptide-loaded tumor cells. The potential for developing WT1 as a target for immunotherapy in NHL deserves further exploration.

Donor killer immunoglobulin-like receptor genes and reactivation of cytomegalovirus after HLA-matched hematopoietic stem-cell transplantation: HLA-C allotype is an essential cofactor

Natural killer (NK) cells whose killer immunoglobulin-like receptors (KIRs) recognize human leukocyte antigen (HLA) ligand are “licensed” for activity. In contrast, non-licensed NK cells display KIRs for which ligand is absent from the self genotype and are usually hyporesponsive. Surprisingly, non-licensed cells are active in tumor control after hematopoietic stem-cell transplantation (HSCT) and dominate NK response to murine cytomegalovirus (CMV) infection. From those reports, we hypothesized that control of human CMV early after HSCT is influenced by donor KIR genes whose HLA ligand is absent-from-genotype of HLA-matched donor and recipient. To investigate, we studied CMV reactivation through Day 100 after grafts involving CMV-seropositive donor and/or recipient. A multivariate proportional rates model controlled for variability in surveillance and established covariates including acute graft-versus-host disease; statistical significance was adjusted for testing of multiple KIRs with identified HLA class I ligand (2DL1, 2DL2/3, 2DS1, 2DS2, full-length 2DS4, 3DL1/3DS1, 3DL2). Among HSCT recipients (n = 286), CMV reactivation-free survival time varied with individual donor KIR genes evolutionarily specific for HLA-C: when ligand was absent from the donor/recipient genotype, inhibitory KIRs 2DL2 (P < 0.0001) and 2DL1 (P = 0.015) each predicted inferior outcome, and activating KIRs 2DS2 (P < 0.0001), 2DS1 (P = 0.016), and 2DS4 (P = 0.016) each predicted superior outcome. Otherwise, with ligand present-in-genotype, donor KIR genes had no effect. In conclusion, early after HLA-matched HSCT, individual inhibitory and activating KIR genes have qualitatively different effects on risk of CMV reactivation; unexpectedly, absence of HLA-C ligand from the donor/recipient genotype constitutes an essential cofactor in these associations. Being KIR- and HLA-C-specific, these findings are independent of licensing via alternate NK cell receptors (NKG2A, NKG2C) that recognize HLA-E.

Creating genetic resistance to HIV

HIV/AIDS remains a chronic and incurable disease, in spite of the notable successes of combination antiretroviral therapy. Gene therapy offers the prospect of creating genetic resistance to HIV that supplants the need for antiviral drugs. In sight of this goal, a variety of anti-HIV genes have reached clinical testing, including gene-editing enzymes, protein-based inhibitors, and RNA-based therapeutics. Combinations of therapeutic genes against viral and host targets are designed to improve the overall antiviral potency and reduce the likelihood of viral resistance. In cell-based therapies, therapeutic genes are expressed in gene modified T lymphocytes or in hematopoietic stem cells that generate an HIV-resistant immune system. Such strategies must promote the selective proliferation of the transplanted cells and the prolonged expression of therapeutic genes. This review focuses on the current advances and limitations in genetic therapies against HIV, including the status of several recent and ongoing clinical studies.

KIR2DS2 and KIR2DS4 promoter hypomethylation patterns in patients undergoing hematopoietic cell transplantation (HCT)

The killer cell Ig-like receptor (KIR)-MHC class I pathway is an integral part of natural killer cell immunity, and its role in host protection from both cancer and infection is important. In addition, we have shown elevated KIR2DS2 and 2DS4 expression in PBMCs of patients undergoing hematopoietic cell transplantation (HCT) [1]. Since all inhibitory KIR promoters are known to be heavily methylated, the question asked here is how and when KIR2DS2 and 2DS4 promoters had changed their methylation profile in association with HCT. Genomic DNA, extracted from 20 KIR2DS2/4+ donor and recipient cells, was treated with sodium bisulfate that will modify the unmethylated cytosine into uracil. Sequencing chromatographs were examined for C/T double peak indicative of base conversion. A CpG island in KIR2DS2 promoter spans from -160 to +26 with six cytosine sites. In contrast, the KIR2DS4 promoter CpG island contains three cytosine sites. The noted increase of unmethylated sites was associated with increased KIR expression as measured by mRNA-cDNA Q-PCR. In addition, the frequency of unmethylated sites in the CpG island was increased after HCT. The mechanism through which hypomethylation occurs after HCT is not known but it suggests a linkage to NK clonal expansion during the process of NK education in response to transplant therapy or viral infection.

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.

Cytomegalovirus viral load and virus-specific immune reconstitution after peripheral blood stem cell versus bone marrow transplantation

Peripheral blood stem cell (PBSC) products contain more T cells and monocytes when compared with bone marrow (BM), leading to fewer bacterial and fungal infections. Cytomegelovirus (CMV) viral load and disease as well as CMV-specific immune reconstitution were compared in patients enrolled in a randomized trial comparing PSBC and BM transplantation. There was a higher rate of CMV infection and disease during the first 100 days after transplantation among PBSC recipients (any antigenemia/DNAemia: PBSC, 63% vs BM, 42%, P = .04; CMV disease: PBSC, 17% vs BM, 4%, P = .03). By 2 years, CMV disease rates were similar. The early increase in CMV events correlated temporarily with lower CMV-specific CD4(+) T helper and CD8(+) cytotoxic T lymphocyte function at 30 days after transplantation in PBSC recipients. By 3 months after transplantation and thereafter, CMV-specific immune responses were similar between BM and PBSC recipients. In conclusion, higher CMV infection and disease rates occurred in PBSC transplant recipients early after transplantation. These differences may be because of a transient delay in CMV-specific immune reconstitution following PBSC transplantation.

Expression of activating KIR2DS2 and KIR2DS4 genes after hematopoietic cell transplantation: relevance to cytomegalovirus infection

The important role of activating killer immunoglobulin-like receptors (KIRs) in protecting against cytomegalovirus (CMV) reactivation has been described previously in patients undergoing hematopoietic cell transplantation (HCT). More specifically, the presence of multiple activating KIRs and the presence of at least KIR2DS2 and KIR2DS4 in the donor genotype identified a group of HCT patients at low risk for CMV reactivation. However, CMV infection still occurs in patients with the KIR protective genotype, and the question has been raised as to whether this is related to the lack of KIR expression. In this report, expression of the KIR2DS2 and KIR2DS4 genes, as measured by mRNA-based quantitative polymerase chain reaction in both the donor cells and the HCT recipient cells, was studied relative to CMV reactivation. In the control samples from healthy donors, the median range for KIR2DS2 and KIR2DS4 expression was low, with 35% of donors considered null-expressers. Interestingly, KIR2DS2 and KIR2DS4 expression was elevated after HCT compared with donor expression before HCT, and was significantly elevated in CMV viremic compared with CMV nonviremic HCT recipients. The CMV seropositivity of donors was not associated with activating KIR expression, and donor null expression in those with the KIR2DS2 or KIR2DS4 genotype was not predictive for CMV reactivation in the recipient. After controlling for other transplant factors, including donor type (sibling or unrelated), transplant source (bone marrow or peripheral blood stem cells), and acute GVHD grade, regression analysis of elevated KIR gene expression found an association for both KIR2DS2 and KIR2DS4, with a 7-fold increase in risk for CMV reactivation. We speculate that the elevated activating KIR expression in CMV-viremic HCT recipients is either coincidental with factors that activate CMV or is initiated by CMV or cellular processes responsive to such CMV infection reactivation.

Allogeneic haematopoietic stem cell transplantation in patients with human immunodeficiency virus: the experiences of more than 25 years

For treatment of several malignancies, transplantation of allogeneic haematopoietic stem cells (HSCT) derived from bone marrow or peripheral blood has been used as a therapeutic procedure for decades. In the past, HSCT has been suggested as a treatment option for infection with the human immunodeficiency virus type 1 (HIV-1), but these attempts were mostly unsuccessful. Today, after the introduction of an active anti-retroviral therapy, the lifetime expectancy of HIV-infected patients has improved substantially, but nevertheless the incidence rate of malignancies in these patients has increased considerably. Therefore, it can be assumed that there will be a rising necessity for HIV-1-infected patients with malignancies for allogeneic HSCT. At the same time, there is increasing interest in treatment methods which might target the HIV-1 reservoir more effectively, and the question has been raised as to whether allogeneic HSCT could be linked to such strategies. In this paper the data of more than 25 years experience with allogeneic HSCT in patients with HIV-1 are reviewed and analysed.

RNA-based gene therapy for HIV with lentiviral vector-modified CD34(+) cells in patients undergoing transplantation for AIDS-related lymphoma

AIDS patients who develop lymphoma are often treated with transplanted hematopoietic progenitor cells. As a first step in developing a hematopoietic cell-based gene therapy treatment, four patients undergoing treatment with these transplanted cells were also given gene-modified peripheral blood-derived (CD34(+)) hematopoietic progenitor cells expressing three RNA-based anti-HIV moieties (tat/rev short hairpin RNA, TAR decoy, and CCR5 ribozyme). In vitro analysis of these gene-modified cells showed no differences in their hematopoietic potential compared with nontransduced cells. In vitro estimates of successful expression of the anti-HIV moieties were initially as high as 22% but declined to approximately 1% over 4 weeks of culture. Ethical study design required that patients be transplanted with both gene-modified and unmanipulated hematopoietic progenitor cells obtained from the patient by apheresis. Transfected cells were successfully engrafted in all four infused patients by day 11, and there were no unexpected infusion-related toxicities. Persistent vector expression in multiple cell lineages was observed at low levels for up to 24 months, as was expression of the introduced small interfering RNA and ribozyme. Therefore, we have demonstrated stable vector expression in human blood cells after transplantation of autologous gene-modified hematopoietic progenitor cells. These results support the development of an RNA-based cell therapy platform for HIV.

HIV status does not affect the outcome of autologous stem cell transplantation (ASCT) for non-Hodgkin lymphoma (NHL)

Randomized trials comparing autologous stem cell transplant (ASCT) to conventional chemotherapy have demonstrated superior survival among HIV-negative ASCT patients with relapsed non-Hodgkin lymphoma (NHL). Recent trials explored the feasibility of ASCT in the HIV setting. Although these studies have shown that ASCT in HIV-positive NHL patients (HIVpos-NHL) is well tolerated, the impact of HIV infection on long-term transplant outcome is not well characterized. Ongoing comparison of long-term survival following ASCT in HIVpos-NHL patients and HIVneg-NHL patients will allow investigators to explore whether there should be inclusion of HIVpos-NHL patients in ASCT trials. To study long-term outcome we conducted a single-institution matched case-controlled study in HIVpos-NHL patients (cases) and HIVneg-NHL patients (controls). Twenty-nine patients with HIVpos-NHL were matched with HIVneg-NHL controls on sex, time to ASCT, year of transplant, histology, age, disease status, number prior regimens, and conditioning regimen. Nonrelapse mortality (NRM) was similar: 11% (95% confidence interval [CI]: 4%-28%) in HIVpos-NHL patients and 4% (95% CI: 1%-25%) in HIVneg-NHL controls (P = .18). Two-year disease-free survival (DFS) for the HIVpos-NHL patients was 76% (95% CI: 62%-85%) and 56% (95% CI: 45%-66%) for the HIVneg-NHL controls (P = .33). Overall survival was also similar; the 2-year point estimates were 75% (95% CI: 61%-85%) and 75% (95% CI: 60%-85%), respectively (P = .93), despite inclusion of more poor risk HIVpos-NHL patients. These results provide further evidence that HIV status does not affect the long-term outcome of ASCT for NHL, and therefore HIV status alone should no longer exclude these patients from transplant clinical trials.

Increased programmed death-1 molecule expression in cytomegalovirus disease and acute graft-versus-host disease after allogeneic hematopoietic cell transplantation

To study the role of the programmed death-1 molecule (PD-1) in cytomegalovirus (CMV) infection and disease after allogeneic hematopoietic cell transplantation (HCT), 206 subjects were followed prospectively for immune response to CMV and assigned to 3 groups based on CMV outcome. The subjects were analyzed retrospectively for PD-1 expression in cryopreserved CD4+ and CD8+T cells collected at days 40, 90, 120, 150, 180, and 360 posttransplantation. HCT recipients with CMV disease (n=14) were compared with recipients with prolonged CMV infection, but no CMV disease (median duration of infection, 3 months; n=14) and with controls with no CMV infection who received similar transplants (n=22). The CMV disease group had a significantly higher mean fluorescein intensity of PD-1 in CD4+ (P < .05) and CD8+ (P < .05) lymphocytes at all time points studied. PD-1 expression also was significantly elevated in those with severe acute graft-versus-host disease (aGVHD), including the no-viremia group. The data suggest that PD-1 is induced by aGVHD even in the absence of CMV infection. This enhanced PD-1 expression during severe aGVHD and with CMV reactivation could explain the known role of aGVHD as a risk factor for CMV disease.

A fusion protein of HCMV IE1 exon4 and IE2 exon5 stimulates potent cellular immunity in an MVA vaccine vector

A therapeutic CMV vaccine incorporating an antigenic repertoire capable of eliciting a cellular immune response has yet to be successfully implemented for patients who already have acquired an infection. To address this problem, we have developed a vaccine candidate derived from modified vaccinia Ankara (MVA) that expresses three immunodominant antigens (pp65, IE1, IE2) from CMV. The novelty of this vaccine is the fusion of two adjacent exons from the immediate-early region of CMV, their successful expression in MVA, and robust immunogenicity in both primary and memory response models. Evaluation of the immunogenicity of the viral vaccine in mouse models shows that it can stimulate primary immunity against all three antigens in both the CD4(+) and CD8(+) T cell subsets. Evaluation of human PBMC from healthy CMV-positive donors or patients within 6 months of receiving hematopoietic cell transplant shows robust stimulation of existing CMV-specific CD4(+) and CD8(+) T cell subsets.

The status of gene vectors for the treatment of diabetes

Diabetes mellitus type 1 (DM1) represents one of the most obvious targets for successful treatment by gene transfer. The disease provides targets and methods for therapy that include suppression of autoimmunity, restoration of insulin responsiveness, functional replacement of pancreatic islets, and correction of vascular and nerve damage associated with prolonged hyperglycemia. The pathogenesis of DM1 is well understood and gene sequences are known that would support these various approaches for genetic intervention. However, a key limitation at present is the availability of efficient and reliable methods for delivery and sustained expression of the transferred DNA. Most genetic vectors are derived from viruses, and recent improvements in adenovirus-derived, lentivirus-derived, and adeno-associated virus-derived vectors suggest that these will have successful application to diabetes in the future.

Inhibition of HIV-1 replication with designed miRNAs expressed from RNA polymerase II promoters

Small interfering RNA (siRNA) mediates sequence-specific RNA cleavage and represents a potential approach to treat the infection of human immunodeficiency virus (HIV). Expression of a single siRNA species frequently led to the emergence of HIV escape variants. Thus, multiple siRNAs targeted to different regions in the HIV-1 genome may be required. However, overexpression of different anti-HIV siRNA genes from multiple pol III promoters can induce cell toxicity, thus may not be a viable option in the setting of human gene therapy trials. In the current study, we evaluated the strategy of using pol II promoters to drive the expression of siRNAs against HIV-1. We replaced the stem sequence in the stem-loop structure of the well-characterized miR-30a with siRNA sequences and showed that designed microRNA (miRNA) could be expressed from pol II promoters. We demonstrated efficient inhibition of HIV-1 replication with such designed miRNA, but the efficacy was directly correlated with the expression level. Both the vector copy number and the promoter strength directly affected the ability of the siRNA to inhibit HIV-1 replication. We also showed that a combination of pol II and pol III promoters to express two different siRNAs increased the efficacy against HIV-1 replication without comprising cell viability.

Functional comparison of T cells recognizing cytomegalovirus pp65 and intermediate-early antigen polypeptides in hematopoietic stem-cell transplant and solid organ transplant recipients

The functional status of cytotoxic T lymphocyte (CTL) populations recognizing cytomegalovirus intermediate-early antigen (IE1) and pp65 polypeptides was investigated in peripheral blood mononuclear cells from hematopoietic stem-cell transplant (HSCT) and solid organ transplant recipients. Combined flow-based CD107a/b degranulation/mobilization and intracellular cytokine (ICC) assays using peptide libraries as antigens indicated that a significantly higher proportion of pp65-specific CTLs were in a more mature functional state, compared with IE1-specific CTLs. Degranulation/multiple cytokine ICC assays also indicated that a significantly higher proportion of pp65-specific than IE1-specific CTLs secreted both interferon- gamma and tumor necrosis factor- alpha and possessed greater cytotoxic potential. These results support our earlier findings of functional differences between CTLs recognizing individual epitopes within the IE1 and pp65 antigens in healthy donors and HSCT recipients and extend them to a broader array of human leukocyte antigen-restricted responses to those antigens. We also provide evidence of a relationship between cytotoxic function and the ability of cytomegalovirus-specific CTLs to secrete multiple cytokines.

Ex Vivo Selection and Expansion of Cells Based on Expression of a Mutated Inosine Monophosphate Dehydrogenase 2 after HIV Vector Transduction: Effects on Lymphocytes, Monocytes, and CD34+ Stem Cells

Hematopoietic progenitor cells (HPCs) represent an ideal target for gene therapy treatment of human immunodeficiency virus (HIV) infection. However, gene delivery into quiescent HPCs by retroviral or lentiviral vectors remains relatively poor. We evaluated a selection scheme based on the expression of a variant of inosine monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme in the de novo purine biosynthesis pathway. As lymphocytes depend more than other cell types on de novo synthesis of purines, IMPDH inhibitors such as mycophenolic acid (MPA) can selectively expand lymphocytes overexpressing the enzymes. We used HIV vectors to deliver an IMPDH variant into T cells and HPCs. We showed that the transduced T cells became resistant to MPA selection. By expressing a short hairpin RNA gene targeted to the HIV gag transcript, the MPA-selected T cells became resistant to HIV-1 infection. Monocyte/macrophages derived from the transduced HPCs differentiated normally and exhibited normal function as measured by B7 up-regulation and phagocytosis when stimulated. Our results suggest that this system may be applicable as a selection strategy to enrich transduced T lymphocytes and mononuclear cells in vivo for HIV gene therapy.

Cytomegalovirus immune reconstitution occurs in recipients of allogeneic hematopoietic cell transplants irrespective of detectable cytomegalovirus infection

The question of when immune reconstitution of cytomegalovirus (CMV)-specific CD8 T cells occurs after hematopoietic cell transplantation and, more specifically, to which CMV targets this immunity is likely to be directed remains poorly understood. The dependence of immune reconstitution on CMV reactivation is even less clear. To better understand these events, 44 CMV-seropositive HLA-A*0201 subjects were followed up at approximately days 40, 90, 120, 150, 180, and 360 after hematopoietic cell transplantation for CMV immunity as measured by 2 types of assays: (1) an HLA-A*0201 tetramer-binding assay for both CMV pp65 (pp65) and immediate-early 1 (IE-1) or (2) intracellular cytokine interferon gamma responses induced by pp65 or IE-1-derived peptides. To verify the reliability of IE-1-specific assays relative to the pp65-based assays, a pilot study first compared the development of IE-1-specific immunity in a subgroup by using multiple HLA-A*0201-restricted peptides, and then these recipients were followed up for 1 year for immunologic function and for CMV infection. The IE-1-specific response occurred to each of the 3 HLA-A*0201-restricted peptides studied (IE-1-256, -297, and -316), and there was no predominant IE peptide response. However, the immunodominant HLA-A*0201-restricted pp65 peptide was recognized significantly more frequently than these IE-1 peptides. When this was compared with the occurrence of CMV infection, the overall immune reactivity, as measured by the mean or median number of CD8+ T cells reactive to either pp65 or IE-1 peptides by intracellular cytokine or tetramer binding assay, was not significantly different in those with and without CMV infection. For patients who demonstrated reconstituted immunity to CMV at 1 year, all were reconstituted by 6 months, and the timing of the first observed immune reactivity to either of the pp65 or the IE peptides was not different in those with and without detectable CMV infection.

Current status of gene therapy strategies to treat HIV/AIDS

Progress in developing effective gene transfer approaches to treat HIV-1 infection has been steady. Many different transgenes have been reported to inhibit HIV-1 in vitro. However, effective translation of such results to clinical practice, or even to animal models of AIDS, has been challenging. Among the reasons for this failure are uncertainty as to the most effective cell population(s) to target, the diffuseness of these target cells in the body, and ineffective or insufficiently durable gene delivery. Better understanding of the HIV-1 replicative cycle, host factors involved in HIV-1 infection, vector biology and application, transgene technology, animal models, and clinical study design have all contributed vastly to planning current and future strategies for application of gene therapeutic approaches to the treatment of AIDS. This review focuses on the newest developments in these areas and provides a strong basis for renewed optimism that gene therapy will have an important role to play in treating people infected with HIV-1.

Lack of association of cytomegalovirus with human brain tumors

Cytomegalovirus (CMV) is thought to possess oncogenic properties and has been linked with a number of human malignancies. CMV infection was recently described in association with malignant gliomas. The intent of the present study was to further investigate the reported association between CMV and malignant gliomas. Tissue from 22 brain tumors of various histologic types and grades, four normal brains, six breast carcinomas, six colon carcinomas, six lung carcinomas, and six sarcomas were evaluated for the presence of CMV by polymerase chain reaction (PCR), in situ hybridization, and immunohistochemical methods. None of the brain tumors or normal brain tissue tested demonstrated evidence of CMV pp65 or early nuclear proteins by immunohistochemistry. In addition, no CMV RNA or DNA was detected in these cases by in situ hybridization and PCR. None of the carcinomas or sarcomas evaluated were positive for CMV by immunohistochemistry, in situ hybridization, or PCR. The findings of the present study suggest that CMV is not significantly associated with brain tumors in humans.

Assessment of cellular immunity to human cytomegalovirus in recipients of allogeneic stem cell transplants

Effective reconstitution of cellular immunity following hematopoietic stem cell transplantation (HCT) is thought to be important for protection from the morbidity caused by cytomegalovirus (CMV) reactivation and disease. This review critically discusses current methods for assessment of CMV-specific cellular immune responses, with emphasis on flow cytometry-based methodologies such as MHC-I and MHC-II tetramer staining and intracellular cytokine assays. The advantages and weaknesses of these assays are considered in comparison to traditional immunologic techniques. Application of these newer methodologies has provided insight into the dynamics of the levels of CMV-specific CD4(+) and CD8(+) T-lymphocytes following HCT, and into the sources and diversity of these cells. Data from preliminary clinical studies suggest that CMV-specific CD8(+) T-lymphocyte levels greater than 1 x 10(7)/L of peripheral blood may correlate with protection from CMV disease. Studies on the functional phenotypes of CMV-specific CD8(+) T-lymphocytes such as cytokine production, degranulation, and cytotoxicity have indicated that these cells are heterogeneous with regard to these properties. Future research will focus on establishing whether any of these immunologic assays will serve as a correlate of protection and inform as to which patients are at high risk for CMV reactivation and disease. Identification of an informative assay may allow its incorporation into standard clinical practice for monitoring HCT patients.

DNA and low titer, helper-free, recombinant AAV prime-boost vaccination for cytomegalovirus induces an immune response to CMV-pp65 and CMV-IE1 in transgenic HLA A*0201 mice

A prime-boost immunization regimen allowed the use of low titer, helper-free rAAV-pp65mII and rAAV-IE1 virus to elicit specific humoral and cellular responses to two important cytomegalovirus (CMV) antigens: the immediate-early 1 (IE-1) and pp65 proteins. Simultaneous immunization of both CMV proteins, using DNA vaccine priming followed by rAAV boost, induced antibody (Ab) response, CD8 lymphocytes with cytotoxic function, and detectible binding of the cognate peptide epitopes for human HLA A*0201 restriction using tetramer technology.

Simultaneous reconstitution of multiple cytomegalovirus-specific CD8+ cell populations with divergent functionality in hematopoietic stem-cell transplant recipients

A panel of 7 human cytomegalovirus (CMV) epitope peptides and corresponding major histocompatibility class 1 tetramers was used to evaluate cellular immunity in healthy seropositive donors and in hematopoietic stem-cell transplant recipients. Broad CMV-specific T cell responses to epitopes were found within several CMV polypeptides and were restricted by multiple human leukocyte antigen alleles. Their cytotoxic functionality was evaluated by use of an assay that measures transient surface levels of lysosomal membrane proteins LAMP-1 (CD107a) and LAMP-2 (CD107b) after peptide stimulation. This assay can be combined with tetramer staining of antigen-specific CD8(+) T lymphocytes and has potential as a surrogate marker for cytotoxic function. CD8(+) T lymphocytes specific for epitopes within the pp65 or pp50 gene products exhibited significantly higher functionality, compared with populations recognizing CMV major immediate early-1 epitopes. These functional differences between T lymphocyte populations within the same individual may have implications for protection against CMV.

RNA-mediated inhibition of HIV in a gene therapy setting

At present, treatment for HIV-1 infection employs highly active anti-retroviral therapy (HAART), which utilizes a combination of RT and protease inhibitors. Unfortunately, HIV can escape many therapies because of its high mutation rate and the complexity of its pathogenesis. HIV-1 integrates into the cellular genome, which facilitates persistence and acts as a reservoir for reactivation and replication. As an alternative or adjuvant to chemotherapy we have been developing an RNA-based gene therapy approach for the treatment of HIV-1 infection. This article summarizes the various RNA based technologies that we have developed for potential application in a gene therapy setting.