New approaches for monitoring CTL activity in clinical trials

CD8+T-cell response to mutated HLA-B*35-restricted Gag HY9 and HA9 epitopes from HIV-1 variants from Medellin, Colombia

The HLA-B*35 alleles have been associated with a slow or rapid progression of HIV-1 infection. However, the mechanisms related to HIV-1 progression have yet to be entirely understood. Several reports indicate that the binding affinity between the HLA-I molecule and peptides could be associated with an increased CD8+ T-cell response. Novel HLA-B*35-restricted mutated variants have been described from HSNQVSQNY (HY9) and HPVHAGPIA (HA9) epitopes. Bioinformatic analysis has indicated that these mutated epitopes show low and high binding affinity towards HLA-B*35, respectively. However, the polyfunctionality of CD8+ T-cells stimulated with these mutated and wild-type epitopes has yet to be reported. The results suggest that the low-binding affinity H124 N/S125 N/N126S mutated peptide in the HY9 epitope induced a lower percentage of CD107a+CD8+ T-cells than the wild-type epitope. Instead, the high-binding affinity peptides I223V and I223A in the HA9 epitope induced a significantly higher frequency of polyfunctional CD8+ T-cells. Also, a higher proportion of CD8+ T-cells with two functions, with Granzyme B+ Perforin+ being the predominant profile, was observed after stimulation with mutated peptides associated with high binding affinity in the HA9 epitope. These results suggest that the high-affinity mutated peptides induced a more polyfunctional CD8+ T-cell response, which could be related to the control of viral replication.

IFNβ-induced exosomal linc-EPHA6-1 promotes cytotoxicity of NK cells by acting as a ceRNA for hsa-miR-4485-5p to up-regulate NKp46 expression

AIMS

Exosomes contain functional molecules from their cells of origin and can enter recipient cells for intercellular communication. Interferon β (IFNβ) has been shown to induce some lncRNAs to regulate host immune response and play a major role in the positive regulation of the activity of natural killer (NK) cells. We aim to clarify whether IFNβ induced exosomes can regulate the cytotoxicity of NK cells by transferring specific lncRNAs into NK cells.

MAIN METHODS

Exosomes were isolated from the supernatants of A549 cells with or without IFNβ treatment. Co-culture and ELISA assay were used to analyze the effect of exosomes on the cytotoxicity of NK cells. Human transcriptome array (HTA) was performed to analyze the profiling of RNAs wrapped in exosomes. Then subcellular location, qPCR, western blotting, dual-luciferase reporter assay and ELISA were used to determine long noncoding RNAs (lcnRNAs) location, sponge absorb effects, the expression of NKp46 and cytotoxicity of NK cells.

KEY FINDINGS

ELISA assay showed IFNβ induced exosomes can strengthen the cytotoxicity of NK cells. Through HTA we found the expression levels of 69 lncRNAs were significantly changed within IFNβ induced exosomes. Additionally, we found a specific exosomal cargo, linc-EPHA6-1, acted as a competing endogenous RNA (ceRNA) for hsa-miR-4485-5p which subsequently up-regulate one of the natural cytotoxicity receptors (NKp46) expression. Furthermore, we verified over-expression of linc-EPHA6-1 significantly enhances the cytotoxicity of NK cells against A549 cells and Zika virus infected A549 cells.

SIGNIFICANCE

Our results demonstrated that IFNβ-induced exosomal linc-EPHA6-1 can regulate the cytotoxicity of NK cells.

Cell-Mediated Immunity Generated in Response to a Purified Inactivated Vaccine for Dengue Virus Type 1

Dengue is a tropical disease transmitted by mosquitoes, and nearly half of the world’s population lives in areas where individuals are at risk of infection. Several vaccines for dengue are in development, including one which was recently licensed in several countries, although its utility is limited to people who have already been infected with one of the four dengue viruses. One major hurdle to understanding whether a dengue vaccine will work for everyone—before exposure—is the necessity of knowing which marker can be measured in the blood to signal that the individual has protective immunity. This report describes an approach measuring multiple different parts of immunity in order to characterize which signals one candidate vaccine imparted to a small number of human volunteers. This approach was designed to be able to be applied to any dengue vaccine study so that the data can be compared and used to inform future vaccine design and/or optimization strategies.

Dengue is the most prevalent arboviral disease afflicting humans, and a vaccine appears to be the most rational means of control. Dengue vaccine development is in a critical phase, with the first vaccine licensed in some countries where dengue is endemic but demonstrating insufficient efficacy in immunologically naive populations. Since virus-neutralizing antibodies do not invariably correlate with vaccine efficacy, other markers that may predict protection, including cell-mediated immunity, are urgently needed. Previously, the Walter Reed Army Institute of Research developed a monovalent purified inactivated virus (PIV) vaccine candidate against dengue virus serotype 1 (DENV-1) adjuvanted with alum. The PIV vaccine was safe and immunogenic in a phase I dose escalation trial in healthy, flavivirus-naive adults in the United States. From that trial, peripheral blood mononuclear cells obtained at various time points pre- and postvaccination were used to measure DENV-1-specific T cell responses. After vaccination, a predominant CD4⁺ T cell-mediated response to peptide pools covering the DENV-1 structural proteins was observed. Over half (13/20) of the subjects produced interleukin-2 (IL-2) in response to DENV peptides, and the majority (17/20) demonstrated peptide-specific CD4⁺ T cell proliferation. In addition, analysis of postvaccination cell culture supernatants demonstrated an increased rate of production of cytokines, including gamma interferon (IFN-γ), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Overall, the vaccine was found to have elicited DENV-specific CD4⁺ T cell responses as measured by enzyme-linked immunosorbent spot (ELISpot), intracellular cytokine staining (ICS), lymphocyte proliferation, and cytokine production assays. Thus, together with antibody readouts, the use of a multifaceted measurement of cell-mediated immune responses after vaccination is a useful strategy for more comprehensively characterizing immunity generated by dengue vaccines.

IMPORTANCE Dengue is a tropical disease transmitted by mosquitoes, and nearly half of the world’s population lives in areas where individuals are at risk of infection. Several vaccines for dengue are in development, including one which was recently licensed in several countries, although its utility is limited to people who have already been infected with one of the four dengue viruses. One major hurdle to understanding whether a dengue vaccine will work for everyone—before exposure—is the necessity of knowing which marker can be measured in the blood to signal that the individual has protective immunity. This report describes an approach measuring multiple different parts of immunity in order to characterize which signals one candidate vaccine imparted to a small number of human volunteers. This approach was designed to be able to be applied to any dengue vaccine study so that the data can be compared and used to inform future vaccine design and/or optimization strategies.

In vitro immunotherapy potency assays using real-time cell analysis

A growing understanding of the molecular interactions between immune effector cells and target tumor cells, coupled with refined gene therapy approaches, are giving rise to novel cancer immunotherapeutics with remarkable efficacy in the clinic against both solid and liquid tumors. While immunotherapy holds tremendous promise for treatment of certain cancers, significant challenges remain in the clinical translation to many other types of cancers and also in minimizing adverse effects. Therefore, there is an urgent need for functional potency assays, in vitro and in vivo, that could model the complex interaction of immune cells with tumor cells and can be used to rapidly test the efficacy of different immunotherapy approaches, whether it is small molecule, biologics, cell therapies or combinations thereof. Herein we report the development of an xCELLigence real-time cytolytic in vitro potency assay that uses cellular impedance to continuously monitor the viability of target tumor cells while they are being subjected to different types of treatments. Specialized microtiter plates containing integrated gold microelectrodes enable the number, size, and surface attachment strength of adherent target tumor cells to be selectively monitored within a heterogeneous mixture that includes effector cells, antibodies, small molecules, etc. Through surface-tethering approach, the killing of liquid cancers can also be monitored. Using NK92 effector cells as example, results from RTCA potency assay are very well correlated with end point data from image-based assays as well as flow cytometry. Several effector cells, i.e., PBMC, NK, CAR-T were tested and validated as well as biological molecules such as Bi-specific T cell Engagers (BiTEs) targeting the EpCAM protein expressed on tumor cells and blocking antibodies against the immune checkpoint inhibitor PD-1. Using the specifically designed xCELLigence immunotherapy software, quantitative parameters such as KT₅₀ (the amount of time it takes to kill 50% of the target tumor cells) and % cytolysis are calculated and used for comparing the relative efficacy of different reagents. In summary, our results demonstrate the xCELLigence platform to be well suited for potency assays, providing quantitative assessment with high reproducibility and a greatly simplified work flow.

Augmentation of cellular and humoral immune responses to HPV16 and HPV18 E6 and E7 antigens by VGX-3100

We have previously demonstrated the immunogenicity of VGX-3100, a multicomponent DNA immunotherapy for the treatment of Human Papillomavirus (HPV)16/18-positive CIN2/3 in a phase 1 clinical trial. Here, we report on the ability to boost immune responses with an additional dose of VGX-3100. Patients completing our initial phase 1 trial were offered enrollment into a follow on trial consisting of a single boost dose of VGX-3100. Data show both cellular and humoral immune responses could be augmented above pre-boost levels, including the induction of interferon (IFN)γ production, tumor necrosis factor (TNF)α production, CD8+ T cell activation and the synthesis of lytic proteins. Moreover, observation of antigen-specific regulation of immune-related gene transcripts suggests the induction of a proinflammatory response following the boost. Analysis of T cell receptor (TCR) sequencing suggests the localization of putative HPV-specific T cell clones to the cervical mucosa, which underscores the putative mechanism of action of lesion regression and HPV16/18 elimination noted in our double-blind placebo-controlled phase 2B trial. Taken together, these data indicate that VGX-3100 drives the induction of robust cellular and humoral immune responses that can be augmented by a fourth "booster" dose. These data could be important in the scope of increasing the clinical efficacy rate of VGX-3100.

Synthetic consensus HIV-1 DNA induces potent cellular immune responses and synthesis of granzyme B, perforin in HIV infected individuals

This study evaluated the safety and immunogenicity of PENNVAX-B in 12 HIV infected individuals. PENNVAX-B is a combination of three optimized synthetic plasmids encoding for multiclade HIV Gag and Pol and a consensus CladeB Env delivered by electroporation. HIV infected individuals whose virus was effectively suppressed using highly active antiretroviral therapy (HAART) received PENNVAX-B DNA followed by electroporation with CELLECTRA-5P at study weeks 0, 4, 8, and 16. Local administration site and systemic reactions to PENNVAX-B were recorded after each treatment along with any adverse events. Pain of the treatment procedure was assessed using a Visual Analog Scale. Whole PBMCs were isolated for use in IFN ELISpot and Flow Cytometric assays. PENNVAX-B was generally safe and well tolerated. Overall, the four dose regimen was not associated with any serious adverse events or severe local or systemic reactions. A rise in antigen-specific SFU was detected in the INFγ ELISpot assay in all 12 participants. T cells from 8/12 participants loaded with both granzyme B and perforin in response to HIV antigen, an immune finding characteristic of long-term nonprogressors (LTNPs) and elite controllers (ECs). Thus administration of PENNVAX-B may prove useful adjunctive therapy to ART for treatment and control of HIV infection.

Enumeration and characterization of human memory T cells by enzyme-linked immunospot assays

The enzyme-linked immunospot (ELISPOT) assay has advanced into a useful and widely applicable tool for the evaluation of T-cell responses in both humans and animal models of diseases and/or vaccine candidates. Using synthetic peptides (either individually or as overlapping peptide mixtures) or whole antigens, total lymphocyte or isolated T-cell subset responses can be assessed either after short-term stimulation (standard ELISPOT) or after their expansion during a 10-day culture (cultured ELISPOT). Both assays detect different antigen-specific immune responses allowing the analysis of effector memory T cells and central memory T cells. This paper describes the principle of ELISPOT assays and discusses their application in the evaluation of immune correlates of clinical interest with a focus on the vaccine field.

Quantifying biomass changes of single CD8+ T cells during antigen specific cytotoxicity

Existing approaches that quantify cytotoxic T cell responses rely on bulk or surrogate measurements which impede the direct identification of single activated T cells of interest. Single cell microscopy or flow cytometry methodologies typically rely on fluorescent labeling, which limits applicability to primary cells such as human derived T lymphocytes. Here, we introduce a quantitative method to track single T lymphocyte mediated cytotoxic events within a mixed population of cells using live cell interferometry (LCI), a label-free microscopy technique that maintains cell viability. LCI quantifies the mass distribution within individual cells by measuring the phase shift caused by the interaction of light with intracellular biomass. Using LCI, we imaged cytotoxic T cells killing cognate target cells. In addition to a characteristic target cell mass decrease of 20–60% over 1–4 h following attack by a T cell, there was a significant 4-fold increase in T cell mass accumulation rate at the start of the cytotoxic event and a 2–3 fold increase in T cell mass relative to the mass of unresponsive T cells. Direct, label-free measurement of CD8+ T and target cell mass changes provides a kinetic, quantitative assessment of T cell activation and a relatively rapid approach to identify specific, activated patient-derived T cells for applications in cancer immunotherapy.

Immunotherapy against HPV16/18 generates potent TH1 and cytotoxic cellular immune responses

Despite the development of highly effective prophylactic vaccines against human papillomavirus (HPV) serotypes 16 and 18, prevention of cervical dysplasia and cancer in women infected with high-risk HPV serotypes remains an unmet medical need. We report encouraging phase 1 safety, tolerability, and immunogenicity results for a therapeutic HPV16/18 candidate vaccine, VGX-3100, delivered by in vivo electroporation (EP). Eighteen women previously treated for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3) received a three-dose (intramuscular) regimen of highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens followed by EP in a dose escalation study (0.3, 1, and 3 mg per plasmid). Immunization was well tolerated with reports of mild injection site reactions and no study-related serious or grade 3 and 4 adverse events. No dose-limiting toxicity was noted, and pain was assessed by visual analog scale, with average scores decreasing from 6.2/10 to 1.4 within 10 min. Average peak interferon-γ enzyme-linked immunospot magnitudes were highest in the 3 mg cohort in comparison to the 0.3 and 1 mg cohorts, suggesting a trend toward a dose effect. Flow cytometric analysis revealed the induction of HPV-specific CD8(+) T cells that efficiently loaded granzyme B and perforin and exhibited full cytolytic functionality in all cohorts. These data indicate that VGX-3100 is capable of driving robust immune responses to antigens from high-risk HPV serotypes and could contribute to elimination of HPV-infected cells and subsequent regression of the dysplastic process.

Enhanced anti-cancer activity of human dendritic cells sensitized with gamma-irradiation-induced apoptotic colon cancer cells

Properly sensitized dendritic cells (DCs) can be an effective immunotherapeutic against cancers. We investigated the phenotypic and functional changes in human DCs sensitized with γ-irradiated colon cancer cell-line HT-29 (GIH). GIH induced maturation and activation of DCs. GIH-sensitized DCs showed increased cytotoxic activity against HT-29 through higher expression of perforin and granzyme B. They further induced expression of effector cytokines, cytotoxic molecules, and mucosal-homing receptor in autologous T-cells. Conclusively, these results suggest that effective anti-cancer activity is induced when DCs are sensitized with γ-irradiated cancer cells via both direct augmentation of the cytotoxicity and indirect activation of T cells.

Immune markers and correlates of protection for vaccine induced immune responses

Vaccines have been a major innovation in the history of mankind and still have the potential to address the challenges posed by chronic intracellular infections including tuberculosis, HIV and malaria which are leading causes of high morbidity and mortality across the world. Markers of an appropriate humoral response currently remain the best validated correlates of protective immunity after vaccination. Despite advancements in the field of immunology over the past few decades currently there are, however, no sufficiently validated immune correlates of vaccine induced protection against chronic infections in neither human nor veterinary medicine. Technological and conceptual advancements within cell-mediated immunology have led to a number of new immunological read-outs with the potential to emerge as correlates of vaccine induced protection. For T(H)1 type responses, antigen-specific production of interferon-gamma (IFN-γ) has been promoted as a quantitative marker of protective cell-mediated immune responses over the past couple of decades. More recently, however, evidence from several infections has pointed towards the quality of the immune response, measured through increased levels of antigen-specific polyfunctional T cells capable of producing a triad of relevant cytokines, as a better correlate of sustained protective immunity against this type of infections. Also the possibilities to measure antigen-specific cytotoxic T cells (CTL) during infection or in response to vaccination, through recombinant major histocompatibility complex (MHC) class I tetramers loaded with relevant peptides, has opened a new vista to include CTL responses in the evaluation of protective immune responses. Here, we review different immune markers and new candidates for correlates of a protective vaccine induced immune response against chronic infections and how successful they have been in defining the protective immunity in human and veterinary medicine.

Simultaneous Detection of Antigen-Specific IgG- and IgM-Secreting Cells with a B Cell Fluorospot Assay

The traditional enzyme-linked immunospot (ELISpot) assay is the gold standard for the enumeration of antigen-specific B cells. Since B cell availability from biological samples is often limited, either because of sample size/volume or the need of performing multiple analyses on the same sample, the implementation of ELISpot assay formats that allow the simultaneous detection of multiple antibody types is desirable. While dual-color ELISpot assays have been described, technical complexities have so far prevented their wide utilization as well as further expansion of their multicolor capability. An attractive solution is to replace the chromogenic reaction of the traditional ELISpot assay with a fluorescent detection system (fluorospot assay). Fluorospot assays using fluorophore-conjugated secondary antibodies in conjunction with fluorescence enhancers, FITC/anti-FITC and biotin/avidin amplification systems and dedicated equipment for spot detection have been developed to enumerate T-cells secreting two or three specific cytokines and, more recently, IgG and IgA antibody-secreting cells (ASCs). We hereby report a method for a multiplex B cell fluorospot assay that utilizes quantum-dot nanocrystals as reporters without further amplification systems or need of dedicated equipment. With this method we simultaneously enumerated HIV-1 gp41 envelope glycoprotein-specific IgG and IgM antibody-secreting cells with sensitivity comparable to that of the traditional ELISpot assay.

Evaluation of antigen specific recognition and cell mediated cytotoxicity by a modified lysispot assay in a rat colon carcinoma model

Background

Antigen-specific CD8+ cytotoxic T lymphocytes represent potent effector cells of the adaptive immune response against viruses as well as tumours. Therefore assays capable at exploring the generation and function of cytotoxic T lymphocytes represent an important objective for both clinical and experimental settings.

Methods

Here we show a simple and reproducible assay for the evaluation of antigen-specific CD8+ cytotoxic T lymphocytes based on a LysiSpot technique for the simultaneous determination of antigen-specific IFN-γ production and assessment of tumor cytolysis. The assay was developed within an experimental model of colorectal carcinoma, induced by the colorectal tumor cell line DHD-K12 that induces tumors in BDIX rats and, in turn, elicits a tumor- specific immune response.

Results

Using DHD-K12 cells transfected to express Escherichia coli β-galactosidase as target cells, and by the fine setting of spot colours detection, we have developed an in vitro assay that allows the recognition of cytotoxic T lymphocytes induced in BDIX rats as well as the assessment of anti-tumour cytotoxicity. The method highlighted that in the present experimental model the tumour antigen-specific immune response was bound to killing target cells in the proportion of 55%, while 45% of activated cells were not cytotoxic but released IFN-γ. Moreover in this model by an ELISPOT assay we demonstrated the specific recognition of a nonapeptide epitope called CSH-275 constitutionally express in DHD-K12 cells.

Conclusions

The assay proved to be highly sensitive and specific, detecting even low frequencies of cytotoxic/activated cells and providing the evaluation of cytokine-expressing T cells as well as the extent of cytotoxicity against the target cells as independent functions. This assay may represent an important tool to be adopted in experimental settings including the development of vaccines or immune therapeutic strategies

Immunological monitoring of the tumor immunoenvironment for clinical trials

Monitoring of immunotherapeutic clinical trials has undergone a considerable change in the last decade resulting in a general agreement that immune monitoring should guide the development of cancer vaccines. The emphasis on immune cell functions and quantitation of antigen-specific T cells have been playing a major role in the attempts to establish meaningful correlations between therapy-induced alterations in immune responses and clinical endpoints. However, one significant unresolved issue in modern immunotherapy is that when a tumor-specific cellular immune response is observed following the course of immunotherapy, it does not always lead to clinically proven cancer regression. This disappointing lack of a correlation between the tumor-specific cytotoxic immune responses and the clinical efficacy of immunotherapy may be explained, among other reasons, by the notion that the analysis of any single immunological parameter is not sufficient to provide clinically feasible information about the complex interactions between different cell subsets in the peripheral blood and immune, tumor, and stromal cells in the tumor milieu. By contrast, a systemic approach is required for improving the quality of a serial monitoring to ensure that it adequately and reliably measures potential changes induced in patients by administered vaccines or immunomodulators. Comprehensive evaluation of the balance between the immunostimulatory and immunosuppressive compartments of the immune system could be critical for a better understanding of how a given immunotherapy works or does not work in a particular clinical trial. New approaches to characterize tumor-infiltrating leukocytes, their phenotypic, biochemical, and genetic characteristics within the tumor microenvironment need to be developed and validated and should complement current monitoring techniques. These immune-monitoring assays for the local tumor immunoenvironment should be developed, validated, and standardized for reliability and consistency in order to establish the overall performance standards.

Evaluation of a robotic system for the recovery of peripheral blood mononuclear cells

Investigations into immune responses are often based upon recovery of peripheral blood mononuclear cells (PBMC). To this purpose, the recovery of PBMC by gradient centrifugation is labour-intensive and requires a reasonable level of skill by the laboratory technician. Thus, we set out to determine whether laboratory automation equipment could be used for the recovery of PBMC from blood samples of horses, pigs and cattle, based on the Ficoll-Paque gradient centrifugation technique. Mixing of blood samples with PBS, layering of diluted blood onto Ficoll-Paque gradients, recovery of separated PBMC in RPMI 1640 medium were performed using an automated robotic system, the SBF200 (AM Robotic Systems, Warrington, UK) under laminar air flow conditions. Tubes were tagged with bar codes and manually placed after gradient centrifugation into a tube reader to measure the volume and position of the PBMC layer. The results of the automated procedure compared very well to those of the manual one in terms of percent cell recovery, sterility and cell viability. Also, a high throughput of samples could be implemented: with the integration of cell counting it should be possible for 96 blood samples to be processed, including the production of aliquots, by one person in a day.

Active and passive immunotherapy for lymphoma: proving principles and improving results

Conventional chemotherapy for lymphoma has advanced greatly over the past 50 years, changing some lymphoma subtypes from uniformly lethal to curable; however, the majority of lymphomas in patients remain incurable, and there is a need for novel therapies with less toxicity and more specific targeting of tumor cells. The vertebrate immune system has evolved the capacity for such specific targeting through the B-cell and T-cell receptors; passive immunotherapies utilizing these receptors, such as monoclonal antibodies (mAbs) or T cells, have shown efficacy in treating lymphomas. The first generation of mAb-based therapies has transformed the standard of care for lymphoma, and newer antibodies may improve on this approach. Clinical activity has been shown by T cells bearing receptors that target viral antigens as well as T cells bearing re-engineered receptors that target antigens recognized by antibodies. Active immunotherapies, such as vaccines and immune checkpoint blockades, have prolonged survival in certain solid tumors and are being actively pursued to treat lymphoma. A variety of vaccines (eg, protein- and cell-based vaccines) are being tested in ongoing trials, and the most recent iterations show therapeutic activity. Newer trials are addressing the problem of tumor-induced immunosuppression by the use of antibodies against immunologic checkpoints or by the reinfusion of primed T cells after lymphodepletion, a process we refer to as immunotransplantation. Herein, we discuss results of the various immunotherapy strategies applied to lymphoma and the ongoing approaches for their improvement.

A flow cytometry-based assay to assess minute frequencies of CD8+ T cells by their cytolytic function

Limited sample size and low sensitivity of currently used functional assays challenge direct analysis of cytotoxic CD8+ T lymphocyte activity to quantify antigen-specific immunity after infection or vaccination. Our flow cytometry-based assay reproducibly detects at least three epitope-specific CD8+ T lymphocytes by their cytolytic function. As exemplified for viral epitopes restricted to the human leukocyte antigen (HLA)-A2, the HLA-A2+ human somatic cell hybrid T2 provided an about 10-fold more sensitive readout as compared to autologous B-lymphoblastoid cells or the human erythroleukemia cell line K562 transfected to express HLA-A2 when used as target cells. We named our assay VITAL-FR assay, referring to Hermans et al. (2004) and indicating the modification of using Far Red (FR) dye instead of CMTMR. Under optimal conditions the VITAL-FR assay proved 30 times more sensitive than the 51chromium-release assay to assess epitope-specific target cell lysis. The high overall sensitivity of the VITAL-FR assay basically depended on the negligible spectral overlap of the emission of a stable Far Red fluorescent reporter with the green tracer for target cell labelling. It also profited from long co-incubation of effector and target cells of up to 72, from prior in-vitro culture increasing the frequency of epitope-specific CD8+ T cells and from generic, easily accessible standardized target cells that were used with only 10(3) specific and 10(3) control target cells per individual experimental reaction. Our functional approach with the VITAL-FR assay therefore ideally suits for monitoring CD8+ T cell-mediated cytotoxicity in e.g. vaccination studies with known MHC-restricted immunogenic peptides in scientific and diagnostic applications.

Lymphoma immunotherapy: vaccines, adoptive cell transfer and immunotransplant

Therapy for non-Hodgkin lymphoma has benefited greatly from basic science and clinical research such that chemotherapy and monoclonal antibody therapy have changed some lymphoma subtypes from uniformly lethal to curable, but the majority of lymphoma patients remain incurable. Novel therapies with less toxicity and more specific targeting of tumor cells are needed and immunotherapy is among the most promising of these. Recently completed randomized trials of idiotype vaccines and earlier-phase trials of other vaccine types have shown the ability to induce antitumor T cells and some clinical responses. More recently, trials of adoptive transfer of antitumor T cells have demonstrated techniques to increase the persistence and antitumor effect of these cells. Herein, we discuss lymphoma immunotherapy clinical trial results and what lessons can be taken to improve their effect, including the combination of vaccination and adoptive transfer in an approach we have dubbed 'immunotransplant'.

Genotypic variation and phenotypic characterization of granzyme B gene polymorphisms

BACKGROUND

Granzyme B has been associated with allograft rejection in solid organ transplantation. Single nucleotide polymorphisms (SNPs) in the granzyme B gene might impact its expression. The aims of this study were (1) to establish the frequency of two granzyme B SNPs (A-295G; Q-55R) in pediatric heart transplant (PHTx) recipients and (2) to determine their phenotypic expression in healthy individuals.

METHODS

Three hundred ninety-six PHTx patients (245 white non-Hispanic, 49 black non-Hispanic, 82 Hispanics, and 20 others) and 52 healthy controls were screened for Q-55R and A-295G. For the control samples, we assessed the frequency of granzyme B positive cells by ELISPOT assay after mitogen stimulation.

RESULTS

Among the PHTx recipients, 57% percent of the population carried the Q/Q genotype, whereas 6% were R/R homozygotes. Seven of 49 (14%) black non-Hispanics were R/R homozygotes, whereas 13 of 245 (5%) of white non-Hispanics and 5 of 82 (6%) Hispanics carried the R/R genotype (P=0.02). The A allele frequency of granzyme B A-295G (49.6%) was similar to that of the G allele (50.4%). However, 80% of Black non-Hispanics were A allele carriers compared with 68% of White non-Hispanics (P<0.0001). After mitogen stimulation, the frequency of granzyme B positive cells was higher in the Q/Q homozygotes compared with R/R carriers (P=0.006), whereas a similar frequency of granzyme B positive cells was noticed among the genotypes of A-295G SNP.

CONCLUSIONS

These data indicate that 55 Q/Q genotype is associated with increased in vitro expression of granzyme B.

Emerging concepts in biomarker discovery; the US-Japan Workshop on Immunological Molecular Markers in Oncology

Supported by the Office of International Affairs, National Cancer Institute (NCI), the "US-Japan Workshop on Immunological Biomarkers in Oncology" was held in March 2009. The workshop was related to a task force launched by the International Society for the Biological Therapy of Cancer (iSBTc) and the United States Food and Drug Administration (FDA) to identify strategies for biomarker discovery and validation in the field of biotherapy. The effort will culminate on October 28th 2009 in the "iSBTc-FDA-NCI Workshop on Prognostic and Predictive Immunologic Biomarkers in Cancer", which will be held in Washington DC in association with the Annual Meeting. The purposes of the US-Japan workshop were a) to discuss novel approaches to enhance the discovery of predictive and/or prognostic markers in cancer immunotherapy; b) to define the state of the science in biomarker discovery and validation. The participation of Japanese and US scientists provided the opportunity to identify shared or discordant themes across the distinct immune genetic background and the diverse prevalence of disease between the two Nations. Converging concepts were identified: enhanced knowledge of interferon-related pathways was found to be central to the understanding of immune-mediated tissue-specific destruction (TSD) of which tumor rejection is a representative facet. Although the expression of interferon-stimulated genes (ISGs) likely mediates the inflammatory process leading to tumor rejection, it is insufficient by itself and the associated mechanisms need to be identified. It is likely that adaptive immune responses play a broader role in tumor rejection than those strictly related to their antigen-specificity; likely, their primary role is to trigger an acute and tissue-specific inflammatory response at the tumor site that leads to rejection upon recruitment of additional innate and adaptive immune mechanisms. Other candidate systemic and/or tissue-specific biomarkers were recognized that might be added to the list of known entities applicable in immunotherapy trials. The need for a systematic approach to biomarker discovery that takes advantage of powerful high-throughput technologies was recognized; it was clear from the current state of the science that immunotherapy is still in a discovery phase and only a few of the current biomarkers warrant extensive validation. It was, finally, clear that, while current technologies have almost limitless potential, inadequate study design, limited standardization and cross-validation among laboratories and suboptimal comparability of data remain major road blocks. The institution of an interactive consortium for high throughput molecular monitoring of clinical trials with voluntary participation might provide cost-effective solutions.

The third dimension of ELISPOTs: quantifying antibody secretion from individual plasma cells

The enzyme-linked immunospot assay (ELISPOT) is a technique widely used to enumerate the number of immune cells secreting a specific protein, such as antibodies or cytokines. A limitation with the ELISPOT assay is that it can only be used to detect a single protein of interest. Recently, the ELISPOT technique has been modified to use fluorophores allowing multiple secreted proteins to be detected simultaneously. This technique has greatly enhanced the ability to identify cells secreting multiple proteins, but has not been used to its fullest potential. We wished to accurately quantify the expression of antigen-specific antibody from a single plasma cell and to determine whether plasma cells recovered from different locations had different secretion rates. To achieve this we analyzed fluorospot images quantitatively using Mira MX 7 UL Astronomy software, and coupled this data with a quantitative ELISA to determine secretion rates from individual cells. Using this technique we were able to determine that plasma cells recovered from the peripheral blood secreted the most antibody (1.667 ng/cell/12 h) while splenic antibody secreting cells the least (0.399 ng/cell/12 h). We were able to quantify a 150 fold difference in antibody secretion between cells, with most plasma cells divided into two groups, low secretors (<0.1 ng/cell) or high secretors (>2 ng/cell). We believe this technique will be particularly useful for examining the secretion ratio of two proteins secreted from an individual cell, allowing us to determine if secretion is fixed or variable.

In vitro end points for the assessment of cellular immune response-modulating drugs

BACKGROUND

The concept of immunotoxicology and the development of a battery of immune-function assays to screen potential immunotoxic compounds have been increasingly used in the past. Immunotoxic outcome generally seems appropriate to evaluate the risk in drug development. Improving this approach is possible, by using methods now available, to study the effect of a chemical compound on the immune system.

OBJECTIVE

The goal of this review is to provide an overview of the current and recent methodologies for testing the immunological effect and immunotoxic risks in drug candidates.

METHODS

The methodological details here discussed include a synthetic description of the immunocompetent cells in cell-mediated immunity and the choice of the most appropriate assay (bioassays, immunoassays, molecular biology techniques, flow cytometry).

CONCLUSION

This review offers an assessment of in vitro models to study the toxic impact of (bio)pharmaceuticals on cellular immune system and aid drug scientists in understanding the significance and the methods to approach immunotoxicology.

Induction of T-cell responses against cutaneous T-cell lymphomas ex vivo by autologous dendritic cells transfected with amplified tumor mRNA

Sézary syndrome (SzS), the leukemic variant of cutaneous T-cell lymphomas, is incurable. Dendritic cells (DCs) transfected with tumor mRNA can stimulate antitumor immunity in certain cancer patients. In this study, we determined whether mRNAs from Sézary cells could be used for loading DCs and stimulating antitumor immunity. Autologous DCs were generated from monocytes of the peripheral blood from 10 patients with SzS. Total RNA was extracted from Sézary cells and amplified by T7 in vitro transcription. The induction of antitumor IFN-gamma and granzyme B (GrB)-producing cytotoxic T lymphocytes (CTL) by RNA-transfected DCs was determined by ELISPOT assays. We found that IFN-gamma was required for IL-12p70 production by monocyte-derived DCs from SzS. The oncogenic transcription factor Twist and the tyrosine kinase receptor EphA4 were expressed in total RNA from Sézary cells and the paired amplified mRNAs. RNA-transfected DCs induced antitumor IFN-gamma-producing CTLs in 7 of 10 subjects and GrB-producing CTLs in 6 of 9 subjects. Both CD3+CD8+ T cells and CD4+CD25+ T cells were expanded without induction of regulatory T cells. These data support the concept of using tumor mRNA for a vaccine strategy that requires small amounts of tumor cells without need for specific antigens in patients with SzS.

Measuring cell death mediated by cytotoxic lymphocytes or their granule effector molecules

Cytotoxic lymphocytes (CL) are highly motile cells that utilize granule exocytosis to kill virus-infected or transformed targets. Isolated CL and purified granule proteins have been used to investigate the molecular processes that CL use to kill their targets and to investigate the basis of human disease. We have set out various methods that are routinely used to isolate CL and characterize the cell death pathways they induce. As cell death mediated through TNF-superfamily members and their respective receptors is covered elsewhere, this manuscript will deal specifically with cytotoxic granule-mediated cell death.