Identification of functional subsets by flow cytometry: intracellular detection of cytokine expression

Expression Profiles of Immune Cells after Propofol or Sevoflurane Anesthesia for Colorectal Cancer Surgery: A Prospective Double-blind Randomized Trial

BACKGROUND

The antitumor effects of natural killer cells, helper T cells, and cytotoxic T cells after cancer surgery were reported previously. This study hypothesized that propofol-based anesthesia would have fewer harmful effects on immune cells than volatile anesthetics-based anesthesia during colorectal cancer surgery.

METHODS

In total, 153 patients undergoing colorectal cancer surgery were randomized and included in the analysis. The primary outcome was the fraction of circulating natural killer cells over time in the propofol and sevoflurane groups. The fractions of circulating natural killer, type 1, type 17 helper T cells, and cytotoxic T cells were investigated. The fractions of CD39 and CD73 expressions on circulating regulatory T cells were investigated, along with the proportions of circulating neutrophils, lymphocytes, and monocytes.

RESULTS

The fraction of circulating natural killer cells was not significantly different between the propofol and sevoflurane groups until 24 h postoperatively (20.4 ± 13.4% vs. 20.8 ± 11.3%, 17.9 ± 12.7% vs. 20.7 ± 11.9%, and 18.6 ± 11.6% vs. 21.3 ± 10.8% before anesthesia and after 1 and 24 h after anesthesia, respectively; difference [95% CI], -0.3 [-4.3 to 3.6], -2.8 [-6.8 to 1.1], and -2.6 [-6.2 to 1.0]; P = 0.863, P = 0.136, and P = 0.151 before anesthesia and after 1 and 24 h, respectively). The fractions of circulating type 1 and type 17 helper T cells, cytotoxic T cells, and CD39+ and CD73+ circulating regulatory T cells were not significantly different between the two groups. The neutrophil to lymphocyte ratio in both groups remained within the normal range and was not different between the groups.

CONCLUSIONS

Propofol-based anesthesia was not superior to sevoflurane-based anesthesia in terms of alleviating suppression of immune cells including natural killer cells and T lymphocytes during colorectal cancer surgery.

EDITOR’S PERSPECTIVE

Extracellular allograft inflammatory factor-1 (AIF-1) potentiates Th1 cell differentiation and inhibits Treg response in human peripheral blood mononuclear cells from normal subjects

We identified the presence of AIF-1 (allograft inflammatory factor-1) in human peripheral blood mononuclear cells (PBMCs) from normal subjects by immunocytological methods. After isolation of different types of mononuclear cells by FACS (Fluorescence-activated cell sorting) with >95% purity, we studied the transcript levels of AIF-1 using qPCR. We observed the following order of AIF-1 mRNA expression in mononuclear cells: T-lymphocytes ˃ Monocytes ˃ B-lymphocytes ˃ NK. After T cell expansion of isolated PBMCs using anti-CD3-CD28 magnetic beads (Dynabeads®), AIF-1 increased intracellularly in the presence of brefeldin A; this finding, along with an increase in the medium in the absence of the drug, suggests that AIF-1 is processed in the Golgi apparatus and may be secreted extracellularly. In another set of experiments, interleukin-12 and anti-interleukin-4 were added to PBMCs during T cell expansion to promote Th1 polarization and to inhibit Th2 differentiation. In this case, the presence of 6 nM of rhAIF-1 (recombinant human AIF-1) increased the mRNA expression of interferon-ϒ and interleukin-2. In the same set of experiments, the incubation of PBMCs with rhAIF-1 (6 nM) promoted the decrease of mRNA expression of IL-10 and TGF-β, along with the decrease of CD25 and Foxp3 proteins. Furthermore, extracellular rhAIF-1 (6 nM) increased the survival of naive and effector T cells during Th1 polarization by inhibition of apoptosis, without causing changes in cell cycle rate and in retinoblastoma-cyclin-dependent kinase (Rb-CDK) activation. Taken together, rhAIF-1 treatment of PBMCs potentiates Th1 response and inhibits functionally suppressive CD25 + Foxp3 + Treg, which suggests an important immunomodulatory role in governing T cell response.

Modulation of tumor microenvironment for immunotherapy: focus on nanomaterial-based strategies

Recent advances in the field of immunotherapy have profoundly opened up the potential for improved cancer therapy and reduced side effects. However, the tumor microenvironment (TME) is highly immunosuppressive, therefore, clinical outcomes of currently available cancer immunotherapy are still poor. Recently, nanomaterial-based strategies have been developed to modulate the TME for robust immunotherapeutic responses. In this review, the immunoregulatory cell types (cells relating to the regulation of immune responses) inside the TME in terms of stimulatory and suppressive roles are described, and the technologies used to identify and quantify these cells are provided. In addition, recent examples of nanomaterial-based cancer immunotherapy are discussed, with particular emphasis on those designed to overcome barriers caused by the complexity and diversity of TME.

Single-Cell High-Throughput Technologies in Cerebrospinal Fluid Research and Diagnostics

High-throughput single-cell technologies have recently emerged as essential tools in biomedical research with great potential for clinical pathology when studying liquid and solid biopsies. We provide an update on current single-cell methods in cerebrospinal fluid research and diagnostics, focusing on high-throughput cell-type specific proteomic and genomic technologies. Proteomic methods comprising flow cytometry and mass cytometry as well as genomic approaches including immune cell repertoire and single-cell transcriptomic studies are critically reviewed and future directions discussed.

Characterization of the flow cytometric assay for ex vivo monitoring of cytotoxicity mediated by antigen-specific cytotoxic T lymphocytes

Several non-radioactive methods have widely been utilized to detect antigen-specific cytotoxic T lymphocyte (CTL) responses instead of the classical ⁵¹Cr-release assay. These methods include intracellular cytokine staining, major histocompatibility complex-class I tetramers, and the CD107a mobilization assay. However, they do not directly measure target-cell death. In contrast, several attempts have been made to develop the flow cytometric CTL (FC-CTL) assay for evaluation of cytotoxicity. However, further improvement is necessary for it to become standardized. Here, we evaluated the characteristics of the FC-CTL assay based on the uptake of propidium iodide (PI) using target cell lines expressing the green fluorescent protein (GFP). The FC-CTL assay was found to be sensitive enough to detect primary CTL responses. The usage of a pre-established GFP-expressing target cell line facilitated the procedure of the assay, and enabled a clear discrimination between target and effector cells. Time-course analyses demonstrated that PI-stained target cells were detected as early as surface CD107a expression after antigenic stimulation. Thus, the PI/GFP-based FC-CTL assay is sufficiently sensitive to practically detect the early stages of target-cell death, and may have a great potential for becoming a standard tool to measure CTL activity.

Multicolor Digital Flow Cytometry in Human Translational Immunology

By facilitating the simultaneous analysis of parameters from diverse cell lineages and biological pathways, multicolor flow cytometry is integral to many studies in human immunology-particularly those in older individuals-where sample amounts may be limiting. Studies in human cohorts require particular attention to fluorochrome panel design and procedures to standardize instrument performance; reproducible instrument conditions (over time and between centers) are crucial to accurate comparisons and conclusions in the analysis of heterogeneous groups of human subjects. Here, we describe procedures for multicolor digital flow cytometry, our experience in flow cytometry panel design and our approach in standardizing instrument performance using BD Biosciences hardware and software (BD Biosciences, San Jose, CA). These techniques allow for the generation of accurate and precise data in a variety of settings.

Detection and Tracking of NY-ESO-1-Specific CD8+ T Cells by High-Throughput T Cell Receptor β (TCRB) Gene Rearrangements Sequencing in a Peptide-Vaccinated Patient

Comprehensive immunological evaluation is crucial for monitoring patients undergoing antigen-specific cancer immunotherapy. The identification and quantification of T cell responses is most important for the further development of such therapies. Using well-characterized clinical samples from a high responder patient (TK-f01) in an NY-ESO-1f peptide vaccine study, we performed high-throughput T cell receptor β-chain (TCRB) gene next generation sequencing (NGS) to monitor the frequency of NY-ESO-1-specific CD8⁺ T cells. We compared these results with those of conventional immunological assays, such as IFN-γ capture, tetramer binding and limiting dilution clonality assays. We sequenced human TCRB complementarity-determining region 3 (CDR3) rearrangements of two NY-ESO-1f-specific CD8⁺ T cell clones, 6-8L and 2F6, as well as PBMCs over the course of peptide vaccination. Clone 6-8L possessed the TCRB CDR3 gene TCRBV11-03*01 and BJ02-01*01 with amino acid sequence CASSLRGNEQFF, whereas 2F6 possessed TCRBV05-08*01 and BJ02-04*01 (CASSLVGTNIQYF). Using these two sequences as models, we evaluated the frequency of NY-ESO-1-specific CD8⁺ T cells in PBMCs ex vivo. The 6-8L CDR3 sequence was the second most frequent in PBMC and was present at high frequency (0.7133%) even prior to vaccination, and sustained over the course of vaccination. Despite a marked expansion of NY-ESO-1-specific CD8⁺ T cells detected from the first through 6th vaccination by tetramer staining and IFN-γ capture assays, as evaluated by CDR3 sequencing the frequency did not increase with increasing rounds of peptide vaccination. By clonal analysis using 12 day in vitro stimulation, the frequency of B*52:01-restricted NY-ESO-1f peptide-specific CD8⁺ T cells in PBMCs was estimated as only 0.0023%, far below the 0.7133% by NGS sequencing. Thus, assays requiring in vitro stimulation might be underestimating the frequency of clones with lower proliferation potential. High-throughput TCRB sequencing using NGS can potentially better estimate the actual frequency of antigen-specific T cells and thus provide more accurate patient monitoring.

T helper 17 cells and related cytokines after allergen inhalation challenge in allergic asthmatics

BACKGROUND

T helper (Th)17 cells may play a role in allergic asthma. This study assessed the effect of allergen inhalation challenge on circulating Th17 cells and related cytokines in allergic asthmatics.

METHODS

Peripheral blood mononuclear cells were collected from 16 atopic asthmatics before and 24 h after allergen challenge, as well as from 10 atopic nonasthmatics and 10 normal controls. Cells were stained for Th17 cytokines and their receptors (IL-17A, IL-17F, IL-21, IL-22, IL-17R, and IL-23R) using flow cytometry. Cytokine concentrations from cell culture supernatants were quantified using a multiplex assay for IL-17A, IL-17F, IL-21, IL-22, and IL-23.

RESULTS

At baseline, asthmatics had a higher percentage of circulating Th17 cells (1.2 ± 0.5%) compared to normal controls (0.9 ± 0.66%, p < 0.001) but not compared to atopic nonasthmatics (1.13 ± 0.5%). There was a significant increase in Th17 cells in asthmatics after allergen challenge to 1.55 ± 0.4% (p < 0.05) and a trend toward significance in IL-17R expression from 3.4 ± 4.3 to 6.86 ± 6.84% after allergen challenge (p = 0.06). There was also a significant reduction in IL-21-positive cells following allergen challenge from 3.46 ± 1.85 to 2.33 ± 1.37% (p < 0.001). There were no significant differences in IL-17F, IL-22 and IL-23R expression. The concentration of IL-17A in culture supernatant was significantly higher in asthmatics compared to normal controls and IL-17A significantly increased 24 h after allergen challenge.

CONCLUSIONS

The increase of Th17 cells and IL-17A in atopic asthma after allergen inhalation challenge suggests a possible role for Th17 in allergen-induced airway responses.

Exopolysaccharide-producing Bifidobacterium animalis subsp. lactis strains and their polymers elicit different responses on immune cells from blood and gut associated lymphoid tissue

The effect of exopolysaccharide (EPS) producing bifidobacteria, and the EPS derived thereof, on the modulation of immune response was evaluated. Cells isolated from gut associated lymphoid tissue (GALT) and from peripheral blood mononuclear cells (PBMC) of naïve rats were used. The proliferation and cytokine production of these immune cells in the presence of the three isogenic Bifidobacterium animalis subsp. lactis strains (A1, A1dOx and A1dOxR), as well as their purified polymers, were in vitro analysed. The cytokine pattern produced by immune cells isolated from GALT showed that most levels remained stable in the presence of the three strains or their corresponding polymers. However, in PBMC the UV-inactivated bacteria induced higher levels of the ratios IFNγ/IL-17, TNFα/IL-10 and TNFα/TGFβ, and no variation in the ratio IFNγ/IL-4. Thus, B. animalis subsp. lactis strains were able to activate blood monocytes as well as T lymphocytes towards a mild inflammatory Th1 response. Furthermore, only the EPS-A1dOxR was able to stimulate a response in a similar way than its EPS-producing bacterium. Our work supports the notion that some bifidobacterial EPS could play a role in mediating the dialog of these microorganisms with the immune system. In addition, this study emphasizes the effect that the origin of the immune cells has in results obtained; this could explain the great amount of contradiction found in literature about the immunomodulation capability of EPS from probiotic bacteria.

Advances in immune-based therapies of renal cell carcinoma

Renal cell carcinoma (RCC) is the most prevalent malignancy within the kidney, and over 40% of patients with RCC will die from their disease. Approximately a third of patients present with metastatic disease and a third of patients undergoing nephrectomy for clinically localized RCC will develop metastases. Metastatic RCC poses a therapeutic challenge due to its resistance to conventional modes of therapy such as chemotherapy and radiation therapy. While it is clear that strides have been made against metastatic RCC, the overall objective response rates of interleukin-2- and interferon-alpha-based immunotherapy remain at approximately 20%. Despite advances in biologic- and immune-based therapies, long-term survival for patients with metastatic RCC remains modest. Furthermore, the toxicity profile of these cytokine regimens is significant. Advances in the understanding of the nature of tumor antigens and their optimal presentation, and in the regulatory mechanisms that govern the immune system, have provided multiple novel immunotherapy intervention strategies with increased specificity and potentially fewer side effects. Such strategies are currently being tested in clinical trials.

A real-time killing assay to follow viral epitope presentation to CD8 T cells

The ability of cytotoxic T lymphocytes (CTL) to clear virus-infected cells requires the presentation of viral peptides intracellularly processed and displayed by major histocompatibility complex class I. Assays to measure CTL-mediated killing often use peptides exogenously added onto target cells--which does not account for epitope processing--or follow killing of infected cells at a single time point. In this study we established a real-time fluorogenic cytotoxic assay that measures the release of the Glucose-6-phosphate-dehydrogenase by dying target cells every 5 min after addition of CTL. It has comparable sensitivity to (51)chromium-based killing assay with the additional advantage of incorporating the kinetics of epitope presentation. We showed that HIV infection of immortalized or primary CD4 T cells leads to asynchronous killing by two CTL clones specific for epitopes located in different proteins. Real-time monitoring of killing of virus-infected cells will enable identification of immune responses efficiently preventing virus dissemination.

Multiparameter flow cytometry: advances in high resolution analysis

Over the past 40 years, flow cytometry has emerged as a leading, application-rich technology that supports high-resolution characterization of individual cells which function in complex cellular networks such as the immune system. This brief overview highlights advances in multiparameter flow cytometric technologies and reagent applications for characterization and functional analysis of cells modulating the immune network. These advances significantly support high-throughput and high-content analyses and enable an integrated understanding of the cellular and molecular interactions that underlie complex biological systems.

Estimating point and interval frequency of antigen-specific CD4+ T cells based on short in vitro expansion and improved poisson distribution analysis

BACKGROUND

Knowledge of antigen-specific CD4(+) T cells frequencies is pivotal to the choice of the antigen to be used in anti-viral and anti-tumor vaccination procedures and for monitoring of immune responses. Methods that employ small cell numbers from patient samples, are easy to perform and do not require complex techniques/instrumentations and therefore standardization are desirable.

METHODOLOGY/PRINCIPAL FINDINGS

Purified blood CD4(+) T cells from healthy donors were cultured with autologous antigen presenting cells in several replicate wells in equal numbers in the absence (un-stimulated wells) or in the presence of synthetic peptides corresponding to viral antigens promiscuous HLA-DR epitopes (antigen-stimulated wells). At day 7 of culture low dose IL-2 was added and at day 14 IFN-γ and IL-5 release in the supernatant was measured. A statistical analysis approach, based on Poisson distribution, was then implemented to calculate the frequency of viral-specific CD4(+) T cells. We first determined a patient-specific exceptionality threshold of cytokine release in the un-stimulated wells and then, based on this threshold, we counted the inactive/active wells within the antigen-stimulated wells. This number, along with the number of cells per well, allowed the point and interval estimates of frequencies. A ready-to-use Excel worksheet template with automatic calculations for frequencies estimate was developed and is provided as a supplemental file (Table S9).

CONCLUSIONS/SIGNIFICANCE

We report a simple experimental procedure combining short term in vitro cell culture with statistical analysis to calculate the frequency of antigen-specific CD4(+) T cells. The detailed experimental procedure along with the Excel applicative are a valuable tool for monitoring immune responses in the clinical practice.

Micropatterned aptasensors for continuous monitoring of cytokine release from human leukocytes

We report the development of a microdevice for detecting local interferon gamma (IFN-γ) release from primary human leukocytes in real time. Our microdevice makes use of miniature aptamer-modified electrodes integrated with microfluidics to monitor cellular production of IFN-γ. The aptamer species consists of a DNA hairpin molecule with thiol groups on the 3'-end for self-assembly onto Au electrodes. A redox reporter is covalently attached at the 5'-end for electrochemical sensing. This aptasensor has excellent sensitivity for IFN-γ (<60 pM detection limit) and responds to the target analyte in real time without additional washing or labeling steps. Aptamer-functionalized electrode arrays are fabricated on glass slides containing poly(ethylene glycol) (PEG) hydrogel patterns designed to expose glass regions adjacent to electrodes while protecting the remainder of the surface from nonspecific adsorption. The micropatterned substrates are integrated with PDMS microfluidic channels and incubated with T-cell-specific antibodies (Ab) (anti-CD4). Upon injection of blood, leukocytes are bound to Ab-modified glass regions in proximity to aptasensors. Cytokine release from captured cells is triggered by mitogenic activation and detected at the aptamer-modified electrodes using square wave voltammetry (SWV). The IFN-γ signal is monitored in real time with signal appearing as early as 15 min poststimulation from as few as 90 T cells. The observed IFN-γ release profiles are used to calculate an initial IFN-γ production rate of 0.0079 pg cell(-1) h(-1) upon activation. The work described here represents an important step toward development of aptasensors for immune cell analysis and blood-based diagnostics.

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.

Application of flow cytometry in pediatric hematology-oncology

Applications of flow cytometry in pediatric cancers have expanded substantially in recent years. In acute leukemias, the commonest childhood cancer, flow cytometry can now define complex antigenic profiles that are associated with specific cytogenetic/molecular defects and can also directly identify BCR-ABL fusion protein. Flow cytometry based scoring system has been described for diagnosis of myelodysplastic syndromes. In solid tumors, flow cytometry was previously used mainly to determine DNA content for prognosis; however, recent studies in children with neuroblastoma and Ewing sarcoma have identified its diagnostic utility. In this review, we will discuss the current and future applications of flow cytometry in pediatric hematology-oncology.

Flow cytometric analysis of cell signaling proteins

In recent years, techniques that combine the use of phospho-specific antibodies and multiparameter flow cytometry have been developed for the detection of protein phosphorylation at the single cell level. Flow cytometry is uniquely suited for this type of analysis, as it can measure functional and phenotypic markers in the context of complex cell populations. Phosphorylation can be assessed simultaneously in multiple cell subsets, and due to the small sample sizes required, and the rapid analyses of large numbers of cells in this approach, rare cell analysis is possible without the ex vivo expansion of cells.In this chapter, we detail flow cytometric protocols for the detection of intracellular phospho-proteins in samples derived from whole blood and peripheral blood mononuclear cell preparations. These protocols define steps for cell activation, fixation, permeabilization, and staining by phospho-specific and phenotyping antibodies. We discuss technical difficulties inherent to this technique and suggest solutions to commonly encountered problems. Additionally, we show examples of phospho-protein detection in lymphocyte subsets, dendritic cells, and monocytes activated with various stimuli, including mitogens, cytokines, and superantigens. Finally, we highlight a potential clinical trial application for this flow cytometric assay as a platform for pharmacodynamic monitoring of kinase inhibitors.

Antioxidant supplementation alters cytokine production from monocytes

We studied in 10 healthy subjects the effect of chronic enteral supplementation of antioxidants (vitamins E, C, A, allopurinol, and N-acetylcysteine) on cytokine production by monocytes at rest, end exercise (60-min cycling at 60% of maximum oxygen consumption), and 60 min post-exercise (recovery). The percentage and the mean fluorescent intensity (MFI) of both unstimulated and lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6-producing monocytes were detected using flow cytometry. Antioxidants decreased the percentage of unstimulated IL-6-producing monocytes following exercise, while their MFI increased at rest. The percentage of LPS-stimulated monocytes increased after exercise and they produced more IL-6 both at rest and following exercise. The percentage of unstimulated and LPS-stimulated IL-1beta-producing monocytes was not affected by antioxidants. The MFI of IL-1beta-produced unstimulated monocytes was increased after antioxidants both at rest and following exercise. After antioxidants, LPS-stimulated monocytes produced more IL-1beta following exercise. Antioxidants decreased the percentage of TNF-alpha spontaneously-produced monocytes following exercise, which produced more TNF-alpha at recovery. Antioxidants did not affect the percentage of LPS-stimulated monocytes producing TNF-alpha, while LPS-stimulated production of TNF-alpha increased both at rest and following exercise. Antioxidants differentially affect TNF-alpha, IL-1beta, and IL-6 production by monocytes, with a general tendency of augmenting cytokine production.

New flow cytometric assays for monitoring cell-mediated cytotoxicity

The exact immunologic responses after vaccination that result in effective antitumor immunity have not yet been fully elucidated and the data from ex vivo T-cell assays have not yet defined adequate surrogate markers for clinical efficacy. A more detailed knowledge of the specific immune responses that correlate with positive clinical outcomes should help to develop better or novel strategies to effectively activate the immune system against tumors. Furthermore, clinically relevant material is often limited and, thus, precludes the ability to perform multiple assays. The two main assays currently used to monitor lymphocyte-mediated cytoxicity in cancer patients are the (51)Cr-release assay and IFN-gamma ELISpot assay. The former has a number of disadvantages, including low sensitivity, poor labeling and high spontaneous release of isotope from some tumor target cells. Additional problems with the (51)Cr-release assay include difficulty in obtaining autologous tumor targets, and biohazard and disposal problems for the isotope. The ELISpot assays do not directly measure cytotoxic activity and are, therefore, a surrogate marker of cyotoxic capacity of effector T cells. Furthermore, they do not assess cytotoxicity mediated by the production of the TNF family of death ligands by the cytotoxic cells. Therefore, assays that allow for the simultaneous measurement of several parameters may be more advantageous for clinical monitoring. In this respect, multifactor flow cytometry-based assays are a valid addition to the currently available immunologic monitoring assays. Use of these assays will enable detection and enumeration of tumor-specific cytotoxic T lymphocytes and their specific effector functions and any correlations with clinical responses. Comprehensive, multifactor analysis of effector cell responses after vaccination may help to detect factors that determine the success or failure of a vaccine and its immunological potency.

Clinical implications of the type 1/type 2 balance of helper T cells and P-glycoprotein function in peripheral T lymphocytes of myasthenia gravis patients

Myasthenia gravis is an autoimmune disorder mediated by antibodies against the acetylcholine receptors of the skeletal muscles. Imbalances between T helper type 1 and type 2 cytokine production play a key role in the induction and development of several autoimmune diseases. Peripheral T helper type 1 and type 2 cells in 50 myasthenia gravis patients were estimated by intracellular cytokines. The percentage of T helper type 1 cells in CD4(+) cells was higher than that of type 2 or type 0 cells (P<0.0001). There was a significant correlation between T helper type 1/type 2 ratio and the P-glycoprotein function on CD3(+) T cells (P=0.008). In the patients treated with prednisolone alone (n=12), there was a significant correlation negatively between the percentage of change in the T helper type 1/type 2 ratio and the reduction rate of quantitative myasthenia gravis scores after 12 months of treatment (P=0.012). In contrast, all of the patients treated with prednisolone and calcineurin inhibitor in combination saw reductions in the scores. Our data suggest that the T helper type 1/type 2 ratio was involved in the disease activity of the patients treated with prednisolone alone. On the other hand, the patients treated with prednisolone and calcineurin inhibitor in combination had their disease condition improved regardless of the T helper type 1 predominance. Therefore, the data suggest that supplemental calcineurin inhibitors are effective for the myasthenia gravis patients treated with prednisolone alone when their T helper balance shifts toward to type 1.

Immunotoxicology: Opportunities for Non-animal Test Development

At present, several animal-based assays are used to assess immunotoxic effects such as immunosuppression and sensitisation. The use of whole animals, however, presents several secondary issues, including expense, ethical concerns and relevance to human risk assessment. There is a growing belief that non-animal approaches can eliminate these issues without impairing human safety, provided that biological markers are available to identify the immunotoxic potentials of new chemicals to which humans may be exposed. Driven by the 7th Amendment to the EU Cosmetics Directive, the new EU policy on chemicals (the REACH system), proposals to update the European legislation on the protection of animals used in research, and emerging visions and strategies for predicting toxicity, such in vitro methods are likely to play a major role in the near future. The realisation that the immune system can be the target of many chemicals, resulting in a range of adverse effects on the host's health, has raised serious concerns from the public and within the regulatory agencies. Hypersensitivity and immunosuppression are considered the primary focus for developing in vitro methods in immunotoxicology. However, in vitro assays to detect immunostimulation and autoimmunity are also needed. This review of the state-of-the-art in the field of in vitro immunotoxicity, reveals a lack of cell-based immunotoxicity assays for predicting the toxicity of xenobiotics toward the immune system in a simple, fast, economical and reliable way.

Development of an artificial-antigen-presenting-cell-based assay for the detection of low-frequency virus-specific CD8(+) T cells in whole blood, with application for measles virus

Evaluation of the immune responses induced by childhood vaccines requires measurement of T-cell, as well as antibody, responses. However, cellular immune responses are often not analyzed because of technical hurdles and the volume of blood required. Therefore, a sensitive and specific assay for antigen-specific T cells that utilizes a small volume of blood would facilitate new vaccine evaluation. We developed a novel assay for quantifying virus-specific CD8(+) T cells that combines the use of HLA-A2 immunoglobulin-based artificial antigen-presenting cells (aAPCs) for stimulation of antigen-specific CD8(+) T cells in whole blood with quantitative real-time reverse transcription-PCR (qRT-PCR) to detect gamma interferon (IFN-gamma) mRNA. This assay was optimized using a well-established cytomegalovirus (CMV) CD8(+) T-cell system. The aAPC-qRT-PCR assay had comparable sensitivity to intracellular cytokine staining (ICS) in detecting CMV-specific CD8(+) T cells with a detection limit of less than 0.004%. The assay was applied to the detection of low-frequency measles virus (MV)-specific CD8(+) T cells by stimulating blood from five MV-immune HLA-A*0201 donors with four different MV-specific peptides (MV peptide aAPCs). Stimulation with three of the MV peptide aAPCs resulted in significant increases in IFN-gamma mRNA ranging from 3.3- to 13.5-fold. Our results show that the aAPC-qRT-PCR assay is highly sensitive and specific and can be standardized for screening MV-specific CD8(+) T cells in vaccine trials. The technology should be transferable to analysis of CD8(+) T-cell responses to other antigens.

Comparison of intracellular cytokine flow cytometry and an enzyme immunoassay for evaluation of cellular immune response to active tuberculosis

A prospective cross-sectional blinded study of 28 patients (21 male and 7 female patients; mean age, 44 years) with suspected active tuberculosis (TB) attending a TB and chest clinic is described. Blood was taken for immune cell enumeration, a whole-blood enzyme-linked immunosorbent assay (ELISA) for the detection of gamma interferon (IFN-gamma) by the QuantiFERON-TB Gold (QFT-G) assay, and intracellular cytokine flow cytometry (ICC) analysis; and sputum was simultaneously taken for bacteriological culture for Mycobacterium tuberculosis. Twelve healthy subjects were included as controls. The performance characteristics of the QFT-G and ICC assays for the detection of active TB were compared. Among the patients with active TB, we found (i) normal to slightly elevated peripheral CD4(+) and CD8(+) T-cell counts but a significant reduction in the number of NK cells; (ii) CD4(+) T cells were the major cell type producing IFN-gamma, a type 1 cytokine; (iii) small percentages of CD8(+) T cells were also primed for IFN-gamma production; (iv) the production of interleukin-4 (IL-4), a type 2 cytokine, was not prominent; and (v) the sensitivity and the specificity of the QFT-G assay were 88.2% and 18%, respectively, and those of the ICC assay were 94.1% and 36.4%, respectively. The specificities of the blood tests were likely underestimated due to cross-reaction to a non-M. tuberculosis mycobacterial infection and the lack of a confirmatory test that could be used to diagnose latent M. tuberculosis infection. Flow cytometry accurately locates the pool of immunological effector cells responsible for cytokine production during active TB. The ICC assay is an additional useful tool for the diagnosis of active TB.

Autologous nucleus pulposus primes T cells to develop into interleukin-4-producing effector cells: an experimental study on the autoimmune properties of nucleus pulposus

An autoimmune response to herniated nucleus pulposus has been proposed to constitute a pathophysiologic mechanism for inducing sciatica based on the fact that nucleus pulposus under normal conditions is excluded from the development of immunological tolerance. The manifestation of an autoimmune response comprises different steps starting with antigen capture, continuing with activation of T helper (T(H)) cells and ending with production of autoantibodies. Activated T(H) cells differentiate into either T(H)1 cells, predominately producing proinflammatory cytokines such as interferon gamma (IFNgamma) or a T(H)2 subset mainly producing anti-inflammatory cytokines such as interleukin-4 (IL-4). The aim of the present study was to examine if exposure of autologous nucleus pulposus (NP) to the immune system for 3 weeks is potent enough to prime T(H) cells to differentiate into T(H)2 cells. The study was performed in a pig model allowing the exposure of NP to the immune system. To assess the polarization of T(H) cells the intracellular production of IFNgamma and IL-4 was measured in T cells by using flow cytometry. The revealed predominant production of IL-4 together with low production of IFNgamma in T cells after NP exposure to the immune system indicates that nucleus pulposus may prime T(H) cells to develop into IL-4-producing T(H)2 cells after being exposed to the immune system, for example, in association with disc herniation.

FATT-CTL assay for detection of antigen-specific cell-mediated cytotoxicity

Here we describe a flowcytometric assay that measures the defining function of virus-specific cytotoxic T lymphocytes (CTL), i.e., killing viral protein expressing cells. The fluorescent antigen-transfected target cell (FATT)-CTL assay requires no viruses, recombinant viral vectors, or radioactive isotopes to generate CTL target cells that present naturally processed epitopes. It facilitates developing standardized applications in clinical trial settings. Plasmid vectors encoding antigen-green fluorescent protein (GFP) fusion proteins were used directly to nucleofect immortalized B cells or peripheral blood mononuclear cells (PBMCs). Elimination of antigen-GFP expressing cells by cloned CTL, in vitro sensitized PBMC, or ex vivo PBMC was quantified following a 4-18-h coculture period by flowcytometry. This technology successfully detected cell-mediated cytotoxicity in studies involving human PBMC and various viral antigens, including structural proteins of influenza A virus, and structural and nonstructural HIV proteins. Standardized protocols are currently being developed in the framework of a clinical immunotherapy trial in HIV-infected individuals. The FATT-CTL assay principles facilitate standardized flowcytometric detection of antigenic protein-specific cell-mediated cytotoxicity in many different basic research and clinical trial settings. By measuring their defining function, the FATT-CTL assay contributes to a more complete assessment of antigen-specific CTL responses to infection and vaccination.

Use of CD137 to study the full repertoire of CD8+ T cells without the need to know epitope specificities

CD137 (4-1BB) is a member of the TNFR-family with costimulatory function, triggering prosurvival signals in activated T-cells. Upregulation of CD137 upon stimulation allows identifying and isolating live, human antigen-specific CD8+ T-cells of all phenotypes, and therefore provides a comprehensive detection method. Furthermore responses against antigen mixtures can be easily detected, enabling antigen discovery in a stepwise deconvoluting approach. In this article, we will discuss various aspects of this methodology, including potential pitfalls as well as a variety of applications, as illustrated by examples from our laboratory.

A microdevice for multiplexed detection of T-cell-secreted cytokines

Cytokines are produced by immune cells in response to viral or bacterial pathogens and therefore have significant diagnostic value. The goal of the present study was to develop a miniature device for detection of interleukin (IL)-2 and interferon (IFN)-gamma cytokines secreted by a small population of CD4 and CD8 T-cells. Microarrays of T-cell- and cytokine-specific Ab spots were printed onto poly(ethylene glycol) (PEG) hydrogel-coated glass slides and enclosed inside a microfluidic device, creating a miniature ( approximately 3 microL) immunoreaction chamber. Introduction of the red blood cell (RBC) depleted whole human blood into the microfluidic device followed by washing at a pre-defined shear stress resulted in isolation of pure CD4 and CD8 T-cells on their respective Ab spots. Importantly, the cells became localized next to anti-IL-2 and -IFN-gamma Ab spots. Mitogenic activation of the captured T-cells was followed by immunofluorescent staining (all steps carried out inside a microfluidic device), revealing concentration gradients of surface-bound cytokine molecules. A microarray scanner was then used to quantify the concentration of IFN-gamma and IL-2 near CD4 and CD8 T-cells. This study represents one of the first demonstrations of a microdevice for capturing desired T-cell subsets from a small blood volume and determining, on-chip, cytokine profiles of the isolated cells. Such a microdevice is envisioned as an immunology tool for multi-parametric analysis of T-cell function with direct applications in diagnosis/monitoring of HIV and other infectious diseases.

Immune responses to mumps vaccine in adults who were vaccinated in childhood

BACKGROUND

In a mumps outbreak in the United States, many infected individuals were adults who had received 2 doses of mumps vaccine. The persistence of cellular immunity to mumps vaccine has not been defined.

METHODS

This was an observational, nonrandomized cohort study evaluating cell-mediated and humoral immunity to mumps in 10 vaccinated and 10 naturally immune adults. Mumps-specific T cell activation and interferon (IFN)-gamma production were measured using lymphoproliferative and flow cytometry assays, and mumps immunoglobulin (Ig) G was measured using enzyme-linked immunosorbent assay.

RESULTS

T cell immunity to mumps was high in both groups; 70% of vaccinated and 80% of naturally immune individuals had a positive (> or =3) stimulation index (SI) (P = 1.0). The mean percentages of mumps-specific CD4+ T cells that expressed CD69 and produced IFN-gamma were equivalent in the 2 groups: 0.06% and 0.12%, respectively (P = .11). The mean SIs in the groups were also equivalent, although IFN-gamma concentrations from cultures stimulated with mumps antigen were higher in naturally immune adults than in vaccinated adults (P < or = .01). All adults were positive for mumps IgG.

CONCLUSION

T and B cell immunity to mumps was detected in adults at least 10 years after immunization. Except for IFN-gamma release, responses in vaccinated adults paralleled those observed in naturally immune individuals.

The role of flow cytometry in the interferon-gamma-based diagnosis of active tuberculosis and its coinfection with HIV-1--A technically oriented review

TB remains uncontrolled. In resource-rich countries, only approximately 60% of diagnoses are confirmed by culture. The number is lower in resource-poor environments. Huge scope therefore exists for alternative diagnostic strategies. Counting antigen-specific lymphocytes by virtue of cytokine production following 8-16 h stimulation with tuberculosis antigens is currently the strategy of choice. Several methods exist, including ELISA, ELISpots, and flow cytometry. Although it is clear that blood samples stimulated by ESAT-6 and CFP-10 antigens discriminate between TB infection and BCG vaccination, it is flow-cytometry that seems to be able to distinguish active TB disease from mere TB exposure. Of the various flow-protocols including four-color tests (CD45-CD3-CD4-IFNgamma), three-color tests (CD3-CD4-IFNgamma) and two-color tests (CD4-IFNgamma), even the simplest is performing well, provided that the results are expressed as percentage of IFN-gamma+ cells per CD4+ lymphocytes (%IFNgamma/CD4+). Studies using broncho-alveloar lavage (BAL) and Induced-Sputum (ISp) show that TB-specific CD4+IFN-gamma+ T cells accumulate in the lung in pulmonary and extra-pulmonary TB at frequencies >5-20-fold more frequent than in blood. This pulmonary homing is absent following BCG immunization. The use of PPD to stimulate CD4+IFN-gamma+ cells in the lung in active TB leads to >3-12-fold greater responses than seen with CFP-10 or ESAT-6, and any interference from BCG vaccination is absent. This method is unaffected by HIV coinfection, which has always been the problem for other immune-based diagnostics. Further, lung-based samples provide material for rapid tests of both the IFN-gamma assay and bacteriology, and importantly, these tests are amenable for future simplification with automated fluorescence-image cytometers.Another development of the multiparameter analytical power of flow-cytometry is to use markers for "lung-seeking" populations of CD4+ T cells in blood, obviating lung sampling. In active TB, but not in BCG vaccinees, TB-specific memory CD4+ T cells can be found in blood that are dominantly CD27-negative and probably lung seeking and can be diagnostically useful.

Use of quantitative flow cytometry to measure ex vivo immunostimulant activity of echinacea: the case for polysaccharides

INTRODUCTION

When directly exposed to various echinacea fractions, human leukocytes ex vivo are strongly stimulated to proliferate and to produce immunostimulation and inflammatory cytokines. A comparison of fractions containing lipoidal small molecules and high-molecular-weight water-soluble polysaccharides indicates that the latter are substantially more potent as immunostimulants. Echinacea purpurea (L.) Moench, E. angustifolia DC, and E. pallida (Nutt.), Nutt. extracts, and each plant part contain significantly potent constituents. Flow cytometric techniques were utilized.

OBJECTIVES

This study was undertaken to determine whether flow cytometry could measure immunostimulant activity present in echinacea and, if so, which species produced more activity, which plant part was the most active, and whether the organic soluble or the aqueous extractables were more active. Ex vivo human clinical material was employed.

DESIGN

Echinacea extracts were analyzed using flow cytometric techniques. The immunostimulation assays were measured in triplicate.

METHODS

Samples dissolved in dimethyl sulfoxide (DMSO) were added to 200 microL of heparinized blood mixed with 50 muL of phosphate buffer, vortexed, and incubated to allow adequate time for immune-cell stimulation. Fifty (50) microL of the stimulated blood samples were added to each of a reagent cocktail consisting of 20 microL of CD4FITC/CD69PE/CD3PerCP expressed on the helper/inducer T-lymphocyte subset; CD8FITC/CD69/PE/ CD3PerCP expressed on the human suppresser/cytotoxic T-lymphocytes and on a subset of natural killer lymphocytes; CD19FITC/CD69PE/CD45PerCP expressed on B-lymphocytes; or CD56FITC/CD69PE/CD45PerCP expressed on NK lymphocytes. Four hundred and fifty (450) microL of 1 X FACS lysing solution was added and incubated in the dark (rt, 30 minutes) and then subjected to flow cytometric analysis. All reported readings are the average of several determinations. Positive controls consisted of phorbol myristyl acetate (PMA) (50 ng/mL), phytohemagglutinin (10 microg/mL), CD2/CD2R (positive activation control)(5 microL/250 muL of reaction), and negative controls consisted of dimethyl sulfoxide (2% in RPMI-1640), RPMI-1640 medium, and cyclosporin A (10 microg/mL).

RESULTS

The main immunostimulatory activity of echinacea resides in the water-soluble materials rather than the lipoidal small molecules. E. purpurea, E. Pallida, and E. angustifolia leaves, stems, flowering tops, and roots all produce substantial immunostimulatory activity.

CONCLUSIONS

The use of flow cytometry demonstrates a link between the polysaccharides in echinacea and the biologic immunostimulatory effect that has therapeutic relevance, and strong evidence for this immunostimulant property is presented.

Lymphocyte subpopulations in human exposure to metals (IUPAC Technical Report)

Numerous species of metal ions cause immunosensitization in humans. Possible approaches to determine those occupational and environmental exposures to metals that result in immunological changes include lymphocyte transformation assay, cytokine profiling, and measurement of lymphocyte subpopulations. In two previous papers, we considered lymphocyte transformation assay [1] and cytokine profiling [2]. Here we review the effects of exposures to metals on lymphocyte subpopulations. Specific consideration is given to beryllium, chromium, cobalt, nickel, palladium and platinum, cadmium, gold, mercury, and lead. Analysis of the scientific literature shows that immunosensitizing metals may have influences on the lymphocyte subset composition, but only in a few instances does exposure to metals cause reproducible shifts of lymphocyte subpopulations. If lymphocyte subpopulations are analyzed, each diagnostic step, including indication, sample handling, analytic procedure, and data interpretation, should adhere to good quality assurance and quality control.

Peripheral CD4+ T cells showing a Th2 phenotype in a patient with Mikulicz's disease associated with lymphadenopathy and pleural effusion

Mikulicz's disease (MD) is a unique IgG4-related systemic disease indicated by enlargement of the lachrymal and salivary glands and which differs substantially from Sjögren's syndrome. A male patient with pleural effusion, swelling of the submandibular glands, and swelling of the paraaortic, mediastinal, and pararenal lymph nodes was diagnosed with MD. Analysis of peripheral CD4+ T cells from the patient revealed deviation of the Th1/Th2 balance to Th2. Prednisolone therapy ameliorated the disease and corrected the Th1/Th2 imbalance.

Peripheral inflammatory cytokines as biomarkers in Alzheimer's disease and mild cognitive impairment

BACKGROUND

Several lines of evidence in the literature have shown that inflammation is involved in the pathogenesis of Alzheimer's disease (AD). However, the results from the evaluation of serum inflammatory markers in AD patients have been controversial.

OBJECTIVE

To determine if any differences exist in the monocytic secretion pattern of IL-1beta, IL-6, IL-12 and TNF-alpha from mild cognitive impairment (MCI) and AD patients, when compared with healthy age-matched controls.

METHODS

To evaluate the percentage of peripheral monocytes secreting IL-1beta, IL-6, IL-12 and TNF-alpha along with the relative levels of these proteins, a cytofluorimetric analysis was conducted under basal conditions and after lipopolysaccharide-induced cell activation.

RESULTS

We found, in AD and MCI patients, a significant raise in the percentage of monocytes producing the studied cytokines (under basal conditions and after the exposure to an inflammatory stimulus), as well as a decreased competence of these cells to respond to inflammatory challenges, when compared with controls.

CONCLUSIONS

These results agree with a persistent inflammatory status in AD, reinforcing the hypothesis of a progressive impairment of the immune response in this disorder and suggesting that monocytes may be good targets to study the progression from MCI to AD.

Rare-Event Analysis in Flow Cytometry

Technical aspects of rare-event detection are discussed in this article in a practical context, with two real-life examples. A growing number of flow cytometry-based assays depend on rare-event detection for basic science and clinical applications.

Intelligent bioprocessing for haemotopoietic cell cultures using monitoring and design of experiments

The need for successful ex-vivo expansion and directed differentiation of haematopoietic stem cells (HSCs) for therapeutic applications has increased over the past decade. Haematopoietic cell cultures are complex and full characterisation of the process environment has yet to be achieved. The complexity and transient nature of HSC cultures make the identification, maintenance and control of optimal operating conditions challenging. Application of real-time, on-line monitoring techniques and process control strategies enhances the ability to operate bioprocesses of desired reproducibility and high product quality. In this review, we discussed the methods by which in vitro culture information necessary for bioprocess control may be obtained, including process considerations, monitoring and analytical tools, and design of experiments (DOE). The successful application of these tools may result in time- and cost-effective cultures for directed differentiation and expansion of haematopoietic components intended for clinical use.

A novel multiparametric flow cytometry-based cytotoxicity assay simultaneously immunophenotypes effector cells: comparisons to a 4 h 51Cr-release assay

Natural killer (NK) cell-or T cell-mediated cytotoxicity traditionally is measured in 4-16 h (51)Cr-release assays (CRA). A new four-color flow cytometry-based cytotoxicity assay (FCC) was developed to simultaneously measure NK cell cytotoxicity and NK cell phenotype (CD3(-)CD16(+)CD56(+)). Target cells, K562 or Daudi, were labeled with Cell Tracker Orange (CTO) prior to the addition of effector cells. Following co-incubation, 7 amino-actinomycin D (7-AAD) was added to measure death of target cells. The phenotype of effectors, viability of targets, the formation of tumor-effector cell conjugates and absolute numbers of all cells were measured based on light scatter (FSC/SSC), double discrimination of the fluorescence peak integral and height, and fluorescence intensity. Kinetic studies (0.5 and 1 to 4 h) at different effector to target (E:T) cell ratios (50, 25, 12, and 6) confirmed that the 3 h incubation was optimal. The FCC assay is more sensitive than the CRA, has a coefficient of variation (CV) 8-13% and reliably measures NK cell-or lymphokine-activated killer (LAK) cell-mediated killing of target cells in normal controls and subjects with cancer. The FCC assay can be used to study a range of phenotypic attributes, in addition to lytic activity of various subsets of effector cells, without radioactive tracers and thus, it is relatively inexpensive. The FCC assay has a potential for providing information about molecular interactions underlying target cell lysis and thus becoming a major tool for studies of disease pathogenesis as well as development of novel immune therapies.

Comparison of cellular functionality of human mesenchymal stromal cells and PBMC

BACKGROUND

Human mesenchymal stromal cells (MSC) and PBMC play significant roles in repair processes following inflammation. Mechanisms of recruitment are still under investigation.

METHODS AND RESULTS

MIP-1alpha induced the chemotactic migration of MSC but not of PBMC. Correlating with this, 7.7% of MSC expressed the chemokine receptor CCR-1, as shown by FACS analysis. In contrast, PBMC did not express CCR-1 or CCR-2 but did express CXCR-4 (81.9%) and CCR-7 (42.2%). Setum induced the chemotaxis of both cell types, and zymosan activation increased the migration of PBMC but not of MSC. Corresponding with this, C5a induced the migration of PBMC but not of MSC. Dose-dependent and -specific adhesion to fibronectin, fibrinogen, collagen type I and collagen type II could be demonstrated for MSC; in contrast, PBMC did not adhere to any of the investigated proteins. Real-time PCR of receptor expression revealed a 12.2-fold higher expression of alphav in MSC compared with PBMC. Incubation of MSC with tumor necrosis factor-alpha (TNFalpha) induced NFkappaB activation and increased the chemotactic response to serum and adhesion to fibronedtin.

DISCUSSION

Chemotaxis and adhesion are crucial and differing cell fundtons of MSC and PBMC.

Immunology and immunotherapy approaches for prostate cancer

Several mechanisms that impair the immune response to promote tumour progression are reported. These mechanisms aim to reduce the ability of antigen-presenting cells to present antigen and activate naïve T cells to support an active immune response or to create a suppressive environment that induce non-functional tumour-associated antigen-specific T cells. Prostate cancer (PC) alone accounts for 33% of incident cancer cases and about 9% of all cancer-related deaths among men in the USA during 2006. Whereas androgen deprivation has remained the first line of therapy for advanced PC, other therapies are still required due to progression to an androgen-resistant state and eventually loss of control in patients receiving hormonal therapy. Immunotherapy seems to be a promising approach to enhance tumour-specific T-cell responses in different cancers including prostate. More importantly, clinical trials in advanced PC patients have shown that immunotherapy may generate significant clinical responses. Immunology and immunotherapy aspects of PC with focus on prostate-specific antigen will be presented.

Clinical experience with plasmid DNA- and modified vaccinia virus Ankara-vectored human immunodeficiency virus type 1 clade A vaccine focusing on T-cell induction

Candidate human immunodeficiency virus type 1 (HIV-1) vaccines focusing on T-cell induction, constructed as pTHr.HIVA DNA and modified vaccinia virus Ankara (MVA).HIVA, were delivered in a heterologous prime-boost regimen. The vaccines were tested in several hundred healthy or HIV-1-infected volunteers in Europe and Africa. Whilst larger trials of hundreds of volunteers suggested induction of HIV-1-specific T-cell responses in <15 % of healthy vaccinees, a series of small, rapid trials in 12-24 volunteers at a time with a more in-depth analysis of vaccine-elicited T-cell responses proved to be highly informative and provided more encouraging results. These trials demonstrated that the pTHr.HIVA vaccine alone primed consistently weak and mainly CD4(+), but also CD8(+) T-cell responses, and the MVA.HIVA vaccine delivered a consistent boost to both CD4(+) and CD8(+) T cells, which was particularly strong in HIV-1-infected patients. Thus, whilst the search is on for ways to enhance T-cell priming, MVA is a useful boosting vector for human subunit genetic vaccines.