Clinical and immunological responses in metastatic melanoma patients vaccinated with a high-dose poly-epitope vaccine

Assessment of CD8+ T-cell mediated immunity in an influenza A(H3N2) human challenge model in Belgium: a single centre, randomised, double-blind phase 2 study

BACKGROUND

Protection afforded by inactivated influenza vaccines can theoretically be improved by inducing T-cell responses to conserved internal influenza A antigens. We assessed whether, in an influenza controlled human infection challenge, susceptible individuals receiving a vaccine boosting T-cell responses would exhibit lower viral load and decreased symptoms compared with placebo recipients.

METHODS

In this single centre, randomised, double-blind phase 2 study, healthy adult (aged 18-55 years) volunteers with microneutralisation titres of less than 20 to the influenza A(H3N2) challenge strain were enrolled at an SGS quarantine facility in Antwerp, Belgium. Participants were randomly assigned double-blind using a permuted-block list with a 3:2 allocation ratio to receive 0·5 mL intramuscular injections of modified vaccinia Ankara (MVA) expressing H3N2 nucleoprotein (NP) and matrix protein 1 (M1) at 1·5 × 108 plaque forming units (4·3 × 108 50% tissue culture infectious dose [TCID50]; MVA-NP+M1 group) or saline placebo (placebo group). At least 6 weeks later, participants were challenged intranasally with 0·5 mL of a 1 × 106 TCID50/mL dose of influenza A/Belgium/4217/2015 (H3N2). Nasal swabs were collected twice daily from day 2 until day 11 for viral PCR, and symptoms of influenza were recorded from day 2 until day 11. The primary outcome was to determine the efficacy of MVA-NP+M1 vaccine to reduce the degree of nasopharyngeal viral shedding as measured by the cumulative viral area under the curve using a log-transformed quantitative PCR. This study is registered with ClinicalTrials.gov, NCT03883113.

FINDINGS

Between May 2 and Oct 24, 2019, 145 volunteers were enrolled and randomly assigned to the MVA-NP+M1 group (n=87) or the placebo group (n=58). Of these, 118 volunteers entered the challenge period (71 in the MVA-NP+M1 group and 47 in the placebo group) and 117 participants completed the study (71 in the MVA-NP+M1 group and 46 in the placebo group). 78 (54%) of the 145 volunteers were female and 67 (46%) were male. The primary outcome, overall viral load as determined by quantitative PCR, did not show a statistically significant difference between the MVA-NP+M1 (mean 649·7 [95% CI 552·7-746·7) and placebo groups (mean 726·1 [604·0-848·2]; p=0·17). All reported treatment emergent adverse events (TEAEs; 11 in the vaccination phase and 51 in the challenge phase) were grade 1 and 2, except for two grade 3 TEAEs in the placebo group in the challenge phase. A grade 4 second trimester fetal death, considered possibly related to the MVA-NP+M1 vaccination, and an acute psychosis reported in a placebo participant during the challenge phase were reported.

INTERPRETATION

The use of an MVA vaccine to expand CD4+ or CD8+ T cells to conserved influenza A antigens in peripheral blood did not affect nasopharyngeal viral load in an influenza H3N2 challenge model in seronegative, healthy adults.

FUNDING

Department of Health and Human Services; Administration for Strategic Preparedness and Response; Biomedical Advanced Research and Development Authority; and Barinthus Biotherapeutics.

Constant regulation for stable CD8 T-cell functional avidity and its possible implications for cancer immunotherapy

The functional avidity (FA) of cytotoxic CD8 T cells impacts strongly on their functional capabilities and correlates with protection from infection and cancer. FA depends on TCR affinity, downstream signaling strength, and TCR affinity-independent parameters of the immune synapse, such as costimulatory and inhibitory receptors. The functional impact of coreceptors on FA remains to be fully elucidated. Despite its importance, FA is infrequently assessed and incompletely understood. There is currently no consensus as to whether FA can be enhanced by optimized vaccine dose or boosting schedule. Recent findings suggest that FA is remarkably stable in vivo, possibly due to continued signaling modulation of critical receptors in the immune synapse. In this review, we provide an overview of the current knowledge and hypothesize that in vivo, codominant T cells constantly "equalize" their FA for similar function. We present a new model of constant FA regulation, and discuss practical implications for T-cell-based cancer immunotherapy.

Toward QbD Process Understanding on DNA Vaccine Purification Using Design of Experiment

DNA vaccines, the third generation of vaccines, are a promising therapeutic option for many diseases as they offer the customization of their ability on protection and treatment with high stability. The production of DNA vaccines is considered rapid and less complicated compared to others such as mRNA vaccines, viral vaccines, or subunit protein vaccines. However, the main issue for DNA vaccines is how to produce the active DNA, a supercoiled isoform, to comply with the regulations. Our work therefore focuses on gaining a process understanding of the purification step which processes parameters that have impacts on the critical quality attribute (CQA), supercoiled DNA and performance attribute (PA), and step yield. Herein, pVax1/lacZ was used as a model. The process parameters of interest were sample application flow rates and salt concentration at washing step and at elution step in the hydrophobic interaction chromatography (HIC). Using a Design of Experiment (DoE) with central composite face centered (CCF) approach, 14 experiments plus four additional runs at the center points were created. The response data was used to establish regression predictive models and simulation was conducted in 10,000 runs to provide tolerance intervals of these CQA and PA. The approach of this process understanding can be applied for Quality by Design (QbD) on other DNA vaccines and on a larger production scale as well.

Process Characterization by Definitive Screening Design Approach on DNA Vaccine Production

Plasmid DNA is a vital biological tool for molecular cloning and transgene expression of recombinant proteins; however, decades ago, it has become an exceptionally appealing as a potential biopharmaceutical product as genetic immunization for animal and human use. The demand for large-quantity production of DNA vaccines also increases. Thus, we, herein, presented a systematic approach for process characterization of fed-batch Escherichia coli DH5α fermentation producing a porcine DNA vaccine. Design of Experiments (DoE) was employed to determine process parameters that have impacts on a critical quality attribute of the product, which is the active form of plasmid DNA referred as supercoiled plasmid DNA content, as well as the performance attributes, which are volumetric yield and specific yield from fermentation. The parameters of interest were temperature, pH, dissolved oxygen, cultivation time, and feed rate. Using the definitive-screening design, there were 16 runs, including 3 additional center points to create the predictive model, which then was used to simulate the operational ranges for capability analysis.

High Peptide Dose Vaccination Promotes the Early Selection of Tumor Antigen-Specific CD8 T-Cells of Enhanced Functional Competence

CD8 T-cell response efficiency critically depends on the TCR binding strength to peptide-MHC, i.e., the TCR binding avidity. A current challenge in onco-immunology lies in the evaluation of vaccine protocols selecting for tumor-specific T-cells of highest avidity, offering maximal immune protection against tumor cells and clinical benefit. Here, we investigated the impact of peptide and CpG/adjuvant doses on the quality of vaccine-induced CD8 T-cells in relation to binding avidity and functional responses in treated melanoma patients. Using TCR-pMHC binding avidity measurements combined to phenotype and functional assays, we performed a comprehensive study on representative tumor antigen-specific CD8 T-cell clones (n = 454) from seven patients vaccinated with different doses of Melan-A/ELA peptide (0.1 mg vs. 0.5 mg) and CpG-B adjuvant (1–1.3 mg vs. 2.6 mg). Vaccination with high peptide dose favored the early and strong in vivo expansion and differentiation of Melan-A-specific CD8 T-cells. Consistently, T-cell clones generated from those patients showed increased TCR binding avidity (i.e., slow off-rates and CD8 binding independency) readily after 4 monthly vaccine injections (4v). In contrast, the use of low peptide or high CpG-B doses required 8 monthly vaccine injections (8v) for the enrichment of anti-tumor T-cells with high TCR binding avidity and low CD8 binding dependency. Importantly, the CD8 binding-independent vaccine-induced CD8 T-cells displayed enhanced functional avidity, reaching a plateau of maximal function. Thus, T-cell functional potency following peptide/CpG/IFA vaccination may not be further improved beyond a certain TCR binding avidity limit. Our results also indicate that while high peptide dose vaccination induced the early selection of Melan-A-specific CD8 T-cells of increased functional competence, continued serial vaccinations also promoted such high-avidity T-cells. Overall, the systematic assessment of T-cell binding avidity may contribute to optimize vaccine design for improving clinical efficacy.

Enzyme-linked immunospot assay to monitor antigen-specific cellular immune responses in mouse tumor models

Critical to the advancement of tumor immunotherapy is the reliable identification of responders and the quantification of the tumor-specific immune response elicited by treatments. In this regard, Enzyme-Linked Immunospot assay (ELISpot) is an ideal monitoring technique due to its high sensitivity, ease of execution and cost-effectiveness. Originally developed for the enumeration of B cells secreting antigen-specific antibodies, ELISpot assay has been adapted to detect and quantify cytokine-secreting immune cells present at low frequency in a variety of biological samples, including blood, in response to antigen-specific stimuli. The above-mentioned features emphasize the role of ELISpot as valuable assay for translational research and clinical applications. In the present chapter, we will focus on the use of ELISpot assay for monitoring the tumor-specific effector responses induced by different treatments in preclinical models and will provide some protocols and technical hints for its application.

Deletion of A44L, A46R and C12L Vaccinia Virus Genes from the MVA Genome Improved the Vector Immunogenicity by Modifying the Innate Immune Response Generating Enhanced and Optimized Specific T-Cell Responses

MVA is an attenuated vector that still retains immunomodulatory genes. We have previously reported its optimization after deleting the C12L gene, coding for the IL-18 binding-protein. Here, we analyzed the immunogenicity of MVA vectors harboring the simultaneous deletion of A44L, related to steroid synthesis and A46R, a TLR-signaling inhibitor (MVAΔA44L-A46R); or also including a deletion of C12L (MVAΔC12L/ΔA44L-A46R). The absence of biological activities of the deleted genes in the MVA vectors was demonstrated. Adaptive T-cell responses against VACV epitopes, evaluated in spleen and draining lymph-nodes of C57Bl/6 mice at acute/memory phases, were of higher magnitude in those animals that received deleted MVAs compared to MVAwt. MVAΔC12L/ΔA44L-A46R generated cellular specific memory responses of higher quality characterized by bifunctionality (CD107a/b⁺/IFN-γ⁺) and proliferation capacity. Deletion of selected genes from MVA generated innate immune responses with higher levels of determining cytokines related to T-cell response generation, such as IL-12, IFN-γ, as well as IL-1β and IFN-β. This study describes for the first time that simultaneous deletion of the A44L, A46R and C12L genes from MVA improved its immunogenicity by enhancing the host adaptive and innate immune responses, suggesting that this approach comprises an appropriate strategy to increase the MVA vaccine potential.

STING activator c-di-GMP enhances the anti-tumor effects of peptide vaccines in melanoma-bearing mice

Therapeutic vaccines to induce anti-tumor CD8 T cells have been used in clinical trials for advanced melanoma patients, but the clinical response rate and overall survival time have not improved much. We believe that these dismal outcomes are caused by inadequate number of antigen-specific CD8 T cells generated by most vaccines. In contrast, huge CD8 T cell responses readily occur during acute viral infections. High levels of type-I interferon (IFN-I) are produced during these infections, and this cytokine not only exhibits anti-viral activity but also promotes CD8 T cell responses. The studies described here were performed to determine whether promoting the production of IFN-I could enhance the potency of a peptide vaccine. We report that cyclic diguanylate monophosphate (c-di-GMP), which activates the stimulator of interferon genes, potentiated the immunogenicity and anti-tumor effects of a peptide vaccine against mouse B16 melanoma. The synergistic effects of c-di-GMP required co-administration of costimulatory anti-CD40 antibody, the adjuvant poly-IC, and were mediated in part by IFN-I. These findings demonstrate that peptides representing CD8 T cell epitopes can be effective inducers of large CD8 T cell responses in vaccination strategies that mimic acute viral infections.

HLA-A*31 as a marker of genetic susceptibility to sepsis

Objective

The HLA haplotype has been associated with many autoimmune diseases, but no associations have been described in sepsis. This study aims to investigate the HLA system as a possible marker of genetic sepsis susceptibility.

Methods

This is a prospective cohort study including patients admitted to an intensive care unit and healthy controls from a list of renal transplant donors. Patients with less 18 years of age; pregnant or HIV positive patients; those with metastatic malignancies or receiving chemotherapy; or with advanced liver disease; or with end-of-life conditions were excluded. The DNA was extracted from the whole blood and HLA haplotypes determined using MiliPlex^® technology.

Results

From October 2010 to October 2012, 1,121 patients were included (1,078 kidney donors, 20 patients admitted with severe sepsis and 23 with septic shock). HLA-A*31 positive subjects had increased risk of developing sepsis (OR 2.36, 95%CI 1.26-5.35). Considering a p value <0.01, no other significant association was identified.

Conclusion

HLA-A*31 expression is associated to risk of developing sepsis.

Vitiligo-like depigmentation in patients with stage III-IV melanoma receiving immunotherapy and its association with survival: a systematic review and meta-analysis

PURPOSE

Vitiligo-like depigmentation in patients with melanoma may be associated with more favorable clinical outcome. We conducted a systematic review of patients with stage III to IV melanoma treated with immunotherapy to determine the cumulative incidence of vitiligo-like depigmentation and the prognostic value of vitiligo development on survival.

METHODS

We systemically searched and selected all studies on melanoma immunotherapy that reported on autoimmune toxicity and/or vitiligo between 1995 and 2013. Methodologic quality of each study was appraised using adapted criteria for systematic reviews in prognostic studies. Random-effect models were used to calculate summary estimates of the cumulative incidence of vitiligo-like depigmentation across studies. The prognostic value of vitiligo-like depigmentation on survival outcome was assessed using random-effects Cox regression survival analyses.

RESULTS

One hundred thirty-seven studies were identified comprising 139 treatment arms (11 general immune stimulation, 84 vaccine, 28 antibody-based, and 16 adoptive transfer) including a total of 5,737 patients. The overall cumulative incidence of vitiligo was 3.4% (95% CI, 2.5% to 4.5%). In 27 studies reporting individual patient data, vitiligo development was significantly associated with both progression-free-survival (hazard ratio [HR], 0.51; 95% CI, 0.32 to 0.82; P < .005) and overall survival (HR, 0.25; 95% CI, 0.10 to 0.61; P < .003), indicating that these patients have two to four times less risk of disease progression and death, respectively, compared with patients without vitiligo development.

CONCLUSION

Although vitiligo occurs only in a low percentage of patients with melanoma treated with immunotherapy, our findings suggest clear survival benefit in these patients. Awareness of vitiligo induction in patients with melanoma is important as an indicator of robust antimelanoma immunity and associated improved survival.

Trial watch: DNA vaccines for cancer therapy

The foundation of modern vaccinology dates back to the 1790s, when the English physician Edward Jenner uncovered the tremendous medical potential of prophylactic vaccination. Jenner’s work ignited a wave of nationwide vaccination campaigns abating the incidence of multiple life-threatening infectious diseases and culminating with the eradication of natural smallpox virus, which was definitively certified by the WHO in 1980. The possibility of using vaccines against cancer was first proposed at the end of the 19th century by Paul Ehrlich and William Coley. However, it was not until the 1990s that such a hypothesis began to be intensively investigated, following the realization that the immune system is not completely unresponsive to tumors and that neoplastic cells express immunogenic tumor-associated antigens (TAAs). Nowadays, anticancer vaccines are rapidly moving from the bench to the bedside, and a few prophylactic and therapeutic preparations have already been approved by FDA for use in humans. In this setting, one interesting approach is constituted by DNA vaccines, i.e., TAA-encoding circularized DNA constructs, often of bacterial origin, that are delivered to patients as such or by means of specific vectors, including (but not limited to) liposomal preparations, nanoparticles, bacteria and viruses. The administration of DNA vaccines is most often performed via the intramuscular or subcutaneous route and is expected to cause (1) the endogenous synthesis of the TAA by myocytes and/or resident antigen-presenting cells; (2) the presentation of TAA-derived peptides on the cell surface, in association with MHC class I molecules; and (3) the activation of potentially therapeutic tumor-specific immune responses. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating DNA vaccines as therapeutic interventions against cancer.

Is the "3+3" dose-escalation phase I clinical trial design suitable for therapeutic cancer vaccine development? A recommendation for alternative design

PURPOSE

Phase I clinical trials are generally conducted to identify the maximum tolerated dose (MTD) or the biologically active dose (BAD) using a traditional dose-escalation design. This design may not be applied to cancer vaccines, given their unique mechanism of action. The FDA recently published "Guidance for Industry: Clinical Considerations for Therapeutic Cancer Vaccines." However, many questions about the design of cancer vaccine studies remain unanswered.

EXPERIMENTAL DESIGN

We analyzed the toxicity profile in 239 phase I therapeutic cancer vaccine trials. We addressed the ability of dose escalation to determine the MTD or the BAD in trials that used a dose-escalation design.

RESULTS

The rate of grade 3/4 vaccine-related systemic toxicities was 1.25 adverse events per 100 patients and 2 per 1,000 vaccines. Only two of the 127 dose-escalation trials reported vaccine-related dose limiting toxicities, both of which used bacterial vector vaccines. Out of the 116 trials analyzed for the dose-immune response relationship, we found a statistically significant dose-immune response correlation only when the immune response was measured by antibodies (P < 0.001) or delayed type hypersensitivity (P < 0.05). However, the increase in cellular immune response did not appear further sustainable with the continued increase in dose.

CONCLUSIONS

Our analysis suggests that the risks of serious toxicities with therapeutic cancer vaccines are extremely low and that toxicities do not correlate with dose levels. Accordingly, the conventional dose-escalation design is not suitable for cancer vaccines with few exceptions. Here, we propose an alternative design for therapeutic cancer vaccine development.

Preclinical and clinical development of DNA vaccines for prostate cancer

Prostate cancer is the most commonly diagnosed cancer in the United States. It is also the second leading cause of cancer-related death in men, making it one of the largest public health concerns today. Prostate cancer is an ideal disease for immunotherapies because of the generally slow progression, the dispensability of the target organ in the patient population, and the availability of several tissue-specific antigens. As such, several therapeutic vaccines have entered clinical trials, with one autologous cellular vaccine (sipuleucel-T) recently gaining Food and Drug Administration approval after demonstrating overall survival benefit in randomized phase III clinical trials. DNA-based vaccines are safe, economical, alternative "off-the-shelf" approaches that have undergone extensive evaluation in preclinical models. In fact, the first vaccine approved in the United States for the treatment of cancer was a DNA vaccine for canine melanoma. Several prostate cancer-specific DNA vaccines have been developed in the last decade and have shown promising results in early phase clinical trials. This review summarizes anticancer human DNA vaccine trials, with a focus on those conducted for prostate cancer. We conclude with an outline of special considerations important for the development and successful translation of DNA vaccines from the laboratory to the clinic.

Elements in the Development of a Production Process for Modified Vaccinia Virus Ankara

The production of several viral vaccines depends on chicken embryo fibroblasts or embryonated chicken eggs. To replace this logistically demanding substrate, we created continuous anatine suspension cell lines (CR and CR.pIX), developed chemically-defined media, and established production processes for different vaccine viruses. One of the processes investigated in greater detail was developed for modified vaccinia virus Ankara (MVA). MVA is highly attenuated for human recipients and an efficient vector for reactogenic expression of foreign genes. Because direct cell-to-cell spread is one important mechanism for vaccinia virus replication, cultivation of MVA in bioreactors is facilitated if cell aggregates are induced after infection. This dependency may be the mechanism behind our observation that a novel viral genotype (MVA-CR) accumulates with serial passage in suspension cultures. Sequencing of a major part of the genomic DNA of the new strain revealed point mutations in three genes. We hypothesize that these changes confer an advantage because they may allow a greater fraction of MVA-CR viruses to escape the host cells for infection of distant targets. Production and purification of MVA-based vaccines may be simplified by this combination of designed avian cell line, chemically defined media and the novel virus strain.

Clinical applications of attenuated MVA poxvirus strain

The highly attenuated poxvirus strain modified vaccinia virus Ankara (MVA) has reached maturity as a vector delivery system and as a vaccine candidate against a broad spectrum of diseases. This has been largely recognized from research on virus-host cell interactions and immunological studies in pre-clinical and clinical trials. This review addresses the studies of MVA vectors used in phase I/II clinical trials, with the aim to provide the main findings obtained on their behavior when tested against relevant human diseases and cancer and also highlights the strategies currently implemented to improve the MVA immunogenicity. The authors assess that MVA vectors are progressing as strong vaccine candidates either alone or when administered in combination with other vectors.

Process development and production of cGMP grade Melan-A for cancer vaccine clinical trials

Melan-A is a cancer testis antigen commonly found in melanoma, and has been shown to stimulate the body's immune response against cancerous cells. We have developed and executed a process utilizing current good manufacturing practices (cGMP) to produce the 6 times-His tagged protein in C41DE3 Escherichia coli for use in Phase I clinical trials. Approximately 11 g of purified Melan-A were produced from a 20 L fed-batch fermentation. Purification was achieved through a three column process utilizing immobilized metal affinity, anion exchange, and cation exchange chromatography with a buffer system optimized for low-solubility, high LPS binding capacity proteins. The host cell proteins, residual DNA, and endotoxin concentration were well below limits for a prescribed dose with a final purity level of 91%.

Phase I trial of recombinant modified vaccinia ankara encoding Epstein-Barr viral tumor antigens in nasopharyngeal carcinoma patients

Epstein-Barr virus (EBV) is associated with several malignancies including nasopharyngeal carcinoma, a high incidence tumor in Chinese populations, in which tumor cells express the two EBV antigens EB nuclear antigen 1 (EBNA1) and latent membrane protein 2 (LMP2). Here, we report the phase I trial of a recombinant vaccinia virus, MVA-EL, which encodes an EBNA1/LMP2 fusion protein designed to boost T-cell immunity to these antigens. The vaccine was delivered to Hong Kong patients with nasopharyngeal carcinoma to determine a safe and immunogenic dose. The patients, all in remission more than 12 weeks after primary therapy, received three intradermal MVA-EL vaccinations at three weekly intervals, using five escalating dose levels between 5 × 10(7) and 5 × 10(8) plaque-forming unit (pfu). Blood samples were taken during prescreening, immediately before vaccination, one week afterward and at intervals up to one year later. Immunogenicity was tested by IFN-γ ELIspot assays using complete EBNA1 and LMP2 15-mer peptide mixes and known epitope peptides relevant to patient MHC type. Eighteen patients were treated, three per dose level one to four and six at the highest dose, without dose-limiting toxicity. T-cell responses to one or both vaccine antigens were increased in 15 of 18 patients and, in many cases, were mapped to known CD4 and CD8 epitopes in EBNA1 and/or LMP2. The range of these responses suggested a direct relationship with vaccine dose, with all six patients at the highest dose level giving strong EBNA1/LMP2 responses. We concluded that MVA-EL is both safe and immunogenic, allowing the highest dose to be forwarded to phase II studies examining clinical benefit.

Protective CD8+ T-cell immunity to human malaria induced by chimpanzee adenovirus-MVA immunisation

Induction of antigen-specific CD8(+) T cells offers the prospect of immunization against many infectious diseases, but no subunit vaccine has induced CD8(+) T cells that correlate with efficacy in humans. Here we demonstrate that a replication-deficient chimpanzee adenovirus vector followed by a modified vaccinia virus Ankara booster induces exceptionally high frequency T-cell responses (median >2400 SFC/10(6) peripheral blood mononuclear cells) to the liver-stage Plasmodium falciparum malaria antigen ME-TRAP. It induces sterile protective efficacy against heterologous strain sporozoites in three vaccinees (3/14, 21%), and delays time to patency through substantial reduction of liver-stage parasite burden in five more (5/14, 36%), P=0.008 compared with controls. The frequency of monofunctional interferon-γ-producing CD8(+) T cells, but not antibodies, correlates with sterile protection and delay in time to patency (P(corrected)=0.005). Vaccine-induced CD8(+) T cells provide protection against human malaria, suggesting that a major limitation of previous vaccination approaches has been the insufficient magnitude of induced T cells.

Analysis of pre-treatment markers predictive of treatment benefit for the therapeutic cancer vaccine MVA-5T4 (TroVax)

Cancer vaccines such as MVA-5T4 (TroVax(®)) must induce an efficacious immune response to deliver therapeutic benefit. The identification of biomarkers that impact on the clinical and/or immunological efficacy of cancer vaccines is required in order to select patients who are most likely to benefit from this treatment modality. Here, we sought to identify a predictor of treatment benefit for renal cancer patients treated with MVA-5T4. Statistical modeling was undertaken using data from a phase III trial in which patients requiring first-line treatment for metastatic renal cell carcinoma were randomized 1:1 to receive MVA-5T4 or placebo alongside sunitinib, IL-2 or IFN-α. Numerous pre-treatment factors associated with inflammatory anemia (e.g., CRP, hemoglobin, hematocrit, IL-6, ferritin, platelets) demonstrated a significant relationship with tumor burden and patient survival. From these prognostic factors, the pre-treatment mean corpuscular hemoglobin concentration (MCHC) was found to be the best predictor of treatment benefit (P < 0.01) for MVA-5T4 treated patients and also correlated positively with tumor shrinkage (P < 0.001). Furthermore, MCHC levels showed a significant positive association with 5T4 antibody response (P = 0.01). The latter result was confirmed using an independent data set comprising phase II trials of MVA-5T4 in patients with colorectal, renal and prostate cancers. Retrospective analyses demonstrated that RCC patients who had very large tumor burdens and low MCHC levels received little or no benefit from treatment with MVA-5T4; however, patients with smaller tumor burdens and normal MCHC levels received substantial benefit from treatment with MVA-5T4.

Therapeutic cancer vaccines in prostate cancer: the quest for intermediate markers of response

Despite recent advances in cancer immunotherapy, no prospectively validated intermediate biomarkers exist to predict response. These biomarkers are highly desirable given modern immunotherapy's paradoxical pattern of clinical benefit; that is, improvement in overall survival without short-term change in progression. Immunotherapy clinical trials have evaluated biomarkers that may correlate with clinical outcomes. Many of them are performed on peripheral blood to evaluate the systemic response, such as tumor-targeted humoral and cellular immunity, and cytokine responses. Accumulating evidence suggests that immune infiltrates in tumors may suggest evidence for the therapy's mechanism of action, and have greater potential for providing prognostic and predictive information. In addition, a non-immunologic biomarker, such as tumor growth kinetics, may explain this paradoxical pattern of clinical benefit, and predict survival in patients treated with an immunotherapy. Prospective assessment and validation of these and other intermediate markers would be required to better understand their potential clinical role.

Impact of anti-orthopoxvirus neutralizing antibodies induced by a heterologous prime-boost HIV-1 vaccine on insert-specific immune responses

BACKGROUND

The impact of anti-vector immunity on the elicitation of insert-specific immune responses is important to understand in vaccine development. HVTN 055 was a 150 person phase I randomized, controlled HIV vaccine trial of recombinant modified vaccinia Ankara (rMVA) and fowlpox (rFPV) with matched HIV-1 inserts which demonstrated increased CD8+ T-cell immune responses in the heterologous vaccine group. The controls used in this study were the empty vectors (MVA and FPV).

METHODS

Anti-MVA and anti-vaccinia neutralizing antibodies (NAbs) were measured and compared with cellular and humoral HIV-1-specific immune responses.

RESULTS

Elicitation of anti-vector responses increased with increasing dose of MVA and up to 2 administrations. Further inoculations of MVA (up to 5) did not increase the magnitude of the anti-MVA response but did delay the anti-vector NAb titre decay. There was no evidence that the insert impaired the anti-vector response, nor that anti-vector immunity attenuated the insert-specific responses.

CONCLUSION

Two doses of MVA may be ideal for the elicitation of orthopoxvirus immune responses with further doses maintaining increased titres against the vector. We found no evidence that eliciting HIV insert- or MVA vector-specific immune responses interfered with elicitation of immune responses to the other.

Deletion of specific immune-modulatory genes from modified vaccinia virus Ankara-based HIV vaccines engenders improved immunogenicity in rhesus macaques

Modified vaccinia virus Ankara (MVA) is a safe, attenuated orthopoxvirus that is being developed as a vaccine vector but has demonstrated limited immunogenicity in several early-phase clinical trials. Our objective was to rationally improve the immunogenicity of MVA-based HIV/AIDS vaccines via the targeted deletion of specific poxvirus immune-modulatory genes. Vaccines expressing codon-optimized HIV subtype C consensus Env and Gag antigens were generated from MVA vector backbones that (i) harbor simultaneous deletions of four viral immune-modulatory genes, encoding an interleukin-18 (IL-18) binding protein, an IL-1β receptor, a dominant negative Toll/IL-1 signaling adapter, and CC-chemokine binding protein (MVAΔ4-HIV); (ii) harbor a deletion of an additional (fifth) viral gene, encoding uracil-DNA glycosylase (MVAΔ5-HIV); or (iii) represent the parental MVA backbone as a control (MVA-HIV). We performed head-to-head comparisons of the cellular and humoral immune responses that were elicited by these vectors during homologous prime-boost immunization regimens utilizing either high-dose (2 × 10(8) PFU) or low-dose (1 × 10(7) PFU) intramuscular immunization of rhesus macaques. At all time points, a majority of the HIV-specific T cell responses, elicited by all vectors, were directed against Env, rather than Gag, determinants, as previously observed with other vector systems. Both modified vectors elicited up to 6-fold-higher frequencies of HIV-specific CD8 and CD4 T cell responses and up to 25-fold-higher titers of Env (gp120)-specific binding (nonneutralizing) antibody responses that were relatively transient in nature. While the correlates of protection against HIV infection remain incompletely defined, our results indicate that the rational deletion of specific genes from MVA vectors can positively alter their cellular and humoral immunogenicity profiles in nonhuman primates.

Genetic cancer vaccines: current status and perspectives

INTRODUCTION

The recent approval of the first therapeutic cancer vaccine by the US Regulatory Agency represents a breakthrough event in the history of cancer treatment. The past scepticism towards this type of therapeutic intervention is now replaced by great expectations. The field is now moving towards the development of alternative vaccination technologies, which are capable of generating stronger, more durable and efficient immune responses against specific tumour-associated antigens (TAAs) in combination with cheaper and more standardised manufacturing.

AREAS COVERED

In this context, genetic vaccines are emerging among the most promising methodologies. Several evidences point to combinations of different genetic immunisation modalities (heterologous prime/boost) as a powerful approach to induce superior immune responses and achieve greater clinical efficacy. In this review, we provide an overview of the current status of development of genetic cancer vaccines with particular emphasis on adenoviral vector prime/DNA boost vaccination schedules.

EXPERT OPINION

We believe that therapeutic genetic cancer vaccines have the strong potential to become an established therapeutic modality for cancer in next coming years, in a manner similar to what have now become monoclonal antibodies.

Vaccinia viruses: vaccines against smallpox and vectors against infectious diseases and tumors

Less than 200 years after its introduction, widespread use of vaccinia virus (VACV) as a smallpox vaccine has eradicated variola virus. Along with the remarkable success of the vaccination program, frequent and sometimes severe adverse reactions to VACV were encountered. After eradication, VACV has been reserved for select populations who might be at significant risk for orthopoxvirus infections. Events over the past decade have renewed concerns over the potential use of variola virus as a biological weapon. Accordingly, interest in VACV and attenuated derivatives has increased, both as vaccines against smallpox and as vectors for other vaccines. This article will focus on new developments in the field of orthopoxvirus immunization and will highlight recent advances in the use of vaccinia viruses as vectors for infectious diseases and malignancies.

On the future of HLA

As the immunobiological function of the HLA (human leucocyte antigen) class I and II molecules was revealed, we have seen an explosive development of the HLA field. Today, the HLA complex occupies a central position in basic and clinical immunology. In this Opinion article, I will briefly discuss some challenges which in my opinion are more important than others in the near future of HLA, with a focus on products of the classical HLA class I and II genes. Matching for HLA antigens will continue to be of importance in organ and hematopoietic stem cell transplantations. In the latter field, induction of graft-versus-leukemia effects will receive greater attention, where HLA will play a central role. It is anticipated that we will see an extensive development in our knowledge of the etiology and pathogenesis of autoimmune diseases, where some HLA class I and II genes by far are the strongest predisposing genes. To predict and prevent autoimmune diseases will be a major challenge for the HLA field in the future. HLA will also be of increasing importance in pharmacogenomics, vaccinations and anthropology. Together, this will leave the HLA field with many new challenges and opportunities, which in the future will require more focus on functional aspects of the immunogenetics of HLA.

Elevated tumor-associated antigen expression suppresses variant peptide vaccine responses

Variant peptide vaccines are used clinically to expand T cells that cross-react with tumor-associated Ags (TAA). To investigate the effects of elevated endogenous TAA expression on variant peptide-induced responses, we used the GP70 TAA model. Although young BALB/c mice display T cell tolerance to the TAA GP70(423-431) (AH1), expression of GP70 and suppression of AH1-specific responses increases with age. We hypothesized that as TAA expression increases, the AH1 cross-reactivity of variant peptide-elicited T cell responses diminishes. Controlling for immunosenescence, we showed that elevated GP70 expression suppressed AH1 cross-reactive responses elicited by two AH1 peptide variants. A variant that elicited almost exclusively AH1 cross-reactive T cells in young mice elicited few or no T cells in aging mice with Ab-detectable GP70 expression. In contrast, a variant that elicited a less AH1 cross-reactive T cell response in young mice successfully expanded AH1 cross-reactive T cells in all aging mice tested. However, these T cells bound the AH1/MHC complex with a relatively short half-life and responded poorly to ex vivo stimulation with the AH1 peptide. Variant peptide vaccine responses were also suppressed when AH1 peptide is administered tolerogenically to young mice before vaccination. Analyses of variant-specific precursor T cells from naive mice with Ab-detectable GP70 expression determined that these T cells expressed PD-1 and had downregulated IL-7Rα expression, suggesting they were anergic or undergoing deletion. Although variant peptide vaccines were less effective as TAA expression increases, data presented in this article also suggest that complementary immunotherapies may induce the expansion of T cells with functional TAA recognition.

Recommendations from the iSBTc-SITC/FDA/NCI Workshop on Immunotherapy Biomarkers

PURPOSE

To facilitate development of innovative immunotherapy approaches, especially for treatment concepts exploiting the potential benefits of personalized therapy, there is a need to develop and validate tools to identify patients who can benefit from immunotherapy. Despite substantial effort, we do not yet know which parameters of antitumor immunity to measure and which assays are optimal for those measurements.

EXPERIMENTAL DESIGN

The iSBTc-SITC (International Society for Biological Therapy of Cancer-Society for Immunotherapy of Cancer), FDA (Food and Drug Administration), and NCI (National Cancer Institute) partnered to address these issues for immunotherapy of cancer. Here, we review the major challenges, give examples of approaches and solutions, and present our recommendations.

RESULTS AND CONCLUSIONS

Although specific immune parameters and assays are not yet validated, we recommend following standardized (accurate, precise, and reproducible) protocols and use of functional assays for the primary immunologic readouts of a trial; consideration of central laboratories for immune monitoring of large, multi-institutional trials; and standardized testing of several phenotypic and functional potential potency assays specific to any cellular product. When reporting results, the full QA (quality assessment)/QC (quality control) should be conducted and selected examples of truly representative raw data and assay performance characteristics should be included. Finally, to promote broader analysis of multiple aspects of immunity, and gather data on variability, we recommend that in addition to cells and serum, RNA and DNA samples be banked (under standardized conditions) for later testing. We also recommend that sufficient blood be drawn to allow for planned testing of the primary hypothesis being addressed in the trial, and that additional baseline and posttreatment blood is banked for testing novel hypotheses (or generating new hypotheses) that arise in the field.

Pilot study of 1650-G: a simplified cellular vaccine for lung cancer

INTRODUCTION

Cancer immunotherapy is a conceptually attractive since it is highly specific and can deal with disseminated disease with minimal impact on normal tissues. Early phase clinical trials have well established the ability of a variety of immunotherapeutic approaches to induce antigen specific immune responses in lung cancer patients. Although no immunotherapy is likely to be a panacea, recent data from randomized phase IIB studies offer promise of therapeutic activity in both early and late stage lung cancer.

METHODS

This report describes early clinical experience with vaccine 1650-G, an allogeneic cellular vaccine using granulocyte macrophage colony stimulating factor as an adjuvant. This nonrandomized pilot study was conducted at four sites in the Commonwealth of Kentucky with primary objective of determining biological activity in a relevant patient population; the use of similar antigen source, immunization schedule, and immunological assessment facilitated comparison to DC vaccines previously tested by our group.

RESULTS

Data indicates 1650-G is safe and generated a robust and unequivocal immunological response in 6/11 of immunized patients. The relative frequency and kinetics of the response appears similar to that achieved with DC vaccines (1650+autologous DC). The fact that this vaccine could be transported and delivered to cancer patients in community cancer clinics also fulfills an important objective of our research.

CONCLUSIONS

These findings provide critical foundation for further testing of this simple, and comparatively inexpensive multivalent NSCLC vaccine.

Programmed cell death-1 (PD-1) at the heart of heterologous prime-boost vaccines and regulation of CD8+ T cell immunity

Developing new vaccination strategies and optimizing current vaccines through heterologous prime-boost carries the promise of integrating the benefits of different yet synergistic vectors. It has been widely thought that the increased immunity afforded by heterologous prime-boost vaccination is mainly due to the minimization of immune responses to the carrier vectors, which allows a progressive build up of immunity against defined epitopes and the subsequent induction of broader immune responses against pathogens. Focusing on CD8⁺ T cells, we put forward a different yet complementary hypothesis based primarily on the systematic analysis of DNA vaccines as priming agents. This hypothesis relies on the finding that during the initiation of immune response, acquisition of co-inhibitory receptors such as programmed cell death-1 (PD-1) is determined by the pattern of antigen exposure in conjunction with Toll-like receptor (TLR)-dependent stimulation, critically affecting the magnitude and profile of secondary immunity. This hypothesis, based upon the acquisition and co-regulation of pivotal inhibitory receptors by CD8⁺ T cells, offers a rationale for gene-based immunization as an effective priming strategy and, in addition, outlines a new dimension to immune homeostasis during immune reaction to pathogens. Finally, this model implies that new and optimized immunization approaches for cancer and certain viral infections must induce highly efficacious T cells, refractory to a broad range of immune-inhibiting mechanisms, rather than solely or primarily focusing on the generation of large pools of vaccine-specific lymphocytes.

A new insight into hepatitis C vaccine development

Chronic hepatitis C virus (HCV) infection remains a serious burden to public health worldwide. Currently, HCV-infected patients could undergo antiviral therapy by giving pegylated IFN-α with ribavirin. However, this therapy is only effective in around 50% of patients with HCV genotype 1, which accounts for more than 70% of all HCV infection, and it is not well tolerated for most patients. Moreover, there is no vaccine available. The efforts on identifying protective immunity against HCV have progressed recently. Neutralizing antibodies and robust T cell responses including both CD4⁺ and CD8⁺ have been shown to be related to the clearance of HCV, which have shed lights on the potential success of HCV vaccines. There are many vaccines developed and tested before entering clinical trials. Here, we would first discuss strategies of viral immune evasion and correlates of protective host immunity and finally review some prospective vaccine approaches against chronic HCV infection.