Vaccine-induced T-cell Responses Research Articles

Final Results from a Cancer Research Uk First in Man Phase I Trial of Ima950 (A Novel Multi Peptide Vaccine) Plus Gm-Csf in Patients with Newly Diagnosed Glioblastoma

ABSTRACT Background IMA950 is a novel multi-peptide glioblastoma (GBM) specific vaccine that contains 11 HLA binding tumour associated peptides (TUMAPs), identified on human leukocyte antigen (HLA) surface receptors in primary human GBM tissue, and one viral (HBV) marker peptide. The TUMAPs are designed to activate TUMAP-specific CD8+ cytotoxic and CD4+ helper T lymphocytes, which then recognise cognate TUMAPs presented by GBM tumour cells and effect a targeted immune response. Methods Patients (pts) must be eligible for standard treatment of newly diagnosed GBM (maximal safe tumour resection, concomitant chemoradiotherapy (CRT) and adjuvant temozolomide (TMZ)) and be HLA-A*02 positive with no history of autoimmune disease. Vaccination comprises IMA950 plus GM-CSF injected intradermally at 11 time points over a 24 week period. Up to 45 pts will be entered into one of two cohorts with similar schedules. In Cohort 1 vaccination begins 7 to 14 days prior to initial CRT; in Cohort 2 it begins at least 7 days post CRT and 28 days prior to adjuvant TMZ. Safety is assessed according to NCI CTCAE Version 4.0. Immune response is determined by HLA-multimer analysis of vaccine-induced Tcell response in PBMC samples. Secondary objectives include observation of any anti-tumour effects, measurement of pre-treatment regulatory T-cell levels and evaluation of the effect of steroid dose on observed T-cell responses. Results As of 21 May-12, 25 pts (12 in Cohort 1 and 13 in Cohort 2) have been recruited. Adverse events related to either IMA950 or GM-CSF have been restricted to minor injection site reactions, a single distant allergic rash and a case of isolated asymptomatic neutropenia. Eleven pts have been analysed for immune response with 10 being evaluable (6 from Cohort 1 and 4 from Cohort 2). Eight pts responded to the HBV marker peptide, 8 pts to at least one TUMAP and 4 pts to multiple TUMAPs; 100% of pts in Cohort 2 responded to at least one TUMAP and 50% to multiple TUMAPs. Conclusion IMA950 plus GMCSF given alongside standard treatment for GBM has been well tolerated to date and these results already give encouragement for further development of this vaccine. Disclosure H. Singh-Jasuja: Harpreet Singh-Jasuja is a Founder and the Chief Scientific Officer of Immatics Biotechnologies GmbH. He also has stock or ownership stakes to disclose. All other authors have declared no conflicts of interest.

Strong vaccine-induced CD8 T-cell responses have cytolytic function in a chimpanzee clearing HCV infection.

A single correlate of effective vaccine protection against chronic HCV infection has yet to be defined. In this study, we analyzed T-cell responses in four chimpanzees, immunized with core-E1-E2-NS3 and subsequently infected with HCV1b. Viral clearance was observed in one animal, while the other three became chronically infected. In the animal that cleared infection, NS3-specific CD8 T-cell responses were observed to be more potent in terms of frequency and polyfunctionality of cytokine producing cells. Unique to this animal was the presence of killing-competent CD8 T-cells, specific for NS31258–1272, being presented by the chimpanzee MHC class I molecule Patr-A*03∶01, and a high affinity recognition of this epitope. In the animals that became chronically infected, T-cells were able to produce cytokines against the same peptide but no cytolysis could be detected. In conclusion, in the animal that was able to clear HCV infection not only cytokine production was observed but also cytolytic potential against specific MHC class I/peptide-combinations.

Vaccination with Gag, Vif, and Nef gene fragments affords partial control of viral replication after mucosal challenge with SIVmac239.

Broadly targeted cellular immune responses are thought to be important for controlling replication of human and simian immunodeficiency viruses (HIV and SIV). However, eliciting such responses by vaccination is complicated by immunodominance, the preferential targeting of only a few of the many possible epitopes of a given antigen. This phenomenon may be due to the coexpression of dominant and subdominant epitopes by the same antigen-presenting cell and may be overcome by distributing these sequences among several different vaccine constructs. Accordingly, we tested whether vaccinating rhesus macaques with "minigenes" encoding fragments of Gag, Vif, and Nef resulted in broadened cellular responses capable of controlling SIV replication. We delivered these minigenes through combinations of recombinant Mycobacterium bovis BCG (rBCG), electroporated recombinant DNA (rDNA) along with an interleukin-12 (IL-12)-expressing plasmid (EP rDNA plus pIL-12), yellow fever vaccine virus 17D (rYF17D), and recombinant adenovirus serotype 5 (rAd5). Although priming with EP rDNA plus pIL-12 increased the breadth of vaccine-induced T-cell responses, this effect was likely due to the improved antigen delivery afforded by electroporation rather than modulation of immunodominance. Indeed, Mamu-A*01(+) vaccinees mounted CD8(+) T cells directed against only one subdominant epitope, regardless of the vaccination regimen. After challenge with SIVmac239, vaccine efficacy was limited to a modest reduction in set point in some of the groups and did not correlate with standard T-cell measurements. These findings suggest that broad T-cell responses elicited by conventional vectors may not be sufficient to substantially contain AIDS virus replication. Immunodominance poses a major obstacle to the generation of broadly targeted, HIV-specific cellular responses by vaccination. Here we attempted to circumvent this phenomenon and thereby broaden the repertoire of SIV-specific cellular responses by vaccinating rhesus macaques with minigenes encoding fragments of Gag, Vif, and Nef. In contrast to previous mouse studies, this strategy appeared to minimally affect monkey CD8(+) T-cell immundominance hierarchies, as seen by the detection of only one subdominant epitope in Mamu-A*01(+) vaccinees. This finding underscores the difficulty of inducing subdominant CD8(+) T cells by vaccination and demonstrates that strategies other than gene fragmentation may be required to significantly alter immunodominance in primates. Although some of the regimens tested here were extremely immunogenic, vaccine efficacy was limited to a modest reduction in set point viremia after challenge with SIVmac239. No correlates of protection were identified. These results reinforce the notion that vaccine immunogenicity does not predict control of AIDS virus replication.

Safety and immunogenicity of therapeutic DNA vaccine with antiviral drug in chronic HBV patients and its immunogenicity in mice

Here, we evaluated the safety and immunogenicity of hepatitis B virus (HBV) DNA vaccine, HB-110, in mice and Korean patients with chronic hepatitis B (CHB) undergoing adefovir dipivoxil (ADV) treatment. For animal study, mice (BALB/c or HBV transgenic) were immunized with mHB-110, and T-cell and antibody responses were evaluated. For clinical study, 27 patients randomly received either ADV alone or ADV in combination with HB-110. Liver function tests, serum HBV DNA levels and the presence of HBeAg/anti-HBe were analysed. T-cell responses were estimated by ELISPOT and FACS analysis. mHB-110 induced higher T-cell and antibody responses than mHB-100 in mice. No adverse effects were observed by HB-110 cotreated with ADV. HBV-specific T-cell responses were induced in a portion of patients in medium to high dose of HB-110. Interestingly, HB-110 exhibited positive effects on ALT normalization and maintenance of HBeAg seroconversion. One patient, who received high dose of HB-110 exhibited HBeAg seroconversion during vaccination, which correlated with vaccine-induced T-cell responses without ALT elevation. HB-110 was safe and tolerable in CHB patients. In contrast to results in animal models, HB-110 in Korean patients exhibited weaker capability of inducing HBV-specific T-cell responses and HBeAg seroconversion than HB-100 in Caucasian patients. As Asian patients, who are generally infected via vertical transmission, appeared to have higher level of immune tolerance than Caucasian, novel approaches for breaking immune tolerance rather than enhancing immunogenicity may be more urgently demanded to develop effective therapeutic HBV DNA vaccines.

Characterization of T-cell responses to cryptic epitopes in recipients of a noncodon-optimized HIV-1 vaccine.

Cryptic epitopes (CEs) can be encoded by any of the 5 alternative reading frames (ARFs, 2 sense and 3 antisense) of a known gene. Although CE responses are commonly detected during HIV-1 infection, it is not known whether these responses are induced after vaccination. Using a bioinformatic approach, we determined that vaccines with codon-optimized HIV inserts significantly skewed CE sequences and are not likely to induce crossreactive responses to natural HIV CE. We then evaluated the CE- and protein-specific T-cell responses using Gag, Pol, and ARF peptide pools among participants immunized with a non-codon optimized vaccine regimen of 2 pGA2/JS7 DNA primes followed by 2 MVA/HIV62 Gag-Pol-Env vector boosts or 4 saline injections. Vaccinees had significantly more interferon gamma enzyme-linked immunosorbent spot (IFNγ ELISpot) responses toward Gag (P = 0.003) but not toward Pol protein than did placebo recipients. However, CE-specific T-cell responses were low in magnitude, and their frequencies did not differ significantly between vaccine and placebo recipients. Additionally, most positive CE responses could not be mapped to individual peptides. After expanding responses in a cultured assay, however, the frequency and the median magnitude of responses to ARF peptides were significantly greater in vaccinees (P < 0.0001), indicating that CE-specific T-cell responses are present but below an ex vivo assay's limit of detection. Our data demonstrate that HIV-1 vaccines currently in clinical trials are poorly immunogenic with regard to CE-specific T-cell responses. Therefore, the context of HIV-1 immunogens may need to be modified as a comprehensive strategy to broaden vaccine-induced T-cell responses.

Immunotherapy-induced CD8+ T Cells Instigate Immune Suppression in the Tumor

Despite clear evidence of immunogenicity, cancer vaccines only provide a modest clinical benefit. To evaluate the mechanisms that limit tumor regression following vaccination, we have investigated the weak efficacy of a highly immunogenic experimental vaccine using a murine melanoma model. We discovered that the tumor adapts rapidly to the immune attack instigated by tumor-specific CD8+ T cells in the first few days following vaccination, resulting in the upregulation of a complex set of biological networks, including multiple immunosuppressive processes. This rapid adaptation acts to prevent sustained local immune attack, despite continued infiltration by increasing numbers of tumor-specific T cells. Combining vaccination with adoptive transfer of tumor-specific T cells produced complete regression of the treated tumors but did not prevent the adaptive immunosuppression. In fact, the adaptive immunosuppressive pathways were more highly induced in regressing tumors, commensurate with the enhanced level of immune attack. Examination of tumor infiltrating T-cell functionality revealed that the adaptive immunosuppression leads to a progressive loss in T-cell function, even in tumors that are regressing. These novel observations that T cells produced by therapeutic intervention can instigate a rapid adaptive immunosuppressive response within the tumor have important implications for clinical implementation of immunotherapies.

Distinct T-Cell Responses When BCG Vaccination Is Delayed From Birth to 6 Weeks of Age in Ugandan Infants

In Uganda, the tuberculosis vaccine BCG is administered on the first day of life. Infants delivered at home receive BCG vaccine at their first healthcare facility visit at 6 weeks of age. Our aim was to determine the effect of this delay in BCG vaccination on the induced immune response. We assessed CD4(+) and CD8(+) T-cell responses with a 12-hour whole-blood intracellular cytokine/cytotoxic marker assay, and with a 6-day proliferation assay. We enrolled 92 infants: 50 had received BCG vaccine at birth and 42 at 6 weeks of age. Birth vaccination was associated with (1) greater induction of CD4(+) and CD8(+) T cells expressing either interferon γ (IFN-γ) alone or IFN-γ together with perforin and (2) induction of proliferating cells that had greater capacity to produce IFN-γ, tumor necrosis factor α (TNF-α), and interleukin 2 together, compared with delayed vaccination. Distinct patterns of T-cell induction occurred when BCG vaccine was given at birth and at 6 weeks of age. We propose that this diversity might impact protection against tuberculosis. Our results differ from those of studies of delayed BCG vaccination in South Africa and the Gambia, suggesting that geographical and population heterogeneity may affect the BCG vaccine-induced T-cell response.

Will mosaic vaccine immunogens expand immune response breadth to rival HIV-1 strain diversity?

HIV-1 displays the most genetic diversity of any virus studied to date [1]. Within an infected individual, the virus constantly mutates, outpacing host immune responses and increasing the number of distinct isolates that may be transmitted. Contending with such extreme diversity poses an unprecedented challenge for HIV-1 vaccine development. Although few HIV-1 preventive vaccine efficacy trials have been conducted to date, thus far only partial efficacy in reducing infection risk has been observed in one study in a low-risk setting (RV144; vaccine efficacy = 30%) [2]. Serum binding antibodies specific for HIV-1 Env were shown to correlate with reduced infection risk in this study [3]. To date, no HIV-1 vaccine has definitively reduced viral load after infection or slowed disease progression. Expanding cellular and antibody immune response breadth will likely be necessary for achieving high levels of vaccine efficacy in the face of HIV-1’s extraordinary genetic diversity. The first HIV vaccines containing mosaic antigen inserts will enter human testing later this year. This approach represents one of several in silico-based strategies to increase the cross reactivity of vaccine responses for diverse HIV-1 isolates. The original aim of mosaic antigens was to expand vaccine cellular response breadth (number of responses to distinct T-cell epitopes) and depth (number of responses to a given T-cell epitope). In nonhuman primate studies, vaccine-induced T-cell responses have been correlated with reduced viral loads [4–7]. In humans, a recombinant adenovirus serotype 5 vector (Ad5) vaccine inducing significant cellular responses was shown to exert immune pressure on HIV-1 divergence in infected individuals [8,9]. Vaccineinduced cellular responses were of limited breadth and depth and this may explain why the vaccine was not effective in reducing viral loads for infected vaccine recipients [10]. Increased breadth and depth for T-cell responses may help prevent infection or may block escape pathways and lead to earlier control of viral replication or slower disease progression for vaccinated individuals who become infected. Mosaic antigen sequences encode composite full-length HIV-1 proteins that optimize coverage of potential T-cell epitopes [11]. Mosaic protein sequences are generated from a genetic algorithm in which natural sequences are repeatedly recombined in silico with the goal of computationally ‘evolving’ a protein sequence made up of the peptides most frequently represented in the database. Mosaic antigens may be generated based on a set of sequences from a single clade or from the entire M group sequence collection. The inclusion of multiple mosaic antigens into a polyvalent cocktail enables even greater coverage of T-cell epitopes and may potentially block viral escape pathways [12]. Consensus sequences are another strategy to improve T-cell response breadth. In this strategy, computational methods are used to generate a sequence representing “The first HIV vaccines containing mosaic antigen inserts will enter human testing later this year.”

Strategies to reverse melanoma-induced T-cell dysfunction

Patients with advanced melanoma can develop spontaneous cellular and humoral responses to tumor antigens. Understanding the failure of spontaneous or vaccine-induced tumor antigen-specific T-cell responses to promote the immunologic clearance of melanomas is critical. Multiple mechanisms of melanoma-induced immune escape, which are likely to cause the failure of the spontaneous or vaccine-induced immune responses to promote tumor regression in humans, have been elucidated. In addition, a number of negative factors in the tumor microenvironment dampen antitumor immune responses, including cytokines (like transforming growth factor-β or interleukin-10), suppressive cells (regulatory T cells and myelosuppressive dendritic cells), defective antigen presentation by tumor cells (human leukocyte antigen or T antigen expression loss, antigen processing machinery defects), amino acid catabolizing enzymes (indoleamine-2-3 dioxygenase, arginase), and immune inhibitory pathways (like cytotoxic T-lymphocyte antigen 4/cluster of differentiation 28, programmed death 1/programmed death 1 ligand 1). This information has been used to develop a number of therapies to specifically target these negative regulators of antimelanoma immune responses to enhance tumor antigen-specific immune responses and to increase the likelihood of clinical benefits in patients with advanced melanoma.

Abstract SY27-01: Synthetic vaccine for immunotherapy of high risk HPV infections.

Abstract Therapeutic vaccination of persistent virus infections and associated diseases including (pre-)cancer so far has largely evaded success, mainly due to the fact that insufficiently consistent and robust effector T cell responses were induced by the commonly used vaccine constructs and formulations such as recombinant viruses and bacteria, recombinant proteins, DNA constructs, Dendritic Cell (DC) vaccines and exact HLA class I binding peptides (short peptides). Problems have been severe antigenic competition from vector sequences by recombinant viruses and bacteria, insufficiently powerful T cell generation by DNA constructs, insufficient homing to lymph nodes of injected DC and antigen presentation of short peptides by non-professional antigen presenting cells in vivo, causing tolerance instead of immunity. Much more robust and consistent T cell responses can be obtained by vaccination with long (28-35 amino acid long) synthetic peptides. Such immunogens are more efficiently processed and presented than intact proteins by DC and only DC can efficiently perform this task. Moreover, only concentrated antigen of choice is offered and antigenic competition therefore plays no role. Phase I/II studies with an HPV16 SLP® vaccine, consisting of 13 long peptides covering the HPV16 E6 and E7 antigens, in patients with advanced HPV16-positive cervical cancer, revealed that this vaccine was safe and highly immunogenic. We then tested the clinical efficacy of this HPV16 SLP® vaccine in HPV16-induced high grade vulvar intraepithelial neoplasia (VIN3), a premalignant epithelial disorder, spontaneous regression of which occurs in less than 2% of patients and in which recurrence after standard treatment is high. In this phase 2 trial, 20 women with VIN3 were vaccinated three times sc in the limbs with a mix of the HPV16 E6 and E7 synthetic long peptides formulated in Montanide ISA-51. The endpoints were objective clinical responses, defined as reduction of at least 50% in lesion size (partial response) or complete regressions, and HPV16-specific T-cell responses. The vaccine was safe. At 3 months after the last vaccination, an objective response was observed in 12/20 (60%). Five patients showed a complete and durable regression of the lesions. The strength of the vaccine-induced HPV16-specific T-cell response was significantly higher in the group of patients with a complete regression of their lesions compared to non-responders. Patients with large lesions were less likely to experience a complete clinical response than patients with small lesions and we ascribe this to a larger proportion of vaccine induced HPV-specific regulatory cells in the patients with large lesions. In a preclinical mouse model we have shown marked synergism in eradication of established HPV16 E6/E7+ tumors between platinum-based chemotherapy and HPV16 SLP vaccination, associated with a decrease in myeloid cells in the blood and in the tumor. In a pilot clinical study, end stage cervical cancer patients, treated with carbotaxol, showed no T cell immunodeficiency and showed robust T cell effector responses to a single dose of HPV16 SLP® vaccine. These findings set the stage for a randomized phase II study of chemo-immunotherapy in this category of patients, in which chemotherapy alone will be compared with chemo-immunotherapy. In conclusion, treatment with the HPV16 SLP vaccine is effective in patients with established VIN disease. The SLP platform lends itself for development of therapeutic vaccines against many other chronic infections and non-viral cancers. In patients with cancer, it is attractive to combine this type of vaccination with chemotherapy and with immunomodulatory drugs such as type I interferon and checkpoint-control blocking monoclonal antibodies. Citation Format: Cornelis J. M. Melief. Synthetic vaccine for immunotherapy of high risk HPV infections. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr SY27-01. doi:10.1158/1538-7445.AM2013-SY27-01

Abstract SY27-03: Biomarker-guided development of novel multi-peptide cancer vaccines - from discovery to phase lll trials.

Abstract SY27-03: Biomarker-guided development of novel multi-peptide cancer vaccines - from discovery to phase lll trials.

HPV16 synthetic long peptide (HPV16-SLP) vaccination therapy of patients with advanced or recurrent HPV16-induced gynecological carcinoma, a phase II trial

BackgroundHuman papilloma virus type 16 (HPV16)-induced gynecological cancers, in particular cervical cancers, are found in many women worldwide. The HPV16 encoded oncoproteins E6 and E7 are tumor-specific targets for the adaptive immune system permitting the development of an HPV16-synthetic long peptide (SLP) vaccine with an excellent treatment profile in animal models. Here, we determined the toxicity, safety, immunogenicity and efficacy of the HPV16 SLP vaccine in patients with advanced or recurrent HPV16-induced gynecological carcinoma.MethodsPatients with HPV16-positive advanced or recurrent gynecological carcinoma (n = 20) were subcutaneously vaccinated with an HPV16-SLP vaccine consisting of a mix of 13 HPV16 E6 and HPV16 E7 overlapping long peptides in Montanide ISA-51 adjuvant. The primary endpoints were safety, toxicity and tumor regression as determined by RECIST. In addition, the vaccine-induced T-cell response was assessed by proliferation and associated cytokine production as well as IFNγ-ELISPOT.ResultsNo systemic toxicity beyond CTCAE grade II was observed. In a few patients transient flu-like symptoms were observed. In 9 out of 16 tested patients vaccine-induced HPV16-specific proliferative responses were detected which were associated with the production of IFNγ, TNFα, IL-5 and/or IL-10. ELISPOT analysis revealed a vaccine-induced immune response in 11 of the 13 tested patients. The capacity to respond to the vaccine was positively correlated to the patient’s immune status as reflected by their response to common recall antigens at the start of the trial. Median survival was 12.6 ± 9.1 months. No regression of tumors was observed among the 12 evaluable patients. Nineteen patients died of progressive disease.ConclusionsThe HPV16-SLP vaccine was well tolerated and induced a broad IFNγ-associated T-cell response in patients with advanced or recurrent HPV16-induced gynecological carcinoma but neither induced tumor regression nor prevented progressive disease. We, therefore, plan to use this vaccine in combination with chemotherapy and immunomodulation.

The candidate tuberculosis vaccine Mtb72F/AS02 in PPD positive adults: A randomized controlled phase I/II study

Prevention of tuberculosis (TB) through vaccination would substantially reduce the global TB burden. Mtb72F/AS02 is a candidate TB vaccine shown to be immunogenic and well tolerated in PPD-negative adults. We evaluated the safety and immunogenicity of Mtb72F/AS02 in Mycobacterium-primed adults (BCG-vaccinated, or infected adults who had received post-exposure chemoprophylaxis or treatment for pulmonary TB disease). In this observer-blind controlled trial, 20 BCG-vaccinated adults and 18 adults previously infected with Mycobacterium tuberculosis (Mtb), were randomized 3:1 to receive three doses of Mtb72F/AS02 or AS02 at one-month intervals, and followed for 6 months post third vaccination. Mtb72F/AS02 was well tolerated in BCG-vaccinated adults, and tended to be more reactogenic in Mtb-infected adults. Adverse events were mainly self-limiting, resolving without sequelae. No serious adverse events were reported. The adverse events in Mtb72F/AS02 vaccinees were not clearly associated with vaccine-induced responses (as assessed by proinflammatory cytokines, total IgE and C-reactive protein levels). No Th2 T-cell responses, or vaccine-induced T-cell responses to Mtb antigens (CFP-10/PPD/ESAT-6) were detected by ICS. In both cohorts, Mtb72F/AS02 induced persistent polyfunctional Mtb72F-specific CD4(+) T-cell responses and anti-Mtb72F humoral responses. IFN-γ was detectable in serum one day post each vaccination. Further evaluation of the candidate vaccine, Mtb72F/AS02, is warranted. ClinicalTrials.gov identifier: NCT00146744.

Antibodies with High Avidity to the gp120 Envelope Protein in Protection from Simian Immunodeficiency Virus SIV mac251 Acquisition in an Immunization Regimen That Mimics the RV-144 Thai Trial

The recombinant canarypox vector, ALVAC-HIV, together with human immunodeficiency virus (HIV) gp120 envelope glycoprotein, has protected 31.2% of Thai individuals from HIV acquisition in the RV144 HIV vaccine trial. This outcome was unexpected, given the limited ability of the vaccine components to induce CD8(+) T-cell responses or broadly neutralizing antibodies. We vaccinated macaques with an immunization regimen intended to mimic the RV144 trial and exposed them intrarectally to a dose of the simian immunodeficiency virus SIV(mac251) that transmits few virus variants, similar to HIV transmission to humans. Vaccination induced anti-envelope antibodies in all vaccinees and CD4(+) and CD8(+) T-cell responses. Three of the 11 macaques vaccinated with ALVAC-SIV/gp120 were protected from SIV(mac251) acquisition, but the result was not significant. The remaining vaccinees were infected and progressed to disease. The magnitudes of vaccine-induced SIV(mac251)-specific T-cell responses and binding antibodies were not significantly different between protected and infected animals. However, sera from protected animals had higher avidity antibodies to gp120, recognized the variable envelope regions V1/V2, and reduced SIV(mac251) infectivity in cells that express high levels of α(4)β(7) integrins, suggesting a functional role of antibodies to V2. The current results emphasize the utility of determining the titer of repeated mucosal challenge in the preclinical evaluation of HIV vaccines.

Breadth or conservation score (CS): which is more important for HIV-1 T cell based vaccine immunogen design?

Background One of the greatest challenges to develop an efficacious HIV vaccine is the enormous diversity of HIV-1. To tackle this problem, T cells based vaccine approaches have come up with two main camps: the mosaic immunogen camp: increasing the breadth of vaccine-induced responses, and the conserved immunogen camp: targeting vaccineinduced T-cell responses only to highly conserved viral regions. While both approaches are theoretically sound, there is no current data suggesting that either approach will be successful in inducing T cells with superior antiviral efficacy. Here we analyzed T cell responses elicited during early HIV-1 infection, to address the question whether CS of targeted epitopes and breadth of T cell responses play an important role in viral control. Methods Using IFN-g ELISpot, we comprehensively mapped T cell epitope specificities recognized by 24 ART-naive individuals during early infection. We identified CS of targeted epitopes, where the CS is defined as the proportion of random HIV-1 group M amino acid sequences in the LANL database that include the epitope. We used a prediction model to impute the viral load (VL) set-point using the first available VL as a predictor for subjects lacking VL set-point. We further evaluated the association between the CS of the targeted epitopes and breadth of T cell responses to the individuals’ VL set-point.

MRKAd5 HIV-1 Gag/Pol/Nef Vaccine-Induced T-Cell Responses Inadequately Predict Distance of Breakthrough HIV-1 Sequences to the Vaccine or Viral Load

BackgroundThe sieve analysis for the Step trial found evidence that breakthrough HIV-1 sequences for MRKAd5/HIV-1 Gag/Pol/Nef vaccine recipients were more divergent from the vaccine insert than placebo sequences in regions with predicted epitopes. We linked the viral sequence data with immune response and acute viral load data to explore mechanisms for and consequences of the observed sieve effect.MethodsNinety-one male participants (37 placebo and 54 vaccine recipients) were included; viral sequences were obtained at the time of HIV-1 diagnosis. T-cell responses were measured 4 weeks post-second vaccination and at the first or second week post-diagnosis. Acute viral load was obtained at RNA-positive and antibody-negative visits.FindingsVaccine recipients had a greater magnitude of post-infection CD8+ T cell response than placebo recipients (median 1.68% vs 1.18%; p = 0·04) and greater breadth of post-infection response (median 4.5 vs 2; p = 0·06). Viral sequences for vaccine recipients were marginally more divergent from the insert than placebo sequences in regions of Nef targeted by pre-infection immune responses (p = 0·04; Pol p = 0·13; Gag p = 0·89). Magnitude and breadth of pre-infection responses did not correlate with distance of the viral sequence to the insert (p>0·50). Acute log viral load trended lower in vaccine versus placebo recipients (estimated mean 4·7 vs 5·1) but the difference was not significant (p = 0·27). Neither was acute viral load associated with distance of the viral sequence to the insert (p>0·30).InterpretationDespite evidence of anamnestic responses, the sieve effect was not well explained by available measures of T-cell immunogenicity. Sequence divergence from the vaccine was not significantly associated with acute viral load. While point estimates suggested weak vaccine suppression of viral load, the result was not significant and more viral load data would be needed to detect suppression.

Low-dose cyclophosphamide administered as daily or single dose enhances the antitumor effects of a therapeutic HPV vaccine

Although therapeutic HPV vaccines are able to elicit systemic HPV-specific immunity, clinical responses have not always correlated with levels of vaccine-induced CD8(+) T cells in human clinical trials. This observed discrepancy may be attributable to an immunosuppressive tumor microenvironment in which the CD8(+) T cells are recruited. Regulatory T cells (Tregs) are cells that can dampen cytotoxic CD8(+) T-cell function. Cyclophosphamide (CTX) is a systemic chemotherapeutic agent, which can eradicate immune cells, including inhibitory Tregs. The optimal dose and schedule of CTX administration in combination with immunotherapy to eliminate the Treg population without adversely affecting vaccine-induced T-cell responses is unknown. Therefore, we investigated various dosing and administration schedules of CTX in combination with a therapeutic HPV vaccine in a preclinical tumor model. HPV tumor-bearing mice received either a single preconditioning dose or a daily dose of CTX in combination with the pNGVL4a-CRT/E7(detox) DNA vaccine. Both single and daily dosing of CTX in combination with vaccine had a synergistic antitumor effect as compared to monotherapy alone. The potent antitumor responses were attributed to the reduction in Treg frequency and increased infiltration of HPV16 E7-specific CD8(+) T cells, which led to higher ratios of CD8(+)/Treg and CD8(+)/CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs). There was an observed trend toward decreased vaccine-induced CD8(+) T-cell frequency with daily dosing of CTX. We recommend a single, preconditioning dose of CTX prior to vaccination due to its efficacy, ease of administration, and reduced cumulative adverse effect on vaccine-induced T cells.

Pediatric influenza vaccination: understanding the T-cell response

Influenza A virus-specific T cells are highly cross-reactive and contribute to heterosubtypic immunity, which may afford protection against novel pandemic strains of influenza virus. However, the magnitude and nature of virus-specific T-cell responses induced by natural infections and/or vaccination in young children is poorly understood. Host factors, such as the development of the immune system during childhood and environmental factors such as exposure rates to influenza viruses and interference by vaccination contribute to shaping the magnitude and specificity of the T-cell response. Here, the authors review several of these factors, including the differences between T-cell responses of young children and adults, the age-dependent frequency of virus-specific T cells and the impact of annual childhood influenza vaccination. In addition, the authors summarize all currently available studies in which influenza vaccine-induced T-cell responses were evaluated. The authors discuss these findings in the light of developing vaccines and vaccination strategies aiming at the induction of protective immunity to seasonal and pandemic influenza viruses of antigenically distinct subtypes.

Optimization and qualification of a multiplex bead array to assess cytokine and chemokine production by vaccine-specific cells

The magnitude and functional phenotype (e.g. proliferation, immune stimulation) of vaccine-induced T-cell responses are likely to be critical in defining responses that can control pathogenic challenge. Current multi-parameter flow cytometric techniques may not be sufficient to measure all of these different functions, since characterizing T-cell responses by flow cytometry is presently limited to concurrent measurement of at most 10 cytokines/chemokines. Here, we describe extensive studies conducted using standardized GCLP procedures to optimize and qualitatively/quantitatively qualify a multiplex bead array (MBA) performed on supernatant collected from stimulated peripheral blood mononuclear cells (PBMC) to assess 12 cytokines and chemokines of interest. Our optimized MBA shows good precision (intra-assay, inter-day, inter-technician; coefficients of variation <30%) and linearity for most of the analytes studied. We also developed positivity criteria that allow us to define a response as positive or negative with a high degree of confidence. In conclusion, we provide a detailed description of the qualification of an MBA, which permits quantitative and qualitative evaluation of vaccine-induced immunogenicity and analysis of immune correlates of protection. This assay provides an excellent complement to the existing repertoire of assays for assessing immunogenicity in HIV vaccine clinical trials.

Association of idiotype vaccine-induced T-cell response with improved survival and time-to-next treatment (TTNT) in untreated mantle cell lymphoma (MCL).

2528 Background: Murine models show Id-vaccines induce antitumor responses, possibly through Th1/Tc1 cytokines. We report an 11-year follow-up of Id-vaccine following DA-EPOCH-Rituximab in 26 untreated MCL patients. Methods: DA-EPOCH-R was administered q3 weeks × 6, followed 12 weeks later by 5 cycles of Id-vaccine. Id protein was made by hybridoma technology, conjugated to keyhole limpet hemocyanin (KLH) and administered with GM-CSF. Pre- and post-vaccine immune responses (IR) were tested in parallel: anti-Id and anti-KLH humoral responses (ELISA); anti-KLH cellular responses (intracellular cytokine assay); and anti-tumor cellular responses (cytokine induction, IFNγ ELISPOT). Results: Characteristics: median age 57 (r 22-73), blastoid variant 15%, and MIPI (low-65%; intermediate-16%; high-19%). With 122 mo median follow-up (r 111-132), the median PFS is 24 mo and OS is 104 mo. MIPI was associated with OS (p=0.0002); median OS: low (not reached), intermediate (84 mo) and high (44 mo). We found no association between OS and anti-KLH IR, anti-Id humoral response, IFNγ ELISPOT, or antitumor TNFα or IFNγ responses. Normalized antitumor T-cell GM-CSF response (median &lt;4.3 vs. &gt;4.3) was associated with OS of 79 mo vs. not reached, respectively (p=0.015 (unadj.) and p=0.045 (adj.)). MIPI (p=0.02) and GM-CSF (p=0.057) were independently associated with OS. TTNT (based on disease activity), correlated with antitumor GM-CSF response (p=0.018) but not MIPI and was independent of MIPI (GM-CSF; p=0.041). Correlation of pre-and post-treatment GM-CSF production suggested a priming effect. Tumor proliferation by GEP did not correlate with OS (n=14). Conclusions: Antitumor GM-CSF response was significantly associated with OS and TTNT, suggesting antitumor cellular immune response significantly delayed tumor growth. Antitumor GM-CSF response may serve as a surrogate biomarker for vaccine efficacy. Our results are consistent with recent data that T-cell GM-CSF production is required for breaking tolerance against self-antigens. Id vaccines may prolong survival of MCL following rituximab-based chemotherapy and should be further evaluated.