Antigen Gp100 Research Articles

Intra-patient escalation dosing strategy with IMCgp100 results in mitigation of T-cell based toxicity and preliminary efficacy in advanced uveal melanoma.

9531 Background: IMCgp100 is a bispecific biologic capable of redirecting T cells against the melanocyte-associated antigen gp100. In the first-in-human (FIH) clinical trial, preliminary efficacy of IMCgp100 in advanced uveal melanoma (UM) was observed; however, cases of severe T cell-mediated toxicities with the first 2 doses limited dosing to 50 mcg QW. This phase 1 study was designed to implement intra-patient escalation to mitigate toxicity and maximize exposure of IMCgp100. Methods: Using a 3+3 design, HLA-A2+ pts with metastatic UM were treated with low weekly (QW) dosing of IMCgp100 iv at Cycle 1, Day 1 (C1D1) (20 mcg) and C1D8 (30 mcg), followed by the escalated cohort dose administered at C1D15 and beyond. Results: Nineteen metastatic UM pts with a median of 3 prior lines of therapy (range 0 - 8) were treated across 4 target dose cohorts (60, 70, 80, and 75 mcg). Fifteen of 19 pts remain on treatment at the data cutoff (25Nov16). Enrollment completed 15Sep16. DLT was observed in 1 of 6 pts in the 70-mcg cohort (LFT elevation), and 2 of 4 pts treated at 80 mcg QW (LFT and bilirubin elevation). The 80 mcg dose level was not tolerated and a 75 mcg cohort was enrolled. Six pts were treated at 75 mcg without DLT; this dose was identified as the MTD and RP2D. All 3 DLT resolved without corticosteroids and all pts resumed IMCgp100. Frequent related AE included pruritus (84%), pyrexia (84%), fatigue (74%), hypotension (74%) and peripheral edema (63%). Gr 3/4 drug-related AE include AST increased (15%), erythema (15%) and hypotension (15%). Preliminary efficacy data (RECIST v1.1) from 17 evaluable pts (2 pts had insufficient follow-up) showed no objective responses; 12 pts had a BOR of SD (63%) including 4 pts (24%) with a ≥10% reduction in target lesions. With median follow-up of 1.8 mo, the disease control rate (16 wks) was 32%. Conclusions: The intra-patient escalation regimen of IMCgp100 results in a 50% increase in dose above the FIH Phase 1, acceptable safety profile, and preliminary efficacy in UM pts. Considering the dismal prognosis of metastatic UM, the PFS observed in this study is encouraging. A Phase 2 expansion cohort and separate pivotal trial of IMCgp100 in advanced UM are ongoing. Clinical trial information: NCT02570308.

Expressing anti-HIV VRC01 antibody using the murine IgG1 secretion signal in Pichia pastoris

The use of the recombinant expression platform Pichia pastoris to produce pharmaceutically important proteins has been investigated over the past 30 years. Compared to mammalian cultures, expression in P. pastoris is cheaper and faster, potentially leading to decreased costs and process development times. Product yields depend on a number of factors including the secretion signal chosen for expression, which can influence the host cell response to recombinant protein production. VRC01, a broadly neutralising anti-HIV antibody, was expressed in P. pastoris, using the methanol inducible AOX1 promoter for both the heavy and light chains. Titre reached up to 3.05 μg mL−1 in small scale expression. VRC01 was expressed using both the α-mating factor signal peptide from Saccharomyces cerevisiae and the murine IgG1 signal peptide. Surprisingly, using the murine IgG1 signal peptide resulted in higher yield of antibody capable of binding gp140 antigen. Furthermore, we evaluated levels of secretory stress compared to the untransformed wild-type strain and show a reduced level of secretory stress in the murine IgG1 signal peptide strains versus those containing the α-MF signal peptide. As bottlenecks in the secretory pathway are often the limiting factor in protein secretion, reduced levels of secretory stress and the higher yield of functional antibody suggest the murine IgG1 signal peptide may lead to better protein folding and secretion. This work indicates the possibilities for utilising the murine IgG1 signal peptide for a range of antibodies, resulting in high yields and reduced cellular stress.

Paracoccidioidomycosis infection in domestic and wild mammals by Paracoccidioides lutzii

Paracoccidioidomycosis (PCM) is a systemic mycosis that occurs in several Latin American countries, especially in Brazil. It is caused by the thermo-dimorphic fungus Paracoccidioides spp. Serological studies to detect animal infection represent an excellent strategy for data on the agent's ecology. Although the state of Rio Grande do Sul (RS) is an endemic area for PCM in humans, there is scarce information available on the ecology of the agent in the region. This study aimed to investigate the infection by Paracoccidioides lutzii in animals living in RS, Brazil. A total of 85 wild mammals, 200 horses and 196 domestic dogs, previously tested for infection by P.brasiliensis, were included in this study. Serum samples from the animals were tested by ELISA to detect anti- P.lutzii antibodies. From the 481 animals tested, 105 (21.8%) were seropositive for IgG anti-P.lutzii. Of these, 54 were also positive for P.brasiliensis. A total of 11 horses (10.5%), 30 dogs (28.8%) and 10 wild mammals (9.5%) were positive only for P.lutzii (n=51). The detection of anti-P.lutzii antibodies in animals of RS suggests that the fungus can be found in southern Brazil, despite being described mainly in the midwest and southeast of the country.

Subtractive SELEX using agar beads for screening DNA aptamers with specific affinity to HIV gp41 antigen

To obtain DNA aptamers with a highly specific affinity to HIV gp41 antigen using SELEX screening for detection of HIV. The specific DNA aptamers of HIV gp41 antigen were screened from the double-stranded DNA derived from the single-stranded DNA (ssDNA) library with agarose beads as the supportive medium and HIV gp41 antigen as the target molecule using SELEX technique and real-time quantitative PCR. The secondary ssDNA library obtained after 6 rounds of screening was amplified by PCR to obtain dsDNA. The dsDNA was linked with pMDTM 18-T vector, cloned and sequenced to obtain 4 aptamers of HIV gp41 antigen. The affinities of the 4 aptamers (Kd) all reached the nanomolar level. Among the 4 aptamers, the No.15 aptamer showed the strongest affinity. Specificity analysis of the aptamers revealed that all these 4 aptamers had specific affinity to HIV gp41 antigen with no affinity to other non-specific proteins. We successfully obtained DNA aptamers with highly specific affinity to the HIV gp41 antigen from random single-stranded oligonucleotide library, and the obtained aptamers have the ability to antagonize HIV gp41 antigen.

Lipid Nanoparticle Assisted mRNA Delivery for Potent Cancer Immunotherapy.

The induction of a strong cytotoxic T cell response is an important prerequisite for successful immunotherapy against many viral diseases and tumors. Nucleotide vaccines, including mRNA vaccines with their intracellular antigen synthesis, have been shown to be potent activators of a cytotoxic immune response. The intracellular delivery of mRNA vaccines to the cytosol of antigen presenting immune cells is still not sufficiently well understood. Here, we report on the development of a lipid nanoparticle formulation for the delivery of mRNA vaccines to induce a cytotoxic CD 8 T cell response. We show transfection of dendritic cells, macrophages, and neutrophils. The efficacy of the vaccine was tested in an aggressive B16F10 melanoma model. We found a strong CD 8 T cell activation after a single immunization. Treatment of B16F10 melanoma tumors with lipid nanoparticles containing mRNA coding for the tumor-associated antigens gp100 and TRP2 resulted in tumor shrinkage and extended the overall survival of the treated mice. The immune response can be further increased by the incorporation of the adjuvant LPS. In conclusion, the lipid nanoparticle formulation presented here is a promising vector for mRNA vaccine delivery, one that is capable of inducing a strong cytotoxic T cell response. Further optimization, including the incorporation of different adjuvants, will likely enhance the potency of the vaccine.

Fusion of the dendritic cell-targeting chemokine MIP3α to melanoma antigen Gp100 in a therapeutic DNA vaccine significantly enhances immunogenicity and survival in a mouse melanoma model

BackgroundAlthough therapeutic cancer vaccines have been mostly disappointing in the clinic, the advent of novel immunotherapies and the future promise of neoantigen-based therapies have created the need for new vaccine...

Structure of an N276-Dependent HIV-1 Neutralizing Antibody Targeting a Rare V5 Glycan Hole Adjacent to the CD4 Binding Site.

ABSTRACTAll HIV-1-infected individuals develop strain-specific neutralizing antibodies to their infecting virus, which in some cases mature into broadly neutralizing antibodies. Defining the epitopes of strain-specific antibodies that overlap conserved sites of vulnerability might provide mechanistic insights into how broadly neutralizing antibodies arise. We previously described an HIV-1 clade C-infected donor, CAP257, who developed broadly neutralizing plasma antibodies targeting an N276 glycan-dependent epitope in the CD4 binding site. The initial CD4 binding site response potently neutralized the heterologous tier 2 clade B viral strain RHPA, which was used to design resurfaced gp120 antigens for single-B-cell sorting. Here we report the isolation and structural characterization of CAP257-RH1, an N276 glycan-dependent CD4 binding site antibody representative of the early CD4 binding site plasma response in donor CAP257. The cocrystal structure of CAP257-RH1 bound to RHPA gp120 revealed critical interactions with the N276 glycan, loop D, and V5, but not with aspartic acid 368, similarly to HJ16 and 179NC75. The CAP257-RH1 monoclonal antibody was derived from the immunoglobulin-variable IGHV3-33 and IGLV3-10 genes and neutralized RHPA but not the transmitted/founder virus from donor CAP257. Its narrow neutralization breadth was attributed to a binding angle that was incompatible with glycosylated V5 loops present in almost all HIV-1 strains, including the CAP257 transmitted/founder virus. Deep sequencing of autologous CAP257 viruses, however, revealed minority variants early in infection that lacked V5 glycans. These glycan-free V5 loops are unusual holes in the glycan shield that may have been necessary for initiating this N276 glycan-dependent CD4 binding site B-cell lineage.IMPORTANCE The conserved CD4 binding site on gp120 is a major target for HIV-1 vaccine design, but key events in the elicitation and maturation of different antibody lineages to this site remain elusive. Studies have shown that strain-specific antibodies can evolve into broadly neutralizing antibodies or in some cases act as helper lineages. Therefore, characterizing the epitopes of strain-specific antibodies may help to inform the design of HIV-1 immunogens to elicit broadly neutralizing antibodies. In this study, we isolate a narrowly neutralizing N276 glycan-dependent antibody and use X-ray crystallography and viral deep sequencing to describe how gp120 lacking glycans in V5 might have elicited these early glycan-dependent CD4 binding site antibodies. These data highlight how glycan holes can play a role in the elicitation of B-cell lineages targeting the CD4 binding site.

Combination of Antiretroviral Drugs and Radioimmunotherapy Specifically Kills Infected Cells from HIV-Infected Individuals

Eliminating virally infected cells is an essential component of any HIV eradication strategy. Radioimmunotherapy (RIT), a clinically established method for killing cells using radiolabeled antibodies, was recently applied to target HIV-1 gp41 antigen expressed on the surface of infected cells. Since gp41 expression by infected cells is likely downregulated in patients on antiretroviral therapy (ART), we evaluated the ability of RIT to kill ART-treated infected cells using both in vitro models and lymphocytes isolated from HIV-infected subjects. Human peripheral blood mononuclear cells (PBMCs) were infected with HIV and cultured in the presence of two clinically relevant ART combinations. Scatchard analysis of the 2556 human monoclonal antibody to HIV gp41 binding to the infected and ART-treated cells demonstrated sufficient residual expression of gp41 on the cell surface to warrant subsequent RIT. This is the first time the quantification of gp41 post-ART is being reported. Cells were then treated with Bismuth-213-labeled 2556 antibody. Cell survival was quantified by Trypan blue and residual viremia by p24 ELISA. Cell surface gp41 expression was assessed by Scatchard analysis. The experiments were repeated using PBMCs isolated from blood specimens obtained from 15 HIV-infected individuals: 10 on ART and 5 ART-naïve. We found that 213Bi-2556 killed ART-treated infected PBMCs and reduced viral production to undetectable levels. ART and RIT co-treatment was more effective at reducing viral load in vitro than either therapy alone, indicating that gp41 expression under ART was sufficient to allow 213Bi-2556 to deliver cytocidal doses of radiation to infected cells. This study provides proof of concept that 213Bi-2556 may represent an innovative and effective targeting method for killing HIV-infected cells treated with ART and supports continued development of 213Bi-2556 for co-administration with ART toward an HIV eradication strategy.

Melanoma antigens are biomarkers for ipilimumab response.

Novel immunotherapy modalities significantly improve survival of patients with metastatic melanoma. However, CTLA-4-blocking monoclonal antibody ipilimumab is effective only in a small proportion of patients. Biomarkers for prediction of treatment response are indispensably needed. To determine the utility of multimarker detection of circulating melanoma cells as prognostic and pharmacodynamic biomarker in patients with metastatic melanoma treated with ipilimumab. Patients (n = 62) with metastatic melanoma in unresectable stage III or metastatic stage IV treated with ipilimumab were recruited prospectively. The values of four melanoma markers on circulating cells Melan-A, gp100, MAGE-3 and melanoma inhibitory antigen prior to the treatment and within the therapy were compared to the data collected at baseline - after the melanoma surgery. The immunotherapy pretreatment marker level was found to be prognostic of overall survival; lower levels were linked to longer survival time. Moreover, longitudinal follow-up of melanoma markers in patients treated with ipilimumab correlates with therapy response. A decline of marker levels by >30% at week 6 (in 83% of the responding subjects) to week 9 (in all responders) of ipilimumab administration was associated with response to therapy. Elevation of the tumour markers during the treatment precedes clinical progression and gives an early warning of treatment failure. Melanoma circulating cells hold potential as predictive and pharmacodynamic biomarker of immunotherapy.

Generation and Characterization of a Bivalent HIV-1 Subtype C gp120 Protein Boost for Proof-of-Concept HIV Vaccine Efficacy Trials in Southern Africa.

The viral envelope glycoprotein (Env) is the major target for antibody (Ab)-mediated vaccine development against the Human Immunodeficiency Virus type 1 (HIV-1). Although several recombinant Env antigens have been evaluated in clinical trials, only the surface glycoprotein, gp120, (from HIV-1 subtype B, MN, and subtype CRF_01AE, A244) used in the ALVAC prime-AIDSVAX gp120 boost RV144 Phase III HIV vaccine trial was shown to contribute to protective efficacy, although modest and short-lived. Hence, for clinical trials in southern Africa, a bivalent protein boost of HIV-1 subtype C gp120 antigens composed of two complementary gp120s, from the TV1.C (chronic) and 1086.C (transmitted founder) HIV-1 strains, was selected. Stable Chinese Hamster Cell (CHO) cell lines expressing these gp120s were generated, scalable purification methods were developed, and a detailed analytical analysis of the purified proteins was conducted that showed differences and complementarity in the antigenicity, glycan occupancy, and glycan content of the two gp120 molecules. Moreover, mass spectrometry revealed some disulfide heterogeneity in the expressed proteins, particularly in V1V2-C1 region and most prominently in the TV1 gp120 dimers. These dimers not only lacked binding to certain key CD4 binding site (CD4bs) and V1V2 epitope-directed ligands but also elicited reduced Ab responses directed to those epitopes, in contrast to monomeric gp120, following immunization of rabbits. Both monomeric and dimeric gp120s elicited similarly high titer Tier 1 neutralizing Abs as measured in standard virus neutralization assays. These results provide support for clinical evaluations of bivalent preparations of purified monomeric TV1.C and 1086.C gp120 proteins.

Immune-related Adverse Events of Dendritic Cell Vaccination Correlate With Immunologic and Clinical Outcome in Stage III and IV Melanoma Patients.

The purpose of this study was to determine the toxicity profile of dendritic cell (DC) vaccination in stage III and IV melanoma patients, and to evaluate whether there is a correlation between side effects and immunologic and clinical outcome. This is a retrospective analysis of 82 stage III and 137 stage IV melanoma patients, vaccinated with monocyte-derived or naturally circulating autologous DCs loaded with tumor-associated antigens gp100 and tyrosinase. Median follow-up time was 54.3 months in stage III patients and 12.9 months in stage IV patients. Treatment-related adverse events occurred in 84% of patients; grade 3 toxicity was present in 3% of patients. Most common adverse events were flu-like symptoms (67%) and injection site reactions (50%), and both correlated with the presence of tetramer-positive CD8+ T cells (both P<0.001). In stage III melanoma patients experiencing flu-like symptoms, median overall survival (OS) was not reached versus 32.3 months in patients without flu-like symptoms (P=0.009); median OS in patients with an injection site reaction was not reached versus 53.7 months in patients without an injection site reaction (P<0.05). In stage IV melanoma patients (primary uveal and mucosal melanomas excluded), median OS in patients with or without flu-like symptoms was 13.1 versus 8.9 months, respectively (P=0.03); median OS in patients with an injection site reaction was 15.7 months versus 9.8 months in patients without an injection site reaction (P=0.003). In conclusion, DC vaccination is safe and tolerable and the occurrence of the immune-related side effects, such as flu-like symptoms and injection site reactions, correlates with immunologic and clinical outcome.

Coadministration of a Plasmid Encoding HIV-1 Gag Enhances the Efficacy of Cancer DNA Vaccines.

DNA vaccination holds great promise for the prevention and treatment of cancer and infectious diseases. However, the clinical ability of DNA vaccines is still controversial due to the limited immune response initially observed in humans. We hypothesized that electroporation of a plasmid encoding the HIV-1 Gag viral capsid protein would enhance cancer DNA vaccine potency. DNA electroporation used to deliver plasmids in vivo, induced type I interferons, thereby supporting the activation of innate immunity. The coadministration of ovalbumin (OVA) and HIV-1 Gag encoding plasmids modulated the adaptive immune response. This strategy favored antigen-specific Th1 immunity, delayed B16F10-OVA tumor growth and improved mouse survival in both prophylactic and therapeutic vaccination approaches. Similarly, a prophylactic DNA immunization against the melanoma-associated antigen gp100 was enhanced by the codelivery of the HIV-1 Gag plasmid. The adjuvant effect was not driven by the formation of HIV-1 Gag virus-like particles. This work highlights the ability of both electroporation and the HIV-1 Gag plasmid to stimulate innate immunity for enhancing cancer DNA vaccine immunogenicity and demonstrates interesting tracks for the design of new translational genetic adjuvants to overcome the current limitations of DNA vaccines in humans.

Adjuvant dendritic cell vaccination induces tumor-specific immune responses in the majority of stage III melanoma patients

ABSTRACTPurpose: To determine the effectiveness of adjuvant dendritic cell (DC) vaccination to induce tumor-specific immunological responses in stage III melanoma patients.Experimental design: Retrospective analysis of stage III melanoma patients, vaccinated with autologous monocyte-derived DC loaded with tumor-associated antigens (TAA) gp100 and tyrosinase after radical lymph node dissection. Skin-test infiltrating lymphocytes (SKILs) obtained from delayed-type hypersensitivity skin-test biopsies were analyzed for the presence of TAA-specific CD8+ T cells by tetrameric MHC-peptide complexes and by functional TAA-specific T cell assays, defined by peptide-recognition (T2 cells) and/or tumor-recognition (BLM and/or MEL624) with specific production of Th1 cytokines and no Th2 cytokines.Results: Ninety-seven patients were analyzed: 21 with stage IIIA, 34 with stage IIIB, and 42 had stage IIIC disease. Tetramer-positive CD8+ T cells were present in 68 patients (70%), and 24 of them showed a response against all 3 epitopes tested (gp100:154–162, gp100:280–288, and tyrosinase:369–377) at any point during vaccinations. A functional T cell response was found in 62 patients (64%). Rates of peptide-recognition of gp100:154–162, gp100:280–288, and tyrosinase:369–377 were 40%, 29%, and 45%, respectively. Median recurrence-free survival and distant metastasis-free survival of the whole study population were 23.0 mo and 36.8 mo, respectively.Conclusions: DC vaccination induces a functional TAA-specific T cell response in the majority of stage III melanoma patients, indicating it is more effective in stage III than in stage IV melanoma patients. Furthermore, performing multiple cycles of vaccinations enhances the chance of a broader immune response.

Comprehensive Characterization of Reference Standard Lots of HIV-1 Subtype C Gp120 Proteins for Clinical Trials in Southern African Regions.

Two HIV-1 subtype C gp120 protein candidates were the selected antigens for several experimental vaccine regimens now under evaluation in HVTN 100 Phase I/II clinical trial aiming to support the start of the HVTN 702 Phase IIb/III trial in southern Africa, which is designed to confirm and extend the partial protection seen against HIV-1 infection in the RV144 Thai trial. Here, we report the comprehensive physicochemical characterization of the gp120 reference materials that are representative of the clinical trial materials. Gp120 proteins were stably expressed in Chinese Hamster Ovary (CHO) cells and subsequently purified and formulated. A panel of analytical techniques was used to characterize the physicochemical properties of the two protein molecules. When formulated in the AS01 Adjuvant System, the bivalent subtype C gp120 antigens elicited 1086.C- and TV1.C-specific binding antibody and CD4+ T cell responses in mice. All the characteristics were highly representative of the Clinical Trial Materials (CTM). Data from this report demonstrate the immunogenicity of the gp120 antigens, provide comprehensive characterization of the molecules, set the benchmark for assessment of current and future CTM lots, and lay the physicochemical groundwork for interpretation of future clinical trial data.

68. Immunovirotherapy: Enhancing Personalized T Cell Therapy with Oncolytic Measles Virus Vaccination

Oncolytic viruses directly reduce tumor burden by selective lytic replication in malignant cells, which designates these vectors as a potent platform for targeted cancer therapy. Lately the focus of oncolytic research has shifted towards the immunostimulatory potential of viral infection within the tumor microenvironment. Oncolytic viruses can be considered to act as an autologous tumor vaccine with the capacity to induce a tumor-specific T cell response. We hypothesize that oncolytic measles virus (MV) expressing a tumor-associated antigen (TAA) can specifically support T cell activation and persistence after adoptive transfer of TAA-specific T cells. We modified the Schwarz vaccine-derived measles virus to encode either OVA as a model antigen or one of the endogenous melanoma antigens trp-2 or gp100. TAA insertion did not impede viral replication and oncolysis compared to the parental virus. For in vivo studies, we have generated a new immunocompetent mouse model for MV oncolysis, B16-hCD46. Transduction of hCD46-positive B16 tumor cells with the novel viruses induces a strong virus-mediated expression of the tumor antigens, serving as a specific and lasting stimulus for adoptively transferred T cells. With the increasing availability of tumor sequencing data, this study has direct implications for future clinical trials of personalized immunovirotherapy.

Construction of a recombinant HIV-1 gp140 protein vaccine and evaluation of its immunogenicity

Objective To construct a recombinant HIV-1 gp140 protein vaccine and to evaluate its immunogenicity. Methods Four expression vectors containing different signal peptides including DRVI, IL-2, venom and chitinase were constructed for the expression of gp140 protein clones. Western blot assay was performed to evaluate the expression efficiency of the constructed expression vectors. The cleavage of signal peptides was analyzed by sequencing analysis. The gp140 protein clones with different lengths of C-terminus were constructed and then comparatively analyzed for the screening of optimized recombinant HIV-1 gp140 antigen. Guinea pigs were immunized with different strategies and the potency of vaccination was evaluated by detecting the binding antibodies and neutralizing antibodies after immunization. Results DRVI, the designed signal peptide, had the advantages in determining the efficiency of protein secretion and signal peptide cleavage. Compared with the co-immunization with DNA and recombinant Tiantan vaccinia (rTV) HIV vaccines, immunization of guinea pigs with the recombined gp140 protein vaccine alone could induce higher levels of binding antibodies and neutralizing antibodies. The gp140 protein with long C-terminus was slightly better than the one with short C-terminus in eliciting immune response, but no significant differences were found between them. Conclusion The optimized HIV-1 gp140 protein vaccine with appropriate protein signal peptide and C-terminus was successfully constructed and turned out to be effective in eliciting stronger immune response. Key words: HIV-1 gp140 protein; Antigen design; Immune evaluation

An optimized single chain TCR scaffold relying on the assembly with the native CD3-complex prevents residual mispairing with endogenous TCRs in human T-cells.

Immunotherapy of cancer envisions the adoptive transfer of T-cells genetically engineered with tumor-specific heterodimeric α/β T-cell receptors (TCRα/β). However, potential mispairing of introduced TCRα/β-chains with endogenous β/α-ones may evoke unpredictable autoimmune reactivities. A novel single chain (sc)TCR format relies on the fusion of the Vα-Linker-Vβ-fragment to the TCR Cβ-domain and coexpression of the TCR Cα-domain capable of recruiting the natural CD3-complex for full and hence, native T-cell signaling. Here, we tested whether such a gp100(280-288)- or p53(264-272) tumor antigen-specific scTCR is still prone to mispairing with TCRα. In a human Jurkat-76 T-cell line lacking endogenous TCRs, surface expression and function of a scTCR could be reconstituted by any cointroduced TCRα-chain indicating mispairing to take place on a molecular basis. In contrast, transduction into human TCRα/β-positive T-cells revealed that mispairing is largely reduced. Competition experiments in Jurkat-76 confirmed the preference of dcTCR to selfpair and to spare scTCR. This also allowed for the generation of dc/scTCR-modified cytomegalovirus/tumor antigen-bispecific T-cells to augment T-cell activation in CMV-infected tumor patients. Residual mispairing was prevented by strenghtening the Vα-Li-Vβ-fragment through the design of a novel disulfide bond between a Vα- and a linker-resident residue close to Vβ. Multimer-stainings, and cytotoxicity-, IFNγ-secretion-, and CFSE-proliferation-assays, the latter towards dendritic cells endogenously processing RNA-electroporated gp100 antigen proved the absence of hybrid scTCR/TCRα-formation without impairing avidity of scTCR/Cα in T-cells. Moreover, a fragile cytomegalovirus pp65(495-503)-specific scTCR modified this way acquired enhanced cytotoxicity. Thus, optimized scTCR/Cα inhibits residual TCR mispairing to accomplish safe adoptive immunotherapy for bulk endogenous TCRα/β-positive T-cells.

Immunological Characterization of Plant-Based HIV-1 Gag/Dgp41 Virus-Like Particles.

It is widely anticipated that a prophylactic vaccine may be needed to control the HIV/AIDS epidemic worldwide. Despite over two decades of research, a vaccine against HIV-1 remains elusive, although a recent clinical trial has shown promising results. Recent studies have focused on highly conserved domains within HIV-1 such as the membrane proximal external region (MPER) of the envelope glycoprotein, gp41. MPER has been shown to play critical roles in mucosal transmission of HIV-1, though this peptide is poorly immunogenic on its own. Here we provide evidence that plant-produced HIV-1 enveloped virus-like particles (VLPs) consisting of Gag and a deconstructed form of gp41 comprising the MPER, transmembrane, and cytoplasmic domains (Dgp41) provides an effective platform to display MPER for use as an HIV vaccine candidate. Prime-boost strategies combining systemic and mucosal priming with systemic boosting using two different vaccine candidates (VLPs and CTB-MPR—a fusion of MPER and the B-subunit of cholera toxin) were investigated in BALB/c mice. Serum antibody responses against both the Gag and gp41 antigens were elicited when systemically primed with VLPs. These responses could be recalled following systemic boosting with VLPs. In addition, mucosal priming with VLPs allowed for a boosting response against Gag and gp41 when boosted with either candidate. Importantly, the VLPs also induced Gag-specific CD4 and CD8 T-cell responses. This report on the immunogenicity of plant-based Gag/Dgp41 VLPs may represent an important milestone on the road towards a broadly efficacious and inexpensive subunit vaccine against HIV-1.

Prophylactic vaccines are potent activators of monocyte-derived dendritic cells and drive effective anti-tumor responses in melanoma patients at the cost of toxicity.

Dendritic cell (DC)-based immunotherapy is explored worldwide in cancer patients, predominantly with DC matured with pro-inflammatory cytokines and prostaglandin E2. We studied the safety and efficacy of vaccination with monocyte-derived DC matured with a cocktail of prophylactic vaccines that contain clinical-grade Toll-like receptor ligands (BCG, Typhim, Act-HIB) and prostaglandin E2 (VAC-DC). Stage III and IV melanoma patients were vaccinated via intranodal injection (12 patients) or combined intradermal/intravenous injection (16 patients) with VAC-DC loaded with keyhole limpet hemocyanin (KLH) and mRNA encoding tumor antigens gp100 and tyrosinase. Tumor antigen-specific T cell responses were monitored in blood and skin-test infiltrating-lymphocyte cultures. Almost all patients mounted prophylactic vaccine- or KLH-specific immune responses. Both after intranodal injection and after intradermal/intravenous injection, tumor antigen-specific immune responses were detected, which coincide with longer overall survival in stage IV melanoma patients. VAC-DC induce local and systemic CTC grade 2 and 3 toxicity, which is most likely caused by BCG in the maturation cocktail. The side effects were self-limiting or resolved upon a short period of systemic steroid therapy. We conclude that VAC-DC can induce functional tumor-specific responses. Unfortunately, toxicity observed after vaccination precludes the general application of VAC-DC, since in DC maturated with prophylactic vaccines BCG appears to be essential in the maturation cocktail.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-016-1796-7) contains supplementary material, which is available to authorized users.

Potential To Streamline Heterologous DNA Prime and NYVAC/Protein Boost HIV Vaccine Regimens in Rhesus Macaques by Employing Improved Antigens.

In a follow-up to the modest efficacy observed in the RV144 trial, researchers in the HIV vaccine field seek to substantiate and extend the results by evaluating other poxvirus vectors and combinations with DNA and protein vaccines. Earlier clinical trials (EuroVacc trials 01 to 03) evaluated the immunogenicity of HIV-1 clade C GagPolNef and gp120 antigens delivered via the poxviral vector NYVAC. These showed that a vaccination regimen including DNA-C priming prior to a NYVAC-C boost considerably enhanced vaccine-elicited immune responses compared to those with NYVAC-C alone. Moreover, responses were improved by using three as opposed to two DNA-C primes. In the present study, we assessed in nonhuman primates whether such vaccination regimens can be streamlined further by using fewer and accelerated immunizations and employing a novel generation of improved DNA-C and NYVAC-C vaccine candidates designed for higher expression levels and more balanced immune responses. Three different DNA-C prime/NYVAC-C+ protein boost vaccination regimens were tested in rhesus macaques. All regimens elicited vigorous and well-balanced CD8(+)and CD4(+)T cell responses that were broad and polyfunctional. Very high IgG binding titers, substantial antibody-dependent cellular cytotoxicity (ADCC), and modest antibody-dependent cell-mediated virus inhibition (ADCVI), but very low neutralization activity, were measured after the final immunizations. Overall, immune responses elicited in all three groups were very similar and of greater magnitude, breadth, and quality than those of earlier EuroVacc vaccines. In conclusion, these findings indicate that vaccination schemes can be simplified by using improved antigens and regimens. This may offer a more practical and affordable means to elicit potentially protective immune responses upon vaccination, especially in resource-constrained settings. Within the EuroVacc clinical trials, we previously assessed the immunogenicity of HIV clade C antigens delivered in a DNA prime/NYVAC boost regimen. The trials showed that the DNA prime crucially improved the responses, and three DNA primes with a NYVAC boost appeared to be optimal. Nevertheless, T cell responses were primarily directed toward Env, and humoral responses were modest. The aim of this study was to assess improved antigens for the capacity to elicit more potent and balanced responses in rhesus macaques, even with various simpler immunization regimens. Our results showed that the novel antigens in fact elicited larger numbers of T cells with a polyfunctional profile and a good Env-GagPolNef balance, as well as high-titer and Fc-functional antibody responses. Finally, comparison of the different schedules indicates that a simpler regimen of only two DNA primes and one NYVAC boost in combination with protein may be very efficient, thus showing that the novel antigens allow for easier immunization protocols.