Inhibition of a vaccine-induced anti-tumor B cell response by soluble protein antigen in the absence of continuing T cell help

Insertion of atypical glycans into the tumor antigen-binding site identifies DLBCLs with distinct origin and behavior

Glycosylation of the surface immunoglobulin (Ig) variable region is a remarkable follicular lymphoma-associated feature rarely seen in normal B cells. Here, we define a subset of diffuse large B-cell lymphomas (DLBCLs) that acquire N-glycosylation sites selectively in the Ig complementarity-determining regions (CDRs) of the antigen-binding sites. Mass spectrometry and X-ray crystallography demonstrate how the inserted glycans are stalled at oligomannose-type structures because they are buried in the CDR loops. Acquisition of sites occurs in ∼50% of germinal-center B-cell-like DLBCL (GCB-DLBCL), mainly of the genetic EZB subtype, irrespective of IGHV-D-J use. This markedly contrasts with the activated B-cell-like DLBCL Ig, which rarely has sites in the CDR and does not seem to acquire oligomannose-type structures. Acquisition of CDR-located acceptor sites associates with mutations of epigenetic regulators and BCL2 translocations, indicating an origin shared with follicular lymphoma. Within the EZB subtype, these sites are associated with more rapid disease progression and with significant gene set enrichment of the B-cell receptor, PI3K/AKT/MTORC1 pathway, glucose metabolism, and MYC signaling pathways, particularly in the fraction devoid of MYC translocations. The oligomannose-type glycans on the lymphoma cells interact with the candidate lectin dendritic cell-specific intercellular adhesion molecule 3 grabbing non-integrin (DC-SIGN), mediating low-level signals, and lectin-expressing cells form clusters with lymphoma cells. Both clustering and signaling are inhibited by antibodies specifically targeting the DC-SIGN carbohydrate recognition domain. Oligomannosylation of the tumor Ig is a posttranslational modification that readily identifies a distinct GCB-DLBCL category with more aggressive clinical behavior, and it could be a potential precise therapeutic target via antibody-mediated inhibition of the tumor Ig interaction with DC-SIGN-expressing M2-polarized macrophages.

Exploring the pathways to chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), increasing knowledge of the biology of the tumor cells has led to transformative improvements in our capacity to assess and treat patients. The dependence of tumor cells on surface immunoglobulin receptor signaling, survival pathways, and accessory cells within the microenvironment has led to a successful double-barreled attack with designer drugs. Studies have revealed that CLL should be classified based on the mutational status of the expressed IGHV sequences into 2 diseases, either unmutated (U) or mutated (M) CLL, each with a distinctive cellular origin, biology, epigenetics/genetics, and clinical behavior. The origin of U-CLL lies among the natural antibody repertoire, and dominance of IGHV1-69 reveals a superantigenic driver. In both U-CLL and M-CLL, a calibrated stimulation of tumor cells by self-antigens apparently generates a dynamic reiterative cycle as cells, protected from apoptosis, transit between blood and tissue sites. But there are differences in outcome, with the balance between proliferation and anergy favoring anergy in M-CLL. Responses are modulated by an array of microenvironmental interactions. Availability of T-cell help is a likely determinant of cell fate, the dependency on which varies between U-CLL and M-CLL, reflecting the different cells of origin, and affecting clinical behavior. Despite such advances, cell-escape strategies, Richter transformation, and immunosuppression remain as challenges, which only may be met by continued research into the biology of CLL.

Laboratory Mice - A Driving Force in Immunopathology and Immunotherapy Studies of Human Multiple Myeloma

Mouse models of human cancer provide an important research tool for elucidating the natural history of neoplastic growth and developing new treatment and prevention approaches. This is particularly true for multiple myeloma (MM), a common and largely incurable neoplasm of post-germinal center, immunoglobulin-producing B lymphocytes, called plasma cells, that reside in the hematopoietic bone marrow (BM) and cause osteolytic lesions and kidney failure among other forms of end-organ damage. The most widely used mouse models used to aid drug and immunotherapy development rely on in vivo propagation of human myeloma cells in immunodeficient hosts (xenografting) or myeloma-like mouse plasma cells in immunocompetent hosts (autografting). Both strategies have made and continue to make valuable contributions to preclinical myeloma, including immune research, yet are ill-suited for studies on tumor development (oncogenesis). Genetically engineered mouse models (GEMMs), such as the widely known Vκ*MYC, may overcome this shortcoming because plasma cell tumors (PCTs) develop de novo (spontaneously) in a highly predictable fashion and accurately recapitulate many hallmarks of human myeloma. Moreover, PCTs arise in an intact organism able to mount a complete innate and adaptive immune response and tumor development reproduces the natural course of human myelomagenesis, beginning with monoclonal gammopathy of undetermined significance (MGUS), progressing to smoldering myeloma (SMM), and eventually transitioning to frank neoplasia. Here we review the utility of transplantation-based and transgenic mouse models of human MM for research on immunopathology and -therapy of plasma cell malignancies, discuss strengths and weaknesses of different experimental approaches, and outline opportunities for closing knowledge gaps, improving the outcome of patients with myeloma, and working towards a cure.

Celebrating 20 Years of IGHV Mutation Analysis in CLL

The division of CLL into 2 broad subsets with highly significant differences in clinical behavior was reported in 2 landmark papers in Blood in 1999.^1,2 The simple analysis of the mutational status of the IGV regions provided both a prognostic indicator and an insight into the cellular origins. Derivation from B cells with very low or no IGV mutations generally leads to a more aggressive disease course than derivation from B cells with higher levels. This finding focused attention on surface Ig (sIg), the major B-cell receptor, and revealed dynamic antigen engagement in vivo as a tumor driver. It has also led to new drugs aimed at components of the intracellular activation cascades. After 20 years, the 2 senior authors of those papers have looked at the history of the observations and at the increasing understanding of the role of sIg in CLL that have emanated from them. As in the past, studies of CLL have provided a link between biology and the clinic, enabling more precise targeting which attacks critical pathways but minimizes side effects.

A novel recombinant 6Aβ15-THc-C chimeric vaccine (rCV02) mitigates Alzheimer's disease-like pathology, cognitive decline and synaptic loss in aged 3 × Tg-AD mice

Alzheimer's disease (AD) is a neurodegenerative disorder that impairs memory and cognition. Targeting amyloid-β (Aβ) may be currently the most promising immunotherapeutic strategy for AD. In this study, a recombinant chimeric 6Aβ15-THc-C immunogen was formulated with alum adjuvant as a novel Aβ B-cell epitope candidate vaccine (rCV02) for AD. We examined its efficacy in preventing the cognitive deficit and synaptic impairment in 3 × Tg-AD mice. Using a toxin-derived carrier protein, the rCV02 vaccine elicited robust Aβ-specific antibodies that markedly reduced AD-like pathology and improved behavioral performance in 3 × Tg-AD mice. Along with the behavioral improvement in aged 3 × Tg-AD mice, rCV02 significantly decreased calpain activation concurrent with reduced soluble Aβ or oligomeric forms of Aβ, probably by preventing dynamin 1 and PSD-95 degradation. Our data support the hypothesis that reducing Aβ levels in rCV02-immunized AD mice increases the levels of presynaptic dynamin 1 and postsynaptic PSD-95 allowing functional recovery of cognition. In conclusion, this novel and highly immunogenic rCV02 shows promise as a new candidate prophylactic vaccine for AD and may be useful for generating rapid and strong Aβ-specific antibodies in AD patients with pre-existing memory Th cells generated after immunization with conventional tetanus toxoid vaccine.

A plant-expressed conjugate vaccine breaks CD4(+) tolerance and induces potent immunity against metastatic Her2(+) breast cancer

Passive antibody therapy for cancer is an effective but costly treatment modality. Induction of therapeutically potent anticancer antibodies by active vaccination is an attractive alternative but has proven challenging in cancer due to tolerogenic pressure in patients. Here, we used the clinically relevant cancer target Her2, known to be susceptible to targeting by antibody therapy, to demonstrate how potent antibody can be induced by vaccination. A novel 44kD Her2 protein fragment was generated and found to be highly effective at inducing anti-Her2 antibody including trastuzumab-like reactivities. In the tolerant and spontaneous BALB-neuT mouse model of metastatic breast cancer this Her2-targeting vaccine was only effective if the fragment was conjugated to a foreign immunogenic carrier; Fragment C of tetanus toxin. Only the conjugate vaccine induced high affinity anti-Her2 antibody of multiple isotypes and suppressed tumor development. The magnitude of CD4(+) T-cell help and breadth of cytokines secreted by the CD4(+) T helper (Th) cells induced to the foreign antigen was critical. We used a highly efficient plant-based bio-manufacturing process for protein antigens, magnICON, for vaccine expression, to underpin feasibility of future clinical testing. Hence, our novel Her2-targeting conjugate vaccine combines preclinical efficacy with clinical deliverability, thus setting the scene for therapeutic testing.

Novel receptor-derived cyclopeptides to treat heart failure caused by anti-β1-adrenoceptor antibodies in a human-analogous rat model

Despite recent therapeutic advances the prognosis of heart failure remains poor. Recent research suggests that heart failure is a heterogeneous syndrome and that many patients have stimulating auto-antibodies directed against the second extracellular loop of the β1 adrenergic receptor (β1EC2). In a human-analogous rat model such antibodies cause myocyte damage and heart failure. Here we used this model to test a novel antibody-directed strategy aiming to prevent and/or treat antibody-induced cardiomyopathy. To generate heart failure, we immunised n = 76/114 rats with a fusion protein containing the human β1EC2 (amino-acids 195-225) every 4 weeks; n = 38/114 rats were control-injected with 0.9% NaCl. Intravenous application of a novel cyclic peptide mimicking β1EC2 (β1EC2-CP, 1.0 mg/kg every 4 weeks) or administration of the β1-blocker bisoprolol (15 mg/kg/day orally) was initiated either 6 weeks (cardiac function still normal, prevention-study, n = 24 (16 treated vs. 8 untreated)) or 8.5 months after the 1st immunisation (onset of cardiomyopathy, therapy-study, n = 52 (40 treated vs. 12 untreated)); n = 8/52 rats from the therapy-study received β1EC2-CP/bisoprolol co-treatment. We found that β1EC2-CP prevented and (alone or as add-on drug) treated antibody-induced cardiac damage in the rat, and that its efficacy was superior to mono-treatment with bisoprolol, a standard drug in heart failure. While bisoprolol mono-therapy was able to stop disease-progression, β1EC2-CP mono-therapy -or as an add-on to bisoprolol- almost fully reversed antibody-induced cardiac damage. The cyclo¬peptide acted both by scavenging free anti-β1EC2-antibodies and by targeting β1EC2-specific memory B-cells involved in antibody-production. Our model provides the basis for the clinical translation of a novel double-acting therapeutic strategy that scavenges harmful anti-β1EC2-antibodies and also selectively depletes memory B-cells involved in the production of such antibodies. Treatment with immuno-modulating cyclopeptides alone or as an add-on to β1-blockade represents a promising new therapeutic option in immune-mediated heart failure.

Plant virus particles carrying tumour antigen activate TLR7 and Induce high levels of protective antibody

Induction of potent antibody is the goal of many vaccines targeted against infections or cancer. Modern vaccine designs that use virus-like particles (VLP) have shown efficacy for prophylactic vaccination against virus-associated cancer in the clinic. Here we used plant viral particles (PVP), which are structurally analogous to VLP, coupled to a weak idiotypic (Id) tumour antigen, as a conjugate vaccine to induce antibody against a murine B-cell malignancy. The Id-PVP vaccine incorporates a natural adjuvant, the viral ssRNA, which acts via TLR7. It induced potent protective anti-Id antibody responses in an in vivo mouse model, superior to the "gold standard" Id vaccine, with prevalence of the IgG2a isotype. Combination with alum further increased antibody levels and maintained the IgG2a bias. Engagement of TLR7 in vivo was followed by secretion of IFN-α by plasmacytoid dendritic cells and by activation of splenic CD11chi conventional dendritic cells. The latter was apparent from up-regulation of co-stimulatory molecules and from secretion of a wide range of inflammatory cytokines and chemokines including the Th1-governing cytokine IL-12, in keeping with the IgG2a antibody isotype distribution. PVP conjugates are a novel cancer vaccine design, offering an attractive molecular form, similar to VLP, and providing T-cell help. In contrast to VLP, they also incorporate a safe "in-built" ssRNA adjuvant.

High-affinity memory B cells induced by conjugate vaccines against weak tumor antigens are vulnerable to nonconjugated antigen

Induction of antibody-mediated immunity against hematologic malignancies requires CD4+ T-cell help, but weak tumor antigens generally fail to induce adequate T-cell responses, or to overcome tolerance. Conjugate vaccines can harness alternative help to activate responses, but memory B cells may then be exposed to leaking tumor-derived antigen without CD4+ T-cell support. We showed previously using lymphoma-derived idiotypic antigen that exposure to “helpless” antigen silences the majority of memory IgG+ B cells. Transfer experiments now indicate that silencing is permanent. In marked contrast to IgG, most coexisting IgM+ memory B cells exposed to “helpless” antigen survive. Confirmation in a hapten (NP) model allowed measurement of affinity, revealing this, rather than isotype, as the determinant of survival. IgM+ B cells had Ig variable region gene usage similar to IgG but with fewer somatic mutations. Survival of memory B cells appears variably controlled by affinity for antigen, allowing a minority of low affinity IgG+, but most IgM+, memory B cells to escape deletion in the absence of T-cell help. The latter remain, but the majority fail to undergo isotype switch. These findings could apply to other tumor antigens and are relevant for vaccination strategies aimed to induce long-term antibody.

A high-affinity T-helper epitope enhances peptide-pulsed dendritic cell-based vaccine

The NV epitope, a dominant helper determinant from the circumsporozoite antigen of Plasmodium falciparum, is strongly immunogenic and can provide help for cytotoxic T-lymphocyte (CTL) activation. In this study, we evaluated whether the addition of NV peptide can augment the efficacy of peptide-pulsed dendritic cell (DC) immunization in vivo. Using B16 melanoma as tumor model, we demonstrated that DCs pulsed with both NV and gp100 (a melanoma-specific antigen) peptide enhanced immune priming and protection from tumor challenge in vivo. Further, we showed the mechanisms of the NV epitope that help CTL activation; MHC-II-restricted NV peptide induced dramatically more effective helper cells, with a higher level of CD40L expression and IFN-γ production, which, in turn, more effectively conditioned DCs for CTL activation. The improved helper cells also induced greater IL-12 production by DCs, accounting for the reciprocal T-helper polarization to Th1, and increased the expression of costimulatory molecules. Collectively, these findings demonstrate that NV peptide in addition to tumor antigen-pulsed DC immunizations augment helper cell activation, which in turn promotes maturation of DC, and enhance in vivo antitumor activity.

The human G1m1 allotype associates with CD4+ T-cell responsiveness to a highly conserved IgG1 constant region peptide and confers an asparaginyl endopeptidase cleavage site

The human G1m1 allotype comprises two amino acids, D12 and L14, in the CH3 domain of IGHG1. Although the G1m1 allotype is prevalent in human populations, ∼40% of Caucasiods are homozygous for the nG1m1 allotype corresponding to E12 and M14. Peptides derived from the G1m1 region were tested for their ability to induce CD4+ T-cell proliferative responses in vitro. A peptide immediately downstream from the G1m1 sequence was recognized by CD4+ T cells in a large percentage of donors (peptide CH3₁₅₋₂₉). CD4+ T-cell proliferative responses to CH3₁₅₋₂₉ were found at an increased frequency in nG1m1 homozygous donors. Homozygous nG1m1 donors possessing the HLA-DRB1^*07 allele displayed the highest magnitudes of proliferation. CD4+ T cells from donors homozygous for nG1m1 proliferated to G1m1-carrying Fc-fragment proteins, whereas CD4+ T cells from G1m1 homozygous donors did not. The G1m1 sequence creates an enzymatic cleavage site for asparaginyl endopeptidase in vitro. Proteolytic activity at D12 may allow the presentation of the CH3₁₅₋₂₉ peptide, which in turn may result in the establishment of tolerance to this peptide in G1m1-positive donors. Homozygous nG1m1 patients may be more likely to develop CD4+ T-cell-mediated immune responses to therapeutic antibodies carrying the G1m1 allotype.

Idiotype vaccine strategies for improving outcomes in follicular lymphoma

BACKGROUND

Follicular lymphoma (FL) is a common indolent lymphoma associated with a relapsing course. Preclinical models and clinical studies demonstrate that immunizing FL patients against their own tumor idiotype induces humoral and cellular immunity and supresses tumor growth.

METHODS

We review idiotype vaccine strategies that have been tested in FL patients in frontline and relapsed settings to examine the safety and efficacy of this approach.

RESULTS

Several Phase II trials of recombinant or hybridoma-produced vaccines or vaccines combined with other immunotherapy demonstrate cellular and humoral anti-idiotype responses and clinical responses, indicating that idiotype vaccines provide promise for improving FL outcomes.

CONCLUSION

These strategies are now being evaluated in Phase III trials but have yet to demonstrate clear advantages in progression-free survival.

DNA vaccines: precision tools for activating effective immunity against cancer

DNA vaccination has suddenly become a favoured strategy for inducing immunity. The molecular precision offered by gene-based vaccines, together with the facility to include additional genes to direct and amplify immunity, has always been attractive. However, the apparent failure to translate operational success in preclinical models to the clinic, for reasons that are now rather obvious, reduced initial enthusiasm. Recently, novel delivery systems, especially electroporation, have overcome this translational block. Here, we assess the development, current performance and potential of DNA vaccines for the treatment of cancer.

BiovaxID idiotype vaccination: active immunotherapy for follicular lymphoma

Although advanced-stage follicular lymphoma (FL) has been considered incurable with standard therapy, novel strategies that utilize immunotherapy provide opportunities for prolonging disease-free survival. While passive immunotherapy with antibodies targeting the CD20 antigen on B cells has been the most widely applied lymphoma immunotherapy, active immunization with vaccines derived from the immunoglobulin idiotype present on the surface of FL provides an opportunity to induce specific humoral and cellular immune responses to the tumor, and have been demonstrated to produce significant benefits in prolonging disease-free survival. Promoting the benefits of all forms of immunotherapy will likely depend upon improving complete remission rates with initial treatment. BiovaxID, a patient-specific idiotype vaccine, has demonstrated durable remissions when administered to FL patients in first complete remission along with keyhole limpet hemocyanin and granulocyte-macrophage colony-stimulating factor, and is now undergoing evaluation in a pivotal Phase III clinical trial.

Tumor-associated embryonic antigen-expressing vaccines that target CCR6 elicit potent CD8+ T cell-mediated protective and therapeutic antitumor immunity

Despite its potency, the wider use of immunotherapy for B cell malignancies is hampered by the lack of well-defined tumor-specific Ags. In this study, we demonstrate that an evolutionarily conserved 37-kDa immature laminin receptor protein (OFA-iLRP), a nonimmunogenic embryonic Ag expressed by a variety of tumors, is rendered immunogenic if targeted to the APCs using the CCR6 ligands MIP3alpha/CCL20 and mDF2beta. The CCR6 targeting facilitated efficient Ag cross-presentation and induction of tumor-neutralizing CTLs. Although the Ag targeting alone, without activation of dendritic cells (DCs), is proposed to induce tolerance, and MIP3alpha does not directly activate DCs, the MIP3alpha-based vaccine efficiently induced protective and therapeutic antitumor responses. The responses were as strong as those elicited by the OFA-iLRP fusions with moieties that activated DCs and Th1-type cytokine responses, mDF2beta, or mycobacterial Hsp70 Ag. Although the same cDNA encodes the dimerized high-affinity mature 67-kDa mLRP that is expressed in normal tissues to stabilize the binding of laminin to cell surface integrins, the vaccines expressing OFA-iLRP elicited long-term protective CD8(+) T cell-mediated memory responses against syngeneic B cell lymphoma, indicating the potential application of these simple vaccines as preventive and therapeutic formulations for human use.

Chemokine-idiotype fusion DNA vaccines are potentiated by bivalency and xenogeneic sequences

V regions of monoclonal Ig express an exquisite B-cell tumor–specific antigen called idiotype (Id). Id is a weak antigen and it is important to improve immunogenicity of Id vaccines. Chemokine receptors are expressed on antigen-presenting cells (APCs) and are promising targets for Id vaccines. Here we compare monomeric and dimeric forms of MIP-1α and RANTES that target Id to APCs in a mouse B lymphoma (A20) and a multiple myeloma model (MOPC315). MIP-1α was more potent than RANTES. The dimeric proteins were more potent than monomeric equivalents in short-term assays. When delivered in vivo by intramuscular injection of plasmids followed by electroporation, dimeric proteins efficiently primed APCs in draining lymph nodes for activation and proliferation of Id-specific CD4+ T cells. Good anti-Id antibody responses were obtained, and mice immunized only once were 60% to 80% protected in both tumor models. CD8+ T cells contributed to the protection. Antibody responses and tumor protection were reduced when the human Ig hinge = CH3 dimerization motif was replaced with syngeneic mouse counterparts, indicating that tumor-protective responses were dependent on xenogeneic sequences. The results suggest that bivalency and foreign sequences combine to increase the efficiency of chemokine-Id DNA vaccines.