Incorporation of CD40 ligand or granulocyte-macrophage colony stimulating factor into Hantaan virus (HTNV) virus-like particles significantly enhances the long-term immunity potency against HTNV infection

PURPOSE

Hantavirus infections cause severe haemorrhagic fever with renal syndrome (HFRS) in humans and are associated with high fatality rates. In 2017, numerous outbreaks were reported in China and Germany. This represents a significant public-healthcare issue with no effective HFRS vaccines that offer a long-term immune response. In this study, we investigated the long-term humoral and cellular immune responses and protective immunity of Hantaan virus (HTNV) granulocyte-macrophage colony stimulating factor (GM-CSF) and CD40 ligand (CD40L) virus-like particles (VLPs) in mice.

METHODOLOGY

GM-CSF and CD40L VLPs were constructed via co-transfection of pCI-S and pCI-M-CD40L, and pCI-S and pCI-M-GM-CSF, into dihydrofolatereductase (dhfr)-deficient Chinese hamster ovary cells, respectively. Mice were immunized with HTNV VLPs 2 weeks apart. The animals were challenged 6 months after immunization. Specific and neutralizing antibodies were assessed by ELISA; IFN-γ was measured by enzyme-linked immunospot (ELISpot) assay and effectiveness by cytotoxic T lymphocyte (CTL) cytotoxicity assays. Nucleic acid loads of HTNV were tested by quantitative real-time PCR and viral antigen was detected via indirect ELISA. Pathological alterations were detected via haematoxylin-eosin staining.

RESULTS

GM-CSF and CD40L VLPs provided stable, long-term protection with a high titre of neutralizing antibody in mice 6 months after immunization. Furthermore, VLPs increased HTNV-specific cellular immune responses via higher expression of IFN-γ and CTL responses. HTNV challenge assay results showed long-term protection against HFRS. No significant pathological alteration was observed in the organs of mice after immunization.

CONCLUSION

This is, to the best of our knowledge, the first report demonstrating the long-term potency of HTNV VLP vaccines against HTNV infection and offers new insights into HTNV vaccine development.

A phase I/randomized phase II study of GM.CD40L vaccine in combination with CCL21 in patients with advanced lung adenocarcinoma

The GM.CD40L vaccine, which recruits and activates dendritic cells, migrates to lymph nodes, activating T cells and leading to systemic tumor cell killing. When combined with the CCL21 chemokine, which recruits T cells and enhances T-cell responses, additive effects have been demonstrated in non-small cell lung cancer mouse models. Here, we compared GM.CD40L versus GM.CD40L plus CCL21 (GM.CD40L.CCL21) in lung adenocarcinoma patients with ≥ 1 line of treatment. In this phase I/II randomized trial (NCT01433172), patients received intradermal vaccines every 14 days (3 doses) and then monthly (3 doses). A two-stage minimax design was used. During phase I, no dose-limiting toxicities were shown in three patients who received GM.CD40L.CCL21. During phase II, of evaluable patients, 5/33 patients (15.2%) randomized for GM.DCD40L (p = .023) and 3/32 patients (9.4%) randomized for GM.DCD40L.CCL21 (p = .20) showed 6-month progression-free survival. Median overall survival was 9.3 versus 9.5 months with GM.DCD40L versus GM.DCD40L.CCL21 (95% CI 0.70–2.25; p = .44). For GM.CD40L versus GM.CD40L.CCL21, the most common treatment-related adverse events (TRAEs) were grade 1/2 injection site reaction (51.4% versus 61.1%) and grade 1/2 fatigue (35.1% versus 47.2%). Grade 1 immune-mediated TRAEs were isolated to skin. No patients showed evidence of pseudo-progression or immune-related TRAEs of grade 1 or greater of pneumonitis, endocrinopathy, or colitis, and none discontinued treatment due to toxicity. Although we found no significant associations between vaccine immunogenicity and outcomes, in limited biopsies, one patient treated with GMCD40L.CCL21 displayed abundant tumor-infiltrating lymphocytes. This possible effectiveness warrants further investigation of GM.CD40L in combination approaches.

B lymphocytes can be activated to act as antigen presenting cells to promote anti-tumor responses

Immune evasion by tumors includes several different mechanisms, including the inefficiency of antigen presenting cells (APCs) to trigger anti-tumor T cell responses. B lymphocytes may display a pro-tumoral role but can also be modulated to function as antigen presenting cells to T lymphocytes, capable of triggering anti-cancer immune responses. While dendritic cells, DCs, are the best APC population to activate naive T cells, DCs or their precursors, monocytes, are frequently modulated by tumors, displaying a tolerogenic phenotype in cancer patients. In patients with cervical cancer, we observed that monocyte derived DCs are tolerogenic, inhibiting allogeneic T cell activation compared to the same population obtained from patients with precursor lesions or cervicitis. In this work, we show that B lymphocytes from cervical cancer patients respond to treatment with sCD40L and IL-4 by increasing the CD80+CD86+ population, therefore potentially increasing their ability to activate T cells. To test if B lymphocytes could actually trigger anti-tumor T cell responses, we designed an experimental model where we harvested T and B lymphocytes, or dendritic cells, from tumor bearing donors, and after APC stimulation, transplanted them, together with T cells into RAG1-/- recipients, previously injected with tumor cells. We were able to show that anti-CD40 activated B lymphocytes could trigger secondary T cell responses, dependent on MHC-II expression. Moreover, we showed that dendritic cells were resistant to the anti-CD40 treatment and unable to stimulate anti-tumor responses. In summary, our results suggest that B lymphocytes may be used as a tool for immunotherapy against cancer.

Phosphoinositide 3-kinase mediates CD40 ligand-induced oxidative stress and endothelial dysfunction via Rac1 and NADPH oxidase 2

OBJECTIVES

CD40 ligand (CD40L) has been implicated as an inducer of reactive oxygen species (ROS) generation in endothelial cells, but definitive evidence for this and the in vivo relevance haves not been demonstrated fully. We thus investigated whether phosphoinositide 3-kinase (PI3K) was linked to ROS generation and endothelial reactivity in response to CD40L.

METHODS AND RESULTS

CD40L treatment activated PI3K activity by regulating the association between PI3K p85 and the CD40 receptor. CD40L exposure also stimulated the GTPase Rac1, which is known to activate NADPH oxidases, and enhanced ROS formation, whereas PI3K inhibition or depletion by small interfering RNA (siRNA) prevented these responses. Subsequently, PI3K overexpression activated Rac1 and increased ROS generation. These responses were not observed in the presence of inactive Rac1 or siRNA against the NADPH oxidase subunit NOX2. Protein kinase Czeta mediates PI3K-regulated NADPH oxidase activation by promoting cellular p47phox translocation. Importantly, PI3K inhibition prevented CD40L-mediated ROS generation and endothelial dysfunction in a mouse model. In summary, PI3K mediates CD40L-induced ROS production and subsequent endothelial dysfunction.

CONCLUSIONS

Targeting PI3K may provide a new therapeutic approach in diseases associated with oxidative stress and endothelial dysfunction.

The Potential of Gene Transfer into Primary B-CLL Cells Using Recombinant Virus Vectors

Despite recent advances, chronic lymphocytic leukemia (CLL) as the most common leukemia remains a largely incurable disease. Modern treatment options include novel drugs like purine analogues, monoclonal antibodies and transplantation strategies. Moreover, gene transfer of immunostimulatory molecules is another, but still experimental approach that can be used to potentiate immune responses against leukemic cells. CD40 ligand (CD40L) was shown to be a promising molecule for immunotherapy of B-CLL playing a critical role in immune activation. However, CLL B cells are resistant to transduction with most currently available vector systems. Improving the efficiency and specificity of gene vectors is critical for the success of gene therapy in this area. Using replication defective adenovirus encoding CD40L (Ad-CD40L), immunologic and clinical responses were seen in CLL patients after infusion of autologous Ad-CD40L-CLL cells in a recent phase I trial. Due to the immunogenic nature of adenovirus vectors, alternative vector systems are currently explored. Recombinant adeno-associated virus (rAAV) was shown to enable efficient transduction of primary B-CLL cells. By use of a library of AAV clones with randomly modified capsids, receptor-targeting mutants with a tropism for CLL cells can be selected. Furthermore, helper-virus free Epstein-Barr virus (EBV)-based gene transfer vectors hold promise for development of CLL-targeted vaccines after remaining safety issues will be resolved. Herpes simplex virus (HSV)-based vectors, especially HSV amplicons, have favorable features for B-CLL gene transfer including high transduction efficiency, ability to infect postmitotic cells and a large packaging capacity. The challenge for the future will be to transfer these alternative vector systems into clinic and allow the detection of a CLL-specific immune response by use of defined tumor antigens. This will make it possible to establish the potential clinical role of gene therapy for CLL patients.

Expression of CD40 and growth-inhibitory activity of CD40 ligand in ovarian cancer cell lines

OBJECTIVE

Soluble recombinant human CD40 ligand trimer (rhuCD40Lt) has shown antitumor activity in preclinical and clinical studies. We evaluated the effect of rhuCD40Lt on epithelial ovarian carcinoma (EOC) cell lines.

METHODS

Expression of the receptor, CD40, was determined by reverse transcriptase-polymerase chain reaction and flow cytometry, and antiproliferative effects of rhuCD40Lt, either alone or in combination with recombinant interferon-gamma (rIFN-gamma), were examined in 8 EOC lines.

RESULTS

Expression of CD40 was elevated in 5 out of 8 EOC cell lines examined by flow cytometry, and the presence of CD40 transcripts was detected by RT-PCR in all 8 cell lines. CD40 expression was increased by rIFN-gamma, but treatment with rhuCD40Lt decreased CD40 expression in 4 of the 5 lines that had shown elevated CD40 expression. rhuCD40Lt had a growth-inhibitory effect on 2774 cells, which also exhibited the highest level of CD40 expression. Growth-inhibitory effect of rhuCD40Lt was additive with rIFN-gamma on 2774, NMP-1, a cisplatin-resistant subline of OVCAR3, and HEY cell lines. The number of apoptotic tumor cells was increased following treatment with rhuCD40Lt.

CONCLUSIONS

CD40 is expressed on EOC cell lines, and expression was found at the transcript level in all of the EOC lines examined. rIFN-gamma enhances CD40 expression, though a decrease in CD40 expression was observed following treatment with rhuCD40Lt. Growth-inhibitory activity of rhuCD40Lt on EOC lines that express CD40 could be enhanced when rhuCD40Lt treatment was combined with rIFN-gamma. These results suggest that future studies of the combination of rhuCD40Lt and rIFN-gamma might warrant consideration.

Proangiogenic function of CD40 ligand-CD40 interactions

Angiogenesis is a characteristic component of cell-mediated immune inflammation. However, little is known of the immunologic mediators of angiogenesis factor production. Interactions between CD40 ligand (CD40L) and CD40 have been shown to have pluripotent functions in inflammation, including the production of cytokines, chemokines, as well as the angiogenesis factor, vascular endothelial growth factor (VEGF), by endothelial cells. In this study we found that treatment of cultured human endothelial cells with an anti-CD40 Ab (to ligate CD40) resulted in the expression of several other angiogenesis factors, including fibroblast growth factor-2 and the receptors Flt-1 and Flt-4. To determine the proangiogenic effect of CD40L in vivo, human skin was allowed to engraft on SCID mice for 6 wk. These healed human skins express CD40 on resident endothelial cells and monocyte/macrophages, but not on CD20-expressing B cells. Skins were injected with saline, untransfected murine fibroblasts, or murine fibroblasts stably transfected with human CD40L. We found that the injection of CD40L-expressing cells, but not control cells, resulted in the in vivo expression of several angiogenesis factors (including VEGF and fibroblast growth factor) and a marked angiogenesis reaction. Mice treated with anti-VEGF failed to elicit an angiogenesis reaction in response to injection of CD40L-expressing cells, suggesting that the proangiogenic effect of CD40L in vivo is VEGF dependent. These observations imply that ligation of CD40 at a peripheral inflammatory site is of pathophysiological importance as a mediator of both angiogenesis and inflammation.

The use of lentiviral vectors in gene therapy of leukemia: combinatorial gene delivery of immunomodulators into leukemia cells by state-of-the-art vectors

Our goal is to develop cell vaccines against leukemia cells, genetically modified to express molecules with potent immune-stimulatory capacities. Pre-clinical evaluation of this approach in murine models has demonstrated efficient anti-leukemic responses with the expression of immunomodulators, in particular GM-CSF and CD80, in irradiated cell vaccines. We have previously shown efficient insertion of GM-CSF and CD80 genes into primary human leukemia cells with the use of second and third generation self-inactivating (SIN) lentiviral vectors (Blood 96 (2000), 1317; Leukemia 16 (2002), 1645). The advantages of lentiviral vectors for development of autologous leukemia cell vaccines include: (1) efficient and consistent gene delivery; (2) high levels of transgene expression; (3) persistent expression of the transduced gene; (4) no viral proteins, as only the transduced gene is expressed; (5) no undesirable cytotoxic effects, and; (6) simplicity of use [leukemia cells are exposed to vector(s) only once]. In this work, we evaluated the insertion of the central polypurine tract and the central termination sequence into a SIN lentiviral vector encoding for GM-CSF and CD80, which significantly enhanced the transduction efficiency of primary leukemia cells and provided higher levels of GM-CSF and CD80 co-expression. We also demonstrate a methodology to deliver simultaneously a combination of immunomodulatory molecules (GM-CSF, CD80, IL-4, and CD40L) to activate different pathways of immune stimulation. Therefore, lentiviral vectors offer a simple, versatile, and reliable approach for engineering leukemic cells for use as cell vaccines.

Targeting with bovine CD154 enhances humoral immune responses induced by a DNA vaccine in sheep

CD40-CD154 interactions play an important role in regulating humoral and cell-mediated immune responses. Recently, these interactions have been exploited for the development of therapeutic and preventive treatments. The objective of this study was to test the ability of bovine CD154 to target a plasmid-encoded Ag to CD40-expressing APCs. To achieve this, a plasmid coding for bovine CD154 fused to a truncated secreted form of bovine herpesvirus 1 glycoprotein D (tgD), pSLIAtgD-CD154, was constructed. The chimeric tgD-CD154 was expressed in vitro in COS-7 cells and reacted with both glycoprotein D- and CD154-specific Abs. Both tgD and tgD-CD154 were capable of binding to epithelial cells, whereas only tgD-CD154 bound to B cells. Furthermore, dual-labeling of ovine PBMCs revealed that tgD-CD154 was bound by primarily B cells. The functional integrity of the tgD-CD154 chimera was confirmed by the induction of both IL-4-dependent B cell proliferation and tgD-specific lymphoproliferative responses in vitro. Finally, sheep immunized with pSLIAtgD-CD154 developed a more rapid primary tgD-specific Ab response and a significantly stronger tgD-specific secondary response when compared with animals immunized with pSLIAtgD and control animals. Similarly, virus-neutralizing Ab titers were significantly higher after secondary immunization with pSLIAtgD-CD154. These results demonstrate that using CD154 to target plasmid-expressed Ag can significantly enhance immune responses induced by a DNA vaccine.

Recombinant CD40 ligand administration does not decrease intensity of Pneumocystis carinii infection in scid mice

X-linked Hyper IgM Syndrome (HIM) is a rare congenital immunodeficiency recently demonstrated to be caused by a mutation in the gene encoding CD40 ligand. These patients are susceptible to Pneumocystis carinii pneumonia, which implies an important role for CD40L in host defense against P. carinii. In this study we undertook to investigate whether treatment of P. carinii infected scid mice with murine recombinant CD40 ligand trimer (muCD40L) for 21 days would facilitate clearance of the organisms. We found no significant difference in organism burden in treated compared to control animals. Therefore in this model treatment with muCD40L alone is ineffective in clearing P. carinii infection.

Activation-induced cell death of aggressive histology lymphomas by CD40 stimulation: induction of bax

CD40 is present on both normal and neoplastic B-lineage cells. CD40 stimulation of normal B cells has been shown to promote normal growth and differentiation, whereas aggressive histology B lymphomas are growth inhibited. The inhibition of neoplastic B-cell growth is believed to occur via activation-induced cell death in which stimuli that typically promote the growth of normal cells prevent the growth of their neoplastic counterparts. We show here that CD40 stimulation using either a soluble recombinant human CD40 ligand (srhCD40L) or anti-CD40 monoclonal antibody resulted in apoptosis of human Burkitt lymphoma cell lines. Additional studies examining the mechanism of CD40-mediated death revealed an increase in bax messenger RNA with a subsequent increase in Bax protein in the mitochondria of the treated cells. In vitro exposure of the cells to bax antisense oligonucleotides resulted in a significant decline in Bax protein levels and partial protection from CD40-mediated death, indicating that induction of Bax was at least one mechanism underlying this inhibitory effect of CD40 stimulation on lymphomas. When immunodeficient mice bearing Burkitt lymphoma were treated with srhCD40L, significant increases in survival were observed indicating a direct antitumor effect as a result of CD40 stimulation in vivo. Overall, these results demonstrate that CD40 ligation of aggressive histology B-lymphoma cells results in inhibition both in vitro and in vivo and thus may be of potential clinical use in their treatment.

Latent sensitivity to Fas-mediated apoptosis after CD40 ligation may explain activity of CD154 gene therapy in chronic lymphocytic leukemia

Patients with chronic lymphocytic leukemia (CLL) treated with adenovirus (Ad)-CD154 (CD40L) gene therapy experience reductions in leukemia cell counts and lymph node size associated with induction of the death receptor Fas (CD95). CD4 T cell lines can induce apoptosis of CD40-activated CLL cells via a CD95 ligand (CD95-L)-dependent mechanism. To examine whether CD95-L was sufficient to induce cytolysis of CD40-activated CLL cells, we used Chinese hamster ovary cells transfected with CD95-L as cytotoxic effector cells. CD40-activated CLL cells were initially resistant to CD95-mediated apoptosis despite high-level expression of CD95. However, after 72 h, CLL cells from seven of seven patients became increasingly sensitive to CD95-mediated apoptosis. This sensitivity correlated with a progressive decline in Flice-inhibitory protein (FLIP), which was induced within 24 h of CD40 ligation. Down-regulation of FLIP with an antisense oligonucleotide or a pharmacologic agent, however, was not sufficient to render CLL cells sensitive to CD95-mediated apoptosis in the 24-72 h after CD40 activation. Although the levels of pro-Caspase-8 appeared sufficient, inadequate levels of Fas-associated death domain protein (FADD) and DAP3 may preclude assembly of the death-inducing signaling complex. Seventy-two hours after CD40 ligation, sensitivity to CD95 and a progressive increase in FADD and DAP3 were associated with the acquired ability of FADD and FLIP to coimmunoprecipitate with the death-inducing signaling complex after CD95 ligation. Collectively, these studies reveal that CD40 ligation on CLL B cells induces a programmed series of events in which the cells initially are protected and then sensitized to CD95-mediated apoptosis through shifts in the balance of the anti- and proapoptotic proteins FLIP and FADD.

Induction of antitumor immunity via intratumoral tetra-costimulator protein transfer

Our group recently described a novel two-step Fc(gamma1) fusion protein transfer method, which entails the docking of Fc(gamma1) fusion proteins onto cells precoated with chemically palmitated protein A (pal-prot A). In the present study, we have adapted this protein transfer method, originally used in an ex vivo context, for in situ tumor cell engineering, and in so doing, we have evaluated its utility for the induction of antitumor immunity via combinatorial costimulator protein transfer on to tumor cell surfaces. The feasibility of "painting" cells with preformed conjugates of a murine B7-1 costimulator derivative, B7-1.Fc(gamma1), and pal-prot A in a single step was first established ex vivo. Next, B7-1.Fc(gamma1):pal-prot A transfer was accomplished in vivo by directly injecting the preformed conjugates into highly aggressive L5178Y-R lymphomas grown intradermally in syngeneic mice. The presence of cell surface-associated B7-1 epitopes on cells of the injected tumors was documented by flow cytometric analysis of cells recovered subsequently from the injected tumors. B7-1.Fc(gamma1), along with Fc(gamma1) fusion protein derivatives of three additional costimulators (Fc(gamma1).4-1BBL, CD48.Fc(gamma1), and Fc(gamma1).CD40L) geared toward a variety of immune effectors, were together preconjugated with pal-prot A and injected directly into tumor beds. Significantly, this "tetra-costimulator" combination, delivered intratumorally, induced complete tumor regression in approximately 45% of treated mice, whereas control injections of pal-prot A alone had no therapeutic effect. Furthermore, there was evidence for systemic antitumor immunity in that tumor-specific CTLs were detected in spleens recovered from cured mice, and these mice were uniformly protected against tumor rechallenge at distant tumor sites. Hence, combinatorial costimulator transfer, coupled to intratumoral delivery, may have special advantages for the induction of antitumor immunity.

A method for the production of cryopreserved aliquots of antigen-preloaded, mature dendritic cells ready for clinical use

Dendritic cells (DC) are increasingly used as a vaccine. Unfortunately, a satisfactory cryopreservation of DC in the absence of FCS is not yet available, so that laborious repeated generation of DC from fresh blood or frozen peripheral blood mononuclear cells for each vaccination has been required to date. We now aimed at developing an effective cryopreservation method, and by testing several variables found that it was crucial to combine the most advantageous maturation stimulus with an improved freezing procedure. We generated monocyte-derived DC from leukapheresis products by using GM-CSF and IL-4 and showed that amongst several known maturation stimuli the cocktail consisting of TNF-alpha+IL-1 beta+IL-6+PGE(2) achieved the highest survival of mature DC. We then systematically explored cryopreservation conditions, and found that freezing matured DC at 1 degrees C/min in pure autologous serum+10% DMSO+5% glucose at a cell density of 10x10(6) DC/ml gave the best results. Using this approach 85-100% of the frozen DC could be recovered in a viable state after thawing (Table 1). The morphology, phenotype, survival as well as functional properties (allogeneic mixed leukocyte reaction, induction of influenza matrix or melan A peptide-specific cytotoxic T cells) of these thawed DC were equivalent to freshly prepared ones. The addition of CD40L or TRANCE/RANKL further improved DC survival. Importantly, we demonstrate that DC can effectively be loaded with antigens (such as Tetanus Toxoid, influenza matrix and melan A peptides) before cryopreservation so that it is now possible to generate antigen-preloaded, frozen DC aliquots that after thawing can be used right away. This is an important advance as both the generation of a standardized DC vaccine under GMP conditions and the carrying out of clinical trials are greatly facilitated.