Long-term antigen-specific immune response by an oncolytic adenovirus encoding SP-SA-E7-4-1BBL in HPV-16 cancer model

BACKGROUND

To describe an oncolytic adenovirus (OAd) encoding SP-SA-E7-4-1BBL that is capable of inducing tumor regression in therapeutic assays. Herein, we tested whether the antitumor effect is given by the induction of a tumor-specific immune response, as well as the minimum dose needed to elicit antitumor protection and monitor the OAd biodistribution over time.

METHODS AND RESULTS

C57BL/6 mice (n = 5) per group were immunized twice with OAds encoding SP-SA-E7-4-1BBL, SA-E7-4-1BBL, or SP-SA-4-1BBL and challenged with TC-1 cancer cells. The DNA construct SP-SA-E7-4-1BBL was employed as a control via biolistic or PBS injection. Groups without tumor development at 47 days were rechallenged with TC-1 cells, and follow-up lasted until day 90. The minimum dose of OAd to induce the antitumor effect was established by immunization using serial dilution doses. The cytometry bead assay and the ELISpot assay were used to evaluate cytokine release in response to ex vivo antigenic stimulation. The distribution profile of the OAd vaccine was evaluated in the different organs by histological, immunohistochemical and qPCR analyses. The OAd SP-SA-E7-4-1BBL-immunized mice did not develop tumors even in a rechallenge. A protective antitumor effect was observed from a dose that is one hundredth of most reports of adenoviral vaccines. Immunization with OAd increases Interferon-gamma-producing cells in response to antigen stimulation. OAd was detected in tumors over time, with significant morphological changes, contrary to nontumor tissues.

CONCLUSIONS

The OAd SP-SA-E7-4-1BBL vaccine confers a prophylactic, safe, long-lasting, and antigen-dependent antitumor effect mediated by a Th1 antitumor immune response.

Engineered soluble, trimerized 4-1BBL variants as potent immunomodulatory agents

Targeting co-stimulatory receptors promotes the activation and effector functions of anti-tumor lymphocytes. 4-1BB (CD137/TNFSF9), a member of the tumor necrosis factor receptor superfamily (TNFR-SF), is a potent co-stimulatory receptor that plays a prominent role in augmenting effector functions of CD8+ T cells, but also CD4+ T cells and NK cells. Agonistic antibodies against 4-1BB have entered clinical trials and shown signs of therapeutic efficacy. Here, we have used a T cell reporter system to evaluate various formats of 4-1BBL regarding their capacity to functionally engage its receptor. We found that a secreted 4-1BBL ectodomain harboring a trimerization domain derived from human collagen (s4-1BBL-TriXVIII) is a strong inducer of 4-1BB co-stimulation. Similar to the 4-1BB agonistic antibody urelumab, s4-1BBL-TriXVIII is very potent in inducing CD8+ and CD4+ T cell proliferation. We provide first evidence that s4-1BBL-TriXVIII can be used as an effective immunomodulatory payload in therapeutic viral vectors. Oncolytic measles viruses encoding s4-1BBL-TriXVIII significantly reduced tumor burden in a CD34+ humanized mouse model, whereas measles viruses lacking s4-1BBL-TriXVIII were not effective. Natural soluble 4-1BB ligand harboring a trimerization domain might have utility in tumor therapy especially when delivered to tumor tissue as systemic administration might induce liver toxicity.

Adenovirus vaccine therapy with CD137L promotes CD8+ DCs-mediated multifunctional CD8+ T cell immunity and elicits potent anti-tumor activity

Renal carcinoma progresses aggressively in patients with metastatic disease while curative strategies are limited. Here, we constructed a recombinant non-replicating adenovirus (Ad) vaccine encoding an immune activator, CD137L, and a tumor antigen, CAIX, for treating renal carcinoma. In a subcutaneous tumor model, tumor growth was significantly suppressed in the Ad-CD137L/CAIX vaccine group compared with the single vaccine group. The induction and maturity of CD11C+ and CD8+CD11C+ dendritic cell (DC) subsets were promoted in Ad-CD137L/CAIX co-immunized mice. Furthermore, the Ad-CD137L/CAIX vaccine elicited stronger tumor-specific multifunctional CD8+ T cell immune responses as demonstrated by increased proliferation and cytolytic function of CD8+ T cells. Notably, depletion of CD8+ T cells greatly compromised the effective protection provided by Ad-CD137L/CAIX vaccine, suggesting an irreplaceable role of CD8+ T cells for the immunopotency of the vaccine. In both lung metastatic and orthotopic models, Ad-CD137L/CAIX vaccine treatment significantly decreased tumor metastasis and progression and increased the induction of tumor-specific multifunctional CD8+ T cells, in contrast to treatment with the Ad-CAIX vaccine alone. The Ad-CD137L/CAIX vaccine also augmented the tumor-specific multifunctional CD8+ T cell immune response in both orthotopic and metastatic models. These results indicated that Ad-CD137L/CAIX vaccine elicited a potent anti-tumor activity by inducing CD8+DC-mediated multifunctional CD8+ T cell immune responses. The potential strategy of CD137L-based vaccine might be served as a novel treatment for renal carcinoma or other malignant tumors.

Designed improvement to T-cell immunotherapy by multidimensional single cell profiling

BACKGROUND

Adoptive cell therapy based on the infusion of chimeric antigen receptor (CAR) T cells has shown remarkable efficacy for the treatment of hematologic malignancies. The primary mechanism of action of these infused T cells is the direct killing of tumor cells expressing the cognate antigen. However, understanding why only some T cells are capable of killing, and identifying mechanisms that can improve killing has remained elusive.

METHODS

To identify molecular and cellular mechanisms that can improve T-cell killing, we utilized integrated high-throughput single-cell functional profiling by microscopy, followed by robotic retrieval and transcriptional profiling.

RESULTS

With the aid of mathematical modeling we demonstrate that non-killer CAR T cells comprise a heterogeneous population that arise from failure in each of the discrete steps leading to the killing. Differential transcriptional single-cell profiling of killers and non-killers identified CD137 as an inducible costimulatory molecule upregulated on killer T cells. Our single-cell profiling results directly demonstrate that inducible CD137 is feature of killer (and serial killer) T cells and this marks a different subset compared with the CD107apos (degranulating) subset of CAR T cells. Ligation of the induced CD137 with CD137 ligand (CD137L) leads to younger CD19 CAR T cells with sustained killing and lower exhaustion. We genetically modified CAR T cells to co-express CD137L, in trans, and this lead to a profound improvement in anti-tumor efficacy in leukemia and refractory ovarian cancer models in mice.

CONCLUSIONS

Broadly, our results illustrate that while non-killer T cells are reflective of population heterogeneity, integrated single-cell profiling can enable identification of mechanisms that can enhance the function/proliferation of killer T cells leading to direct anti-tumor benefit.

An engineered 4-1BBL fusion protein with "activity on demand"

Engineered cytokines are gaining importance in cancer therapy, but these products are often limited by toxicity, especially at early time points after intravenous administration. 4-1BB is a member of the tumor necrosis factor receptor superfamily, which has been considered as a target for therapeutic strategies with agonistic antibodies or using its cognate cytokine ligand, 4-1BBL. Here we describe the engineering of an antibody fusion protein, termed F8-4-1BBL, that does not exhibit cytokine activity in solution but regains biological activity on antigen binding. F8-4-1BBL bound specifically to its cognate antigen, the alternatively spliced EDA domain of fibronectin, and selectively localized to tumors in vivo, as evidenced by quantitative biodistribution experiments. The product promoted a potent antitumor activity in various mouse models of cancer without apparent toxicity at the doses used. F8-4-1BBL represents a prototype for antibody-cytokine fusion proteins, which conditionally display "activity on demand" properties at the site of disease on antigen binding and reduce toxicity to normal tissues.

The CD137 Ligand Is Important for Type 1 Diabetes Development but Dispensable for the Homeostasis of Disease-Suppressive CD137+ FOXP3+ Regulatory CD4 T Cells

CD137 modulates type 1 diabetes (T1D) progression in NOD mice. We previously showed that CD137 expression in CD4 T cells inhibits T1D, but its expression in CD8 T cells promotes disease development by intrinsically enhancing the accumulation of β-cell-autoreactive CD8 T cells. CD137 is expressed on a subset of FOXP3+ regulatory CD4 T cells (Tregs), and CD137+ Tregs are the main source of soluble CD137. Soluble CD137 suppresses T cells in vitro by binding to the CD137 ligand (CD137L) upregulated on activated T cells. To further study how the opposing functions of CD137 are regulated, we successfully targeted Tnfsf9 (encoding CD137L) in NOD mice using the CRISPR/Cas9 system (designated NOD.Tnfsf9 -/-). Relative to wild-type NOD mice, T1D development in the NOD.Tnfsf9 -/- strain was significantly delayed, and mice developed less insulitis and had reduced frequencies of β-cell-autoreactive CD8 T cells. Bone marrow chimera experiments showed that CD137L-deficient hematopoietic cells were able to confer T1D resistance. Adoptive T cell transfer experiments showed that CD137L deficiency on myeloid APCs was associated with T1D suppression. Conversely, lack of CD137L on T cells enhanced their diabetogenic activity. Furthermore, neither CD137 nor CD137L was required for the development and homeostasis of FOXP3+ Tregs. However, CD137 was critical for the in vivo T1D-suppressive activity of FOXP3+ Tregs, suggesting that the interaction between CD137 and CD137L regulates their function. Collectively, our results provide new insights into the complex roles of CD137-CD137L interaction in T1D.

Editing of Genomic TNFSF9 by CRISPR-Cas9 Can Be Followed by Re-Editing of Its Transcript

The CRISPR-Cas system is a well-established RNA-guided DNA editing technique widely used to modify genomic DNA sequences. I used the CRISPR-Cas9 system to change the second and third nucleotides of the triplet TCT of human TNSFSF9 in HepG2 cells to TAG to create an amber stop codon. The TCT triplet is the codon for Ser at the 172nd position of TNSFSF9. The two substituted nucleotides, AG, were confirmed by DNA sequencing of the PCR product followed by PCR amplification of the genomic TNFSF9 gene. Interestingly, sequencing of the cDNA of transcripts of the edited TNFSF9 gene revealed that the TAG had been re-edited to the wild type triplet TCT, and 1 or 2 bases just before the triplet had been deleted. These observations indicate that CRISPR-Cas9-mediated editing of bases in target genomic DNA can be followed by spontaneous re-editing (correcting) of the bases during transcription.

Development of a flow cytometry assay which allows to evaluate the efficiency of immunomodulatory vaccines to enhance T cell-mediated antitumor response

Immunotherapy has revolutionized the treatment of cancer. Since tumor cells exhibit low immunogenicity and can induce several mechanisms of tolerance, the use of monoclonal antibodies or other immunomodulators, targeting costimulation of T cells may mediate the inhibition of immunosuppressive mechanisms, favouring immune surveillance and enhancing the detection and elimination of tumor cells. We developed a new in vitro assay, based on flow cytometry, which allows exploring the therapeutic potential of tumor-derived immunomodulatory lineages, enhancing anti-tumor response. We generated tumor-derived cells that simultaneously co-express eGFP and one immunomodulatory molecule (OX40L, 4-1BBL or GM-CSF). These genetically modified tumor-derived cells are irradiated and then incubated with primary T cells to evaluate the killing activity, which can be estimated by a decrease in the eGFP positive cells. The results have shown correlation with in vivo experiments. This model may contribute to the development of high-throughput assays for the screening of immunomodulators and a reduction in the use of experimental animals.

Crystal structure of murine 4-1BB and its interaction with 4-1BBL support a role for galectin-9 in 4-1BB signaling

4-1BB (CD137) is a TNF receptor superfamily (TNFRSF) member that is thought to undergo receptor trimerization upon binding to its trimeric TNF superfamily ligand (4-1BBL) to stimulate immune responses. 4-1BB also can bind to the tandem repeat-type lectin galectin-9 (Gal-9), and signaling through mouse (m)4-1BB is reduced in galectin-9 (Gal-9)-deficient mice, suggesting a pivotal role of Gal-9 in m4-1BB activation. Here, using sulfur-SAD phasing, we determined the crystal structure of m4-1BB to 2.2-Å resolution. We found that similar to other TNFRSFs, m4-1BB has four cysteine-rich domains (CRDs). However, the organization of CRD1 and the orientation of CRD3 and CRD4 with respect to CRD2 in the m4-1BB structure distinctly differed from those of other TNFRSFs. Moreover, we mapped two Asn residues within CRD4 that are N-linked glycosylated and mediate m4-1BB binding to Gal-9. Kinetics studies of m4-1BB disclosed a very tight nanomolar binding affinity to m4-1BBL with an unexpectedly strong avidity effect. Both N- and C-terminal domains of Gal-9 bound m4-1BB, but with lower affinity compared with m4-1BBL. Although the TNF homology domain (THD) of human (h)4-1BBL forms non-covalent trimers, we found that m4-1BBL formed a covalent dimer via 2 cysteines absent in h4-1BBL. As multimerization and clustering is a prerequisite for TNFR intracellular signaling, and as m4-1BBL can only recruit two m4-1BB monomers, we hypothesize that m4-1BBL and Gal-9 act together to aid aggregation of m4-1BB monomers to efficiently initiate m4-1BB signaling.

Use of Engineered Exosomes Expressing HLA and Costimulatory Molecules to Generate Antigen-specific CD8+ T Cells for Adoptive Cell Therapy

Dendritic cell-derived exosomes (DEX) comprise an efficient stimulator of T cells. However, the production of sufficient DEX remains a barrier to their broad applicability in immunotherapeutic approaches. In previous studies, genetically engineered K562 have been used to generate artificial antigen presenting cells (AAPC). Here, we isolated exosomes from K562 cells (referred to as CoEX-A2s) engineered to express human leukocyte antigen (HLA)-A2 and costimulatory molecules such as CD80, CD83, and 41BBL. CoEX-A2s were capable of stimulating antigen-specific CD8 T cells both directly and indirectly via CoEX-A2 cross-dressed cells. Notably, CoEX-A2s also generated similar levels of HCMV pp65-specific and MART1-specific CD8 T cells as DEX in vitro. The results suggest that these novel exosomes may provide a crucial reagent for generating antigen-specific CD8 T cells for adoptive cell therapies against viral infection and tumors.

OX40 and 4-1BB downregulate Kaposi’s sarcoma-associated herpesvirus replication in lymphatic endothelial cells, but 4-1BB and not OX40 inhibits viral replication in B-cells

Kaposi’s sarcoma-associated herpesvirus (KSHV) belongs to the human gammaherpesvirus subfamily and is associated with malignancies of endothelial origin (Kaposi’s sarcoma, KS) and B-cell origin [primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD)]. Viral lytic replication is known to be required for KS and MCD. As KSHV-related tumours mostly develop in human subjects when the immune system is compromised by immunosuppressive regimen, human immunodeficiency virus infection or some genetic deficiencies, KSHV-specific immune responses are believed to be important in the control of KSHV replication. However, analysis of the roles of immune cells in viral pathogenesis has been difficult due to the lack of an adequate animal model. Recently, congenital OX40 deficiency, as determined by genome-wide exome sequencing, was shown to be associated with aggressive childhood KS in a patient, suggesting that disrupted OX40–OX40L interactions might be implicated in disease development. Here, we report that interaction of recombinant OX40 protein with OX40L expressed on endothelial cells severely impaired KSHV lytic replication. Furthermore, 4-1BB–4-1BBL interactions were also capable of efficiently inhibiting viral replication in B-cells and endothelial cells. To the best of our knowledge, this is the first direct evidence that ligation of tumour necrosis factor superfamily members and their cognate receptors is important for the control of viral lytic replication. These data are likely to pave the way for the development of KSHV-specific therapies for KS and MCD, in which viral lytic replication is a disease-determining factor.

Expansion of NK Cells Using Genetically Engineered K562 Feeder Cells

Natural killer (NK) cells can be expanded upon activation by proliferative cytokines (such as IL-2 and IL-15). The NK cell expansion can be greatly enhanced by proteins from feeder cells such as tumor cell lines or PBMCs. Therefore, coculture systems of irradiated feeder cells and NK cells in media containing IL-2 and IL-15 have been developed to generate large numbers of NK cells, although NK cell expansion protocol using anti-CD3 antibody (OKT-3) without feeder cells has also been developed. Commonly used feeder cell lines are RPMI8866, Epstein-Barr lymphoblastoid cell line (EBV-LCL), and K562. Stimulation with NK-sensitive K562 cells is known to augment NK cell proliferation to IL-2, IL-15, and IL-21 in combination.Recently, remarkable NK cell-expansion rates are achieved when genetically engineered (GE) feeder cells are used. Dr. Dario Campana's group found that membrane-bound IL-15 and 4-1BBL, coexpressed by K562 cells, acted synergistically to augment K562-specific NK stimulatory capacity, resulting in vigorous expansion of peripheral blood CD56(+) CD3(-) NK cells without concomitant growth of T lymphocytes. Here, we describe an in vitro expansion method of human NK cells among PBMCs by coculturing with GE_K562 cells.

Fibroblast growth factor-21 is expressed in neonatal and pheochromocytoma-induced adult human brown adipose tissue

OBJECTIVE

In rodents, brown (BAT) and white (WAT) adipose tissues are targets and expression sites for fibroblast growth factor-21 (FGF21). In contrast, human WAT expresses negligible levels of FGF21. We examined FGF21 expression in human BAT samples, including the induced BAT found in adult patients with pheochromocytoma, and interscapular and visceral BAT from newborns.

METHODS

The expression of FGF21 and uncoupling protein-1 (UCP1, a brown adipocyte marker), was determined by quantitative real-time-PCR and immunoblotting. The transcript levels of marker genes for developmentally-programmed BAT (zinc-finger-protein of the cerebellum-1, ZIC1) and inducible-BAT (cluster of differentiation-137, CD137) were also determined.

RESULTS

FGF21 and UCP1 are significantly expressed in visceral adipose tissue from pheochromocytoma patients, but not in visceral fat from healthy individuals. In neonates, FGF21 and UCP1 are both expressed in visceral and interscapular fat, and their expression levels show a significant positive correlation. Marker gene expression profiles suggest that inducible BAT is present in visceral fat from pheochromocytoma patients and neonates, whereas developmentally-programmed BAT is present in neonatal interscapular fat.

CONCLUSIONS

Human BAT, but not WAT, expresses FGF21. The expression of FGF21 is especially high in inducible, also called beige/brite, neonatal BAT, but it is also found in the interscapular, developmentally-programmed, BAT of neonates.

HIV-1 adenoviral vector vaccines expressing multi-trimeric BAFF and 4-1BBL enhance T cell mediated anti-viral immunity

Adenoviral vectored vaccines have shown considerable promise but could be improved by molecular adjuvants. Ligands in the TNF superfamily (TNFSF) are potential adjuvants for adenoviral vector (Ad5) vaccines based on their central role in adaptive immunity. Many TNFSF ligands require aggregation beyond the trimeric state (multi-trimerization) for optimal biological function. Here we describe Ad5 vaccines for HIV-1 Gag antigen (Ad5-Gag) adjuvanted with the TNFSF ligands 4-1BBL, BAFF, GITRL and CD27L constructed as soluble multi-trimeric proteins via fusion to Surfactant Protein D (SP-D) as a multimerization scaffold. Mice were vaccinated with Ad5-Gag combined with Ad5 expressing one of the SP-D-TNFSF constructs or single-chain IL-12p70 as adjuvant. To evaluate vaccine-induced protection, mice were challenged with vaccinia virus expressing Gag (vaccinia-Gag) which is known to target the female genital tract, a major route of sexually acquired HIV-1 infection. In this system, SP-D-4-1BBL or SP-D-BAFF led to significantly reduced vaccinia-Gag replication when compared to Ad5-Gag alone. In contrast, IL-12p70, SP-D-CD27L and SP-D-GITRL were not protective. Histological examination following vaccinia-Gag challenge showed a dramatic lymphocytic infiltration into the uterus and ovaries of SP-D-4-1BBL and SP-D-BAFF-treated animals. By day 5 post challenge, proinflammatory cytokines in the tissue were reduced, consistent with the enhanced control over viral replication. Splenocytes had no specific immune markers that correlated with protection induced by SP-D-4-1BBL and SP-D-BAFF versus other groups. IL-12p70, despite lack of anti-viral efficacy, increased the total numbers of splenic dextramer positive CD8+ T cells, effector memory T cells, and effector Gag-specific CD8+ T cells, suggesting that these markers are poor predictors of anti-viral immunity in this model. In conclusion, soluble multi-trimeric 4-1BBL and BAFF adjuvants led to strong protection from vaccinia-Gag challenge, but the protection was independent of standard immune markers. Soluble multi-trimeric SP-D-4-1BBL and SP-D-BAFF provide a novel technology to enhance adenoviral vector vaccines against HIV-1.

Evaluating combinations of costimulatory antibody-ligand fusion proteins for targeted cancer immunotherapy

Combinatory strategies are becoming of increasing interest in cancer immunotherapy. Costimulation by individual members of the immunoglobulin-like (Ig)- and TNF superfamily have already shown promising antitumor potential, thus prompting the exploration of their synergistic abilities in combinatorial approaches. Here, we pursued a targeted strategy with antibody-fusion proteins composed of a tumor-directed antibody and the extracellular domain of the costimulatory ligand B7.1, 4-1BBL, OX40L, GITRL or LIGHT, respectively. Costimulatory activity was assessed in an experimental setting where initial T cell activation was induced by a bispecific antibody (tumor-related antigen × CD3). Advantage of combined targeted costimulation was shown for either B7.1 or 4-1BBL with OX40L, GITRL, LIGHT and 4-1BBL in terms of T cell proliferation and IFN-γ release. Since encouraging results were obtained by the combination of B7.1 and 4-1BBL, we adapted the model system for a time-shift setting. Here, enhanced proliferation and granzyme B expression as well as reduced PD-1 expression on the T cell population demonstrated the benefit of costimulation-assisted restimulation. Finally, the antitumor potential of this combinatorial setting was confirmed in vivo in a lung metastasis mouse model. Thus, combinatorial approaches with costimulatory antibody-ligand fusion proteins seem a promising strategy to be further investigated for cancer immunotherapy.

Long-term proliferation of functional human NK cells, with conversion of CD56(dim) NK cells to a CD56 (bright) phenotype, induced by carcinoma cells co-expressing 4-1BBL and IL-12

4-1BB ligation co-stimulates T cell activation, and agonistic antibodies have entered clinical trials. Natural killer (NK) cells also express 4-1BB following activation and are implicated in the anti-tumour efficacy of 4-1BB stimulation in mice; however, the response of human NK cells to 4-1BB stimulation is not clearly defined. Stimulation of non-adherent PBMC with OVCAR-3 cells expressing 4-1BB ligand (4-1BBL) or IL-12 resulted in preferential expansion of the NK cell population, while the combination 4-1BBL + IL-12 was superior for the activation and proliferation of functional NK cells from healthy donors and patients with renal cell or ovarian carcinoma, supporting long-term (21 day) NK cell proliferation. The expanded NK cells are predominantly CD56(bright), and we show that isolated CD56(dim)CD16(+) NK cells can switch to a CD56(bright)CD16(-) phenotype and proliferate in response to 4-1BBL + IL-12. Whereas 4-1BB upregulation on NK cells in response to 4-1BBL required 'help' from other PBMC, it could be induced on isolated NK cells by IL-12, but only in the presence of target (OVCAR-3) cells. Following primary stimulation with OVCAR-3 cells expressing 4-1BBL + IL-12 and subsequent resting until day 21, NK cells remained predominantly CD56(bright) and retained both high cytotoxic capability against K562 targets and enhanced ability to produce IFNγ relative to NK cells in PBMC. These data support the concept that NK cells could contribute to anti-tumour activity of 4-1BB agonists in humans and suggest that combining 4-1BB-stimulation with IL-12 could be beneficial for ex vivo or in vivo expansion and activation of NK cells for cancer immunotherapy.

[Prostate cancer cell vaccine transfected with 4-1BBL induces anti-tumor immunity in vitro]

OBJECTIVE

To explore the anti-tumor immunity in vitro induced by prostate cancer cell vaccine transfected with recombinant adenovirus encoding 4-1BBL in mice.

METHODS

The replication-deficient adenovirus AdEasy-1 system was used to construct recombinant adenovirus Ad-m4-1BBL and Ad-eGFP. The prostate cancer cell RM-1 of mice was transfected with Ad-m4-1BBL and Ad-eGFP, and treated with mitomycin (MMC) to produce TCV, TCV-Ad-eGFP and TCV-Ad-m4-1BBL, followed by co-culture with syngeneic murine spleen cells. Then the cytotoxic activity of the lymphocytes against RM-1 cells was analyzed with CCK-8 solution, and IL-2 and INF-gamma were detected by ELISA.

RESULTS

The 4-1BBL protein was highly expressed in the TCV-Ad-m4-1BBL of the 4-1BBL-transfected mice. TCV-Ad-m4-1BBL significantly increased the expressions of IL-2 ([180.24 +/- 2.22] pg/ml) and INF-gamma ([1512.46 +/- 23.64] pg/ml) as compared with TCV and TCV-Ad-eGFP (P < 0.05), and induced higher RM-1 cell specific cytotoxicity ([34.24 +/- 2.64]%) than the latter two ([9.82 +/- 1.48]%) and ([14.65 +/- 3. 21]%), (P < 0.05). But none of them exhibited significant cytotoxicity against hepatocellular carcinoma Hepal-6.

CONCLUSION

The m4-1BBL-expressing prostate cancer cell vaccine can effectively induce anti-tumor immune responses.

The change of immunoactivity of dendritic cells induced by mouse 4-1BBL recombinant adenovirus

PURPOSE

The purpose of this study is to construct a recombinant adenovirus vector carrying mouse 4-1BBL and observe its effects in dendritic cells.

MATERIALS AND METHODS

Mouse 4-1BBL cDNA was taken from the plasmid pcDNA3-m4- 1BBL and subcloned into adenovirus shuttle plasmid pAdTrack-CMV, and then transformed into competent BJ5183 with plasmid pAdEasy-1. After recombination in E.coli, Ad-4-1BBL was packaged and amplified in HEK 293 cells. The expression of 4-1BBL in Ad-4-1BBL-transfected mouse prostate cancer cell line RM-1 was detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. After the co-culture of dendritic cells (DCs) with Ad-4-1BBL-transfected RM-1 cells, interleukin (IL)-6 and IL-12 production were assessed by enzyme-linked immunosorbent assay (ELISA) and co-stimulatary molecules (CD80 and CD86) on DCs were analyzed by flow cytometry.

RESULTS

The levels of IL-6 (3,960 pg/mL) and IL-12 (249 pg/mL) production in Ad-m4-1BBL-pulsed DCs were more than those in none-pulsed DCs. The differences were statistically significant (p < 0.05). The expression of co-stimulatary molecules (CD80 and CD86) was up-regulated in Ad-m4-1BBL-pulsed DCs.

CONCLUSION

The results indicated the recombinant mouse 4-1BBL can effectively activate DCs.

Triple expression of B7-1, B7-2 and 4-1BBL enhanced antitumor immune response against mouse H22 hepatocellular carcinoma

OBJECTIVES

Costimulatory signals are essential for T-cell activation and hence play a very important role in antitumor immunity. B7 and 4-1BBL which belongs to tumor necrosis factor (TNF) family provide costimulatory interaction for T-cell activation and function. This study investigated the role of B7 and 4-1BBL in the amplification of tumor immunity by transduction of the B7-1, B7-2 and 4-1BBL into mouse hepatocellular carcinoma cell line H22.

METHODS

The tumorigenicity of H22 variants expressing either B7-1, B7-2 (H22/B7-1/B7-2) or 4-1BBL was compared with an H22 variant expressing B7-1, B7-2 and 4-1BBL (H22/B7-1/B7-2/4-1BBL). The study next investigated whether the combination of B7-1/B7-2 and 4-1BBL cell injection induced cytotoxic T lymphocyte (CTL) response and IL-2/IFN-γ secretion. The immune mechanisms underlying this combination treatment were then analyzed.

RESULTS

Syngeneic BALB/c mice injected with H22/B7-1/B7-2/4-1BBL cells that expressed elevated levels of B7-1, B7-2 and 4-1BBL showed a tumor development frequency of 50% compared with 100% in mice injected with the H22 parental line, H22/neo, H22/B7-1/B7-2 and H22/4-1BBL. Mice inoculated with H22 tumor cells expressing B7-1, B7-2 and 4-1BBL developed a strong cytotoxic T lymphocyte response and long-term immunity against wild-type tumor, suggesting a synergistic effect between the B7 and 4-1BBL costimulatory pathways. Results showed that H22/B7-1/B7-2/4-1BBL tumor vaccines probably protect the infiltrating lymphocytes from apoptosis and induce NF-κB activation to improve T-cell-mediated antitumor response.

CONCLUSIONS

In this study, the antitumor consequences of using B7-1, B7-2 and 4-1BBL gene transfer have demonstrated the therapeutic potential of gene therapy approach for hepatocellular carcinoma.

[Immunological killing effect of recombicant adenovirus vector rAD-mTERT-m4-1BBL on mouse hepatoma cell line Hepa1-6 cells co-cultured with T lymphocytes]

OBJECTIVE

To study the immunological suppressing effect of recombinant adenovirus vector rAD-mTERT promotor-m4-1BBL (rAD-mTERT) on mouse hepatoma cell line Hepa1-6 cells in co-culture with T lymphocytes.

METHODS

Adding recombinant adenovirus rAD, rAD-CMV-m4-1BBL (rAD-CMV) and rAD-mTERT to Hepa1-6 and L929 cells, respectively, to observe the effect of these adenoviruses on growth and apoptosis of these cells in co-culture with T lymphocytes.

RESULTS

Adding adenovirus significantly suppressed the growth and slightly increased apoptosis of the two types of cells (P < 0.05). rAD-mTERT promotor-m4-1BBL showed only pro-apoptotic effect on Hepa1-6 cells. When co-cultured with T lymphocytes, rAD-CMV-m4-1BBL showed promoting effect on apoptosis of the cells. Compared with that of T cells pre-co-culture, CD4(+) and CD8(+) T cells were proliferated, and the ratio of CD4/CD8 was significantly reduced (from 1.27 to 1.08).

CONCLUSION

Adding the recombinant adenoviruses only suppresses the cell growth, but not promotes their apoptosis. In co-culture with T lymphocytes, recombinant adenovirus vector rAD-mTERT promotor-m4-1BBL can targetingly suppress the growth and induce apoptosis of Hepa1-6 cells. The apoptosis is induced through the immunological killing effect of T lymphocytes.

[Transgenic 4-1-BB ligand therapy induces tumor specific immune response in oral squamous cell carcinoma]

OBJECTIVE

To examine the activation and cytotoxicity of human peripheral blood T lymphocyte induced in vitro by human 4-1-BB ligand (4-1-BBL) gene transfected into tumor Tca8113 cells.

METHODS

The eukaryotic expression vector pEGFP-h4-1-BBL was transfected into human oral carcinoma cell line Tca8113 by Lipofectamine 2000. The transfected cells were then selected in medium containing G-418, cloned by limited dilution and named as Tca8113-4-1-BBL. Human 4-1-BBL mRNA and protein expression of transfected cells was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting respectively. The tumor cell vaccines (TCV) were obtained by treatment with mitomycin (MMC). Human peripheral blood mononuclear cells (PBMC) were prepared from lymphoprep, and then stimulated with anti-CD-3 mAb and incubated with non-transfected or transfected TCV-Tca8113 cells, respectively. The proliferation of T cells was evaluated by trypan blue exclusion; the CCK-8 was used to detect the cytotoxic effect of T lymphocytes. Meanwhile, the secretion of interferon-gamma (IFN-gamma) and interleukin (IL)-2 in culture supernatant was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The Tca8113 cells transfected by pEGFP-h4-1-BBL could express human 4-1-BBL efficiently. As compared with wild type Tca8113 cells, the transfected Tca8113 cells could markedly promote proliferation, IL-2 and IFN-gamma production and cytotoxic activity of lymphocytes.

CONCLUSIONS

The transfection of human 4-1-BBL gene in Tca8113 cells is effective in enhancing its immunogenicity and inducing antitumor immune response in vitro.

[Expansion of human natural killer cells ex vivo]

AIM

To obtain sufficient numbers of pure and activated human primary NK cells for potential clinical application.

METHODS

PBMC based ex vivo expansion of natural killer cells was set up. The expansion was initiated by co-culture of PBMC and stimulator cells (irradiate genetic modified K562 cells) in RPMI1640 medium with 1 000 U/mL IL-2. Genetic modified K562 cells 'K562D3' were prepared by expressing IL-15, 4-1BBL and IL-18 on K562 cell membrane.

RESULTS

An average of 500 fold expansion of CD56(+)CD3(-) cells was observed after 3 weeks of co-culture. The NK cells population could reach 93% after expansion, comparing with 7% before expansion. The expanded NK cells lysed 95% of K562 targets in a 5:1 effector to target ratio. IL-15/4-1BBL bound K562 stimulatory cells could expand same fold NK cells as K562D3, but the cytotoxicity of NK cells expanded by 'K562D3' was 10% higher.

CONCLUSION

The described method is a simple and efficient way for the expansion of human NK cells.

Preferential T cell expansion by artificial antigen presenting cells expressing 4-1BBL alone or in combination with CD80 or CD86

BACKGROUND

Varieties of artificial antigen presenting cells (aAPCs) with different efficiencies have been introduced to expand whole T cell population or antigen specific ones for the purpose of T cell therapy. From antibody coated beads to gene modified dendritic cells each has some advantages and disadvantages. However, no one can ignore the importance and the necessity of costimulation interaction during T cell activation.

OBJECTIVE

This study was designed to compare the effectiveness of CD80/CD86 and 4-1BBL, two major costimulatory families, in costimulation of autologous T cell responses.

METHODS

We used recombinant non-replicative adenoviral vectors and transferred genes of these ligands to autologous blood monocytes and skin fibroblasts to create aAPCs system. T cell response to anti-CD3 pan stimulation and some viral peptide Ags, in co-culture with gene modified monocytes and fibroblasts were studied using CFSE and HLA tetramers, respectively.

RESULTS

Over-expression of ligands was able to expand the T cell population significantly higher than normal cells with no interference with antigen stimulation. Presence of 4-1BBL alone or in combination with B7 members enhanced T cell expansion and promoted more Ag-specific cells to accumulate in these culture systems.

CONCLUSION

Considering the inhibitory proportion of B7 costimulation route, 4-1BBL, as an alternative signaling pathway, in combination with B7 will promote T cell proliferation and expansion.

[The change of immunoactivity of dendritic cells induced by recombinant rat 4-1BBL]

AIM

To investigate the change of immunoactivity and surface marker of dendritic cells (DCs) derived from bone marrow and induced by rat 4-1BBL.

METHODS

Plasmid pIRES2-EGFP-4-1BBL was constructed and tansfected into HepG2 cells by lipofectin-mediated method, and positive cells were screened by G418. The expression of 4-1BBL in cells were detected by RT-PCR, and the expression of EGFP was detected by fluorescence microscopy. Various HepG2 cells were co-cultured with DC for 2 days, and then the expression of MHC-II and CD80 on DC were detected by FCM, and IL-6 and IL-12 levels secreted by DCs were tested by ELISA.

RESULTS

The recombinant pIRES2-EGFP-4-1BBL vector was successfully constructed and was steadily expressed in HepG2 cells transfected by pIRES2-EGFP-4-1BBL. Compared with HepG2 cells transfected by pIRES2-EGFP plasmid , recombinant HepG2 cells induced high expression of MHC-II and CD80 and secreted more IL-6 and IL-12 on DCs(P<0.05).

CONCLUSION

The recombinant rat 4-1BBL could promote the maturity of DCs derived from bone marrow.

[Construction and expression of human 4-1BBL/anti-CD20 fusion protein]

AIM

To construct and express human 4-1BBL/anti-CD20 bispecific fusion protein and identify its biological activity.

METHODS

PCR and overlapping PCR were used to construct human 4-1BBL/anti-CD20 bispecific fusion protein. DNA sequencing was performed by the terminus of the fusion protein nucleotide.The product was purified by affinity chromatography and analyzed by Western blot and its antigen-binding activity was examined by FACS.

RESULTS

The data of DNA sequence showed that human 4-1BBL/anti-CD20 bispecific fusion protein was correct. The fusion protein was recovered in high yield (up to 4 mg/L) after E-tag purification and predominantly(90%) as a dimer. The fusion protein could bind to Raji cells(CD20(+)) and A549 cells(4-1BB(+)), respectively.

CONCLUSION

The human 4-1BBL/anti-CD20 bispecific fusion protein with high level expression was successfully obtained and could bind to Raji ceIls and A549 cells.

Extracellular domain of 4-1BBL enhanced the antitumoral efficacy of peripheral blood lymphocytes mediated by anti-CD3 x anti-Pgp bispecific diabody against human multidrug-resistant leukemia

Our previous data have shown a significantly higher tumor response to anti-CD3/anti-Pgp bispecific diabody-mediated immunotherapy for P-glycoprotein (Pgp)-overexpressing K562/A02 cells, but a rapid tumor relapse occurred at 1 week after therapy. In an attempt to overcome tumor recurrence, we supplemented the previous therapy with extracellular domain of human 4-1BBL (ex4-1BBL) to regulate the activation of peripheral blood lymphocyte (PBL). As a result, this combination showed enhanced cytotoxicity in vitro and eradicated the multidrug-resistant xenografts of K562/A02 in nude mice. Furthermore, no tumor recurrence was observed within 100 days after the first treatment. Therefore, when used as an adjuvant, ex4-1BBL may improve the outcome of PBL-based immunotherapy.

Prevention of lethal tumor growth and generation of long-lasting immunity in vivo using CD137L and interleukin-12 gene transfer

In a wide range of solid tumors, overexpression of CD137L has been shown to induce tumor immunity partly due to the stimulation of CD8+ CTL, which was even increased when immunotherapy with interleukin-12 (IL12) was additionally employed. However, little in known regarding hematologic neoplasias in this respect. Of the 8 animals receiving IL12-secreting tumor cells, 2 died. Animals treated with CD137L-expressing tumor cells and the combination group, all animals survived. Interestingly, re-challenge with wild-type tumor cells was rejected by all animals in the CD137L group and all remaining animals in the IL12 group, while these in the control group died. IL12- and CD137L-transfected plasmocytoma cells prevented tumor growth and induced long-lasting immunity. Our results warrant follow-up for future clinical use in patients with myeloma.

[Study on the construction and expression of the human 4-1BBL extracellular domain/anti-CD20 Fab' fusion protein]

Several studies have demonstrated the role of 4-1BBL in T cell activation. Furthermore, enhanced 4-1BB/4-1BBL interaction has been shown to amplify T-cell-mediated antitumor immunity in several mouse models. However, when applied in humans, it was difficult to generate sufficient T cells ex vivo and whole cell vaccines to transfer back into patients. To overcome this difficulty, we have focused on producing the human 4-1BBL extracellular domain/anti-CD20 Fab' fusion protein. In this report, PCR and overlap PCR were used to construct the human 4-1BBL extracellular domain/anti-CD20 Fab' expression vector. DNA sequence was analyzed by the Terminus of Dideoxy Nucleotide. The product was purified by affinity chromatography and analyzed by SDS-PAGE and HPLC; its antigen binding activity was examined by rosetting assay. The data of DNA sequence showed that the human 4-1BBL extracellular domain/anti-CD20 Fab' fusion protein was corrected. The fusion protein was recovered in high yield (up to 200 microg/mL) after E-taq purification. The fusion protein was capable of simultaneous binding to stimulated Jurkat cells and Raji cells as shown by cellular rosetting. In conclusion, the human 4-1BBL extracellular domain/anti-CD20 Fab' fusion protein was induced to express in E. coli 16C9. The results of some biological activity experiments indicated that the fusion protein could bind to stimulated Jurkat cells and Raji cells. Furthermore, 4-1BBL-negative tumors can be converted into 4-1BBL-positive tumors by the fusion protein without the need for 4-1BBL gene transfer to the malignant cells.

B7-1 and 4-1BB ligand expression on a myeloma cell line makes it possible to expand autologous tumor-specific cytotoxic T cells in vitro

OBJECTIVE

The aim of this study was to confer an antigen-presenting cell (APC) ability on multiple myeloma cell lines (HMCLs) using B7-1 and/or 4-1BBL gene transfer.

MATERIALS AND METHODS

HMCLs were retrovirally transduced with B7-1 and/or 4-1BBL cDNAs. Allogeneic or autologous T cells were stimulated by coculture with B7-1- and/or 4-1BBL-transduced HMCLs in the presence of interleukin-2. T cell clones were obtained by limiting dilution. T-cell activation was assessed by interferon-gamma Elispot assays and cytotoxicity by (51)Cr release assays.

RESULTS

Neither primary multiple myeloma cells (MMCs) nor HMCLs expressed B7-1 or 4-1BBL, and these molecules could not be induced by CD40 triggering. HMCLs failed to stimulate allogeneic or autologous T cells. Transduction of HMCLs with B7-1 and/or 4-1BBL retroviruses induced a high expression of B7-1 and 4-1BBL molecules and a strong T-cell activation ability. Long-term cultured CD8(+) T-cell lines could be obtained by stimulation with the autologous B7-1/4-1BBL XG-19 HMCL. These cytotoxic T lymphocytes (CTL) efficiently killed the autologous parental XG-19 HMCL as well as autologous primary MMCs and allogeneic HMCLs. They did not kill autologous CD34 cells and autologous EBV cell line or natural killer target K562 cells. Cloned CTL could recognize allogeneic HMCLs, demonstrating that a shared anti-MMC repertoire was expanded.

CONCLUSION

Transduction with B7-1 and 4-1BBL retroviruses turned HMCLs into efficient APCs. It permitted the long-term expansion of autologous anti-tumor CTL with a shared anti-MMC repertoire, for one HMCL. These data suggest developing an immunotherapy using modified tumor cells in patients with multiple myeloma.

Growth inhibitory and apoptosis inducing effect of Perilla frutescens extract on human hepatoma HepG2 cells

Perilla frutescens (L.) Britt. (Lamiaceae) has traditionally been used to treat diseases, including tumors, but the antitumorigenesis mechanism is unclear. We evaluated the effects of Perilla frutescens leaf extract (PLE) on proliferation and apoptosis inducing in human hepatoma HepG2 cells using a cell proliferation assay, flow cytometry, and cDNA microarrays. Gene expression and apoptosis were also assessed in HepG2 cells treated with a major constituent of PLE, rosmarinic acid (RosA). In the PLE-treated HepG2 cells, antiproliferative activity (105 microg/mL) were observed, flow cytometry revealed significant apoptosis, and microarray data indicated that the expression of a lot apoptosis-related genes were regulated in a time-dependent manner. Compared with PLE, RosA (10 microg/mL; a dose equivalent to 105 microg/mL of PLE) was less effective in increasing the expression of apoptosis-related genes and apoptosis inducing in HepG2 cells. Thus, additional PLE constituents may influence apoptosis in HepG2 cells. The results of our study suggest that the PLE should be further investigated as a promising to treat hepatocellular carcinoma.

Co-immunisation with DNA encoding RANK/RANKL or 4-1BBL costimulatory molecules does not enhance effector or memory CTL responses afforded by immunisation with a tumour antigen-encoding DNA vaccine

T cell mediated immune responses are induced following interaction of MHC-presented epitope on professional antigen presenting cells such as dendritic cells (DCs) with cognate T cell receptor. Up-regulation of receptor-ligand pairs of costimulatory molecules linking DC to T cell enhances the resulting T cell responses. This 'second signalling' occurs through the B7 molecules CD80/86 expressed by DCs, and importantly through members of the TNF ligand/TNF receptor superfamilies. We have previously shown that co-expression of RANK/RANKL or 41BB-L in addition to tumour antigen in dendritic cells augmented cognate effector and memory tumour antigen-directed cytotoxic T cell responses when the DCs were used to immunise mice. Here, we examined whether co-immunisation with naked plasmid DNAs encoding antigen and these costimulatory molecule(s), would enhance antigen specific T cell responses. We demonstrate that co-immunisation with DNAs encoding tumour antigen and costimulatory molecules failed to enhance antigen-directed CTL responses, or tumour protection, afforded by immunisation with DNA encoding tumour antigen alone.

Distinct approaches to investigate the importance of the murine 4-1BB-4-1BBL interaction in the antibody response to Streptococcus pneumoniae

Protection against infection with Streptococcus pneumoniae is based mainly on the generation of antibodies to the pneumococcal capsular polysaccharides (caps-PS). Although caps-PS are considered thymus-independent antigens, there is a growing body of evidence that T lymphocytes and costimulatory molecules are involved in the regulation of the antibody response to caps-PS. We investigated whether the interaction between 4-1BB and 4-1BB ligand (4-1BBL) is involved in the modulation of the antibody response to caps-PS after immunization with Pneumovax or with intact heat-killed S. pneumoniae. Treatment with agonistic anti-4-1BB mAb, which mimics engagement of 4-1BB by 4-1BBL, had no effect on the IgG and IgM immune response to caps-PS (Serotype 3) after immunization with Pneumovax or with S. pneumoniae Serotype 3. However, anti-4-1BB treatment strongly inhibited the IgG response to pneumococcal surface protein A (PspA). By contrast, the IgG anti-caps-PS (Serotype 3) antibody response was reduced strongly in 4-1BBL(-/-) mice immunized with S. pneumoniae Serotype 3. The IgG anti-PspA antibody response in the 4-1BB(-/-) mice was comparable with the immune response in the wild-type mice. We conclude that distinct pathways are involved in the humoral antibody response to pneumococcal antigens, depending on the nature of the antigen and the context in which the different antigens are presented. The 4-1BB-4-1BBL interaction is not involved in the antibody response to soluble caps-PS. The influence of the 4-1BB-4-1BBL interaction in the immune reaction to S. pneumoniae Serotype 3 depends on the experimental system used.

[Construction and expression of eukaryotic expression vector of human 4-1BB ligand gene in tumor cells and its antitumor activity in vitro]

AIM

To construct eukaryotic expression vector of human 4-1BB ligand (4-1BBL) gene and express it in HT-29 cell line. To explore the effect on activation and cytotoxicity of human cytotoxic T lymphocytes(CTLs) induced by human 4-1BBL gene transfection into tumor cells in vitro.

METHODS

RT-PCR was applied to amplify the full-length of human 4-1BBL gene from Raji cells. After sequencing, the cDNA was recombinated into the eukaryotic expression vector pcDNA3.1(-) and transfected into HT-29 cells through Lipofect AMINE 2000. Human 4-1BBL mRNA and protein expression of transfected cells was detected by RT-PCR and FACS respectively. Human peripheral blood mononuclear cells were stimulated with anti-CD3 mAb and incubated with non-transfected or transfected HT-29 cells, respectively. The MTT colorimetry was used to detect the proliferation and cytotoxic effect of T lymphocytes. Meanwhile, the expression of intracellular IFN-gamma was detected by FCM.

RESULTS

The HT-29 cells transfected by pcDNA3.1(-)-h4-1BBL could express human 4-1BBL efficiently. As compared with wild type HT-29 cells, the transfected HT-29 cells had more effect for proliferation, IFN-gamma production and cytotoxic activity of lymphocytes.

CONCLUSION

The recombinant eukaryotic expression vector of pcDNA3.1(-)-h4-1BBL is successfully constructed. The transfection of human 4-1BBL gene in HT-29 cells is effctive in enhancing its immunogenicity and inducing antitumor immune response in vitro.

Enhanced protective efficacy and reduced viral load of foot-and-mouth disease DNA vaccine with co-stimulatory molecules as the molecular adjuvants

To improve efficacy of DNA vaccination, various approaches have been developed, including the use of plasmid expressing co-stimulatory molecules as molecular adjuvants. In this study, we investigated whether co-inoculation of a construct expressing either 4-1BBL or OX40L as the molecular adjuvant with FMDV DNA vaccine, pcD-VP1, can increase immune responses and protective efficacies. Compared to the group immunized with pcD-VP1 alone, the co-inoculation of either molecular adjuvant induced a higher ratio of IgG2a/IgG1, higher levels of expression of IFN-gamma in CD4(+) and CD8(+) T cells and antigen-specific CTL responses, and more importantly provided an enhanced protection against the live FMDV challenge in animals. Concurrently, 4-1BBL as the molecular adjuvant dramatically reduced the viral loads of FMDV in vivo after the challenge. Together, the results demonstrate that co-stimulatory molecules 4-1BBL and OX40L can enhance the antigen-specific cell-mediated responses elicited by VP1 DNA vaccine and provide an enhanced protective efficacy with the reduced viral loads.

Cell surface 4-1BBL mediates sequential signaling pathways 'downstream' of TLR and is required for sustained TNF production in macrophages

The stimulation of Toll-like receptors (TLRs) on macrophages triggers production of the cytokine tumor necrosis factor (TNF). TNF production occurs within 1 h of TLR stimulation and is sustained for 1 d. Here we document a function for the TNF family member 4-1BB ligand (4-1BBL) in sustaining TLR-induced TNF production. TLR signaling induced 4-1BBL, and 4-1BBL interacted with TLRs on the macrophage surface. The influence of 4-1BBL on TNF production was independent of its receptor (4-1BB) and did not require the adaptors MyD88 or TRIF. It did not influence TLR4-induced activation of transcription factor NF-kappaB (an early response) but was required for TLR4-induced activation of transcription factors CREB and C/EBP (a late event). Transient TLR4-MyD88 complexes appeared during the first hour after lipopolysaccharide stimulation, and TLR4-4-1BBL interactions were detected between 2 h and 8 h after lipopolysaccharide stimulation. Our results indicate that two different TLR4 complexes sequentially form and selectively control early and late TNF production.

Targeted and untargeted CD137L fusion proteins for the immunotherapy of experimental solid tumors

INTRODUCTION

CD137L is a member of the tumor necrosis factor superfamily that provides a costimulatory signal to T cells. In this study, two novel CD137L fusion proteins were produced and compared with the CD137 agonist antibody 2A.

MATERIALS AND METHODS

Murine CD137L was linked to the COOH terminus of either the Fc fragment of immunoglobulin (untargeted version) or TNT-3 (targeted version), an antibody that binds to necrotic regions of tumors. Groups of mice bearing established Colon 26 tumors were then treated daily x 5 with each fusion protein or 2A to determine their immunotherapeutic potential.

RESULTS

Both fusion proteins retained CD137L activity in vitro and TNT-3/CD137L showed tumor-binding activity by biodistribution analysis in tumor-bearing mice. The fusion proteins also produced similar responses in vivo at the 1 nmol per dose range and showed a 60% (TNT-3/CD137L) or 40% (Fc/CD137L) survival of treated mice at 150 days after tumor implantation, similar to the effects of 2A. Morphologic and immunohistochemical analyses showed massive central necrosis and infiltration of granzyme B-positive cells in necrotic areas and viable peripheral regions of treated tumors. Finally, cell depletion studies showed that CD137L-mediated tumor regression was CD8(+) T cell dependent.

CONCLUSIONS

From these studies, it was determined that both targeted and untargeted CD137L fusion proteins showed effective antitumor activity, but that the targeted version was more potent. Therefore, the use of the natural CD137 ligand is a promising approach to the treatment of solid tumors by virtue of its ability to produce physiologic costimulation within the tumor, limiting side effects often seen with agonist antibody therapies.

The adjuvant effects of co-stimulatory molecules on cellular and memory responses to HBsAg DNA vaccination

Because DNA vaccines on their own tend to induce weak immune responses in humans, adjuvant methods are needed in order to improve their efficacy. The co-stimulatory molecules 4-1BBL, OX40L, and CD70 have been shown to induce strong T cell activities; therefore, in this study, we investigated whether they may be used as molecular adjuvants for a hepatitis B surface antigen (HBsAg) DNA vaccine (pcDS2) in eliciting strong cellular and memory responses. Compared to mice immunized with pcDS2 alone, addition of the co-stimulatory molecules increased T cell proliferation and an HBsAg-specific antibody response that was marked with a higher ratio of IgG2a/IgG1. Importantly, pcDS2 plus these co-stimulatory molecules elicited a higher level of IFN-gamma and IL-4 in CD4(+) T cells and a higher level of IFN-gamma in CD8(+) T cells. In addition, a significantly robust antigen-specific cytotoxic T lymphocyte (CTL) response and the production of long-term memory CD8(+) T cells were also observed in the groups immunized with pcDS2 plus 4-1BBL, OX40L, or CD70. Consistently, as late as 100 days after immunization, upregulated expressions of BCL-2, Spi2A, IL-7Ra, and IL-15Ra were still observed in mice immunized with pcDS2 plus these co-stimulatory molecules, suggesting the generation of memory T cells in these groups. Together, these results suggest that the co-stimulatory molecules 4-1BBL, OX40L, or CD70 can enhance the immunogenicity of HBsAg DNA vaccines, resulting in strong humoral, cellular, and memory responses. This approach may lead to an effective therapeutic vaccine for chronic hepatitis B virus (HBV) infection.

4-1BB (CD137) signals depend upon CD28 signals in alloimmune responses

Our previous study has demonstrated that there is a significant delay of Balb/c cardiac allograft rejection in the C57BL/6 4-1BB-deficient knockout recipient. In this study, we examined the effect of combined blockade of the 4-1BB and CD28 costimulatory pathways on cardiac allograft rejection in the C57BL/6-->Balb/c model. A long-term cardiac allograft survival was induced in CD28/4-1BB- deficient mice (>100 days survival in 3 of 4 mice), which was comparable with CD28-deficient mice (>100 days survival in 2 of 5 mice; P<0.2026). There was no long-term cardiac allograft survival in either wild-type (WT) or 4-1BB-deficient mice, even though 4-1BB-deficient recipients showed a significant delay of cardiac allograft rejection than WT mice. An in vitro mixed leukocyte reaction (MLR) assay showed that 4-1BB-deficient and WT mouse T cells had a similar responsiveness to allostimulation, whereas CD28- and CD28/4-1BB-deficient mouse T cells had a defective responsiveness to allostimulation. Furthermore, 4-1BB-deficient mice showed a similar CTL but an elevated Ab response against alloantigens as compared to WT mice, and the alloimmune responses of 4-1BB-deficient mice were abrogated in the CD28-deficient background. Overall, these results indicate that the CD28 costimulatory pathway plays a major role in the alloimmune response and that 4-1BB signals are dependent upon CD28 signals.

4-1BBL coexpression enhances HIV-specific CD8 T cell memory in a poxvirus prime-boost vaccine

We have constructed a recombinant fowlpox virus expressing HIV antigens and the costimulatory molecule 4-1BBL. When included in the boost, but not the prime of a poxvirus prime-boost strategy, 4-1BBL significantly enhanced the anti-HIV T cell response generated to this vaccination in BALB/c mice, as detected by ex vivo IFNgamma ELISPOT responses, intracellular cytokine staining to HIV Gag antigens, and enumeration of Gag-reactive CD8 T cells. 4-1BBL however, is not capable of modulating the CD4 T cell response, nor the antibody response to this vaccination strategy. Enhancement of the T cell response by 4-1BBL continues into the memory phase, as detected 2 months post vaccination. This data is the first to show modulation of the immune response to a viral vaccine by coexpression of 4-1BBL and supports this strategy as an exciting approach for enhancement of T cell memory in prime-boost vaccines.

[Impact of co-expression of CD80, CD86 and CD137L genes on tumor immunogenicity in HCC H22-BAL b/c mouse model]

OBJECTIVE

To understand the influence of co-expression of CD80, CD86 and CD137L genes on tumor immunogenicity in hepatocellular carcinoma H22-BAL B/c mouse models.

METHODS

The mice were randomly divided into five groups, named A, B, C, D and E, and control groups A and B, 20 mice in each group. Hepatocellular carcinoma H22-BAL B/c mouse model was established by subcutaneous injection of cells H22-Wt, H22-neo, H22-CD80/CD86+, H22-CD137L+ and H22-CD80/CD86/CD137L+, respectively. The rate and incubation period of tumor development, survival rate, and the tumor growth in vivo were observed and recorded. The effects of gene transduction on immunogenicity of the tumor and antitumor immunity of the animals were assessed by re-innoculation of wild type H22 cells.

RESULTS

The rate of tumor development in group E was only 50%, much lower than that in other four groups (P < 0. 01). The tumor growth in group C was reduced with complete tumor regression in two hosts (20%, 2/10). In group E, there was more pronounced reduction of tumor size. The maximal tumor sizes were remarkably smaller than those of group C, and there was complete tumor regression in three mice (60%, 3/5). No tumor regression was found in the other three groups. Survival rates of group C and E were significantly higher than that of animals in groups A, B and D (P < 0. 01), but no significant difference was seen between group C and E. The results of re-inoculation test showed that tumor formation rate was 40% (4/10) in group C, 100% (8/8) in group D, and 0 (0/5) in group E. There were significant differences between groups C and E and control group, between group E and C, but not between C and D. After the third time of re-inoculation with H22-Wt cells at the 56th day, tumor occurred in 6/6 mice (100%) of group C, but 0 (0/5) in group E. The difference was very significant. Five animals without tumor formation after the first inoculation in group E, were re-inoculated with H22-Wt cells on the 21st day and the third re-inoculation on the 56th day, no tumor was found (0/5).

CONCLUSION

Both co-expression and solo-expression of CD80+ CD86 and CD137L genes reduce the tumorigenicity of wild type H22 cells, but co-expression of CD80, CD86 and CD137L genes can more significantly improve the immunogenicity of H22-CD80/CD86/CD137L+ cells.

[Cloning and expression of the extracellular domain of 4-1BBL]

RT-PCR was used to clone DNA fragment of the extracellular domain of 4-1BBL from human THP-1 cells (human monocyte), and the expression vector pAYZ4-1BBL was constructed by cloning the extracellular domain of 4-1BBL into the expression vector pAYZ. The extracellular domain of 4-1BBL was expressed in E. coli 16C9 and purified by affinity chromatography. SDS-PAGE and Western blot analysis showed that the relativae molecular weight of soluble 4-1BBL is 22kD which was consistent with the theoretically predicted value. So far as we know, it is the first time that the soluble expression of 4-1BBL in E. coli was achieved 4-1BBL induced a significant release of IL-2 in stimulated Jurkat cells after 48h incubation, especially in the presence of tumor cell. At the same time the apoptosis level of Jurkat cell reduce more than 50%. In conclusion, 4-1BBL may be useful in cancer immunotherapy.

[Inhibitory effect of 4-1BBL combined with Hsp70-tumor antigen peptides on pulmonary metastasis of melanoma in mice]

BACKGROUND & OBJECTIVE

Low level expression of some co-stimulatory molecules is an important mechanism for tumor to evade the attack of immunity system; up-regulating these molecules can enhance antitumor immune response. Mouse melanoma B16-F1 cell line is low immunogenic. This study was designed to investigate the inhibitory effect of co-stimulatory molecule 4-1BBL combined with hot shock protein 70 (Hsp70)-tumor antigen peptides on pulmonary metastasis of melanoma in mice, and to analyze the possible mechanism.

METHODS

After establishment of B16-F1 melanoma pulmonary metastasis model, the mice were divided into combination (4-1BBL plus Hsp70-B16) group, 4-1BBL group, Hsp70-B16-F1 group, empty vector group, and normal saline(NS) group, and relevantly received subcutaneous immunization of Hsp70-B16 peptides complex and simultaneous injection of plasmid p4-1BBL via the tail vein. Seventeen days after inoculation of B16 cells, the mice were killed to count pulmonary metastasis nodes under microscope, and to detect a series of immunologic parameters, liver function, and kidney function.

RESULTS

The number of pulmonary metastasis nodes was significantly smaller in combination group than in 4-1BBL group and Hsp70-B16 group (50+/-8 vs. 500+/-80 and 450+/-40, P0.01); the levels of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) in serum were significantly higher in combination group than in NS group (200.31+/-25.36 vs. 56.89+/-16.55, P0.05; 1 870.53+/-204.28 vs. 610.30+/-120.05, P0.01). The liver and kidney functions of mice in each group are normal.

CONCLUSION

4-1BBL in combination with Hsp70-B16 peptides can effectively inhibit melanoma pulmonary metastasis mainly through augmenting the function of peripheral T lymphocytes.