Abstract 1730: A novel chimeric virus-like drug conjugate (VDC) for the potential treatment of HPV-positive tumors

Introduction: Human papillomavirus (HPV) virus-like particles (VLPs) bind to a wide variety of tumor types via modified glycosaminoglycans (GAGs) found on the tumor cell surface. This finding led to the development of the investigational virus-like drug conjugate (VDC) belzupacap sarotalocan (bel-sar, formerly AU-011), an HPV-derived VLP conjugated to a light-activated cytotoxic payload. When activated by near-infrared light, bel-sar induced rapid tumor necrosis resulting in pro-immunogenic cell death, release of tumor neoantigens and long-term anti-tumor immunity in the TC-1 tumor model. When E6 and E7 expressing TC-1 mouse tumors were treated with the VDC, E7-specific T-cells were detected in the absence of provided tumor antigens. A novel chimeric VDC (cVDC) is now in development, in which E6 and E7 are fused to the L2 capsid protein as a means to potentially further enhance the observed anti-tumor response. This cVDC could allow for the targeted cytotoxicity of HPV-positive tumors in addition to the release of supplemental tumor antigens E6 and E7 within the now pro-immunogenic tumor milieu, potentially leading to a long term anti-tumor response.

Methods: The detoxified sequences of E6 and E7 were engineered as one fusion polypeptide on the C-terminus of the L2 minor capsid protein. Both L2/E6/E7 and L2/E7/E6 protein expression vectors were generated to determine if the order of the proteins impacted L2’s ability to co-assemble with L1, the major capsid protein. The plasmids were co-expressed alongside L1 using the mammalian 293TT expression system.

Results: Both the L2/E6/E7 and L2/E7/E7 fusion proteins were expressed and co-assembled with L1 into chimeric VLPs. Fusion protein expression was validated by western blots for L2, E6 and E7, and VLPs were confirmed by electron microscopy.

Conclusions: Preliminary data indicate that chimeric VDCs containing E6 and E7 can successfully be generated using the 293TT mammalian expression system. Studies evaluating the cytotoxicity and E6 and E7 immunogenicity of the cVDC as well as the impact on tumor targeting are underway.

Citation Format: Rhonda C. Kines, Anneli Savinainen, Elisabet de los Pinos, John T. Schiller. A novel chimeric virus-like drug conjugate (VDC) for the potential treatment of HPV-positive tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1730.

Immune checkpoint inhibition combined with targeted therapy using a novel virus-like drug conjugate induces complete responses in a murine model of local and distant tumors

Metastases remain the leading cause of cancer-related death worldwide. Therefore, improving the treatment efficacy against such tumors is essential to enhance patient survival. AU-011 (belzupacap sarotalocan) is a new virus-like drug conjugate which is currently in clinical development for the treatment of small choroidal melanoma and high-risk indeterminate lesions in the eye. Upon light activation, AU-011 induces rapid necrotic cell death which is pro-inflammatory and pro-immunogenic, resulting in an anti-tumor immune response. As AU-011 is known to induce systemic anti-tumor immune responses, we investigated whether this combination therapy would also be effective against distant, untreated tumors, as a model for treating local and distant tumors by abscopal immune effects. We compared the efficacy of combining AU-011 with several different checkpoint blockade antibodies to identify optimal treatment regimens in an in vivo tumor model. We show that AU-011 induces immunogenic cell death through the release and exposure of damage-associated molecular patterns (DAMPs), resulting in the maturation of dendritic cells in vitro. Furthermore, we show that AU-011 accumulates in MC38 tumors over time and that ICI enhances the efficacy of AU-011 against established tumors in mice, resulting in complete responses for specific combinations in all treated animals bearing a single MC38 tumor. Finally, we show that AU-011 and anti-PD-L1/anti-LAG-3 antibody treatment was an optimal combination in an abscopal model, inducing complete responses in approximately 75% of animals. Our data show the feasibility of combining AU-011 with PD-L1 and LAG-3 antibodies for the treatment of primary and distant tumors.

A novel virus-like drug conjugate (VDC) in combination with immune checkpoint inhibitors for the treatment of primary tumors and distant metastasis

e14544

Background: Although there has been great progress in the early diagnosis of choroidal melanoma, metastases remain the leading cause of cancer-related death. Therefore, improving the treatment efficacy against metastases is essential to enhance patient survival. A new targeted therapy, the virus-like drug conjugate (VDC) AU-011 (belzupacap sarotalocan), is currently in clinical development to treat early-stage choroidal melanoma with an intra-ocular administration followed by near-infrared (NIR) light activation using a photodynamic therapy (PDT) laser. Murine experiments have shown that AU-011 enhances immune checkpoint inhibition (ICI) and protects against tumor rechallenge. Methods: We investigated whether this combination therapy had an effect not only on primary tumors but also on distant, untreated tumors, as a model for treating metastatic cancer by abscopal immune effects and compared the efficacy of combining AU-011 with several ICI antibodies. Results: In vitro, AU-011 treatment induced a preferential cytotoxicity in cancer over antigen presenting cells, confirming the tumor-targeting of AU-011. AU-011 treatment induced immunogenic cell death in several murine cancer cell lines through the release and exposure of damage-associated molecular patterns (DAMPs), resulting in the maturation of dendritic cells. Furthermore, AU-011 in combination with ICI antibodies demonstrated greater efficacy than AU-011 alone, or ICI antibodies alone against established MC38 tumors in mice, resulting in complete tumor response in all treated animals for specific combinations. Finally, AU-011 and anti-PD-L1/ anti-LAG-3 antibody treatment was an optimal combination in an abscopal model of metastatic disease, inducing complete cures in approximately 75 % of animals. Conclusions: Based on our observations, we conclude that AU-011 treatment combined with immune checkpoint inhibition is effective against both primary tumors and distant metastases, and identify anti-PD-L1/ anti-LAG-3 as the most potent combination with AU-011. These data may support an investigation of AU-011 in this combination in future clinical trials.[Table: see text]

Discovery of SY-5609: A Selective, Noncovalent Inhibitor of CDK7

CDK7 has emerged as an exciting target in oncology due to its roles in two important processes that are misregulated in cancer cells: cell cycle and transcription. This report describes the discovery of SY-5609, a highly potent (sub-nM CDK7 Kd) and selective, orally available inhibitor of CDK7 that entered the clinic in 2020 (ClinicalTrials.gov Identifier: NCT04247126). Structure-based design was leveraged to obtain high selectivity (>4000-times the closest off target) and slow off-rate binding kinetics desirable for potent cellular activity. Finally, incorporation of a phosphine oxide as an atypical hydrogen bond acceptor helped provide the required potency and metabolic stability. The development candidate SY-5609 displays potent inhibition of CDK7 in cells and demonstrates strong efficacy in mouse xenograft models when dosed as low as 2 mg/kg.

Abstract C091: Preclinical evaluation of PK, PD, and antitumor activity of the oral, non-covalent, potent and highly selective CDK7 inhibitor, SY-5609, provides rationale for clinical development in multiple solid tumor indications

Introduction: CDK7 is a key regulator of transcription and cell cycle progression and has been implicated in multiple tumor types driven by aberrant transcriptional control (e.g. MYC-, ESR1-activation) and/or aberrant cell cycle control (e.g. RB1, CCNE1, CDKN2A alterations). SY-5609 is an oral, potent, and highly selective CDK7 inhibitor that is advancing through IND-enabling studies to support initiation of a planned Phase 1 oncology trial in early 2020. Here we report on the relationship between pharmacokinetics (PK), pharmacodynamics (PD), and tumor growth inhibition (TGI) in xenograft models of tumor types with transcriptional and/or cell cycle aberrations including high grade serous ovarian cancer (HGSOC), small cell lung cancer (SCLC), triple negative breast cancer (TNBC), and estrogen receptor positive breast cancer (ER+BC). Methods: The relationship between SY-5609 PK, PD, and TGI was evaluated in xenograft models of HGSOC (OVCAR3) and TNBC (HCC70) using once daily (QD) or twice daily (BID) dosing via oral gavage. SY-5609 TGI was evaluated as a single agent (SA) QD in patient-derived xenograft (PDX) models of HGSOC (n=3), SCLC (n=4), TNBC (n=4), and in combination with once weekly fulvestrant in ER+BC PDX models selected in vivo for resistance to the CDK4/6 inhibitor palbociclib (n=1) or resistance to both palbociclib and fulvestrant (n=1). Results: SY-5609 plasma exposure was dose proportional and did not accumulate after repeated therapeutic doses. Dose-dependent transcriptional responses in xenograft tissue were observed within 4 hours of SY-5609 dosing and were sustained for 24 hours. TGI was dose-dependent, with tumor regressions observed at doses significantly below the maximum tolerated dose (MTD). Similar TGI was seen when the same daily dose was administered either QD or BID suggesting that the effect was driven by overall exposure or minimum concentration. In HGSOC, SCLC, and TNBC PDX models, SA SY-5609 induced >50% TGI in all models tested (11/11), with 7/11 (64%) demonstrating robust anti-tumor activity (≥90% TGI or regression): 3/3 HGSOC, 2/4 SCLC, and 2/4 TNBC. In a palbociclib-resistant ER+BC PDX model, the combination of SY-5609 and fulvestrant induced significant TGI (89%), with no evident tumor regrowth up to 21 days after dosing cessation, distinguishing the observed effects from SY-5609 SA or fulvestrant SA. In a palbociclib and fulvestrant double-resistant ER+ BC PDX model, SY-5609 SA resulted in 33% TGI and fulvestrant SA had no activity. In contrast, the combination of SY-5609 and fulvestrant demonstrated significant TGI (68%; p<0.0001 vs fulvestrant SA), suggesting re-sensitization to fulvestrant. Conclusions: We have characterized PK, PD, and anti-tumor activity of the CDK7 inhibitor SY-5609 in a series of xenograft models. Exposure in plasma is dose-proportional and does not accumulate at therapeutic dose levels. SY-5609 induces dose-dependent transcriptional responses in tumor xenograft tissue and shows robust TGI, including regressions, in PDX models derived from multiple solid tumor indications. These results highlight the broad potential for SY-5609 across a variety of solid tumor types, including treatment resistant ER+BC, and support the development of SY-5609 in early phase clinical trials.

Citation Format: Liv H Johannessen, Shanhu Hu, Nan Ke, Anthony D'Ippolito, Nisha Rajagopal, Jason Marineau, Anneli Savinainen, William Zamboni, Graeme Hodgson. Preclinical evaluation of PK, PD, and antitumor activity of the oral, non-covalent, potent and highly selective CDK7 inhibitor, SY-5609, provides rationale for clinical development in multiple solid tumor indications [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C091. doi:10.1158/1535-7163.TARG-19-C091

Pharmacokinetics and intraocular pressure-lowering activity of TAK-639, a novel C-type natriuretic peptide analog, in rabbit, dog, and monkey

TAK-639 is a topical, 9-amino acid, synthetic, C-type natriuretic peptide analog in development for the treatment of primary open-angle glaucoma and ocular hypertension. This study investigated the impact of TAK-639 on intraocular pressure (IOP), the levels of TAK-639 in aqueous humor, and the pharmacokinetic/pharmacodynamic relationship of TAK-639 following topical ocular administration to normotensive female Dutch belted rabbits, beagle dogs, and cynomolgus monkeys. In the IOP studies, rabbits (n = 6/group) and dogs (n = 8/group) received a single topical ocular dose of TAK-639 0.03%, 0.1%, 0.3%, or 0.6% in the right eye and vehicle in the left eye; monkeys (n = 8/group) received TAK-639 0.1%, 0.3%, 0.6%, 0.9%, or 1.2% in the right eye only. IOP was measured pre dose and at various time points from 0.5 to 24 h post dose for rabbits, and 1-48 h post dose for dogs and monkeys. To assess exposure in aqueous humor, another set of animals received a single ocular dose of TAK-639 0.03%, 0.1%, 0.3%, or 0.6% (rabbits, n = 20/group; dogs, n = 14/group) or TAK-639 0.3%, 0.6%, or 1.2% (monkeys, n = 10/group) in both eyes. Aqueous humor and plasma were collected at the same post dose time points at which IOP was measured. Aqueous humor and plasma TAK-639 concentrations were measured by liquid chromatography-mass spectrometry, and pharmacokinetic parameters were estimated with non-compartmental analysis. Topical ocular administration of TAK-639 resulted in a dose-dependent decrease in IOP, with maximum mean decreases in IOP ranging from -8.90% to -34.4% in the rabbit, from -16.5% to -26.4% in the dog, and from -3.43% to -13.5% in the monkey. The duration of the IOP-lowering effect was 12 h in the rabbit and monkey and 48 h in the dog. TAK-639 exposure in aqueous humor (both maximum concentration and area under the curve) was also dose dependent, with maximum concentration ranging from 0.152 to 93.6 ng/mL (0.03% and 0.6% doses, respectively) in rabbits, 0.490-13.8 ng/mL (0.03% and 0.3% doses, respectively) in dogs, and 1.16-18.1 ng/mL (0.3% and 1.2% doses, respectively) in monkeys. The pharmacokinetic/pharmacodynamic profile, when fitted to an inhibitory sigmoidal model, demonstrated that TAK-639 exposure in aqueous humor correlated well with IOP reduction in these species. The TAK-639 exposure in aqueous humor at half maximal IOP reduction (EC₅₀) was lower in monkey and dog than in rabbit (0.2 and 0.4 vs. 2.0 ng/mL, respectively). In plasma, quantifiable concentrations of TAK-639 were low and detectable predominantly at early time points. In conclusion, in rabbit, dog, and monkey, a single topical ocular drop of TAK-639 had a significant IOP-lowering effect that correlated well with increases in TAK-639 levels in aqueous humor and resulted in minimal systemic exposure of TAK-639.

Effects of TAK-639, a novel topical C-type natriuretic peptide analog, on intraocular pressure and aqueous humor dynamics in mice

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness, and individuals with ocular hypertension are at risk to develop POAG. Currently, the only modifiable risk factor for glaucoma progression is lowering of intraocular pressure (IOP). A novel mechanism for lowering IOP involves activation of the type B natriuretic peptide receptor (NPR-B), the naturally occurring agonist of which is C-type natriuretic peptide (CNP). Being a cyclic peptide of 22 amino acids, CNP does not readily penetrate the cornea and its ocular hypotensive effect requires intraocular injection. TAK-639 is a synthetic, cornea-permeable, 9-amino acid CNP analog has been studied for the treatment of ocular hypertension and POAG. We assessed TAK-639 in a receptor binding profile and the effects of TAK-639 on NPR-B-mediated cyclic GMP production in cultured transformed human trabecular meshwork (TM) cells (GTM-3). We also evaluated the effects of topical ocular administration of TAK-639 on mouse IOP and aqueous humor dynamics. Among 89 non-natriuretic peptide receptors, transporters, and channels evaluated, TAK-639 at 10 μM displaced ligand binding by more than 50% to only two receptors: the type 2 angiotensin receptor (IC₅₀ = 8.2 μM) and the cholecystokinin A receptor (IC₅₀ = 25.8 μM). In vitro, TAK-639 selectively activates NPR-B (EC₅₀ = 61 ± 11 nM; GTM-3 cells) relative to NPR-A (EC₅₀ = 2179 ± 670 nM; 293T cells). In vivo, TAK-639 lowered mouse IOP by three mechanisms: increase in aqueous humor outflow facility (C), reduction in the aqueous humor formation rate (Fin), and reduction in episcleral venous pressure (Pe). The maximum mean IOP decreases from baseline were -12.1%, -21.0%, and -36.1% for 0.1%, 0.3%, and 0.6% doses of TAK-639, respectively. Maximum IOP-lowering effect was seen at 2 h, and the duration of action was >6 h. With TAK-639 0.6%, at 2 h post-dose, aqueous outflow facility (C) increased by 155.8%, Fin decreased by 41.0%, the uveoscleral outflow rate (Fu) decreased by 52.6%, and Pe decreased by 31.5% (all p < 0.05). No ocular adverse effects were observed. TAK-639 is an efficacious IOP-lowering agent, with a unique combination of mechanisms of action on both aqueous formation and aqueous outflow facility. Further study of this mechanism of treatment may optimize pharmacologic outcomes and provide disease management in patients with POAG and ocular hypertension.

Abstract 4421: SY-5609, an orally available selective CDK7 inhibitor demonstrates broad anti-tumor activity in vivo

Previously, we reported on a series of highly potent, selective, and non-covalent CDK7 inhibitors that demonstrated antiproliferative activity against triple-negative breast cancer (TNBC) and ovarian cancer (OVA) cell lines and tumor growth inhibition in cell line-derived (CDX) and patient-derived (PDX) mouse xenograft models. Here, we report on the in vitro and in vivo profile of our development candidate, SY-5609. Methods: Kinase inhibition assays at both Km and 2 mM [ATP] were used to assess inhibition of CDK2, CDK7, CDK9, and CDK12. SPR was used to determine the Kd, kon, and koff binding characteristics of SY-5609 to immobilized CDK7/Cyclin H dimer. CDK7 compound occupancy was determined using a biotinylated small molecule probe to pull down free CDK7 following incubating of HL60 cells with SY-5609. Inhibition of tumor cell line growth was assessed following 72 hrs of incubation with SY-5609. Flow cytometry was used to assess apoptosis and cell cycle modulation after 48 hrs of treatment. Effects on DNA damage and repair were assessed by immunofluorescence staining for γH2AX and RAD51 proteins. To assess in vivo effects, mice were implanted subcutaneously and randomized for treatment when tumors reached 150-200 mm3 and dosed orally for 3 weeks by both QD and BID dosing regimens. Collected tumor tissue samples were analyzed for protein levels of MCL1, pCDK2, MYC, and RNA Pol II CTD pSer5 by western blot. Results: SY-5609 bound CDK7/Cyclin H with a Kd of 0.059 nM and occupied CDK7 in HL60 cells with an EC50 of 33 nM. Cell growth inhibition EC50 values were 6-17 nM in a panel of solid tumor cell lines. Selectivity of SY-5609 over CDK12, CDK9, and CDK2 was 2492-, 2508-, and 8068-fold, respectively. SY-5609 led to induction of apoptosis, cell cycle arrest, and inhibition of DNA damage repair in tumor cell lines. Dose-dependent tumor growth inhibition was observed in a panel of CDX and PDX solid tumor models with both QD and BID dosing of SY-5609 with resulting decreases in direct (pCDK2, RNA Pol II CTD pSer5) and indirect (MCL1, MYC) protein biomarkers. In summary, we describe SY-5609, an orally available, potent, and selective CDK7 inhibitor that drives strong responses in CDX and PDX tumor models. These data support the rationale for advancing SY-5609 into IND-enabling studies.

Citation Format: Shanhu Hu, Jason Marineau, Kristin Hamman, Michael Bradley, Anneli Savinainen, Sydney Alnemy, Nisha Rajagopal, David Orlando, Claudio Chuaqui, Eric Olson. SY-5609, an orally available selective CDK7 inhibitor demonstrates broad anti-tumor activity in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4421.

Differential efficacy of the TSPO ligands etifoxine and XBD-173 in two rodent models of Multiple Sclerosis

Neurosteroids such as progesterone and allopregnanolone have been shown to exert neuroprotective effects under a variety of pathological or insult conditions, and there is evidence that the neurosteroid system is perturbed in Multiple Sclerosis (MS) patients. Neurosteroids are synthesized in the central nervous system (CNS) through a series of metabolic transformations, beginning with a rate-limiting step of cholesterol transport through the outer mitochondrial membrane via the transporter translocator protein (TSPO). We examined the effects of etifoxine and XBD-173, two different brain penetrant TSPO agonists, for their ability to ameliorate clinical signs in two different experimental autoimmune encephalitis (EAE) models. Etifoxine, as previously reported, was efficacious in EAE, while XBD-173 was not. Surprisingly, XBD-173, but not etifoxine elevated relevant neurosteroids in brain of female rats and differed in its ability to exert anti-inflammatory and direct neuroprotective effects in vitro as compared to etifoxine. We conclude that the neurosteroid elevations produced in brain by XBD-173 are not sufficient to ameliorate EAE and suggest that etifoxine may have additional mechanisms of action that provide therapeutic benefit in this model system.

IKKbeta inhibition protects against bone and cartilage destruction in a rat model of rheumatoid arthritis

OBJECTIVE

The IKK complex regulates NF-kappaB activation, an important pathway implicated in the rheumatoid arthritis (RA) disease process. This study was undertaken to assess the efficacy of N-(6-chloro-7-methoxy-9H-beta-carbolin-8-yl)-2-methylnicotinamide (ML120B), a potent and selective small molecule inhibitor of IKKbeta.

METHODS

Polyarthritis was induced in rats by injection of Freund's complete adjuvant into the hind footpad. ML120B was administered orally twice daily, either prophylactically or therapeutically. Paw volumes and body weights were measured every 2-3 days throughout the study. We assessed bone erosions by several methods: histologic evaluation, quantitative micro-computed tomography (micro-CT) imaging analysis, and measurement of type I collagen fragments in the serum. Quantitative polymerase chain reaction was used to evaluate expression of messenger RNA for genes related to inflammation and to bone and cartilage integrity.

RESULTS

Oral administration of ML120B inhibited paw swelling in a dose-dependent manner (median effective dosage 12 mg/kg twice daily) and offered significant protection against arthritis-induced weight loss as well as cartilage and bone erosion. We were able to directly demonstrate that NF-kappaB activity in arthritic joints was reduced after ML120B administration. Also, we observed that down-regulation of the NF-kappaB pathway via IKKbeta inhibition dampened the chronic inflammatory process associated with rat adjuvant-induced arthritis.

CONCLUSION

The results of the present study suggest that IKKbeta inhibition is an effective therapeutic approach to treat both the inflammation and the bone/cartilage destruction observed in RA. Methods for the determination of serum markers for bone and cartilage destruction, as well as micro-CT analysis, may aid in predicting and evaluating the therapeutic efficacy of IKKbeta inhibition therapy in humans.

Application of surface roughness analysis on micro-computed tomographic images of bone erosion: examples using a rodent model of rheumatoid arthritis

Quantifying the bone erosion in preclinical models of rheumatoid arthritis is valuable for the evaluation of drug treatments. This study introduces a three-dimensional method for bone surface roughness measurement from micro-computed tomographic data obtained from rats subjected to collagen-induced arthritis (CIA), in which the degree of bone erosion is related to the severity and the duration of the disease. In two studies of rat CIA, the surface roughness of the talus bone following 21 days of disease increased 559% and 486% from the control group. At 41 days following disease induction, the roughness of the bone surface increased 857% above baseline. The roughness of the control samples was similar from each study (less than 4% different), demonstrating the robustness of the algorithm. Treatment with methotrexate at 0.1 mg/kg daily demonstrated significant protection from bone erosion, whereas the 0.05 mg/kg daily dose was not efficacious (98% versus 22% inhibition of roughness-measured bone erosion). The main advantage of such an algorithm is demonstrated in the preclinical drug study of rat CIA with methotrexate treatment, indicating the immediate utility of this approach in drug development studies.

Quantitative Analysis of Micro-CT Imaging and Histopathological Signatures of Experimental Arthritis in Rats

Micro-computed tomographic (micro-CT) imaging provides a unique opportunity to capture 3-D architectural information in bone samples. In this study of pathological joint changes in a rat model of adjuvant-induced arthritis (AA), quantitative analysis of bone volume and roughness were performed by micro-CT imaging and compared with histopathology methods and paw swelling measurement. Micro-CT imaging of excised rat hind paws (n = 10) stored in formalin consisted of approximately 600 30-mum slices acquired on a 512 x 512 image matrix with isotropic resolution. Following imaging, the joints were scored from H&E stained sections for cartilage/bone erosion, pannus development, inflammation, and synovial hyperplasia. From micro-CT images, quantitative analysis of absolute bone volumes and bone roughness was performed. Bone erosion in the rat AA model is substantial, leading to a significant decline in tarsal volume (27%). The result of the custom bone roughness measurement indicated a 55% increase in surface roughness. Histological and paw volume analyses also demonstrated severe arthritic disease as compared to controls. Statistical analyses indicate correlations among bone volume, roughness, histology, and paw volume. These data demonstrate that the destructive progression of disease in a rat AA model can be quantified using 3-D micro-CT image analysis, which allows assessment of arthritic disease status and efficacy of experimental therapeutic agents.

Kainate receptor activation induces mixed lineage kinase-mediated cellular signaling cascades via post-synaptic density protein 95

Kainate receptor glutamate receptor 6 (GluR6) subunit-deficient and c-Jun N-terminal kinase 3 (JNK3)-null mice share similar phenotypes including resistance to kainite-induced epileptic seizures and neuronal toxicity (Yang, D. D., Kuan, C-Y., Whitmarsh, A. J., Rincon, M., Zheng, T. S., Davis, R. J., Rakis, P., and Flavell, R. (1997) Nature 389, 865-869; Mulle, C., Seiler, A., Perez-Otano, I., Dickinson-Anson, H., Castillo, P. E., Bureau, I., Maron, C., Gage, F. H., Mann, J. R., Bettler, B., and Heinemmann, S. F. (1998) Nature 392, 601-605). This suggests that JNK activation may be involved in GluR6-mediated excitotoxicity. We provide evidence that post-synaptic density protein (PSD-95) links GluR6 to JNK activation by anchoring mixed lineage kinase (MLK) 2 or MLK3, upstream activators of JNKs, to the receptor complex. Association of MLK2 and MLK3 with PSD-95 in HN33 cells and rat brain preparations is dependent upon the SH3 domain of PSD-95, and expression of GluR6 in HN33 cells activated JNKs and induced neuronal apoptosis. Deletion of the PSD-95-binding site of GluR6 reduced both JNK activation and neuronal toxicity. Co-expression of dominant negative MLK2, MLK3, or mitogen-activated kinase kinase (MKK) 4 and MKK7 also significantly attenuated JNK activation and neuronal toxicity mediated by GluR6, and co-expression of PSD-95 with a deficient Src homology 3 domain also inhibited GluR6-induced JNK activation and neuronal toxicity. Our results suggest that PSD-95 plays a critical role in GluR6-mediated JNK activation and excitotoxicity by anchoring MLK to the receptor complex.

A genetic basis for atrophy: dominant non-responsiveness and helicobacter induced gastritis in F(1) hybrid mice

BACKGROUND

The importance of host factors in helicobacter induced gastritis has been shown in animal models. Infection of most mouse strains with Helicobacter felis results in a functional atrophic gastritis, while other strains remain gastritis free.

AIMS

To investigate these host factors further by using genetic crosses of responder and non-responder mice.

METHODS

F(1) hybrids of the non-responder CBA/Ca strain and three strains of mice known to develop H felis induced gastritis were infected for three months with H felis. Gastritis was assessed by histopathology and serum antibody responses by ELISA.

RESULTS

Infection of CBA/Ca mice and F(1) hybrids induced little or no gastritis. Analyses of the antibody responses in these mice revealed virtually undetectable anti-helicobacter antibody levels despite colonisation with high numbers of H felis. In contrast, infection of H felis responsive strains induced gastritis and a significant humoral immune response.

CONCLUSIONS

The non-responsiveness of CBA/Ca mice to H felis infection is dominantly inherited. The lack of gastritis in CBA mice and their offspring is probably due to active suppression of the immune response normally mounted against H felis. Investigation of these mechanisms will provide important insights relevant to induction of gastric atrophy and cancer in humans.

Helicobacter pylori infection in immunized mice lacking major histocompatibility complex class I and class II functions

The role of major histocompatibility complex (MHC) class I- and class II-restricted functions in Helicobacter pylori infection and immunity upon oral immunization was examined in vivo. Experimental challenge with H. pylori SS1 resulted in significantly greater (P </= 0.025) colonization of MHC class I and class II mutant mice than C57BL/6 wild-type mice. Oral immunization with H. pylori whole-cell lysates and cholera toxin adjuvant significantly reduced the magnitude of H. pylori infection in C57BL/6 wild-type (P = 0.0083) and MHC class I knockout mice (P = 0.0048), but it had no effect on the H. pylori infection level in MHC class II-deficient mice. Analysis of the anti-H. pylori antibody levels in serum showed a dominant serum immunoglobulin G1 (IgG1) response in immunized C57BL/6 wild-type and MHC class I mutant mice but no detectable serum IgG response in MHC class II knockout mice. Populations of T-cell-receptor (TCR) alphabeta+ CD4(+) CD54(+) cells localized to gastric tissue of immunized C57BL/6 wild-type and MHC class I knockout mice, but TCRalphabeta+ CD8(+) cells predominated in the gastric tissue of immunized MHC class II-deficient mice. These observations show that CD4(+) T cells engaged after mucosal immunization may be important for the generation of a protective anti-H. pylori immune response and that CD4(+) CD8(-) and CD4(-) CD8(+) T cells regulate the extent of H. pylori infection in vivo.