Autologous human preclinical modeling of melanoma interpatient clinical responses to immunotherapeutics

BACKGROUND

Despite recent advances in immunotherapy, a substantial population of late-stage melanoma patients still fail to achieve sustained clinical benefit. Lack of translational preclinical models continues to be a major challenge in the field of immunotherapy; thus, more optimized translational models could strongly influence clinical trial development. To address this unmet need, we designed a preclinical model reflecting the heterogeneity in melanoma patients' clinical responses that can be used to evaluate novel immunotherapies and synergistic combinatorial treatment strategies. Using our all-autologous humanized melanoma mouse model, we examined the efficacy of a novel engineered interleukin 2 (IL-2)-based cytokine variant immunotherapy.

METHODS

To study immune responses and antitumor efficacy for human melanoma tumors, we developed an all-autologous humanized melanoma mouse model using clinically annotated, matched patient tumor cells and peripheral blood mononuclear cells (PBMCs). After inoculating immunodeficient NSG mice with patient tumors and an adoptive cell transfer of autologous PBMCs, mice were treated with anti-PD-1, a novel investigational engineered IL-2-based cytokine (nemvaleukin), or recombinant human IL-2 (rhIL-2). The pharmacodynamic effects and antitumor efficacy of these treatments were then evaluated. We used tumor cells and autologous PBMCs from patients with varying immunotherapy responses to both model the diversity of immunotherapy efficacy observed in the clinical setting and to recapitulate the heterogeneous nature of melanoma.

RESULTS

Our model exhibited long-term survival of engrafted human PBMCs without developing graft-versus-host disease. Administration of an anti-PD-1 or nemvaleukin elicited antitumor responses in our model that were patient-specific and were found to parallel clinical responsiveness to checkpoint inhibitors. An evaluation of nemvaleukin-treated mice demonstrated increased tumor-infiltrating CD4+ and CD8+ T cells, preferential expansion of non-regulatory T cell subsets in the spleen, and significant delays in tumor growth compared with vehicle-treated controls or mice treated with rhIL-2.

CONCLUSIONS

Our model reproduces differential effects of immunotherapy in melanoma patients, capturing the inherent heterogeneity in clinical responses. Taken together, these data demonstrate our model's translatability for novel immunotherapies in melanoma patients. The data are also supportive for the continued clinical investigation of nemvaleukin as a novel immunotherapeutic for the treatment of melanoma.

Nemvaleukin alfa, a novel engineered IL-2 fusion protein, drives antitumor immunity and inhibits tumor growth in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is a deadly disease with a 5-year survival of less than 7%. The addition of immunotherapy to chemotherapy was recently approved as first-line treatment; however, the improved clinical benefit is modest, highlighting an urgent need for new treatment strategies. Nemvaleukin alfa, a novel engineered interleukin-2 fusion protein currently in phase I-III studies, is designed to selectively expand cytotoxic natural killer (NK) cells and CD8⁺ T cells. Here, using a novel SCLC murine model, we investigated the effects of a mouse version of nemvaleukin (mNemvaleukin) on tumor growth and antitumor immunity.

METHODS

A novel Rb1 ^-/- p53 ^-/- p130 ^-/- SCLC model that mimics human disease was generated. After confirming tumor burden by MRI, mice were randomized into four treatment groups: vehicle, mNemvaleukin alone, chemotherapy (cisplatin+etoposide) alone, or the combination of mNemvaleukin and chemotherapy. Tumor growth was measured by MRI and survival was recorded. Tumor-infiltrating lymphocytes and peripheral blood immune cells were analyzed by flow cytometry. Cytokine and chemokine secretion were quantified and transcriptomic analysis was performed to characterize the immune gene signatures.

RESULTS

mNemvaleukin significantly inhibited SCLC tumor growth, which was further enhanced by the addition of chemotherapy. Combining mNemvaleukin with chemotherapy provided the most significant survival benefit. Profiling of tumor-infiltrating lymphocytes revealed mNemvaleukin expanded the total number of tumor-infiltrating NK and CD8⁺ T cells. Furthermore, mNemvaleukin increased the frequencies of activated and proliferating NK and CD8⁺ T cells in tumors. Similar immune alterations were observed in the peripheral blood of mNemvaleukin-treated mice. Of note, combining mNemvaleukin with chemotherapy had the strongest effects in activating effector and cytotoxic CD8⁺ T cells. mNemvaleukin alone, and in combination with chemotherapy, promoted proinflammatory cytokine and chemokine production, which was further confirmed by transcriptomic analysis.

CONCLUSIONS

mNemvaleukin, a novel cytokine-based immunotherapy, significantly inhibited murine SCLC tumor growth and prolonged survival, which was further enhanced by the addition of chemotherapy. mNemvaleukin alone, and in combination with chemotherapy, drove a strong antitumor immune program elicited by cytotoxic immune cells. Our findings support the evaluation of nemvaleukin alone or in combination with chemotherapy in clinical trials for the treatment of SCLC.

Nemvaleukin alfa combination therapy for gastrointestinal (GI) cancers: Preclinical evidence and clinical data from the ARTISTRY-1 trial

659

Background: Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8+ T and NK cells, with minimal expansion of regulatory T cells. Inherently active, nemvaleukin neither requires metabolic/proteolytic conversion nor degrades into native IL-2. Preclinical characterization confirmed receptor selectivity and antitumor activity of nemvaleukin alone and with checkpoint inhibitors (CPIs) and informed dose selection for the first-in-human study ARTISTRY-1; other combination regimens are ongoing evaluation. In ARTISTRY-1, responses with nemvaleukin in combination with pembrolizumab were observed in a variety of tumors, including GI. In addition to the clinical outcomes of these patients (pts), we describe preclinical evaluation of nemvaleukin with tyrosine kinase inhibitors (TKIs)—a drug class indicated for some GI cancers. Methods: Pts with GI cancers who had progressed on prior therapy were enrolled into cohorts of mixed tumor types in ARTISTRY-1 (NCT02799095) and received IV nemvaleukin (3 µg/kg) and pembrolizumab (200 mg). Outcomes presented include antitumor activity and safety as of August 2021. Combinations of nemvaleukin with TKIs were evaluated in mouse tumor models, including colorectal adenocarcinoma (MC38). Results: Clinically, 26 pts with GI cancer (colon/colorectal, n = 14; esophageal, n = 5; hepatocellular, n = 3; pancreatic, n = 3; gastric, n = 1) received nemvaleukin + pembrolizumab (median 3 cycles [range: 1-24]). Median age was 55 y (range: 26-82), ECOG performance status was 0 (n = 6) or 1 (n = 20), and median prior lines of therapy was 3 (range: 1-6). Four pts had a partial response, 2 with esophageal, 1 with MSI-H colorectal, and 1 with pancreatic cancer, with target lesion decreases of 37% to 63%. Six pts had stable disease. Two responders remain on treatment (> 36 and > 80 wks for colorectal and esophageal cancer, respectively). Frequent (> 25%) nemvaleukin-related adverse events (AEs) among all pts receiving nemvaleukin combination (n = 156) were chills (58%), pyrexia (53%), nausea (29%), and fatigue (29%). Grade ≥3 nemvaleukin-related AEs (≥8%) were reported in 48%, including anemia (12%), neutrophil count decreased (10%), and neutropenia (8%). In mice, the combination of the mouse ortholog of nemvaleukin with VEGF TKIs showed improved antitumor activity and survival, along with increased immune activation and angiogenesis blockade in the tumor microenvironment compared with any compound alone. Conclusions: Emerging clinical data show responses in GI tumors may be achieved with nemvaleukin/pembrolizumab with manageable safety. Preclinical evidence of antitumor activity of nemvaleukin with CPIs or TKIs warrants further exploration of nemvaleukin in new combinations for pts with GI cancers. Clinical trial information: NCT02799095.

Pharmacokinetics and Pharmacodynamic Effects of Nemvaleukin Alfa, a Selective Agonist of the Intermediate-Affinity IL-2 Receptor, in Cynomolgus Monkeys

Nemvaleukin alfa (nemvaleukin, ALKS 4230) is a novel cytokine, created by the fusion of circularly permuted interleukin-2 (IL-2) to the IL-2Rα subunit of the IL-2 receptor (IL-2R) complex, that confers selectivity for the intermediate-affinity IL-2R expressed on CD8⁺ T cells and natural killer (NK) cells. The pharmacokinetics and selective pharmacodynamic properties of nemvaleukin have been demonstrated using in vitro and in vivo mouse models. The pharmacokinetic/pharmacodynamic effects of nemvaleukin on immune cell subtypes were evaluated in cynomolgus monkeys following intravenous (i.v.) and subcutaneous (s.c.) administration to inform dose selection and predict pharmacodynamic effects in humans. Male drug-naïve cynomolgus monkeys (N = 15) were administered either single-dose (i.v. 0.3 mg/kg; s.c. 0.3 mg/kg or 1.0 mg/kg) or repeated-doses (i.v. 0.1 mg/kg on days 1-5 or s.c. 0.5 mg/kg on days 1 and 4) of nemvaleukin. Serial blood samples were collected for pharmacokinetic assessment, immunophenotyping by flow cytometry, and profiling of serum cytokines. Repeat-dose s.c. administration of nemvaleukin with less frequent dosing resulted in total systemic exposure and trough serum concentrations comparable to those seen with i.v. administration, with lower peak serum concentrations. Transient elevation of interferon-γ and IL-6 peaked at 2 and 8 hours after i.v. and s.c. administration, respectively. Selective expansion of immunoprotective central memory, effector memory, and terminal effector CD8⁺ T cells and CD56⁺ NK cells, and minimal expansion of immunosuppressive CD4⁺CD25⁺FoxP3⁺ regulatory T cells was observed following both i.v. and s.c. administration. These data support the ongoing clinical evaluation of i.v. and s.c. nemvaleukin. Significance Statement Administration of the novel interleukin-2 receptor agonist nemvaleukin alfa (nemvaleukin, ALKS 4230) to cynomolgus monkeys resulted in selective expansion of immune effector cells, including CD8⁺ T and NK cells, with minimal effects on immunosuppressive CD4⁺ regulatory T cells, confirming the design of nemvaleukin and highlighting its potential as a cancer immunotherapy. Subcutaneous administration of nemvaleukin achieved systemic exposure and immunostimulatory effects similar to those observed following more frequent intravenous dosing and may represent a practical alternative in a clinical setting.

ALKS 4230: a novel engineered IL-2 fusion protein with an improved cellular selectivity profile for cancer immunotherapy

BACKGROUND

Interleukin-2 (IL-2) plays a pivotal role in immune homeostasis due to its ability to stimulate numerous lymphocyte subsets including natural killer (NK) cells, effector CD4⁺ and CD8⁺ T cells, and regulatory T cells (T_regs). Low concentrations of IL-2 induce signaling through the high-affinity IL-2 receptor (IL-2R) comprised of IL-2Rα, IL-2Rβ, and common γ chain (γ_c), preferentially expressed on T_regs. Higher concentrations of IL-2 are necessary to induce signaling through the intermediate-affinity IL-2R, composed of IL-2Rβ and γ_c, expressed on memory CD8⁺ T cells and NK cells. Recombinant human IL-2 (rhIL-2) is approved for treatment of metastatic melanoma and renal cell carcinoma (RCC), but adverse events including capillary leak syndrome, potentially mediated through interaction with the high-affinity IL-2R, limit its therapeutic use. Furthermore, antitumor efficacy of IL-2 may also be limited by preferential expansion of immunosuppressive T_regs. ALKS 4230 is an engineered fusion protein comprised of a circularly-permuted IL-2 with the extracellular domain of IL-2Rα, designed to selectively activate effector lymphocytes bearing the intermediate-affinity IL-2R.

RESULTS

ALKS 4230 was equipotent to rhIL-2 in activating human cells bearing the intermediate-affinity IL-2R, and less potent than rhIL-2 on cells bearing the high-affinity IL-2R. As observed in vitro with primary human cells from healthy donors and advanced cancer patients, ALKS 4230 induced greater activation and expansion of NK cells with reduced expansion of T_regs relative to rhIL-2. Similarly, in mice, ALKS 4230 treatment stimulated greater expansion of NK cells and memory-phenotype CD8⁺ T cells at doses that did not expand or activate T_regs. ALKS 4230 treatment induced significantly lower levels of proinflammatory cytokines, including tumor necrosis factor alpha, interleukin-6, and interferon gamma relative to rhIL-2. Furthermore, ALKS 4230 exhibited superior antitumor efficacy in the mouse B16F10 lung tumor model, where ALKS 4230 could be administered via multiple routes of administration and dosing schedules while achieving equivalent antitumor efficacy.

CONCLUSIONS

ALKS 4230 exhibited enhanced pharmacokinetic and selective pharmacodynamic properties resulting in both improved antitumor efficacy and lower indices of toxicity relative to rhIL-2 in mice. These data highlight the potential of ALKS 4230 as a novel cancer immunotherapy, and as such, the molecule is being evaluated clinically.

Abstract 2202: The combination of a mouse ortholog of ALKS 4230, a selective agonist of the intermediate affinity IL-2 receptor, and the angiogenesis inhibitor lucitanib enhances antitumor activity

ALKS 4230, an engineered cytokine designed for selective binding to the intermediate affinity interleukin-2 receptor (IL-2R), is being evaluated as a monotherapy and in combination with pembrolizumab in patients with advanced solid tumors. The selectivity of ALKS 4230 is achieved through stable fusion of circularly permuted IL-2 to IL-2Rα, with the goal of driving antitumor responses via selective activation of CD8+ T cells and NK cells, while avoiding activation of regulatory T cells (Tregs), which express the high affinity IL-2R. High levels of vascular endothelial growth factor (VEGF) are associated with an immunosuppressive tumor microenvironment and diminished response to high-dose IL-2. Lucitanib is an anti-angiogenic, multi-tyrosine kinase inhibitor targeting VEGFR1-3, PDGFRα/β, and FGFR1-3. We evaluated the antitumor efficacy and mechanism of the combination of RDB 1462, the mouse ortholog of ALKS 4230, and lucitanib in the MC38 mouse syngeneic tumor model.

C57BL/6 mice were subcutaneously implanted with MC38 cells and treated with RDB 1462 (1.5 mg/kg and 3 mg/kg once every 3 days for 3 weeks), lucitanib (10 mg/kg daily for 28 days), or the combination of both molecules. After 11 days of treatment, lucitanib monotherapy resulted in 100% tumor growth inhibition (TGI), while 1.5 mg/kg and 3 mg/kg RDB 1462 monotherapy resulted in 25% and 51% TGI, respectively. Lucitanib monotherapy extended survival, with a mean survival time (MST) of 39 days compared to 15 days for vehicle, with no complete tumor regressions. MSTs were 18-22 days for RDB 1462 monotherapy groups, 60 days for the lower dose combination arm, and >60 days for the higher dose combination. Durable complete tumor regressions were observed in 1/20 mice treated with either dose of RDB 1462 monotherapy and 5/10 mice treated with the lower dose of RDB 1462 in combination with lucitanib. 10/10 mice treated with the higher dose of RDB 1462 in combination with lucitanib exhibited complete responses on Day 60. Flow cytometric analyses revealed that RDB 1462 treatment induced significant peripheral CD8+ T cell expansion compared to vehicle (p<0.05) without an increase in Foxp3+ Tregs. This effect was enhanced by the combination of RDB 1462 with lucitanib. The combination led to a significant (p<0.05) increase in intratumoral CD8+ T cells and dendritic cells (CD11c+F4/80−), together with a reduction in tumor-associated macrophages (CD11b+F4/80+). The combination treatment elicited a distinct gene expression profile in tumors by RNA-Seq, merging the immunostimulatory effects of RDB 1462 with the anti-angiogenic effects of lucitanib.

The combination of an intermediate affinity IL-2R-selective cytokine and an angiogenesis inhibitor resulted in durable dose-dependent antitumor efficacy in the MC38 mouse tumor model.

Citation Format: Jared E. Lopes, Rachel L. Dusek, Liliane Robillard, Minh Nguyen, Bruce Roth, Bryan Vought, Arthur Liberzon, Raymond J. Winquist, Heather C. Losey. The combination of a mouse ortholog of ALKS 4230, a selective agonist of the intermediate affinity IL-2 receptor, and the angiogenesis inhibitor lucitanib enhances antitumor activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2202.

Abstract 2663: Characterization of the pharmacodynamic immune response to a novel immunotherapeutic agent, ALKS 4230, in mice and non-human primates

ALKS 4230 is a selective agonist of the intermediate-affinity IL-2 receptor (IL-2R). A phase 1 study is ongoing to evaluate the safety and tolerability of ALKS 4230 in the treatment of patients with refractory solid tumors. The selectivity of ALKS 4230 is achieved through the stable fusion of circularly permuted IL-2 to the extracellular portion of the IL-2Rα chain, CD25. The resulting fusion protein is sterically prevented from binding to the high-affinity IL-2R complex, comprised of IL-2Rα, IL-2Rβ, and common gamma chain, expressed preferentially on CD4+ FOXP3+ regulatory T cells (CD4+ Tregs) yet retains full ability to signal through the intermediate-affinity IL-2R complex, comprised of IL-2Rβ and common gamma chain, expressed on memory CD8+ T cells and NK cells. Repeated dosing of ALKS 4230 drives the significant expansion of various CD8+ T cell and NK cell populations without activation and minimal expansion of CD4+ Tregs in mice and non-human primates (NHP). The kinetics of the immunological responses in mice and NHP demonstrate that the pharmacodynamic effects persist beyond systemic exposure of ALKS 4230. Data demonstrating the effects of ALKS 4230 on tumor-infiltrating lymphocyte populations in syngeneic tumor models will also be presented.

Citation Format: Jared E. Lopes, Heather C. Losey, Reginald L. Dean, Heather L. Flick, Michael R. Huff, Rosemarie A. Moroso, Lei Sun, Juan C. Alvarez. Characterization of the pharmacodynamic immune response to a novel immunotherapeutic agent, ALKS 4230, in mice and non-human primates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2663. doi:10.1158/1538-7445.AM2017-2663

Abstract 3158: Ex vivo expansion and activation of human lymphocytes with a selective activator of effector cells

RDB 1450 is an engineered fusion protein of circularly permuted IL-2 and IL-2Rα that is selective for the intermediate-affinity IL-2 receptor. The intermediate-affinity receptor is comprised of the IL-2 receptor beta chain (CD122) and common gamma chain (CD132) expressed on lymphocytes with effector function, whereas the high-affinity receptor, which additionally includes the alpha chain (CD25), is expressed primarily on immunosuppressive CD4+CD25+ regulatory T cells (Tregs). Ex vivo proliferation of subsets of human lymphocytes in response to RDB 1450 or rhIL-2 were evaluated. RDB 1450 supports the selective activation and expansion of effector lymphocytes based on higher observed memory CD8 T/Treg and NK/Treg ratios. Both RDB 1450 and IL-2 drive expansion of NK cells, however, a greater proportion of CD25+ NK cells are observed in response to RDB 1450. Furthermore, unlike IL-2, RDB 1450 does not effectively expand highly suppressive ICOS+ Tregs.   The immunological profile resulting from the ex vivo treatment of human PBMCs with RDB 1450 supports its use as a novel immunotherapy for cancer.

Citation Format: Jared E. Lopes, Jan L. Fisher, Heather C. Losey, Marc S. Ernstoff, Juan C. Alvarez. Ex vivo expansion and activation of human lymphocytes with a selective activator of effector cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3158. doi:10.1158/1538-7445.AM2015-3158

Abstract 4280: Utilizing a selective agonist of the intermediate-affinity IL-2 receptor with an improved pharmacokinetic profile leads to an enhanced immunostimulatory response With reduced toxicity in mice

RDB 1450 is an engineered fusion protein which selectively activates the intermediate-affinity IL-2 receptor present on NK cells and memory CD8 T cells. In rodents, RDB 1450 has a half-life of 6-8 hours, compared to a half-life of minutes for recombinant human IL-2 (rhIL-2). Repeat daily dosing (QD) of RDB 1450 in mice results in marked expansion of NK cells and CD8+CD44high T cells, with minimal expansion of CD4+ regulatory T cells (Tregs). Higher QD doses elicit more pronounced effector cell expansion with modest pulmonary edema. TID delivery of the same total daily dose of RDB 1450 enhances the immunological responses in the absence of pulmonary edema. These results suggest that prolonged delivery of reduced concentrations of RDB 1450 drive the desired immune responses with improved tolerability. In contrast, high circulating concentrations of rhIL-2 are required to stimulate effector cells due to its preferential activation of Tregs at lower concentrations. The selectivity profile and favorable pharmacokinetics of RDB 1450 highlight its potential as a novel, differentiated immunotherapeutic agent for the treatment of cancer.

Citation Format: Heather C. Losey, Jared E. Lopes, Reginald L. Dean, Heather Flick, Madison Gomes, Michael R. Huff, Rosemarie A. Moroso, Lei Sun, Chunhua Wang, Julie F. Waters, Juan C. Alvarez. Utilizing a selective agonist of the intermediate-affinity IL-2 receptor with an improved pharmacokinetic profile leads to an enhanced immunostimulatory response With reduced toxicity in mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4280. doi:10.1158/1538-7445.AM2015-4280

Abstract 4281: Determination of the Relative Potency of a Selective Agonist of the Intermediate-Affinity IL-2 Receptor on Lymphocytes from Human, Cynomolgus Monkey and Mouse

RDB 1450 is an engineered fusion protein designed to selectively activate the intermediate-affinity IL-2 receptor versus the high-affinity IL-2 receptor. The potencies of RDB 1450 and IL-2 for activation of distinct subsets of effector and regulatory lymphocytes from murine, non-human primate and human donors were determined. Splenocytes isolated from mice or leukocytes isolated from human or cyno blood were stimulated with either RDB 1450 or IL-2. Multicolor flow cytometry was used to identify distinct subpopulations and the extent of phosphorylation of STAT5 was measured. Whereas IL-2 is 2-3 orders of magnitude more potent on immunosuppressive Tregs relative to NK cells and memory CD8 T cells, RDB 1450 induces activation of NK cells, memory CD8 T cells and Tregs at comparable concentrations within each species. The non-differentiated potency of RDB 1450 on the lymphocyte subpopulations examined suggests that its effects are mediated through the intermediate affinity receptors even on CD25-expressing Tregs. The preferential activation of Tregs by IL-2 may lead to immunosuppression and limit its antitumor efficacy. In contrast, RDB 1450 does not exhibit the same preference for Treg activation and is expected to be more effective in driving antitumor immune responses. These results highlight the differentiated immunological profile of RDB 1450 and support its potential as a novel human immunotherapy.

Citation Format: Emily E. Rosentrater, Heather Flick, Jared E. Lopes, Heather C. Losey, Chunhua Wang, Juan C. Alvarez. Determination of the Relative Potency of a Selective Agonist of the Intermediate-Affinity IL-2 Receptor on Lymphocytes from Human, Cynomolgus Monkey and Mouse. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4281. doi:10.1158/1538-7445.AM2015-4281

Foxp3 is required throughout the life of a regulatory T cell

The forkhead family transcription factor Foxp3 is critical for the development and function of CD4(+)CD25(+) regulatory T cells (Tregs). A series of reports have begun to shed light on the precise role of Foxp3 in the regulation of the Treg transcriptome. Foxp3 can bind to specific gene elements, thereby altering transcription of target genes directly, and Foxp3 can alter the expression of genes encoding other transcription factors, thereby having an indirect effect on the transcription of target genes. Cells retaining aspects of Treg differentiation persist in the absence of Foxp3, which is suggestive of a Foxp3-independent aspect of Treg biology.

Analysis of FOXP3 reveals multiple domains required for its function as a transcriptional repressor

Foxp3 has been shown to be both necessary and sufficient for the development and function of naturally arising CD4+ CD25+ regulatory T cells in mice. Mutation of Foxp3 in Scurfy mice and FOXP3 in humans with IPEX results in fatal, early onset autoimmune disease and demonstrates the critical role of FOXP3 in maintaining immune homeostasis. The FOXP3 protein encodes several functional domains, including a C2H2 zinc finger, a leucine zipper, and a winged-helix/forkhead (FKH) domain. We have shown previously that FOXP3 functions as a transcriptional repressor and inhibits activation-induced IL-2 gene transcription. To characterize the role of each predicted functional domain on the in vivo activity of FOXP3, we have evaluated the location of point mutations identified in a large cohort of patients with the immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) and found them to cluster primarily within the FKH domain and the leucine zipper, but also present within the poorly defined N-terminal portion of the protein. The molecular functions of each of the IPEX-targeted domains were investigated. We show that FOXP3 is constitutively localized to the nucleus and this localization requires sequences at both the amino and C-terminal ends of its FKH domain. Moreover, FOXP3 was found to homodimerize through its leucine zipper. We also identify a novel functional domain within the N-terminal half of FOXP3, which is required for FOXP3-mediated repression of transcription from both a constitutively active and a NF-AT-inducible promoter. Furthermore, we demonstrate that IPEX mutations in these domains correlate with deficiencies in FOXP3 repressor function, corroborating their in vivo relevance.

Insights into transcriptional regulation by FOXP3

FoxP3 recently entered the spotlight as a critical component of regulatory T cell development and function. Several groups are presently engaged in an effort to uncover the mechanistic details of its contribution to this critical T cell subset. Despite this, the mechanism of FoxP3-mediated transcriptional repression and the affected target genes are still largely unknown. First, we discuss insights from work on other Fox family members with an emphasis on those with known roles in the immune system. Second, we review recent data concerning the molecular mechanism of FoxP3 function and its role in human disease. Finally, we consider what is known about FoxP3 target genes and their effect on T cell physiology.

Characterization of flagellin expression and its role in Listeria monocytogenes infection and immunity

Flagellin is the structural component of flagella produced by many pathogenic bacteria and is a potent proinflammatory molecule that mediates these effects through Toll-like receptor (TLR) 5. In Listeria monocytogenes (LM), flagellin expression is regulated by temperature and has been described as being shut off at 37 degrees C. In this study, we demonstrate that TLR5-mediated cell activation and flagellin expression is maintained at 37 degrees C in some laboratory-adapted strains and in approximately 20% of LM clinical isolates. To determine the role of flagellin in LM infection, a targeted mutation in the structural gene for flagellin (flaA) was generated in a parental LM strain that expressed flagellin under all conditions examined. In vitro studies demonstrated that this deltaflaA mutant was (i). non-motile; (ii). not able to activate TLR5-transfected HeLa cells; and (iii). induced tumour necrosis factor (TNF)-alpha production in approximately 50% fewer CD11b+ cells in splenocytes from normal mice compared with the parental strain. However, there was no significant alteration in virulence of the deltaflaA mutant after either intravenous or oral murine infection. Similarly, there was no difference in the generation of LM-specific CD8 or CD4 T cells after intravenous or oral infection. These data indicate that flagellin is not essential for LM pathogenesis or for the induction of LM-specific adaptive immune responses in normal mice.

Comparison of simulated patient and didactic methods of teaching HIV risk assessment to medical residents

INTRODUCTION

Physicians need to be well trained in HIV risk assessment interview skills. Little has been written in the literature concerning training methods for this specialized interview.

METHODS

One model to teach the HIV risk assessment interview has been developed and has been used to teach third-year medical students. We compared this interactive model, which uses simulated patients to teach HIV Risk Assessment, to a didactic one. Twelve medical residents were taken through either the interactive session or the didactic session. Pre-post changes from questionnaires were calculated to determine any differences in sessions. Also, Objective Structured Clinical Examinations (OSCEs) were used to grade all residents 2 weeks after their sessions.

RESULTS

All pre-post changes were calculated and no statistically significant differences were seen (P > 0.50). OSCE interpersonal skills scores and content scores were calculated. The interactive group had statistically significantly higher scores (P < 0.05).

CONCLUSION

The data supports the conclusion that an interactive method is more effective to use to train HIV risk assessment interview skills to medical residents when compared to the didactic method.

[Hemangioma of Meckel's cavum: a case report]

A case of haemangioma of Meckel's cave is reported. The rarity of the lesion is focused, as well as its symptomatology and the radiologic changes.