PROTAC-mediated NR4A1 degradation as a novel strategy for cancer immunotherapy

An effective cancer therapy requires killing cancer cells and targeting the tumor microenvironment (TME). Searching for molecules critical for multiple cell types in the TME, we identified NR4A1 as one such molecule that can maintain the immune suppressive TME. Here, we establish NR4A1 as a valid target for cancer immunotherapy and describe a first-of-its-kind proteolysis-targeting chimera (PROTAC, named NR-V04) against NR4A1. NR-V04 degrades NR4A1 within hours in vitro and exhibits long-lasting NR4A1 degradation in tumors with an excellent safety profile. NR-V04 inhibits and frequently eradicates established tumors. At the mechanistic level, NR-V04 induces the tumor-infiltrating (TI) B cells and effector memory CD8+ T (Tem) cells and reduces monocytic myeloid-derived suppressor cells (m-MDSC), all of which are known to be clinically relevant immune cell populations in human melanomas. Overall, NR-V04-mediated NR4A1 degradation holds promise for enhancing anticancer immune responses and offers a new avenue for treating various types of cancers such as melanoma.

Inhibition of LILRB2 by a Novel Blocking Antibody Designed to Reprogram Immunosuppressive Macrophages to Drive T Cell Activation in Tumors

Tumor-associated macrophages (TAMs) play an important role in maintaining the immunosuppressive state of the tumor microenvironment (TME). High levels of CD163+ TAMs specifically are associated with poor prognosis in many solid tumor types. Targeting TAMs may represent a key approach in development of the next generation of cancer immune therapeutics. Members of the leukocyte immunoglobulin-like receptor B (LILRB) family, including LILRB2 (ILT4), are known to transmit inhibitory signals in macrophages and other myeloid cells. Leveraging bulk and single cell RNAseq datasets, as well as extensive immunophenotyping of human tumors, we found that LILRB2 is highly expressed on CD163+ CD11b+ cells in the TME and that LILRB2 expression correlates with CD163 expression across many tumor types. To target LILRB2, we have developed JTX-8064, a highly potent and selective antagonistic monoclonal antibody. JTX-8064 blocks LILRB2 binding to its cognate ligands, including classical and non-classical MHC molecules. In vitro, JTX-8064 drives the polarization of human macrophages and dendritic cells toward an immunostimulatory phenotype. As a result, human macrophages treated with a LILRB2 blocker are reprogrammed to increase the activation of autologous T cells in co-culture systems. Furthermore, JTX-8064 significantly potentiates the activity of anti-PD-1 in allogeneic mixed lymphocyte reaction. In a human tumor explant culture, pharmacodynamic activity of JTX-8064 was observed in monotherapy and in combination with anti-PD-1. Collectively, our work provides strong translational and pre-clinical rationale to target LILRB2 in cancer.

Differential expression of CCR8 in tumors versus normal tissue allows specific depletion of tumor-infiltrating T regulatory cells by GS-1811, a novel Fc-optimized anti-CCR8 antibody

The presence of T regulatory (Treg) cells in the tumor microenvironment is associated with poor prognosis and resistance to therapies aimed at reactivating anti-tumor immune responses. Therefore, depletion of tumor-infiltrating Tregs is a potential approach to overcome resistance to immunotherapy. However, identifying Treg-specific targets to drive such selective depletion is challenging. CCR8 has recently emerged as one of these potential targets. Here, we describe GS-1811, a novel therapeutic monoclonal antibody that specifically binds to human CCR8 and is designed to selectively deplete tumor-infiltrating Tregs. We validate previous findings showing restricted expression of CCR8 on tumor Tregs, and precisely quantify CCR8 receptor densities on tumor and normal tissue T cell subsets, demonstrating a window for selective depletion of Tregs in the tumor. Importantly, we show that GS-1811 depleting activity is limited to cells expressing CCR8 at levels comparable to tumor-infiltrating Tregs. Targeting CCR8 in mouse tumor models results in robust anti-tumor efficacy, which is dependent on Treg depleting activity, and synergizes with PD-1 inhibition to promote anti-tumor responses in PD-1 resistant models. Our data support clinical development of GS-1811 to target CCR8 in cancer and drive tumor Treg depletion in order to promote anti-tumor immunity.

Abstract 5007: Preclinical evaluation of JTX-8064, an anti-LILRB2 antagonist antibody, for reprogramming tumor-associated macrophages

Introduction: Jounce has generated cell type-specific gene signatures as a means of probing The Cancer Genome Atlas and other large datasets to identify targets that may be important immune checkpoints. Using a tumor-associated macrophage (TAM) gene signature, we have found a strong correlation and coherence between TAMs and LILRB2 (leukocyte immunoglobulin like receptor B2; ILT4) across multiple tumors types. LILRB2 is a myeloid cell surface receptor containing four extracellular immunoglobulin domains, a transmembrane domain, and three cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Ligation of LILRB2 on myeloid cells, via its endogenous ligands (classical MHC I molecules [e.g. HLA-A, HLA-B] and non-classical MHC I molecules [e.g. HLA-G]), provides a negative signal that inhibits stimulation of an immune response. HLA-G is recognized as an important immunosuppressive molecule playing a role in maternal-fetal tolerance and being overexpressed in cancer - often associated with advanced disease stage and poor prognosis. As tumor-associated macrophages are known to suppress the anti-cancer immune response, these findings provide rationale for targeting LILRB2.

Methods and Results: We have generated a panel of monoclonal antibodies that bind specifically to LILRB2, but not other LILR family members, and can block binding of LILRB2 to MHC I molecules (i.e. HLA-A and HLA-G). In vitro differentiated monocyte-derived macrophages (MDMs) cultured for 24h in the presence of anti-LILRB2 antibodies and lipopolysaccharide (LPS) show polarization toward a more inflammatory phenotype - secreting higher levels of TNF-α and IL-6 with decreased amounts of IL-10 and CCL2 as compared to an isotype control antibody. NanoString mRNA analysis revealed that, in the absence of LPS or any additional stimuli, MDMs cultured with anti-LILRB2 antibodies showed gene changes consistent with inflammatory or M1-like polarization of macrophages. Anti-LILRB2 antibodies were also evaluated in human tumor histoculture and induced pharmacodynamic responses consistent with macrophage and T cell activation in a variety of tumor types. While mice do not express LILRB2 specifically, they do express a LILRB-like molecule known as Pirb. Mice that are deficient in Pirb display resistance to mouse colon 38 (MC-38) tumor growth suggesting this pathway functions as immune checkpoint in cancer.

Conclusions: Based on these preclinical data, JTX-8064, a high affinity LILRB2-specific humanized antagonist monoclonal antibody, is being developed as an immunotherapeutic to reprogram suppressive macrophages within the tumor microenvironment.

Citation Format: Heather Cohen, Yasmin Hashambhoy-Ramsay, Lauren R. Pepper, Jeffrey Y. Smith, Margaret Willer, Kevin Guay, Vikki Spaulding, Kristin O'Malley, Monica Gostissa, Abha Dhaneshwar, Edward C. Stack, Alessandro Mora, Donald R. Shaffer. Preclinical evaluation of JTX-8064, an anti-LILRB2 antagonist antibody, for reprogramming tumor-associated macrophages [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 5007.

Abstract P2-11-07: Mutually exclusive expression pattern of the immune co-inhibitory molecules B7-H4 and PD-L1 in triple negative breast cancer

B7-H4 (VTCN1, B7x, B7S1) is a transmembrane protein belonging to the B7 family of costimulatory proteins and has been shown to inhibit T cell proliferation, cytokine secretion, and cytotoxic lymphocyte (CTL) induction. B7-H4 expressed on tumor cells or macrophages has been associated with poor prognosis and impaired T cell function in renal cell and ovarian cancers. Here we show B7-H4 is abundantly expressed in human breast cancer with triple negative breast cancer (TNBC) having the highest overall B7-H4 mRNA expression. We developed a specific and sensitive immunohistochemistry (IHC) assay for evaluation of B7-H4 protein and quantified B7-H4 expression in 156 breast tumor samples. Approximately 70% of the breast tumor samples had detectable B7-H4 expression whereas none of the normal or benign breast tissues stained positive for B7-H4. Multiplex IHC and flow cytometry studies showed that the majority of B7-H4 expression was restricted to the tumor epithelial cells, the CD45+ immune cells were negative for B7-H4 expression. Interestingly none of the TNBC samples that were positive for B7-H4 showed detectable expression of PD-L1 suggesting that B7-H4 and PD-L1 checkpoint proteins may act in a mutually exclusive manner.

To evaluate the role of B7-H4 on tumor immune evasion, we overexpressed murine or human B7-H4 on the mouse colon-26 (CT26) tumor cell line and injected these cells intravenously into Balb/c mice. By day 14 we observed significantly more tumors as well as larger percent tumor area in the lungs of mice given CT26 cells transduced with human or mouse B7-H4 as compared to vector control transduced cells. These data suggest B7-H4 expression in tumors can accelerate tumor growth in immune competent mice and that targeting B7-H4 may provide therapeutic benefit. Given the mutually exclusive expression patterns of B7-H4 and PD-L1 a B7-H4 targeting agent may provide particular benefit in those patients where current anti-PD-1/PD-L1 therapies are not effective.

Citation Format: Shaffer DR, Nagashima K, Cortez-Retamozo V, Feldman I, Smith J, Zafari M, Larson R, Mabry R, Novorantseva T, Briskin M, Sathyanaryananan S. Mutually exclusive expression pattern of the immune co-inhibitory molecules B7-H4 and PD-L1 in triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-11-07.

In vivo discovery of immunotherapy targets in the tumour microenvironment

Recent clinical trials showed that targeting of inhibitory receptors on T cells induces durable responses in a subset of cancer patients, despite advanced disease. However, the regulatory switches controlling T-cell function in immunosuppressive tumours are not well understood. Here we show that such inhibitory mechanisms can be systematically discovered in the tumour microenvironment. We devised an in vivo pooled short hairpin RNA (shRNA) screen in which shRNAs targeting negative regulators became highly enriched in murine tumours by releasing a block on T-cell proliferation upon tumour antigen recognition. Such shRNAs were identified by deep sequencing of the shRNA cassette from T cells infiltrating tumour or control tissues. One of the target genes was Ppp2r2d, a regulatory subunit of the PP2A phosphatase family. In tumours, Ppp2r2d knockdown inhibited T-cell apoptosis and enhanced T-cell proliferation as well as cytokine production. Key regulators of immune function can therefore be discovered in relevant tissue microenvironments.

TanCAR: A Novel Bispecific Chimeric Antigen Receptor for Cancer Immunotherapy

Targeted T cells are emerging as effective non-toxic therapies for cancer. Multiple elements, however, contribute to the overall pathogenesis of cancer through both distinct and redundant mechanisms. Hence, targeting multiple cancer-specific markers simultaneously could result in better therapeutic efficacy. We created a functional chimeric antigen receptor-the TanCAR, a novel artificial molecule that mediates bispecific activation and targeting of T cells. We demonstrate the feasibility of cumulative integration of structure and docking simulation data using computational tools to interrogate the design and predict the functionality of such a complex bispecific molecule. Our prototype TanCAR induced distinct T cell reactivity against each of two tumor restricted antigens, and produced synergistic enhancement of effector functions when both antigens were simultaneously encountered. Furthermore, the TanCAR preserved the cytolytic ability of T cells upon loss of one of the target molecules and better controlled established experimental tumors by recognition of both targets in an animal disease model. This proof-of-concept approach can be used to increase the specificity of effector cells for malignant versus normal target cells, to offset antigen escape or to allow for targeting the tumor and its microenvironment.Molecular Therapy-Nucleic Acids (2013) 2, e105; doi:10.1038/mtna.2013.32; published online 9 July 2013.

Antitumor effects of chimeric receptor engineered human T cells directed to tumor stroma

Cancer-associated fibroblasts (CAFs), the principle component of the tumor-associated stroma, form a highly protumorigenic and immunosuppressive microenvironment that mediates therapeutic resistance. Co-targeting CAFs in addition to cancer cells may therefore augment the antitumor response. Fibroblast activation protein-α (FAP), a type 2 dipeptidyl peptidase, is expressed on CAFs in a majority of solid tumors making it an attractive immunotherapeutic target. To target FAP-positive CAFs in the tumor-associated stroma, we genetically modified T cells to express a FAP-specific chimeric antigen receptor (CAR). The resulting FAP-specific T cells recognized and killed FAP-positive target cells as determined by proinflammatory cytokine release and target cell lysis. In an established A549 lung cancer model, adoptive transfer of FAP-specific T cells significantly reduced FAP-positive stromal cells, with a concomitant decrease in tumor growth. Combining these FAP-specific T cells with T cells that targeted the EphA2 antigen on the A549 cancer cells themselves significantly enhanced overall antitumor activity and conferred a survival advantage compared to either alone. Our study underscores the value of co-targeting both CAFs and cancer cells to increase the benefits of T-cell immunotherapy for solid tumors.

Aggressive peripheral CD70-positive T-cell lymphoma associated with severe chronic active EBV infection

Severe chronic active Epstein-Barr virus infection (CAEBV) in T or NK cells is a rare complication of latent EBV infection. CAEBV associated T-cell lymphoproliferative disease (LPD) consists of polyclonal lesions as well as aggressive lymphomas. Here, we report such a patient. In addition, we show that this primary CAEBV associated T-cell lymphoma expresses CD70 and is sensitive to killing by CD70-specific T cells, identifying CD70 as a potential immunotherapeutic target for CAEBV-associated T-cell lymphoma.

Crosstalk between medulloblastoma cells and endothelium triggers a strong chemotactic signal recruiting T lymphocytes to the tumor microenvironment

Cancer cells can live and grow if they succeed in creating a favorable niche that often includes elements from the immune system. While T lymphocytes play an important role in the host response to tumor growth, the mechanism of their trafficking to the tumor remains poorly understood. We show here that T lymphocytes consistently infiltrate the primary brain cancer, medulloblastoma. We demonstrate, both in vitro and in vivo, that these T lymphocytes are attracted to tumor deposits only after the tumor cells have interacted with tumor vascular endothelium. Macrophage Migration Inhibitory Factor (MIF)" is the key chemokine molecule secreted by tumor cells which induces the tumor vascular endothelial cells to secrete the potent T lymphocyte attractant "Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES)." This in turn creates a chemotactic gradient for RANTES-receptor bearing T lymphocytes. Manipulation of this pathway could have important therapeutic implications.

Expansion of T cells targeting multiple antigens of cytomegalovirus, Epstein-Barr virus and adenovirus to provide broad antiviral specificity after stem cell transplantation

BACKGROUND AIMS

Hematopoietic stem cell transplant (HSCT) is the treatment of choice for a proportion of patients with hematologic malignancies as well as for non-malignant diseases. However, viral infections, particularly Epstein-Barr virus (EBV), cytomegalovirus (CMV) and adenovirus (Ad), remain problematic after transplant despite the use of antiviral drugs. We have shown that cytotoxic T lymphocytes (CTL) generated against CMV-pp65, EBV and Ad antigens in a single culture are capable of controlling infections with all three viruses after HSCT. Although pp65-specific CTL have proved efficacious for the control of CMV infection, several reports highlight the importance of targeting additional CMV antigens.

METHODS

To expand multivirus-specific T cells with activity against both CMV-pp65 and CMV-IE-1, peripheral blood mononuclear cells (PBMC) were transduced with the adenoviral vector (Ad5f35-IE-1-I-pp65). After 9-12 days the CTL were restimulated with autologous EBV-transformed B cells transduced with the same Ad vector.

RESULTS

After 18 days in culture nine CTL lines expanded from less than 1.5 × 10(7) PBMC to a mean of 6.1 × 10(7) T cells that recognized CMV antigens pp65 [median 273 spot-forming cells (SFC), range 47-995] and IE-1 (median 154 SFC, range 11-505), the Ad antigens hexon (median 153 SFC, range 26-465) and penton (median 37 SFC, range 1-353), as well as EBV lymphoblastoid cell lines (median 55 SFC, range 9-301). Importantly, the T cells recognized at least two antigens per virus and lysed virus peptide-pulsed targets.

CONCLUSIONS

CTL that target at least two antigens each of CMV, EBV and Ad should have clinical benefit with broad coverage of all three viruses and enhanced control of CMV infections compared with current protocols.

Immunotherapeutic options for Epstein-Barr virus-associated lymphoproliferative disease following transplantation

Epstein-Barr virus-associated lymphoproliferative diseases (EBV-LPD) after hematopoietic stem cell transplantation or solid-organ transplantation remain a serious and potentially life-threatening complication. In the last decade, outcomes for EBV-LPD have significantly improved. Key to this success was the development of early detection methods, such as serial measurements of EBV-DNA load in the peripheral blood of transplant recipients. Immunotherapeutic interventions for EBV-LPD include reduction of immunosuppression, CD20 monoclonal antibodies (rituximab) as monotherapy or in conjunction with chemotherapy, and adoptive immunotherapy with EBV-specific T cells. Pre-emptive immunotherapeutic interventions can prevent the development of EBV-LPD. As monotherapy, immunotherapy is effective in inducing remissions of EBV-LPD with low-risk features. For high-risk disease, combining immunotherapy with conventional therapies has led to superior outcomes. Current challenges consist of risk stratifying patients so that patients receive the most efficacious therapy without suffering from unwanted side effects.

ADAM12 is highly expressed in carcinoma-associated stroma and is required for mouse prostate tumor progression

The interaction between stromal cells and tumor cells is emerging as a critical aspect of tumor progression. Yet there is a paucity of molecular markers for cells participating in such interactions, and only few genes are known to play a critical role in this process. Here, we describe the identification of ADAM12 (a disintegrin and metalloprotease 12) as a novel marker for a subpopulation of stromal cells that are adjacent to epithelial tumor cells in three mouse carcinoma models (models for prostate, breast and colon cancer). Moreover, we show that ADAM12 is essential for tumor development and progression in the W10 mouse model for prostate cancer. These results suggest that ADAM12 might be a useful marker for stromal cells in mouse tumors that are likely to participate in stromal/tumor cell crosstalk, and that ADAM12 is a potential target for design of drugs that prevent carcinoma growth.

Relationship quality and potentially harmful behaviors by spousal caregivers: how we were then, how we are now. The Family Relationships in Late Life Project

Structured interview data from 142 caregivers (98 wives, 44 husbands) indicate that more depressed caregivers are more likely to treat their spouses in potentially harmful ways. However, consistent with hypotheses derived from communal relationships theory, when the preillness relationship between caregiver and care recipient was characterized by mutual responsiveness to each other's needs (i.e., was more communal), caregivers were less depressed and less frequently engaged in potentially harmful behaviors. These effects were not attributable to demographic factors, amount of care provided, care recipient dementia status, or length of time in the caregiving role. Rather, multivariate analyses suggest that the extent to which premorbid relationships were communal in nature determines whether caregivers perceive their current relationships as rewarding, which, in turn, predicts caregiver depression and potentially harmful behaviors.

On finding for defendants who plead insanity: the crucial impact of dispositional instructions and opportunity to deliberate

One hundred twenty participants functioned as mock-jurors and as members of deliberating juries in an experiment designed to assess the impact of dispositional instruction on verdicts rendered in an insanity trial. Consistent with prior research (K. E. Whittemore & J. R. Ogloff, 1995), dispositional instruction had no effect on the verdict preferences of individual jurors prior to deliberating. Yet, as expected, the instruction manipulation had a major impact on postdeliberative decisions (i.e., group verdicts; individual juror verdict preferences). Content analyses of jury deliberations revealed that postdeliberative shifts toward harsh verdicts in uninstructed juries and toward lenient verdicts in instructed juries were mediated by the impact of the Instruction manipulation on the content of jury deliberations: uninstructed juries feared that an acquitted-insane defendant would be freed to act again, whereas instructed juries recognized that finding for an insane defendant implied his retention and treatment. Implications of these results for both legal policy and the conduct of mock-trial research are discussed.

Activity restriction and prior relationship history as contributors to mental health outcomes among middle-aged and older spousal caregivers

In a sample of cancer patients (n = 75) and spousal caregivers (24 men and 51 women), restriction in caregiver routine activities mediated associations between caregiving stress (patient symptom severity) and caregiver depressed affect and resentment. Moreover, the antecedents and affective consequences of caregiver activity restriction were consistent with the theory of communal relationships (e.g., M. S. Clark & J. Mills, 1979, 1993). If a relationship had been communal in the past (i.e., characterized by mutual concern for and responsiveness to one another's needs), activity restriction was predicted by intimacy and affectional loss (rather than by the severity of patient symptoms) and in turn predicted caregiver depressed affect. Among caregivers in less communal relationships, activity restriction was predicted by severity of patient symptoms (rather than by intimacy and affectional loss) and in turn predicted resentment of care recipients and the caregiving role.

Gender and situational context moderate the relationship between self-monitoring and induction of self-disclosure

Male and female undergraduates who differed in degree of self-monitoring interviewed same-sex strangers to test the hypothesis that interviewer self-monitoring propensities foster self-disclosure only in disclosure-conducive contexts (i.e., collaborative contexts for men and social-expressive contexts for women). Results indicated that high self-monitoring (but not low self-monitoring) interviewers of each gender were notably more successful at eliciting personal information in the contexts generally considered amenable to male and female self-disclosure than in disclosure-nonconducive contexts. Moreover, male high self-monitoring interviewers reliably elicited more information than their low self-monitoring counterparts only in the disclosure-conducive (for men) collaborative context. However, high self-monitoring female interviewers did not elicit more information than their dispositional counterparts in disclosure-conducive, social-expressive contexts, although they reliably induced less disclosure than low self-monitors in the disclosure-nonconducive (for women) collaborative context.

Activity restriction and prior relationship history as contributors to mental health outcomes among middle-aged and older spousal caregivers

In a sample of cancer patients (n = 75) and spousal caregivers (24 men and 51 women), restriction in caregiver routine activities mediated associations between caregiving stress (patient symptom severity) and caregiver depressed affect and resentment. Moreover, the antecedents and affective consequences of caregiver activity restriction were consistent with the theory of communal relationships (e.g., M. S. Clark & J. Mills, 1979, 1993). If a relationship had been communal in the past (i.e., characterized by mutual concern for and responsiveness to one another's needs), activity restriction was predicted by intimacy and affectional loss (rather than by the severity of patient symptoms) and in turn predicted caregiver depressed affect. Among caregivers in less communal relationships, activity restriction was predicted by severity of patient symptoms (rather than by intimacy and affectional loss) and in turn predicted resentment of care recipients and the caregiving role.

Temperature-sensitive hepatitis A virus mutants with deletions downstream of the first pyrimidine-rich tract of the 5' nontranslated RNA are impaired in RNA synthesis

Hepatitis A virus (HAV) mutants containing large deletions within the first pyrimidine-rich tract (pY1; nucleotides [nt] 99 to 138) of the 5' nontranslated RNA (5'NTR) replicate well in cultured cells, while those with pY1 deletions which extend in a 3' direction to include nt 140 to 144 (CUUGU) have a temperature-sensitive (ts) replication phenotype (D.R. Shaffer, E.A. Brown, and S.M. Lemon, J. Virol. 68:5568-5578, 1994). To characterize this replication defect, the ts mutant delta 131-144 was grown under one-step conditions at the nonpermissive temperature (37 degrees C). A shift to the permissive temperature (31 degrees C) for the first 18 h of the viral replication cycle did not enhance virus yields, indicating that temperature sensitivity is not due to a defect in viral entry or uncoating. Similarly, absence of increased yield with a late shift to 31 degrees C between 54 and 72 h suggested that the ts defect does not involve viral assembly. Although monocistronic RNA transcripts containing the delta 99-144 deletion directed translation 22 to 58% less efficiently than the standard 5'NTR in transfected BS-C-1 cells, this difference was present at both 31 and 37 degrees C. In addition, there were no temperature-dependent differences in the abilities of bicistronic transcripts containing either ts or non-ts 5'NTR sequences within the intercistronic space to direct translation of a downstream reporter gene. Thus, ts mutations do not confer a demonstrable temperature-related defect in cap-independent translation. In contrast, an RNase protection assay showed that synthesis of viral plus-strand RNA was markedly delayed in BS-C-1 cells infected with ts virus at 37 degrees C. Analysis of the nucleotide sequence surrounding the deletion in a non-ts revertant derived from delta 116-144 virus revealed that a single U-to-G transversion at nt 114 (CUUUU-->CUUGU) had restored the sequence normally present between nt 140 and 144. These results indicate that ts mutants of HAV with deletions extending downstream from the pY1 domain to nt 140 to 144 are defective in RNA synthesis and that the single-stranded RNA segment containing nt 140 to 144 plays a critical role in replication of HAV RNA.

A hepatitis A virus deletion mutant which lacks the first pyrimidine-rich tract of the 5' nontranslated RNA remains virulent in primates after direct intrahepatic nucleic acid transfection

Cell culture-adapted variants of hepatitis A virus (HAV) in which the first pyrimidine-rich tract (pY1; nucleotides 99 to 138) of the 5' nontranslated region has been deleted (delta 96-137 or delta 96-139) replicate as well as parental virus in cultured cells (D.R. Shaffer, E.A. Brown, and S.M. Lemon, J. Virol. 68:5568-5578, 1994). To determine whether viruses with such large deletion mutations are able to replicate and to produce acute hepatitis in primates, we reconstructed the delta 96-137 deletion in the genetic background of a virulent virus which differs from the wild type by only one mutation in the 2B-coding region (HM175/8Y). Full-length synthetic delta 96-137/8Y RNA was injected into the livers of two HAV-seronegative marmosets (Saguinus mystax). Both animals developed serum liver enzyme elevations and inflammatory changes in serial liver biopsies within 3 to 4 weeks of inoculation which were comparable in magnitude to those observed previously following intrahepatic inoculation of marmosets with HM175/8Y RNA. Sequencing of RNA from virus shed in feces demonstrated the presence of the delta 96-137 deletion. These results indicate that the pY1 sequence of HAV is not required for efficient viral replication in hepatocytes in situ or for production of acute hepatic injury following intrahepatic RNA transfection in primates.

Large deletion mutations involving the first pyrimidine-rich tract of the 5' nontranslated RNA of human hepatitis A virus define two adjacent domains associated with distinct replication phenotypes

The 5' nontranslated RNA (5'NTR) of the HM175 strain of human hepatitis A virus contains several pyrimidine-rich regions, the largest and most 5' of which (pY1) is an almost pure polypyrimidine tract located between nucleotides (nt) 99 and 138, which includes five tandem repeats of the sequence motif (U)UUCC(C). Previous modeling of the RNA secondary structure suggested that this region was likely to be single-stranded, but repetitive RNase V1 cleavage sites within these (U)UUCC(C) motifs indicated that pY1 possesses an ordered structure. To assess the role of this domain in replication of the virus, a series of large deletion mutations were created which involved the pY1 domain of an infectious cDNA clone. Deletion of 44 nt between nt 96 and 139, including the entire pY1 domain, did not reduce the capacity of the virus to replicate in BS-C-1 or FRhK-4 cells, as assessed by the size of replication foci in radioimmunofocus assays or by virus yields under one-step growth conditions. In contrast, viable virus could not be recovered from transfected RNAs in which the deletion was extended in a 5' direction by an additional 3 nt (delta 93-134), most likely because of the destabilization of a predicted stem-loop structure upstream of pY1. Deletion mutations extending in a 3' fashion to nt 140, 141, or 144 resulted in moderately (delta 96-140 and delta 96-141) or strongly (delta 99-144, delta 116-144, and delta 131-144) temperature-sensitive replication phenotypes. Although deletion of the pY1 domain did not by itself affect the replication phenotype of virus, the additional deletion of sequence elements within the pY1 domain (nt 99 to 130) substantially enhanced the temperature-sensitive phenotype of delta 131-144 virus. These data suggest that the (U)UUCC(C) motifs within the pY1 domain are conserved among wild-type viruses in order to serve a function required during infection in vivo but not in cell culture. In contrast, the single-stranded region located immediately downstream of pY1 (nt 140 to 144) is essential for efficient replication in cultured cells at physiological temperature. Viruses with deletion mutations involving nt 140 to 144 and viruses with large pY1 deletions but normal replication phenotypes in cell culture may have attenuation properties which could be exploited for vaccine development.

Gender and self-disclosure revisited: personal and contextual variations in self-disclosure to same-sex acquaintances

Male and female American students who differed in masculinity and in femininity self-disclosed to a same-sex stranger in contexts that made either social/expressive motives or instrumental motives salient. The results were consistent with the primary assertion that measures of sex role identity are better predictors of contextual variations in self-disclosure than is sex per se. Sex consistently failed to predict subjects' willingness to self-disclose, both within and across contexts, whereas femininity promoted self-disclosure in the context that was clearly social and expressive in character. Although masculinity failed to exert the expected facilitative impact on self-disclosure within the instrumental context, it nonetheless influenced the results; androgynous subjects, who scored high in both masculinity and femininity, were more self-revealing across contexts than was any other group.

Interaction of low density lipoproteins with human aortic elastin

Interaction between lipoproteins and elastin in the arterial wall may play an important role in atherosclerotic lipid deposition, but binding affinities and other characteristics of the interaction have not been determined previously. Elastin was isolated by hot alkali treatment of human aortic tissue. At 4 degrees C, radioiodinated human low density lipoprotein (LDL) bound to more than one class of binding sites on elastin. Sites of highest affinity had an apparent dissociation constant of 3.6 x 10(-8) M. Total binding at an LDL concentration of 50 micrograms/ml ranged from 4 to 50 ng LDL protein/mg elastin. The binding was relatively specific, since binding was competitively inhibited by LDL and apo E-containing high density lipoprotein (HDL) but only modestly by HDL3. Atherosclerotic elastin exhibited a twofold to fourfold higher capacity for binding LDL, but a reduced affinity. At 37 degrees C, normal elastin exhibited an initial rapid binding of LDL, with a slower linear phase of binding over a 15-hour period, indicating an additional complex process at this temperature. Consideration of the expected LDL concentrations in the arterial intima, in comparison with binding affinities, suggests that LDL binding to elastin probably occurs in the intima and may foster atherosclerotic lipid deposition.

Stress fibers in endothelial cells overlying atherosclerotic lesions in rabbit aorta

Endothelial injury or dysfunction has long been postulated to promote atherogenesis, but structural alterations of endothelium in atherosclerosis have remained obscure. We report the common occurrence of actin-containing stress fibers, stainable by rhodamine-phalloidin, in endothelium overlying atherosclerotic lesions in cholesterol-fed rabbits. Nonlesioned areas in the same aortas showed normal endothelium with minimal development of stress fibers, which was no different from the appearance of endothelium in chow-fed rabbits. Microtubule organization revealed by immunofluorescence appeared normal in all areas. The development of stress fibers may be related to an altered substratum for endothelial attachment. This study provided no evidence to relate stress fiber formation with lesion initiation, but an association with well-developed foam cell lesions was evident.