Abstract P5-11-12: Longitudinal changes in volumetric breast density and fibroglandular volume with endocrine therapy in African American women with estrogen receptor positive breast cancer

Background and Aim:

Reduction in breast density has been proposed as a biomarker of response to endocrine therapy (ET). The vast majority of current data are derived from white or Asian women. Because baseline breast density is associated with race, it is possible that changes in breast density with treatment may also be affected by race. Our objective was to assess the impact of ET on volumetric breast density (VBD) and fibroglandular volume (FGV) in African American (AA) women with invasive breast cancer.

Methods:

We conducted a retrospective study of AA women diagnosed with estrogen receptor positive invasive breast cancer at our institution from 2009-2013. Mammograms within two years prior to diagnosis and at least 6 months post-diagnosis were utilized for comparing density measurements. Using Volpara automated software, VBD and FGV were measured for the contralateral normal breast by averaging the respective values measured on the craniocaudal and mediolateral oblique views.

Results:

51 women met the inclusion criteria and were confirmed to have received ET. Sixteen women received tamoxifen, 34 received an aromatase inhibitor, and medication data was unavailable in one case. The mean age at diagnosis was 56 years (range 29-72, median 55). 53% of women had stage I disease, 29% had stage II disease, and 18% had stage III disease. The majority of women had ER+ PR+ HER2 - disease (82.4%). 53.0% of women received systemic chemotherapy and all but one woman were treated surgically. Average body mass index (BMI) at diagnosis was 36.5, with data not available for 22 women. The mean time between diagnosis and baseline mammogram was 32 days, and the mean time between follow-up mammogram and baseline mammogram was 401 days. Average BMI at one year follow up was 33.7, with data not available for 19 women. The mean baseline VBD was 7.5% (range 1.9-21.5%, median 6.3%) and the mean follow-up VBD was 6.9% (range 2.0-23.6%, median 5.6%). Fifteen women had a longitudinal increase in VBD. The mean absolute change in VBD was -0.6% (range -3.4% to +9.8%, median 0.7%), with a mean 8.0 percent decrease from baseline to follow-up (range -0.7 to +0.5, median 0.1). The mean baseline FGV was 72.3 cm3 (range 18.5-208.4, median 65.3) and the mean follow-up FGV was 69.7 cm3 (range 22.7-197.5, median 60.5). Nineteen women had a longitudinal increase in FGV. The mean absolute reduction in FGV was 2.6 cm3 (range -53.3 to 49.3, median 4.8), with a mean 0.9 percent decrease from baseline to follow-up (range -111.6 to +53.0, median 5.2).

Conclusions:

We observed an overall decrease in Volpara-calculated VBD and FGV in our cohort of AA women treated with ET. It remains to be determined whether changes in VBD and FGV across serial mammograms may be a biomarker for response to ET in women of all races. Large prospective studies are needed to evaluate the effects of ET on longitudinal changes in VBD and FGV while controlling for confounders such as menopausal status, BMI, and chemotherapy.

Citation Format: Johnson HM, Shivalingappa H, Wong JH, Muzaffar M, Verbanac K, Vohra NA. Longitudinal changes in volumetric breast density and fibroglandular volume with endocrine therapy in African American women with estrogen receptor positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-11-12.

Abstract P6-08-21: Early breast cancer-specific mortality in women with early stage breast cancer: Epidemiological and clinical characteristics

Background and Aim:

The five-year survival for women with stage I-II breast cancer is 93-100%. Despite standard of care treatment, a small subset of these women suffer early breast cancer-specific mortality and die within 12 months of diagnosis. This subset of women has not been previously described. The aim of this study is to characterize the incidence, demographics, and clinical characteristics of women with early stage breast cancer who suffer early breast cancer-specific mortality.

Methods:

Retrospective population study of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registry of women diagnosed with stage I, IIA, or IIB breast cancer between 2004 and 2010. Data were filtered to histology codes 8500-8543 and 8575. Patient demographics (age, race, ethnicity) and clinical characteristics (stage, T stage, N stage, grade, ER status, PR status) of women in the early mortality subset were compared with those of women who survived > 12 months via the Chi-square test and the student t-test.

Results:

259,380 women formed the basis of our analysis. 4,572 women (0.018%) died within 12 months of diagnosis. Compared with those who survived > 12 months, women who suffered early breast cancer-specific mortality were on average older (mean age 65.7 years versus 60.3 years, p<0.00001) and more likely to be Hispanic (14.3% versus 8.9%, p<0.00001) or black (11.0% versus 9.1%, p<0.00001). Clinical characteristics associated with early mortality included higher stage (stage IIA 34.2% versus 29.4%, stage IIB 21.8% versus 12.9%, p<0.00001), higher T stage (T2 40.5% versus 28.1%, T3 3.1% versus 1.6%, p<0.00001), higher N stage (N1 29.7% versus 23.2%, N2 0.8% versus 0.4%, N3 0.4% versus 0.1%, p<0.00001), higher grade (moderate 39.3% versus 42.5%, high 40.0% versus 31.5%, p<0.00001), higher rates of ER negativity (27.2% versus 19.0%, p<0.00001), and higher rates of PR negativity (38.5% versus 30.2%, p<0.00001).

Conclusions:

Breast cancer-specific mortality within 12 months of diagnosis of stage I-II breast cancer is a rare phenomenon which has not been previously characterized. There are several demographic and clinical features associated with early mortality, however further research is needed to identify specific prognostic factors that will allow identification of women at risk for early mortality at the time of diagnosis.

Citation Format: Johnson HM, Wong JH, Vohra NA, Muzaffar M. Early breast cancer-specific mortality in women with early stage breast cancer: Epidemiological and clinical characteristics [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-21.

Superantigens: The Good, the Bad, and the Ugly

Increasing evidence suggests that superantigens play a role in Immune-mediated diseases. Superantigens are potent activators of CD4* T cells, causing rapid and massive proliferation of cells and cytokine production. This characteristic of superantigens can be exploited in diseases where strong immunologic responses are required, such as in the B16F10 animal model of melanoma. Superantigen administration is able to significantly enhance Ineffective anti-tumor Immune responses, resulting in potent and long-lived protective anti-tumor immunity. However, superantigens are more well-known for the role they play in diseases. Studies using an animal model for neurologic demy-elinatlng diseases such as multiple sclerosis show that superantigens can induce severe relapses and activate auto-reactive T cells not involved in the Initial bout of disease. This may also involve epitope spreading of disease. Superantigens have also been implicated in acute diseases such as food poisoning and TSS, and in chronic diseases such as psoriasis and rheumatoid arthritis. Viral superantigens are also involved in the disease process, including superantigens derived from human Immunodeficiency virus and mouse mammary tumor virus. Finally, immunotherapies that ameliorate the role played by superantigens in disease are discussed.

Interferon-tau: prospects for clinical use in autoimmune disorders

Interferon-tau (IFN-tau) is a type I IFN originally discovered for its role as a pregnancy recognition hormone in ruminant animals such as sheep and cows. IFN-tau possesses all of the biological properties ascribed to the other type I IFNs including antiviral, antiproliferative and immunomodulatory activities. However, IFN-tau differs in that it is relatively nontoxic to cells at high concentrations as compared to the toxicity normally associated with IFNs-alpha and -beta and the type II IFN, IFN-gamma. IFN-tau was examined for its ability to prevent the development of experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), in humans. IFN-tau prevents development of EAE as effectively as IFN-beta, a type I IFN currently being used for the treatment of MS. Unlike IFN-beta, however, IFN-tau treated mice did not develop leucopenia or experience bodyweight loss indicative of toxicity. Superantigens can induce relapses in EAE, similar to those that are observed in patients with relapsing-remitting MS; IFN-tau blocks superantigen reactivation of EAE. The inhibitory effect of IFN-tau on induction of EAE and reactivation by superantigen involves suppression of myelin basic protein and superantigen activation of T cells as well as suppressed induction of inflammatory cytokines such as tumour necrosis factor-alpha. In addition, IFN-tau has been shown to reduce immunologically mediated spontaneous fetal resorption. Thus, IFN-tau has considerable potential for treatment of autoimmune and immunologically mediated disorders, including MS.

The acceptability of an information leaflet explaining cardiopulmonary resuscitation policy in the hospice setting: a qualitative study exploring patients' views

BACKGROUND

Guidelines advise that patients receiving palliative care should be given realistic information about cardiopulmonary resuscitation (CPR) and encouraged to participate in decisions about this. For many patients attending a hospice, CPR is unlikely to be successful because of advanced disease. It is difficult to predict which patients would like to discuss CPR and whether such discussion might cause distress.

AIM

This research set out to determine the acceptability and understanding of a patient information leaflet about CPR given to inpatients and day-unit patients in one hospice, and to seek patients' views on communication about resuscitation.

METHODS

Semi-structured interviews were carried out with five hospice inpatients and one day-unit patient and analysed using interpretative phenomenological analysis for emergent themes.

RESULTS AND CONCLUSIONS

The leaflet was acceptable to the participants but was interpreted in the context of their understanding of their illness and prognosis. The leaflet alone is not a reliable method of communicating resuscitation policy and should be followed up by the opportunity to ask questions, if the patient wishes. Many factors influence patient choices about CPR. Realistic information about prognosis and about the risks and harms of CPR would allow patients to make a better-informed decision. However, if a patient prefers not to talk about their prognosis and end-of-life issues, then this should be respected.

Gamma interferon signaling: insights to development of interferon mimetics

We have developed small peptide mimetics of gamma interferon (IFNgamma), based not on the classical model of IFNgamma initiated signaling by extracellular interaction, but rather on direct intracellular signaling by IFNgamma. IFNgamma, its receptor subunit IFNGR1, and transcription factor STAT1alpha are transported to the nucleus of cells as a complex where IFNgamma provides a classical polycationic nuclear localization sequence (NLS) for such transport. The C terminus of IFNgamma, represented here by the mouse IFNgamma peptide, IFNgamma(95-132), was capable of also forming a complex with IFNGR1 and STAT1alpha when introduced intracellularly and provided the NLS signaling for nuclear transport. Importantly, mouse IFNgamma(95-132) and human IFNgamma(95-134) mimetics both induced an antiviral state and upregulation of MHC class II molecules in cells similar to that of full length IFNgamma. Both IFNgamma and its peptide mimetics bind to an intracellular site, IFNGR1(253-287), on the cytoplasmic domain of receptor subunit IFNGR1. This binding plays a role in tyrosine phosphorylation events, catalyzed by JAK1 and JAK2 kinases that result in the phosphorylation and binding of STAT1alpha to the cytoplasmic domain of IFNGR1. Important structural requirements for IFNgamma mimetic activity are a polycationic NLS and an alpha helix in the mimetics. Finally, chromatin immunoprecipitations and reporter gene studies of IFNgamma and IFNgamma mimetic treated cells indicate that they, along with IFNGR1 and STAT1alpha, bind to the GAS element of IFNgamma activated genes and participate in STAT1alpha transcription. It is important to note that IFNgamma intracellular events played the key role in development of IFNgamma mimetics.

Superantigen enhanced protection against a weak tumor-specific melanoma antigen: implications for prophylactic vaccination against cancer

B16F10 melanoma is a tumor derived from C57BL/6 mice that has been found to be poorly immunogenic and highly aggressive. Here we have shown that vaccination of mice with irradiated B16F10 cells followed by treatment with a combination of staphylococcal enterotoxins A and B (SEA/SEB) leads to significant and specific protection against subsequent challenge with viable B16F10 cells (at least 25-fold greater than a lethal dose). Also, 75% of mice surviving over 150 days remained tumor-free after rechallenge with viable B16F10 cells, evidence of the development of strong immunologic memory. Additional studies showed increases in CD4(+) and CD8(+) T-cell populations, cytotoxic T-lymphocyte activity and interferon-gamma production, all of which may contribute to enhanced survival. Furthermore, failure to produce protection in either CD4(-/-) or CD8(-/-) T-cell knockout mice is evidence that CD4(+) and CD8(+) T cells play an essential role in induction of immunity. These results show that superantigen administration subsequent to vaccination with inactivated tumor cells results in protective antitumor immunity. Thus, prophylactic vaccination against cancer is a feasible method for arming the immune system prior to the incidence of cancer.

Nuclear translocation of IFN-gamma is an intrinsic requirement for its biologic activity and can be driven by a heterologous nuclear localization sequence

We have previously identified a nuclear localization sequence (NLS) in interferon-gamma (IFN-gamma). This NLS functions intracellularly by forming a complex with its transcription factor Stat1alpha and the nuclear importer of Stat1alpha, the importin-alpha analog NPI-1. The stability of this complex and the subsequent nuclear translocation of the complexed Stat1alpha are dependent on the integrity of this NLS, showing that Stat1alpha nuclear import is mediated by the IFN-gamma NLS. In this study, to directly evaluate the intrinsic requirement of nuclear IFN-gamma toward its biologic activities, we engineered a chimeric in which the IFN-gamma NLS has been substituted by a heterologous NLS, namely, the prototypical NLS of the SV40 large T antigen, which would drive nuclear translocation of IFN-gamma in a sequence-nonspecific manner. The chimeric, IFN-gamma-SV, was equally active in antiviral and antiproliferative assays as the wild-type IFN-gamma. Interestingly, IFN-gamma-SV was also translocated to the nucleus and was also recovered intracellularly as a complex with the Stat1alpha importer NPI-1, like wild-type IFN-gamma. Comparison with an NLS deletion mutant showed that deletion or changes within the NLS motif of IFN-gamma were inconsequential to the high-affinity extracellular binding to the IFN-gamma receptor complex, yet the presence of an NLS was critical to the expression of the biologic activities of IFN-gamma and its NPI-1 complexation ability. Our data conclusively demonstrate that nuclear translocation of IFN-gamma is an intrinsic requirement for the full expression of the biologic activities of IFN-gamma and strengthen the conclusion that nuclear chaperoning of Stat1alpha is the primary role of IFN-gamma nuclear translocation. This type of ligand imprinting by sequestering of activated Stat may contribute to the specificity of Stat nuclear transcription.

Differential properties of two putative nuclear localization sequences found in the carboxyl-terminus of human ifn-gamma

Interferon-gamma (IFN-gamma), a protein that uses the Jak-Stat pathway for signal transduction, translocates rapidly to the nucleus in cells treated extracellularly with the cytokine. A nuclear localization sequence (NLS) has been identified and characterized in the C-terminus of IFN-gamma. Both human and murine IFN-gamma contain this NLS. We show in this report that human IFN-gamma (HuIFN-gamma) contains a second NLS at an upstream site, as determined in standard import assays using digitonin-permeabilized HeLa cells. The primary sequence, analogous with the NLS sequence identified in murine IFN-gamma, representing amino acids 122-132 of HuIFN-gamma was capable of mediating the nuclear import of the autofluorescent protein allophycocyanin (APC) in an energy-dependent manner. The second sequence, representing amino acids 78-92 of HuIFN-gamma, was also capable of mediating the nuclear import of APC in an energy-dependent manner but to a greatly reduced extent. The nuclear import of both sequences conjugated to APC was strongly blocked by competition with unconjugated HuIFN-gamma(122-132). Competition by the sequence HuIFN-gamma(78-92) effectively blocked the import of APC-conjugated HuIFN-gamma(78-92) but, at the same concentration, was not capable of inhibiting the nuclear import of APC-conjugated HuIFN-gamma(122-132), suggesting that HuIFN-gamma(78-92) was a less efficient NLS than HuIFN-gamma(122-132). This is consistent with >90% loss of antiviral activity of HuIFN-gamma lacking the downstream NLS in 122-132. The nuclear import of APC-conjugated HuIFN-gamma(122-132) was inhibited by a peptide containing the prototypical polybasic NLS of the SV40 T NLS, which suggests that the same Ran/importin cellular machinery is used in both cases.

The COOH-terminal nuclear localization sequence of interferon gamma regulates STAT1 alpha nuclear translocation at an intracellular site

We have recently shown that the nuclear localization of IFN gamma is mediated by a polybasic nuclear localization sequence (NLS) in its C terminus. This NLS is required for the full expression of biological activity of IFN gamma, both extracellularly and intracellularly. We now show that this NLS plays an integral intracellular role in the nuclear translocation of the transcription factor STAT1 alpha activated by IFN gamma. Treatment of IFN gamma with antibodies to the C-terminal region (95–133) containing the NLS blocked the induction of STAT1 alpha nuclear translocation. The antibodies had no effect on nuclear translocation of STAT1 alpha in IFN gamma treated cells. A deletion mutant of human IFN gamma, IFN gamma (1–123), which is devoid of the C-terminal NLS region was found to be biologically inactive, but was still able to bind to the IFN gamma receptor complex on cells with a K(d) similar to that of the wild-type protein. Deletion of the NLS specifically abolished the ability of IFN gamma(1–123) to initiate the nuclear translocation of STAT1 alpha, which is required for the biological activities of IFN gamma following binding to the IFN gamma receptor complex. Thus, the NLS region appears to contribute minimally to extracellular high-affinity receptor-ligand binding, yet exerts a strong functional role in STAT1 alpha nuclear localization. A high-affinity site for the interaction of the C-terminal NLS domain of IFN gamma with a K(d) approx. 3 × 10(−8) M(−1) has been described by previous studies on the intracellular cytoplasmic domain of the IFN gamma receptor alpha-chain. To examine the role of the NLS at the intracellular level, we microinjected neutralizing antibodies raised against the C-terminal NLS domain of IFN gamma into the cytoplasm of cells before treatment of cells with IFN gamma. These intracellular antibodies specifically blocked the nuclear translocation of STAT1 alpha following the subsequent treatment of these cells extracellularly with IFN gamma. These data show that the NLS domain of IFN gamma interacts at an intracellular site to regulate STAT1 alpha nuclear import. A C-terminal peptide of murine IFN gamma, IFN gamma(95–133), that contains the NLS motif, induced nuclear translocation of STAT1 alpha when taken up intracellularly by a murine macrophage cell line. Deletion of the NLS motif specifically abrogated the ability of this intracellular peptide to cause STAT1 alpha nuclear translocation. In cells activated with IFN gamma, IFN gamma was found to as part of a complex that contained STAT1 alpha and the importin-alpha analog Npi-1, which mediates STAT1 alpha nuclear import. The tyrosine phosphorylation of STAT1 alpha, the formation of the complex IFN gamma/Npi-1/STAT1 alpha complex and the subsequent nuclear translocation of STAT1 alpha were all found to be dependent on the presence of the IFN gamma NLS. Thus, the NLS of IFN gamma functions intracellularly to directly regulate the activation and ultimate nuclear translocation STAT1 alpha.

Down-regulation of neu/HER-2 by interferon-gamma in prostate cancer cells

Interferons (IFNs) are known to possess potent antitumor properties. Previous studies have indicated that IFNs are capable of modulating the expression of various tumor suppressor genes and oncogenes. In this study, we looked at the effect of IFN-gamma on the neu/HER-2 proto-oncogene in the DU145, LNCaP, and PC-3 prostate cancer cell lines. IFN-gamma inhibited cell proliferation in both DU145 and PC-3 cells in a dose-dependent manner, whereas no inhibition of proliferation was seen in LNCaP cells. Correspondingly, IFN-gamma treatment of DU145 and PC-3 cells resulted in an increased production of the cyclin-dependent kinase inhibitor p21(WAF1), whereas no increase in p21(WAF1) was seen in LNCaP cells. In addition, IFN-gamma induced phosphorylation of signal transducer and activator of transcription (STAT) 1 in DU145 and PC-3 cells, but not in LNCaP cells. Consistent with these findings, we found that IFN-gamma treatment of DU145 and PC-3 cells caused a reduction in neu/HER-2 expression, with no change seen in the LNCaP cell line. Transfection and overexpression of the transcriptional coactivator p300 in PC-3 cells suppressed the reduction in neu/HER-2 expression after IFN-gamma treatment, suggesting a role for p300 in neu/HER-2 expression. The antiproliferative activity and p21(WAF1) production of these cells after IFN-gamma treatment were found to be reduced as well. We propose that the down-regulation of neu/HER-2 by IFN-gamma occurs via the interaction of phosphorylated STAT1 with p300 because IFN-gamma activities requiring phosphorylated STAT1 are reduced in cells overexpressing p300. These findings suggest that neu/HER-2 may play a role in the growth of some prostate cancers and that IFN-gamma may suppress such cancers by down-regulation of neu/HER-2.

Inhibition of the glioblastoma cell cycle by type I IFNs occurs at both the G1 and S phases and correlates with the upregulation of p21(WAF1/CIP1)

The antiproliferative effect of IFNalpha was tested on the human glioblastoma cell lines, U-373MG and T98G. IFNalpha significantly inhibited the growth of both cell lines, but was more effective in retarding the growth of U-373MG cells. Flow cytometry analysis indicated that synchronized IFNalpha-treated U-373MG cells showed a strong block in the progression of cells out of the S phase of the cell cycle. T98G cells, on the other hand, showed a moderate delay in the transition of cells from G1 to S phase and only a slight delay in the S phase, consistent with the decreased antiproliferative effect of IFNalpha on this cell line. IFNalpha-treated cells were then tested for the induction of the tumor suppressor gene product, p21(WAF1/CIP1). Higher levels of p21(WAF1/CIP1) were detected in lysates from IFNalpha-treated U-373MG cells as compared to media controls for as long as 18 h. In IFNalpha-treated T98G cells, p21(WAF1/CIP1) levels were slightly elevated at 4 and 6 h, but decreased to levels similar to controls thereafter, correlating with the antiproliferative effects of IFNalpha on each cell line. Immunoprecipitation studies on lysates from IFNalpha-treated U-373MG and T98G cells indicated that increased amounts of p21(WAF1/CIP1) were complexed to both cyclin D1 and cyclin E. Further, reduced cyclin-dependent kinase 2 (cdk2) activity was found in both IFNalpha-treated U-373MG and T98G cells, suggesting a mechanism by which p21(WAF1/CIP1) exerted its antiproliferative effects. Lastly, we analyzed the time-dependent production of the cyclins D1, E, and A. No differences in cyclin D1 levels were found between IFNalpha-treated and media-treated U-373MG and T98G cells. However, both IFNalpha-treated U-373MG and T98G cells showed a prolonged elevation in cyclin E, correlating with the G1 to S phase delays observed in these cell lines. Further, the duration of cyclin E production corresponded with the magnitude of the cell cycle delays seen in IFNalpha-treated U-373MG and T98G cells. Prolonged elevation of cyclin A was also seen in both IFNalpha-treated U-373MG and T98G cells, the magnitude of which correlated with the S phase delay observed in these cell lines. Thus, the data indicate that IFNalpha has significant antiproliferative activity against glioblastoma cells that is mediated, at least in part, by the tumor suppressor gene product, p21(WAF1/CIP1).

Differential nuclear localization of the IFNGR-1 and IFNGR-2 subunits of the IFN-gamma receptor complex following activation by IFN-gamma

We have recently identified a nuclear localization sequence (NLS) in the C-terminus of murine type II interferon (IFN), IFN-gamma, that is responsible for the internalization and nuclear translocation of extracellularly added IFN-gamma. Because the uptake of IFN-gamma is a receptor-mediated endocytotic process, we examined in this study the fate of both the receptor subunits (IFNGR-1 and IFNGR-2) of the heterodimeric IFN-gamma receptor complex. Human IFN-gamma (HuIFN-gamma) was also found to contain a polybasic NLS in a conserved C-terminal region capable of directing its nuclear translocation. Like the ligand, the IFNGR-1 subunit of the receptor complex on WISH cells was found to be translocated to the nucleus on treatment with HuIFN-gamma. Using a combination of immunoprecipitation and immunofluorescence techniques, we found the nuclear accumulation of IFNGR-1 to be ligand dependent, and it was evident within 10-20 min after ligand stimulation. IFNGR-1 was found to colocalize, in a time-dependent and dose-dependent fashion, with the nuclear translocation of the transcription factor Stat1alpha, which is activated by this ligand-receptor system. In addition, Stat1alpha was found to be complexed with IFNGR-1 over the time period of its nuclear translocation. In marked contrast, IFNGR-2 was not transported to the nucleus. The surface immunofluorescence pattern of IFNGR-2 suggested that, following ligand stimulation, the majority of IFNGR-2 remains at the cell surface, whereas IFNGR-1 is endocytosed and targeted to the cell nucleus. These findings suggest that IFNGR-1 plays an active intracellular role in signal transduction events subsequent to the binding of ligand to the dimeric receptor complex. Furthermore, these studies provide the first example of the selective endocytosis and nuclear translocation of a subunit of a multimeric receptor complex.

Inhibitory effects of IFN-gamma and acyclovir on the glioblastoma cell cycle

Glioblastoma multiforme is one of the most aggressive and frequently occurring forms of brain cancer. It originates from astrocytes and is characterized by a loss of cell cycle control frequently involving mutations in tumor suppressor genes, such as p53 and p16. Nucleoside analogs, such as acyclovir (ACV), are currently being used in the treatment of viral diseases, such as those caused by members of the herpes family. Further, ACV in combination with type I interferons (IFN) has been shown to be more effective at lower doses in treatment of viral diseases. We show here that ACV at high concentrations (up to 500 microg/ml) inhibited growth in tissue culture of the human glioblastoma cell lines T98G, SNB-19, and U-373 by as much as 68.3% while inhibiting normal human astrocytes by only 38.3%. Related to this, the tumor cells were more than sevenfold more efficient in phosphorylation of ACV to the active phosphate form than normal human astrocytes. Analogous to treatment of virus-infected cells, suboptimal concentrations of ACV were as effective as high concentrations when used in conjunction with low concentrations of IFN-gamma in inhibition of tumor cell growth. At the cellular level, ACV and IFN-gamma inhibited the cell cycle in both the G1 and S phases. The cooperative effect of ACV and IFN-gamma against the glioblastomas appears to be due to direct inhibition of DNA synthesis by ACV in the S phase of the cell cycle and induction by IFN-gamma of the tumor suppressor gene p21wAF1/CIP1, which in turn acts at the level of proliferating cell nuclear antigen (PCNA) and cyclin E/cyclin-dependent kinase 2 (Cdk2) binding and inhibition of function. These studies show that the combination of IFN-gamma and ACV at suboptimal concentrations elicits significant antiproliferative effects on the glioblastoma cell lines T98G, SNB-19, and U-373 while having very little effect on normal human astrocyte cell proliferation.

IFN-gamma induction of p21(WAF1) is required for cell cycle inhibition and suppression of apoptosis

Interferons (IFN) inhibit the growth of tumor cells by blocking the progression of their cell cycle. Recently, we showed that this cell cycle inhibition correlates with the ability of IFN to upregulate the cyclin-dependent kinase inhibitor p21(WAF1). This, however, is not proof of a causal relationship. Using p21(WAF1)-deficient cells derived from the HCT116 colon adenocarcinoma cell line, we now show that p21(WAF1) is indeed responsible for the antiproliferative effects of the type II IFN, IFN-gamma. IFN-gamma upregulated p21(WAF1) expression in a p53-independent manner, decreased cyclin-dependent kinase 2 activity, and inhibited entry into the S phase of the cell cycle in p21+/+ but not in p21-/- HCT116 cells. We additionally found that the lack of p21(WAF1) expression resulted in an increase in the ability of IFN-gamma to induce apoptosis, as reflected by an earlier induction of DNA fragmentation and caspase 3 activity in p21-/- cell. Our results indicate that p21(WAF1) expression is necessary for IFN-gamma-mediated cell cycle inhibition and suppression of IFN-gamma-induced apoptosis.

IFN-tau inhibits IgE production in a murine model of allergy and in an IgE-producing human myeloma cell line

BACKGROUND

IFN-tau, a type I IFN, is an antiviral, immunomodulating, and antiproliferative agent similar to IFN-alpha and IFN-beta, but IFN-tau lacks the toxicity associated with high concentrations of these IFNs in tissue culture and in animal studies. We have previously shown that IFN-tau inhibits antibody production in a murine model of an autoimmune disease.

OBJECTIVE

We investigate the effectiveness of ovine IFN-tau and other type I IFNs in suppressing the development of allergic sensitization in a murine model of allergy by using ovalbumin (OVA) antigen as an allergen and in suppressing IgE production by using a human IgE-producing myeloma cell line.

METHODS AND RESULTS

Mice that were treated with IFN-tau in vivo before and after intraperitoneal immunization with aluminum hydroxide-precipitated OVA had significantly lower OVA-specific IgE levels than the PBS-treated group. IFN-tau-treated mice had reduced inflammatory cell infiltration into the lung tissue. Furthermore, in vitro IFN-tau treatment of splenocytes taken from OVA-immunized mice suppressed OVA-induced proliferation. Also, treatment of the IgE-producing human myeloma cell line U266BL with IFN-tau-reduced IgE production and inhibited cell proliferation compared with media controls. Similar suppression of proliferation and inhibition of IgE production was seen with other type I IFNs, as well as a humanized IFN-tau/IFN-alphaD chimeric that consists of residues 1 to 27 of the ovine IFN-tau and residues 28 to 166 of the human IFN-alphaD. The chimeric was not toxic to human peripheral white blood cells at concentrations as high as 10(5) U/mL, whereas human IFN-alphaD was toxic at 10(3) U/mL.

CONCLUSION

These data suggest that IFNs may be useful in preventing allergic sensitization by suppressing the production of allergen-specific IgE antibodies without toxic side effects.

Expression, purification, and characterization of interferon-tau produced in Pichia pastoris grown in a minimal medium

Interferon-tau (IFN-tau) is a novel type I IFN that was originally identified as a pregnancy recognition hormone. IFN-tau shares all of the biological properties of other type I IFNs including antiviral activity and antiproliferative activity through induction of the cell cycle inhibitor gene product p21WAF1. It is a promising therapy for cancers, viral infections, and for autoimmune disorders such as multiple sclerosis, without the adverse side effects associated with IFN-alpha and IFN-beta. Here, we describe novel growth and induction conditions for the expression of functionally active and uniformly 15N-labeled IFN-tau from Pichia pastoris in a minimal media for use in initial 2D- and 3D-NMR studies in solution. Purified 15N-IFN-tau was homogenous, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and MALDI-TOF mass spectrometer (MS), and retained full biological activity. MS analysis confirmed uniform isotopic labeling of IFN-tau with 15N incorporation exceeding 99%. Circular dichroism (CD) as well as 1D-NMR and 15N-1H heteronuclear single quantum coherence (HSQC) spectra confirmed that purified 15N-labeled IFN-tau has a stable secondary structure. Besides providing a route for isotope labeling of IFN-tau, our procedure may be useful for the expression and purification of other proteins that are difficult to obtain in Pichia pastoris grown in minimal media.

Crystal structure of ovine interferon-tau at 2.1 A resolution

Ovine interferon-tau (ovIFN-tau) is a pregnancy recognition hormone required for normal embryonic development in sheep. In addition to its novel role in reproductive physiology, ovIFN-tau displays antiviral and antiproliferative activities similar to the IFN-alpha subtypes. To probe the structural basis for its unique activity profile, the crystal structure of ovIFN-tau has been determined at 2.1 A resolution. The fold of ovIFN-tau is similar to the previously determined crystal structures of human IFN-alpha2b and human and murine IFN-beta, which each contain five alpha-helices. Comparison of ovIFN-tau with huIFN-alpha2b, huIFN-beta, and muIFN-beta reveals unexpected structural differences that occur in regions of considerable sequence identity. Specifically, main-chain differences up to 11 A occur for residues in helix A, the AB loop, helix B, and the BC loop. Furthermore, these regions are known to be important for receptor binding and biological activity. Of particular interest, a buried ion pair is observed in ovIFN-tau between Glu71 and Arg145 which displaces a conserved tryptophan residue (Trp77) from the helical bundle core. This ion pair represents a major change in the core of ovIFN-tau compared to huIFN-alpha2b. Based on amino acid sequence comparisons, these ovIFN-tau structural features may be conserved in several human IFN-alpha subtypes and IFN-omega. The structure identifies potential problems in interpreting site-directed mutagenesis data on the human IFN-alpha family that consists of 12 proteins.

Updating accounts following a correction of misinformation

The research examined whether corrected misinformation influences anaphoric inferences people make during subsequent reading. Participants read a set of corrected-misinformation and no-misinformation stories and made judgments about probe words that were either appropriate or inappropriate anaphoric referents. At a short delay, the results showed less activation for appropriate referents that were corrections of misinformation. At longer delays, the activation of appropriate referents showed no significant difference, but misinformation probes were more quickly recognized than were inappropriate referents that were incidentally mentioned in control story versions. In all conditions, appropriate referents showed more activation than inappropriate ones. The results suggest that corrected misinformation can continue to influence on-line reading processes.

The carboxyl terminus of interferon-gamma contains a functional polybasic nuclear localization sequence

Cytokines such as interferon-gamma (IFN-gamma), which utilize the well studied JAK/STAT pathway for nuclear signal transduction, are themselves translocated to the nucleus. The exact mechanism for the nuclear import of IFN-gamma or the functional role of the nuclear translocation of ligand in signal transduction is unknown. We show in this study that nuclear localization of IFN-gamma is driven by a simple polybasic nuclear localization sequence (NLS) in its COOH terminus, as verified by its ability to specify nuclear import of a heterologous protein allophycocyanin (APC) in standard import assays in digitonin-permeabilized cells. Similar to other nuclear import signals, we show that a peptide representing amino acids 95-132 of IFN-gamma (IFN-gamma(95-132)) containing the polybasic sequence 126RKRKRSR132 was capable of specifying nuclear uptake of the autofluorescent protein, APC, in an energy-dependent fashion that required both ATP and GTP. Nuclear import was abolished when the above polybasic sequence was deleted. Moreover, deletions immediately NH2-terminal of this sequence did not affect the nuclear import. Thus, the sequence 126RKRKRSR132 is necessary and sufficient for nuclear localization. Furthermore, nuclear import was strongly blocked by competition with the cognate peptide IFN-gamma(95-132) but not the peptide IFN-gamma(95-125), which is deleted in the polybasic sequence, further confirming that the NLS properties were contained in this sequence. A peptide containing the prototypical polybasic NLS sequence of the SV40 large T-antigen was also able to inhibit the nuclear import mediated by IFN-gamma(95-132). This observation suggests that the NLS in IFN-gamma may function through the components of the Ran/importin pathway utilized by the SV40 T-NLS. Finally, we show that intact IFN-gamma, when coupled to APC, was also able to mediate its nuclear import. Again, nuclear import was blocked by the peptide IFN-gamma(95-132) and the SV40 T-NLS peptide, suggesting that intact IFN-gamma was also transported into the nucleus through the Ran/importin pathway. Previous studies have suggested a direct intracellular role for IFN-gamma in the induction of its biological activities. Based on our data in this study, we suggest that a key intracellular site of interaction of IFN-gamma is the one with the nuclear transport mechanism that occurs via the NLS in the COOH terminus of IFN-gamma.

Mechanism of interleukin-10 inhibition of T-helper cell activation by superantigen at the level of the cell cycle

We have analyzed the effects of interleukin-10 (IL-10) on the entry of quiescent CD4(+) T cells into the cell cycle upon stimulation with the superantigen staphylococcal enterotoxin B (SEB). IL-10 arrested cells at G0/G1. IL-10 treatment prevented the downregulation of p27(Kip1), an inhibitory protein that controls progression out of the G0 phase of the cell cycle. IL-10 also prevented the upregulation of the G1 cyclins D2 and D3, proteins necessary for entry and progression through the G1 phase of the cell cycle. Associated with the inhibition of the cell cycle, IL-10 suppressed SEB induction of interleukin-2 (IL-2). Addition of exogenous IL-2 to IL-10-treated cells significantly reversed the antiproliferative effects of IL-10. Moreover, IL-10 effects on the early G1 proteins p27(Kip1) and cyclin D2 were similarly reversed by exogenous IL-2. Although this reversal by IL-2 was pronounced, it was not complete, suggesting that IL-10 may have some effects not directly related to the suppression of IL-2 production. Cell separation experiments suggest that IL-10 can effect purified CD4(+) T cells directly, providing functional evidence for the presence of IL-10 receptors on CD4(+) T cells. IL-10 also inhibited expression of IL-2 transcriptional regulators c-fos and c-jun, which also inhibit other cell functions. Our studies show that the mechanism of IL-10 regulation of quiescent CD4(+) T-cell activation is mainly by blocking induction of IL-2 that is critical to downregulation of p27(Kip1) and upregulation of D cyclins in T-cell activation and entry into the cell cycle.

IFNgamma inhibition of cell growth in glioblastomas correlates with increased levels of the cyclin dependent kinase inhibitor p21WAF1/CIP1

Glioblastoma is a highly aggressive form of brain cancer characterized by uncontrolled cell growth resulting from a loss of cell cycle regulation. In this study we determined the antiproliferative effects of interferon gamma (IFNgamma) on the glioblastoma cell lines T98G, SNB-19 and U-373, focusing on the ability of IFNgamma to increase levels of p21WAF1/CIP1, an important negative regulator of cell cycle events. IFNgamma was found to inhibit the growth of all cell lines, with inhibition ranging from 82.2% to 45.4%. Flow cytometry analysis showed that IFNgamma treatment caused a cell cycle delay in the G1 or S phases. The strength of this delay varied, correlating with the degree by which IFNgamma inhibited proliferation of each cell line. IFNgamma treatment increased the production of the cyclin dependent kinase inhibitor (CKI) p21WAF1/ CIP1 in all cell lines, the level and kinetics of production of which correlated with the degree and stage of inhibition of cellular proliferation. Further, immunoprecipitation of p21WAF1/CIP1 in complexes of p21WAF1/CIP1/cyclin-dependent kinase 2 (cdk2)/cyclin showed that the amount of p21WAF1/CIP1 in the complexes and the inhibition of cdk2-cyclin kinase activity correlated with the level of p21WAF1/CIP1 produced in the cells by IFNgamma. These results show that IFNgamma has significant antiproliferative effects on the glioblastoma cell lines and suggest that p21WAF1/CIP1 plays a role in mediating these effects.

Updating accounts following a correction of misinformation

The research examined whether corrected misinformation influences anaphoric inferences people make during subsequent reading. Participants read a set of corrected-misinformation and no-misinformation stories and made judgments about probe words that were either appropriate or inappropriate anaphoric referents. At a short delay, the results showed less activation for appropriate referents that were corrections of misinformation. At longer delays, the activation of appropriate referents showed no significant difference, but misinformation probes were more quickly recognized than were inappropriate referents that were incidentally mentioned in control story versions. In all conditions, appropriate referents showed more activation than inappropriate ones. The results suggest that corrected misinformation can continue to influence on-line reading processes.

Mechanism of HIV pathogenesis: role of superantigens in disease

Initial infection with human immunodeficiency virus (HIV) results in a burst of viremia and an ensuing spread of virus to secondary lymphoid organs, after which a "latency" period occurs with little or no virus detectable in the circulation. The term latent period has been shown to be a misnomer, because substantial viral replication occurs during this time in lymph nodes, although clinically there appears to be few symptoms of disease. However, a telling indicator of active infection during this period is the initiation of decline in CD4+ T-cell numbers. A number of hypotheses have been postulated for the mechanism(s), as of yet not fully elucidated, by which T cells are depleted. Although quiescent cells can be infected, it has been shown that replication of HIV in CD4+ T cells requires cellular activation. The levels of viremia early in infection indicate that a large number of cells are actively infected, further suggesting that a mechanism must exist by which HIV activates a large pool of cells and ultimately causes their depletion. One possible mechanism for activation would be the presence of an HIV-encoded superantigen. Superantigens are proteins that are polyclonal stimulators of CD4+ T lymphocytes. This occurs as a result of their ability to form a trimolecular complex with MHC class II molecules on antigen-presenting cells and the Vbeta-specific region on the T-cell receptor. Thus, superantigen activation of T cells is antigen-nonspecific. The prototype superantigens are the staphylococcal enterotoxins. Putative viral superantigens include a protein from mouse mammary tumor virus and related retroviruses, rabies nucleocapsid, and the Nef protein of HIV. Nef is required for optimal HIV pathogenesis, and this may be due to its superantigen properties, where CD4 cells are transformed to the activated state for virus replication.

Modulation of disease by superantigens

Increasing evidence suggests that bacterial and viral superantigens are involved in immune-mediated disease. Studies using an animal model for multiple sclerosis show that superantigens can induce relapses and bring into play autoreactive T cells with restricted usage of T cell receptor V beta families that may be indirectly involved in the initial episode of disease. This may also involve epitope spreading. Superantigens have also been implicated in other autoimmune diseases such as rheumatoid arthritis and psoriasis. Superantigens encoded by viruses such as mouse mammary tumor virus play an important role in disease progression.

IFNgamma induction of p21WAF1 in prostate cancer cells: role in cell cycle, alteration of phenotype and invasive potential

Type I and type II interferons (IFNs) are known to exert antitumor effects on a variety of tissues and cell types. We have previously shown that the type I IFN IFN alpha induces the expression of the cyclin-dependent kinase inhibitor p21WAF1 and inhibits the cell cycle of the human prostate adenocarcinoma cell line, DU145, that carries mutations in the tumor suppressor gene products p53 and pRB. We now show that the type II IFN IFN gamma similarly induces the expression of p21WAF1 and inhibits the cell cycle of DU145 cells. In addition, we show that while both IFNs exert antiproliferative activity, only IFN gamma induced phenotypic changes in these cells that accompanied the antiproliferative effect. For example, IFN gamma, but not IFN alpha, caused a significant reduction in epidermal growth factor receptor expression as well as an increase in the adhesion molecules intercellular adhesion molecule-1 and integrin alpha3. These phenotypic changes in DU145 cells are suggestive of the acquisition of a non-tumorigenic state. Consistent with these findings, IFN gamma showed a significantly lower invasive ability in in vitro assays using invasion chambers. Thus, IFN gamma inhibits both the cell cycle and the metastatic potential of DU145 cells independent of the p53 and RB status, and our data describe a mechanism for mediating the antitumor capabilities of IFN gamma that bypasses tumor suppressor genes like p53.

Hypothesis: ligand/receptor-assisted nuclear translocation of STATs

The STAT transcription factors are mediators of signal transduction of a variety of factors, including interferons (IFNs), interleukins, growth factors, and peptide hormones. Subsequent to activation, STATs are translocated to the nucleus apparently through the well-described importin/Ran system, where they activate target genes. Molecules utilizing this nuclear import system require specific nuclear localization sequences (NLSs). Paradoxically, such NLSs are not identifiable on STATs, thus raising the question of how they are imported into the nucleus. Of considerable interest is the observation that ligands and/or receptors that signal through STATs contain putative NLSs and, where examined, either ligand or receptor undergoes nuclear translocation. We hypothesize that ligands and/or their receptors serve as vehicles for the nuclear translocation of STATs, and that they may be directly involved in signal transduction. Using IFNgamma as a model system, we provide a possible mechanism for how this direct role is fulfilled. A functional NLS has been identified in a C-terminal domain of IFNgamma. This domain and the NLS contained within are crucial for the biological properties of IFNgamma in that a peptide encompassing this domain is sufficient to induce an antiviral state. Further, this domain binds specifically to a membrane-proximal region internal cytoplasmic domain of the alpha subunit of the receptor complex in a region that is directly involved in the recruitment and activation of the JAK/STAT pathway. We suggest that this novel mode of receptor recognition and activation may be a driving force for nuclear translocation of molecules like STATs that are associated with the ligand-receptor complex.

IFN-tau suppresses both the autoreactive humoral and cellular immune responses and induces stable remission in mice with chronic experimental allergic encephalomyelitis

We have previously shown that interferon-tau (IFN-tau) pretreatment inhibits the development of both acute and chronic mouse experimental allergic encephalomyelitis (EAE), an animal model for the human demyelinating disease multiple sclerosis (MS). IFN-tau is a type I IFN that has pregnancy recognition hormone activity in ruminants. Here we show that IFN-tau induced remission in SJL/J mice that had ongoing chronic active EAE disease and protected mice against secondary relapses. IFN-tau treatment reversed lymphocyte infiltration and microglial activation in the central nervous system. Mice that were treated with IFN-tau had lower levels of anti-MBP antibodies than untreated mice in both chronic and acute forms of EAE. MBP induced proliferation in B cells from EAE mice, but treatment with IFN-tau either in vivo or in vitro blocked activation. Furthermore, IFN-tau inhibited MBP activation of T cells from EAE mice. Thus, IFN-tau inhibits the humoral arm as well as the cellular arm of the autoimmune disease EAE. The data presented here show that IFN-tau inhibits both B cell and T cell responses in EAE as well as active, chronic EAE, and this may help explain the effectiveness of type I IFNs in treatment of MS.

Type I interferon induction of the Cdk-inhibitor p21WAF1 is accompanied by ordered G1 arrest, differentiation and apoptosis of the Daudi B-cell line

We show, in this study, that type I IFN induction of the cyclin-dependent kinase (cdk) inhibitor p21WAF1 in the human Burkitt lymphoma B cell-line Daudi and ensuing cell cycle arrest correlate with the terminal differentiation of these cells, and is ultimately followed by apoptosis and cell death. The expression of p21WAF1 paralleled the onset of G1 arrest and the reduction of surface IgM expression which was used as a marker of the differentiation response, and the IFN treated cells acquired a typical plasma cell-like morphology. The type II IFN IFNgamma, which does not inhibit the growth of Daudi cells, did not induce the expression of p21WAF1, nor affect the expression of surface IgM. The induction of p21WAF1 which paralleled the inhibition of the phosphorylation of the retinoblastoma protein, pRB, was preceded by the strong reduction in c-myc levels. We propose that the coupled down-regulation of c-myc and induction of p21WAF1 may be crucial to the induction of differentiation and G1 arrest in Daudi cells by type I IFN. Growth arrest and differentiation was followed by apoptosis and cell death, and was accompanied by the induction of the activity of the apoptotic ICE-family protease CPP32. G1 arrest and differentiation followed by apoptotic cell death are characteristics of terminal differentiation. Thus, our data suggest that the induction of p21WAF1 and G1 arrest mediated by type I IFN in Daudi cells is part of terminal differentiation response in these cells, highlighting a role for type I IFN as B cell terminal differentiation factors.

Immunomodulating functions of recombinant ovine interferon tau: potential for therapy in multiple sclerosis and autoimmune disorders

The interferons (IFN) are a family of complex proteins possessing antiviral, antiproliferative, and immunomodulatory activities. Two type I recombinant human IFN have been recently approved for the treatment of multiple sclerosis (MS). However, use of high dose type I IFN treatment in MS patients has been limited by dose-related toxicity. Ovine IFN tau is a unique type I interferon discovered for its role in the animal reproductive cycle. It differs from other type I IFNs in that it is remarkably less toxic even at high concentrations, is able to cross species barriers, and is not inducible by viral infection. Ovine IFN tau has been shown to be very effective in the treatment of animal models of MS. In this study, we examined the toxicity of OvIFN tau on human T-cells at high doses and its immunregulatory properties at equivalent doses. Our experiments confirmed the remarkably non-toxic nature of OvIFN tau on human cells at high concentrations as well as immunomodulating properties consistent with other type I IFNs including an antilymphoproliferative effect and inhibition of IFN gamma-induced HLA class II expression. These results suggest that OvIFN tau could be developed into a potentially less toxic therapeutic option for immune-mediated disorders including MS.

Cytokine-receptor complexes as chaperones for nuclear translocation of signal transducers

A variety of ligands that include interleukins, interferons, and growth hormones activate STAT transcriptions factors. When activated, STATs are translocated to the nucleus apparently through the well described importin/Ran system where they activate target genes. Molecules utilizing this nuclear import system require specific nuclear localization sequences (NLSs). Paradoxically, such NLSs are not identifiable on STATs, raising the question of how they are imported into the nucleus. Surprisingly, most ligands and/or receptors that signal through STATs contain putative NLSs, and where examined either ligand or receptor undergo nuclear translocation. We hypothesize that these ligands and/or their receptors serve as chaperones in the nuclear translocation of STATs, and that they may be directly involved in signal transduction. Using IFN gamma as a model system we provide a possible mechanism for how this direct role is fulfilled. A C-terminal domain of IFN gamma has been identified that contains a functional NLS. Besides the fact that this domain, and the NLS in particular, is crucial for the biological properties of IFN gamma, a peptide encompassing this domain is sufficient to induce an antiviral state. Moreover, this domain interacts exclusively with an internal cytoplasmic domain of a subunit of the receptor complex in a region that is directly involved in the recruitment and activation of the elements of the JAK/STAT pathway. We suggest that this novel mode of receptor recognition and activation may be a driving force for nuclear translocation of molecules like STATs that are associated with the ligand-receptor complex.

Human IFN gamma receptor cytoplasmic domain: expression and interaction with HuIFN gamma

To investigate the structural basis for human interferon gamma (huIFN gamma) binding to intracellular regions of the human IFN gamma receptor (huIFN gamma R), we have subcloned and expressed the huIFN gamma R free of fusion proteins in the yeast strain Pichia pastoris. HuIFN gamma bound to the cytoplasmic domain of the receptor via the IFN gamma C-terminus. Binding was inhibited by both human and mouse C-terminus peptides. N-terminus peptides failed to inhibit cytoplasmic binding. Thus, while extracellular receptor domain binding is species specific, binding to the cytoplasmic domain of the receptor is species non-specific. In solid-phase binding assays, IFN gamma had a Kd of 3.7 x 10(-8) M for the newly expressed cytoplasmic domain. Peptide competitions showed that IFN gamma bound to a receptor site corresponding to the membrane proximal residues 253-287, which is adjacent to the site of binding of the tyrosine kinase JAK2. The cytoplasmic binding affinity and binding site specificity suggest that the huIFN gamma R cytoplasmic domain can function independent of the extracellular domain to bind huIFN gamma and induce the biological activity previously associated with internalized huIFN gamma.

The solution structure of a class II major histocompatibility complex superantigen binding domain

We have used 600 MHz 1H NMR spectroscopy data to determine the solution structure of a 31-residue domain of a murine class II major histocompatibility (MHC) protein. This domain, I-Ab(beta)-(60-90), binds to the superantigen staphylococcal enterotoxin A. Distance geometry and dynamical simulated annealing calculations were performed using NOESY- and COSY-deduced constraints. I-Ab(beta)-(60-90), which is mostly alpha-helical, is more similar to the corresponding region of the class II MHC protein HLA-DR1 than to the class I MHC protein HLA-A2. Arg-72 and Arg-80 lie on the same side of the helix and face away from the antigenic peptide binding groove. His-81, implicated in both superantigen and peptide binding, is located midway between the surface defined by Arg-72/Arg-80 and residues that define the inside of the peptide binding groove, allowing for its participation in both types of binding.

Oral feeding of interferon tau can prevent the acute and chronic relapsing forms of experimental allergic encephalomyelitis

IFN tau is a member of the type I IFN family but unlike IFN alpha and IFN beta, IFN tau lacks toxicity at high concentrations. Recently, ovine IFN tau was shown to prevent acute induction and superantigen reactivation of experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). In this report, we examined the ability of IFN tau when administered by oral feeding to block development of EAE. Oral feeding of INF tau prevented paralysis in the acute form of EAE in NZW mice and chronic-relapsing EAE in SJL/J mice. In addition, oral feeding of IFN tau at 10(5) U/dose was as effective as intraperitoneal (i.p.) injection in preventing chronic-relapsing EAE, and both forms of IFN tau administration resulted in IL10 production. Histological examination revealed no inflammatory lymphocytic infiltration to the CNS in IFN tau treated animals as compared to controls. Prolonged treatment of IFN tau was shown to be necessary for chronic-relapsing EAE since removal of IFN tau treatment by either oral feeding or i.p. injection resulted in onset of disease. Lastly, sera from SJL/J mice which received prolonged IFN tau treatment by oral feeding exhibited little to no development of anti-IFN tau antibodies. Thus, oral feeding of ovine IFN tau may be a successful form of IFN tau administration for treatment of autoimmune diseases such as MS and may circumvent potentially debilitative antibody responses.

Potent anti-feline immunodeficiency virus and anti-human immunodeficiency virus effect of IFN-tau

Ovine IFN-tau is a newly described protein related to IFN-alpha that is responsible for maternal recognition of pregnancy in sheep. It has been shown to exhibit potent antiviral and antiproliferative activity. To determine its antiviral activity against feline immunodeficiency virus (FIV) and HIV, the activity of the RNA-dependent DNA polymerase, reverse transcriptase, was assayed in FIV- and HIV-infected feline and human PBL treated with IFN-tau. Significant dose-dependent inhibition of reverse transcriptase activity by IFN-tau was detected by day 6 of culture and was maintained through the peak of virus replication. In addition, production of the FIV core protein, p25, was blocked by IFN-tau. Both the amino- and carboxyl-terminal regions of IFN-tau, as identified by synthetic peptides, appear to be involved in its antiretroviral activity. Comparison of the anti-HIV activities of IFN-tau and recombinant human IFN-alpha2 (rHuIFN-alpha2) indicated that while rHuIFN-alpha2 was toxic to cells at 10,000 U/ml, IFN-tau antiretroviral activity was not associated with a decrease in either cell viability or immunologic reactivity. Thus, IFN-tau displayed potent anti-FIV and anti-HIV activity without the cytotoxicity associated with high concentrations of rHuIFN-alpha2.

CD4 T suppressor cells mediate interferon tau protection against experimental allergic encephalomyelitis

Interferon tau is a type I IFN that was originally identified as a pregnancy recognition hormone produced by trophoblast cells. It is as potent an antiviral agent as IFN alpha and IFN beta, but lacks the toxicity associated with high concentrations of these IFNs in tissue culture and in animal studies. We recently showed that IFN tau, like IFN beta, can prevent the development of experimental allergic encephalomyelitis (EAE). We report here that IFN tau prevents EAE in mice by induction of suppressor cells and suppressor factors. Suppressor cells can be induced by IFN tau in tissue culture, and in vivo by either intraperitoneal injection or by oral administration to mice. Incubation of suppressor cells with myelin basic protein (MBP)-sensitized T cells blocked or delayed the MBP-induced proliferation. Further intraperitoneal injection of suppressor cells into mice blocked induction of EAE by MBP. Suppressor cells possessed the CD4 T cell phenotype, and produced soluble suppressor factors that inhibited MBP activation of T cells from EAE mice. The suppressor factors were found to be IL-10 and TGF beta, which acted synergistically to inhibit the MBP activation of T cells from EAE mice. These findings are important for understanding the mechanism(s) by which type I IFNs protect against autoimmune disease.

Potent anti-feline immunodeficiency virus and anti-human immunodeficiency virus effect of IFN-tau

Ovine IFN-tau is a newly described protein related to IFN-alpha that is responsible for maternal recognition of pregnancy in sheep. It has been shown to exhibit potent antiviral and antiproliferative activity. To determine its antiviral activity against feline immunodeficiency virus (FIV) and HIV, the activity of the RNA-dependent DNA polymerase, reverse transcriptase, was assayed in FIV- and HIV-infected feline and human PBL treated with IFN-tau. Significant dose-dependent inhibition of reverse transcriptase activity by IFN-tau was detected by day 6 of culture and was maintained through the peak of virus replication. In addition, production of the FIV core protein, p25, was blocked by IFN-tau. Both the amino- and carboxyl-terminal regions of IFN-tau, as identified by synthetic peptides, appear to be involved in its antiretroviral activity. Comparison of the anti-HIV activities of IFN-tau and recombinant human IFN-alpha2 (rHuIFN-alpha2) indicated that while rHuIFN-alpha2 was toxic to cells at 10,000 U/ml, IFN-tau antiretroviral activity was not associated with a decrease in either cell viability or immunologic reactivity. Thus, IFN-tau displayed potent anti-FIV and anti-HIV activity without the cytotoxicity associated with high concentrations of rHuIFN-alpha2.

IFNalpha induces the expression of the cyclin-dependent kinase inhibitor p21 in human prostate cancer cells

Prostate cancer, like other types of cancer, is associated with the loss of cell cycle control, resulting in unregulated growth of cells. We report here on the inhibitory effects of interferon alpha (IFN alpha) on the cell cycle of prostate cancer cells, using the human prostate carcinoma cell line DU145 that has mutations in the tumor suppressor genes pRB, p53 and KAI1. IFN alpha inhibited growth and colony formation of DU145 cells and analysis by flow cytometry suggests that IFN alpha inhibited the progression of these cancer cells from the G1 through S phase of the cell cycle. IFN alpha treatment of DU145 cells reduced cyclin dependent kinase 2 (cdk2) activity. In particular, cyclin E dependent cdk2 activity was inhibited by IFN alpha treatment. IFN alpha treatment, however, did not affect the amount of cdk2 bound to cyclin E. Consistent with this data, IFN alpha was able to induce expression of the kinase inhibitor p21 in DU145 cells. Furthermore, IFN treatment increased the amounts of p21 complexed with cdk2 in these cells. These data support a role for p21 in mediating the antiproliferative action of IFN alpha. The induction of p21 and its growth inhibitory effects in DU145 cells appears independent of p53, pRB and KAI1 status.

Superantigens as virulence factors in autoimmunity and immunodeficiency diseases

Virulence factors are microbial products that are known to be harmful to the host and may assist in the pathogenesis of the micro-organism. Superantigens, including those produced by bacteria and viruses, clearly act as virulence factors. The clinical effects of superantigens can be not only acute but also chronic and complex. Recent evidence suggests that superantigens may play a central role in the pathogenesis of autoimmune and immunodeficiency disorders. It is our contention that superantigens, as environmental factors, can change a controllable disease into one that becomes relentless for susceptible individuals. To illustrate the detrimental effects of superantigens on disease outcome, modulation of experimental allergic encephalomyelitis by superantigen, as well as the potential role of superantigens in human immunodeficiency virus pathogenesis will be discussed. The information presented may provide valuable insight into the role of superantigens in autoimmunity and human immunodeficiency virus infection.

V beta activation by HIV Nef protein: detection by a simple amplification procedure

We previously reported that Nef protein from human immunodeficiency virus (HIV) has superantigen properties. However, we were unable to consistently demonstrate V beta-specific expansion by Nef using flow cytometry, possibly due to its lower mitogenic activity compared to prototypic superantigens. Therefore, we developed a simple amplification detection method using immobilized anti-V beta antibodies. Human peripheral blood mononuclear cells from adult donors were treated for 24 h with Nef and restimulated with immobilized anti-V beta antibodies for an additional 72 h. Significant expansion of V beta 5.3 and V beta 18 T-cells were detected in Nef-treated cultures, with expansion of V beta 18 occurring with all donors tested, and V beta 5.3 expansion occurring in 50% of the donors. Variable responses were obtained with V beta 2, V beta 3, and V beta 9. These results were confirmed using the more time-consuming method of reverse transcriptase-polymerase chain reaction (RT-PCR). Thus, this novel, reproducible, and relatively simple method can detect V beta-specific expansion by weak superantigens.

A role for the cyclin-dependent kinase inhibitor p21 in the G1 cell cycle arrest mediated by the type I interferons

Type I interferons (IFN), such as IFN-alpha, are potent antiproliferative and antitumor agents. IFN-tau, originally identified as a pregnancy recognition hormone, is a type I IFN that is related to IFN-alpha. We examine here the mechanism of the antiproliferative effects of IFN-alpha and IFN-tau in terms of their effects on intracellular events that regulate the cell cycle. Both IFN inhibited proliferation of the human Burkitt lymphoma cell line, Daudi, causing accumulation of cells in the G1 phase of the cell cycle. IFN-alpha was more effective than IFN-tau in this regard. Both IFN were found to inhibit the kinase activity of the cyclin-dependent kinase cdk2 in a manner that correlated with their relative abilities to cause cells to accumulate in the G1 phase of the cell cycle. Further, IFN treatment did not affect the expression of cdk2 protein, suggesting that the IFN modulated cdk2 activity through a cdk inhibitor. Consistent with this conclusion, both IFN induced the expression of the cyclin-dependent kinase inhibitor protein p21. The levels of p21 induced also correlated with the relative abilities of the IFN to inhibit cdk2 activity and to arrest cell growth in the G1 phase of the cell cycle. Moreover, following IFN treatment, increased levels of p21 were found complexed with cdk2, consistent with its role in the inhibition of cdk2 activity. These data suggest that p21-mediated inhibition of cdk2 activity plays an important role in the antiproliferative activity of type I IFN. The findings highlight interesting similarities between these cytokines and the products of tumor suppressor genes, such as p53, and may indicate a mechanism for the antitumor effects of the type I IFN.

Structural requirements for agonist activity of a murine interferon-gamma peptide

We have demonstrated previously that murine interferon-gamma (MuIFN-gamma) binds to the extracellular domain of the receptor alpha chain through its N-terminus and subsequently to the cytoplasmic domain of the receptor via its C-terminus. Binding of the C-terminus to the cytoplasmic domain of the receptor is thought to occur following endocytosis of the IFN-gamma-receptor complex. In fact, the MuIFN-gamma C-terminus peptide, MuIFN-gamma (95-133), has full agonist activity on macrophages where it is internalized through pinocytosis. Here we examine the structural elements required for the agonist activity of MuIFN-gamma (95-133). Disruption of the alpha helical structure of the peptide by proline substitutions or truncation of the helix resulted in significant loss of binding or loss of antiviral activity or both and induction of MHC class II molecules. Further, removal of the polycationic sequence RKRKR in the tail beyond the helical structure also resulted in loss of agonist activity. Thus, we have isolated the functional site on MuIFN-gamma to the C-terminus and have shown that its helical structure and polycationic tail are required for binding to the cytoplasmic domain of the receptor and induction of biologic activity.

HIV encodes for its own CD4 T-cell superantigen mitogen

Previously we reported that Nef protein from human immunodeficiency virus (HIV) induces proliferation of human peripheral blood mononuclear cells (PBMC). Herein, we show that HIV replicates in cells activated by Nef. PBMC proliferated in response to Nef and were capable of producing significant amounts of infectious virus upon infection. Polyclonal antibodies to Nef synthetic peptides blocked proliferation and neutralized infection. Characteristic of superantigens, T-cell proliferation in response to Nef required antigen-presenting cells and showed CD4 Vb preferences as previously shown. These findings suggest that Nef is a virally encoded T-cell superantigen and, as such, may be vital in the establishment of HIV infection in a new host and in subsequent disease pathogenesis.

Characterization of Nef-induced CD4 T cell proliferation

Studies on Nef, a regulatory protein encoded by human immunodeficiency virus (HIV), suggest it plays an important role in HIV pathogenesis. Previously, we reported that Nef binds to class II MHC antigens and induces proliferation of human peripheral blood mononuclear cells (PBMC). Herein, we further characterize PBMC responses to Nef. Polyclonal antisera generated against Nef synthetic peptides blocked proliferation. Responses were T cell-specific and required antigen-presenting cells (APC). T cells responded in the presence of paraformaldehyde-inactivated APC, suggesting that Nef is presented in an unprocessed form. Nef-stimulated cells produced IL 2 and IFN gamma, products of T helper-1 cells. Thus, Nef has superantigen properties in that it binds to MHC class II antigens, does not need processing to be presented by APC, and activates T cells, causing proliferation and production of the T helper 1 cytokines, IL 2 and IFN gamma. The identification of an HIV protein that activates T cells is of considerable interest, given that HIV replicates in T cell blasts but not in quiescent cells.

A neutralizing epitope of the superantigen SEA has agonist activity on T cells

We have previously shown that sequence 121-149 of the staphylococcal enterotoxin superantigen SEA plays an important role in superantigen function. A synthetic peptide of this region, SEA(121-149), blocks SEA binding to class II MHC molecules and induces interleukin-1 and tumor necrosis factor production in monocytes. In this study, we further emphasize the structural and functional significance of this region of SEA by showing that the SEA(121-149) peptide induces T cell proliferation in a manner similar to that of SEA. SEA(121-149) reacted with antibodies produced to SEA, and the SEA(121-149) specific antibodies neutralized SEA mitogenic activity. A tetrameric form of SEA(121-149) showed increased binding to antibodies and enhanced T cell activation, consistent with the greater avidity associated with increased valency. These data suggest that the internal domain of SEA corresponding to residues 121-149 plays an important role in superantigen activity.

Superantigens: structure and relevance to human disease

Superantigens are a class of immunostimulatory molecules produced by bacteria and viruses. Their potent immune effects are due to their unique ability to bind to the major histocompatibility complex (MHC) outside the antigen-binding cleft and to stimulate T cells in a T-cell receptor (TCR) Vbeta-specific manner. Structural studies have revealed the binding sites involved in the MHC/superantigen/TCR complex. The bacterial superantigens are responsible for a number of syndromes, including food poisoning and toxic shock syndrome, but their effects may be not only acute but also chronic and complex. Recent evidence suggests that superantigens may be relevant to the pathogenesis of autoimmune and immunodeficiency disorders. To illustrate the detrimental effects of superantigens on disease outcome, evidence demonstrating the modulation of experimental allergic encephalomyelitis, an animal model for multiple sclerosis, by superantigen, as well as the potential role of superantigens in HIV pathogenesis of AIDS, will be presented. The information presented may provide valuable insight into the role of superantigens in autoimmunity and HIV infection.

Differential recognition of the type I interferon receptor by interferons tau and alpha is responsible for their disparate cytotoxicities

Interferon tau (IFN tau), originally identified as a pregnancy recognition hormone, is a type I interferon that is related to the various IFN alpha species (IFN alpha s). Ovine IFN tau has antiviral activity similar to that of human IFN alpha A on the Madin-Darby bovine kidney (MDBK) cell line and is equally effective in inhibiting cell proliferation. In this study, IFN tau was found to differ from IFN alpha A in that is was > 30-fold less toxic to MDBK cells at high concentrations. Excess IFN tau did not block the cytotoxicity of IFN alpha A on MDBK cells, suggesting that these two type I IFNs recognize the type I IFN receptor differently on these cells. In direct binding studies, 125I-IFN tau had a Kd of 3.90 x 10(-10) M for receptor on MDBK cells, whereas that of 125I-IFN alpha A was 4.45 x 10(-11) M. Consistent with the higher binding affinity, IFN alpha A was severalfold more effective than IFN tau in competitive binding against 125I-IFN tau to receptor on MDBK cells. Paradoxically, the two IFNs had similar specific antiviral activities on MDBK cells. However, maximal IFN antiviral activity required only fractional occupancy of receptors, whereas toxicity was associated with maximal receptor occupancy. Hence, IFN alpha A, with the higher binding affinity, was more toxic than IFN tau. The IFNs were similar in inducing the specific phosphorylation of the type I receptor-associated tyrosine kinase Tyk2, and the transcription factors Stat1 alpha and Stat2, suggesting that phosphorylation of these signal transduction proteins is not involved in the cellular toxicity associated with type I IFNs. Experiments using synthetic peptides suggest that differences in the interaction at the N terminal of IFN tau and IFN alpha with the type I receptor complex contribute significantly to differences in high-affinity equilibrium binding of these molecules. It is postulated that such a differential recognition of the receptor is responsible for the similar antiviral but different cytotoxic effects of these IFNs. Moreover, these data imply that receptors are "spare'' with respect to certain biological properties, and we speculate that IFNs may induce a concentration-dependent selective association of receptor subunits.