Injection Of Polyinosinic-polycytidylic Acid Research Articles

An interferon-induced GTP-binding protein, Mx, from the redlip mullet, Liza haematocheila: Deciphering its structural features and immune function

The interferon-induced GTP-binding protein Mx is responsible for a specific antiviral state against a broad spectrum of viral infections that are induced by type-I interferons (IFN α/β) in different vertebrates. In this study, the Mx gene was isolated from the constructed mullet cDNA database. Structural features of mullet Mx (MuMx) were analyzed using different in-silico tools. The pairwise comparison revealed that the MuMx sequence was related to Stegastes partitus Mx with an 83.7% sequence identity, whereas MuMx was clustered into the teleost category in the phylogentic analysis. Sequence alignment showed that the dynamin-type guanine nucleotide-binding domain (G_DYNAMIN_2), central interactive domain (CID), and GTPase effector domain (GED) were conserved among Mx counterparts. The transcriptional expression of MuMx was the highest in blood cells from unchallenged fish. The temporal mRNA profile showed that MuMx expression was significantly elevated in all tissues, including blood, spleen, head kidney, liver, and gills after the injection of polyinosinic-polycytidylic acid (poly I:C) at many time points. Moreover, MuMx expression increased slightly, in the blood, spleen, and head kidney at a few time points after the injection of lipopolysaccharide (LPS) and Lactococcus garvieae (L. garvieae). Results of the subcellular localization analysis confirmed that the MuMx protein was highly expressed in the cytoplasm. The analysis of the gene expression of the viral hemorrhagic septicemia virus (VHSV) under conditions of MuMx overexpression confirmed the significant inhibition of viral transcripts. The cell viability (MTT) assay and VHSV titer quantification with the presence of MuMx indicated a significant reduction in virus replication. Collectively, these findings suggest that Mx is a specific immune-related gene that elicits crucial antiviral functions against viral antigens in the mullet fish.

Astragalus polysaccharide improves anti-tumor immunity mediated by macrophages and natural killer cells in mice

Objective To evaluate the regulatory effects of Astragalus polysaccharide (APS) on macrophage polarization and NK cell-mediated anti-tumor responses in mice. Methods C57BL/6 mice were injected intraperitoneally with APS once a day for seven consecutive days. Activation of immune cells was then induced by intraperitoneal injection of polyinosinic-polycytidylic acid (Poly I∶C) 24 h after the APS intervention. Peritoneal macrophages were collected 24 h after induction to analyze the status of polarization and the production of nitric oxide (NO). Cytotoxicity and exocytosis of activated NK cells were measured to assess the effector functions of these cells. NK cell activities induced by NKG2D were studied in the absence of the whole JNK or JNK2 signaling pathway. Results Intraperitoneal injection of APS promoted the polarization of macrophages induced by tumor cells in mice, and enhanced the cytotoxicity of NK cells to tumor cells. However, APS was in need of the involvement of appropriate stimulatory factors to have regulatory effects. Complete inhibition of JNK signaling pathway dramatically reduced the effector functions of NK cells, which could not be recovered by APS administration. Conclusions APS was involved in the regulation of anti-tumor innate immunity through enhancing the M1-polarization of macrophages and improving the effector functions of NK cells. This study might to some extent elucidate the mechanism of APS in immune regulation and anti-tumor immunity. Key words: Astragalus polysaccharide; Innate immunity; Anti-tumor immunity; Immune regulation

Physiological responses to central and peripheral injection of polyinosinic-polycytidylic acid in chicks

ABSTRACT1. The purpose of the present study was to determine if intracerebroventricular (ICV) and intraperitoneal (IP) injection of polyinosinic-polycytidylic acid (poly I:C), a viral mimetic that binds to toll-like receptor-3 (TLR3), affects food intake, voluntary activity, cloacal temperature, plasma corticosterone (CORT) and glucose concentrations, and crop emptying rate in chicks (Gallus gallus).2. Both ICV and IP injection of poly I:C significantly decreased food intake.3. IP but not ICV injection of poly I:C significantly suppressed voluntary activity, whereas ICV injection decreased time spent sitting. Both ICV and IP injection of poly I:C significantly increased plasma CORT and glucose concentration. Neither ICV nor IP injection of poly I:C significantly affected cloacal temperature.4. In addition, ICV injection of poly I:C significantly reduced crop emptying rate, whereas IP injection had no effect.5. These results suggested that central TLR3 is related to anorexia, stress response and retardation of crop emptying while peripheral TLR3 is related to anorexia, change in behaviour and stress responses during viral infection in chicks.

Pro-epileptogenic effects of viral-like inflammation in both mature and immature brains.

BackgroundInfectious encephalitides are most often associated with acute seizures during the infection period and are risk factors for the development of epilepsy at later times. Mechanisms of viral encephalitis-induced epileptogenesis are poorly understood. Here, we evaluated the contribution of viral encephalitis-associated inflammation to ictogenesis and epileptogenesis using a rapid kindling protocol in rats. In addition, we examined whether minocycline can improve outcomes of viral-like brain inflammation.MethodsTo produce viral-like inflammation, polyinosinic-polycytidylic acid (PIC), a toll-like receptor 3 (TLR3) agonist, was applied to microglial/macrophage cell cultures and to the hippocampus of postnatal day 13 (P13) and postnatal day 74 (P74) rats. Cell cultures permit the examination of the inflammation induced by PIC, while the in vivo setting better suits the analysis of cytokine production and the effects of inflammation on epileptogenesis. Minocycline (50 mg/kg) was injected intraperitoneally for 3 consecutive days prior to the kindling procedure to evaluate its effects on inflammation and epileptogenesis.ResultsPIC injection facilitated kindling epileptogenesis, which was evident as an increase in the number of full limbic seizures at both ages. Furthermore, in P14 rats, we observed a faster seizure onset and prolonged retention of the kindling state. PIC administration also led to an increase in interleukin 1β (IL-1β) levels in the hippocampus in P14 and P75 rats. Treatment with minocycline reversed neither the pro-epileptogenic effects of PIC nor the increase of IL-1β in the hippocampus in both P14 and P75 rats.ConclusionsHippocampal injection of PIC facilitates rapid kindling epileptogenesis at both P14 and P75, suggesting that viral–induced inflammation increases epileptogenesis irrespective of brain maturation. Minocycline, however, was unable to reverse the increase of epileptogenesis, which might be linked to its absence of effect on hippocampal IL-1β levels at both ages.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0773-6) contains supplementary material, which is available to authorized users.

Impact of Maternal Stress in Pregnancy on Brain Function of the Offspring.

Epidemiological studies suggest that exposure to prenatal stressors, including malnutrition, maternal immune activation (MIA), and adverse life events, is associated with increased risks of schizophrenia, autism spectrum disorder (ASD), and attention-deficit hyperactivity disorder (ADHD). However, the underlying pathophysiological mechanisms are unclear. The first trimester of pregnancy is particularly a vulnerable period. During this period, the self-renewal of neural stem cells and neurogenesis vigorously occur, and synaptic connections are partially formed in the telencephalon. Disturbance of this neuronal proliferation and migration during the first trimester may underlie the increased susceptibility to these disorders. Epigenetic modifications, such as DNA methylation and histone modification, are critical mechanisms for regulating gene expression. They can be affected by stress and are associated with an increase in susceptibility to schizophrenia and developmental disabilities. Injection of polyinosinic-polycytidylic acid or lipopolysaccharide induces MIA, enhances the expression of proinflammatory cytokines, and leads to the activation of microglia and the subsequent epigenetic modification of neurons or glia in the offspring. Furthermore, maternal high-fat diet and obesity similarly induce MIA and therefore may increase the risk of developmental disabilities. In addition, maternal stress reprograms the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the stress response in the offspring. Thus, exposure to prenatal stress may increase the susceptibility to schizophrenia, ASD, or ADHD in the offspring through epigenetic modifications, MIA, and alteration of the HPA axis.

Polyinosinic-Polycytidylic Acid Perturbs Ovarian Functions Through Toll-Like Receptor 3-Mediated Tumor Necrosis Factor A Production in Female Mice.

Viral infections may perturb ovarian functions and female fertility. Mechanisms underlying viral perturbation of ovarian functions are incompletely understood. This study found that intraperitoneal injection of polyinosinic-polycytidylic acid [poly (I:C)] in female mice inhibits estradiol synthesis and induces ovarian granulosa cell apoptosis. Poly (I:C) is a synthetic viral double-stranded RNA analog, which induces innate antiviral responses mimicking a viral infection through activation of pattern recognition receptors, including toll-like receptor 3 (TLR3), retinoic acid-inducible gene I, and melanoma differentiation-associated gene 5. Injection of poly (I:C) significantly induced granulosa cell apoptosis in antral follicles and reduced antral follicle numbers. These effects were significantly diminished in Tlr3 knockout or tumor necrosis factor-alpha (Tnfa) knockout mice. We demonstrated that poly (I:C) induced TNFA production at a relatively high level in wild-type mice compared with that in Tlr3 knockout mice. Notably, TNFA neutralizing antibody significantly reduced poly (I:C)-induced ovarian dysfunction. In vitro assays confirmed that TNFA inhibits estradiol synthesis and induces granulosa cell apoptosis. Results provide novel insights into the mechanisms by which a mimicked viral infection perturbs ovarian functions in mice.

Focal Adhesion Kinase Inactivation Reduces the Development of Acute Leukemia and Partially Rescues Hematopoietic Stem Cell Defects in Pten-Knockout Mice

AbstractAbstract 864Phosphatase and tensin homolog on chromosome 10 (Pten) is a tumor suppressor which possesses both lipid and protein phosphatase activities. Mutations and epigenetic inactivations of the Pten gene are commonly detected in a large number of tissue malignancies, including leukemias and lymphomas. Studies using Hematopoietic Pten-knockout in adult mice (Pten−/−) have demonstrated that Pten plays a critical role in maintaining the homeostasis of bone marrow (BM) hematopoiesis. Pten inactivation promotes the proliferation and peripheral mobilization of BM hematopoietic stem cells (HSCs). Pten−/− mice develop myeloproliferative disorders (MPD) within days, followed by acute leukemic transformation. Most previous studies attributed such phenotypic changes observed in Pten−/− mice to excessive activation of the PI3K/AKT/mTOR signal, a consequence of the loss of Pten’s lipid phosphatase activity. However, the role of Pten’s protein phosphatase activity in the regulation of HSCs and leukemogenesis is not well studied.Focal adhesion kinase (Fak) is a critical substrate for the protein phosphatase activity of Pten. Dysregulation of Fak has been observed in many cancers, including acute myeloid leukemias (AML) and acute lymphocytic leukemias (ALL). Therefore, we postulated that Fak might play a pivotal role in the development and progression of leukemia following Pten deletion. To test this hypothesis, we generated Mx1-Cre+Ptenfl/flFakfl/fl mice (an interferon-inducible Pten and Fak compound-knockout, Pten−/−Fak−/−) in which both the Pten and Fak genes in the hematopoietic system are deleted upon injection of polyinosinic-polycytidylic acid (pI-pC). Our results showed that the genetic inactivation of Fak can partially rescue HSC defects associated with Pten deficiency. We found that peripheral mobilization of HSCs in Pten−/−Fak−/− mice is significantly reduced compared to Pten−/− mice. As a consequence, more long-term HSCs (LT-HSCs) are preserved in the BM of Pten−/−Fak−/− mice compared to Pten−/− mice. Transplantation studies suggested that the hematopoietic reconstitutive capacity of Pten−/−Fak−/− HSCs is significantly improved compared to Pten−/− HSCs. Although Fak deletion fails to prevent the development of MPD in Pten−/− mice, Fak deletion does significantly reduce the frequency of AML/ALL, also significantly delays the onset of AML/ALL in comparison to Pten−/− mice. This study suggests that Fak might be a potential target for preventing the MPD-to-AML/ALL transformation and therefore blocking the Fak activity may hold a promise for a novel anti-leukemia therapy. The molecular mechanisms underlying the phenotype restoration of Pten−/− mice by Fak deletion in the hematopoietic system are actively being studied in our laboratory. Disclosures:No relevant conflicts of interest to declare.

Growth Factor Independent-1 (Gfi1) As a New Target for Human Leukemia Therapy

Abstract 560More than 50% of patients diagnosed with B or T-cell leukemia and lymphoma will fail current treatment protocols. This highlights the urgent need for new and improved therapies. Since the transcription factor Growth factor independent-1 (Gfi1) plays an important role in lymphoid differentiation, we explored whether it might be a suitable target for therapy. Using mouse models in which T-cell leukemia can be induced by transgenic expression of mutated forms of Notch1, by injection of the carcinogen N-Ethyl–nitrosourea (ENU) or infection with a Murine Moloney Leukemia Virus, we found that Gfi1 knockout mice had a significantly lower incidence and a longer latency period of T-ALL. To verify whether targeting Gfi1 would be a novel approach to treat B- or T-cell lymphoma, we used Mx1Cre Gfi1fl/fl mice. In these mice, injection of polyinosinic-polycytidylic acid (pIpC) activates the Mx1 promoter driven Cre expression, which ultimately leads to the deletion of the floxed Gfi1 alleles. As controls, we used Gfi1fl/fl mice, which lack the Cre recombinase and thus still express Gfi1 after pIpC injection. To elicit a T- or B-cell lymphoma, we used ENU injection combined with expression of a mutated Notch1 transgene for T-ALL, or transgenic over-expression of c-Myc for B-cell leukemia (Eμ-Myc). Using in-vivo ultrasound supported imaging, we observed complete regression of tumour masses when Gfi1 was eliminated in Mx1Cre Gfi1fl/fl mice, curing the mice of the either the T or B-cell malignancies. Strikingly, this effect was observed in the absence of any other treatment regimen.To explore the mechanisms underlying this phenomenon, we explanted tumor samples from mice, in which Gfi1 expression was either maintained or deleted and performed gene expression arrays. A comparative analysis of the array data demonstrated that loss of Gfi1 affects pathways of key importance for leukemia such as metabolism, cell cycle progression, basal transcription and apoptosis but also the response to DNA damage. It has been shown previously for non hematological malignancies that oncogenic transformation in conjuction with dysregulated cell cycle induces DNA strand breaks (DSBs), which leads to an increased p53 dependent apoptotic response in tumours compared to non-transformed cells. This forces the tumor cells to counteract this effect – for instance by selection for the loss of p53. Consistent with this concept, we noted that leukemic cells from our tumor models displayed a greater amount of DSBs and also higher rates of spontaneous apoptosis than normal cells. Interestingly, the number of apoptotic cells was further increased in those tumors where Gfi1 had been deleted. We hypothesized that Gfi1 protects leukemia cells against DSB induced apoptosis. To test this hypothesis, we irradiated in Gfi1+/+ and Gfi1−/− thymocytes, which induces DSB in thymocytes. In line with our hypothesis we found that Gfi1−/− thymocytes showed increased rates of apoptosis compared to irradiated Gfi1+/+ thymocytes and that loss of Gfi1 led to an increased induction of pro-apoptotic genes such as Bax, Noxa and Puma after irradiation. Since Bax, Noxa and Puma are all p53 target genes, we investigated a possible link between Gfi1 and p53 and found that (I) Gfi1 binds to p53, (II) that Gfi1 inhibits the transcription of p53 target genes and (III) that Gfi1 occupies p53 target gene at the same sites as p53. In summary, Gfi1 antagonizes p53 function and loss of Gfi1 sensitizes cells to p53-mediated apoptosis.Next, we used different human T-ALL cell lines and treated these cells either with sh-RNA lentivirus or morpholinos to abrogate GFI1 expression. In all cases, down-regulation of GFI1 expression led to increased apoptosis and impeded growth of human leukemia cells. Finally, we transplanted leukemic cells of T-ALL patients into NOD-Scid, IL2Rnull (NSG) mice, waited for the leukemic cells to engraft, and then injected GFI1 specific- or control morpholinos. While mice treated with control morpholino died of leukemia, the animals treated with GFI1-specific morpholinos survived showing a significant reduction of human leukemic cells in the blood, bone marrow and spleen, even with samples from patients who did not respond to first line therapy. Since morpholinos have received approval for use in humans, our data suggest that targeting GFI1 in human T-ALL patients may be a promising therapeutic target and a feasible way to complement current T-ALL treatment regimens. Disclosures:No relevant conflicts of interest to declare.

A Mimic of Viral Double-Stranded RNA Triggers Fulminant Type 1 Diabetes-like Syndrome in Regulatory T Cell-Deficient Autoimmune Diabetic Mouse

Human fulminant type 1 diabetes (FT1D) is an extremely aggressive disease. The delay of proper diagnosis results in high mortality. However, the pathophysiology of this disease remains unclear. We took advantage of CD28-deficient NOD (CD28(-/-) NOD) mice, which have limited numbers of regulatory T cells and develop aggressive autoimmune diabetes, to create a FT1D model that mimicked the disease in humans. Young CD28(-/-) NOD mice were injected with polyinosinic-polycytidylic acid to activate innate immunity in an effort to induce diabetes onset. In this model, innate immune cell activation precedes the onset of diabetes similar to ∼70% of FT1D patients. Eighty-three percent of CD28(-/-) NOD mice developed diabetes within 1-6 d after injection of polyinosinic-polycytidylic acid. Moreover, T cells infiltrated the pancreatic exocrine tissue and destroyed α cells, an observation characteristic of human FT1D. We conclude that an FT1D-like phenotype can be induced in the background of autoimmune diabetes by a mimic of viral dsRNA, and this model is useful for understanding human FT1D.

Suppression of innate immunity (natural killer cell/interferon-γ) in the advanced stages of liver fibrosis in mice

Activation of innate immunity (natural killer [NK] cell/interferon-γ [IFN-γ]) has been shown to play an important role in antiviral and antitumor defenses as well as antifibrogenesis. However, little is known about the regulation of innate immunity during chronic liver injury. Here, we compared the functions of NK cells in early and advanced liver fibrosis induced by a 2-week or a 10-week carbon tetrachloride (CCl(4) ) challenge, respectively. Injection of polyinosinic-polycytidylic acid (poly I:C) or IFN-γ induced NK cell activation and NK cell killing of hepatic stellate cells (HSCs) in the 2-week CCl(4) model. Such activation was diminished in the 10-week CCl(4) model. Consistent with these findings, the inhibitory effect of poly I:C and IFN-γ on liver fibrosis was markedly reduced in the 10-week versus the 2-week CCl(4) model. In vitro coculture experiments demonstrated that 4-day cultured (early activated) HSCs induce NK cell activation via an NK group 2 member D/retinoic acid-induced early gene 1-dependent mechanism. Such activation was reduced when cocultured with 8-day cultured (intermediately activated) HSCs due to the production of transforming growth factor-β (TGF-β) by HSCs. Moreover, early activated HSCs were sensitive, whereas intermediately activated HSCs were resistant to IFN-γ-mediated inhibition of cell proliferation, likely due to elevated expression of suppressor of cytokine signaling 1 (SOCS1). Disruption of the SOCS1 gene restored the IFN-γ inhibition of cell proliferation in intermediately activated HSCs. Production of retinol metabolites by HSCs contributed to SOCS1 induction and subsequently inhibited IFN-γ signaling and functioning, whereas production of TGF-β by HSCs inhibited NK cell function and cytotoxicity against HSCs. The antifibrogenic effects of NK cell/IFN-γ are suppressed during advanced liver injury, which is likely due to increased production of TGF-β and expression of SOCS1 in intermediately activated HSCs.

Activation of natural killer cells inhibits liver regeneration in toxin-induced liver injury model in mice via a tumor necrosis factor-α-dependent mechanism

Liver lymphocytes are enriched in natural killer (NK) cells, and activation of NK cells by injection of polyinosinic-polycytidylic acid (poly I:C) inhibits liver regeneration in the partial hepatectomy model via production of IFN-gamma. However, the role of NK cells in liver regeneration in a model of carbon tetrachloride (CCl(4))-induced liver injury remains unknown. In this study, we investigated the effect of activation of NK cells induced by poly I:C on liver regeneration in the CCl(4) model. Administration of poly I:C suppressed liver regeneration in CCl(4)-treated mice. Depletion of NK cells but not Kupffer cells or T cells restored liver regeneration in poly I:C/CCl(4)-treated mice. Poly I:C and CCl(4) cotreatment synergistically induced accumulation of NK cells in the liver and NK cell production of IFN-gamma and tumor necrosis factor (TNF)-alpha. Serum levels of these two cytokines were also synergistically induced after poly I:C and CCl(4) treatment. Finally, blockage of TNF-alpha but not IFN-gamma restored liver regeneration in poly I:C/CCl(4)-treated mice. Taken together, these findings suggest that poly I:C treatment inhibits liver regeneration in the CCl(4)-induced liver injury model via induction of NK cell production of TNF-alpha.

TLR3‐mediated signal induces proinflammatory cytokine and chemokine gene expression in astrocytes: Differential signaling mechanisms of TLR3‐induced IP‐10 and IL‐8 gene expression

Viral infection is one of the leading causes of brain encephalitis and meningitis. Recently, it was reported that Toll-like receptor-3 (TLR3) induces a double-stranded RNA (dsRNA)-mediated inflammatory signal in the cells of the innate immune system, and studies suggested that dsRNA may induce inflammation in the central nervous system (CNS) by activating the CNS-resident glial cells. To explore further the connection between dsRNA and inflammation in the CNS, we have studied the effects of dsRNA stimulation in astrocytes. Our results show that the injection of polyinosinic-polycytidylic acid (poly(I:C)), a synthetic dsRNA, into the striatum of the mouse brain induces the activation of astrocytes and the expression of TNF-alpha, IFN-beta, and IP-10. Stimulation with poly(I:C) also induces the expression of these proinflammatory genes in primary astrocytes and in CRT-MG, a human astrocyte cell line. Furthermore, our studies on the intracellular signaling pathways reveal that poly(I:C) stimulation activates IkappaB kinase (IKK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) in CRT-MG. Pharmacological inhibitors of nuclear factor-kappaB (NF-kappaB), JNK, ERK, glycogen synthase kinase-3beta (GSK-3beta), and dsRNA-activated protein kinase (PKR) inhibit the expression of IL-8 and IP-10 in astrocytes, indicating that the activation of these signaling molecules is required for the TLR3-mediated chemokine gene induction. Interestingly, the inhibition of PI3 kinase suppressed the expression of IP-10, but upregulated the expression of IL-8, suggesting differential roles for PI3 kinase, depending on the target genes. These data suggest that the TLR3 expressed on astrocytes may initiate an inflammatory response upon viral infection in the CNS.

Induction of Bystander T Cell Proliferation by Viruses and Type I Interferon in Vivo

T cell proliferation in vivo is presumed to reflect a T cell receptor (TCR)-mediated polyclonal response directed to various environmental antigens. However, the massive proliferation of T cells seen in viral infections is suggestive of a bystander reaction driven by cytokines instead of the TCR. In mice, T cell proliferation in viral infections preferentially affected the CD44hi subset of CD8+ cells and was mimicked by injection of polyinosinic-polycytidylic acid [poly(I:C)], an inducer of type I interferon (IFN I), and also by purified IFN I; such proliferation was not associated with up-regulation of CD69 or CD25 expression, which implies that TCR signaling was not involved. IFN I [poly(I:C)]-stimulated CD8+ cells survived for prolonged periods in vivo and displayed the same phenotype as did long-lived antigen-specific CD8+ cells. IFN I also potentiated the clonal expansion and survival of CD8+ cells responding to specific antigen. Production of IFN I may thus play an important role in the generation and maintenance of specific memory.

Neurochemical and neuroendocrine responses to Newcastle disease virus administration in mice

Mice injected intraperitoneally with Newcastle disease virus (NDV) responded with increased plasma concentrations of ACTH and corticosterone and increased hypothalamic concentrations of the tryptophan and of the norepinephrine catabolite, 3-methoxy,4-hydroxyphenylethyleneglycol (MHPG) and the serotonin catabolite, 5-hydroxyindoleacetic acid (5-HIAA). Two different strains of NDV, a lentogenic and a mesogenic one, elicited dose-dependent effects in these responses. Both strains elicited near maximal responses at does around 1000 hemagglutination units. The maximal effects on ACTH, corticosterone and MHPG occurred around 2 h, but the effects on tryptophan and 5-HIAA were greatest at 8 h. Similar responses in plasma corticosterone, and cerebral tryptophan and 5-HIAA were observed following i.p. injection of polyinosinic-polycytidylic acid, but MHPG was not altered. The cyclo-oxygenase inhibitor, indomethacin, had little effect on the NDV-induced increases in plasma corticosterone and ACTH, and hypothalamic indolamines, but essentially ablated the MHPG response. The effect of NDV on plasma corticosterone, like that of endotoxin (LPS), was prevented by hypophysectomy, suggesting that the pituitary was required for these responses. These endocrine and neurochemical responses to NDV resemble those to interleukin-1 (IL-1) and LPS. Therefore we tested mice pretreated with the IL-1-receptor antagonist. This treatment prevented the neurochemical and plasma ACTH and corticosterone responses to IL-1, but did not alter those to LPS, and prevented the endocrine and neurochemical responses to NDV in approximately half of the animals. Thus IL-1 may be a mediator of the responses to NDV, but additional factors may also be involved.

Toxicité de l'acide polyinosinique-polycytidylique pour les souris infectées par le virus de la chorioméningite lymphocytaire

While injection of polyinosinic-polycytidylic acid (poly-IC) does not protect adult C3H mice against fatal brain infection with lymphocytic choriomeningitis (LCM) virus, it can have a toxic effect and bring on death four to eight hours after administration. Toxicity depends on the stage of infection of mice and on the dose of poly-IC used, and can be reduced or eliminated by administration of water and electrolytes. Administration of poly-IC gives rise to an increased induction or ⪡ priming ⪢ of interferon in relation to the level of circulating interferon induced by LCM virus. Toxicity is not, however, related to viremia. Poly-IC injected into congenitally infected mice is not toxic but does elicit a priming effect. Several hypotheses are proposed to explain this toxicity of poly-IC in mice infected with LCM virus.

Effect of polyinosinic-polycytidylic acid on the number of colony-forming cells in the hematopoietic organs of guinea pigs

An increase in the number of cells forming discrete colonies in monolayer cultures of myelokaryocytes (colony-forming cells) was observed in guinea pigs 8–24 h after receiving an intraperitoneal injection of polyinosinic-polycytidylic acid in a dose of 300μg/kg. The number of colony-forming cells in the spleen was reduced at these same time after injection of the compound. After 3 days the number of colony-forming cells in the spleen increased, but in the bone marrow it decreased. These values returned to normal 14 days after injection of the compound. The changes observed are evidently explainable on the grounds that the compound has a marked effect on the fraction of colony-forming cells in hematopoietic organs that are stromal elements of the stem-cell type.