Myxoma virus leukemia-associated protein is responsible for major histocompatibility complex class I and Fas-CD95 down-regulation and defines scrapins, a new group of surface cellular receptor abductor proteins

Down-modulation of major histocompatibility class I (MHC-I) molecules is a viral strategy for survival in the host. Myxoma virus, a member of the Poxviridae family responsible for rabbit myxomatosis, can down-modulate the expression of MHC-I molecules, but the viral factor(s) has not been described. We cloned and characterized a gene coding for an endoplasmic reticulum (ER)-resident protein containing an atypical zinc finger and two transmembrane domains, which we called myxoma virus leukemia-associated protein (MV-LAP). MV-LAP down-regulated surface MHC-I and Fas-CD95 molecules upon transfection; the mechanism probably involves an exacerbation of endocytosis and was lost when the ER retention signal was removed. In addition, the lytic activity of MHC-I-restricted antigen-specific cytolytic T lymphocytes (CTL) against myxoma virus-infected antigen-presenting target cells was significantly reduced, revealing a strong correlation between MHC-I down-regulation by MV-LAP and CTL killing in vitro. In vivo experiments with a knockout virus showed that MV-LAP is a virulence factor, potentially involved in the immunosuppression characteristic of myxomatosis. Data bank analysis revealed that MV-LAP has homologs in herpesviruses and other poxviruses. We propose the name "scrapins" to define a new group of ER-resident surface cellular receptor abductor proteins. The down-regulation of cell surface molecules by scrapins probably helps protect infected cells during viral infections.     

Lack of an immune response against the tetracycline-dependent transactivator correlates with long-term doxycycline-regulated transgene expression in nonhuman primates after intramuscular injection of recombinant adeno-associated virus

We previously documented persistent regulation of erythropoietin (Epo) secretion in mice after a single intramuscular (i.m.) injection of a recombinant adeno-associated virus (rAAV) vector harboring both the tetracycline-dependent transactivator (rtTA) and the Epo cDNA (D. Bohl, A. Salvetti, P. Moullier, and J. M. Heard, Blood 92:1512-1517, 1998). Using the same vector harboring the cynomolgus macaque Epo cDNA instead, the present study evaluated the ability of the tetracycline-regulatable (tetR) system to establish long-term transgene regulation in nonhuman primates. The vector was administered i.m., after which 5-day induction pulses were performed monthly for up to 13 months by using doxycycline (DOX), a tetracycline analog. We show that initial inductions were successful in all individuals and that there was a tight regulation and a rapid deinduction pattern upon DOX withdrawal. For one macaque, regulation of Epo secretion was maintained during the entire experimental period; for the five remaining macaques, secreted Epo became indistinguishable from endogenous Epo upon repeated DOX inductions. We investigated the mechanism involved and showed that, except in the animal in which secretion persisted, delayed humoral and cellular immune responses were directed against the rtTA transactivator protein associated with the reduction of vector DNA in transduced muscles. This study provides some evidence that, when the immune system is not mobilized against the rtTA transactivator, the tetR-regulatable system is able to support long-term transgene regulation in the context of an rAAV in nonhuman primates. In addition, our results suggest potential improvements for vector design.     

Proliferative generation of mammalian auditory hair cells in culture

Hair cell (HC) and supporting cell (SC) productions are completed during early embryonic development of the mammalian cochlea. This study shows that acutely dissociated cells from the newborn rat organ of Corti, developed into so-called otospheres consisting of 98% nestin (+) cells when plated on a non-adherent substratum in the presence of either epidermal growth factor (EGF) or fibroblast growth factor (FGF2). Within cultured otospheres, nestin (+) cells were shown to express EGF receptor (EGFR) and FGFR2 and rapidly give rise to newly formed myosin VIIA (+) HCs and p27(KIP1) (+) SCs. Myosin VIIA (+) HCs had incorporated bromodeoxyuridine (BrdU) demonstrating that they were generated by a mitotic process. Ultrastructural studies confirmed that HCs had differentiated within the otosphere, as defined by the presence of both cuticular plates and stereocilia. This work raises the hypothesis that nestin (+) cells might be a source of newly generated HCs and SCs in the injured postnatal organ of Corti.     

Extraction and quantitative analysis of the blue-green pigment “marennine” synthesized by the diatom Haslea ostrearia

This study reports further information on mareninne, awater-soluble blue-green pigment synthesized by the diatom Hasleaostrearia, which is essential to the greening of maturing oysters inFrench production areas. The extraction process is reported, as well aspreliminary characterization of a partially purified marennine extract,including quantitative spectrophotometric analysis of intracellular pigment. Amean specific extinction coefficient, E ^1% _1cm = 17.2 at 669 nm, is proposed. Results forquantitative determination of marennine accumulated in cells during batchcultures are presented, and their importance for pigment production isconsidered in relation to potential industrial applications.     

Regulation of the interleukin-1 receptor antagonist in THP-1 cells by ligands of the peroxisome proliferator-activated receptor gamma

Monocytes/macrophages (Mphi) play a pivotal role in the persistence of chronic inflammation and local tissue destruction in diseases such as rheumatoid arthritis and atherosclerosis. The production by Mphi of cytokines, chemokines, metalloproteinases and their inhibitors is an essential component in this process, which is tightly regulated by multiple factors. The peroxisome proliferator-activated receptors (PPARs) were shown to be involved in modulating inflammation. PPARgamma is activated by a wide variety of ligands such as fatty acids, the anti-diabetic thiazolidinediones (TZDs), and also by certain prostaglandins of which 15-deoxy-Delta(12,14)-PGJ2 (PGJ2). High concentrations of PPARgamma ligands were shown to have anti-inflammatory activities by inhibiting the secretion of interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNFalpha) by stimulated monocytes.The aim of this study was to determine whether PGJ2 and TZDs would also exert an immunomodulatory action through the up-regulation of anti-inflammatory cytokines such as the IL-1 receptor antagonist (IL-1Ra). THP-1 monocytic cells were stimulated with PMA, thereby enhancing the secretion of IL-1, IL-6, TNFalpha, IL-1Ra and metalloproteinases. Addition of PGJ2 had an inhibitory effect on IL-1, IL-6 and TNFalpha secretion, while increasing IL-1Ra production. In contrast, the bona fide PPARgamma ligands (TZDs; rosiglitazone, pioglitazone and troglitazone) barely inhibited proinflammatory cytokines, but strongly enhanced the production of IL-1Ra from PMA-stimulated THP-1 cells. Unstimulated cells did not respond to TZDs in terms of IL-1Ra production, suggesting that in order to be effective, PPAR ligands depend on PMA signalling. Basal levels of PPARgamma are barely detectable in unstimulated THP-1 cells, while stimulation with PMA up-regulates its expression, suggesting that higher levels of PPARgamma expression are necessary for receptor ligand effects to occur. In conclusion, we demonstrate for the first time that TZDs may exert an anti-inflammatory activity by inducing the production of the IL-1Ra.     

Inheritable forms of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) arises from parafollicular or C cells of the thyroid that produce calcitonin. It accounts for 5-10% of all thyroid cancers. Hereditary MTC represents 20-30% of all MTCs. It can be transmitted with an autosomal dominant pattern, either as a single entity, familial MTC, or it can arise as part of a multiple endocrine neoplasia (MEN) syndrome type 2A or 2B. The identification of hereditary MTC has been facilitated in recent years by the direct analysis of the ret proto-oncogene.