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Biomedical subjects

Thomas E Morrison

Publications and source records attributed to Thomas E Morrison.

7 recordsLinked to original sources
PubMed2025

A covalent chemical probe for Chikungunya nsP2 cysteine protease with antialphaviral activity and proteome-wide selectivity.

Chikungunya is a mosquito-borne viral disease that causes fever and severe joint pain for which there is no direct acting drug treatments. Vinyl sulfone SGC-NSP2PRO-1 (3) was identified as a potent inhibitor of the nsP2 cysteine protease (nsP2pro) that reduced viral titer against infectious isolates of Chikungunya and other alphaviruses. The covalent warhead in 3 captured the active site C478 and inactivated nsP2pro with a kinact/Ki ratio of 5950 M-1 s-1. The vinyl sulfone 3 was inactive across a panel of 23 other cysteine proteases and demonstrated remarkable proteome-wide selectivity by two chemoproteomic methods. A negative control analog SGC-NSP2PRO-1N (4) retained the isoxazole core and covalent warhead but demonstrated > 100-fold decrease in enzyme inhibition. Both 3 and 4 were stable across a wide range of pH in solution and upon prolonged storage as solids. Vinyl sulfone 3 and its negative control 4 will find utility as high-quality chemical probes to study the role of the nsP2pro in cellular studies of alphaviral replication and virulence.

Chikungunya virus↗
PubMed2006

Differential induction of type I interferon responses in myeloid dendritic cells by mosquito and mammalian-cell-derived alphaviruses.

Dendritic cells (DCs) are an important early target cell for many mosquito-borne viruses, and in many cases mosquito-cell-derived arboviruses more efficiently infect DCs than viruses derived from mammalian cells. However, whether mosquito-cell-derived viruses differ from mammalian-cell-derived viruses in their ability to induce antiviral responses in the infected dendritic cell has not been evaluated. In this report, alphaviruses, which are mosquito-borne viruses that cause diseases ranging from encephalitis to arthritis, were used to determine whether viruses grown in mosquito cells differed from mammalian-cell-derived viruses in their ability to induce type I interferon (IFN) responses in infected primary dendritic cells. Consistent with previous results, mosquito-cell-derived Ross River virus (mos-RRV) and Venezuelan equine encephalitis virus (mos-VEE) exhibited enhanced infection of primary myeloid dendritic cells (mDCs) compared to mammalian-cell-derived virus preparations. However, unlike the mammalian-cell-derived viruses, which induced high levels of type I IFN in the infected mDC cultures, mos-RRV and mos-VEE were poor IFN inducers. Furthermore, the poor IFN induction by mos-RRV contributed to the enhanced infection of mDCs by mos-RRV. These results suggest that the viruses initially delivered by the mosquito vector differ from those generated in subsequent rounds of replication in the host, not just with respect to their ability to infect dendritic cells but also in their ability to induce or inhibit antiviral type I IFN responses. This difference may have an important impact on the mosquito-borne virus's ability to successfully make the transition from the arthropod vector to the vertebrate host.

Alphavirus↗
PubMed2006

Characterization of Ross River virus tropism and virus-induced inflammation in a mouse model of viral arthritis and myositis.

Mosquito-borne alphaviruses are a significant cause of both encephalitic and arthritic disease in humans worldwide. In contrast to the encephalitic alphaviruses, the pathogenesis of alphavirus-induced arthritic disease is not well understood. Utilizing a mouse model of Ross River virus (RRV) disease, we found that the primary targets of RRV infection are bone, joint, and skeletal muscle tissues of the hind limbs in both outbred CD-1 mice and adult C57BL/6J mice. Moreover, histological analyses demonstrated that RRV infection resulted in severe inflammation of these tissues. Characterization of the inflammatory infiltrate within the skeletal muscle tissue identified inflammatory macrophages, NK cells, and CD4+ and CD8+ T lymphocytes. To determine the contribution of the adaptive immune system, the outcome of RRV-induced disease was examined in C57BL/6J RAG-1(-/-) mice, which lack functional T and B lymphocytes. RAG-1(-/-) and wild-type mice developed similar disease signs, infiltration of inflammatory macrophages and NK cells, and muscle pathology, suggesting that the adaptive immune response does not play a critical role in the development of disease. These results establish the mouse model of RRV disease as a useful system for the identification of viral and host factors that contribute to alphavirus-induced arthritis and myositis.

Alphavirus Infections↗
PubMed2004

BZLF1, an Epstein-Barr virus immediate-early protein, induces p65 nuclear translocation while inhibiting p65 transcriptional function.

We have previously demonstrated that the Epstein-Barr virus immediate-early BZLF1 protein interacts with, and is inhibited by, the NF-kappaB family member p65. However, the effects of BZLF1 on NF-kappaB activity have not been intensively studied. Here we show that BZLF1 inhibits p65-dependent gene expression. BZLF1 inhibited the ability of IL-1, as well as transfected p65, to activate the expression of two different NF-kappaB-responsive genes, ICAM-1 and IkappaB-alpha. BZLF1 also reduced the constitutive level of IkappaB-alpha protein in HeLa and A549 cells, and increased the amount of nuclear NF-kappaB to a similar extent as tumor necrosis factor-alpha (TNF-alpha) treatment. In spite of this BZLF1-associated increase in the nuclear form of NF-kappaB, BZLF1 did not induce binding of NF-kappaB to NF-kappaB responsive promoters (as determined by chromatin immunoprecipitation assay) in vivo, although TNF-alpha treatment induced NF-kappaB binding as expected. Overexpression of p65 dramatically inhibited the lytic replication cycle of EBV in 293-EBV cells, confirming that NF-kappaB also inhibits BZLF1 transcriptional function. Our results are consistent with a model in which BZLF1 inhibits the transcriptional function of p65, resulting in decreased transcription of IkappaB-alpha, decreased expression of IkappaB-alpha protein, and subsequent translocation of NF-kappaB to the nucleus. This nuclear translocation of NF-kappaB may promote viral latency by negatively regulating BZLF1 transcriptional activity. In situations where p65 activity is limiting in comparison to BZLF1, the ability of BZLF1 to inhibit p65 transcriptional function may protect the virus from the host immune system during the lytic form of infection.

Active Transport, Cell Nucleus↗
PubMed2004

Epstein-Barr virus immediate-early protein BZLF1 inhibits tumor necrosis factor alpha-induced signaling and apoptosis by downregulating tumor necrosis factor receptor 1.

Tumor necrosis factor alpha (TNF-alpha) is a key mediator of host immune and inflammatory responses and inhibits herpesvirus replication by cytolytic and noncytolytic mechanisms. TNF-alpha effects are primarily mediated through the major TNF-alpha receptor, TNF-R1, which is constitutively expressed in most cell types. Here we show that the Epstein-Barr virus (EBV) immediate-early protein BZLF1 prevents TNF-alpha activation of target genes and TNF-alpha-induced cell death. These effects are mediated by down-regulation of the promoter for TNF-R1. Additionally, we demonstrate that expression of TNF-R1 is downregulated during the EBV lytic replication cycle. Thus, EBV has developed a novel mechanism for evading TNF-alpha antiviral effects during lytic reactivation or primary infection.

Apoptosis↗
PubMed2004

The BRRF1 early gene of Epstein-Barr virus encodes a transcription factor that enhances induction of lytic infection by BRLF1.

The switch from the latent to the lytic form of Epstein-Barr virus (EBV) infection is mediated by expression of the viral immediate-early (IE) proteins, BZLF1 (Z) and BRLF1 (R). An EBV early protein, BRRF1 (Na), is encoded by the opposite strand of the BRLF1 intron, but the function of this nuclear protein in the viral life cycle is unknown. Here we demonstrate that Na enhances the R-mediated induction of lytic EBV infection in 293 cells latently infected with a recombinant EBV (R-KO) defective for the expression of both R and Na. Na also enhances R-induced lytic infections in a gastric carcinoma line (AGS) carrying the R-KO virus, although it has no effect in a Burkitt lymphoma line (BL-30) stably infected with the same mutant virus. We show that Na is a transcription factor that increases the ability of R to activate Z expression from the R-KO viral genome in 293 cells and that Na by itself activates the Z promoter (Zp) in EBV-negative cells. Na activation of Zp requires a CRE motif (ZII), and a consensus CRE motif is sufficient to transfer Na responsiveness to the heterologous E1b promoter. Furthermore, we show that Na enhances the transactivator function of a Gal4-c-Jun fusion protein but does not increase the transactivator function of other transcription factors (including ATF-1, ATF-2, and CREB) known to bind CRE motifs. Na expression in cells results in increased levels of a hyperphosphorylated form of c-Jun, suggesting a mechanism by which Na activates c-Jun. Our results indicate that Na is a transcription factor that activates the EBV Zp IE promoter through its effects on c-Jun and suggest that Na cooperates with BRLF1 to induce the lytic form of EBV infection in certain cell types.

Genes, Immediate-Early↗