Biomedical subjects

T Shioda

Publications and source records attributed to T Shioda.

At least 55 records · Page 3Linked to original sources

PubMed1998

Importance of the N-glycan in the V3 loop of HIV-1 envelope protein for CXCR-4- but not CCR-5-dependent fusion.

The V3 region of HIV-1 envelope protein possesses a single N-linked sugar chain, which is conserved in most HIV-1 strains. We studied its role in the life cycle of HIV-1 strains with different co-receptor usage. Removal of the glycan appeared to cause a marked reduction of CXCR-4- but not CCR-5-dependent virus entry. A basic amino acid substitution at the 11th position of V3 markedly compensated for the removal of the N-glycan. These results indicate that the N-glycan plays an important role for CXCR-4-dependent virus entry and that this role is exerted in a particular context of the peptide backbone.

Amino Acid Sequence↗

PubMed1998

Large quantity production with extreme convenience of human SDF-1alpha and SDF-1beta by a Sendai virus vector.

We describe a robust expression of human stromal cell-derived factor-1alpha (SDF-1alpha) and SDF-1beta, the members of CXC-chemokine family, with a novel vector system based upon Sendai virus, a non-segmented negative strand RNA virus. Recombinant SDF-1alpha and SDF-1beta were detected as a major protein species in culture supernatants, reached as high as 10 microg/ ml. This remarkable enrichment of the products allowed us to use even the crude supernatants as the source for biological and antiviral assays without further concentration nor purification and will thus greatly facilitate to screen their genetically engineered derivatives.

Anti-HIV Agents↗

PubMed1998

IL-4 and a glucocorticoid up-regulate CXCR4 expression on human CD4+ T lymphocytes and enhance HIV-1 replication.

CXCR4 is a key co-receptor required for the infection of T-tropic HIV-1 strain of CD4+ T lymphocytes. The regulation of this chemokine receptor was therefore studied. Th2 polarized cells expressed more CXCR4 than Th1 cells. Among a panel of cytokines and stimulants, a Th2 type cytokine interleukin-4 (IL-4) selectively up-regulated the mRNA level as well as surface protein expression of CXCR4 within 16 h. In addition, CXCR4 was also up-regulated by a glucocorticoid, dexamethasone. These treated cells became more responsive in transendothelial migration assays to the specific CXCR4 ligand, SDF-1alpha. Furthermore, up-regulation of CXCR4 was also associated with the enhancement of HIV replication in human CD4+ T lymphocytes. This study indicates the enhanced T-tropic HIV-1 infection to CD4+ T lymphocytes through up-regulation of CXCR4 by several immunomodulating agents, IL-4, and a glucocorticoid. These findings may explain the shift to T-tropic HIV-1 dominance during AIDS progression when Th2 comes to predominate.

Adjuvants, Immunologic↗

PubMed1998

Facilitation of HIV-1 isolation from patients by neuraminidase.

We previously reported that infectivities of human and other non-human lentiviruses including human immunodeficiency virus type 1 (HIV-1) are activated by desialylation of the virion surface [H. Hu et al., J Virol 70: 7,462-7,470 (1996)]. The present study was designed to determine whether neuraminidase (NA) is useful for isolation of HIV-1 from patients. Peripheral blood mononuclear cells (PBMC) or CD4+ cells isolated from the PBMC of infected individuals were cocultured with PBMC or CD4+ cells from uninfected healthy donors, and the efficiency and frequency of virus isolation in the presence of NA were compared with those by a routine conventional procedure. In a total of 41 isolation trials from 28 individuals, the presence of NA markedly increased the frequency of isolation. Furthermore, both the day when virus was first detected and the day when the virus titer was the highest in the cultures were significantly earlier in the presence of NA than in the absence of NA. The deduced amino acid sequences of the V2 and V3 regions of gp120 were identical or very similar between the isolates obtained in the presence or absence of NA, suggesting that both isolation procedures selected a similar population. NA was thus found to facilitate HIV-1 isolation and its use is recommended particularly when isolation is negative by the conventional procedures.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Dissociation of ligand-induced internalization of CXCR-4 from its co-receptor activity for HIV-1 Env-mediated membrane fusion.

The C-terminal cytoplasmic tail of chemokine receptors is important for their internalization upon ligand binding. We generated several deletion mutants of the C-terminal cytoplasmic tail of CXCR-4, a co-receptor for T cell line tropic strains of human immunodeficiency virus type 1 (HIV-1), to know whether or not co-receptor internalization is associated with HIV-1 entry. Our data showed that the removal of C-terminal 15 amino acid residues of the cytoplasmic tail from CXCR-4 completely abolished its internalization, but did not affect the co-receptor activity at all. Co-receptor activity was fully retained even when all 45 amino acid residues in the C-terminal cytoplasmic tail had been deleted. These data indicated that no cytoplasmic tail nor internalization of CXCR-4 is required for its co-receptor activity for HIV-1 entry.

Animals↗

PubMed1998

Sendai virus C proteins are categorically nonessential gene products but silencing their expression severely impairs viral replication and pathogenesis.

BACKGROUND: The P/C mRNA of Sendai virus (SeV), a prototypic member of the family Paramyxoviridae in the Mononegavirales superfamily comprising a large number of nonsegmented negative strand RNA viruses, encodes a nested set of accessory proteins, C', C, Y1 and Y2, referred to collectively as C proteins, initiating, respectively, at ACG/81 and AUGs/114, 183, 201 in the +1 frame relative to the ORF of phospho (P) protein, the smaller subunit of RNA polymerase. Among them, C is the major species expressed in infected cells at a molar ratio which is several-fold higher than the other three. However, their function has remained an enigma. It has not even been established whether or not the C proteins are essential for viral replication. Many other viruses in Mononegavirales encode C-like proteins, but their roles also remain to be defined. RESULTS: By taking advantage of a recently developed reverse genetics system to recover infectious SeV from cDNA, we created mutants in which C protein frames were variously silenced. C/C'(-) viruses which did not express C and C', but did express Y1 and Y2, were severely attenuated in replication in tissue culture cells of various species and tissues, as well as in embryonated chicken eggs. More notably, they were almost totally incapable of growing productively in--and hence nonpathogenic for mice--the natural host. Both gene expression and genome replication appeared to be impaired in C/C'(-) viruses. Additionally silencing the Y1 and Y2 expression was also possible, and a critically impaired but viable clone, the 4C(-) virus, was isolated which expressed none of the four C proteins. CONCLUSION: SeV C proteins are categorically nonessential gene products, but greatly contribute to full replication capability in vitro and are indispensable for in vivo multiplication and pathogenesis. This study represents the first comprehensive functional assessment of the accessary C protein for Mononegavirales.

Animals↗

PubMed1998

Location-specific, unequal contribution of the N glycans in simian immunodeficiency virus gp120 to viral infectivity and removal of multiple glycans without disturbing infectivity.

One of the striking features of human immunodeficiency virus, simian immunodeficiency virus (SIV), and other lentiviruses is extensive N glycosylation of the envelope protein. To assess the requirement of each N glycan for viral infectivity, we individually silenced all 23 N glycosylation sites in the gp120 subunit of SIVmac239 envelope protein by mutagenizing the canonical Asn-Xaa-Thr/Ser N glycosylation motif in an infectious molecular clone, attempted to rescue viruses from the clones, and compared the replication capability of the rescued viruses in MT4 cells. The mutation resulted in either the recovery of a fully infectious virus (category I); recovery of a faster-replicating virus, compared with the parental virus (category II); or no virus recovery (category III). These categorically different sites were not distributed randomly but were clustered. The sites of category I were localized largely in the N-terminal half, whereas the sites of categories II and III were localized in the C-terminal region, including the CD4 binding site, and the central part, including the C loop, respectively. To learn how far SIV can tolerate the removal of glycans, multiplex mutagenesis was also attempted. When they were appreciably distant from one another in the primary sequence, up to five sites could be silenced in combination without disturbing infectivity. On the other hand, it was difficult to silence contiguous sites. Thus, it appeared that a certain degree of sugar chain density over the local region had to be preserved. We discuss the potential utility of these variously deglycosylated mutants for clarifying the role of N glycans in SIV replication in vivo, as well as in the host response, and for designing vaccines and the generation of glycoprotein crystals.

Base Sequence↗

PubMed1998

Measles virus attenuation associated with transcriptional impediment and a few amino acid changes in the polymerase and accessory proteins.

Measles virus (MV) isolated in B95a cells, a marmoset B-cell line, retains full pathogenicity for cynomolgus monkeys, while its derivative obtained by adaptation to the growth in Vero cells, a monkey kidney cell line, loses the pathogenic potential (F. Kobune, H. Sakata, and A. Sugiura, J. Virol. 64:700-705, 1990). Here, we show with a pair of strains, a fresh isolate (9301B) in B95a cells and its Vero cell-adapted form (9301V), that the in vivo attenuation parallels the decrease of replication and syncytium-inducing capabilities in the original B95a cells and that these in vitro phenotypes are attributable to impediment of transcription, which is already obvious at the level of primary transcription catalyzed by the virion-associated RNA polymerase. On the other hand, cell fusion assays detected no functional difference between the glycoproteins of the two viruses. Essentially the same transcriptional impediment with reduced syncytium induction following Vero cell adaptation was found with two other pairs of strains that had been similarly prepared. Nucleotide sequence comparison between the 9301B and 9301V viruses revealed that a few (at most five) amino acid changes, which sporadically took place in the polymerase (L and P proteins) and/or accessory V and C proteins, were responsible for the in vitro and in vivo attenuation through adaptation to growth in Vero cells.

Adaptation, Physiological↗

PubMed1997

MSG1 and its related protein MRG1 share a transcription activating domain.

MSG1 is a recently described melanocyte-specific nuclear protein whose biochemical function is unknown [Shioda et al. (1996) Proc. Natl. Acad. Sci. USA 93, 12298-12303]. Two human cDNA sequences found in the EST (expressed sequence tag) database were predicted to encode a small peptide (45 aa) that showed 69% identity to the C-terminal sequence of MSG1, suggesting the existence of a novel MSG1-related protein. Based on these EST sequences, we isolated a novel gene, MRG1 (MSG1-Related Gene 1), by the 5'-RACE (rapid amplification of cDNA ends) technique. The MRG1 mRNA transcript is expressed widely and encodes a nuclear protein that share two highly conserved domains, CR1 (14 aa) and CR2 (approx. 50 aa), with MSG1. The CR2 domain is significantly acidic and activates transcription in yeast cells. The full-length MSG1 and MRG1 fused to GAL4 DNA-binding domain activates transcription in mammalian cells, and this is dependent on the presence of the CR2 domain. These results suggest that MRG1 and MSG1 may function as transcription activators.

Amino Acid Sequence↗

PubMed1997

HIV type 1 V3 variation dynamics in vivo: long-term persistence of non-syncytium-inducing genotypes and transient presence of syncytium-inducing genotypes during the course of progressive AIDS.

We performed a population-based sequence analysis of the envelope V3 region of human immunodeficiency virus type 1 (HIV-1) in two infected hemophiliacs. The study was conducted over 6-9 years, extending from the asymptomatic phase to AIDS. In both patients, serial analysis showed that the V3 population at the initial stage consisted exclusively of putative non-syncytium-inducing (NSI) genotypes. Several of these clones continued to be present without change for many years until the terminal stage and often represented the dominant species in the population at each time interval. On the other hand, syncytium-inducing (SI) genotypes were initially absent but appeared shortly before severe depletion of CD4+ T cells and their proportion in the population appeared to correlate with the viral load. In sharp contrast to NSI genotypes, SI genotypes displayed a significantly shorter presence. Thus, rapid gross population changes were found in SI genotypes, which were particularly frequent in the asymptomatic phase and less frequent in the terminal stage. Furthermore, the ratio of nonsynonymous nucleotide substitutions per synonymous substitutions in the V3 region in SI genotypes was higher than the corresponding value of NSI genotypes and the phylogenetic tree analysis revealed that a longer branch length was observed in SI genotypes than in NSI genotypes. These results suggest that there might be a stronger pressure for selection on SI viruses than on NSI viruses during the high CD4 counts on the contrary to the fact that emergence of SI genotypes was well correlated with the rapid decline of CD4 count.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Expression of Fas ligand in liver metastases of human colonic adenocarcinomas.

Fas ligand (FasL) plays a pivotal role in lymphocyte cytotoxicity and the maintenance of immunological homeostasis. Since FasL has been implicated in the existence of immunologically privileged body sites by inducing apoptosis of activated T lymphocytes, we investigated the expression of FasL in human colon cancers. We found that two out of seven primary tumors and all four hepatic metastatic tumors of surgically obtained colonic adenocarcinoma expressed FasL mRNA and protein, detected by reverse transcription-coupled PCR and by immunohistochemical staining, respectively. Expression of FasL was not detected in normal colonic epithelial cells. FasL mRNA was also expressed in some human colonic adenocarcinoma cell lines including SW480, SW1116, and LS180 cells. Cell-surface-associated FasL was detected in these human colon cancer cells by fluorescence immunocytochemical staining. In addition, the expressed FasL was demonstrated to be functional, since coculture experiments using FasL-expressing SW480 cells resulted in apoptosis of Jurkat T leukemia cells that are sensitive to Fas-mediated apoptosis, and this process was specifically inhibited by the neutralizing anti-human FasL antibody. Thus, our findings and other data suggest an alternative mechanism that enables tumors to evade immune destruction by inducing apoptosis in activated T lymphocytes. Furthermore, constitutive expression of FasL in hepatic metastatic tumors suggests that FasL may also be important in their colonization in the liver through induction of apoptosis in the surrounding Fas-expressing hepatocytes.

Adenocarcinoma↗

PubMed1997

Experimental animal model of hematogenous cardiac metastasis and neoplastic cardiac tamponade.

BACKGROUND: There have been no animal models reported that are suitable for studying cardiac metastasis. We describe a unique animal model that efficiently generates cardiac tumor colonies and neoplastic cardiac tamponade with very high incidence. METHODS: HT1080 human fibrosarcoma cells were injected intravenously into 11-day-old chick embryos. Tumor colonization was evaluated morphologically 10 days after injection. RESULTS: HT1080 cells formed massive cardiac tumor colonies with 100% (50/50) incidence; 10-20 visible surface colonies per heart, 1-3 mm in diameter. Most (>90%) of the cardiac tumor colonies were accompanied with clear, colorless pericardial effusion forming cardiac tamponade. Histological observation revealed that some tumor colonies grew within the lumen of the blood vessels in the myocardium as well as around the blood vessels. CONCLUSION: The experimental metastasis model consisting of HT1080 cells and chick embryos would be useful for studying pathophysiology of cardiac metastasis and neoplastic tamponade.

Animals↗

PubMed1997

Sendai virus-based expression of HIV-1 gp120: reinforcement by the V(-) version.

BACKGROUND: We have established a system for recovering Sendai virus (SeV), a nonsegmented negative strand RNA virus, entirely from cDNA at an extremely high rate, and have succeeded in creating a V(-) SeV whose gene expression was greatly enhanced by the deletion of the nonessential V gene. Because of its extreme medical importance, there has been a strong need for the establishment of a better system to express the gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) in sufficient quantity and purity. It also remains to be established to produce gp120 in in vitro natural host cells for HIV-1 such as human primary blood mononuclear cells, macrophages or established T cell lines. RESULTS: Using the above system, we created recombinant Sendai viruses expressing the gp120 in CV1 cells, a monkey kidney line. The expression level from the standard V(+) version has already reached 2.2/microg per 10(6) infected cells, which was readily purified from the culture fluid with a recovery rate of about 60%, and has so far appeared to be functionally and serologically authentic. The inserted gp120 gene was stably maintained during numerous passages of the recombinant virus. The V(-) version-based expression was even more robust, consistently reaching over 6.0 microg per 10(6) cells, a level that is one of the highest currently attainable for gp120 production in mammalian cells. Furthermore, a broad host range of SeV allowed gp120 production in all the three natural host cells for HIV-1 described above. CONCLUSIONS: SeV-based expression serves as a novel choice for producing large quantities of HIV-1 gp120 and will greatly facilitate biochemical, biological and immunological studies of this important glycoprotein.

DNA, Recombinant↗

PubMed1997

Creation of an infectious recombinant Sendai virus expressing the firefly luciferase gene from the 3' proximal first locus.

A genetic engineering approach was made to generate a recombinant non-segmented negative-strand RNA virus, Sendai virus (SeV) of the family Paramyxoviridae, that expresses firefly luciferase. The DNA construct containing the entire open reading frame (ORF) of the luciferase gene followed by the SeV transcription stop and restart signals connected with the conserved intergenic three nucleotides was inserted immediately before the ORF of the viral 3'-proximal nucleocapsid (N) protein gene in a full-length SeV cDNA copy. After intracellular expression of full-length antigenomic transcripts from the engineered cDNA and of the viral n ucleocapsid protein and RNA polymerase from the respective plasmids, a recombinant SeV expressing luciferase activity at a high level was recovered, although the tendency of this particular reporter gene product to aggregate in cells made it difficult to estimate the maximum level of expression. The increase in genome length brought about by inserting 1728 nucleotides into the 15,384 nucleotide parental SeV was associated with reduced plaque size, slightly slower replication kinetics and a severalfold decrease in yield of the virus. The inserted luciferase gene was stably maintained after numerous rounds of replication by serial passages in chick embryos. These results indicate the potential utility of SeV as a novel expression vector.

Animals↗

PubMed1997

Importance of the cysteine-rich carboxyl-terminal half of V protein for Sendai virus pathogenesis.

The Sendai virus V protein is a nonstructural trans-frame protein whose cysteine-rich C-terminal half is fused to the acidic N-terminal half of the P protein via mRNA editing. We recently created a mutant by disrupting the editing motif, which is devoid of mRNA editing and hence unable to produce the V protein, and demonstrated that this V(-) virus replicated normally or even faster with augmented gene expression and cytopathogenicity in cells in vitro, but was strongly attenuated in pathogenicity for mice (A. Kato, K. Kiyotani, Y. Sakai, T. Yoshida, and Y. Nagai, EMBO J. 16:578-587, 1997). Thus, although categorized as a nonessential protein, the V protein appeared to encode a luxury function required for the viral in vivo pathogenesis. Here, we created another version of a V-deficient mutant, VdeltaC, encoding only the N-terminal half but not the V-specific C-terminal half, by introducing a stop codon in the trans-V frame, and then we compared its in vitro and in vivo phenotypes with those of the V(-) and wild-type viruses. The VdeltaC virus was found to be similar to the wild-type virus in vitro with no augmented gene expression and cytopathogenicity, but in vivo, it resembled the V(-) virus, displaying a similarly attenuated phenotype. Thus, the pathogenicity determinant in the V protein was mapped to the C-terminal half. The N-terminal half was likely sufficient to confer normal (wild-type) in vitro phenotypes.

Amino Acid Sequence↗

PubMed1997

In vivo sequence variability of human immunodeficiency virus type 1 envelope gp120: association of V2 extension with slow disease progression.

According to the rate of depletion of CD4 cell counts, we grouped 12 cases of human immunodeficiency virus type 1 (HIV-1) infection as 6 rapid (21.0 to 33.8 cells per microl per month) and 6 slow (0.9 to 7.9 cells per microl per month) progressors and determined the individual viral quasispecies patterns by sequencing the genome region encoding the V1, V2, and V3 loops of envelope protein. Although the quasispecies structures varied widely from one individual to another, a strong correlation was observed between a low rate of disease progression and a high degree of genetic diversity of HIV-1. Furthermore, the V2 loop extension was observed specifically in individuals with slow or no disease progression, whereas basic amino acid substitutions in V3 characteristic of a viral phenotype shift from non-syncytium inducing to syncytium inducing were observed in patients with advanced stages of disease regardless of their rate of disease progression. Studies with recombinant viruses suggested that elongation of V2 potentially restricts the capacity of HIV-1 to replicate in macrophages. Thus, our results suggest the association of distinct sequence features of both V3 and V2 with particular patterns of disease progression. Elongation of the V2 loop may be a good predictor of slow disease progression, while basic substitutions of V3 without elongation of V2 are characteristic of rapid progression.

Amino Acid Sequence↗

PubMed1997

Early events of metastasis in the microcirculation involve changes in gene expression of cancer cells. Tracking mRNA levels of metastasizing cancer cells in the chick embryo chorioallantoic membrane.

The early events of metastasis involve multiple interactions between cancer cells and the host microcirculation during cancer cell arrest, adhesion, and extravasation. These interactions may lead to changes in gene expression of the metastasizing cancer cells, although such changes have never been demonstrated directly. To test this hypothesis, B16-F10 murine melanoma cells were injected intravenously into the chick embryo chorioallantoic membrane (CAM), and mRNA levels in the metastasizing cancer cells were evaluated by species-specific reverse transcription polymerase chain reaction. Unlike standard mouse models of experimental metastasis, the CAM model showed successful extravasation of a large number of the arrested cancer cells in the CAM microcirculation without significant cancer cell death, providing a unique opportunity to keep track of mRNA levels in cancer cells during the early phases of metastasis. Using this model, we were able to demonstrate directly the temporal induction of cancer cell genes that potentially affect metastatic efficiency, namely, Fos (5 to 60 minutes after injection), vascular permeability factor (4 to 7 hours), and urokinase plasminogen activator (> 9 hours). In conclusion, using the CAM system, we have observed an alteration of gene expression in cancer cells in the early phases of metastasis, most likely as a consequence of host-cancer cell interactions. These changes may influence the metastatic behavior of cancer cells.

Actins↗

PubMed1997

In vivo sequence changes of HIV-1 envelope V2 and V3 loops.

Human immunodeficiency virus type 1 (HIV-1) circulates in vivo as heterogeneous mixed populations (quasispecies). We analyzed the quasispecies nature of the first, second, and third hypervariable loops (V1, V2, and V3) of the gp 120 in plasma and viral isolates obtained from 19 infected individuals. Sequence analysis of 7 SI and 10 NSI isolates showed that the increased positive charge in V3 and elongation of V1 clearly correlated with viral SI capability in PBMC. Contrary to the previous report (M. Groenink et al. Science 260: 1513-1525, 1993), there appeared to be no correlation between SI or non-SI phenotype and length of V2. However, all the 5 isolates with long V2 and basic V3 showed SI phenotype, whereas 4 out of 6 isolates with short V2 and basic V3 showed NSI phenotype, still suggesting some functional cooperation of V2 and V3 on viral syncytium inducing capability. Sequence analysis of HIV-1 in plasma showed the positive correlation between V3 charge and V1 or V2 length in 4 cases. This result suggests the associated evolution of V1/V2 and V3 in these cases.

Cloning, Molecular↗