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Biomedical subjects

R M Simpson

Publications and source records attributed to R M Simpson.

At least 19 recordsLinked to original sources
PubMed2000

Binding of Bacillus thuringiensis delta-endotoxins Cry1Ac and Cry1Ba to a 120-kDa aminopeptidase-N of Epiphyas postvittana purified from both brush border membrane vesicles and baculovirus-infected Sf9 cells.

A 120-kDa protein was purified from brush border membrane vesicles of the tortricid moth Epiphyas postvittana (Walker) based both on its activity as an aminopeptidase and the ability to bind the Bacillus thuringiensis delta-endotoxin Cry1Ac. The purified enzyme had a pI of 5.6 and was a leucine aminopeptidase, with some isoleucine, phenylalanine and tryptophan aminopeptidase activity. Further characterisation showed that the protein was also able to bind Cry1Ba. During purification, the molecular weight of the protein decreased from 120 to 115 kDa due to the loss of a glycophosphatidinyl anchor. The protein was N-terminally sequenced and, using this information and conserved regions within other insect aminopeptidase-N (APN) sequences, redundant primers were designed to amplify the aminopeptidase coding sequence from E. postvittana midgut cDNA. The predicted protein sequence from the full-length cDNA was most closely related to the APN protein sequence from Heliothis virescens (61% identity) and shared other features of insect APNs including a Zn(2+) binding site motif and four conserved cysteines. The E. postvittana was expressed in Sf9 cells using baculovirus, yielding a protein of molecular weight 130 kDa, but with unchanged N-terminal sequence. Purified recombinant protein bound both Cry1Ac and Cry1Ba by ligand blot assays. However, despite the protein being expressed on the external surface of the Sf9 cells, it bound neither Cry1Ac nor Cry1Ba in vivo.

Amino Acid Sequence↗
PubMed2000

Passage of human T-cell leukemia virus type-1 during progression to cutaneous T-cell lymphoma results in myelopathic disease in an HTLV-1 infection model.

Studies comparing functional differences in human T-cell leukemia virus type 1 (HTLV-1) clones that mediate distinct outcomes in experimentally infected rabbits, resulted in a dermatopathic smoldering adult T-cell leukemia/lymphoma following chronic infection with HTLV-1 strain RH/K34. During the 3.5 years' follow-up, HTLV-1 skin disease progressed to cutaneous T-cell lymphoma. When infection was passed to several naive rabbits, progressive paraparesis due to myelopathic neurodegeneration, analogous to HTLV-associated myelopathy, resulted in one of 4 transfusion recipients. Similar proviral loads were detected in the two diseases, regardless of stage of progression or tissue compartment of infection. Complete proviral sequences obtained from the donor and affected recipient aligned identically with each other and with the inoculated virus clone. Existence of disparate pathogenic outcomes following infectious transmission further extends the analogy of using rabbits to model human infection and disease. Although the experimental outcomes shown are limited by numbers of animals affected, they mimic the infrequency of HTLV-1 disease and authenticate epidemiological evidence of virus sequence stability regardless of disease phenotype. The findings suggest that further investigation of a possible role for HTLV-1 in some forms of cutaneous T-cell lymphoma is warranted.

Animals↗
PubMed2000

Evidence for humoral and cellular reactivity against keratin and thyroglobulin in HTLV-I infected rabbits.

Human T cell leukemia virus type I (HTLV-I) infection was initially associated with T cell leukemia and a progressive neurologic disease but has since been linked to an increasing number of autoimmune disorders, including Sjogren's syndrome, uveitis, and polyarthritis. A survey of serum samples from a rabbit model of HTLV-I infection revealed that all had antibodies against keratin and thyroglobulin. Sera from several infected rabbits also reacted with collagen, while antibody reactions with other autoantigens tested, including DNA, were rare and sporadic. In addition to antibodies, cellular reactivity to keratin, but not thyroglobulin, was demonstrated by cellular proliferation in presence of IL-2 and keratin. Expanded cell cultures were positive for T cell activation markers and CD8. Association of the auto-reactivity with HTLV-I infection rather than random anti-cellular responses was supported by the fact that no antikeratin or antithyroglobulin was seen in uninfected controls, including that inoculated with uninfected lymphocytes. Finding autoantibodies in rabbits infected using naked HTLV-I DNA clones provided further assurance that infection induced the autoimmune reactions detected.

Animals↗
PubMed1998

The 16-kDa alpha-crystallin (Acr) protein of Mycobacterium tuberculosis is required for growth in macrophages.

Although the 16-kDa alpha-crystallin homologue of Mycobacterium tuberculosis (MTB) is the dominant protein produced by stationary phase cultures in vitro, it is undetectable in logarithmically growing cultures. By growing bacilli at defined oxygen concentrations, acr transcription was shown to be strongly induced by mildly hypoxic conditions. Acr expression also was found to be induced during the course of in vitro infection of macrophages. The acr gene was replaced with a hygromycin resistance cassette by allelic exchange in MTB H37Rv. The resulting Deltaacr::hpt strain was shown to be equivalent to wild-type H37Rv in in vitro growth rate and infectivity but was significantly impaired for growth in both mouse bone marrow derived macrophages and THP-1 cells. In addition to its proposed role in maintenance of long-term viability during latent, asymptomatic infections, these results establish a role for the Acr protein in replication during initial MTB infection.

Animals↗
PubMed1998

Source and route of exposure influence infectivity of a molecular clone of human T cell leukemia virus type I.

Infection with human T cell leukemia virus type I (HTLV-I) is typically asymptomatic, but does result in diverse diseases ranging from adult T cell leukemia to spastic neuromyelopathy. To date, differences in HTLV-I provirus structure have not been correlated with pathogenic or asymptomatic outcome of infection. Molecular clones of HTLV-I are now available and represent a powerful tool to link virus structure to pathogenesis. Present studies to explore in vivo infectivity and pathogenicity of an HTLV-I molecular clone, K30p, have utilized the rabbit as a model system. This clone was administered to neonatal or adult rabbits by several different routes and infectivity and pathogenicity were examined. Detection of antiviral humoral immune responses, presence of provirus in tissue samples, and isolation of virus in cultures of blood lymphocytes were used to establish systemic HTLV-I infection. Intramuscular, but not nervous system, exposure to K30p HTLV-I naked DNA resulted in infection. Conversely, neural exposure to T cells that had been transfected with the K30p HTLV-I DNA consistently resulted in systemic infection. Despite detection of HTLV-I provirus in brain and spinal cord of some infected rabbits, no clinical or neuropathological changes occurred. Source and route of virus exposure played a role in infectivity, but did not influence the pathogenic outcome of HTLV-I infection.

Animals↗
PubMed1997

Experimental perinatal transmission of human immunodeficiency virus type 1 by passage of infected T cells.

Pediatric AIDS typically follows transmission of human immunodeficiency virus type 1 (HIV-1) from infected mothers to their offspring. The possibility that infected maternal-origin cells serve as a conveyance for mother-to-child HIV-1 transmission was investigated in a rabbit infection model. Administration of HIV-1-infected human T cells to pregnant rabbits was followed by evaluation of offspring, from newborn to 1.5 years of age. HIV-1 was detected in 11 of 19 vaginally delivered offspring born to mothers given infected cells during gestation. Interstitial pneumonias or lymphoid organ lesions, similar to those seen in human pediatric AIDS, occurred in some offspring. Persistence of inoculum cell (HLA)-specific gene sequences in offspring indicated that vertical transmission can be effected by T cell-associated virus. These results along with features of rabbit biology, including primate-type placentation, short gestation, and delivery of litters, suggest that the rabbit model is advantageous for studies of perinatal HIV-1 transmission.

Amino Acid Sequence↗
PubMed1996

Cutaneous manifestations of human T cell leukemia virus type I infection in an experimental model.

Skin diseases ranging from infective dermatitis to cutaneous lymphoma have been associated with human T cell leukemia virus (HTLV) type I. A generalized exfoliative papillated dermatopathy occurred in a rabbit 20 months into a course of chronic HTLV-I infection. Biopsies revealed epidermotropic T cell infiltrates, including Sezary-like cells, that resulted in a pattern mimicking cutaneous T cell lymphoma. HTLV-I was isolated from affected skin, and virus expression was detected in cutaneous cultures. Sezary-like cells also occurred in circulation. Interleukin-2-independent lymphocyte cultures, established from blood exhibiting elevated CD8 T cell levels and CD25 expression, had polyclonal integration of provirus. The findings are similar to those in evolving adult T cell leukemia lymphoma and may represent a prelymphomatous change. The cutaneous lymphoproliferative lesion resulted from HTLV-I infection and further establishes the New Zealand White rabbit inoculated with the RH/K34 cell line as a suitable model for investigation of HTLV-I pathogenesis.

Adult↗
PubMed1996

Experimental acute adult T cell leukemia-lymphoma is associated with thymic atrophy in human T cell leukemia virus type I infection.

Human T cell leukemia virus type I (HTLV-1) infection may lead to an acutely fatal adult T cell leukemia-lymphoma (ATLL), but HTLV-1-infected people usually remain asymptomatic. Why only certain HTLV-I infections lead to acute ATLL, which is characterized by leukemic infiltration of multiple organs and immune suppression, remains unknown. A readily accessible animal model in which the spectrum of consequences resulting from HTLV-I infection can be observed would greatly aid studies of this retrovirus. New Zealand White rabbits inoculated with either HTLV-1-infected CD25+ T cells or cell-free virus, were serially necropsied at different intervals after death or humane sacrifice. Tissues were preserved at necropsy or cultured in vitro and subsequently prepared for morphologic or molecular examination. Rabbits inoculated with RH/K34, a productively infected rabbit T cell line that contains a monoclonally integrated full-length HTLV-I provirus, developed acute ATLL-like biologically malignant lymphoproliferative disease with lymphocyte infiltration of viscera; lymphomas consisting primarily of monoclonal expansions of RH/K34 manifested a variety of diffuse pleomorphic histologic types. Concurrently, lymphoproliferative disease was associated with onset of thymic atrophy in the presence of rapidly increasing thymic proviral load. In contrast, rabbits given two other HTLV-1 inocula, originally derived (as was RH/K34) using the human T cell line MT-2 as virus source, also became infected but did not develop thymic atrophy or the ATLL-like disease. HTLV-1 infection, thymic atrophy, and leukemic infiltration similar to acute ATLL occurred reproducibly in a New Zealand White rabbit model independent of RH/K34 inoculum and host histocompatibility. Thymic atrophy in RH/K34-inoculated rabbits, but not in rabbits given other similar HTLV-1, was consistent with immunosuppression sufficient to prevent rejection of the inoculum. Although the short, 8-day course of the experimental ATLL precludes its having a molecular pathogenesis identical to the human condition, the systemic consequences of acute ATLL, including its association with thymic atrophy, are closely modeled.

Adult↗
PubMed1995

Human T lymphocyte virus 1 from a leukemogenic cell line mediates in vivo and in vitro lymphocyte apoptosis.

HTLV-1 is implicated in the development of diverse diseases. However, most HTLV-1-infected individuals remain asymptomatic. How HTLV-1 infection leads to disparate consequences remains a mystery, despite extensive investigation of HTLV-1 isolates from infected individuals. As in human infection, experimental HTLV-1 infection in rabbits is generally benign, although HTLV-1-infected rabbit T cell lines that mediate lethal leukemia-like disease have been reported. We report here that thymuses from mature outbred rabbits inoculated with a lethal leukemia-like disease have been reported. We report here that thymuses from mature outbred rabbits inoculated with a lethal HTLV-1 T cell line (RH/K34) showed morphological and biochemical evidence of apoptosis, whereas thymuses from rabbits inoculated with nonlethal HTLV-1 T cell lines showed no signs of apoptosis. Exposure of rabbit or human lymphocytes to purified virus from RH/K34 caused rapid induction of apoptosis, providing an in vitro correlate to the pathogenic effects. By contrast, virus isolated from a nonlethal cell line mediated dose-dependent lymphocyte proliferation. These data implicate lymphocyte apoptosis as a potential mechanism by which the lethal HTLV-1 cell line causes fulminant disease and provide a means to identify factors contributing to HTLV-1 disease. Results from this HTLV-1 infection model can provide insight into variations in HTLV-1 pathogenicity in human infection.

Animals↗
PubMed1995

Rabbits transfused with human immunodeficiency virus type 1-infected blood develop immune deficiency with CD4+ lymphocytopenia in the absence of clear evidence for HIV type 1 infection.

Rabbits can be infected with human immunodeficiency virus (HIV-1), but no disease signs similar to acquired immunodeficiency syndrome (AIDS) have been reported to date. In our attempt to develop types of HIV-1 more virulent for rabbits, an immunodeficiency characterized by CD4+ lymphocytopenia and opportunistic infection was induced by transfusion from HIV-1-infected rabbits. The original donor was infected for 27 months; initial passage resulted in infection of two rabbits. Transfusions from these two infected rabbits. Transfusions from these two infected rabbits caused immunodeficiency in 12 recipients. One rabbit died at 3 months and a second at 8 months postransfusion with lymphocyte depletion in lymphoid organs; one of these and another of the CD4+ lymphocytopenic rabbits had opportunistic infections. Lentivirus-like particles were detected in thymus and spleen from an affected rabbit. Despite appearance of AIDS-like disease signs, antibodies to HIV-1 probes were detected in rabbits receiving passaged blood. However, RNA transcripts hybridizing with HIV-1 probes were detected in organs of some rabbits, implicating the initial HIV infection in the disease. Transfusion from uninfected donors produced no signs of immunodeficiency, which suggests the involvement of an HIV-related agent. The present data do not allow definitive characterization of the agent(s) involved in the immunodeficiency. Possibilities include activation of a rabbit retrovirus or, alternatively, development of a mutated HIV-1 strain.

Animals↗
PubMed1994

Heat-shock proteins expressed on the surface of human T cell leukemia virus type I-infected cell lines induce autoantibodies in rabbits.

Eight human T cell leukemia virus type I (HTLV-I)-infected cell lines were derived in vitro from peripheral blood mononuclear cells of 8 rabbits. Each rabbit was then inoculated with its own HTLV-I-transformed cells, after which all but 1 rabbit had anti-heat-shock protein (hsp) antibodies in sera. Cell line RH/K34, which failed to raise a response to hsp70, caused lethal leukemia when > 2 x 10(8) live cells were injected into unrelated outbred rabbits. Rabbits injected with cell-free virus isolated from RH/K34 cells produced anti-hsp70 antibodies and became infected but developed no fatal disease. ELISA inhibition and flow cytometry analyses indicated that hsp molecules are expressed on the surface of RH/K34 and RH/K30, a nonlethal HTLV-I cell line used for comparison; surface hsp expression does not occur normally. Two proteins of approximately 72 and 93 kDa were detected by Western blot in extracts of RH/K30 cells. Presence of anti-hsp70 antibodies correlated with resistance to lethal doses of live RH/K34 cells, suggesting that hsp immunity may influence the outcome of RH/K34 pathogenicity.

Amino Acid Sequence↗
PubMed1993

Selection of rabbit CD4- CD8- T cell receptor-gamma/delta cells by in vitro transformation with human T lymphotropic virus-I.

In vitro transformation of rabbit peripheral blood mononuclear cells (PBMC) with human T lymphotropic virus-I (HTLV)-infected human or rabbit cells resulted in CD4- CD8- cell lines, some of which caused acute leukemia when injected into rabbits. Structural analyses of the proviruses from cell lines with diverse pathogenic effects provided no clear correlation with lethality. The rabbit lines were provisionally designated T cells because they express interleukin 2R (IL-2R) and CD5 and lack surface immunoglobulin, but none express functional T cell receptor (TCR) alpha or beta transcripts. A more detailed characterization of the HTLV-I-infected cells was required to determine cell lineage and its potential influence on pathogenic consequences. Probes for rabbit TCR gamma and delta genes were derived and used to detect gamma and delta TCR RNA transcripts, identifying the in vitro transformed lines as gamma/delta T cells. CD4+ and CD8+ lines were derived from PBMC of HTLV-I-infected rabbits and CD4+ TCR-alpha/beta HTLV-I lines were derived from rabbit thymus, eliminating the possibility that the HTLV-I isolates used here transform only CD4- CD8- TCR-gamma/delta cells. The percentage of gamma/delta cells in rabbit PBMC is relatively high (23% in adult rabbits); this with diminution of CD4+ and CD8+ cells in IL-2-supplemented PBMC or thymocyte cultures may account for selection of rabbit HTLV-I-infected gamma/delta T cell lines in vitro. The availability of well-characterized T cell lines with diverse in vivo effects in the rabbit HTLV-I disease model allows evaluation of roles played by cell type in HTLV-I-mediated disease.

Animals↗
PubMed1993

Variation in HTLV-I sequences from rabbit cell lines with diverse in vivo effects.

Comparison of nucleotide sequences determined for HTLV-I integrated provirus from two rabbit cell lines, RH/K30 and RH/K34, revealed greater than 99% identity to one another. Substitutions encoding amino acid interchanges were observed in the gag, pol, and rex regions whereas the env and tax proteins were identical in the two lines. Comparison with the human prototypic HTLV-I sequence revealed considerably more variation, especially in the viral envelope region where the rabbit sequences are identical. The HTLV-I lines differed in their potential to cause disease in rabbits: injection of the RH/K34 cell line caused human adult T-cell leukemia/lymphoma-like (ATLL) disease which was fatal within 10 days, whereas all rabbits injected with the same or higher doses of RH/K30 survived with a low-grade leukemia that showed evidence of acute rejection. Correlation of lethality with viral sequence was tested by injection of rabbits with two other rabbit cell lines with HTLV-I provirus identical to RH/K34 in LTR, gag, and env regions. The fact that only one of these lines produced fatal disease suggests that pathogenic determinants lie outside of these regions or, alternatively, that the structure of the integrated virus is not the sole factor in the cell lines' ability to cause ATLL-like disease.

Animals↗