Biomedical subjects

Marvin Reitz

Publications and source records attributed to Marvin Reitz.

7 recordsLinked to original sources

PubMed2006

Human mesenchymal stem cells exert potent antitumorigenic effects in a model of Kaposi's sarcoma.

Emerging evidence suggests that both human stem cells and mature stromal cells can play an important role in the development and growth of human malignancies. In contrast to these tumor-promoting properties, we observed that in an in vivo model of Kaposi's sarcoma (KS), intravenously (i.v.) injected human mesenchymal stem cells (MSCs) home to sites of tumorigenesis and potently inhibit tumor growth. We further show that human MSCs can inhibit the in vitro activation of the Akt protein kinase within some but not all tumor and primary cell lines. The inhibition of Akt activity requires the MSCs to make direct cell-cell contact and can be inhibited by a neutralizing antibody against E-cadherin. We further demonstrate that in vivo, Akt activation within KS cells is potently down-regulated in areas adjacent to MSC infiltration. Finally, the in vivo tumor-suppressive effects of MSCs correlates with their ability to inhibit target cell Akt activity, and KS tumors engineered to express a constitutively activated Akt construct are no longer sensitive to i.v. MSC administration. These results suggest that in contrast to other stem cells or normal stromal cells, MSCs possess intrinsic antineoplastic properties and that this stem cell population might be of particular utility for treating those human malignancies characterized by dysregulated Akt.

Animals↗

PubMed2005

Plant based HIV-1 vaccine candidate: Tat protein produced in spinach.

The HIV-1 Tat protein has been recently explored as a prospective vaccine candidate with broad, subtype non-specific action. We approached the problem of delivery of Tat through the mucosal route by expressing Tat in an edible plant. The tat gene was assembled from synthetic overlapping oligonucleotides, and was subsequently cloned into a plant virus-based vector tobacco mosaic virus (TMV). Spinach plants inoculated with the Tat-producing constructs were collected and fed to mice 7-14 days post inoculation. DNA vaccinations were performed using a gene gun. Codon optimization of the Tat gene expressed in spinach plants resulted in several-fold yield increase as detected in immunoblots, and did not cause severe symptoms in inoculated plants. Mice were fed with the Tat-producing or control vector-inoculated spinach. After three feedings, 1 week apart, 1g per mice, no differences were detected in the growth rate or behavior of the animals fed with these three types of spinach. None of the animals developed measurable Tat antibodies. Following DNA vaccination, however, mice having previously received oral Tat developed higher antibody titers to Tat than did the controls, with the titers peaking at 4 weeks post-vaccination. Codon optimization allows production of up to 300-500 microg of Tat antigen per 1 g of leaf tissue in spinach using a plant virus-based expression system. The plant produced Tat does not seem to have any apparent adverse effect on mice growth or behavior, when fed with spinach for 4 weeks. ELISA data suggested that oral Tat primed for the development of Tat antibodies when mice were subsequently vaccinated with plasmid DNA designed for Tat expression.

AIDS Vaccines↗

PubMed2004

HIV-1 transgenic rats develop T cell abnormalities.

HIV-1 infection leads to impaired antigen-specific T cell proliferation, increased susceptibility of T cells to apoptosis, progressive impairment of T-helper 1 (Th1) responses, and altered maturation of HIV-1-specific memory cells. We have identified similar impairments in HIV-1 transgenic (Tg) rats. Tg rats developed an absolute reduction in CD4+ and CD8+ T cells able to produce IFN-gamma following activation and an increased susceptibility of T cells to activation-induced apoptosis. CD4+ and CD8+ effector/memory (CD45RC- CD62L-) pools were significantly smaller in Tg rats compared to non-Tg controls, although the converse was true for the naïve (CD45RC+ CD62L+) T cell pool. Our interpretation is that the HIV transgene causes defects in the development of T cell effector function and generation of specific effector/memory T cell subsets, and that activation-induced apoptosis may be an essential factor in this process.

Animals↗

PubMed2004

Tumorigenesis by human herpesvirus 8 vGPCR is accelerated by human immunodeficiency virus type 1 Tat.

Human herpesvirus 8 (HHV-8), also called Kaposi's sarcoma (KS) herpesvirus, can cause KS but is inefficient. Untreated human immunodeficiency virus type 1 (HIV-1) coinfection is a powerful risk factor. The HHV-8 chemokine receptor, vGPCR (ORF74), activates NF-kappaB and NF-AT, and their levels of activation are synergistically increased by HIV-1 Tat. Transgenic vGPCR mice develop KS-like tumors. A cell line derived from one such tumor expresses vGPCR and forms tumors in nude mice. Here we show that transfection of DNA encoding HIV-1 tat (but not a transactivation-defective mutant) into these tumor cells increases NF-kappaB and NF-AT activation levels and accelerates tumor formation. Tumorigenesis was also accelerated when Tat DNA was transfected into normal cells and the transfected cells were mixed with the tumor cells and injected into a single site. Tumorigenesis was also increased when the two cell types were injected at separate sites, suggesting that tumorigenesis is accelerated by Tat through soluble factors.

Animals↗

PubMed2003

Characterization of a simian human immunodeficiency virus encoding the envelope gene from the CCR5-tropic HIV-1 Ba-L.

The tat, rev, vpu, and env genes from the monocytotropic CCR5-dependent HIV-1 Ba-L isolate were substituted for homologous simian immunodeficiency virus (SIV) sequences in the SIV genome. The resultant SHIV (SHIV Ba-L) replicated in CCR5-positive PM-1 cells but not in CCR5-negative CEMX174 cells. Infection of HOS cells expressing different co-receptors showed SHIV Ba-L to be strictly CCR5-dependent. Infection of PM-1 cells and rhesus peripheral blood mononuclear cells (PBMCs) was highly sensitive to RANTES but not to SDF-1. Although SHIV Ba-L infected rhesus and pigtail macaques intravenously or rectally, plasma viremia was controlled after 3 weeks. After serial passage through 4 pigtails by blood and bone marrow transfer, virus from pigtail PBMCs had higher in vitro infectious titers on rhesus PBMCs and was efficiently transmitted vaginally in rhesus and cynomolgus macaques. Plasma viremia generally persisted longer than after infection with unpassaged virus but was eventually controlled with no significant decrease in CD4+ T-cell counts in peripheral blood. The envelope gene of SHIV Ba-L revealed a very little genetic drift during in vivo passage. SHIV Ba-L provides a potentially useful model for R5 HIV-1 infection of humans.

Animals↗

PubMed2003

Human herpesvirus 8-encoded vGPCR activates nuclear factor of activated T cells and collaborates with human immunodeficiency virus type 1 Tat.

Human herpesvirus 8 (HHV-8), the etiologic agent of Kaposi's sarcoma (KS), encodes a chemokine receptor homologue, the viral G protein-coupled receptor (vGPCR), that has been implicated in KS pathogenesis. Expression of vGPCR constitutively activates several signaling pathways, including NF-kappa B, and induces the expression of proinflammatory and angiogenic factors, consistent with the inflammatory hyperproliferative nature of KS lesions. Here we show that vGPCR also constitutively activates the nuclear factor of activated T cells (NF-AT), another transcription factor important in regulation of the expression of inflammatory cytokines and related factors. NF-AT activation by vGPCR depended upon signaling through the phosphatidylinositol 3-kinase-Akt-glycogen synthetase kinase 3 (PI3-K/Akt/GSK-3) pathway and resulted in increased expression of NF-AT-dependent cell surface molecules (CD25, CD29, Fas ligand), proinflammatory cytokines (interleukin-2 [IL-2], IL-4), and proangiogenic factors (granulocyte-macrophage colony-stimulating factor GMCSF and TNF alpha). vGPCR expression also increased endothelial cell-T-cell adhesion. Although infection with HHV-8 is necessary to cause KS, coinfection with human immunodeficiency virus type 1 (HIV-1), in the absence of antiretroviral suppressive therapy, increases the risk of KS by many orders of magnitude. NF-AT and NF-kappa B activation by vGPCR was greatly increased by the HIV-1 Tat protein, although Tat alone had little effect on NF-AT. The enhancement of NF-AT by Tat appears to be mediated through collaborative stimulation of the PI3-K/Akt/GSK-3 pathway by vGPCR and Tat. Our data further support the idea that vGPCR contributes to the pathogenesis of KS by a paracrine mechanism and, in addition, provide the first evidence of collaboration between an HIV-1 protein and an HHV-8 protein.

Cell Adhesion↗

PubMed2003

Kaposi's sarcoma-like tumors in a human herpesvirus 8 ORF74 transgenic mouse.

The product of human herpesvirus 8 (HHV-8) open reading frame 74 (ORF74) is related structurally and functionally to cellular chemokine receptors. ORF74 activates several cellular signaling pathways in the absence of added ligands, and NIH 3T3 cells expressing ORF74 are tumorigenic in nude mice. We have generated a line of transgenic (Tg) mice with ORF74 driven by the simian virus 40 early promoter. A minority (approximately 30%) of the Tg mice, including the founder, developed tumors resembling Kaposi's sarcoma (KS) lesions, which occurred most typically on the tail or legs. The tumors were highly vascularized, had a spindle cell component, expressed VEGF-C mRNA, and contained a majority of CD31(+) cells. CD31 and VEGF-C are typically expressed in KS. Tumors generally (but not always) occurred at single sites and most were relatively indolent, although several mice developed large visceral tumors. ORF74 was expressed in a minority of cells in the Tg tumors and in a few other tissues of mice with tumors; mice without tumors did not express detectable ORF74 in any tissues tested. Cell lines established from tumors expressed ORF74 in a majority of cells, expressed VEGF-C mRNA, and were tumorigenic in nude mice. The resultant tumors grew rapidly, metastasized, and continued to express ORF74. Cell lines established from these secondary tumors also expressed ORF74 and were tumorigenic. These data strongly suggest that ORF74 plays a role in the pathology of KS and confirm and extend previous findings on the tumorigenic potential of ORF74.

Animals↗