Persistence of the entire Epstein-Barr virus genome integrated into human lymphocyte DNA

The entire Epstein-Barr virus genome is integrated into Burkitt tumor cell DNA at the terminal direct repeat sequence of the virus. There is no homology between the GC-rich (G, guanine; C, cytosine) terminal repeat and the AT-rich (A, adenine; T, thymine) cell sequences with which it has recombined. More than 15 kilobases of cell DNA have been deleted and 236 base pairs are duplicated at one virus-cell junction site.     

Recognition of HLA-A2 by cytotoxic T lymphocytes after DNA transfer into human and murine cells

A gene coding for the major histocompatibility antigen HLA-A2 was transferred into human HLA-A2 negative M1 cells and murine L cells. Following transfection, these cells expressed molecules at the cell surface that are biochemically indistinguishable from HLA-A2 antigens on the human cell line JY from which the HLA-A2 gene was isolated. The M1A2 cells were recognized and lysed by a cytolytic T-cell clone specific for HLA-A2. The transfected L cells which express HLA-A2 in association with human beta 2-microglobulin were not lysed by this T-cell clone. The specific cytolysis of M1A2 cells could be inhibited by monoclonal antibodies to HLA-A2, and monoclonal antibodies to T3, T8, and LFA-1 on cytotoxic T lymphocytes. These results suggest that killing by allospecific T cells requires HLA-A2 antigens as well as other species-specific structures on the target cell surface.     

Infection of normal human epithelial cells by Epstein-Barr virus

Primary cultures of epithelial cells were grown from the tonsils and adenoids of patients with diseases not related to Epstein-Barr virus. The cells could not be infected by Epstein-Barr virus. Fluorescein-labeled Epstein-Barr virus and a cytofluorograph were then used to show that the epithelial cells do not have detectable receptors for the virus. However, implantation with Epstein-Barr virus receptors gave the cells the ability to bind the labeled virus. One to 5 percent of receptor-implanted cells exposed to the transforming B95-8 substrain of the virus expressed Epstein-Barr nuclear antigen. The early and viral capsid Epstein-Barr virus-determined antigens were not detected in the virus-infected cultures. The results show that normal human epithelial cells from the nasopharynx become susceptible to infection by Epstein-Barr virus when the membrane barrier resulting from the lack of viral receptors is overcome by receptor implantation.     

Epstein-Barr viral DNA: infectivity for human placental cells

Purified DNA of Epstein-Barr virus (EBV) is regularly infectious by means of the "calcium" method of transfection. Cultured human placental cells exposed to EBV DNA of two transforming strains, FF41 and B95, produce virus that is capable of converting normal B lymphocytes into established cell lines. After treatment with EBV (FF41) DNA and EBV (HR-1) DNA the placental cells display antigens associated with the productive viral cycle. The placental cells have not developed foci or other signs of morphologic transformation.     

Differential reactivity of human serums with early antigens induced by Epstein-Barr virus

Inoculation of 64-10 or Raji cultures with Epstein-Barr virus derived from the HRI-K clone of the P3J Burkitt's lymphoma line caused abortive infections in most of the lymphoblastoid cells with synthesis of "early antigens" but few, if any, capsids. Antibodies to early antigens were detected by indirect immunofluorescence in serums of many patients with infectious mononucleosis, Burkitt's lymphoma, or nasopharyngeal carcinoma. These antibodies were rarely present in other serums even though some of them showed high titers of antibodies to Epstein-Barr virus when assayed on EB3 Burkitt tumor cells; they also prevented synthesis of early antigens, provided the serums were mixed with the virus prior to inoculation. Antibodies to early antigens possibly reflect current or recent disease processes that are associated with the virus.     

Quiescent T lymphocytes as an inducible virus reservoir in HIV-1 infection

To better understand the basis for human immunodeficiency virus type 1 (HIV-1) persistence and latency, the form in which viral DNA exists in the peripheral T lymphocyte reservoir of infected individuals was investigated. In asymptomatic individuals, HIV-1 was harbored predominantly as full-length, unintegrated complementary DNA. These extrachromosomal DNA forms retained the ability to integrate upon T cell activation in vitro. In patients with acquired immunodeficiency syndrome (AIDS), there was an increase in integrated relative to extrachromosomal DNA forms. By analysis of DNA from patient lymphocyte subpopulations depleted of human lymphocyte antigen-Dr receptor-positive cells, quiescent T cells were identified as the source of extrachromosomal HIV-1 DNA. Thus quiescent T lymphocytes may be a major and inducible HIV-1 reservoir in infected individuals.     

Morphological transformation in vitro of human fibroblasts by Epstein-Barr virus: preliminary observations

Human embryo fibroblasts have undergone morphological transformation in vitro after infection by Epstein-Barr virus. The fibroblasts were maintained in suspension during exposure to the virus, and further treatment with inactivated Sendai virus increased the transformation rate. The transformed cells were large and polygonal and grew in discrete, heaped up, foci.     

Surface structures involved in target recognition by human cytotoxic T lymphocytes

Cloned human cytotoxic T lymphocytes and monoclonal antibodies inhibiting their function (anti-T3A, anti-T4A, and anti-T8A) were used to elucidate the role of T cell surface glycoproteins in cell-mediated lympholysis involving individual classes of gene products of the major histocompatibility complex on target cells. The results indicate that several surface molecules are required for specific target recognition: T3 and T4 on T4+ cytotoxic T lymphocytes and T3 and T8 on T8+ cytotoxic T lymphocytes.     

Gamma interferon synthesis by human thymocytes and T lymphocytes inhibited by cyclosporin A

Cyclosporin A depresses the synthesis of gamma interferon by human thymocytes and T lymphocytes in vitro. This observation is of potential clinical significance because the long-term treatment of transplant patients with cyclosporin A, a widely used immunosuppressive agent, can give rise to B-cell lymphoma resulting from Epstein-Barr virus activation.     

Direct polyclonal activation of human B lymphocytes by the acquired immune deficiency syndrome virus

When B lymphocytes from normal human peripheral blood were incubated for 1 hour with the retrovirus that causes the acquired immune deficiency syndrome (AIDS), the B cells showed marked proliferation and differentiation. Proliferative responses to the virus peaked on day 4 and appeared to be independent of accessory cells. This finding was repeated with three separate viral isolates, one of which was from a patient from Zaire. The magnitude of the observed responses was comparable to that seen with standard polyclonal B-cell activators. This phenomenon may be at least partially responsible for the polyclonal B-cell activation seen in patients with AIDS.     

Commitment of mouse fibroblasts to adipocyte differentiation by DNA transfection

Cells of the mouse cell line 3T3-F442A can be induced by various hormones to differentiate into adipocytes, whereas cells of 3T3-C2, a subclone of 3T3, cannot. However, transfection of DNA from uninduced 3T3-F422A cells into 3T3-C2 cells permits recovery of 3T3-C2 transfectants that differentiate into adipocytes in the presence of insulin. DNA isolated from human fat tissue, when transfected into 3T3-C2 mouse cells, also gives rise to mouse transfectants that are induced to differentiate into adipocytes by the addition of insulin. Apparently, transfection of a trans-regulatory gene (or genes) from 3T3-F442A or human fat cells into 3T3-C2 cells is sufficient to commit 3T3-C2 cells to adipocyte differentiation.     

猪瘟基因疫苗免疫小鼠外周血细胞免疫动态变化研究

应用ＦＡＣＳ、ＭＴＴ法对猪瘟基因疫苗ｐｃＤＳＴ、ｐｃＤＳＷ免疫鼠外围血中ＣＤ４＾＋和ＣＤ８＾＋淋巴细胞数、淋巴细胞的转化功能等动态变化进行了观察。结果：ｐｃＤＳＴ、ｐｃＤＳＷ猪瘟基因疫苗免疫小鼠后,小鼠的外周血淋巴细胞对ＬＰＳ有强烈的反应性,ＣＤ４＾＋细胞数量增加,外周血淋巴细胞ＣＤ８＾＋细胞数量在一段时间内增加。ＣＤ４＾＋和ＣＤ８＾＋细胞数量在免疫后３２天达到高峰后开始下降。表明ｐｃＤＳＴ、ｐｃＤＳＷ质粒免疫小鼠后诱发免疫反应。     

Epstein-Barr virus: inhibition of replication by three new drugs

Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with three human malignancies. Acyclovir [9-(2-hydroxyethoxymethyl)guanine], the first clinically useful drug effective against replication of EBV, is without effect against latent or persistent EBV infection. Three nucleoside analogs, E-5-(2-bromovinyl)-2'-deoxyuridine, 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine, and 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-methyluracil are potent inhibitors of EBV replication in vitro. Moreover, in contrast to the reversibility of viral inhibition by Acyclovir, these three drugs have prolonged effects in suppressing viral replication even after the drugs are removed from persistently infected cell cultures.     

cdc2 gene expression at the G1 to S transition in human T lymphocytes

The product of the cdc2 gene, designated p34cdc2, is a serine-threonine protein kinase that controls entry of eukaryotic cells into mitosis. Freshly isolated human T lymphocytes (G0 phase) were found to have very low amounts of p34cdc2 and cdc2 messenger RNA. Expression of cdc2 increased 18 to 24 hours after exposure of T cells to phytohemagglutinin, coincident with the G1 to S transition. Antisense oligodeoxynucleotides could reduce the increase in cdc2 expression and inhibited DNA synthesis, but had no effect on several early and mid-G1 events, including blastogenesis and expression of interleukin-2 receptors, transferrin receptors, c-myb, and c-myc. Induction of cdc2 required prior induction of c-myb and c-myc. These results suggest that cdc2 induction is part of an orderly sequence of events that occurs at the G1 to S transition in T cells.     

Sequence of the envelope glycoprotein gene of type II human T lymphotropic virus

The sequence of the envelope glycoprotein gene of type II human T lymphotropic virus (HTLV) is presented. The predicted amino acid sequence is similar to that of the corresponding protein of HTLV type I, in that the proteins share the same amino acids at 336 of 488 residues, and 68 of the 152 differences are of a conservative nature. The overall structural similarity of these proteins provides an explanation for the antigenic cross-reactivity observed among diverse members of the HTLV retrovirus family by procedures that assay for the viral envelope glycoprotein, for example, membrane immunofluorescence.     

Identification of a T helper cell-derived lymphokine that activates resting T lymphocytes

A novel lymphokine with apparent molecular size of 10 to 12 kilodaltons is secreted from helper T cell clones within hours after cross-linking their T cell antigen-MHC (major histocompatibility complex) receptors (T3-Ti). This lymphokine, termed interleukin-4A (IL-4A), stimulates resting lymphocytes by binding to a surface component (or components) of the alternative T11 pathway and subsequently by inducing interleukin-2 (IL-2) receptors. The activation process is neither dependent on antigen specificities of the recruited population or the presence of macrophages. It appears, therefore, that IL-4A is a mediator involved in amplifying the T cell immune response.