Different H-2 subregions influence immunization against retrovirus and immunosuppression

Friend murine leukaemia virus complex (FV) causes an immunosuppressive retrovirus-induced disease. In certain mouse strains, FV shows striking similarities to human immunodeficiency virus (HIV) infection in man in that infected mice have severe T-cell immunosuppression but also develop virus-neutralizing antibodies incapable of eliminating infected cells. Previously we noted the influence of mouse major histocompatibility complex (H-2) genes on both FV-induced immunosuppression and on ability to protect mice against FV by immunizing with a vaccinia-Friend murine leukaemia helper virus (F-MuLV) envelope (env) recombinant virus. Here we show that different subregions of H-2 are involved in susceptibility to virus-induced immunosuppression (H-2D subregion) and protective immunization with a recombinant vaccinia virus (H-2K or I-A subregions). Thus, susceptibility to virus-induced immunosuppression does not preclude protection by vaccinia-Friend immunization. The mechanism of protection seems to involve priming of immune T cells, and not initial induction of neutralizing antibodies or cytotoxic T lymphocytes (CTL) (ref.2). Subsequent virus challenge generates a secondary response, resulting in appearance of IgG antibodies and CTL. In human HIV infection there could also be host genetic influences on elements of disease pathogenesis, such as immunosuppression, and on the success of T-cell priming by potential protective vaccines.     

Inhibition of retroviral protease activity by an aspartyl proteinase inhibitor

Retrovirus protease is an enzyme that cleaves gag and gag-pol precursor polyproteins into the functional proteins of mature virus particles. The correct processing of precursor polyproteins is necessary for the infectivity of virus particles: in vitro mutagenesis which introduces deletions into the murine leukaemia virus genome produces a protease-defective virus of immature core form and lacking infectivity. A therapeutic drug effective against disease caused by retrovirus proliferation could likewise interfere with virus maturation. The primary structure has so far been determined for the protease of avian myeloblastosis virus, and of murine, feline and bovine leukaemia viruses. Amino acid sequencing of the retrovirus proteases, either after their purification or from prediction from the nucleotide sequence, shows that they possess the Asp-Thr-Gly sequence characteristic of the aspartyl proteinases. In this report we show that retrovirus proteases belong to the aspartyl proteinase group and demonstrate an inhibition by the aspartyl proteinase-specific inhibitor, pepstatin A, on the activity of bovine leukaemia, Moloney murine leukaemia and human T-cell leukaemia virus proteases.     

Expression of endogenous murine leukaemia viruses in AKR/J streaker mice

MICE of the AKR/J strain show high rates of spontaneous thymic lymphoma and are chronically infected with murine leukaemia viruses. Total thymectomy in young mice of this strain results in a marked decrease in the incidence of leukaemia. The finding of athymic mutant mice on the AKR/J background (referred to as streaker mice) is of importance in the study of genetic factors which influence virus expression and leukaemogenesis. Here we report that mice of both normal and mutant genotypes vary in the expression of a particular class of murine leukaemia virus. This lower virus expression in conjunction with the absence of a thymus leads to a lower tumour incidence in streaker mice.     

Infective transmission and characterisation of a C-type virus released by cultured human myeloid leukaemia cells.

A C-type virus isolated from long term cultures of myeloid cells from a patient with acute myelogenous leukaemia is infectious for a wide variety of cells. The establishment of chronically infected cells enabled us to characterise the virus by biological, immunological, and biochemical tests. The virus is closely related to the simian sarcoma-associated virus isolated from a woolly monkey fibrosarcoma.     

The Hardy-Zuckerman 2-FeSV, a new feline retrovirus with oncogene homology to Abelson-MuLV

There is substantial evidence that oncogenes (v-onc) of acute transforming retroviruses have been acquired by transduction of cellular genes (c-onc) with retroviruses. Feline leukaemia virus (FeLV)-associated feline fibrosarcomas have proven to be extremely useful for the isolation of acute transforming retroviruses of a mammalian species. Three different v-onc genes have been identified in five acute transforming feline retroviruses. The Susan McDonough feline sarcoma virus (SMFeSV) contains the oncogene fms (ref. 4). The Snyder-Theilen (ST) and Gardner-Arnstein (GA) FeSVs contain the oncogene fes (ref. 4), which is homologous to the oncogene fps of the avian sarcoma viruses FSV, RRCII, PRCIV and 16L (refs 7, 8). The v-onc sequences of the Parodi-Irgens (PI) FeSV have recently been found to be homologous with the v-sis sequences of the simian sarcoma virus. We report here the isolation of another acute transforming feline retrovirus from a naturally occurring feline fibrosarcoma, designated the Hardy-Zuckerman 2 feline sarcoma virus (HZ2-FeSV) and demonstrate that the HZ2-FeSV and Abelson murine leukaemia virus (A-MuLV) have homologous oncogenes.     

Proviral sequences of baboon endogenous type C RNA virus in DNA of human leukaemic tissues.

Hybridisation of RNA from a baboon endogenous type C RNA virus to DNA from tissues of leukaemic patients indicates that a virus of this type is horizontally transmitted among humans. DNA from several patients with leukaemia hybridised 70% of the hybridisable RNA from baboon endogenous type C RNA virus (BaEV) and yielded hybrids of high tm, whereas DNA from normal human tissues hybridised only 23% of the BaEV RNA, and the tm of these hybrids was lower.     

Continuous in vitro generation of multipotential stem cell clones from src-infected cultures

A molecular recombinant of Rous sarcoma virus and murine amphotropic leukaemia virus, src(MoMuLV), where the avian src oncogene has been placed under the influence of a murine virus promoter sequence, has been reported. Infection of long-term marrow cultures with this virus led to a dramatic change in the relative numbers of stem cells, granulocyte-macrophage progenitor cells and mature cells found in normal haematopoietic cell development. However, although the balance between self-renewal, differentiation and development was disturbed, injection of the cultured cells into irradiated syngeneic recipients did not lead to the development of leukaemia. Thus, although the control had been 'loosened', the host regulatory mechanisms were sufficient to impose a restraint on unlimited growth of the cells. We now show that the stem cells from the src-infected cultures show a remarkably increased capacity for self-renewal in vitro in situations which are inimical to the maintenance of self-renewal in normal uninfected stem cells and that self-renewal/differentiation can be modified by the culture conditions.     

Identification and nucleotide sequence of a human locus homologous to the v-myc oncogene of avian myelocytomatosis virus MC29

Avian myelocytomatosis virus MC29 is a replication-defective acute leukaemia virus which induces a variety of tumours in chickens including sarcomas, renal and hepatic carcinomas, and myelocytomatosis. The oncogenic potential of the virus is mediated by the gene v-myc, acquired from sequences (c-myc) present in normal uninfected chicken DNA. Sequences closely related to chicken c-myc have been highly conserved throughout evolution, from Drosophila to vertebrates. The hypothesis that c-myc may be involved in neoplastic transformation has been strengthened by the finding that B-cell lymphomas induced in chickens by avian leukosis virus (ALV) are often associated with increased expression of c-myc resulting from integration of the ALV provirus adjacent to the c-myc gene. More recently, it has been demonstrated that the malignant human cell line HL-60, derived from the peripheral blood leukocytes of a patient with acute promyelocytic leukaemia, expresses elevated levels of myc-related mRNA associated with an amplification of the c-myc gene. To explore the relationship of the human cellular myc gene with the corresponding viral oncogene from MC29, and to provide a framework for the analysis of the mechanism and significance of c-myc amplification in human tumours, we have isolated and determined the nucleotide sequence of a genomic clone prepared from a normal human library which contains all domains sharing homology with v-myc.     

Unique cell lines harbouring both Epstein-Barr virus and adult T-cell leukaemia virus, established from leukaemia patients

Members of three distinct classes of animal virus have been associated with naturally occurring neoplasias in man: Epstein--Barr virus (EBV), a DNA virus belonging to herpesvirus group, papillomavirus, and a novel human RNA (retro) virus, human T-cell leukemia virus or adult T-cell leukaemia (ATL) virus. We have established seven continuous cell lines from ATL patients and 0.1-7% of these cells consistently express ATL-specific antigens (ATLA). EBV-associated nuclear antigen (EBNA) is also found in more than 90% of these cells. We have cloned cells from two of these lines and show here that both ATLA and EBNA were present in the same B-cell clone carrying surface immunoglobulin (sIg).     

Isolation of HTLV-transformed B-lymphocyte clone from a patient with HTLV-associated adult T-cell leukaemia

The human T-cell leukaemia/lymphoma virus (HTLV) is an exogenous retrovirus which has been associated with adult T-cell leukaemia/lymphoma (ATL). This malignancy of T lymphocytes is endemic to southern Japan, the West Indies, and to a lesser extent, the Middle East, Central Africa and the southeastern United States. ATL cells from patients of diverse geographical origins have been found to be infected with HTLV-1 (ref.6). HTLV is normally tropic for mature T lymphocytes, especially those expressing the helper-inducer surface antigen phenotype (OKT4 or Leu-3-positive), and the neoplastic T cells infected with HTLV generally express receptors for T-cell growth factor (detected by reactivity with anti-Tac antibody). However, we report here the isolation of a HTLV-infected B-lymphocyte clone from the peripheral blood of a patient with ATL. This clone is cytogenetically normal and is not infected with Epstein-Barr virus (EBV). Co-culture of cells from this clone with cord blood lymphocytes resulted in transmission of HTLV and the immortalization of either T or B lymphocytes. These results suggest that HTLV may be associated with a broader range of host cells than previously recognized.     

Severe immunodeficiency disease induced by a defective murine leukaemia virus

Different classes of retroviruses have been shown to induce immunodeficiency diseases in various animal species. These animal models may provide an insight into our understanding of AIDS but, with the exception of one strain of feline leukaemia virus, the determinants of pathogenicity have not yet been mapped to these viral genomes. The immunodeficiency-inducing feline leukaemia virus is replication-defective, harbouring the determinant of pathogenicity within its env sequences. We have studied the Duplan strain of murine leukaemia virus which induces, in C57BL/6 mice, a severe immunodeficiency disease with striking similarities to human AIDS. We have identified the aetiological agent of this murine immunodeficiency disease as another defective retrovirus, with a genome of 4.8 kilobases. Molecular cloning and sequencing of this DNA showed that the pol and env genes have been deleted, but that the complete gag region has been conserved and has a novel sequence encoding the p12 protein. As with the feline leukaemia virus, these results provide evidence for the role of defective retroviruses in inducing immunodeficiency and facilitate the study of the mechanisms underlying the pathogenesis of retrovirus-induced immunodeficiency syndromes, including AIDS.     

JD病毒基因组片段的克隆和序列分析

扩增并克隆了ＪＤ病毒的ｇａｇ 基因片段（位于３００ｎｔ～５６４ｎｔ,编码基质蛋白ＭＡ）和ｐｏｌ基因片段（位于３４６７ｎｔ～３６９１ｎｔ,编码反转录酶ＲＴ）,测定其序列并同ＢＩＶ、ＢＦＶ 和ＢＬＶ 的相应基因进行比较．所建立的方法能够特异性扩增ＪＤＶ序列,适用于ＪＤＶ的检测     

Abelson murine leukaemia virus protein is phosphorylated in vitro to form phosphotyrosine

The Abelson murine leukaemia virus protein (P120) can become phosphorylated in vitro by [gamma-32P]ATP. The protein has been purified from cell membranes to the point that in specific conditions virtually all of the incorporated 32P is in P120. The reaction is stimulated by Mn2+ and Mg2+ but not Ca2+ and is very rapid even at 0 degrees C. The phosphate is linked to P120 at tyrosine, a linkage not previously reported for a phosphorylation reaction. Phosphorylation may be involved in the transforming activity of viruses that cause leukaemia as well as sarcomas.     

Temperature-sensitive mutant of avian erythroblastosis virus suggests a block of differentiation as mechanism of leukaemogenesis.

A temperature sensitive mutant has been isolated for the first time from a replication defective acute leukaemia virus, AEV. In vivo, at 41 degrees C, the mutant shows a reduced leukaemogenic potential. In vitro, in erythroblasts transformed at 35 degrees C, haemoglobin synthesis can be induced by a shift to 41 degrees C. This indicates that the continuous expression of a viral gene product is necessary to maintain the undifferentiated state of the virus-transformed leukaemia cells.     

A new acute transforming feline retrovirus and relationship of its oncogene v-kit with the protein kinase gene family

A new acute transforming feline retrovirus, the Hardy-Zuckerman 4 feline sarcoma virus (HZ4-FeSV), has been isolated from a feline fibrosarcoma. The viral genome of HZ4-FeSV contains a new oncogene designated v-kit, has the structure 5' delta gag-kit-delta pol-delta env 3' and specifies a gag-kit polyprotein of relative molecular mass 80,000. The predicted kit amino-acid sequence displays partial homology with tyrosine-specific protein kinase oncogenes. HZ4-FeSV appears to have been generated by transduction of feline c-kit sequences with feline leukaemia virus.     

In vitro synthesis of infectious DNA of murine leukaemia virus.

DNA synthesised in vitro by purified virions of murine leukaemia virus is infectious. Neither RNA nor protein is required for infectivity. Transfection with reverse trancriptase product shows a single-hit dose response and results in the production of complete, infectious virus.     

Three new types of viral oncogene of cellular origin specific for haematopoietic cell transformation.

The RNAs of seven replication-defective leukaemia virus (DLV) strains contain three types of unique sequences, which correlate with the capacity of a given virus strain to transform erythroblasts, macrophage-like cells and myeloblasts, respectively. These sequences, termed erb, mac and myb, have their counterparts in the normal DNA of avian and mammalian species. Our results indicate that DLVs represent recombinants between a common 'vector' related to a chicken endogenous virus and one of three types of cellular gene possibly involved in haematopoietic differentiation.     

家蚕质多角体病毒基因部分序列克隆及分析

根据BmCPV(Bombyx mori cytoplasmic polyedrosis virus)核酸片段4的末端序列设计一对引物，通过RT－PCR扩增获得多条DNA片段，对其中占优势的约740bp的片段进行切胶回收，克隆到pGEM-Teasy载体上并进行序列测定。与GenBank中的database比较分析表明，该序列与已登录的序列同源性很低，并与呼肠弧病毒科其它种的对应核酸序列有较大差异。本实验证明所测序列为一新序列。