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Biomedical subjects

K Hennessy

Publications and source records attributed to K Hennessy.

33 records · Page 2Linked to original sources
PubMed1986

Leukocyte migration inhibition demonstrates a human T-cell response to a membrane protein expressed in latent Epstein-Barr virus infection.

Leukocyte migration inhibition tests show that lymphocytes of Epstein-Barr virus-seropositive individuals recognize a Raji cell membrane antigen and a membrane protein encoded by Epstein-Barr virus in latently infected cells. Antiserum against the latter blocks the leukocyte migration inhibition triggered by both preparations, suggesting that the two antigens are associated with the same protein complex.

Antigens, Surface↗
PubMed1986

Expression of the Epstein-Barr virus nuclear protein 2 in rodent cells.

A 3.0-kilobase-pair Epstein-Barr virus (EBV) DNA segment necessary for lymphocyte immortalization encodes at least part of a nuclear protein (EBNA2) which is characteristically expressed in latently infected, immortalized cells. A 1.5-kilobase open reading frame within this DNA segment has now been inserted into a murine leukemia virus (MuLV)-derived expression vector (pZIP-NEO-SV(X)1) which provides for transcription of heterologous DNA but not for translational start. Transfection of the recombinant DNA into NIH 3T3 cells resulted in expression of a full-sized EBNA2 which localized to the cell nucleus. Significant new evidence is thereby provided that this 1.5 kilobase open reading frame includes a translational start site and encodes the entire EBNA2 protein. Transfection of the recombinant DNA into a helper cell line (psi am22b) providing amphotropic MuLV-packaging functions resulted in the release of a recombinant MuLV carrying the EBNA2 gene. This recombinant virus can infect rodent cells and convert them to stable EBNA2 expression. Rat-1 cells infected with the MuLV EBNA2 recombinant expressed EBNA2 and grew more rapidly in medium supplemented with 1 or 0.5% fetal calf serum than did Rat-1 cells infected with MuLV vector lacking EBNA2. The Rat-1 cells expressing EBNA2 remained contact inhibited, anchorage dependent, and nontumorigenic in nude mice. Different EBV isolates have one of at least two EBNA2 alleles. Despite divergence between the two alleles, a human serum recognized the prototype EBNA2 allele (EBNA2A) as well as the variant EBNA2B allele characteristic of some Burkitt tumor EBV isolates. The EBNA2B allele was also expressed from the MuLV-derived vector. The reproducible expression of EBNA2A or EBNA2B from these recombinant vectors will facilitate analysis of the EBNA2A and EBNA2B phenotypes.

Animals↗
PubMed1985

A second nuclear protein is encoded by Epstein-Barr virus in latent infection.

A region of the Epstein-Barr virus (EBV) genome that is important in inducing cell proliferation includes a single long open reading frame. Part of this open reading frame has been fused to the lacZ gene and expressed in Escherichia coli. Antisera to the fusion protein identify a protein in the nuclei of latently infected growth-transformed lymphocytes and in Burkitt tumor cells grown in vitro. This nuclear protein is encoded by a different virus-gene than that which encodes the previously described EBV nuclear antigen, EBNA.

Animals↗
PubMed1985

A third viral nuclear protein in lymphoblasts immortalized by Epstein-Barr virus.

Most sera from patients with rheumatoid arthritis as well as some sera from normal Epstein-Barr virus (EBV)-infected people detect a 140-kDa protein on immunoblots of EBV-infected lymphoblasts. The 140-kDa protein is a nuclear protein characteristic of latent EBV infection. Sera reactive with this protein identify a distinctive globular nuclear antigen. Although the 140-kDa protein is encoded by EBV, it is not encoded by genes that encode the two previously described EBV nuclear antigens (EBNA) or the latent-infection membrane protein. The 140-kDa protein is therefore designated EBNA3. The EBV genes, including the gene encoding EBNA3, that are characteristically expressed in latent infection are likely to play a role in the maintenance of persistent latent viral infection or in the cell proliferation caused by virus infection.

Antigens, Viral↗
PubMed1985

Biochemistry of latent Epstein-Barr virus infection and associated cell growth transformation.

There is sufficient knowledge of the biochemistry of Epstein-Barr virus (EBV) persistence and gene expression in latent growth-transforming infection and of the persistence and expression of other oncogenic viruses to permit interesting and possibly useful comparisons. Most smaller oncogenic viral genomes usually persist solely as integrated DNAs despite their ability to circularize. Papilloma and hepatitis viruses may persist as episomes, and parts of their genomes may integrate. Usually, only the oncogenic fragment of adenovirus DNA is integrated into cell DNA. In contrast, the entire EBV genome persists in cells as an episome or as integrated DNA. Thus, EBV may have novel mechanisms to maintain its complete genome as an episome or as a complete integrated virus DNA. Three viral genes are expressed in latently EBV-infected growth-transformed cells, each of which encodes one RNA and one protein. Two of the proteins are probably nuclear DNA-binding proteins; the third is probably a membrane protein. Thus, the repertoire of genes expressed is similar in complexity and intracellular distribution to that expressed by papova and adenoviruses in cellular transformation. The papova and adenovirus-transforming genes are partially analogous to retrovirus oncogenes. This similarity cannot as yet be extended to EBV. There is no homology at the DNA-sequence or protein-sequence level between EBV and other viral or cell oncogenes. Thus, it remains important to pursue analysis of the EBV-transforming genes. Identification of these genes is a first step in discerning their function in latent growth-transforming cell infection. Parts of each of these genes are being made in bacteria. The bacterial products enable us to make antisera that are specific for each of the viral proteins. These antisera can also be used to identify the viral proteins within latently infected growth-transformed cells or within cells stably expressing transfected virus genes. The antisera can also be used to study the association of Epstein-Barr nuclear antigen (EBNA) 1 and 2 with DNA and of the lymphocyte-determined membrane antigen (LYDMA) with the cell membrane. The three genes must be introduced into nontransformed cells to determine whether, alone or in combination, they are sufficient to accomplish cell growth transformation.

Amino Acid Sequence↗
PubMed1984

A membrane protein encoded by Epstein-Barr virus in latent growth-transforming infection.

The nucleotide sequence of an Epstein-Barr virus gene expressed in latently infected growth-transformed cells is known to include a long open reading frame containing a 33-base-pair repeat element. A bacterial fusion protein constructed from a portion of the reading frame and Escherichia coli beta-galactosidase was used to produce sera in rabbits against the previously unidentified gene product. The viral protein detected with these sera in latently infected cells varies in size with the number of copies of the DNA repeat element. Translation of the RNA in vitro yields a protein of similar size. As expected from its primary sequence, the protein is a membrane protein. Immunofluorescence studies with the rabbit antisera suggest that the protein is in the plasma membrane. Thus, this protein could be the lymphocyte-determined membrane antigen (LYDMA) responsible for the generation of T-cell immunity to latently infected cells.

Cell Membrane↗
PubMed1984

U2 region of Epstein-Barr virus DNA may encode Epstein-Barr nuclear antigen 2.

Sequence analysis of the U2 regions of the B95-8 and AG876 Epstein-Barr virus (EBV) isolates reveals divergence within a long open reading frame previously identified as encoding 1.5 kilobases of the 3' end of a viral RNA expressed in latently infected, growth-transformed, B-lymphocyte cell lines. Differences among EBV isolates within the U2 open reading frame are shown to correlate with differences in an EBV nuclear antigen, EBNA2. B95-8, W91, Raji, Cherry, and Lamont EBV isolates have similar U2 domains and encode similar-size EBNA2 proteins, while AG876, Jijoye, and P3HR-1 have variant or absent U2 domains and variant or absent EBNA2 proteins. The AG876 U2 open reading frame and EBNA2 protein are both shorter than those of B95-8. These data indicate that the U2 open reading frame encodes EBNA2.

Animals↗
PubMed1984

Identification and characterization of a cellular protein that cross-reacts with the Epstein-Barr virus nuclear antigen.

A 62,000-dalton (62K) cell protein reacts with antisera to the 72K polypeptide of the Epstein-Barr virus nuclear antigen (EBNA) in immunoblots. This protein was initially detected in EBNA-negative as well as EBNA-positive cell lines with anti-EBNA-positive human sera. A monoclonal antibody raised against the 72K EBNA and an antiserum from a rabbit immunized with the glycine-alanine domain of EBNA also reacted with the cellular protein. The cellular protein was partially purified from Epstein-Barr virus genome-positive and -negative cell lines. Absorption experiments identified a shared antigenic determinant between the 72K EBNA and 62K cellular protein. A comparison of the 62K protein and EBNA by protease digestion did not reveal similar peptides.

Antibodies, Monoclonal↗
PubMed1983

Simple repeat array in Epstein-Barr virus DNA encodes part of the Epstein-Barr nuclear antigen.

The size of the Epstein-Barr virus (EBV) nuclear antigen (EBNA) in cells infected with different EBV isolates varies directly with the size of the EBV triplet repeat array, IR3. The isolate with the largest IR3 fragment has approximately 170 more codons than the isolates with the smallest IR3 fragment; it encodes an EBNA which is approximately 17,000 daltons larger than the smallest EBNA. The EBV IR3 encodes part of a 2-kilobase exon of a latently infected cell messenger RNA which must be translated into a repetitive amino acid domain of EBNA.

Animals↗
PubMed1983

One of two Epstein-Barr virus nuclear antigens contains a glycine-alanine copolymer domain.

A gene fusion between an Epstein-Barr virus (EBV) triplet nucleotide repeat array (IR3), which has homology to host DNA, and lacZ was used to demonstrate that this EBV sequence encodes part of the Epstein-Barr nuclear antigen (EBNA). The IR3 sequence is translated into a glycine-alanine copolymer that reacts with anti-EBNA human sera. Some EBV-immune human antisera recognize a second intranuclear protein that is also specific for latently infected cells and is designated EBNA2. EBNA2 is not related to EBNA1 because the molecular mass of EBNA2 is 82 kilodaltons, whereas that of EBNA1 varies from 68 to 85 kilodaltons among cells transformed by different EBV isolates; also EBNA2 does not contain the copolymer domain of EBNA1.

Animals↗
PubMed1982

The biology and chemistry of Epstein-Barr virus.

Epstein-Barr virus (EBV) is the human prototype of a family of closely related herpesviruses of Old World primates. These agents probably evolved and spread among the Old World primates since the divergence of apes from monkeys about 30 million years ago. Although the DNAs of the EBV family have no sequence homology to other herpesviruses, there are some features in common with other herpesviral genomes. EBV DNA is unusual in having five tandem direct repeat elements which divide the genome into five unique sequence domains. The tandem direct repeats at the ends of the linear virion DNA probably mediate circularization of the viral DNA to form the circular episomal viral DNA which is characteristic of EBV-infected cells. In latent transforming infection, messenger RNAs are encoded by three widely separate regions of the EBV genome. The remainder of the viral genome encodes many RNAs and proteins which are expressed in productive infection. Early and late viral genes are intermixed along the full length of EBV DNA.

Animals↗