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G Dapolito

Publications and source records attributed to G Dapolito.

13 recordsLinked to original sources
PubMed2001

Genetic evidence of a role for ATM in functional interaction between human T-cell leukemia virus type 1 Tax and p53.

Recent evidence from several investigators suggest that the human T-cell leukemia virus type 1 Tax oncoprotein represses the transcriptional activity of the tumor suppressor protein, p53. An examination of published findings reveals serious controversy as to the mechanism(s) utilized by Tax to inhibit p53 activity and whether the same mechanism is used by Tax in adherent and suspension cells. Here, we have investigated Tax-p53 interaction simultaneously in adherent epithelial (HeLa and Saos) and suspension T-lymphocyte (Jurkat) cells. Our results indicate that Tax activity through the CREB/CREB-binding protein (CBP), but not NF-kappaB, pathway is needed to repress the transcriptional activity of p53 in all tested cell lines. However, we did find that while CBP binding by Tax is necessary, it is not sufficient for inhibiting p53 function. Based on knockout cell studies, we correlated a strong genetic requirement for the ATM, but not protein kinase-dependent DNA, protein in conferring a Tax-p53-repressive phenotype.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2000

Patterns of genomic sequence diversity among their simian immunodeficiency viruses suggest that L'Hoest monkeys (Cercopithecus lhoesti) are a natural lentivirus reservoir.

Recently, we described a novel simian immunodeficiency virus (SIVlhoest) from a wild-caught L'Hoest monkey (Cercopithecus lhoesti) from a North American zoo. To investigate whether L'Hoest monkeys are the natural host for these viruses, we have screened blood samples from 14 wild animals from the Democratic Republic of Congo. Eight (57%) were found to be seropositive for SIV. Nearly full-length genome sequences were obtained for SIV isolates from three of these monkeys and compared to the original isolate and to other SIVs. The four samples of SIVlhoest formed a distinct cluster in phylogenetic trees. Two of these isolates differed on average at only about 5% of nucleotides, suggesting that they were epidemiologically linked; otherwise, the SIVlhoest isolates differed on average by 18%. Both the level of diversity and the pattern of its variation along the genome were very similar to those seen among isolates of SIVagm from vervet monkeys, pointing to similarities in the nature of, and constraints on, SIV evolution in these two species. Discordant phylogenetic relationships among the SIVlhoest isolates for different genomic regions indicated that mosaic viruses have been generated by recombination, implying that individual monkeys have been coinfected by more than one strain of SIV. Taken together, these observations provide strong evidence that L'Hoest monkeys constitute a natural reservoir for SIV.

Amino Acid Sequence↗
PubMed1999

Simian immunodeficiency virus (SIV) from sun-tailed monkeys (Cercopithecus solatus): evidence for host-dependent evolution of SIV within the C. lhoesti superspecies.

Recently we reported the characterization of simian immunodeficiency virus (SIVlhoest) from a central African l'hoest monkey (Cercopithecus lhoesti lhoesti) that revealed a distant relationship to SIV isolated from a mandrill (SIVmnd). The present report describes a novel SIV (SIVsun) isolated from a healthy, wild-caught sun-tailed monkey (Cercopithecus lhoesti solatus), another member of the l'hoest superspecies. SIVsun replicated in a variety of human T-cell lines and in peripheral blood mononuclear cells of macaques (Macaca spp.) and patas monkeys (Erythrocebus patas). A full-length infectious clone of SIVsun was derived, and genetic analysis revealed that SIVsun was most closely related to SIVlhoest, with an amino acid identity of 71% in Gag, 73% in Pol, and 67% in Env. This degree of similarity is reminiscent of that observed between SIVagm isolates from vervet, grivet, and tantalus species of African green monkeys. The close relationship between SIVsun and SIVlhoest, despite their geographically distinct habitats, is consistent with evolution from a common ancestor, providing further evidence for the ancient nature of the primate lentivirus family. In addition, this observation leads us to suggest that the SIVmnd lineage should be designated the SIVlhoest lineage.

Amino Acid Sequence↗
PubMed1998

Viral genetic evolution in macaques infected with molecularly cloned simian immunodeficiency virus correlates with the extent of persistent viremia.

Genetic evolution of the simian immunodeficiency virus (SIV) envelope glycoprotein was evaluated in a group of six macaques (Macaca nemestrina) infected with the molecularly cloned, moderately pathogenic SIVsm62d. The extent of envelope evolution was subsequently evaluated within the context of the individual pattern of viremia and disease outcome. Two macaques in this cohort developed AIDS by 1.5 years postinoculation (progressors), whereas the remaining four macaques remained asymptomatic (nonprogressors). Compared with the nonprogressor macaques, the two progressor macaques exhibited higher persistent plasma viremia, higher homologous neutralizing antibody titers, and more extensive mutation and evolution in the V1 region of envelope. Although clearly distinct in each of these parameters from the progressors, the four nonprogressors exhibited more individual variability with respect to the extent of persistent viremia and genetic evolution of the V1 region of envelope. The extent of V1 envelope varied from no apparent V1 evolution in a macaque with good viral containment to extensive evolution in one macaque with persistent viremia. This study underscores the critical role of persistent replication in the genetic evolution of SIV.

Amino Acid Sequence↗
PubMed1995

Phylogeny and natural history of the primate lentiviruses, SIV and HIV.

Studies of primate lentivirus phylogeny over the past decade have established a minimum of five related, but genetically distinct, groups of simian immunodeficiency virus (SIV), each originating from a different African primate species. The hypothesis that HIV-2 (and SIVmac) arose by cross-species transmission from sooty mangabeys (Cercocebus atys has been strengthened by a more detailed characterization of the SIVsm/SIVmac/HIV-2 group of viruses. SIV from all four subspecies of African green monkeys (SIVagm) have been characterized with an apparent chimeric genome structure of SIVagm from West African green monkeys. Although these naturally infected primates remain healthy, cross-species transmission to other primate species may result in immunodeficiency, as caused by SIVsm infection of macaque monkeys (Macaca sp.) and recently, SIVagm infection of pig-tailed macaques (M. nemestrina). Studies of variation within infected individuals have been facilitated by adaptation of the techniques of heteroduplex analysis and single-stranded conformational polymorphism of PCR generated fragments.

Africa↗
PubMed1995

Induction of AIDS by simian immunodeficiency virus from an African green monkey: species-specific variation in pathogenicity correlates with the extent of in vivo replication.

Previous studies suggested that simian immunodeficiency viruses isolated from African green monkeys (SIVagm) are relatively nonpathogenic. The report describes the isolation and biologic and molecular characterization of a pathogenic SIVagm strain derived from a naturally infected African green monkey. This virus induced an AIDS-like syndrome characterized by early viremia, frequent thrombocytopenia, severe lymphoid depletion, opportunistic infections, meningoencephalitis, and death of five of eight macaques within 1 year after infection. An infectious clone derived from this isolate reproduced the immunodeficiency disease in pig-tailed (PT) macaques, providing definitive proof of the etiology of this syndrome. Although the virus was highly pathogenic in PT macaques, no disease was observed in experimentally infected rhesus macaques and African green monkeys despite reproducible infection of the last two species. Whereas infection of PT macaques was associated with a high viral load in plasma, peripheral blood mononuclear cells, and tissues, low-level viremia and infrequent expression in lymph nodes of rhesus macaques and African green monkeys suggest that differences in pathogenicity are associated with the extent of in vivo replication. The availability of a pathogenic molecular clone will provide a useful model for the study of viral and host factors that influence pathogenicity.

Animals↗
PubMed1994

Spontaneous substitutions in the vicinity of the V3 analog affect cell tropism and pathogenicity of simian immunodeficiency virus.

Simian immunodeficiency virus (SIV) exists within tissues of infected macaques as a mixture of diverse genotypes. The goal of this study was to investigate the biologic significance of this variation in terms of cellular tropism and pathogenicity. PCR was used to amplify and clone 3'-half genomes from the spleen of an immunodeficiency SIV-infected pig-tailed macaque (Macaca nemestrina). Eight infectious clones were generated by ligation of respective 3' clones into a related SIVsm 5' clone, and virus stocks were generated by transient transfection. Four of these viruses were infectious for macaque peripheral blood mononuclear cells (PBMC) or monocyte-derived macrophages (MDM). Three viruses with distinct tropism for macaque PBMC or MDM were tested for in vivo infectivity and pathogenicity. The ability of these three viruses to infect PBMC and macrophages correlated with differences in infectivity and pathogenicity. Thus, a virus that was infectious for both PBMC and MDM was highly infectious for macaques and induced AIDS in half of the inoculated animals. In contrast, virus that was less infectious for PBMC and not infectious for MDM induced only transient viremia. Finally, a virus that was not infectious for either primary cell type did not infect macaques. Chimeric clones exchanging portions of the envelope gene of the 62A and smH4 molecular clones and a series of point mutants were used to map the determinant of tropism to a 60-amino-acid region of gp120 encompassing the V3 analog of SIV. Naturally occurring mutations within this region were critical for determining tropism and, as a result, pathogenicity of these SIVsm clones.

Amino Acid Sequence↗
PubMed1993

Identification of a new subgroup of SIVagm in tantalus monkeys.

Simian immunodeficiency viruses from African green monkeys (SIVagm) can be classified into three subgroups based upon the species from which they were isolated. The most extensively studied subgroup are composed of SIVagm isolated from vervet monkeys (Cercopithicus pygerythrus). Fewer isolates have been characterized from either grivets (Cercopithicus aethiops) or green monkeys (Cercopithicus sabeus). An additional distinct species of African green monkeys, tantalus monkeys (Cercopithicus tantalus), has not been characterized in terms of SIV infection. A high seroprevalence of SIV-specific antibodies was identified in sera collected from Ugandan tantalus monkeys. SIV was isolated from PBMC (SIVagm/tan), the gag region amplified by polymerase chain reaction, cloned, and sequenced. Based upon gag, SIVagm/tan isolates cluster genetically with other previously recognized SIVagm strains. However, SIVagm from tantalus monkeys forms a distinct genetic subgroup. These data confirm earlier observations of species-specific subtypes of SIVagm viruses and support the hypothesis that these viruses may have coevolved with their host during geographic dispersion throughout Africa.

Amino Acid Sequence↗
PubMed1989

Molecular cloning of SIV from sooty mangabey monkeys.

We derived two infectious molecular clones of SIV from sooty mangabey monkeys (Cercocebus atys) and compared them by restriction enzyme mapping and limited DNA sequencing to other known primate lentiviruses. These analyses show that SIVsmm is closely related to, but distinct from, SIVmac and HIV-2. Our data suggest that SIVmac may have been derived from SIVsmm by cross-species transmission in captivity.

Amino Acid Sequence↗
PubMed1985

Kinetics of synthesis of respiratory syncytial virus glycoproteins.

The synthesis of the two respiratory syncytial (RS) virus glycoproteins (VP66 and VP84) was examined under standard conditions and after treatment with tunicamycin and monensin. The protein backbone for VP66, the fusion protein (F1,2) is cotranslationally glycosylated to form F0, which is cleaved to form F1,2 by 20 min of chase. Monensin treatment inhibited the cleavage of F0 over an 80 min chase period, indicating that this occurred late in the transit of F0 through the Golgi apparatus or after exit from the Golgi apparatus. Tunicamycin treatment resulted in the synthesis of a 50K to 55K unglycosylated F0 which is cleaved to a 40K protein. VP84, the large glycoprotein, contains a protein backbone of only 26K to 30K which is modified by N-linked and probable O-linked glycosylation. Tunicamycin treatment results in the synthesis of a 70K protein (p70) which incorporates [3H]glucosamine and [3H]fucose but not [3H]mannose. Glycosylated precursors varying in mol. wt. from 29K to 45K (p45) are found in infected cells at regular 2K to 3K intervals, producing a 'ladder' effect. The step from p45 to VP84 is severely delayed by monensin treatment thereby enhancing the 'ladder' effect of the precursors.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Chemically synthesized peptides of hepatitis B surface antigen duplicate the d/y specificities and induce subtype-specific antibodies in chimpanzees.

Synthetic peptides, predicted from the nucleotide sequence of the S gene of hepatitis B virus were analyzed in terms of the established specificities of the hepatitis B surface antigen. The analysis indicated that the group-specific alpha antigen is composed of at least three nonoverlapping sequences and that a relatively hydrophilic region of the surface antigen protein, spanning amino acid residues 110-137, specifies the major d and y subtype system. The d/y subtype appears to depend on changes in one or more variable amino acids at positions 127, 131, and 134 of the hepatitis B surface antigen protein. Peptide 49 (consisting of amino acid sequences of the y subtype for the region 110-137), coupled to a carrier protein and mixed with an adjuvant, stimulated a brisk anti-y response in chimpanzees, the relevant model of human response to hepatitis B virus immunization and infection. Experimental challenge with homologous hepatitis B virus resulted in a pattern of partial protection. The results offer promise for the application of chemically synthesized peptides as vaccines in the prophylaxis of hepatitis B virus disease.

Amino Acid Sequence↗