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Interference with simian virus 40 DNA replication by adenovirus type 2 during mixed infection of monkey cells.

Infection of monkey cells with human adenovirus (Ad) is abortive, but the infection can be enhanced by coinfecting with simian virus 40 (SV40). However, in the coinfected monkey cells, Ad interferes strongly with SV40 DNA biosynthesis. This interference was found to be a reproducible, delicately controlled phenomenon that was proportional to the multiplicity of infection of Ad and dependent on the active expression of the Ad genome. Newly synthesized SV40 DNA was not broken down in cells after delayed superinfection with Ad, and several early events of SV40 infection such as adsorption, penetration, uncoating, induction of cellular DNA synthesis, and enhancement of Ad infection were not markedly influenced by Ad-mediated interference. It is unlikely that interference is simply due to competition between SV40 and Ad for metabolites, enzymes, or replication sites. The interference effect could be partially neutralized by an increase in the multiplicity of coinfecting SV40 or by an increase in the time interval between SV40 infection and Ad coinfection. Interference was shown to be due to the activity of an Ad early gene product. However, the detailed mechanism of this Ad interference is still unclear.

Adenoviruses, Human↗

A novel nonnucleoside inhibitor specifically targets cytomegalovirus DNA maturation via the UL89 and UL56 gene products.

3-Hydroxy-2,2-dimethyl-N-[4([[5-(dimethylamino)-1-naphthyl]sulfonyl]amino)-phenyl]propanamide (BAY 38-4766) is a novel selective nonnucleoside inhibitor of cytomegalovirus (CMV) replication with an excellent safety profile. This compound and structural analogues inhibit neither viral DNA synthesis nor viral transcription and translation. Accumulation of dense bodies and noninfectious enveloped particles coincides with inhibition of both concatemer processing and functional cleavage at intergenomic transitions, pointing to interference with viral DNA maturation and packaging of monomeric genome lengths. Resistant virus populations, including a murine CMV (MCMV) isolate with 566-fold-decreased drug sensitivity, were selected in vitro. Sequencing of the six open reading frames (ORFs) known to be essentially involved in viral DNA cleavage and packaging identified mutations in ORFs UL56, UL89, and UL104. Construction of MCMV recombinants expressing different combinations of murine homologues of mutant UL56, UL89, and UL104 and analysis of drug susceptibilities clearly demonstrated that mutant ORFs UL89 exon II (M360I) and M56 (P202A I208N) individually confer resistance to BAY 38-4766. A combination of both mutant proteins exhibited a strong synergistic effect on resistance, reconstituting the high-resistance phenotype of the in vitro mutant. These findings are consistent with genetic mapping of resistance to TCRB (2,5,6-trichloro-1-beta-D-ribofuranosyl benzimidazole) (P. M. Krosky et al., J. Virol. 72:4721-4728, 1998) and provide further indirect evidence that proteins encoded by UL89 and UL56 function as two subunits of the CMV terminase. While these studies also suggest that the molecular mechanism of BAY 38-4766 is distinct from that of benzimidazole ribonucleosides, they also offer an explanation for the excellent specificity and tolerability of BAY 38-4766, since mammalian DNA does not undergo comparable maturation steps.

Animals↗

Bridging the gap. Bringing new antiretroviral medications into the clinic.

Highly active antiretroviral therapy (HAART) is a strategy in which clinicians introduce potent combinations of antiretroviral medications early in the course of HIV infection. The intent is to suppress viral replication as completely as possible to forestall irreversible immune system damage. Antiretroviral agents fall into two major classes reverse transcriptase inhibitors and protease inhibitors. Each class interferes with viral replication at a different point in the viral life cycle. Recent research findings demonstrate clearly that antiretroviral treatment should begin as soon as the patient is willing and able to take the multidrug regimens. The best strategy for meeting the challenge of antiretroviral resistance is prevention. If you completely halt viral replication with potent therapy, the development of resistant strains is prevented.

Acquired Immunodeficiency Syndrome↗

Wheat dwarf virus Ac/Ds vectors: expression and excision of transposable elements introduced into various cereals by a viral replicon.

The maize transposon Activator (Ac) and in vitro-generated nonautonomous derivatives thereof [Ac delta or Dissociation (Ds) elements] were inserted into the genome of a geminivirus of graminaceous plants, wheat dwarf virus, at a site that does not interfere with viral replication. These recombinant viral genomes were introduced into wheat, maize, and rice protoplasts, where rapid and efficient excision of Ac was observed. Excision was detected only in vectors in which, after transfection, the virus could replicate. This result is not restricted to the autonomous Ac; excision of Ds elements was also induced by transposase activity provided in trans by plasmids expressing the cDNA of Ac. The potential of this combination of a transposon with a viral replicon for plant molecular genetic engineering is discussed.

Base Sequence↗