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H Agut

Publications and source records attributed to H Agut.

At least 109 records · Page 6Linked to original sources
PubMed1992

Susceptibility of HIV-1 isolates to zidovudine: correlation between widely applicable culture test and PCR analysis.

Thirteen isolates of human immunodeficiency virus type 1 (HIV-1) obtained in coculture with peripheral blood lymphocytes were tested for in vitro susceptibility to zidovudine (ZDV). Seven isolates were obtained from patients who had never been treated with ZDV and six from patients receiving the drug. The seven isolates from untreated patients and four of six from treated patients were susceptible to ZDV. The two isolates from the patients treated for the longest periods were resistant to the drug. The presence of mutations at critical positions of the reverse transcriptase gene was investigated by direct sequencing of polymerase chain reaction (PCR)-amplified DNA and four isolates were found to be mutants. An isolate from an untreated patient showed a change at residue 70 of the reverse transcriptase and an isolate from a patient treated for 4 months showed a change at residue 67. A change at residue 215 was found only for the two drug-resistant isolates, which correlated with the results obtained by Larder et al. using isolates from MT-2 cell cocultures. These results suggest that any HIV isolate provided by conventional coculture could be confidently tested for ZDV susceptibility in order to study the emergence of resistance during long-term therapy.

Base Sequence↗
PubMed1991

[Study of human immunodeficiency virus in the cerebrospinal fluid. Value and limitations].

Several markers of HIV infection can be detected in the cerebrospinal fluid, including viruses that are replicable in cell cultures, viral antigens and, at an early stage, stigmas of immunization against the virus. Some studies make a distinction between HIV isolated in cerebrospinal fluid and in serum. Cerebrospinal HIV isolates differ from serum isolates in their macrophage tropism, their antigenicity and their low cytotoxicity, but there is little difference in their capacity for replication. Studies aimed at finding virological markers to diagnose HIV-induced neurological lesions have given discordant results. Longitudinal studies are necessary to determine prognostic markers. New techniques, such as amplification by polymerase chain reaction, will perhaps provide new data.

Biomarkers↗
PubMed1991

Genetic variability affects the detection of HIV by polymerase chain reaction.

Nine isolates of HIV-1 obtained from Congolese AIDS patients were amplified by the polymerase chain reaction (PCR) using primer pairs and oligomer probes derived from the HIV-1 LAV-BRU (BRU) sequence. When compared to BRU, two isolates exhibited a significant decrease of PCR efficiency with a given primer pair. Moreover, the DNA amplified from two other isolates did not hybridize with the corresponding probe despite efficient PCR. Base substitutions were detected in the regions of proviral genomes involved in oligonucleotide annealing and were assumed to be responsible for the failure of both amplification and probing. Our data confirm that the genetic variability of HIV-1 may reduce the efficiency of PCR as a diagnostic procedure, especially in the case of African isolates.

Base Sequence↗
PubMed1991

Virological markers in the cerebrospinal fluid from HIV-1-infected individuals.

We analysed 127 specimens of cerebrospinal fluid (CSF) from 118 HIV-1-infected individuals at different stages of infection. Intrathecal antibody synthesis was evident in 23 samples tested and was more frequently directed against HIV than against rubella virus, herpes simplex virus, varicella zoster virus or cytomegalovirus. HIV was isolated from only 14% of the 127 CSF specimens, but from 82% of CSF-paired blood samples. HIV antigen was detected in 12% of CSF specimens and 44% of paired plasma samples. Twenty specimens analysed using the polymerase chain reaction (PCR) detected proviral DNA in 75% of CSF specimens. The low rate of virus recovery from CSF was caused by neither the freezing of specimens prior to culture nor therapy. In contrast, virus isolation from CSF was significantly associated with CSF cell count. Virus isolation and antigen detection in CSF were not correlated with either the Centers for Disease Control disease stage or the peripheral CD4+ lymphocyte count, whereas viraemia was significantly associated with a low CD4+ lymphocyte count. Moreover, virus isolation and antigen detection in CSF were not associated with symptoms of subacute HIV encephalitis, suggesting that these markers are not of potential value in the diagnosis of HIV-specific neurologic complications. The value of PCR in this field merits further investigation.

AIDS Dementia Complex↗
PubMed1991

Several groups among human herpesvirus 6 strains can be distinguished by Southern blotting and polymerase chain reaction.

Eight human herpesvirus 6 (HHV-6) strains were studied by Southern blot and polymerase chain reaction. DNA from infected cells was digested by a panel of restriction enzymes and hybridized with cloned BamHI fragments corresponding to about 30% of the HHV-6 strain SIE genome. In parallel, this DNA was amplified by polymerase chain reaction using pairs of primers derived from the strain SIE nucleotide sequence. Subsequently, amplification products were analyzed by hybridization, digestion with restriction endonucleases, and partial nucleotide sequencing. Overall results indicated that all strains were closely related to one another. However, concordant differences in restriction patterns allowed at least two groups to be distinguished, typified by strains SIE and HST, respectively. Differences between the two groups were found to reflect a limited number of punctual changes in nucleotide sequences. These results strengthen the idea of a unique HHV-6 species with genetic polymorphism. In addition, this study provides useful markers for the diagnosis and molecular epidemiology of HHV-6 infections.

Base Sequence↗
PubMed1991

Correlations between virus infection and pathogenicity in humans.

Infection is not synonymous with disease. Infection refers to the multiplication or the persistence of a virus in tissues while pathogenicity refers to the emergence of disease in the infected host. Pathogenicity is the result of a competition between the growth of the virus and the host response to infection, and its genesis involves many intricate factors. Consequently, most viruses of medical interest exhibit a wide spectrum of pathogenicity ranging from asymptomatic infection to lethal disease. The study of pathogenicity is far more complex than the recognition of infection. Cell cultures, animal models and molecular biology investigations have provided substantial insights both into the virulence of viruses and the susceptibility of the host. However, the prediction of disease often remains hazardous whereas the detection of a virus can now be obtained in most cases by the combination of classical methods with recent molecular techniques. Therefore the prevention of virus diseases transmitted by biologicals is logically founded on the prevention of virus infections, which implies a constant adaptation of safety control procedures to the rapid evolution of knowledge in medical virology.

Biological Products↗
PubMed1990

Simplified test for detecting the resistance of herpes simplex virus to acyclovir.

The detection of herpes simplex virus (HSV) antigen by means of an enzyme amplified ELISA was investigated for rapid screening of acyclovir (ACV) resistance. Vero cell monolayers were inoculated in the presence of different concentrations of ACV. When cytopathic effect was present, the culture supernatants were tested by ELISA. The absorbance values were found to correlate with the results of virus yield and plaque reduction assays. The comparison between absorbance values obtained in the presence of 10 microM ACV and in the absence of drug provided the basis for a simplified sensitivity test. The use of a single ACV concentration allowed discrimination between ACV-resistant and ACV-sensitive reference strains, the detection of ACV-resistant virus mixed in the proportion of 10% with ACV-sensitive virus, and a study of the emergence of an ACV-resistant virus population in serial samples taken from experimental rabbit keratitis. The simplified susceptibility assay is a sensitive and convenient method for rapid screening of HSV resistance to ACV.

Acyclovir↗
PubMed1990

Perspectives in antiviral chemotherapy.

The current progress in antiviral therapy is related to our better understanding of the viral multiplication, with potential targets for specific antiviral action at each step of the multiplication cycle inside the infected cell. Amantadine and Rimantadine are anti-influenza A drugs interfering with the penetration and the release of the virus. Most of the other antiviral drugs which are clinically available have the same target in common, namely the viral DNA polymerase. This holds true for modified nucleosides such as Acycloguanosine (Acyclovir), DHPG, Adenine-Arabinoside, Azidothymidine as well as pyrophosphate derivatives such as phosphonoformic acid. Unfortunately the antiviral chemotherapy must confront 3 obstacles: 1) a possible interference with the normal cellular metabolism, leading to residual cytotoxic side effects; 2) the genetic variability of the viruses, producing drug-resistant mutants and 3) the inability of any antiviral chemotherapeutic agent known to date to eradicate latent viral infection. A new approach of the control of latent infection is suggested with anti sense oligonucleotides of hybridons.

Animals↗
PubMed1989

A point mutation in the poliovirus polymerase gene determines a complementable temperature-sensitive defect of RNA replication.

We have previously described the isolation of a RNA- temperature-sensitive (ts) mutant of poliovirus type 1, ts035, after chemical mutagenesis by 5-fluorouracil. The ts defect of ts035 correlated with defective RNA replication, since the two characters corevert in the case of spontaneous revertants. The alteration of a trans-acting replication function of ts035 was suggested by significant rescue following mixed infection with another ts mutant, ts221, or with wild-type virus. Protein synthesis appeared normal at 39 degrees (nonpermissive temperature) in shift-up experiments and no defect of RNA elongation was evidenced when the activity of replication complexes or purified polymerase was measured at 39 degrees. These results provide circumstantial evidence that the initiation of ts035 RNA synthesis at 39 degrees is impaired. Molecular cloning of the ts035 genome allowed us to construct a recombinant virus with the same ts phenotype as ts035, by the transfer of a fragment of the mutant polymerase gene into the wild-type genome. Two mutations were present in this region of the ts035 genome but the determination of nucleotide sequences in the case of ts035 revertants indicated that only the substitution from A to G at nucleotide 7256 was necessary for the ts phenotype. This mutation replaces Asn 426 by an Asp in polypeptide 3D, the viral polymerase.

Base Sequence↗
PubMed1989

Substitution in the poliovirus replicase gene determines actinomycin D sensitivity of viral replication at elevated temperature.

A series of ts+ revertants and recombinants derived from a temperature-sensitive plurimutant of poliovirus type 1 showed identical plaquing efficiencies at 37 degrees C and at 39 degrees C and exhibited similar yields and plaque morphology to wild-type virus. However, these viruses were characterized by clear inhibition of viral RNA synthesis at 39 degrees C, as measured by uridine incorporation in the presence of actinomycin D. Similarly, virus yields were decreased by one log in the presence of actinomycin D during infection at 39 degrees C. All the ts+ recombinants formed between temperature-sensitive mutants of poliovirus that were inhibited by actinomycin D carried a glutamine----histidine modification at residue 170 of their viral replicase (polypeptide 3D), due to a G----U substitution at nucleotide 6496. Inhibition of viral growth was increased by pretreatment of cells with actinomycin D for 3 h prior to infection, suggesting that actinomycin D sensitivity could reflect an increased dependence of viral RNA replication on host factor(s).

Dactinomycin↗
PubMed1989

[Prospects and current data in antiviral chemotherapy].

The advances achieved in our knowledge on the virus multiplication cycle and the challenge created by the advent of AIDS have resulted in a rational development of new antiviral agents. However, antiviral chemotherapy is hindered by several obstacles: (1) most antiviral drugs are cytotoxic, with the exception of acyclovir which owes its remarkable safety to its activation by the thymidine kinase of the herpes simplex viruses and of the varicella-zoster virus; (2) the risk of selecting resistant strains by mutation of viral enzymes is the unavoidable price to pay for the specificity of new antiviral agents which interfere with these enzymes; so far, this risk seems to apply only to immunocompromised patients; (3) latent viral infection, defined as the lack of active multiplication of the virus, cannot be eradicated by the antiviral drugs available at present since these drugs are inhibitors of viral multiplication. However, anti-sens oligonucleotides could, at least in theory, be used to treat this type of infection which is not limited to the Retroviridae or Herpesviridae families. Finally, antiviral drugs active against life-threatening infections that are as common as rabies and the severe forms of measles or viral hepatitis remain to be discovered.

Antiviral Agents↗