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Biomedical subjects

A Jouan

Publications and source records attributed to A Jouan.

At least 19 recordsLinked to original sources
PubMed2004

In vitro inhibition of Chikungunya and Semliki Forest viruses replication by antiviral compounds: synergistic effect of interferon-alpha and ribavirin combination.

Chikungunya virus (CHIKV) and Semliki Forest virus (SFV) were used in our laboratory to screen active antiviral compounds against viruses of the Alphavirus genus. Antiviral activity was estimated by the reduction of the cytopathic effect of each alphavirus on infected Vero cells and by virus titer reduction. Cytotoxicity was evaluated by determining the inhibition of Trypan blue exclusion in confluent cell cultures and by the evaluation of the inhibitory effect on cell growth. With CHIKV and SFV, the selectivity indices of human recombinant interferon-alpha and iota-carrageenan were much higher than that of ribavirin, which has been previously investigated for its inhibitory effect on alphavirus infections. Compared to ribavirin, 6-azauridine was more effective against CHIKV and showed a similar antiviral activity against SFV. IFN-alpha2b, glycyrrhizin, 6-azauridine, and ribavirin caused a concentration-dependent reduction in the virus yield with CHIKV and SFV. Moreover, the combination of IFN-alpha2b and ribavirin had a subsynergistic antiviral effect on these two alphaviruses and should be evaluated for the treatment of these infections.

Animals↗
PubMed2002

[The Gulf war syndrome].

SPARSE DATA: The Gulf war syndrome remains a little know entity since its first appearance 10 years ago. The objective of our work was to synthesize the data published on the subject in the scientific literature. We analysed the results of American and English epidemiological surveys, from which it was difficult to distinguish the existence of a univocal syndrome. IMPRECISE DEFINITION: It is difficult to give a clear clinical definition of the syndrome, the signs of which fluctuate depending on the studies. Chronic fatigue is frequently associated with the Gulf war syndrome, although some studies have described electrophysiological neurological lesions. NUMEROUS HYPOTHESES: The role of stress, vaccinations and their adjuvants, exposition to neurotoxic substances and weak uranium have been incriminated. We propose that multiple factors be integrated in the research for the genesis of this atypic syndrome.

Animals↗
PubMed2002

Gulf war syndrome: could it be triggered by biological warfare-vaccines using pertussis as an adjuvant?

Several recent epidemiological studies have shown that vaccinations against biological warfare using pertussis as an adjuvant were associated with the Gulf war syndrome. If such epidemiological findings are confirmed, we propose that the use of pertussis as an adjuvant could trigger neurodegeneration through induction of interleukin-1beta secretion in the brain. In turn, neuronal lesions may be sustained by stress or neurotoxic chemical combinations. Particular susceptibility for IL-1beta secretion and potential distant neuronal damage could provide an explanation for the diversity of the symptoms observed on veterans.

Adjuvants, Immunologic↗
PubMed2001

Mosquito cells bind and replicate hepatitis C virus.

Several studies have demonstrated some hepatitis C virus (HCV) replication in lymphocyte and hepatocyte cell lines such as in African green monkey Vero cells. The aim of the present study was to select other cell lines able to bind and replicate HCV. Human hepatoma PLC/PRF/5 cells, human lymphoma Namalwa cells, Vero and mosquito AP61 cells were inoculated with HCV-positive plasma, washed six times and examined for the presence of the viral genome at different times post infection, using an RT-PCR method. Binding of HCV to cells was estimated by HCV RNA detection in cells 2 hr after inoculation and in the last wash of these cells. Successive virus passages in cells were carried out. All the cells studied were able to bind HCV but only AP61 and Vero cells provided evidence of replication and production of infectious virus: virus RNA was detected during 28 days post-infection in four successive virus passages. CD81 molecules, a putative HCV receptor, were detected by cytofluorometric analysis. Vero cells express CD81 molecules whereas these molecules were not detected on AP61 cells. It is suggested that other receptors are involved in HCV binding to Vero and AP61 cells.

Adult↗
PubMed2001

Highly sensitive Taqman PCR detection of Puumala hantavirus.

An increasing number of clinical cases of Hantavirus infections have been reported from various regions in Asia, Europe and North America. Hantaviruses (family Bunyaviridae, genus Hantavirus) are enveloped and possess a single-stranded trisegmented RNA genome of negative polarity. Rodents or insectivores are natural hosts of hantaviruses and transmit the virus to humans chiefly by aerosolisation. These viruses are the causative agents of haemorrhagic fever with renal and pulmonary syndromes. In the northeast of France, Puumala hantavirus causes, every year, more than 150 mild forms of haemorrhagic fever with a renal syndrome known as nephropathia epidemica. Serological tests may lack sensitivity for diagnosing early stages of infection and virus isolation is limited because it grows poorly in cell culture. Since reverse transcription (RT)-PCR amplification is an efficient method for detecting viral genomes in patient specimens, we developed an assay using a Taqman probe and compared it with the classical RT-PCR amplification. To achieve this goal, a Puumala strain was grown in Vero E6 cells and RNA extracted from the culture supernatant. We found that the semi-nested RT-PCR detected a minimal amount of 300 TCID(50) mL(-1), while the Taqman PCR allowed detection of less than 10 TCID(50) mL(-1 )and provided a quantitative analysis.

Animals↗
PubMed2001

Chronic restraint stress induces severe disruption of the T-cell specific response to tetanus toxin vaccine.

Chronic stress is known to induce immunological disorders. In the present study we examined the consequences of chronic restraint stress on the immune response to tetanus toxin in mice. We investigated the repartition of subsets of lymphoid cells in blood and spleen, the functional ability of lymphocytes to proliferate and to produce cytokines, and antibody titres against tetanus toxin following stress. We report discordance of the stimulation index of lymphocytes in the restraint group: the proliferating rate severely decreased following stimulation with a relevant antigen, whereas it increased with mitogen. Thus, we report a decrease in cytokine production with relevant antigen (interferon-gamma and interleukin-10), without a T helper type 1 and 2 secretion imbalance. Moreover, we observed an alteration in the humoral response, including a delay in isotype maturation and an immunoglobulin G1/G2a imbalance.

Animals↗
PubMed2001

Quantitative real-time PCR detection of Rift Valley fever virus and its application to evaluation of antiviral compounds.

The Rift Valley fever virus (RVFV), a member of the genus Phlebovirus (family Bunyaviridae) is an enveloped negative-strand RNA virus with a tripartite genome. Until 2000, RVFV circulation was limited to the African continent, but the recent deadly outbreak in the Arabian Peninsula dramatically illustrated the need for rapid diagnostic methods, effective treatments, and prophylaxis. A method for quantifying the small RNA segment by a real-time detection reverse transcription (RT)-PCR using TaqMan technology and targeting the nonstructural protein-coding region was developed, and primers and a probe were designed. After optimization of the amplification reaction and establishment of a calibration curve with synthetic RNA transcribed in vitro from a plasmid containing the gene of interest, real-time RT-PCR was assessed with samples consisting of RVFV from infected Vero cells. The method was found to be specific for RVFV, and it was successfully applied to the detection of the RVFV genome in animal sera infected with RVFV as well as to the assessment of the efficiency of various drugs (ribavirin, alpha interferon, 6-azauridine, and glycyrrhizin) for antiviral activity. Altogether, the results indicated a strong correlation between the infectious virus titer and the amount of viral genome assayed by real time RT-PCR. This novel method could be of great interest for the rapid diagnosis and screening of new antiviral compounds, as it is sensitive and time saving and does not require manipulation of infectious material.

Animals↗
PubMed2001

Comparison of flavivirus universal primer pairs and development of a rapid, highly sensitive heminested reverse transcription-PCR assay for detection of flaviviruses targeted to a conserved region of the NS5 gene sequences.

Arthropod-transmitted flaviviruses are responsible for considerable morbidity and mortality, causing severe encephalitic, hemorrhagic, and febrile illnesses in humans. Because there are no specific clinical symptoms for infection by a determined virus and because different arboviruses could be present in the same area, a genus diagnosis by PCR would be a useful first-line diagnostic method. The six published Flavivirus genus primer pairs localized in the NS1, NS3, NS5, and 3' NC regions were evaluated in terms of specificity and sensitivity with flaviviruses (including the main viruses pathogenic for humans) at a titer of 10(5) 50% tissue culture infectious doses (TCID(50)s) ml(-1) with a common identification step by agarose gel electrophoresis. Only one NS5 primer pair allowed the detection of all tested flaviviruses with the sensitivity limit of 10(5) TCID(50)s ml(-1). Using a heminested PCR with new primers designed in the same region after an alignment of 30 different flaviviruses, the sensitivity of reverse transcription-PCR was improved and allowed the detection of about 200 infectious doses ml(-1) with all of the tick- and mosquito-borne flaviviruses tested. It was confirmed that the sequenced amplified products in the NS5 region allowed predictability of flavivirus species by dendrogram, including the New York 99 West Nile strain. This technique was successfully performed with a cerebrospinal fluid sample from a patient hospitalized with West Nile virus encephalitis.

Animals↗
PubMed1999

A recombinant Fab neutralizes dengue virus in vitro.

A recombinant Fab that recognizes a neutralizing epitope located in the (296-400) region of protein E of dengue virus was obtained from cloned hybridoma cells secreting the mouse monoclonal antibody (mAb) 4E11. The Fd and light chain antibody genes were amplified by polymerase chain reaction, cloned into the phagemid vector pMad, expressed in bacteria to produce Fab fragments and sequenced. The mAb 4E11, in particular its light chain complementary-determining regions, shared homologies with two other anti-viral mAbs. The affinity of the parental mAb and the cloned Fab to the MalE-E(296-400) fusion protein were shown to be of the same magnitude, i.e. nanomolar. Fab 4E11 neutralization capacity was found between 8 and 4-times or less lower than that of mAb 4E11, depending on serotypes, thus the Fab could have a smaller antiviral activity than the mAb in vitro.

Animals↗
PubMed1997

[Arbovirus infections. From virus, mosquitoes, animals and humans].

Arboviruses occur throughout the world in plants and animals: reptiles, birds and mammals including man. These relatively recent RNA-containing viruses have great evolutionary potential and are a major cause of epidemics. Arboviruses exhibit a dual life cycle involving continual transmission to and from the vertebrate host and arthropod vector which ingests or inoculates the agent during blood meals. Agents belong to many different viral families and represent an important source of emerging diseases. Because of the mode of transmission is vectorial, spread can enhanced by man-made changes in the ecosystem. This risk is often underestimated. The population explosion provides a great opportunity for the progression of these arboviruses.

Animals↗
PubMed1996

Inhibition of the expression of hepatitis A and B viruses (HAV and HBV) proteins by interferon in a human hepatocarcinoma cell line (PLC/PRF/5).

AIMS/METHODS: PLC/PRF/5 is a continuous human hepatocarcinoma cell line whose genome contains integrated HBV DNA and which secretes two of the hepatitis B virus envelope proteins (HBs and PreS2). This line is also susceptible to infection by hepatitis A virus and was therefore used to compare the effects of interferon on protein synthesis of these two viruses and to assess the interactions which occur between them during infection. RESULTS: Results showed that recombinant interferon alpha 2-a inhibited the expression of the two hepatitis B virus envelope antigens (HBs and PreS2) and of the only hepatitis A virus antigen in a dose-dependent fashion. Comparison of the effect of interferon on antigenic protein production of these two viruses, showed stronger inhibition of hepatitis A virus capsid antigen than of hepatitis B virus envelope antigens. Infection with hepatitis A virus also downregulates the expression of the two hepatitis B virus proteins. CONCLUSIONS: Considering the absence of cytotoxic effects from the doses used, this study confirms the relevance of this cellular model for the study of antiviral cytokines in vitro. It also provides a further rationale for the clinical evaluation of the therapeutic potential of interferons in severe hepatitis cases due either to hepatitis A virus alone or to superinfection of hepatitis B virus carriers by hepatitis A virus.

Antigens, Viral↗
PubMed1996

[Fever of unknown origin (FUO) in the camps of Rwandan refugees in the Goma region of in Zaire (September 1994)].

After the outbreaks of cholera, dysenteriae, meningitidis of which the rwandese refugees have been the victims in August and September 1994 in the camps of the Goma's area (Zaïre), the medical teams were confronted with a great number of fevers of unknown origin. In order to explore the possible etiologies, we have conducted a cases/controls study (n = 96). Clinically, the cases occur more frequently than controls headache (p < 0.001), splenomegaly (p = 0.02) and neutropeny (p < 0.001) Serologically, it has been constated non significantly difference between cases and controls, but prevalence of HIV-1 infections (19 and 6%) and arbovirus (23 and 10%) infections are very high. Arbovirosis could explain, partially or associated with HIV and tuberculosis, the presence of these fevers undeterminated more than malaria or typhus epidemic.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Antiviral activity of recombinant interferon-alpha on hepatitis A virus replication in human liver cells.

Human recombinant interferon-alpha (IFN-alpha) was assayed for its antiviral effect on hepatitis A virus (HAV) replication in the human hepatoma cell line PLC/PRF/5. IFN-alpha resulted in concentration-dependent reduction of HAV antigen expression and HAV replication. IFN-alpha had a prophylactic effect, but was still effective when it was added after the infection, even at the end of the first replication cycle. An important increase in 2',5'-oligoadenylate synthetase activity in the IFN-treated human liver cells was observed. The antiviral effect of IFN-alpha could be attributed to the induction of this enzyme. Moreover we have shown that IFN-alpha and glycyrrhizin were synergistic in their antiviral actions against HAV. IFN-alpha emerged, from the present study, as a promising candidate for chemotherapy of severe forms of hepatitis A.

2',5'-Oligoadenylate Synthetase↗
PubMed1995

Small G proteins and the neutrophil NADPH oxidase.

The NADPH oxidase of phagocytic cells is a multimeric enzyme complex activated during phagocytosis. It catalyzes the production of the superoxide anion, precursor of many toxic oxygen metabolites involved in the defense against microorganisms. The enzyme becomes active after assembly on a membrane bound flavocytochrome b of cytosolic factors p47 phox, p67 phox and p40 phox and of low molecular mass GTP binding proteins. This paper reviews recent results concerning the role of two small G proteins, Rac and Rap 1A in oxidase activation. Native prenylated small G proteins are either in the form of a complex in which the GDP bound G protein is associated with a guanine nucleotide dissociation inhibitor, GDI, or in an active GTP bound form able to trigger the activity of its effector. Rac and Rho share a common GDI. As chemotaxis, under Rho control, and oxidase activation, under Rac control, show mutually exclusive signalling pathways, we propose a model where the GDI would switch from one pathway to the other by sequestering either Rac or Rho.

Animals↗
PubMed1994

Activation of the O2(-)-generating NADPH oxidase in a semi-recombinant cell-free system. Assessment of the function of Rac in the activation process.

The neutrophil NADPH oxidase activation factors, p47, p67 and the small guanosine-nucleotide-binding regulatory (G) protein Rac1, were expressed in a baculovirus/insect cell system and purified. In coinfection experiments in which Sf9 cells overexpressed concomitantly p47, p67 and Rac1, the latter was not detected in the p47-p67 complex. The propensity of p47 and p67 to associate together was used to purify recombinant p67 from baculovirus-infected Sf9 cells. 20% of the overexpressed Rac1 in infected Sf9 cells was prenylated and was extracted with low doses of detergent from membranes. Elicitation of full oxidase activity on crude neutrophil membranes using a cell-free system required addition of recombinant p47 and p67, but not that of Rac. In contrast, in the case of KCl-washed membranes, addition of Rac, prenylated or unprocessed, together with p47 and p67 was found to enhance oxidase activation up to fivefold. In all experiments, the amount of added arachidonic acid was optimized. In contrast to prenylated Rac, non-prenylated Rac had to be loaded with guanosine 5'-(3-thiotriphosphate) (GTP[S]) to exhibit full activation efficiency. In the cell-free system used, Rac was shown to be the mediator of the GTP[S] effect. The results suggest that the plasma membrane of resting neutrophils contains a sufficient amount of prenylated Rac for efficient oxidase activation. We therefore propose that Rac has a membrane-associated role and helps to dock and position p47 and p67 on the flavocytochrome b component of the oxidase complex.

Animals↗