Gap suppression at a Lifshitz transition in a multi-condensate superconductor

In multi-orbital materials, superconductivity can exhibit several coupled condensates. In this context, quantum confinement in two-dimensional superconducting oxide interfaces offers new degrees of freedom to engineer the band structure and selectively control the occupancy of 3d orbitals by electrostatic doping. Here, we use resonant microwave transport to extract the superfluid stiffness of the (110)-oriented LaAlO₃/SrTiO₃ interface in the entire phase diagram. We provide evidence of a transition from single-condensate to two-condensate superconductivity driven by continuous and reversible electrostatic doping, which we relate to the Lifshitz transition between 3d bands based on numerical simulations of the quantum well. We find that the superconducting gap is suppressed while the second band is populated, challenging Bardeen-Cooper-Schrieffer theory. We ascribe this behaviour to the existence of superconducting order parameters with opposite signs in the two condensates due to repulsive coupling. Our findings offer an innovative perspective on the possibility to tune and control multiple-orbital physics in superconducting interfaces.

Competition between electron pairing and phase coherence in superconducting interfaces

In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin-orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high-energy dxz/dyz bands in the quantum well, more apt to host superconductivity.

Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices

The recent development in the fabrication of artificial oxide heterostructures opens new avenues in the field of quantum materials by enabling the manipulation of the charge, spin and orbital degrees of freedom. In this context, the discovery of two-dimensional electron gases (2-DEGs) at LaAlO₃/SrTiO₃ interfaces, which exhibit both superconductivity and strong Rashba spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on the realisation of a field-effect LaAlO₃/SrTiO₃ device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage. We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition. Magneto-transport measurements show that the Rashba coupling constant increases linearly with the interfacial electric field. Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates.

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.

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.

[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.

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.

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.

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.

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.

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.

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.

[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.

Inhibition of sandfly fever Sicilian virus (Phlebovirus) replication in vitro by antiviral compounds

Sandfly fever Sicilian virus (SFSV) was used in our laboratory to screen antiviral substances active toward viruses of the Bunyaviridae family. Antiviral activity was estimated by the reduction of the cytopathic effect of SFSV on infected Vero cells. Cytotoxicity was evaluated by determining the inhibition of Trypan blue exclusion. The specificity of action of each tested compound was estimated by the selectivity index (CD50/ED50). Selectivity indices of human recombinant interferon-alpha (IFN alpha) (Roferon and Introna), iota-, kappa- and lambda- carrageenans, fucoidan and 6-azauridine were much higher than that of ribavirin, the only antiviral substance which has been previously investigated for its inhibitory effects on Phlebovirus infections. Other compounds showed significant antiviral activity: glycyrrhizin, suramin sodium, dextran sulphate and pentosan polysulphate. All these compounds caused a concentration-dependent reduction in the virus yield. Ribavirin, 6-azauridine and IFN alpha have been shown to inhibit a late step of the virus replicative cycle, whereas glycyrrhizin and suramin sodium were active at an early step and the sulphated polysaccharides inhibited adsorption of SFSV on the cells. The antiviral compounds selected in this study as specific inhibitors of in vitro replication of SFSV are promising candidates for the chemotherapy of haemorrhagic fevers caused by viruses of the Bunyaviridae family. The combination of IFN alpha and ribavirin, which showed a synergistic antiviral effect, should be evaluated for the treatment of these infections.

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.

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.

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.

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.

Studies on mechanism of action of glycyrrhizin against hepatitis A virus replication in vitro

Glycyrrhizin (GL) achieved a concentration-dependent inhibition of the replication of hepatitis A virus (HAV) in PLC/PRF/5 cells. GL has been shown to inhibit an early stage of the HAV replication. GL was not virucidal and had no measurable effect on the adsorption of [3H]uridine-labelled virions to cells. GL inhibited HAV penetration of the plasma membrane as measured by the amount of infective virus no longer neutralizable by specific antibody over time.

[Antiviral effect of recombinant interferon-alpha on hepatitis A virus replication in human liver cells]

Two recombinant interferons-alpha (IFNs-alpha) were assayed for their antiviral effect on hepatitis A virus (HAV) replication in the human hepatoma cell line PLC/PRF/5. IFN alpha-2a and IFN alpha-2b resulted in concentration-dependent inhibition of HAV antigen expression and HAV infectivity at non toxic concentrations. Their selectivity indices, calculated as the ratio of the dose that reduced the number of viable cells to 50% (CD50) to the effective dose that inhibited 50% of viral antigen expression (ED50) were > 1000. Recombinant IFN-alpha emerged, from the present study, as a promising candidate for chemotherapy of hepatitis A.

Immunoaffinity purification of an oxidase-activating cytosolic complex from bovine neutrophils

An oxidase activating complex from the cytosol of bovine neutrophils was purified by immunoaffinity using a monoclonal antibody specific for the 67 kDa cytosolic factor of oxidase activation (p67) and assayed for production of superoxide O2- in a cell-free system. The complex comprised not only p67, but also the second cytosolic factor of 47 kDa (p47) in equivalent amounts. The p47-p67 complex showed a good oxidase activating potency when added to neutrophil membranes in the presence of GTP-gamma-S and arachidonic acid. A ras-related small G protein could not be immunodetected in the p47-p67 activating complex, indicating that the GTP required for oxidase activation in the cell free system bound to a protein that was either present in catalytic amounts in the cytosolic complex or present in sufficient amount in the membrane fraction.

A generally applicable ELISA for the detection and quantitation of the cytosolic factors of NADPH-oxidase activation in neutrophils

An enzyme-linked immunosorbent assay (ELISA) has been developed using polyclonal antibodies raised against two cytosolic proteins of 47 kDa (p47) and 67 kDa (p67) which behave as activation factors for the superoxide-generating NADPH oxidase of neutrophils at the onset of phagocytosis. These two proteins become associated with the NADPH oxidase complex during activation. This immunological technique has been used to follow the purification steps of p47 and p67. It allows the detection of very small amounts of cytosolic factors in a crude neutrophil extract. It is straightforward and much more sensitive (about 1000 times more) than the classical assay based on the use of a cell-free system of oxidase activation and production of superoxide anion. The percentages of p47 and p67 assessed by ELISA with respect to total cytosolic protein were estimated to amount to 0.13 and 0.20%, respectively. The described method has potential applications for the titration of the cytosolic factors of oxidase activation in autosomal recessive forms of chronic granulomatous disease.

Purification and properties of a functional 47-kilodalton cytosolic factor required for NADPH-oxidase activation in bovine neutrophils

A cytosolic factor of 47 kDa required for activation of the NADPH oxidase, and referred to as p47, has been purified in its functional form from the cytosol of resting bovine neutrophils. The purification was monitored by the determination of the activating potency of p47 in a cell-free system of oxidase activation. The recovery was around 10% and the purification factor greater than 1000. P47 was phosphorylated in vitro by protein kinase A and protein kinase C. [32P] labeled p47 was resolved by isoelectric focusing into two major labeled bands of pI 7.0 and 8.5. Polyclonal antibodies were used to demonstrate that p47 is localized specifically in the cytosol of resting neutrophils, and that, upon activation of neutrophils, p47 is translocated from the cytosol to the membrane.

ADP-ribosylation of a small size GTP-binding protein in bovine neutrophils by the C3 exoenzyme of Clostridium botulinum and effect on the cell motility

A 24-kDa G protein, ADP-ribosylable by exoenzyme C3 from Clostridium botulinum and therefore related to the rho family, was found to be abundantly present in human and bovine neutrophils, and preferentially located in cytosol. In human myeloid HL60 cells, the amount of C3 substrate increased during differentiation of the HL60 cells into granulocytes. The effect of exoenzyme C3 on different functions of bovine neutrophils, namely generation of O-2, degranulation and chemotaxis, has been tested, using electropermeabilized cells. Exoenzyme C3 hardly affected the respiratory burst and the degranulation. In contrast, it efficiently inhibited the spontaneous and chemoattractant-induced motility of the cells and disorganized the actin microfilament assembly.

A study of digestive absorption in four cases of Down's syndrome. Down's syndrome, malnutrition, malabsorption, and Alzheimer's disease

Many data suggest that patients with Down's syndrome (DS) suffer from digestive malabsorption. A fecal test of absorption (search for undigested meat fibers following the ingestion of a measured diet) was conducted in 4 patients with DS. The results point to malabsorption in these patients and support the hypothesis of malabsorption in DS. The etiology of probable malabsorption in DS is discussed. Data are presented suggesting that chronic malnutrition caused by malabsorption could be the cause of the neuropathologic signs of Alzheimer's disease occurring at or slightly before the fourth decade in all patients with DS.

Automated detection of the left ventricular region of interest by means of the extraction of typical behaviors in cardiac radionuclide angiographies

An automated process for the detection of the left ventricular end diastolic contour is defined. The extraction of a pure left ventricular behavior, obtained by the application of the Gram-Schmidt orthogonalization process on a set of vectors representing the three main typical behaviors present in the scintigraphic sequence, yields the synthesis of a new factorial image particularly matched for the extraction of the left ventricular region of interest (ROI). An edge following technique with conditional dilation applied simultaneously on the two binary images resulting from processing the new left ventricular factorial and the average images with a Laplacian operator gives a robust method for the detection of the left ventricular ROI.

Isolation of Rift Valley fever virus from human peripheral blood mononuclear cells: Mauritanian epidemic

During the Mauritanian Rift Valley fever (RVF) epidemic of 1987, peripheral blood mononuclear cells (PBMC) were studied from 78 sick patients. RVF virus (RVFV) was isolated in 5 cases, on Aedes pseudoscutellaris AP61, from both PBMC and serum. Among the 78 cases studied, RVF was proven in 19 cases (24.3%) by specific IgM detection, and in 12 cases (15.3%) by virus isolation from serum, of which 3 also exhibited anti-RVF IgM. Among the 5 PBMC-positive RVFV cases, 2 strains were isolated in the presence of specific IgM from patients presenting with neurologic signs. These observations raised the question as to the role of specific IgM in cellular infection, and suggest that, in certain cases, mononuclear cells may promote RVFV dissemination into brain cells. Further investigations need to be undertaken to determine the RVFV receptor expressed on PBMC membranes.

Filter paper confetti in a serological Rift Valley fever survey

In order to collect epidemiological data about the Rift Valley fever epidemic in Mauritania, we decided to use the filter paper method. The mean recovery level of specific antibodies from filter paper, tested using an immunoenzymatic method, is around one fourth. Taking the mean haematocrit into account, we estimated the extract square with a 1/300 dilution. This method was very useful for epidemiological studies, we observed few patient refusals, but it is necessary to know the exact specificity of the antibodies.

Analytical study of a Rift Valley fever epidemic

Three epidemiological investigations were carried out during and after the 1987 Rift Valley fever (RVF) epidemic in South Mauritania: a case control study, a cross-sectional study in the town of Rosso and a cross-sectional study of villages and encampments around Rosso. The case control study showed an association between epizootic and epidemic outbreaks. The study in Rosso town showed housing and district effects. Also, a medical survey of hospital staff showed the absence of interhuman contamination. The cross-sectional study of villages and encampments around Rosso showed heterogeneity corresponding to a village and ethnic effect. The human epidemic was linked to epizootic disease, but the "vectors" of the disease are not as yet known.

Isolation of the Rift Valley fever virus by inoculation into Aedes pseudoscutellaris cells: comparison with other diagnostic methods

The Rift Valley fever epidemic, which arose in the south of Mauritania beginning on October 15, 1987, enabled a comparative study of different diagnostic methods among humans. During the first two weeks of the epidemic, four parallel methods were used: inoculation into Aedes pseudoscutellaris cells, inoculation intracerebrally into suckling mice, tests by immunocapture of the circulating antigen and detection of type IgM gammaglobulins. Of 370 examined sera, 181 showed at least one marker of recent infection. Inoculation into A. pseudoscutellaris cells was by far the most sensitive and easiest method to use. Detection of the antigen by immunocapture was also a useful technique, since it allowed quick aetiological diagnosis or examination of sera conserved under poor conditions. However, its sensitivity was weak, as it could only detect 26% of positive cases. Vero cells used on a limited scale, in this particular case seemed less sensitive than A. pseudoscutellaris cells. Of a total of 991 sera, 221 diagnoses were reported by discovery of the virus and 271 by detection of specific IgM. In every case, A. pseudoscutellaris cells seemed most appropriate as the system of reference.

Rapid diagnosis of Rift Valley fever: a comparison of methods for the direct detection of viral antigen in human sera

Human sera collected during the 1987 Rift Valley fever (RVF) epidemic in the Senegal River basin were analysed using three enzyme immunoassays to establish the best method for rapid diagnosis of RVF. A biotin-avidin-enhanced antigen detection method utilizing monoclonal antibodies proved most sensitive. Eighty-two viremic human sera were tested, and this assay detected antigen in 29.3% of the samples.

Rift Valley fever among domestic animals in the recent West African outbreak

Severe haemorrhagic disease among the human population of the Senegal River Basin brought the Rift Valley fever virus (RVFV) outbreak of 1987 to the attention of science. As in previous RVFV outbreaks, local herdsmen reported a high incidence of abortion and disease in their livestock. Serum samples were obtained from domestic animal populations from areas near Rosso, the best studied focus of human infection, as well as other areas distant from known human disease. Among animals from the area of high incidence of human disease, antibody prevalence was as high as 85%, with approximately 80% of the sera positive for both RVFV IgG- and viral-specific IgM antibodies. In contrast, human populations in the same area had lower RVFV antibody prevalences, 40% or less, with 90% also being IgM-positive. Sera from livestock in coastal areas 280 km south of the epidemic area were negative for RVFV antibodies. Thus, the detection of RVFV specific IgG and IgM antibodies provided evidence of recent disease activity without the requirement to establish pre-disease antibody levels in populations or individuals and without viral isolation. Subsequently, detection of modest levels of IgG and IgM in the Ferlo region, 130 km south of the Senegal River flood plain, established that RVFV transmission also occurred in another area of the basin. Similar serological testing of domestic ungulates in The Gambia, 340 km south of Rosso, demonstrated antibody prevalence consistent with a lower level of recent transmission of RVFV, i.e., 24% IgG-positive with 6% of the positive sera also having RVFV-specific IgM.

Assessment of an rDNA probe filter hybridization assay for the detection of Rift Valley fever virus RNA in human serum samples from the Mauritanian epidemic

The Rift Valley fever virus (RVFV) epidemic that occurred in southern Mauritania during the 1987 rainy season provided a unique opportunity to test and evaluate a recently developed, M-segment-specific, nucleic acid filter hybridization assay on a large collection of infected human serum samples. It afforded the opportunity to compare the procedure with two other methods for detecting virus: virus isolation and antigen detection by ELISA. The filter hybridization procedure employed a polyethylene-glycol-precipitation and proteinase-K-digestion sample treatment step developed specifically for preparing serum samples for hybridization. The procedure was less sensitive for detecting RVFV in the Mauritanian human viremic samples than in sera from experimentally infected monkeys used to evaluate this procedure. It was also less sensitive than an antigen detection procedure used to test the Mauritanian samples. However, we were able to detect virus RNA in a significant proportion of the virus-isolation-positive samples. Advances in sample preparation, labelling and detection procedures, and hybridization methods will improve the sensitivity, precision and ease of use of this assay and increase its value as a diagnostic tool.

Comparison between vertical parallel hole collimator and 30 degrees rotating slant hole collimator for assessing global and regional left ventricular function by radionuclide angiography

Left ventricular ejection fraction (LVEF) and regional wall motion abnormalities were determined in 40 patients (30 with coronary artery disease and 10 with valvular heart disease) using equilibrium radionuclide angiography. Scintigraphic acquisitions were collected in random order with 2 different collimators as follows: in anterior face (AF), left anterior oblique (25 degrees-45 degrees LAO) and 70 degrees LAO, with a vertical parallel hole collimator (VTC), and in 25 degrees-45 degrees LAO and 65 degrees-80 degrees LAO with a 30 degrees rotating slant hole collimator (RSHC), with the slant of the collimator directed towards the cardiac apex in both projections. Results were compared to contrast ventriculography (CV) performed in the 30 degrees right anterior view (3 segments: anterior, apical, inferior) and in a 60 degrees left anterior oblique view (3 segments: septal, apical and lateral). Radionuclide LVEF in both series was closely correlated with contrast ventriculographic LVEF (r = 0.89, VTC vs CV and r = 0.87, RSHC vs CV, respectively). Regional wall motion analysis was only performed among the 30 patients suffering from coronary heart disease. Eight contrast angiographic studies were normal and 22 abnormal. Global sensitivity and specificity were 100% and 63% with the VTC (3 false positives) and 91% and 87% with the 30 degrees RSHC (2 false negatives and 1 false positive, P = ns). Agreement for the localisation of the regional wall motion abnormalities between CV and radionuclide angiography was 70.6% with the VTC and 71.2% with the RSHC (P = ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative clinical study of a new 17D thermostable yellow fever vaccine

The immunogenicity and the safety of a new heat-stable 17D yellow fever vaccine have been assessed in a randomized comparative study by reference to a non-stabilized vaccine preparation. Seronegative adults were used and 115 and 143 were given the heat-stable and the non-stabilized vaccine, respectively. Fifty two days after the immunization, haemagglutination inhibiting antibodies were found in 77.6 and 73.9% of the vaccinees, neutralizing antibodies in 99.3 and 100% of them. The percentage of seroconversion and the geometric mean of antibody titres were not significantly different. No complaints or adverse reactions in association with the vaccines were recorded. This study demonstrates the high immunogenicity of this new stabilized vaccine whose stability has already been proven.