Force measurements between emulsion droplets-ssDNA conjugates: a new tool for medical diagnostics.

We describe here a new system involving direct force measurements between biomolecules that could be used in biomedical diagnostics. The method consists in the use of magnetic emulsion droplets bearing immobilized single stranded DNA fragments (ssDNA, Deoxyribo Nucleic Acid). The immobilized ssDNA fragments are able to recognize complementary DNA molecules via specific hydrogen binding (hybridization process). The ssDNA used in this study are 32 bases oligonucleotides functionalized at their 5' extremity with biotin and then immobilized onto the magnetic nanodroplets via interactions with streptavidin previously chemically grafted onto the nanomagnetic support. The aim of this work is to evaluate the possible detection of captured nucleic acid targets via single force measurements as an alternative to classical ELOSA (Enzyme Linked Oligo Sorbent Assay). The obtained results are discussed mainly in terms of electrostatic interactions.

Detection of mucosal human papillomavirus types 6/11 in cutaneous lesions from transplant recipients.

Transplant recipient develop multiple cutaneous lesions. We have identified human papillomavirus (HPV) DNA in these lesions using three different techniques, namely polymerase chain reaction (PCR), in situ hybridization, and Southern blotting. By PCR, HPV DNA was detected in 43 of 62 samples: warts, actinic keratoses, Bowen's disease, and squamous cell carcinomas. Surprisingly, HPV 6/11, usually associated with mucosa, were frequently found in benign, premalignant, and malignant cutaneous lesions (30/43 cases). Some of these biopsies were simultaneously tested by in situ hybridization and/or Southern blotting. By in situ hybridization, HPV 6/11 were identified in two warts and one squamous cell carcinoma among 29 tissue specimens tested. Of the three samples examined by Southern blotting, HPV 6/11 were detected in one squamous cell carcinoma. In patients from a control population cutaneous biopsies did not exhibit HPV types 6/11 except in Bowen's disease; HPV types 1 or 2 were mainly found in benign warts. These findings suggest that in transplant recipients, HPV can lose their specificity towards mucosa or cutaneous epithelium. The significance of the presence of HPV 6/11 in skin lesions remains unknown.

Cell cultures and associated retroviruses in multiple sclerosis. Collaborative Research Group on MS.

Retroviral particles associated with reverse transcriptase (RT) activity in cell-cultures from MS patients have been reported by different groups. Cell-cultures have been used for the study and characterization of the corresponding retroviral genome which we have shown is related to ERV9 in the pol region. Previously unpublished details of a study with monocyte cultures are presented together with observations on leptomeningeal and choroid-plexus cultures. The generation of self-transformed cultures after inhibition of interferon, followed by the loss of retroviral expression and recurrent apoptosis, is analyzed. Retroviral particles with RT-activity are produced in monocyte cultures with an apparent correlation with MS disease activity. However, though leptomeningeal and choroid plexus cells from MS can be passaged for a limited period, their evolution in vitro is not compatible with stable retroviral expression. These culture limitations greatly hampered progress on the elucidation of the retroviral genome sequence.

Comparison of several techniques for the detection of apoptotic astrocytes in vitro.

Implication of apoptosis in numerous physiological and pathological processes has resulted in the development of numerous methods to detect apoptosis, but none of them is adapted to all cell types. In this study, we induced apoptosis on murine immortalized astrocytes with urine from multiple sclerosis (MS) patients. Among techniques allowing the detection of apoptotic cells, only a few are adapted to adherent cells such as astrocytes. We compared several techniques (propidium iodide labelling and flow cytometry analysis, TUNEL and annexin V labelling in immunofluorescence, DNA ladder, ELISA tests to detect nucleosomes) in order to choose the method best adapted to our adherent cellular model and to discuss their practicability for the detection of apoptosis on adherent cells. For technical course, propidium iodide labelling followed by flow cytometry analysis as a quantitative technique, and TUNEL in IF (easier and quicker than propidium iodide) as a semiquantitative test were both retained as best adapted to our case. Moreover, in our model, we have observed that phosphatydilserine externalization and DNA fragmentation were concomittant after induction of apoptosis. Techniques studied in this article would allow an enlarged study of the apoptotic mechanism in several pathologies by culture of adherent cells sensitive to apoptosis in vitro.

Construction and expression of a modular gene encoding bacteriophage T7 RNA polymerase.

A modular gene that encodes T7 RNA polymerase (T7 RNAP) and consists of cassettes delimited by unique restriction sites was constructed. The modular and wild-type genes of T7 RNAP were cloned into a vector designed to express His-tagged proteins. The modular and wild-type genes provided the same level of protein expression (i.e., T7 RNAP represented up to 30% of the total protein in Escherichia coli strain BL21). Purification of both proteins by immobilized metal ion affinity chromatography (IMAC) resulted in similar yields (700-800 microg of enzyme per 20 ml of culture) and purity (>95%) as indicated by Coomassie blue staining, Western blotting and the absence of detectable contaminating nuclease activities. Both proteins exhibited identical efficiency in transcription assays, and their specific activities (about 200 U/microg) were close to that of a commercial T7 RNAP preparation. The modular gene provides a useful tool for cassette directed mutagenesis of T7 RNAP.

Gliotoxicity, reverse transcriptase activity and retroviral RNA in monocyte/macrophage culture supernatants from patients with multiple sclerosis.

In investigating a possible link between a novel retroviral agent (provisionally called MSRV), recently characterised in multiple sclerosis (MS), and the neuropathology of MS, it was found that there was a significant correlation between gliotoxicity and reverse transcriptase activity in monocyte/macrophage culture supernatants (MMCS) unique to MS patients. MMCS from healthy controls and patients with other neurological diseases did not display either gliotoxicity or reverse transcriptase activity. The observed gliotoxic effect was an initial, intermediate filament network disorganization and subsequent cell death which was specific to astrocytes and oligodendrocytes. The reverse transcriptase activity and MSRV-specific RNA were observed during the first 2 weeks of culture in MMCS from patients with active MS. The further elucidation of the molecular form(s) of this gliotoxic factor and its original source may be crucial in elucidating important etiopathogenic mechanisms in MS.

Prevalence and persistence of antibody titers to recombinant HIV-1 core and matrix proteins in HIV-1 infection.

Numerous studies have established the correlation between antibodies to the core protein p24 of HIV-1 and the progression of the acquired immunodeficiency syndrome. In this study, we analyzed the immune response to two recombinant gag proteins, p24 and p17, in order to evaluate their diagnostic or prognostic significance. Immune response to the immunodominant domain of the transmembrane glycoprotein gp41 was used as a reference. Sera collected from individuals from France and Burundi (Central Africa) at various CDC stages of HIV-1 infection were tested using three sandwich enzyme-linked immunoassays developed with a synthetic peptide corresponding to the immunodominant domain of gp41, SP gp41, or recombinant p24 and p17 cloned and expressed in Escherichia coli. These assays allowed detection of titer antibodies to the three cited antigens. Antibodies to SP gp41 were detected in every HIV-1-positive patient from France and Burundi, generally at a high and stable level. Results obtained with p24 confirmed the value of antibodies to p24 as a prognostic marker only in European and North American populations, since the African population had very high levels of these antibodies even at an advanced stage of the disease. They also confirmed that initial antibody response to p24 is more predictive of outcome than antibody titer change over time. Although antibodies to p17 decline during progression to AIDS, they are frequently absent in French patients at early, asymptomatic stages and therefore could not be used as a prognostic marker. In contrast, antibodies to p17 are significantly less common in African patients with AIDS when compared with symptomless HIV-1-infected African individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunomagnetic concentration of antigens and detection based on a scanning force microscopic immunoassay.

Scanning Force Microscopy has already been shown to be a convenient and rapid method for sensitive antigen detection and quantification. Here, we describe different improvement steps brought to a TSH Scanning Force Microscopic ImmunoAssay (SFMIA), each of them aiming to solve a previous limitation of the solid phase test format and leading to a significant sensitivity enhancement. First, superparamagnetic nanoparticles conjugated to monoclonal anti alphaTSH antibodies were used for the specific TSH capture step. Their magnetic properties allowed easy separation of the complexes obtained from relatively large reaction volumes by application of a High Gradient Magnetic Field System. As a consequence, complex formation could proceed in a stirred solution, which greatly enhances binding rates compared to previous 'static' conditions of solid-phase reactions. It was established that, despite their small size, magnetic complexes could be moved over short distances by a NdFeB magnet magnetic field. This property was exploited to overcome diffusion barrier and boundary layer constraints and to drive magnetic complexes through the liquid, towards anti-betaTSH antibodies immobilized on silica wafers. Finally, we significantly increased the complex number/surface area by a stepwise reduction of the biospecific solid phase area. The proposed steps permitted a 3-fold improvement in the TSH SFMIA dynamic range. Moreover, as little as 0.02 pg/ml (0.1 nIU/ml or 0.8 amol/ml) of TSH could be detected using 1 ml sample volumes. This is over 100 times more sensitive than the current performance of commercialized automated systems.

Continuous RT-PCR using AMV-RT and Taq DNA polymerase: characterization and comparison to uncoupled procedures.

A continuous reverse transcription polymerase chain reaction (RT-PCR) procedure was designed with all reaction components included in a single tube prior to thermal cycling. This procedure was compared to uncoupled RT-PCR procedures wherein the addition of reagents was separated. In the latter, in particular, conditions for reverse-primer annealing and cDNA synthesis were investigated. The two RT-PCR approaches were compared in the detection of singly spliced and multiply spliced human immunodeficiency virus type 1 (HIV-1) mRNs. The avian myeloblastosis virus reverse transcriptase and Taq DNA Polymerase were used in the continuous procedure under the compromised condition wherein the two enzymes were active in the same buffer. Reverse transcription was carried out at an elevated temperature of 50 degrees C to overcome problems of mRNA secondary structures that could inhibit the reaction. The continuous procedure was found to be as specific and efficient as the best uncoupled procedure. The procedure was shown to be reliable and to have the sensitivity to detect one HTLV-IIIB-infected H9 cell in a million uninfected H9 cells.

Detection of multiple types of human papillomavirus in a giant condyloma from a grafted patient. Analysis by immunohistochemistry, in situ hybridisation, Southern blot and polymerase chain reaction.

Immunosuppressed patients such as transplant recipients are known to develop multiple lesions suggestive of human papillomavirus (HPV) infection. A giant anal condyloma was obtained from a transplant patient; several fragments taken from different areas were examined for the presence of HPV DNA using in situ hybridisation, polymerase chain reaction (PCR) and Southern blot. Typical koilocytes were seen in routinely stained tissue sections, suggesting an HPV infection; furthermore, group specific HPV antigen was detected in one of four frozen fragments. Different results were obtained by in situ hybridisation according to the fragment tested. HPV types 6/11 were detected in each of the five fragments, frozen or fixed in Bouin's or formalin solutions. However, the number of HPV DNA positive cells and the intensity of the reaction greatly varied with the specimen. HPV 16 and 18 probes also reacted positively with the sample fixed in formalin; a stronger signal was observed with HPV 18 in one large focus than with HPV 16. HPV type 5 was detected in a few isolated cells of two frozen fragments. With the Southern blot technique, the profile of an HPV 6/11 was seen only in one of two frozen fragments; in this case, the bands were intense. A slight positive reaction was also obtained in one frozen fragment with HPV 16 probe. Four frozen fragments were analyzed with PCR: HPV 6/11 was detected in each fragment; HPV 18 was detected in the four samples but with different intensities; HPV types 5 and 16 did not show any positive signal. In conclusion, the lesion is an example of infection with several HPV types, demonstrated by three different techniques. This suggests the need for careful dermatological or colposcopic follow-up of transplant recipients, in order to prevent possible malignant transformation of anogenital lesions.

Chromosomal distribution and coding capacity of the human endogenous retrovirus HERV-W family.

Some genomic elements of the multicopy HERV-W endogenous retroviral family have been previously identified in databases. One of them, located on chromosome 7, contains a single complete open reading frame (ORF) putatively encoding an envelope protein. We have experimentally investigated the genomic complexity and coding capacity of the HERV-W family. The human haploid genome contains at least 70, 100, and 30 HERV-W-related gag, pro, and env regions, respectively, widely and heterogeneously dispersed among chromosomes. Using in vitro transcription-translation procedures, three putative HERV-W gag, pro, and env ORFs were detected on chromosomes 3, 6, and 7, respectively, and their sequences analyzed. A 363 amino acid gag ORF containing matrix and carboxy-terminal truncated capsid domains encoded a putative 45-kDa protein. No gag-pro ORF was found, but a pro sequence containing a DTG active site was detected. Finally, the previously described 538 amino acid HERV-W env ORF, located on chromosome 7, was shown to be unique and encoded a putative 80-kDa glycosylated protein. Proteins of molecular mass identical to the one obtained by an in vitro transcription-translation procedure were detected in human placenta, using anti HERV-W Gag- and Env-specific antibodies. The absence of an HERV-W replication-competent provirus versus the existence of HERV-W-related Gag and Env proteins in healthy human placenta is discussed with respect to particle formation, physiology, and pathology.

Phylogeny of a novel family of human endogenous retrovirus sequences, HERV-W, in humans and other primates.

A novel human endogenous retrovirus, HERV-W, has been characterized on the basis of multiple sclerosis-associated retrovirus (MSRV) probes. We have analyzed the phylogenetic distribution of HERV-W in humans and other primate species. As HERV-W presents a C/D chimeric nature and is largely composed of deleted elements, Southern blots were performed using gag, pol, env, and LTR probes. The relative complexities observed for gag, pol, env, and LTR regions were similar in humans, apes, and Old World monkeys, the minimal number of bands observed after Southern blot analysis being 25, 50, 10, and at least 100, respectively. The HERV-W family entered the genome of catarrhines more than 25 million years ago.

Neuron-specific enolase as a marker of neuronal lesions during various comas in man.

The detection of neuron-specific enolase in biological fluids has been investigated as an indirect marker of neuronal damage in man. This protein was measured by a sandwich enzymoimmunoassay in serums and cerebrospinal fluids from patients with consciousness disorders of various aetiologies. Neuron-specific enolase level was significantly increased in sera from patients with comas resulting from anoxemia, head injury, septic state, cirrhosis and fulminant hepatitis. On the other hand, patients with meningitis (affection not normally accompanied with neuronal lesion) exhibited no change of this marker level. The statistical analysis of our results suggests that, in neurological disorders, the neuron-specific enolase levels in cerebrospinal fluid could have some prognostic value. The correlation between its level in cerebrospinal fluid and in serum was also demonstrated. Neuron-specific enolase increase in biological fluids thus represents a useful and promising marker to biochemically characterize various strokes possibly resulting in neuronal damage.

Quantitative and discriminative detection of individual HIV-1 mRNA subspecies by an RNAse mapping assay.

HIV-1 genes are expressed through the complex splicing of a single mRNA precursor leading to three mRNA classes: unspliced, singly-spliced and multiply-spliced. Each class may include several mRNA species specifically encoding one or two HIV-1 proteins. Northern blotting and RT-PCR are the techniques currently used to analyse HIV-1 mRNA expression. Northern blotting allows quantitative detection of these three classes of viral RNA but does not discriminate between individual RNA species. RT-PCR allows discrimination between different species but does not provide a quantitative analysis. Here, we describe an application of an RNAse mapping assay which gives both quantitative and discriminative HIV-1 RNA detection. A radiolabeled probe overlapping the major splicing sites of HIV-1 used for the generation of HIV-1 mRNA subspecies was synthesized. This probe protects differential sizes of these species, allowing discrimination between them. We investigated the RNA expression pattern in high titer HIV-1 producing cells. The HIV-1-specific probe allowed the detection of multiply-spliced vpr, rev and nef mRNAs, singly-spliced env mRNA and unspliced genomic RNA. With its discriminative and quantitative properties, this application is particularly convenient for the investigation of HIV-1 mRNA expression during the course of HIV-1 infections.

Generation of monoclonal antibodies to native human immunodeficiency virus type 1 envelope glycoprotein by immunization of mice with naked RNA.

The Semliki Forest virus (SFV) vector system is a new approach for in vivo expression of heterologous proteins and can also be used to generate specific immune responses in animal models. HIV-1 envelope glycoprotein produced using the SFV expression system is correctly folded, cleaved, transported to the cell surface and exhibits functional activity. We evaluated a recombinant Semliki Forest virus naked RNA-based immunization protocol for generation of monoclonal antibodies against the HIV-1 envelope glycoprotein. In vitro-transcribed RNA encoding for the SFV replicase complex and Env protein of HIV-1 (HXB2 strain) was injected intramuscularly to mice. This approach elicited an Env-specific antibody response in four mice out of five and a monoclonal antibody, 12H2, directed against gp41 was produced. Our results show that recombinant SFV RNA immunization can potentially be used as a quick and direct method to produce monoclonal antibodies, with the particular advantage that vectored RNA, rather than purified antigen, delivers a complex oligomer produced correctly.

Detection of human papillomavirus types 6, 11, 16 and 18 in mucosal and cutaneous lesions by the multiplex polymerase chain reaction.

A multiplex polymerase chain reaction (PCR) based on the simultaneous amplification of human papillomavirus (HPV) types 6/11, 16 and 18 in a single-step procedure was developed, using primers chosen in the E6-E7 region. The specificity and sensitivity of this technique have been proved by amplifying mixtures or various amounts of plasmid-containing HPV DNA; it allowed the detection of as few as 5-25 HPV DNA copies. Application of the multiplex PCR to 71 clinical samples showed that HPV DNA was detected in 80% (45/57 cases) of mucosal biopsies and 35% (5/14 cases) of cutaneous specimens. HPV 16 was predominant in high-grade CIN whereas HPV 6 and 11 were detected more frequently in genital condylomas and laryngeal papillomas. In cutaneous Bowen's disease HPV 16, 18 or 6/11 + 16 were detected and in squamous cell carcinomas HPV 6/11 or 16 were found. After sequence amplification with primers of one HPV type, the clinical samples displayed the same HPV types but the frequency of positive and coinfected lesions increased. Thus, multiplex PCR is a valuable technique for typing HPV DNA but coinfections may be underestimated.

Specific detection of RT activity in culture supernantants of retrovirus-producing cells, using synthetic DNA as competitor in polymerase enhanced reverse transcriptase assay.

The polymerase enhanced reverse transcriptase (PERT) assay is a highly sensitive assay for the detection of reverse transcriptase (RT) activity in culture supernatants of retrovirus-producing cells. However, some cellular DNA-dependent DNA polymerases exhibit RT-like activities in this assay. A synthetic DNA competitor which suppresses the RT-like activities of cellular DNA-dependent DNA polymerases was used in a modified PERT assay technique for specific detection of RT activity in culture supernatants of retrovirus-producing cells. We determined the optimum condition of the assay and evaluated its specificity. This improved PERT assay is easy to perform and is able to detect minute amounts of purified RT, as well as RT in crude cell lysates and concentrated culture supernatants.

Quantitation of HCV RNA using real-time PCR and fluorimetry.

Real-time PCR technology may provide an accurate and sensitive method to quantify hepatitis C virus (HCV) RNA. So far, studies have been carried out using the Taqman technology with the ABI Prism 7700 sequence detector. An alternative and simple real-time PCR assay is described with no probe requirement, based on the SYBR Green I dye and LightCycler fluorimeter. Amplicon synthesis was monitored continuously by SYBR Green I dye binding to double stranded DNA during PCR of the 5' HCV non-coding (NC) region. Specificity was verified by amplicon melting temperatures. An external standard curve was constructed with serial 10 fold dilutions of a modified synthetic HCV 5' NC RNA. A wide range linear relationship (up to 3.7x10(9) copies/ml) was observed between number of PCR cycle needed to detect a fluorescent signal and number of RNA copy. Intra- and inter-assay coefficients of variation were 0.7 to 2.1 and 3.7% respectively, indicating good reproducibility of the method. Thirty-three HCV positive sera of different genotypes were quantified by this method and gave similar but more sensitive results compared to the branched DNA (bDNA) technology.

Detection of a gliotoxic activity in the cerebrospinal fluid from multiple sclerosis patients.

We recently showed that peripheral blood cell supernatants from multiple sclerosis (MS) patients, containing reverse transcriptase activity and retroviral RNA from the newly human identified multiple sclerosis retrovirus (MSRV), also secrete a cytotoxin which induces death of primary mouse cortical glial cells. We have hypothesized that macrophages could release this cytotoxin in the cerebrospinal fluid. The cerebrospinal fluid cytotoxicity from 166 patients with various neurological diseases (including MS patients) was tested on glial cells in vitro. Our bioassay shows that a glial cytotoxic activity is significantly present in cerebrospinal fluid from patients with relapsing-remitting MS at relapse. Since this cytotoxic activity seems to correlate with active cases of MS, it may represent a critical pathogenic factor in the neuropathology of MS.

Simultaneous enzymo-immunologic assays of platelet associated IgG, IgM and C3. A useful tool in assessment of immune thrombocytopenias.

A solid phase enzymo-immunologic assay (EIA) has been developed to measure platelet associated (PA) IgG, IgM and C3. Washed platelets are mixed with a goat anti-IgG (IgM or C3) antiserum and then incubated in serum coated polystyrene plates. There is an inverse relationship between the level of PA IgG (IgM or C3) and the amount of goat antibodies binding to the IgG (IgM or C3) coating the plates. These goat antibodies are detected by addition of a phosphatase-labelled sheep anti-goat immunoglobulins antibody followed by a substrate giving a colour reaction. Using this technique, platelets from normal donors gave values of 2.04 +/- 1.10 fg IgG/platelet (mean +/- SD), 8.66 +/- 2.61 x 10(-16) g IgM/platelet and 5.67 +/- 2.63 x 10(-16) g C3/platelet. In 35 thrombocytopenic ITP patients we observed an increased level of PA IgG in 25, of PA IgM in 24 and of PA C3 in 23, and all of them had at least an increase of one of the 3 components. In 10 ITP patients in remission, 2 had an increased level of PA IgG while PA IgM and C3 values were normal in all. On the other hand, 2 non thrombocytopenic patients with systemic lupus erythematosus had an increased level of PA IgM. Compared to the standard antiglobulin consumption assay (ACA), the EIA was simpler to perform and more sensitive.