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Biomedical subjects

J Pillot

Publications and source records attributed to J Pillot.

At least 55 records · Page 3Linked to original sources
PubMed1994

Activation of the classical pathway of complement by non-immune complexes of immunoglobulins with human protein FV (FV fragment-binding protein).

Protein FV, a human sialoprotein recently described in the stools of patients suffering from liver diseases, binds the variable domain of the heavy chains of immunoglobulins. We show here that preincubation of this protein with monoclonal human IgG1 and IgM activates the complement cascade by forming non-immune complexes, as evidenced by haemolysis inhibition of antibody-coated sheep erythrocytes. As negative controls, no inhibition was observed after incubation either with immunoglobulins or with protein FV alone, and with the protein FV-depleted medium. Activation was due to the binding of immunoglobulins with protein FV, as shown by inhibition of protein FV-induced agglutination of the sensitized erythrocytes in the absence of complement. Activation of the classical pathway was demonstrated both by using a human IgG4 or F(ab')2 fragments unable to activate C1q, and by Western blot analysis of the cleavage of C4 in human serum. These results confirm that protein FV-binding mimics antigen-antibody reactions, and suggest its involvement in hepatitis-associated vasculitis and in local lesions of some inflammatory gut diseases.

Carrier Proteins↗
PubMed1994

ELISA in serodiagnosis of HCV infection.

A high level of anti-HCV is generally associated with viral replication and the number of recognized epitopes appears to be correlated with the viral charge. Nevertheless, the absence of detectable antibodies in about 60% of patients during the acute phase of the disease and in 10% of chronically infected (generally immunocompromised subjects) are heavy handicaps for HCV serology. Moreover, low levels of anti-HCV antibodies can persist after complete recovery, and HCV viremia does not appear to be associated with the presence of a special antibody specificity. The immunoblots presented as 'confirmatory test' always appear to be less sensitive than the screening tests and therefore are unable to discriminate between post-infection antibodies and false-positive reactions, as rare as they can be. In these cases, as in non-responder patients, PCR appears essential. The possible reasons of immune response limitations and the possible improvements of HCV serology are discussed.

Enzyme-Linked Immunosorbent Assay↗
PubMed1994

Immunoglobulin G antibodies in human vaginal secretions after parenteral vaccination.

The induction of antibodies in vaginal secretions by systemic (intramuscular) immunization in humans was investigated by using the tetanus toxoid vaccine. Five women, 30 to 40 years old, were injected with a currently used dose of toxoid (40 IU), and serum, saliva, and vaginal secretion samples were collected on day 0 and on day 6 or day 10. All of these subjects had been previously vaccinated at least 5 years before; four were in good health, whereas one suffered from AIDS in clinical category B3. In most cases, analysis of specific antibodies in the vaginal wash showed a dramatic rise after boosting. These antibodies were primarily of the immunoglobulin G (IgG) isotype. The specific activity (ratio of antibody titer to IgG concentration) was shown to increase after the booster injection, irrespective of variations in the IgG level during the menstrual cycle. Comparison between serum and genital antibodies showed no difference in terms of both specific activity and level of avidity. These results demonstrate that parenteral injections can induce a systemic-derived antibody release in the vaginal fluid. Hence, systemic vaccinations can be efficient at the genital level and thus could reinforce or even replace a local vaccine.

Adult↗
PubMed1994

Detection of antibodies to human immunodeficiency virus in vaginal secretions by immunoglobulin G antibody capture enzyme-linked immunosorbent assay: application to detection of seminal antibodies after sexual intercourse.

In order to evaluate a commercial immunoglobulin G (IgG) antibody capture enzyme-linked immunoassay (ELISA) (Wellcozyme HIV1 + 2 Gacelisa; Murex Diagnostics Limited, Dartford, United Kingdom) for the detection of antibodies to human immunodeficiency virus (HIV) in vaginal secretion samples (VS) from HIV-seropositive and -seronegative women, serum samples (S) and VS were obtained from 129 African women living in the Central African Republic, a country of high HIV prevalence. Sera were tested for HIV by routine second-generation ELISA with confirmatory Western blot (immunoblot) (WB). By the Gacelisa IgG immuno-capture assay, 45 VS were positive and 84 were negative, whereas by WB, 44 VS were confirmed positive and 85 were confirmed negative. Considering WB as a reference, the IgG immunocapture assay in VS was 97.7% sensitive (43 of 44 positive samples) and 97.6% specific (83 of 85 negative samples). Of 42 HIV-seropositive women, 41 (97.6%) had S and VS that both were HIV positive (S+ VS+), and of 87 HIV-seronegative women, 83 (95.4%) had S and VS that both were HIV negative (S- VS-). Five women had discordant results for S and VS. One (S+ VS-) possibly had a false-negative VS result. Two (S- VS+) had similar indeterminate patterns for S and VS in WB. Two (S- VS+) had a typical HIV-positive pattern on WB of VS, whereas S results in WB were indeterminate in one case and negative in the other case; for both women, detection of prostatic acid-phosphatase was positive in VS, strongly suggesting recent sexual intercourse with an HIV-positive man. Because all HIV-infected men have detectable IgG antibodies to HIV in the seminal fluid, an HIV-seronegative rape victim with HIV-positive VS (S- VS+) should receive short-term antiviral therapy to prevent possible HIV transmission.

Adolescent↗
PubMed1993

Nonimmune macromolecular complexes of Ig in human gut lumen. Probable enhancement of antibody functions.

Protein Fv, a human sialoprotein recently described in the stools of patients suffering from liver diseases, binds the variable domain of H chains without impairing Ag binding. Normal subjects are shown here to secrete protein Fv under a hidden form, saturated with luminal Ig. In feces, the nonimmune complexes are essentially of 1800 and 800 kDa M(r); they contain protein Fv molecules bound with F(ab')2 fragments produced by cleavage of Secretory IgA during colonic transit. The 800-kDa complexes correspond to 6 molecules of F(ab')2 fragments bound to a sole protein Fv dimer. This was established by comparison with an in vitro-made complex having a valency of 6. Investigation of the role of protein Fv shows that in vitro addition of this free molecule to antivirus or to anti-Salmonella typhi antibodies allows or augments agglutination of the corresponding pathogens. This property is of major interest for secretory antibodies because it favors their role in Ag conveyance in the mucus stream. It seems therefore that protein Fv is a novel key factor of the immune defense in gut.

Agglutination↗
PubMed1993

Delayed clearance of HBV-DNA detected by PCR in the absence of viral replication.

The polymerase chain reaction (PCR) was used to study the in vivo persistence and clearance of HBV-DNA in the serum of a monkey (Macaca mulatta) known to be naturally resistant to the HBV infection. Total infectious plasma, virus pellet, and viral DNA were inoculated into 3 different monkeys. Degradation of infectious particles and clearance of HBV-DNA were analyzed by detecting HBV-DNA sequences in serial dilutions of serum by dot blot hybridization and PCR. Semi-quantitation was carried out by comparison with minimal positive dilutions of known HBV-DNA. The presence of hepatitis B surface antigen (HB-sAg) and hepatitis B e antigen (HBeAg) in serum was also investigated. PCR assays were found positive in serial samples of the 3 monkeys, and passively transmitted viral DNA remained detectable for 3 months after inoculation. HBsAg and HBeAg were detectable for 3 weeks and 2 weeks, respectively, in a monkey inoculated with total infectious plasma. Semi-quantitation of HBV viremia showed that the amount of virus detected 1 day after injection was markedly decreased and persisted at a low level, showing a rapid and important sequestration of viral particles. Since replication can be excluded in these monkeys, the data show that HBV-DNA sequences can remain detectable at a low level in the serum for long periods. It is thus conceivable that PCR may also detect the HBV genome, eventually degraded in vivo, and a weakly positive result does not always mean ongoing viral replication.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Anti-gp160 IgG and IgA antibodies associated with a large increase in total IgG in cervicovaginal secretions from human immunodeficiency virus type 1-infected women.

To study the specific local immune response in vaginal fluids, 19 women infected with human immunodeficiency virus (HIV) type 1 and 23 seronegative controls were selected. Vaginal fluids were tested by ELISA for total IgG, IgA, and IgM levels and for specific IgG, IgA, and IgM antibodies to gp160. Total IgG, IgA, and IgM concentrations were 6.8-, 5.0-, and 2.5-fold higher, respectively, in HIV-1-infected women than in controls, with a positive correlation between IgG and IgA levels. IgG or IgA antibodies or both to gp160 were detected in 12 subjects (63%), whereas no IgM antibodies to gp160 were found. Anti-gp160 IgG strongly predominated. Serum samples were available for 11 women whose total IgG vaginal levels strongly correlated with total IgG in sera. These results suggest that transudation of serumborne antibodies is the main source of gp160-specific antibodies in the vaginal fluid of HIV-1-infected women.

Africa↗
PubMed1993

Unexpectedly high levels of some presumably protective secretory immunoglobulin A antibodies to dental plaque bacteria in salivas of both caries-resistant and caries-susceptible subjects.

The role of salivary antibodies in protection against cariogenic bacteria is actually a matter of debate. Correlation between caries experience and naturally occurring antibodies was extensively investigated. Comparison of salivary antibodies from 21 caries-resistant and 22 caries-susceptible subjects was carried out by using a new quantitative method. Secretory immunoglobulin A (S-IgA) antibodies to Streptococcus sobrinus and Streptococcus sanguis cells were detected in all salivas and at similar levels in both groups. When assayed with two major antigens from S. sobrinus, i.e., protein antigen I/II and cell wall carbohydrates, only specific activities of antibodies to the protein component were increased (P < 0.01), but this occurred unexpectedly in the caries-susceptible group. Western blot (immunoblot) analysis with the culture supernatant and cell wall proteins from S. sobrinus showed the same antibody specificity in both groups. No selective increase of the protease-resistant S-IgA2 subclass was found, and avidities of antibodies to both antigen I/II and cell wall carbohydrates were similar. Our results demonstrate that naturally induced S-IgA antibodies against S. sanguis, S. sobrinus, and the major antigens of the latter are not sufficient to inhibit caries development.

Adult↗
PubMed1993

Binding of nuclear factors to functional domains of the duck hepatitis B virus enhancer.

We have analyzed the structures, relative organization, and activities of binding sites for nuclear factors in the duck hepatitis B virus (duck HBV) enhancer. DNase I footprinting analysis and mobility shift assays demonstrate that this enhancer of 192 bp contains at least three binding sites for transcription factors: one for hepatocyte-adipocyte C/EBP, a second for the liver-specific transactivator hepatocyte nuclear factor 1 HNF-1, and a third for a factor, called F3, which binds to a DNA sequence bearing some resemblance to that for the ubiquitous factor EF-C. Analysis of transcriptional activity reveals that oligonucleotides corresponding to the individual binding sites, inserted upstream from a heterologous promoter, display very weak enhancer activity, whereas the enhancer encompassing these three sites displays very high activity. Analysis of duck HBV enhancer mutants indicates that the deletion of any of these sites leads to a modification of transcriptional enhancer activity. The hepatocyte nuclear factor 1 binding site is crucial, since an internal deletion of 14 bp abolishes the activity. The C/EBP site can act as repressor, and the F3 site is required for full activity. Comparative analysis reveals that the nuclear factors are similar to those bound to the human HBV enhancer but that the organization of their binding sites in the duck HBV enhancer is different.

Animals↗
PubMed1993

Hepatitis B virus (HBV) binding factor in human serum: candidate for a soluble form of hepatocyte HBV receptor.

A hepatitis B virus (HBV) binding factor (HBV-BF) was identified in normal human serum interacting with the pre-S1 and pre-S2 epitopes of the viral envelope located within the protein domains involved in recognition of hepatocyte receptor(s). This molecule was characterized as a 50-kDa glycoprotein showing an isoelectric point of 7.13 with a biological activity depending on its native molecular conformation and on intact sulfhydryl bonds. Monoclonal antibodies to HBV-BF recognized a membrane component of the normal human liver whereas they were unreactive with hepatocyte membranes of other species and with those of the HepG2 cell line. These results suggest that the HBV-BF represents a soluble fragment of the membrane component and can be related to the HBV receptor mediating attachment of HBV to human liver cells.

Antibodies, Monoclonal↗
PubMed1993

Purification and partial amino acid sequence of suppressive lymphokine from a CD8+ CD57+ human T hybridoma.

A T-suppressor (TS) lymphokine was purified from the supernatant of a T hybridoma established from CD3+ CD8+ CD57+ lymphocytes of a healthy bone marrow transplant patient. Using polyclonal rabbit antibodies, raised against a TS-enriched preparation, a specific protein of 47,000 MW was identified, which was used to prepare monoclonal antibodies. The screening of hybridomas was carried out by strip-ELISA, in which the 47,000 MW band, transferred on a membrane, served as antigen. One of these monoclonal antibodies (IgM kappa) was selected for purification of the native TS molecule, which exhibited the high suppressive activity on the phytohaemagglutinin (PHA) and alloantigen responses of peripheral blood lymphocytes. The establishment of amino acid sequences of five trypsinized cleavage peptides confirmed that this protein has not been previously identified. This lymphokine--also detected in the supernatant of normal CD8+ CD57+ lymphocytes--is likely involved in bone marrow transplantation tolerance.

Amino Acid Sequence↗
PubMed1993

Excess HBcAg in HBc antibody-negative chronic hepatitis B virus carriers.

HBcAg and antibody to HBcAg were assayed in chronic hepatitis B virus carriers who were not reactive for HBc antibodies on available commercial tests. HBc antibody-negative sera, collected before the onset of the acute phase in recovering patients, were used as controls. A high level of HBcAg was detected in HBc antibody-negative chronic hepatitis B virus carriers after dissociative treatment. HBcAg levels were correlated with serum hepatitis B virus DNA levels. Precipitation of immune complexes increased the amount of detected HBcAg. HBc antibodies were detected in some patients only after sucrose gradient fractionation of serum and dissociative treatment. All HBsAg-positive chronic carriers who lacked HBc antibody were immunocompromised. Our results show that in HBc antibody-negative chronic hepatitis B virus carriers with active replication, HBc antibodies may be complexed by the excess of antigen and become undetectable by the available commercial tests. Unresponsiveness to HBcAg cannot always be ascribed to infection by another hepatitis B virus-related virus or hepatitis B virus variant.

Carrier State↗
PubMed1992

Anti-pre-S responses and viral clearance in chronic hepatitis B virus infection.

Serial sera were collected prospectively during the clinical course of 13 HBsAg carriers with chronic liver disease and analyzed for ALT levels, pre-S1 and pre-S2 antigens and corresponding antibodies and other serological hepatitis B virus markers. In five patients, anti-pre-S1 and anti-pre-S2 antibodies became detectable in multiple serum samples, whereas in eight patients anti-pre-S was never detected or only appeared transiently during the follow-up. The first pattern was associated with normalization of ALT levels and undetectable pre-S antigens and viral DNA by the polymerase chain reaction assay at final follow-up. HBsAg clearance occurred in two of the five patients. The second pattern was one of persistence of HBsAg and pre-S antigens, associated with the presence of serum HBV DNA detectable by spot hybridization or polymerase chain reaction regardless of clinical outcome. These findings demonstrate the occurrence of anti-pre-S antibodies in chronic hepatitis B virus-induced liver disease and associate anti-pre-S appearance with the clearance of hepatitis B virus from serum.

Adult↗