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F Simon

Publications and source records attributed to F Simon.

At least 37 records · Page 2Linked to original sources
PubMed1997

Synthetic peptide ELISAs for detection of and discrimination between group M and group O HIV type 1 infection.

We developed and evaluated two peptide-based immunoassays to confirm and discriminate between group M and group O HIV-1 infection. These assays are based on in vitro competition for antibody binding between M and O peptides. The first EIA is based on competition between group M and group O gp41 immunodominant domains and the second on competition between group O and group M V3 regions of gp120. Two panels of sera were used: the first consisted of 109 sera collected from 27 group O- and 92 group M-infected patients in whom the HIV isolates had been genotyped by sequencing or heteroduplex mobility assay. In this panel, the combination of the two assays correctly discriminated 106 samples (100% group O and 96.7% group M samples). The second panel, used for the field evaluation of the two assays, consisted of 157 samples from HIV-1-infected Cameroonian patients, 33 strains having been genotyped. The combination of the two techniques in a serogrouping algorithm discriminated 147 of these samples, 74 being HIV-1 group O and 73 group M. These results always correlated with genotyping results. The 10 sera that were not successfully classified by these assays were from early seroconverters. Altogether, the two assays clearly differentiated 263 of 276 (94.9%) samples in the two panels. On the basis of the genotyping results, the positive predictive value for group discrimination in the two panels was 100% for both GSEIA assays. Our peptide-blocking group-specific EIAs for differentiation and confirmation of HIV-1 group M and group O infection are complementary tools for epidemiological studies and surveillance of HIV-1 group O strain trafficking.

Amino Acid Sequence↗
PubMed1997

Feline heartworm (Dirofilaria immitis) infection: detection of specific IgG for the diagnosis of occult infections.

Sera from 54 cats, 53 asymptomatic and one symptomatic (chronic dyspnoea and coughing), living in a hyper-endemic area for canine heartworm (Dirofilaria immitis) infection were studied to evaluate the reliability of two ELISA-based antibody tests coupled with both somatic (ELISASA) and excretory/secretory (ELISAE/S) antigens. All cats were examined by echocardiography and radiography. In addition, an ELISA-based test to detect adult female heartworm circulating antigens and a modified Knott test for microfilariae in the blood were carried out on all cats. No cat was positive for microfilariae in the blood. Heartworms were visualized in 12 of 54 cats by echocardiography. Of these, three asymptomatic cats and the symptomatic one had radiographic signs of infection and were the only ones positive for heartworm circulating antigens. All sera except two were positive when analyzed in ELISA(SA). In ELISA(E/S), nine sera were positive but three were negative. No sera from the 42 echocardiography-negative cats was positive in ELISA(E/S), but 11 were positive in ELISA(SA). Western blot analyses with somatic antigens of sera from echocardiography-positive cats showed at least four bands of recognition between 19 and 30 kDa and one of about 40 kDa. With E/S antigen, a large band of about 22 kDa and one of about 25 kDa were recognized; these appear to be most specific.

Animals↗
PubMed1997

Serological and virological characterization of HIV-1 group O infection in Cameroon.

OBJECTIVES: To study the presence of HIV-1 group O infection among HIV-infected people in Cameroon and to further characterize the HIV-1 group O infections. DESIGN AND METHODS: During a 2-year survey (1994-1995), all samples tested positive in screening methods in the National Reference and Public Health Laboratory, Centre Pasteur, Yaoundé, Cameroon were identified as HIV-1 group M, HIV-1 group O or HIV-2 by using a serological algorithm. HIV-1 group M and HIV-1 group O were distinguished on the basis of competitive enzyme-linked immunosorbent assay (ELISA) reactivity against gp41 group M recombinant protein. HIV-1 group O infections were confirmed by using group O-specific V3 synthetic peptides. HIV-1 group O strains were isolated by lymphocyte cocultures, proviral DNA was amplified with specific primers, and sequencing was performed on the C2V3 and gag regions. RESULTS: Of the 8,331 screened samples, 3,193 were HIV-reactive, 2,376 (74%) of which were considered to belong to group M. The 817 (26%) that had reacted poorly or not at all against group M gp41 were further characterized: 10 were confirmed as HIV-2 and 82 as HIV-1 group O, the others being indeterminate (n = 285) or negative (n = 440). The frequency of group O relative to group M ranged from 1% in Far North province to 6.3% in the capital. There was no difference in sex, age or frequency of clinical manifestations between group M and group O infections. Group O infection was confirmed in a subset of cases by polymerase chain reaction (n = 14), with perfect concordance. Sequencing and phylogenetic analyses confirmed the high variability inside group O. CONCLUSIONS: Group O and group M epidemiological patterns are known to be similar so the reason for the lower prevalence of group O remains to be found. The wide distribution of group O infection in all Cameroonian provinces underlines the importance of further characterizing the epidemic spread and diffusion of this group.

Amino Acid Sequence↗
PubMed1997

Microwave CO2 plasma-initiated vapour phase graft polymerization of acrylic acid onto polytetrafluoroethylene for immobilization of human thrombomodulin.

The functionalization of polytetrafluoroethylene (PTFE) for human thrombomodulin (hTM) binding has been achieved by CO2 plasma activation and subsequent vapour phase graft polymerization of acrylic acid (AA). The PTFE surfaces after CO2 plasma treatment, AA grafting and hTM immobilization were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy, as well as by zeta potential and wetting measurements to quantitatively control each step of modification. The activity of immobilized hTM was estimated by the protein C activation test.

Acrylates↗
PubMed1997

Diversity of the immunodominant epitope of gp41 of HIV-1 subtype O and its validity for antibody detection.

The immunodominant regions of the gp41 from 13 HIV-1 subtype O strains from Cameroon, 11 from France and one from Germany were sequenced. The amino acid sequences were compared to those of the 3 published HIV-1 subtype O isolates, ANT70, MVP-5180 and VAU. All HIV-1 subtype O isolates had a very conserved amino acid sequence in this region and showed a subtype O specific structure. Within the cysteine loop there was a positive charge of two basic amino acids, arginine and lysine. Only two strains (CM.6778 and CM.8161) showed an acidic amino acid in this loop. None of the isolates showed the same amino acid sequence in this immunodominant region. A 25 residue peptide from the immunodominant domain of gp41 of the MVP-5180 strain was synthesized, cycled to form the cysteine-loop and coated to microtiter plates. Antibody binding was detected by indirect ELISA using an enzyme labeled anti-human IgG. Out of 111 anti-HIV-1 positive specimens, collected mainly from Cameroonian HIV infected patients, only 10 were not reactive in this assay. The 42 anti-HIV-1 subtype O positive specimens gave all a reaction above cut off. Despite the diversity found in the amino acid sequences within the 25 isolates a peptide-based indirect ELISA representing the immunodominant epitope of the strain MVP-5180 successfully detected all the anti-HIV-O sera so far tested, pointing to the importance of adding such a peptide for correct identification of HIV-1 subtype O infected patients, while some assays without HIV-O specific antigens partially fail to detect all anti-HIV-O specimens.

Amino Acid Sequence↗
PubMed1997

HIV-1 detection in cervicovaginal secretions during pregnancy.

OBJECTIVE: To assess the reproducibility of and factors associated with HIV detection in cervicovaginal secretions (CVS). DESIGN: Longitudinal study of 43 HIV-1-infected pregnant women in Paris. METHODS: HIV DNA was detected in peripheral blood mononuclear cells (PBMC) by Amplicor and gag nested polymerase chain reaction (PCR) assays. The HIV genotype was determined by heteroduplex mobility assay. Amplicor and gag nested PCR assays were performed on serial CVS samples for HIV DNA detection, and the HIV Monitor test was used for HIV RNA detection in plasma and CVS. RESULTS: A total of 144 CVS samples were collected from the women included in the study. HIV-1 DNA was detected in 36 (25%) of the 144 samples, from 16 (37.2%) of the 43 women. Results of HIV-1 DNA detection were concordant in the first two samples in 27 (84.4%) of the 32 women with at least two CVS samples. The last CVS sample collected in each woman was HIV-1 DNA-positive in 13 (30.2%) of the 43 women. Three factors were found to be independently associated with HIV-1 DNA detection in CVS: HIV-1 subtype B, absence of zidovudine therapy, and microbial cervicovaginal infection. HIV RNA was detected in CVS from 10 (23.3%) out of 43 women and correlated with DNA detection in the same sample and HIV RNA detection in plasma. CONCLUSIONS: DNA and RNA PCR can be used to detect HIV in cells and supernatants of CVS. These techniques may be useful in cohort studies to investigate HIV transmission and to evaluate the efficacy of antiretroviral drugs to reduce HIV excretion.

Adult↗
PubMed1997

Susceptibility of human immunodeficiency virus type 1 group O isolates to antiretroviral agents: in vitro phenotypic and genotypic analyses.

We investigated the phenotypic and genotypic susceptibility of 11 human immunodeficiency virus type 1 (HIV-1) group O strains to nucleoside and nonnucleoside reverse transcriptase (RT) inhibitors and protease inhibitors in vitro. Phenotypic susceptibility was determined by using a standardized in vitro assay of RT inhibition, taking into account the replication kinetics of each strain. HIV-1 group M and HIV-2 isolates were used as references. DNA from cocultured peripheral blood mononuclear cells was amplified by using pol-specific group O primers and cloned for sequencing. Group O isolates were highly sensitive to nucleoside inhibitors, but six isolates were naturally highly resistant to all of the nonnucleoside RT inhibitors tested. Phylogenetic analysis of the pol gene showed that these isolates formed a separate cluster within group O, and genotypic analysis revealed a tyrosine-to-cysteine substitution at residue 181. Differences in susceptibility to saquinavir and ritonavir (RTV) were not significant between group O and group M isolates, although the 50% inhibitory concentration of RTV for group O isolates was higher than that for the HIV-1 subtype B strains. The study of HIV-1 group O susceptibility to antiretroviral drugs revealed that the viruses tested had specific phenotypic characteristics contrasting with the group M phenotypic expression.

Amino Acid Sequence↗
PubMed1997

Temporal development and prognostic value of antibody response to the major neutralizing epitopes of gp120 during HIV-1 infection.

Our objective was to analyse the humoral response to the major neutralizing epitopes of gp120. The kinetics of the appearance of antibodies directed to the V3 region (V3 Abs) and antibodies directed to the CD4 binding site (CD4BS Abs) were compared in sequential sera from 20 seroconverters. V3 Abs were titrated using 2 different indirect EIAs with synthetic oligopeptides coated on the solid phase. The sequences of the oligopeptides used were those of the MN isolate or a mixture of the consensus sequences of the 5 major HIV-1 subtypes (A-E). CD4BS Abs titers were determined using an EIA in which serum antibodies compete with a labeled human monoclonal antibody, F105, whose corresponding epitope overlaps the conformation-dependent CD4BS, for binding to purified recombinant gp120 coated on a solid phase. The prognostic value of both antibodies was analyzed in a longitudinal study of 60 HIV-1 infected patients (17 nonprogressors and 43 progressors). Eighty-five percent and 70% of HIV sero-converters were positive for V3 Abs and CD4BS Abs, respectively, during the observation period. V3 Abs were detected first in the majority of the patients (mean delay of appearance, 1.22 +/- 0.96 months vs. 4.81 +/- 2.05 months for CD4BS Abs). Both categories of antibodies appeared simultaneously in 4 patients (20%). No prognostic value could be attributed to these antibodies. Our data confirm that V3 Abs and CD4BS Abs appear with some delay after primary infection, suggesting that they do not play a large or early role in the rapid clearance of viremia in primary HIV-1 infection. These antibodies were not associated with progression to symptomatic infection and are thus of no value for surveillance in HIV-1 infected patients.

Amino Acid Sequence↗
PubMed1997

[Bone lesions due to endemic African Kaposi sarcoma: a case report].

Based on clinical and epidemiological data Kaposi's sarcoma (KS) can be divided into four subtypes: classical KS, immunodepression-related KS (IKS), epidemic AIDS-associated KS (AKS), and endemic KS (EKS). EKS is the most common entity in intertropical Africa. The authors of this report describe a case of invasive KS of the extremities associated with metatarsal osteolysis in a 43-year-old man from Central Africa. The patient was seronegative for HIV. Osteolytic lesions associated with EKS are uncommon and present few specific symptoms. They are always associated with skin lesions and are sensitive to radiation therapy and/or systemic chemotherapy. With the growing HIV epidemic, the clinical features of EKS and AKS now overlap and distinction is no longer possible in Black Africa. However AKS rarely involves osteolytic lesions without unfavorable prognosis or unconventional therapeutic modalities. In patients who are seropositive for HIV, it is important to distinguish KS from bacillary angiomatosis. Since these two entities present similar clinical and radiological features, differentiation is usually achieved on the basis of histological findings but active therapeutic testing for bacillary angiomatosis may be necessary.

Adult↗
PubMed1997

[Praziquantel].

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Antiplatyhelmintic Agents↗
PubMed1996

V3 loop sequence analysis of seven HIV type 1 group O isolates phenotyped in peripheral blood mononuclear cells and MT-2 cells.

HIV-1-infected individuals from which syncytium-inducing (SI) viruses are isolated most often progress more rapidly to AIDS than individuals carrying only non-syncytium-inducing (NSI) viruses. The syncytium-inducing capacity of virus isolates is commonly determined in conjunction to replication in MT-2 cells. Comparison of HIV-1 env sequences and a site-directed mutagenesis study have indicated that the presence of a positively charged amino acid at position 11 or 25 in the V3 loop is minimally required for the SI capacity of HIV-1 subtype B viruses. Studies have also shown a similar correlation between positively charged signature amino acids in the V3 loop and syncytium formation in MT-2 cells for HIV-1 subtypes A, D, and E. In the present study virus phenotype was determined and compared to the V3 loop sequence of seven HIV-1 group O isolates. Three of the HIV-1 group O isolates showed the NSI/non-MT-2 tropic phenotype and two showed the SI/MT-2 tropic phenotype, whereas two isolates presented an uncommon NSI/MT-2 tropic phenotype. The V3 loop of the two SI/MT-2 tropic isolates had a high net positive charge and contained a positively charged amino acid at position 11 or 25. The V3 loop of the two NSI/MT-2 tropic isolates had a low net positive charge and contained a single positively charged amino acid at position 37.

Amino Acid Sequence↗