Persistent antibody response to the HIV-1-negative regulatory factor in HIV-1-infected seronegative persons.
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Acquired Immunodeficiency Syndrome↗
Biomedical subjects
A Tartar
Publications and source records attributed to A Tartar.
Purification and partial characterization of a hepatocyte antiproliferative glycopeptide.
A low molecular weight compound, which inhibits the G1-S transition in rat hepatocytes, was obtained by tryptic hydrolysis of human alpha 2-macroglobulin followed by ultrafiltration at pH 10. It was purified by high-performance liquid chromatography on mu Bondapak C18 and mu Bondapak NH2 with a practically quantitative yield; from 5.1 g of alpha 2-macroglobulin, 2.8 micrograms of purified compound were recovered. Inactivation by specific enzymes and chemical analyses showed that the inhibitor is a sialylated glycopeptide whose peptide moiety contains a pyroglutamyl residue. Its molecular mass, estimated by gel permeation chromatography, would be in the interval 3,500-4,600. However, amino acid analyses indicated that it is not yet pure. All these data suggest that alpha 2-macroglobulin could be the carrier of the precursor form of the glycopeptide.
Amino Acids↗
Synthetic peptides approach to identification of epitopes on bovine leukemia virus envelope glycoprotein gp51.
Peptides corresponding to residues 21-28, 39-48, 57-67, 59-69, 78-92, 144-155, 144-157, 195-205, 255-268, and 260-268 of envelope glycoprotein gp51 of bovine leukemia virus (BLV) were chemically synthesized and coupled to keyhole limpet hemocyanin or tetanus toxoid. All peptides were immunogenic in rabbits and induced production of antipeptide antibodies. Enzyme-linked immunosorbent assays using Tween 80-purified gp51 or BLV particles showed that antibodies against peptides 78-92, 255-268, and to a lesser extent 39-48 and 144-157 were able to react with the parent glycoprotein, purified or as an integer part of BLV particles. Antisera against peptides 39-48, 78-92, and 144-157 neutralized VSV (BLV) pseudotypes in vitro, the highest neutralization titer being obtained with the 78-92 cyclized peptide. These observations confirm that the NH2 moiety of gp51 carries epitopes involved in virus infectivity.
Animals↗
Evidence for negative control in protein kinase C substrate specificity.
The peptide Leu-Asp-Asp-Ser-Lys-Arg-Val-Ala-Lys-Arg-Lys-Leu-Ile-Glu, which corresponds to sequence 124 to 137 of c-erb-A protein, was synthesized and tested as substrate for protein kinase C (PKC). Although a typical recognition sequence for PKC, consisting of a cluster of basic residues, is found on the C-terminus side of serine, its phosphorylation was totally prevented by the presence of the two acidic residues on the amino-terminus side. Three analogs in which aspartyl residues were successively replaced with alanine were studied and the influence of the acidic side chain in modulating phosphorylation by PKC was thus possible to determine. The results show that the presence of a single aspartyl residue located in positions i-1 or i-2 with respect to the phosphorylable residue can almost totally abolish the positive effect of a highly favorable cluster of basic residues. These observations highlight the role of negative substrate specificity determinants in settling the protein substrate profile of protein kinase C.
Amino Acid Sequence↗
The complete amino acid sequence of bovine milk angiogenin.
The amino acid sequence of angiogenin isolated from bovine milk was deduced by gas-phase sequencing of the protein and its fragments. The protein contains 125 residues and has a calculated molecular mass of 14,577 Da. The sequence is highly homologous (65% identity) to the sequence of human angiogenin, most of the differences being the result of conservative replacements. Like human angiogenin, the bovine protein is also homologous to bovine pancreatic RNase A (34% identity) and the three major active site residues known to be involved in the catalytic process, His-14, Lys-41 and His-115, are conserved. When tested against conventional substrates for RNase A activity, bovine angiogenin displays the same selective ribonucleolytic activity as human angiogenin. The sequence of bovine angiogenin contains the cell recognition tripeptide Arg-Gly-Asp which is not present in the human protein.
Amino Acid Sequence↗
Analysis of T and B cell epitopes of the Schistosoma mansoni P28 antigen in the rat model by using synthetic peptides.
The Schistosoma mansoni P28 molecule is an Ag inducing protective immunity in various experimental models. Three synthetic peptides, derived from the primary sequence of the recombinant P28 and comprising amino acids 24-43, 115-131, and 140-153, respectively, were synthesized according to their hydrophilicity, mobility, and accessibility profiles. The presence of B and T lymphocyte epitopes in these peptides has been examined in the rat model. The results showed that the 24-43 and the 115-131 peptides contained major epitopes for IgG but not for IgE. Moreover, the 24-43 peptide-specific IgG produced after injecting either the recombinant P28 Ag or the 24-43 peptide coupled to tetanus toxoid was essentially of the IgG2a subclass and to a lesser extent of the IgG1 subclass, whereas no IgG2c was detected. These 24-43 peptide-specific antibodies were cytotoxic in vitro for schistosomula in the presence of eosinophils as effector cells. The 24-43 and the 140-153 peptides contained major targets of T lymphocytes specific for the recombinant P28 Ag. T cell lines specific for the 24-43 peptide have been prepared. These cells proliferated in vitro when stimulated with various S. mansoni crude antigenic preparations or with the recombinant P28 Ag. Moreover, their passive transfer to rats immunized with the P28 Ag led to a significant increase in specific IgE without modifying the IgG response.
Animals↗
Antibodies of predetermined specificity to apolipoprotein C-II elicited with a synthetic peptide. Characterization and use for immunoassays.
Antibodies of predetermined specificity raised against a synthetic peptide corresponding to the C-terminal region of apolipoprotein C-II (Apo C-II) 63-79 were shown to be specific for the apolipoprotein by Western blot. The recognition by these antibodies of Apo C-II containing lipoprotein particles (both isolated and in plasma) was studied in a fluid-phase radioimmunoassay and the affinity constant for plasma was determined. The role of lipids in the expression of epitopes was studied by comparing the antigenicity of intact and delipidated Apo C-II containing fractions. The antibodies proved to be as suitable as conventional anti-protein antibodies in an immunoenzymometric assay and, moreover, were able to develop 'rockets' in an electroimmunoassay.
Antibodies↗
The neurotrophic factor neuroleukin is 90% homologous with phosphohexose isomerase.
Neuroleukin (NLK) is a protein of relative molecular mass (Mr) 56,000 (56K) secreted by denervated rat muscle and found in large amounts in muscle, brain, heart and kidneys. The protein is a neurotrophic factor for spinal and sensory neurons and a lymphokine product of lectin-stimulated T-cells. It also induces immunoglobulin secretion by human mononuclear cells. Molecular clones of NLK have been expressed in monkey COS cells and the product was shown to have the same biological and biochemical properties as the extracted protein. NLK is abundant in muscle, brain and kidney, but is active at concentrations of 10(-9) to 10(-11) M, similar to those for other polypeptide factors. We have cloned the gene for pig muscle phosphohexose isomerase (PHI) (EC 5.3.1.9) which catalyses the conversion of glucose-6-phosphate to fructose-6-phosphate, an obligatory step in glycolysis, and determined its amino-acid sequence. Surprisingly, it is 90% homologous to the sequence of mouse neuroleukin.
Amino Acid Sequence↗
Influence of helical organization on immunogenicity and antigenicity of synthetic peptides.
Using cooperative effects of different peptide structures synthesized in tandem, we have induced an alpha-helical structure in water solution on a peptide which, alone, is unorganized. This structure is particularly relevant in this case as the selected model protein (type 24 M protein of Streptococcus pyogenes) is an extended coiled-coil system. We were thus able to assess the importance of organization or unorganization of a unique amino acid sequence with regards to its immunogenicity and antigenicity. Although in a classical manner, antibodies cross-reacting with the protein can be obtained with the short, unorganized peptide, we demonstrate that conformation-specific antibodies are raised when longer, organized peptides are used as immunogens.
Animals↗
Photosubstitution of cymantrenylalanine as a tool in peptide chemistry. Synthesis and biological activity of new GnRH analogs.
Beyond its aromatic character and important hydrophobicity, cymantrenylalanine, a metallocenic amino-acid, can be easily photosubstituted with phosphine and phosphite ligands to readily yield new analogs with different hydrophobicity and steric hindrance. The incorporation of phosphine and phosphite ligands is described. As an illustration of the offered possibilities, the synthesis and the biological activity of two new GnRH analogs modified in position 6 are reported.
Alanine↗
Fluorescence-activated cell-sorting analysis of fibronectin peptides binding to Trypanosoma cruzi trypomastigotes.
The binding of synthetic peptides modeled from the sequence of the cell attachment site of fibronectin to T. cruzi trypomastigote surface receptors was investigated by fluorescence-activated cell-sorting analysis using fluorescein-labeled peptides. Peptides with the sequence Arg-Gly-Asp-Ser bound to the parasite surface. A low percentage of fresh parasites recently liberated from infected fibroblasts had the capacity to bind the peptide. In contrast, these parasites showed a time-dependent several-fold increase in their ability to bind the Arg-Gly-Asp-Ser-containing peptides during extracellular incubation. From these observations, it appears that the expression of surface receptors on a particular, mature stage of the parasite parallels its ability to adhere to and infect host cells.
Amino Acid Sequence↗
Enzyme-linked immunosorbent assay for human proapolipoprotein A-I using specific antibodies against synthetic peptide.
Apolipoprotein A-I (apoA-I), the major protein component of human high density lipoprotein, appears intracellularly as an intermediate precursor (proapoA-I) with a hexapeptide extension (Arg-His-Phe-Trp-Gln-Gln) at its amino terminus. To investigate the regulation of processes that regulate plasma apoA-I levels, a sensitive and simple assay for proapoA-I is required. We describe a specific enzyme-linked immunosorbent assay (ELISA) for quantification of proapoA-I using monospecific rabbit antibodies raised against the peptide: Arg-His-Phe-Trp-Gln-Gln-Asp-Glu-Pro. The monospecificity of antibodies to propeptide has been checked and no cross-reaction with mature apoA-I has been found although three first mature apoA-I amino acids (Asp-Glu-Pro) were included in the immunizing peptide. The assay is a non-competitive sandwich ELISA in which polystyrene microtiter plates were used with antibodies to propeptide adsorbed on the wells. After incubation with plasma samples, the bound proapoA-I was revealed by labeled rabbit polyclonal antibodies directed against mature apoA-I. The working range was 10 to 100 ng/ml, recovery of proapoA-I added to plasma was 94.6 to 106.5%, and the intra- and interassay coefficients of variation were 3.8% and 7.9%, respectively. A delipidation step using diisopropylether-n-butanol was necessary to expose antigen sites of proapoA-I in native lipoproteins. Mean level of proapoA-I in normal subjects was 87 +/- 15 micrograms/ml. It represented 7.1% of total apoA-I while in Tangier serum it represented 29%.
Apolipoprotein A-I↗
Enzyme-linked immunosorbent assay for serum amyloid A apolipoprotein with use of specific antibodies against synthetic peptides.
We describe a noncompetitive enzyme-linked immunosorbent assay for amyloid A apolipoprotein in human serum (apo SAA) in which specific antibodies against synthetic peptides are used. Microtiter plates were used as solid phase and coated with affinity-purified antibodies raised against SAA1-(95-104) peptide. After incubation with delipidated plasmas, the bound apo SAA was revealed by labeled antibodies raised against SAA1-(58-69) peptide. The assay offers several advantages over existing techniques: sensitivity, specificity, simplicity, and non-use of radioisotopes. Results correlate well with those by a nephelometric method in which polyclonal antibodies are used.
Amino Acid Sequence↗
Chemical approach to synthetic immunogens in clinical chemistry.
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Antibody Formation↗
Synthesis of conjugates between luteinizing hormone releasing hormone (LH-RH) and N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) models of totally synthetic vaccines.
Two glycopeptides associating the aminoacid sequence of LH-RH with MDP were prepared, using a Lys residue as a linker. These conjugates, N alpha MDP N epsilon (LH-RH)-Lys and N alpha MDP N epsilon (LH-RH)-Lys-NH2 obtained by condensation of fragments were synthesized by liquid as well as solid phase methods. Both compounds were able to induce anti LH-RH antibodies and immunological castration. They retained the immuno-adjuvant activity of MDP. Such antigen-adjuvant constructs, devoid of carrier and obtained by chemically defined and reproducible synthetic methods could offer suitable tools for structure-activity relationship studies aiming at defining synthetic vaccines.
Acetylmuramyl-Alanyl-Isoglutamine↗
Trypanosoma cruzi infection inhibited by peptides modeled from a fibronectin cell attachment domain.
The mechanism by which Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, becomes attached to mammalian cells is not well understood. Fibronectin is thought to participate in the attachment, and in this study the region of fibronectin that interacts with the surface receptors of T. cruzi trypomastigotes was investigated by testing the binding of the amino acid sequence Arg-Gly-Asp-Ser, corresponding to the cell attachment site of fibronectin to T. cruzi trypomastigotes. Peptides with the sequence Arg-Gly-Asp-Ser, but not Arg-Phe-Asp-Ser, Arg-Phe-Asp-Ser-Ala-Ala-Arg-Phe-Asp, Ser-Lys-Pro, Glu-Ser-Gly, or Ala-Lys-Thr-Lys-Pro, bound to the parasite surface and inhibited cell invasion by the pathogen. Monoclonal antibodies to the cell attachment domain of fibronectin also inhibited cell infection by the parasite. The immunization of BALB/c mice with tetanus toxoid-conjugated peptide induced a significant protection against T. cruzi. The data support the notion that the sequence Arg-Gly-Asp-Ser of cell surface fibronectin acts as a recognition site for attachment of the parasites.
Amino Acid Sequence↗
Replicative and cytopathic potential of HTLV-III/LAV with sor gene deletions.
The genome of the human T-lymphotropic virus type III (HTLV-III/LAV) has the potential to encode at least three polypeptides in addition to those encoded by the gag, pol, and env genes. In this study, the product of the sor (short open reading frame) region, which overlaps the 3' end of the pol gene, was found to be a protein with a molecular weight of 23,000. An assay was developed for testing the ability of cloned HTLV-III proviruses to produce viruses cytopathic for T4+ lymphocytes. In the cell line used, C8166, neither the HTLV-III sor gene product nor the complete 3'-orf gene product were necessary for the replication or cytopathic effects of the HTLV-III.
Cell Line↗
Binding studies of substance P anterior pituitary binding sites: changes in substance P binding sites during the rat estrous cycle.
Previous studies have shown that substance P (SP), an undecapeptide widely distributed in the gastrointestinal tract and in the peripheral and central nervous system, is a putative regulatory peptide involved in the control of reproductive function. Specifically, SP inhibited, at the anterior pituitary (AP) level, the stimulatory action of a physiological concentration (10(-8) M) of Gonadotropin Releasing Hormone (GnRH) on the release of the luteinizing hormone (LH). In the present work, we have demonstrated the presence of specific SP binding sites in the AP and related changes in the number of these sites to GnRH receptor number, hypothalamic SP and GnRH content and LH secretion during the rat estrous cycle. High affinity saturable SP binding sites (Kd, 1.5 approximately equal to 10 nM) were demonstrated in AP membranes using [3H]-SP or a novel analog, [125I]-(D-Tyr0, NorLeu11)SP. The binding affinity of SP fragments decreased with progressive removal of amino acid residues from N or C termini of the molecule. Other neuropeptides had low affinity for the SP binding sites. During the rat estrous cycle, SP and GnRH binding capacity of the anterior pituitary were inversely related. At the time of the proestrous LH surge, the AP binding capacity was low for GnRH but high for SP. The highest content of SP in the hypothalamus were recorded during the afternoon of proestrus when hypothalamic GnRH levels were lowest and the preovulatory surge occurred. These studies have established the presence of high affinity specific binding sites for SP in the AP which alter during the estrous cycle in a manner appropriate for mediating the direct inhibitory effects of SP on LH release in vitro.
Animals↗