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Biomedical subjects

A Tartar

Publications and source records attributed to A Tartar.

At least 91 records · Page 5Linked to original sources
PubMed1991

Antigenicity and immunogenicity of a multiple peptidic construction of the Schistosoma mansoni Sm-28 GST antigen in rat, mouse, and monkey. 1. Partial protection of Fischer rat after active immunization.

Among the schistosome proteins characterized as vaccine candidates, an Ag of 28 kDa (Sm-28-GST) has received considerable attention. It was shown to be antigenic in humans and protective in mice, rats, hamsters, and baboons. Synthetic peptides derived from its sequence have been used to characterize the immune response to the molecule and one of these, comprising aminoacids 115-131 has been shown to incorporate both T and B cell recognition sites in a variety of experimental models. An octameric ("octopus") construction of the 115-131 peptide has been synthesized and its antigenicity and immunogenicity have been examined. The octopus construct is immunogenic in rats, mice and baboons in the presence of CFA (for rodents) and Bacille-Calmette-Guérin vaccine (for primates) as adjuvants. This clearly indicates that the construction allowed the conservation of the immune sites of the cognate protein. Moreover, anti-octopus sera from immunized Fischer rats were able to mediate platelet-, macrophage-, and eosinophil-dependent cytotoxicity toward schistosomula. Rats immunized with the 115-131 octopus were partially protected against a challenge infection with Schistosoma mansoni cercariae and this was paralleled by an increased level of IgG and more importantly, of IgE Sm-28-GST-specific antibodies.

Amino Acid Sequence↗
PubMed1991

Molecular cloning and sequence analysis of bovine lactotransferrin.

The screening of a bovine submaxillary gland cDNA library yielded 25 clones coding for bovine lactotransferrin. The nucleotide sequence of the longest insert contained a protein-coding region of 2115 nucleotides and a 3' non-coding region of 194 nucleotides followed by a poly(A) tract of about 55 nucleotides. The predicted peptide sequence included a 16-amino-acid signal sequence upstream of the first amino acid of the native protein. The identity of the clone was confirmed by matching the amino acid sequence predicted from the cDNA with the N-terminal and tryptic peptide sequences derived from purified bovine milk lactotransferrin, and also by similarity with human and murine lactotransferrins. The cDNA described corresponds to a 705-amino-acid-long preprotein that lacks the start methionine. The sequence of the secreted protein is 689 amino acids long and contains five potential glycosylation sites. Bovine lactotransferrin is 69% and 64% identical to human and murine lactotransferrins, respectively.

Amino Acid Sequence↗
PubMed1991

Design of potent protein kinase inhibitors using the bisubstrate approach.

A new class of serine/threonine protein kinase inhibitors was designed by associating, in the same structure, mimics of both the ATP binding site and a protein substrate. Among the several potent antagonists which were obtained, the most active consists of isoquinoline-5-sulfonamide, as ATP mimic, and Ser-Arg6, as peptidic moiety, bound by a-NH(CH2)2NH(CH2)2CO-linker. This compound, with a Ki of 0.1 microM toward protein kinase C (PKC) and 0.004 microM toward cyclic AMP dependent protein kinase (PKA), is respectively 60- and 750-fold more active than the commercial inhibitor H-7.

Adenosine Triphosphate↗
PubMed1991

Deglycosylation of alpha 1-proteinase inhibitor is impaired in the faeces of patients with active inflammatory bowel disease (Crohn's disease).

1. alpha 1-Proteinase inhibitor (alpha 1-antitrypsin) was excreted in the faeces of patients with inflammatory bowel disease in different molecular forms: Mr-51,000 and Mr-45,000 forms were widely found in the stools of patients with active disease, whereas a Mr-38,000 species was frequently recovered from healthy subjects and patients with quiescent disease (Mizon, Becuwe, Balduyck et al. Clin. Chem. 1988; 34, 2268-70). 2. N-Terminal sequencing of the Mr-38,000 form of alpha 1-proteinase inhibitor, after SDS/PAGE and electrotransfer on polyvinyl difluoride membranes, showed that it differed from plasma alpha 1-proteinase inhibitor by the loss of 17 N-terminal amino acids. 3. Carbohydrate analysis of the isolated Mr-38,000 form revealed a total lack of neutral sugars. 4. In contrast, the Mr-51,000 form of alpha 1-proteinase inhibitor is glycosylated and thus could be differentiated by virtue of its reactivity with concanavalin A. The analysis of 25 faecal extracts from patients with Crohn's disease allowed us to confirm that the presence of the glycosylated form of alpha 1-proteinase inhibitor was closely related to the degree of inflammation. 5. From these data, it may be hypothesized that the hydrolytic activity of some glycosidases is greatly reduced in active Crohn's disease.

Adolescent↗
PubMed1991

Identification of T cell epitopes within a 23-kD antigen (P24) of Toxoplasma gondii.

Among the potentially vaccinating antigens, the products excreted/secreted by the parasite T. gondii have been demonstrated to be excellent candidates. The molecular cloning of one of these antigens (P24) present in excreted/secreted antigens (ESA) has recently been carried out in our laboratory. The recombinant antigen P24 corresponds to a native molecule of 23 kD. We were interested in determining the main epitopes of the P24 antigen eliciting a T lymphocyte response using synthetic peptides derived from the primary structure of P24. Five peptides: 64-79, 88-109, 170-193, 194-208 and 231-250 were synthesized according to their hydrophobicity, mobility and accessibility profiles. The presence of T lymphocyte epitopes in these peptides has been examined in the rat model. The determination of T cell epitopes was carried out using T lymphocytes from infected rats, and from ESA and P24 expression vaccine virus immunized rats. The results showed that the stimulation of T cells with these peptides varied according to the period after Toxoplasma infection. The main T cell stimulation was obtained with the 88-109, 170-193 and 194-208 peptides. When Fisher rats were immunized with ESA, a most significant stimulation was achieved with the 170-193 and 194-208 peptides. In addition, T lymphocytes primed with P24 expressed vaccine virus immunization were more stimulated with the 88-109 and the 194-208 peptides. This study showed that P24-derived peptide-specific T cells were elicited in the three experimental situations, although no antibody response against the 23-kD native antigen was evidenced in the Fisher rat model. However, the native antigen (presented by irradiated parasites) can induce a proliferative response of the 170-193 peptide-specific T lymphocytes, confirming that this peptide contains an important T cell epitope. The adoptive transfer into athymic rats of T helper cells recovered from 170-193 peptide-immunized Fisher rat conferred a significant protection to infected nude rats despite the fact that no antibody production was observed.

Animals↗
PubMed1990

Immunological crossreactivity between the human immunodeficiency virus type 1 virion infectivity factor and a 170-kD surface antigen of Schistosoma mansoni.

A monoclonal antibody (mAb) directed against a synthetic peptide derived from the sequence of the human immunodeficiency virus type 1 (HIV-1) regulatory protein virion infectivity factor (vif) labeled the surface of Schistosoma mansoni schistosomula by indirect immunofluorescence. Western blotting showed that two S. mansoni proteins of 170 and 65 kD were recognized by the mAb. Sera from 20% of S. mansoni-infected HIV-seronegative individuals tested recognized the PS4 peptide in an ELISA as did sera from S. mansoni-infected rats. Sera from individuals seropositive for HIV-1, but without schistosomiasis, that reacted with the vif peptide also recognized a 170-kD S. mansoni protein. This crossreactive S. mansoni antigen appears to be a target of immunity in vivo since passive transfer of the mAb VIF-CD3 to naive rats had a protective effect against a challenge infection with S. mansoni cercariae.

Amino Acid Sequence↗
PubMed1990

Secondary structure and immunogenicity of hybrid synthetic peptides derived from two Plasmodium falciparum pre-erythrocytic antigens.

Multicomponent synthetic vaccines containing both B and T cell epitopes belonging to two different pre-erythrocytic Ag of Plasmodium falciparum are presented. In a di-component hybrid, a circumsporozoite T cell epitope and a peptide representing a liver stage-specific Ag were connected to obtain a reciprocal reinforcement of helical potentials. In a tri-component hybrid, a sequence corresponding to the circumsporozoite repeat tetrapeptide (NPNA) was tandemly synthesized on the N-terminal end of the di-component hybrid. Both hybrid molecules were able to adopt a partial helical conformation in water as determined by circular dichroism studies. To analyze if the different components were immunologically functional in these vaccines, mich bearing genetic backgrounds known to respond or not to the individual components were immunized with the hybrids. The tri-hybrid peptide showed high immunogenic capacity as it elicited, in both H-2b and H-2k mice, high antibody responses against every separate individual sequence. Moreover, the antibodies induced by these conformationally restricted peptides were able to recognize the corresponding native proteins in the liver schizont and the sporozoite surface. H-2d mice, in which the immune response to the individual components was genetically restricted, did respond against the di-hybrid peptide. The tri-hybrid peptide, in which NPNA repeats were present, lacked this H-2d-priming capacity but it triggered antibody production in H-2d mice previously primed with the di-hybrid peptide. These results indicate that multivalent vaccines can provide positive (potentiating) effects by carefully combining structurally well defined epitopes; however, negative (suppressive) effects are also possible suggesting that selection of multivalent vaccine components will require testing of combined molecules to optimize specific immune responses and avoid undesirable effects which may result from negative molecular interactions.

Amino Acid Sequence↗
PubMed1990

Leiurotoxin I (scyllatoxin), a peptide ligand for Ca2(+)-activated K+ channels. Chemical synthesis, radiolabeling, and receptor characterization.

Leiurotoxin I (scyllatoxin) is a 31-amino acid polypeptide from the venom of the scorpion Leiurus quinquestriatus hebraeus which has been previously isolated and sequenced by others. This paper reports (i) the total synthesis of this scorpion neurotoxin as well as some aspects of its structure-function relationships; (ii) the synthesis of the analog [Tyr2]leiurotoxin I (scyllatoxin) that has been monoiodinated at high specific radioactivity (2000 Ci/mmol) and has served for the characterization of the properties of 125I-[Tyr2]leiurotoxin I binding sites (Kd = 80 pM, molecular mass of 27 and 57 kDa for two polypeptides in the leiurotoxin I binding protein); (iii) the similarity of physiological actions between leiurotoxin I and apamin. Both toxins contract Taenia coli previously relaxed with epinephrine, both toxins block the after-hyperpolarization due to Ca2(+)-activated K+ channel activity in muscle cells in culture; (iv) the probable identity of binding sites for apamin and leiurotoxin I. In spite of a different chemical structure apamin competitively inhibits 125I-[Tyr2] leiurotoxin I binding and vice versa. Moreover, the peculiar effects of K+ on 125I-[Tyr2]leiurotoxin I binding are identical to those previously observed for 125I-apamin binding.

Amino Acid Sequence↗
PubMed1990

Solution conformation of leiurotoxin I (scyllatoxin) by 1H nuclear magnetic resonance. Resonance assignment and secondary structure.

A proton NMR study at 500 MHz of leiurotoxin I in water is presented. Nearly complete sequence-specific assignments of the individual backbone and side-chain proton resonances were achieved using through-bond and through-space connectivities obtained from standard two-dimensional NMR techniques. The secondary structure of this toxin is inferred from a combination of short-range nuclear Overhauser enhancements, scalar couplings and proton/deuteron exchange rates. Three disulfide bridges locate the N-terminal part (that is alpha-helical from residue 6 to 16) on one side of a C-terminal two stranded antiparallel beta sheet (from Leu18 to Val29). The latter features a tight turn at Gly23-Asp24.

Apamin↗
PubMed1990

Polyvalent synthetic vaccines: relationship between T epitopes and immunogenicity.

Three different synthetic polyvalent vaccines have been constructed by conjugating four synthetic peptides without any carrier protein. The peptides were copy fragments of two bacterial antigens (Streptococcus pyogenes M protein and diphtheria toxin), two parasitic antigens (circumsporozoite protein of Plasmodium falciparum and Plasmodium knowlesi), and one viral antigen (hepatitis B surface antigen). Outbred guinea-pigs immunized with polyvalent vaccine containing streptococcal, diphtheric, P. knowlesi and hepatitis peptides raised high specific antibody response against the four specificities. Individual T cell analysis demonstrated that hepatitis peptide bears T dominant epitope. A similar immune response was obtained with a second polyvalent vaccine where the P. knowlesi peptide had been replaced by the P. falciparum peptide. In both experiments the malarial peptides behave like pure B epitopes. Prediction of immunodominant helper T-cell antigenic sites were performed with the five peptides using computer algorithm. Hepatitis and diphtheric peptides were selected whereas the streptococcal peptide was rejected although it can experimentally contain a T epitope. To confirm this result animals were immunized with a third polyvalent vaccine which does not contain the hepatitis peptide. No T cell proliferation or antipeptide antibodies were detected. These results demonstrate that the cooperative immune response requires a certain degree of antigenic complexity for the induction of antibody response.

Amino Acid Sequence↗
PubMed1990

Human kidney amiloride-binding protein: cDNA structure and functional expression.

Phenamil, an analog of amiloride, is a potent blocker of the epithelial Na+ channel. It has been used to purify the porcine kidney amiloride-binding protein. Synthetic oligonucleotides derived from partial sequences have been used to screen a human kidney cDNA library and to isolate the cDNA encoding the human amiloride-binding protein. The primary structure was deduced from the DNA sequence analysis. The protein is 713 residues long, with a 19-amino acid signal peptide. The mRNA was expressed in 293-S and NIH 3T3 cells, yielding a glycoprotein (i) that binds amiloride and amiloride analogs with affinities similar to the amiloride receptor associated with the apical Na+ channel in pig kidney membranes and (ii) that is immunoprecipitated with monoclonal antibodies raised against pig kidney amiloride-binding protein.

Amiloride↗
PubMed1990

A synthetic protein corresponding to the entire vpr gene product from the human immunodeficiency virus HIV-1 is recognized by antibodies from HIV-infected patients.

The 95 amino acid-protein encoded by the non-structural vpr gene of the human immunodeficiency virus type 1 (LAV-1BRU isolate) was chemically synthesized by solid phase methodology. The synthetic vpr protein was characterized by amino acid analysis, sequence analysis, RP-HPLC, and urea-SDS PAGE. Using a radioimmunoassay, antibodies to the synthetic protein were detected in sera of 25% of HIV 1-seropositive patients tested. Western blot analysis suggested that the antibodies preferentially recognize the dimeric form of vpr.

Amino Acid Sequence↗
PubMed1990

T-cell responsiveness towards various synthetic peptides of the P28 antigen in rat and mouse models during Schistosoma mansoni infection.

It has recently been demonstrated that the Schistosoma mansoni P28 antigen can induce a strong protective immunity after direct immunization in various experimental models. T lymphocytes from Fischer rats immunized with the recombinant P28 antigen were cultured in vitro in the presence of seven synthetic peptides derived from the amino acid sequence of the P28. The most significant and reproducible proliferation was obtained with the 24-43 and 115-131 synthetic peptides. In order to analyze whether these located determinants were also exposed to the host's immune system during the natural S. mansoni infection or after immunization with crude antigenic extracts of various development stages of the parasite, the T-cell responsiveness of infected or immunized Fischer rats and BALB/c mice was tested towards these synthetic peptides. The results showed that, in both permissive (mouse) and non-permissive (rat) hosts, 24-43 and 115-131 synthetic peptides are recognized during the course of infection and that there is a dynamic variation of this recognition. These peptides are also recognized by T cells educated against crude antigenic extracts of different developmental stages of the parasite which contained the native form of the P28 molecule. Taken together, the results indicated that these synthetic peptides derived from the recombinant P28 antigen can activate T lymphocytes educated against the native P28 molecule during the development and maturation of the parasite in their hosts. Therefore, they might be useful for the construction of synthetic vaccines against schistosomiasis.

Amino Acid Sequence↗
PubMed1989

Inhibition of protein kinase C by retro-inverso pseudosubstrate analogues.

A retro-inverso analogue of the pseudosubstrate sequence, Arg-Phe-Ala-Arg-Lys-Gly-Ala25-Leu-Arg-Gln-Lys-Asn-Val (1), found in the regulatory domain of all protein kinase C (PKC) subspecies was synthesized. It shows to be an inhibitor (IC50 = 31 microM) of the phosphorylation, by PKC, of [Ala9.10,Lys11.12] glycogen synthase (1-12). Its analogue in which D Ala25 is replaced by D Ser is not a PKC substrate, but a more potent inhibitor, competitive with the peptidic substrate (IC50 = 5 microM, Ki = 2 microM). Both retro-inverso peptides are highly specific for PKC versus adenosine cAMP-dependent protein kinase (PKA) and are totally stable towards proteolysis by trypsin or pronase.

Amino Acid Sequence↗
PubMed1989

Antipeptide antibody against the human low-density-lipoprotein receptor. Characterization and cross-reactivity with bovine lymphocytes.

A dodecapeptide corresponding to the external N-terminal sequence of the human low-density-lipoprotein (LDL) receptor was synthesized. Antibodies raised in rabbits against the peptide were purified and were shown to react specifically with the peptide and with human LDL receptor of fibroblasts, HeLa cells and lymphocytes using binding studies and immunoblotting. By indirect immunogold analysis, antibodies bound to the LDL receptor of human lymphocytes could be revealed as clusters. Anti-receptor peptide immunoglobulins specifically bound to the human HeLa cell's LDL receptor with a lower affinity than LDL (Kd x 3). The anti-receptor peptide immunoglobulins and 125I-labelled-LDL competed with each other for the LDL-receptor sites. Antibodies failed to react with lymphocytes of subjects with the homozygous form of familial hypercholesterolaemia. Cross-reactivity with the dodecapeptide of the bovine LDL receptor was limited, but this cross-reactivity was confirmed by the binding of anti-receptor peptide immunoglobulins to the LDL receptor from bovine lymphocytes.

Amino Acid Sequence↗
PubMed1989

Antipeptide antibodies discriminate between different SAA proteins in human plasma.

Antipeptide antibodies raised against two distinct sequences of human serum amyloid A (SAA) discriminate between different plasma isoforms of this acute phase reactant. As different SAA gene products have meanwhile been identified in human plasma, the discrimination between these different isoforms may help to clarify further the time of appearance of these different forms in plasma and their potential amyloidogenicity.

Antibodies↗
PubMed1989

Protective immunity in mice vaccinated with the Schistosoma mansoni P-28-1 antigen.

The P28-1 Ag induces a strong protective immunity toward Schistosoma mansoni infection in various experimental models. T lymphocytes of mice immunized with the recombinant P28-1 Ag were stimulated in vitro by schistosome Ag of different development stages and by three P28-1 Ag-derived synthetic peptides. The most significant stimulation was achieved with the 24-43 peptide. The use of two fragments of this peptide showed that the P28-1 T lymphocyte specificity concerned essentially the NH2 terminal sequence of the 24-43 peptide. Moreover, T lymphocytes specific for the 24-43 peptide were stimulated by both schistosome Ag and the recombinant P28-1 protein. The passive transfer of (Th + Ts) lymphocytes recovered from P28-1 Ag-immunized mice increased the IgG response to P28-1 and its peptides during infection but did not protect against a challenge infection, such as the passive transfer of anti-P28-1 sera. In contrast, P28-1 specific Th cell lines maintained in culture for 2 mo, passively transferred a strong protection (50%) to infected mice. Supernatants of P28-1-specific T cells obtained after stimulation with the corresponding Ag, were able to confer cytotoxic properties to platelets and macrophages. The presence of IFN-gamma for the cytotoxicity mediated by platelets and macrophage activating factor for the cytotoxicity mediated by macrophages in these supernatants is in a large part responsible for the parasite killing observed. Finally, a preliminary immunogenetic approach with H-2 congenic mice on BALB background showed that the P28-1 Ag T cell response was under the control of the MHC and that the H-2b haplotype determined a low response to P28-1 Ag and its peptides while H-2d and k haplotypes determined high responders.

Animals↗