Biomedical subjects

A Capron

Publications and source records attributed to A Capron.

At least 55 records · Page 3Linked to original sources

PubMed1999

Identification of a developmentally regulated Schistosoma mansoni serine protease homologous to mouse plasma kallikrein and human factor I.

The isolation of 2 genomic clones has allowed us to further characterize a Schistosoma mansoni serine protease designated SmSP1. The deduced amino acid sequence (248aa) considered as a 'light chain' encoding the active site, presents significant homologies with mouse plasma kallikrein and human factor I light chain. The secondary structure of SmSP1 'light chain' is correctly predicted and may be sufficient by itself to constitute an active enzyme. The biological function of SmSP1 is unknown, however, the homology with 2 serine proteases suggests that SmSP1 may play a role in the evasion of the host immune response. This is supported by the presence of the native protein corresponding to SmSP1 particularly in schistosomula released products (SRP) and in male dorsal spines. The expression of this enzyme is differentially regulated throughout the parasite life-cycle. However, infected animals with S. mansoni did not produce specific antibodies to recombinant SmSP1. The lack of such response could be advantageous to the parasite by protecting itself from host effector mechanisms.

Amino Acid Sequence↗

PubMed1999

Recombinant interleukin-16 selectively modulates surface receptor expression and cytokine release in macrophages and dendritic cells.

Interleukin-16 (IL-16), a natural ligand for the CD4 receptor, has been found to modulate T-lymphocyte function and to inhibit human immunodeficiency virus type 1 (HIV-1) replication. Antigen-presenting cells (APC), including macrophages and dendritic cells, are known to express functional surface CD4 molecules, to be susceptible to HIV-1 infection and to play a critical role in different immune processes. Therefore, we evaluated the ability of recombinant IL-16 (rIL-16) to regulate receptor expression and cytokine release in monocyte-derived macrophages (MDM) and monocyte-derived dendritic cells (MDDC). Recombinant IL-16 was found to up-regulate CD25 and CD80 but to down-regulate CD4 and CD86 surface expression in MDM cultures. However, no change could be observed on the level of CD4, CD80 and CD86 expression in IL-16-stimulated MDDC, although a significant up-regulation of CD25 and CD83 was consistently detected. Furthermore, the level of gene expression of the chemokine receptors CCR5 and CXCR4 was significantly reduced in rIL-16-treated MDM and costimulation with IL-2 did not modify the activity of the recombinant cytokine. The effects on chemokine receptor gene expression were less evident in MDDC and only a transient down-regulation of weak intensity could be detected following stimulation with rIL-16. Analysis of supernatants from rIL-16-stimulatedcultures revealed a different profile of released cytokines/chemokines among the two cell populations studied. These findings establish an important role for IL-16 in modulating the activity of APC and may have relevance regarding the protection of reservoir cells against HIV-1 infection.

Antigens, CD↗

PubMed1999

Definition and mapping of epitopes recognized by specific monoclonal antibodies to Schistosoma bovis 28 kDa glutathione S-transferase: relation with anti-egg viability immunity.

Monoclonal antibodies to the 28kDa glutathione S-transferase of Schistosoma bovis have been constructed in mice and used to characterize the epitope(s) potentially implied in the induction of anti-fecundity and anti-egg viability immune responses. Among the MoAbs produced three were particularly studied: Sb4-50 (IgG2a) and Sb4-56 (IgG1) which inhibited Sb28GST activity and Sb4-10 (IgG1) which did not. The use of overlapping peptides covering the entire amino acid sequence of Sb28GST, allowed us to define the linear epitopes recognized by these anti-Sb28GST MoAbs. Amino acid residues 202-211 were recognized by both MoAbs Sb4-50 and Sb4-56 and MoAb Sb4-10 recognized amino acid residues 58-67. Their capacity to inhibit GST activity suggested binding to the active site or to neighbouring regions, which include the C-terminal domain (a.a. 190-211) of the protein. When passively transferred into BALB/c mice MoAbs induced a significant reduction in egg hatching and an increase in immature eggs. Effects on worm burdens were, however, variable and no clear-cut association between the inhibition of enzyme activity and anti-fecundity or anti-viability activities was recorded. Our data indicate that beside the anti-fecundity and anti-viability immunity related to the impairment of GST activity, immune response to epitopes located in other regions of the molecule also contribute to the reduction of egg viability.

Amino Acid Sequence↗

PubMed1999

X-linked immunodeficiency affects the outcome of Schistosoma mansoni infection in the murine model.

The incidence of the X-linked immunodeficiency (Xid) on the outcome of Schistosoma mansoni infection has been evaluated through a comparative analysis of parasitological and immune parameters in two different mouse strains: control BALB/c and BALB. Xid mice which carry the Xid mutation and lack B1 (CD5+ B) cells. This study clearly demonstrates that infected B1 cell-deficient animals display a higher susceptibility to S. mansoni infection as revealed by an increase in the tissue egg loads and a significantly elevated mortality, as well as an increase in the granuloma densities. The analysis of the humoral and the cellular responses, conducted in the same experimental conditions, indicates differences in terms of cytokine production after specific antigenic stimulation of splenocytes. Larger amounts of IFN-gamma and IL-4 are observed in BALB. Xid mice while IL-10 production is reduced. In parallel, the study of the specific antibody isotype profiles shows higher amounts of specific IgE and IgG1 antibodies and lower amounts of IgM and IgA in BALB. Xid mice. Taken together, these observations support the idea that B cells are playing a role in the ability of mice to tolerate infection with Schistosoma mansoni.

Animals↗

PubMed1999

Protective immunity in the rat model of congenital toxoplasmosis and the potential of excreted-secreted antigens as vaccine components.

Toxoplasma infection is a major cause of severe foetal pathology both in humans and in domestic animals, particularly sheep. We have previously reported the development of an experimental model to study congenital toxoplasmosis in the rat. Here we demonstrate that, as in humans, total protection against congenital toxoplasmosis can be achieved regardless of the strain of Toxoplasma gondii used to infect rats, or when initial and challenge infections were carried out with different strains. Chronic infection is associated with a highly specific immunity that involves both B-and T-cell responses beginning at day 10 postinfection. The antibody isotype analysis revealed that whereas immunoglobulin (Ig)G2b is the major elicited isotype, no IgG1 antibodies are detected. T cell proliferation was assayed using crude Toxoplasma extracts or excretory-secretory antigens (ESA). The analysis of T cell supernatants showed the specific secretion of both interleukin-2 and interferon-gamma by activated T cells. Immunization of rats before pregnancy with either crude Toxoplasma extracts or with ESA elicited a B cell response that included antibodies of the IgG1 isotype and conferred on the newborns high levels of protection. Preliminary experiments of immunization using two HPLC-purified ESA, GRA2 and GRA5, conferred, a significant protection although to a lesser extent. This experimental model represents an attractive model for the identification of future vaccine candidates against congenital toxoplasmosis.

Animals↗

PubMed1999

Egg-hatching inhibition in mice immunized with recombinant Schistosoma bovis 28 kDa glutathione S-transferase.

The capacity of a recombinant glutathione S-transferase from Schistosoma bovis (rSb 28GST) to protect BALB/c mice against homologous and heterologous infections with, respectively, S. bovis or Schistosoma mansoni has been studied. Two injections of the rSb 28GST and an intravenous boost resulted in a marked specific IgG response on the day of experimental challenge with S. bovis or S. mansoni cercariae. Immunization of BALB/c mice led to a reduction in egg maturation and egg viability after infection with S. bovis or S. mansoni. Adult worm recoveries after an S. bovis challenge infection and tissue egg densities (intestine and liver) in S. mansoni challenge infection were also reduced in the immunized groups, but these differences were not statistically significant. No association between in vitro inhibition of GST enzymatic activity induced by immunized mouse sera and worm burden reduction was recorded. The analysis of the immune response, on the day of perfusion, showed the production of immunoglobulin (Ig)G1, IgG2a and IgG2b specific antibodies and the production of interleukin (IL)-4 and IL-5 by spleen cells after rSb 28GST stimulation. These data suggest that rSb 28GST immunization induces a moderate effect upon egg maturation and egg hatching, suggesting the involvement of similar mechanisms of action and common, but not exclusive, targets during S. bovis and S. mansoni infections. As a consequence, immunization with rSb 28GST may prove useful in affecting the pathology and transmission of African schistosomes.

Animals↗

PubMed1999

Cytokine mRNA expression in lymphoid organs associated with the expression of IgA response in the rat.

The T-helper dependency of the IgA antibody response has been investigated in rats injected intravenously with Schistosoma mansoni eggs. This method, allowing the trapping of parasite eggs in the lung tissue, led to a strong anti-egg IgA antibody response in the bronchoalveolar lavage but not in the serum. To characterize the cytokine pattern associated with the IgA response, kinetic analysis of the cytokine mRNA expression in the lungs, periaortic nodes (PN) and spleen was undertaken. Under such conditions, significant levels of mRNA encoding IL-5 and IL-10 were recorded in spleen during the early period following egg injection, as well as a more prolonged expression of TGF-beta and IL-6 mRNAs. However, neither IFN-gamma nor IL-4 mRNA could be detected in these samples. Finally, in lungs and in PN, RT-PCR analysis revealed delayed production of cytokine mRNA. Taken together our data suggest that the rat mucosal IgA antibody response is predominantly linked to a Th2 response.

Animals↗

PubMed1999

Cellular immune responses of a Senegalese community recently exposed to Schistosoma mansoni: correlations of infection level with age and inflammatory cytokine production by soluble egg antigen-specific cells.

A recently reported epidemic of Schistosoma mansoni infection in Senegal provided an opportunity to study the dynamics of the development of immunity to human schistosomiasis. We report here on the cell-mediated immune response in a population of 99 females and 95 males, with particular emphasis on the relationship between intensity of infection and age. We found that the intensity of infection correlated negatively with age in females but not in males. In men and women, both Th1- and Th2-type cytokines were detected upon in vitro stimulation of PBMCs with soluble egg antigen (SEA) or soluble adult worm antigens (SWAP). In the female group, SEA-induced PBMC proliferation was associated with the production of IFN-gamma, IL-2 and IL-5, all of which correlated negatively with intensity of infection. Most cytokine production correlated positively with age. Spontaneous production of TNF-alpha, IL-6 and IL-10 was higher in the infected population than in an uninfected control group. Our results suggest that immunity to infection could be more pronounced in the female population and associated with a Th0/1 + 2 pattern of cytokine secretion mediated by soluble egg antigen (SEA).

Adolescent↗

PubMed1999

Human chemokine receptors CCR5, CCR3 and CCR2B share common polarity motif in the first extracellular loop with other human G-protein coupled receptors implications for HIV-1 coreceptor function.

Chemokine receptors (CRs) are 7-helix membrane proteins from the family of G-protein coupled receptors (GPCRs). A few human CRs act as cofactors for macrophage-tropic (M-tropic) human immunodeficiency virus type-1 (HIV-1) entry into cells, while others do not. In this study, we describe an application of molecular modeling techniques to delineate common molecular determinants that might be related to coreceptor activity, and the use of the data to identify other GPCRs as putative cofactors for M-tropic HIV-1 entry. Subsequently, the results were confirmed by an experimental approach. The sequences of extracellular domains (ECDs) of CRs were employed in a compatibility search against a database of environmental profiles derived for proteins with known spatial structure. The best-scoring sequence-profile alignments obtained for each ECD were compared in pairs to check for common patterns in residue environments, and consensus sequence-profile fits for ECDs were also derived. Similar hydrophobicity motifs were found in the first extracellular loops of the CRs CCR5, CCR3, and CCR2B, and are all used by M-tropic HIV-1 for cell entry. In contrast, other CRs did not reveal common motifs. However, the same environmental pattern was also delineated in the first extracellular loop of some human GPCRs showing either high (group 1) or low (group 2) degree of similarity of their polarity patterns with those in HIV-1 coreceptors. To address the question of whether the delineated molecular determinant plays a critical role in the receptor-virus binding, three of the identified GPCRs, bradykinin receptor (BRB2) and G-protein receptor (GPR)-CY6 from group 1, and GPR8 from group 2, were cloned and transfected into HeLa-CD4 cells, which are nonpermissive to M-tropic HIV-1 infection. We demonstrate that, similar to CCR5, the two selected GPCRs from group 1 were capable of mediating M-tropic HIV-1 entry, whereas GPR8 from group 2 did not serve as HIV-1 coreceptor. The potential biological significance of the identified structural motif shared by the human CCR5, CCR3, CCR2B and other GPCRs is discussed.

Amino Acid Sequence↗

PubMed1999

Interleukin-16 (IL-16) inhibits human immunodeficiency virus replication in cells from infected subjects, and serum IL-16 levels drop with disease progression.

The role of recombinant interleukin-16 (rIL-16) in regulating human immunodeficiency virus type 1 (HIV-1) replication in endogenously infected cells has been investigated. Cultures of CD8 cell-depleted mitogen-activated lymphocytes from 22 of 26 HIV-1-infected subjects presented variable levels of secreted p24 antigen. The presence of rIL-16 throughout the 14-day culture period dramatically inhibited p24 release into the culture supernatants. This effect was found to be mediated through inhibition of viral transcription but to be independent of the induced levels of other cytokines or chemokines known to regulate viral replication. Analysis of serum samples from HIV-1-infected subjects over a period of 8 years showed maintained or even increased IL-16 levels during the whole asymptomatic phase and a significant drop on progression to disease. These results strongly support a potential therapeutic value of rIL-16 in HIV-1 infection and the use of serum IL-16 levels to monitor disease progression.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Control of schistosomiasis pathology by combination of Sm28GST DNA immunization and praziquantel treatment.

Today the control of schistosomiasis infection relies only on the use of praziquantel (PZQ) chemotherapy. However, PZQ treatment cannot prevent reinfection and progressive development of the pathology. We assessed in a mouse model the efficiency of a combined therapy, based on the combination of PZQ chemotherapy with Schistosoma mansoni 28-kDa glutathion S-transferase (Sm28GST) DNA vaccination, designed to limit the pathology. Following this combined therapy, the long-term survival of the mice was significantly enhanced in comparison with the survival of mice either vaccinated only or treated with PZQ only. In addition, the development of the pathology observed in the control groups was almost completely prevented in the vaccinated-PZQ-treated mice and was associated with a dramatic reduction of egg deposition in the tissues. We showed that PZQ treatment induced the unmasking of the native GST enzyme at the surface of the worms, thus permitting its neutralization by the antibodies raised by DNA immunization. This study provides insights into the synergistic mechanisms involved in an immunointervention strategy associated with chemotherapy for the control of a chronic infection and its associated pathology.

Animals↗

PubMed1999

Single-dose mucosal immunization with biodegradable microparticles containing a Schistosoma mansoni antigen.

The purpose of this work was to assess the immunogenicity of a single nasal or oral administration of recombinant 28-kDa glutathione S-transferase of Schistosoma mansoni (rSm28GST) entrapped by poly(lactide-co-glycolide) (PLG)- or polycaprolactone (PCL)-biodegradable microparticles. Whatever the polymer and the route of administration used, the equivalent of 100 microg of entrapped rSm28GST induced a long-lasting and stable antigen-specific serum antibody response, with a peak at 9 to 10 weeks following immunization. Isotype profiles were comparable, with immunoglobulin G1 being the predominant isotype produced. The abilities of specific antisera to neutralize the rSm28GST enzymatic activity have been used as criteria of immune response quality. Pooled 10-week sera from mice receiving PLG microparticles by the nasal or oral route neutralized the rSm28GST enzymatic activity, whereas sera of mice receiving either PCL microparticles, free rSm28GST, or empty microparticles inefficiently neutralized this enzymatic activity. Finally, this study shows that a single administration of these microparticles could provide distinct and timely release pulses of microencapsulated antigen, which might greatly facilitate future vaccine development.

Administration, Intranasal↗

PubMed1999

Profiles of Th1 and Th2 cytokines after primary and secondary infection by Schistosoma mansoni in the semipermissive rat host.

In contrast to most mouse strains, rats eliminate the primary schistosome burden around 4 weeks postinfection and subsequently develop protective immunity to reinfection. In rat schistosomiasis, we have shown predominant expression of a Th2-type cytokine response at the mRNA level after primary infection. In the present study, we showed a significant increase in interleukin-4 (IL-4) mRNA expression in inguinal lymph nodes early after a secondary infection. IL-5 mRNA expression showed a significant increase at days 2 and 4 postreinfection in the spleen and lymph nodes, respectively. We did not detect any gamma interferon (IFN-gamma) mRNA after a challenge infection. Analysis of cytokine secretion by stimulated spleen cells after a primary infection showed predominant expression of IL-4 with maximum production on day 21, accompanied by production of IL-5 from day 11 to day 67. A significant increase in IFN-gamma secretion was detected at day 21. Analysis of immunoglobulin G2b (IgG2b) and IgG2c (Th1-related isotypes) showed undetectable levels of IgG2b, but detectable levels of specific IgG2c antibodies were observed from day 42. The analysis of Th2-related isotypes showed high specific IgG1 and IgG2a antibody titers from day 29. After a secondary infection, only IL-4 and IL-5 secretion was sustained. This is supported by the increased production of Th2-related isotypes. These findings showed that S. mansoni infection can drive Th2 responses in rats in the absence of egg production which is required to induce a Th2 response in mice and are in favor of the role of Th2-type cytokines in protective immunity against reinfection.

Animals↗

PubMed1999

Schistosoma mansoni activates host microvascular endothelial cells to acquire an anti-inflammatory phenotype.

Since endothelial cells (ECs) play a key role in immune defense mechanisms and in immunopathology, we investigated whether the intravascular helminth parasite Schistosoma mansoni could interact with and activate resting ECs in vitro. Microscopic analysis revealed that the lung-stage schistosomula specifically attached to microvascular ECs. This adherence was associated to active cellular processes involving actin filament formation. Since variation of permeability of cultured capillary brain ECs is a good marker for endothelial activation, the transendothelial passage of a low-molecular-weight molecule (inulin) on monolayers of bovine brain capillary ECs (BBCEC) was measured in response to parasites. Schistosomula induced a dramatic decrease in transendothelial permeability, a characteristic marker for the generation of an anti-inflammatory phenotype to ECs. This paracellular barrier enhancing effect on endothelial monolayers was due to a soluble substance(s) (below 1 kDa in size) secreted from S. mansoni schistosomula and not by mechanisms associated to adherence between parasites and ECs. The reinforcement of the endothelial barrier function was accompanied by an elevation of intracellular concentration of cyclic AMP (cAMP). The use of specific kinase inhibitors confirms that schistosomula activate ECs through a cAMP/protein kinase A pathway that leads to an increased phosphorylation of the myosin light-chain kinase. These combined findings suggest that the secretory/excretory products from schistosomula possess anti-inflammatory factor(s) that signal host microvascular endothelium. The immunological consequences of such activation are discussed.

Animals↗

PubMed1999

Interleukin-16 inhibits human immunodeficiency virus type 1 entry and replication in macrophages and in dendritic cells.

Recombinant interleukin-16 (rIL-16) has been found to inhibit human immunodeficiency virus type 1 (HIV-1) replication in acutely or endogenously infected CD4(+) T cells. However, the effect of rIL-16 on HIV-1 replication in antigen-presenting cells (APCs) is still unknown. We show here a potent HIV-suppressive activity of rIL-16 in acutely infected monocyte-derived macrophages and dendritic cells determined by the levels of viral RNA transcripts or of viral reverse transcriptase in culture supernatants. The observed effect was dependent on the presence of rIL-16 early after infection and could not be induced by a 24-h treatment of cells with the cytokine prior to infection. Using macrophage-tropic and dually tropic primary isolates, we also showed that the addition of rIL-16 to cell cultures only during the infection period was effective in blocking virus entry and reducing proviral DNA levels in APCs. However, the anti-HIV activity of rIL-16 could not be linked to the induction of virus-suppressive concentrations of beta-chemokines or to the inhibition of HIV-enhancing cytokines. These findings establish a critical role for rIL-16 in protecting APCs against HIV-1 infection and lend further support to its potential use in the treatment of HIV disease.

Chemokine CCL4↗

PubMed1999

The oral route as a potential way of transmission of Schistosoma bovis in goats.

The infectivity of Schistosoma bovis cercariae administered orally was evaluated in Sahelian goats. Compared to the percutaneous route, a single massive oral dose resulted in a worm burden and in fecal egg excretion reduced by one-half. Surprisingly, tissue egg counts were increased by more than 4-fold. Fecundity of individual female schistosomes was, therefore, markedly increased. When infective doses were administered weekly for 20 wk, both worm and egg burdens were doubled without modification of the individual worm pair fecundity. Repeated oral infections seem to have induced an acquired tolerance toward parasite antigens. These results confirm the epidemiologic relevance of the oral route in a host species inclined to become infected through drinking water rather than percutaneous exposures.

Administration, Oral↗

PubMed1998

The house dust mite allergen, Dermatophagoides pteronyssinus, promotes type 2 responses by modulating the balance between IL-4 and IFN-gamma.

A common property of allergens is their potential to generate type 2 cytokine responses. To understand the mechanisms involved in this phenomenon, we have evaluated the polarizing potential of a major allergen, Dermatophagoides pteronyssinus 1 (Der p 1), in an heterologous immunization system using the glutathione S-transferase of the parasite Schistosoma mansoni (Sm28-GST) as immunogen. In previous studies, we showed that immunization with the Sm28-GST emulsified in CFA induced a nonpolarized immune response. In contrast, when alum was used as adjuvant, a type 2 immune response was induced against Sm28-GST. Using this experimental model, we examined whether the administration of Der p 1 together with Sm28-GST influenced the nonpolarized and/or the Th2 profiles induced by the CFA or the alum immunization, respectively. Our results showed that the introduction of Der p 1 in the CFA immunization protocol was associated with diminished anti-Sm28-GST IgG2a Ab titers, reduced IFN-gamma mRNA expression, and frequency of IFN-gamma-producing cells. In contrast, the introduction of Der p 1 in the alum protocol did not affect IL-4 or Ig isotype responses. The effect of Der p 1 was specific, since coimmunization with tetanus toxin fragment C did not affect the profile of the response against Sm28-GST. Furthermore, inactivation of Der p 1 reduced its ability to modify the immune response profile, suggesting that its protease activity played an important role in deviating the immune response. Our results suggest that the Der p 1 has the ability to modify the profile of an immune response by modulating the balance between the polarizing cytokines IL-4 and IFN-gamma.

Adjuvants, Immunologic↗

PubMed1998

Characterization of an intracellular receptor for activated protein kinase C (RACK) from the mollusc Biomphalaria glabrata, the intermediate host for Schistosoma mansoni.

A receptor for activated protein kinase C (RACK) was characterized from the mollusc Biomphalaria glabrata, the intermediate host for the human parasite Schistosoma mansoni. This protein was shown to possess structural and functional characteristics of other RACK proteins from various cells and organisms. Its ability to bind mammalian PKCs also confirmed the conservation of PKC and RACK interactive domains throughout evolution. Results of immunolocalization indicated the presence of Bg RACK in the cytoplasm of mollusc hemocytes and B. glabrata embryonic (Bge) cells with a more intense staining around the nucleus. These results are in agreement with the association of RACK proteins with cytoskeletal elements.

Amino Acid Sequence↗