Biomedical subjects

M Astori

Publications and source records attributed to M Astori.

11 recordsLinked to original sources

PubMed2002

In vivo kinetics of the immunoglobulin E response to allergen: bystander effect of coimmunization and relationship with anaphylaxis.

BACKGROUND: Murine models of hypersensitivity to allergens are useful tools for the evaluation of preclinical strategies to down-regulate the IgE response. OBJECTIVE: To monitor the long-term kinetics of T and B cell responses to allergen as a function of allergen dosage and to investigate the effect of parallel immunization with a second antigen; to correlate B cell response with anaphylaxis. METHODS: CBA/J mice were sensitized every other week by subcutaneous injections of phospholipase A2 (PLA2) and/or ovalbumin (OVA) adsorbed to alum. Specific antibody isotype responses, T cell proliferation, T cell cytokine production and anaphylaxis were assessed throughout the sensitization phase. RESULTS: Low-dose immunization with PLA2 (0.1 microg) favoured a long-term, specific T helper (Th)2 response with high IgE and IL-4 production in contrast to high-dose PLA2 (10 microg) immunization, which biased the immune response towards a Th1 response with high IgG2a and low IL-4 production. Parallel immunization with an unrelated antigen (ovalbumin) had a significant bystander effect on the immunization with PLA2, which was also dose-dependent. Finally, although anaphylaxis as measured by rectal temperature drop was allergen-specific, it could be induced in the high- and low-dose immunization groups, and was not solely dependent on IgE levels. CONCLUSION: Though low-dose allergen immunization appears to induce an efficient IgE response, the intensity and quality of this response may be modulated by bystander effects of parallel immunization and does not correlate strictly with anaphylaxis. This observation has relevance to the design of clinical immunotherapy protocols using murine model-based data.

Allergens↗

PubMed2001

Api m 6: a new bee venom allergen.

BACKGROUND: Characterization of the primary structure of allergens is a prerequisite for the design of new diagnostic and therapeutic tools for allergic diseases. OBJECTIVE: The purpose of this study was the identification and characterization of a low-molecular-weight, IgE-binding, bee venom (BV) allergen. METHODS: BV proteins were separated by using size exclusion chromatography and HPLC. IgE antibody binding to purified proteins was analyzed by means of immunoblotting, and T-cell response was analyzed by means of proliferation assay. Amino acid sequence was determined with 2 approaches, namely Edman degradation and carboxy terminal analysis with mass spectrometry. RESULTS: Api m 6, which migrated as an 8-kd band in SDS-PAGE, was frequently (42%) recognized by IgE from BV-hypersensitive patients. In addition, PBMCs from BV-hypersensitive patients, as well as from a normal control subject, proliferated in response to this allergen. Api m 6 exists as 4 isoforms of 7190, 7400, 7598, and 7808 d, respectively. Amino acid sequences obtained from HPLC-purified preparations revealed that the isoforms were constituted of a common central core of 67 residues, only differing in the amino- and carboxy-terminal ends. Api m 6 showed no significant sequence homology with known proteins. CONCLUSIONS: We have identified and sequenced a new BV allergen that elicits a strong IgE and T-cell response in a large number of BV-hypersensitive patients. Api m 6 should be considered in the diagnostic and therapeutic approach of BV immunotherapy on the basis of peptides or recombinant proteins.

Allergens↗

PubMed2000

Inducing tolerance by intranasal administration of long peptides in naive and primed CBA/J mice.

To assess the capacity of a peptide-based immunotherapy to induce systemic tolerance via the nasal route, we designed three long overlapping peptides of 44-60 aa covering the entire sequence of phospholipase A2 (PLA2), a major bee venom allergen. Both prophylactic and therapeutic intranasal administrations of long peptides to PLA2-hypersensitive CBA/J mice induced specific T cell tolerance to the native allergen. In prophylactic conditions, this tolerance was marked by a suppression of subsequent specific IgE response, whereas the therapeutic approach in presensitized mice induced a more than 60% decrease in PLA2-specific IgE. This decline was associated with a shift in the cytokine response toward a Th1 profile, as demonstrated by decreased PLA2-specific IgG1 and enhanced IgG2a levels, and by a decline in the specific IL-4/IFN-gamma ratios. T cell transfer from long peptide-tolerized mice to naive animals abrogated the expected anti-PLA2 IgE and IgG1 Ab response, as well as specific T cell proliferation, but enhanced specific IgG2a response upon sensitization with PLA2. These events were strongly suggestive of a clonal anergy affecting more profoundly Th2 than the Th1 subsets. In conclusion, these results demonstrate that allergen-derived long peptides delivered via the nasal mucosa may offer an alternative to immunotherapy with native allergens without the inherent risk of systemic anaphylactic reactions. Moreover, long peptides, in contrast to immunotherapy strategies based on short peptides, have the advantage of covering all potential T cell epitopes, and may represent novel and safe tools for the therapy of allergic diseases.

Administration, Intranasal↗

PubMed2000

Allergen-derived long peptide immunotherapy down-regulates specific IgE response and protects from anaphylaxis.

To evaluate a long peptide-based allergy vaccine in a murine model, CBA/J mice were sensitized with low dose alum-adsorbed phospholipase A2 (PLA2), a major bee venom allergen. Presensitized mice were treated by daily i.p. injections of a mixture of three long overlapping peptides (44- to 60-mer) spanning the entire PLA2 molecule (100 microg/peptide) for 6 consecutive days. This therapeutic approach induced a sharp drop in PLA2-specific IgE, an increase in specific IgG2a, and a marked T cell hyporesponsiveness. T cell cytokine secretion was characterized by a shift from a Th2 to a Th1 profile. Prophylactic treatment of naive mice with long peptides prior to sensitization with PLA2 induced a comparable modulation of B and T cell responses. Upon i.p. challenge with native PLA2, presensitized mice treated with the long peptide mixture were fully protected from anaphylaxis. This indicated that allergen-derived long overlapping peptides were safe and able to modulate an established Th2 response or to prevent its development. Furthermore, long peptide-based immunotherapy provided clinical protection against anaphylaxis, thus appearing as a promising approach of the therapy of allergic diseases.

Allergens↗

PubMed1999

Development of T-B cell collaboration in neonatal mice.

The neonatal immune response is impaired during the first weeks after birth. To obtain a better understanding of this immaturity, we investigated the development of T cell interactions with B cells in mice. For this purpose, we analyzed the immune response to three T-dependent antigens in vivo: (i) the polyclonal antibody response induced by vaccinia virus; (ii) the production of polyclonal and specific antibodies following immunization with hapten-carrier conjugates; (iii) the mouse mammary tumor virus superantigen (sAg) response involving an increase in sAg-reactive T cells and induction of polyclonal antibody production. After vaccinia virus injection into neonates, the polyclonal antibody response was similar to that observed in adult mice. The antibody response to hapten-carrier conjugates, however, was delayed and reduced. Injection with sAg-expressing B cells from neonatal or adult mice allowed us to determine whether B cells, T cells or both were implicated in the reduced immune response. In these sAg responses, neonatal T cells were stimulated by both neonatal and adult sAg-presenting B cells but only B cells from adult mice differentiated into IgM- and IgG-secreting plasma cells in the neonatal environment in vivo. Injecting neonatal B cells into adult mice did not induce antibody production. These results demonstrate that the environment of the neonatal lymph node is able to support a T and B cell response, and that immaturity of B cells plays a key role in the reduced immune response observed in the neonate.

Adoptive Transfer↗

PubMed1998

Antibodies to the C-terminal dipeptide of mouse mammary tumor virus [MMTV(SW)] superantigen effectively inhibit T-cell activation in vivo.

BALB/c mice were immunized against the 19 C-terminal amino acids of the mouse mammary tumour virus [MMTV(SW)] superantigen, either actively with the recombinant ORF19 protein or passively by subcutaneous implantation of 6E1.8 hybridoma cells. Protection against the MMTV(SW) superantigen-induced activation of specific T cells was obtained in both immunizations. Whereas the monoclonal antibody provided complete protection, similar antibody titres showed less effective protection in actively immunized mice. This was due to the presence of a histidine tag on the recombinant ORF19 protein preventing immune recognition of the C-terminal amino acids during immunization. Preincubation of the 6E1.8 monoclonal antibodies with modified ORF19 peptides at their C terminus established specific recognition of the last two amino acids of MMTV(SW) superantigen by this antibody, and showed that these amino acids are critical in the interaction between the MMTV(SW) superantigen and the Vbeta element of the T-cell receptor.

Animals↗

PubMed1997

Immunization with a mouse mammary tumour virus envelope protein epitope protects against tumour formation without inhibition of the virus infection.

BALB/c mice were immunized with the EP3 surface epitope of the mouse mammary tumour virus (MMTV) gp52 envelope protein before systemic infection with MMTV(C3H) or MMTV(SW). Analysis of the successive stages of the virus infection showed that although these mice were protected against mammary tumour formation, earlier stages of the infection were not inhibited, as reflected by the persisting superantigen-induced activation and deletion of Vbeta-specific T cells. Transplacental transfer of maternal anti-EP3 immunoglobulins to newborns did not protect them from infection through the Peyer's patches. Preincubation of the MMTVs with an anti-EP3 serum before injection, however, successfully inhibited the early stages of the infection. Results from this study show that to inhibit infection by MMTV efficiently, the virus must be neutralized before its interaction with the cell membrane, and that the affinity of the virus-membrane interaction is higher than that of the virus-antibody interaction.

Animals↗

PubMed1996

Recombinant fusion peptides containing single or multiple repeats of a ubiquitous T-helper epitope are highly immunogenic.

Two recombinant mouse mammary tumor virus (MMTV) subunit vaccines have been constructed, in which linear sequences of the envelope gp 52 glycoprotein (EP3) or the superantigen (SAg) have been fused to single or multiple repeats of a T-cell epitope (P30) from tetanus toxin. Histidine tags or glutathione-S-transferase (GST) sequences have been included in the recombinant peptides in order to facilitate their purification by affinity chromatography. The EP3 or SAg recombinant polypeptides with four, one, or no T-cell epitopes were expressed in Escherichia coli, purified and injected intramuscularly, with non-ionic block copolymers as an adjuvant, into BALB/c mice. Following one or two boosts, the B- and T-cell responses against the recombinant proteins were analysed. The addition of T-cell epitopes considerably increased the immunogenicity of the subunit vaccines. The anti-EP3 response was maximum with four T-cell epitopes, while a single T epitope was optimal for the anti-SAg response.

Animals↗

PubMed1991

Evaluation of diagnostic procedures in chlamydial eye infection.

Sixty-six patients suffering from suspected chlamydial conjunctivitis or keratoconjunctivitis underwent direct examination and culture procedures on specimens from conjunctival swabs and corneal scraping for detection of Chlamydia trachomatis. Patient blood samples were also screened for the presence of antichlamydia IgG and IgA antibodies. Eye positivity was found in 12 and 15% of patients by using culture isolation and direct examination, respectively. In 3 out of the 8 patients with culture-proven chlamydial eye infection, all of them female, C. trachomatis was also isolated from the genital tract.

Adolescent↗

PubMed1988

Effects of a gluten-free diet on catch-up growth and height prognosis in coeliac children with growth retardation recognized after the age of 5 years.

The effects of a gluten-free diet on catch-up growth and predicted height were evaluated in 12 children with coeliac disease diagnosed after the age of 5 years and followed for 2-5.5 years. In the majority of the patients, height and bone age were retarded at the time of diagnosis. Under a gluten-free diet growth velocity, age-related height, predicted height and relative bone age increased, height for bone age slightly decreased. In four patients the predicted height remained below the target height, indicating incomplete catch-up growth.

Adolescent↗

PubMed1987

[Scintigraphic study of gastric emptying in children with common obesity].

Quantitative gastric emptying essay by a single radio-nuclide technique (Tc99m), utilizing a fluid/solid meal, were performed in 2 groups of age-matched children: (a) 15 males with non-endocrine obesity; (b) 6 males and 3 females affected by gastroesophageal reflux, arbitrarily used as controls. Mean (+/- SD) gastric emptying rates, expressed as emptying half-time (T/2 in min) in the group a and b were superimposable (102.0 +/- 60.6 vs 97.3 +/- 43.1). Our data do not support the existence of an abnormally rapid gastric emptying rate in obesity, at least in pediatric age. This finding is even more striking if one considers that our control group was at high risk for delayed gastric emptying.

Child↗