Biomedical subjects

M F Del Guercio

Publications and source records attributed to M F Del Guercio.

7 recordsLinked to original sources

PubMed1999

Pan DR binding sequence provides T-cell help for induction of protective antibodies against Plasmodium yoelii sporozoites.

Pan-DR epitope (PADRE) peptides have demonstrated the capacity to deliver help for antibody responses in vivo. They were also found, fortuitously, to be able to provide significant helper T-cell activity in vivo. This suggested that linear constructs, containing the PADRE epitope, might be as efficient at generating an immune response as large multivalent antigens. Plasmodium falciparum and P. yoelii PADRE constructs were capable of inducing a high titre IgG antibody response that recognized intact sporozoites. We now report that these antibodies can inhibit sporozoite invasion of hepatocytes in vitro and that mice immunized with the PyCSP-PADRE linear construct were protected when challenged with P. yoelii sporozoites.

Amino Acid Sequence↗

PubMed1998

Recognition of a novel naturally processed, A2 restricted, HCV-NS4 epitope triggers IFN-gamma release in absence of detectable cytopathicity.

Using short term CTL lines derived from HLA A2/Kb transgenic mice and IFN-gamma release assays we demonstrate that the NS4.1769 epitope, is generated from natural processing of the NS4 antigen, and presented in the context of the A2/Kb molecules. Interestingly, T cell recognition of the naturally processed form of the NS4. 1769 epitope was associated with significant IFN-gamma release, but no direct cytolytic activity. Epitopes of this phenotype might be of interest, in terms of therapy of chronic HCV infection by associating the benefit of localized lymphokine release with low or absent direct cytopathicity.

Animals↗

PubMed1995

In vitro induction of primary, antigen-specific CTL from human peripheral blood mononuclear cells stimulated with synthetic peptides.

A protocol for in vitro induction of primary, antigen-specific CTL from human peripheral blood mononuclear cells (PBMCs) was developed. Antigen presenting cells (APCs) consisted of Staphylococcus aureus Cowan-I (SAC-I) activated PBMCs treated with a citrate-phosphate buffer at pH 3 to release endogenous peptides bound to surface MHC. This treatment resulted in transient expression of empty class I molecules which could be subsequently stabilized with peptide and beta 2-microglobulin (beta 2m). SAC-I activated PBMCs from HLA-A2.1 normal donors loaded with HBV core 18-27 peptide following acid treatment were used to stimulate PBMCs depleted of CD4+ T cells, in the presence of recombinant interleukin-7 (rIL-7). After 12 days, cells were restimulated with autologous, peptide-pulsed, adherent cells and tested for CTL activity 7 days later. In 23 independent experiments from 13 different HLA-A2.1 donors, this protocol resulted in induction of primary CTL more than 90% of the time. As indicated by both the frequency and magnitude of the response against peptide-sensitized target cells, SAC-I activated PBMCs treated with acid were the most efficient stimulator APC. Thirteen per cent of the cultures generated were capable of lysing target cells transfected with the HBV core antigen and, in general, these CTL cultures exhibited high avidity for the HBV core peptide. This protocol is generally applicable to different antigens and class I alleles, and thus, may be utilized to screen large numbers of peptides to identify human CTL epitopes.

Antigen-Presenting Cells↗

PubMed1994

Identification of potential CTL epitopes of tumor-associated antigen MAGE-1 for five common HLA-A alleles.

Identification of CTL epitopes for tumor-specific responses is important for the development of immunotherapies to treat cancer patients. We have developed a strategy to identify potential CTL epitopes based on screening of sequences of target proteins for presence of specific motifs recognized by the most common HLA-A alleles, and identification of high affinity binding peptides using in vitro quantitative assays. A systematic analysis using the sequence of the product of the tumor-associated MAGE-1 gene has been carried out. All possible peptides of nine and ten residues, containing binding motifs for HLA-A1, -A2.1, A-3.2, -A11 and -A24 were synthesized and tested for binding using a quantitative assay. Out of 237 possible peptide/MHC combinations, 47 cases demonstrated good binding affinity (Kd < or = 500 nM). Several peptides were identified as good MHC binders for each one of the five HLA-A alleles studied (five for HLA-A1, 11 for HLA-A2.1, 10 for HLA-A3.2, 16 for HLA-A11 and five for HLA-A24. Furthermore, eight of these peptides were found to bind well to more than one HLA-A allele. These results have important implications for the development of immunotherapeutic vaccines to treat malignant melanoma.

Amino Acid Sequence↗

PubMed1991

On the interaction of promiscuous antigenic peptides with different DR alleles. Identification of common structural motifs.

We have investigated the interaction between DR1 molecules and the two antigenic peptides, tetanus toxoid 830-843 and hemagglutinin 307-319, previously known to bind most DR alleles (degenerate binding) and to be recognized by the same T cell clones in the context of different DR alleles (promiscuous T cell recognition). The DR1 affinity of these two peptides was compared with that of two other different T cell epitopes (pertussis toxin 30-42 and ragweed allergen Ra3 51-65). It was found that degeneracy and promiscuity were associated with high affinity interactions, whereas binding and T cell selectivity were associated with weaker interactions. Thus, the selectivity of DR-peptide interactions, as is commonly observed with the antibody molecule, appears to be inversely correlated to affinity. Several singly substituted analogs of the hemagglutinin 307-319 determinant have also been tested for capacity to bind various DR alleles (DR1, DR2, DR5, and DR7). The results obtained suggest that this determinant may bind the different DR alleles in a similar orientation. Similar conclusions were reached when the interaction between the tetanus toxoid 830-843 determinant and three different DR alleles (DR1, DR2, and DR7) was studied following the same experimental approach. When crucial DR-binding residues of the two peptides were compared, it was found that they were very similar in both chemical nature and spacing in the peptide primary structure, suggesting that the two peptides may bind DR in a very similar orientation. Finally, a putative motif has been derived and shown to be present in a majority of the DR binders tested, but only in a minority of the non-DR binding peptides.

Alleles↗

PubMed1991

Truncation analysis of several DR binding epitopes.

Peptide regions crucial for binding to four different DR alleles (DR1, DR2, DR5, and DR52a) have been localized in five unrelated DR binding peptides (dynorphin 1-13, sperm whale myoglobin 132-153, influenza hemagglutinin 307-319, pigeon cytochrome c 88-104, and tetanus toxoid 830-843) by testing panels of truncated analogs for DR binding. It was found that in most cases, different DR alleles recognize almost identical, albeit distinct, core regions, suggesting that different DR alleles may recognize similar structures on their peptide ligands. Furthermore, it was found that these core regions, notwithstanding their derivation from unrelated sequences, share a common structural pattern. When the sequences of several other unrelated determinants were scrutinized, the structural motif identified was present in some, but absent in other good DR binders, suggesting that good DR binding capacity of peptide molecules may be compatible with more than one single sequence pattern.

Alleles↗

PubMed1986

B-lymphocyte regulation of the immune system. III. Preparation and characterization of rabbit antibodies that inhibit the biological activity of the lymphokine, B-cell-derived enhancing factor (BEF).

Antibodies that inhibit the biological activity of B-cell-derived enhancing factor (BEF) were produced in a rabbit immunized with BEF obtained from a non-immunoglobulin-producing B-cell line. Immunoglobulin G (IgG) fractions purified from the preimmune or the immune rabbit serum were compared by testing for their capacity to inhibit regulatory activities of BEF. It was found that the enhancing activity exerted by BEF on the in vitro antibody response to sheep red blood cells was inhibited when anti-BEF IgG was incorporated in the cultures. Moreover, anti-BEF IgG abolished the inhibitory activity exerted by BEF on the expression of Fc receptor by lymphoid cells. Comparable concentrations of preimmune IgG were ineffective in inhibiting BEF activity. The passage of supernatant fluid containing BEF activity through an anti-BEF IgG-coupled Sepharose column yielded an 84-fold purified product that exhibit BEF immunoregulatory properties. These results will accelerate further studies aimed at better characterization of the BEF molecule(s).

Animals↗