Biomedical subjects

V Apostolopoulos

Publications and source records attributed to V Apostolopoulos.

At least 19 recordsLinked to original sources

PubMed2006

Alveolar macrophage function is altered in patients with lung cancer.

The alveolar macrophage (AM) is believed to be of central importance in the immune response against infection and tumour. We examined patients with lung cancer in order to evaluate the immuno-stimulatory potential of AM in lung cancer. Bronchoalveolar lavage fluid samples were obtained from patients with adenocarcinoma, squamous cell carcinoma, large cell undifferentiated lung carcinoma, small cell carcinoma and control subjects. AM were isolated and phagocytic function, flow cytometry and cytokine analysis were assessed. AM from patients with small and squamous cell carcinoma had impaired uptake in vitro of 40 nm fluorescent polystyrene beads. AM from patients with small, squamous and large cell undifferentiated carcinoma showed impaired uptake of 1000 nm fluorescent polystyrene beads. Secreted levels of TNF-alpha and IL-1 from AM of patients with small, squamous, and large cell undifferentiated carcinoma were decreased compared to controls. Secreted AM IL-6 levels were decreased in small and large cell undifferentiated carcinoma. AM from adenocarcinoma patients showed similar levels of IL-10, IL-6, IL-1 and TNF-alpha compared to controls. Phenotypic analysis demonstrated that patients with small cell carcinoma were the only group that showed a decrease in MHC class II surface expression. Surface expression of ICAM-1 and CD83 was decreased on AM from patients with large, squamous and small cell carcinoma compared to controls but not adenocarcinoma. Mannose receptor levels were only decreased on AM from patients with squamous and small cell carcinoma but not adenocarcinoma and large cell undifferentiated carcinoma. We conclude that there are type-specific alterations in uptake ability, cytokine secretion and phenotype of AM from lung cancer patients, which may result in an inability to stimulate anti-tumour immunity. The observed differences between lung cancer subgroups may explain previously reported inconsistencies in descriptions of AM characteristics in lung cancer.

Adenocarcinoma↗

PubMed2006

Design of peptide-based vaccines for cancer.

The immune system responds efficiently to bacteria, viruses and other agents however, the immune response to cancers is not as effective. In most cases other than specific genetic rearrangements leading to non-self proteins such as in leukemia and idiotypes in lymphoma, tumor associated proteins are self proteins and are not recognized by the immune system to prevent malignancy. In most cancers, patients develop antibodies and/or CTL-precursors to tumor associated antigens but are not effective in generating a therapeutic immune response. Adjuvants have been used with either whole tumors, subunits or peptides with the aim of increasing their immunity. Whole tumor antigens have certain advantages associated with it, such as ready availability as recombinant proteins, potential epitopes that can be presented by a number of MHC class I/II alleles and antibody development. The methods of identification of CD8 and CD4 epitopes either by use of epitope prediction algorithms or use of transgenic mice has made the use of defined synthetic peptides more attractive. The possibility to synthesize long peptides and introduce multiple epitopes (CD4 or CD8) from single or multiple antigens makes peptide a viable alternative to whole proteins. As an alternative to totally synthetic peptide constructs or polymers, polytopes have been generated by genetic engineering methods. In addition, to deliver immunogens to and to activate DC, receptor-mediated delivery of peptides using antibodies, cytokines and carbohydrates have been used. This review will encompass the various strategies, preclinical and clinical applications in designing peptide-based vaccines for cancer.

Animals↗

PubMed2005

Rational Peptide-based vaccine design for cancer immunotherapeutic applications.

Immune responses to cancer cells can be elicited in vivo by administering synthetic peptides derived from proteins uniquely or overexpressed on tumor cells (tumor associated antigens--TAAs). Peptides derived from TAAs are presented in the context of major histocompatibility complex (MHC) molecules to cytotoxic T cells (CTL), which can recognize and lyze tumor cells. In contrast to peptides derived from an exogenous source (viral or bacterial), tumor peptides bind weakly to MHC class I molecules. The low binding affinity of these peptides makes them poor candidates for vaccination due to the poor immunogenic response produced. In order to enhance antigen recognition and hence immunogenicity, peptide binding affinity for MHC can be initially improved by modifying the "anchor" residues. However, the task at hand is highly unpredictable and minor changes in peptide sequence can alter/abolish the T cell response. Furthermore, despite the wealth of information obtained over the last decade from high resolution X-ray structures of MHC class I in complex with peptides (pMHC) as well as pMHC in complex with T cell receptor (TcR), prediction remains difficult. Nonetheless, peptides represent convenient chemical entities that can be rapidly synthesized in clinical grade for therapeutic applications. Herein, the rationale behind modifying TAAs will be discussed including the synthesis/use of proteolytically tolerant peptides (and peptide mimetics) which incorporate non-natural amino acids, retro-inversion and cyclization to improve bioavailability.

Antigens, Neoplasm↗

PubMed2003

Haemangioblastoma: a rare cause of a cerebellar mass in the elderly.

In the elderly, cerebellar lesions are commonly metastatic tumours with poor prognosis. We describe two octogenarians who presented with obstructive hydrocephalus, secondary to posterior fossa tumours that, on computed tomography, were thought to be cerebellar metastases. Both lesions were excised and the histology proved them to be cerebellar haemangioblastomas, primary benign tumours of the posterior fossa, which are rare in the elderly.

Aged↗

PubMed2002

Use of the mannan receptor to selectively target vaccine antigens for processing and antigen presentation through the MHC class I and class II pathways.

Extensive studies have shown that synthetic and recombinant vaccines developed against hemoparasites have not been as effective as whole parasites or crude membrane fractions in eliciting protective immunity. A possible reason is that synthetic vaccines are not being presented in a form that induces the appropriate immune response. We have developed a bovine model system to evaluate the ability of adjuvant compounds to induce an immune response to peptide antigens dominated by a cytokine profile with a Type 1 (cell-mediated) or Type 2 (humoral) bias. In the initial testing of this system, we found that mRNA expression of certain cytokines (interleukin [IL]-1beta, IL-6, IL-12, IL-15, GM-CSF, iNOS, and tumor necrosis factor [TNF]-alpha) is enhanced when monocyte-derived macrophages are stimulated with peptide antigen conjugated with mannan under oxidizing conditions compared to peptide conjugated with reduced mannan. The data suggest this model will be useful in identifying adjuvant systems that selectively modulate the cytokine profile of antigen presenting cells at the time of antigen presentation and the consequent downstream maturation of naive T cells to effector cells with Type 1 or Type 2 cytokine bias.

Adjuvants, Immunologic↗

PubMed2002

Induction of T helper type 1 and 2 responses to 19-kilodalton merozoite surface protein 1 in vaccinated healthy volunteers and adults naturally exposed to malaria.

Plasmodium falciparum malaria is a major cause of death in the tropics. The 19-kDa subunit of P. falciparum merozoite surface protein 1 (MSP-1(19)), a major blood stage vaccine candidate, is the target of cellular and humoral immune responses in animals and humans. In this phase I trial of MSP-1(19), immunization of nonexposed human volunteers with either of the two allelic forms of recombinant MSP-1(19) induced high levels of antigen-specific Th1 (gamma interferon) and Th2 (interleukin 4 [IL-4] and IL-10) type lymphokines. The adjustment of the antigen dose and number of immunizations regulated the level of specificity of immune responses and Th1/Th2 bias of responses induced by vaccination. Novel conserved and allelic T-cell epitopes which induced cross-strain immune responses were identified. Importantly, responses to many of these novel epitopes were also present in adults exposed to malaria, both in east (Kenya) and west Africa (The Gambia). These data suggest that epitope-specific naturally acquired MSP-1(19) immune responses in endemic populations can be boosted by vaccination.

Adolescent↗

PubMed2002

Applications of peptide mimetics in cancer.

The development of a vaccine for cancer has been difficult compared to the effective vaccines of infectious diseases. Most tumor antigens are not entirely foreign and are expressed on normal tissues, thus, making it difficult to induce strong immune responses against self antigens. A peptide mimic, however, may have the potential to generate greater immune responses than those induced to self peptides. In this review we discuss applications of peptide mimics for cancer immunotherapy which may ultimately prove useful in humans.

Animals↗

PubMed2001

Getting into the groove: unusual features of peptide binding to MHC class I molecules and implications in vaccine design.

The major histocompatibility complex presents antigenic peptides on the surface of antigen presenting cells to T cell receptors. Recognition of peptide-MHC by T cells initiates a cascade of signals in T cells which maintains a T cell dependent immune response. An understanding of the how peptides bind to MHC class I molecules is an important prerequisite in the design of vaccines. Herein, we will discuss, with special emphasis on MUC1, unusual features of MUC1 peptide binding to MHC class I, obtained from vaccine studies including a MUC1 peptide mimic and the crystal structures of low and high affinity peptides lacking canonical anchor motifs in complex with H-2Kb.

Amino Acid Sequence↗

PubMed2001

Anti-mucin monoclonal antibodies.

Mucins are of major interest in cell biology, not only are they highly over-expressed in many adenocarcinomas (up to 40-fold increase), but also have important physiological function, and probably more to be determined (1-3). There is much information available on mucins - doubtless because of their unusual structure being heavily glycosylated, but also containing a repeat region rich in the amino acids serine, threonine and proline. This repeat region confers high immunogenicity of the mucins, and as a result, many antibodies (Abs) have been made to mucins of different species (4). Furthermore, the production of Abs led to the cloning of the cDNAs and armed with these reagents (antibodies, cDNA and genomic structures), advances in the knowledge of the structure and function of mucins has been rapid, together with the development of transgenic and gene knockout animals for biological studies (1-9). Here we describe monoclonal antibodies (Mabs) made to the different mucins, including Mucins 1-4, concentrating on human Mucin 1 (MUC1), to variants of MUC1, to regions outside the VNTR of MUC1, mouse Mucin1 (muc1), unusual features and cross reactions of anti-MUC1 Mabs and Abs made by patients in clinical trials. We will especially describe the Mabs produced in our laboratory.

Animals↗

PubMed2001

A 16-mer peptide (RQIKIWFQNRRMKWKK) from antennapedia preferentially targets the Class I pathway.

Translocation of antigenic peptides into the cytosol of antigen presenting cells facilitates proteosomal processing and loading into Class I molecules for MHC presentation on the cell surface. The DNA binding domain of the Drosophila transcription factor (Antennapedia), a 60 amino acid protein, is rapidly taken up by cells and has been fused to selected antigens to enhance their immunogenicity. We now demonstrate that a 16 amino acid peptide from antennapedia can facilitate the cytoplasmic uptake of CTL epitope 9-mer peptides. Synthetic peptides were made containing the 16-mer antennapedia peptide linked in tandem to the ovalbumin SIINFEKL CTL peptide. The peptide complex was shown to rapidly internalise into APCs by confocal microscopy. This peptide induced CTL in C57BL/6 mice and protected them against growth of an ovalbumin expressing tumour cell line (E.G7-OVA). The ability of the hybrid peptide to be processed and presented by APCs was similar, whether the SIINFEKL sequence was appended at the C-terminus or N-terminus of the Antennapedia peptide. The production of synthetic peptides containing other CTL peptide epitopes may be useful for priming CTLs in vitro and in vivo

Amino Acid Sequence↗

PubMed2001

Designing peptide mimetics for the treatment of multiple sclerosis.

Multiple sclerosis is a chronic inflammatory disease of the central nervous system. While the molecular basis of the disease is still unknown, research effort is currently under progress to prevent or ameliorate its effects. There are two major approaches currently in the pursuing of improved therapeutics for the treatment of multiple sclerosis. The first approach focuses on peptide or mimetic therapy and the second on immunotherapy by preventing or controlling disease through the release of appropriate cytokines.

Amino Acid Sequence↗

PubMed2001

Antihypertensive drugs that act on Renin-Angiotensin System with emphasis in AT(1) antagonists.

Angiotensin II, the primary active hormone in the Renin-Angiotensin System is a major vasoconstrictor implicated in the cause of hypertension. Research efforts have focused in the treatment of disease by blocking its release and more recently by competing its action on AT(1) receptors. This approach generated in the pharmaceutical market, losartan, and other derivatives. To better understand the stereoelectronic requirements that lead to the molecular basis of hypertension the stereochemical features of angiotensin II and its antagonists are studied.

Amino Acid Sequence↗

PubMed2001

Role of the mannose receptor in the immune response.

The mannose receptor (MR) recognizes a range of carbohydrates present on the surface and cell walls of micro-organisms. The MR is primarily expressed on macrophages and dendritic cells and is involved in MR-mediated endocytosis and phagocytosis. In addition, the MR plays a key role in host defense and provides a link between innate and adaptive immunity. Herein, we will review the role of the MR in innate host defense as well as the recent evidence for its role in the adaptive response, for both humoral and cellular immune responses.

Animals↗

PubMed2000

Immunotherapy with mannan-MUC1 and IL-12 in MUC1 transgenic mice.

Mice immunised with oxidised mannan-MUC1 fusion protein (M-FP) develop MHC restricted CD8(+) cytotoxic T cells. We now demonstrate that in MUC1/HLA-A2 transgenic mice, IL-12 gives enhanced CTL, CTLp and tumor protection. CTLp in MUC1 transgenic mice with M-FP were 1/55,000, and with IL-12, this increased to 1/19,000, with improved tumor protection. Thus, IL-12 is important for effective CTL responses to MUC1 in transgenic mice.

Animals↗

PubMed2000

The I-Ag7 MHC class II molecule linked to murine diabetes is a promiscuous peptide binder.

Susceptibility to insulin-dependent diabetes mellitus is linked to MHC class II genes. The only MHC class II molecule expressed by nonobese diabetic (NOD) mice, I-Ag7, shares a common alpha-chain with I-Ad but has a peculiar beta-chain. As with most beta-chain alleles linked to diabetes susceptibility, I-Ag7 contains a nonaspartic residue at position beta57. We have produced large amounts of empty I-Ag7 molecules using a fly expression system to characterize its biochemical properties and peptide binding by phage-displayed peptide libraries. The identification of a specific binding peptide derived from glutamic acid decarboxylase (GAD65) has allowed us to crystallize and obtain the three-dimensional structure of I-Ag7. Structural information was critical in evaluating the binding studies. I-Ag7, like I-Ad, appears to be very promiscuous in terms of peptide binding. Their binding motifs are degenerate and contain small and/or small hydrophobic residues at P4 and P6 of the peptide, a motif frequently found in most globular proteins. The degree of promiscuity is increased for I-Ag7 over I-Ad as a consequence of a larger P9 pocket that can specifically accommodate negatively charged residues, as well as possibly residues with bulky side chains. So, although I-Ad and I-Ag7 are structurally closely related, stable molecules and good peptide binders, they differ functionally in their ability to bind significantly different peptide repertoires that are heavily influenced by the presence or the absence of a negatively charged residue at position 57 of the beta-chain. These characteristics link I-Ag7 with autoimmune diseases, such as insulin-dependent diabetes mellitus.

Amino Acid Motifs↗

PubMed2000

Ex vivo targeting of the macrophage mannose receptor generates anti-tumor CTL responses.

MUC1 is highly expressed in adenocarcinomas and is a possible target for immunotherapy. In mice, oxidized mannan linked to MUC1 (M-FP), given in vivo, induces potent MHC-restricted CTL and tumor protection. Because of the resistance of cancer patients to immunization, ex vivo immunization of macrophage/dendritic cells was examined using oxidized mannan MUC1 to target the mannose receptor and the MHC Class I antigen presentation pathway. Here, we show that murine mannose receptor (MR) bearing macrophages derived from peritoneal exudate cells (PEC) and cultured ex vivo with M-FP can, after adoptive transfer, efficiently present MUC1 to T cells, leading to the generation of high frequency of CTL and protection from tumor challenge. Mice immunized once with syngeneic PEC pulsed with M-FP elicit a similar CTLp frequency to that obtained with three in vivo immunizations. Targeting the MR is crucial to obtain high frequency CTL, and without oxidation the CTLp frequency was low. GM-CSF is important, as GM-CSF o/o mice gave reduced responses, a deficiency corrected by in vivo GM-CSF. In addition, the treatment of macrophages ex vivo with GM-CSF gave enhanced responses and treating mice with GM-CSF prior to M-FP immunizations also enhanced cellular responses. M-FP targets the MR and ensures rapid passage of peptides to Class I molecules, and can also directly stimulate in vitro IL-12 production by macrophages. While many studies are now focussing on dendritic cells, in this study the cells involved were adherent F4/80+ 33D1- macrophages. The findings could be of benefit for the immunization of patients with cancer.

Animals↗

PubMed2000

A structural framework for deciphering the link between I-Ag7 and autoimmune diabetes.

Susceptibility to murine and human insulin-dependent diabetes mellitus correlates strongly with major histocompatibility complex (MHC) class II I-A or HLA-DQ alleles that lack an aspartic acid at position beta57. I-Ag7 lacks this aspartate and is the only class II allele expressed by the nonobese diabetic mouse. The crystal structure of I-Ag7 was determined at 2.6 angstrom resolution as a complex with a high-affinity peptide from the autoantigen glutamic acid decarboxylase (GAD) 65. I-Ag7 has a substantially wider peptide-binding groove around beta57, which accounts for distinct peptide preferences compared with other MHC class II alleles. Loss of Asp(beta57) leads to an oxyanion hole in I-Ag7 that can be filled by peptide carboxyl residues or, perhaps, through interaction with the T cell receptor.

Alleles↗

PubMed2000

Definition of MHC-restricted CTL epitopes from non-variable number of tandem repeat sequence of MUC1.

Mucin1 (MUC1) is expressed ubiquitously on breast cancer cells and is a potential target for the generation of cytotoxic T cells for vaccination against breast cancer. Thus far studies of the immunogenicity of MUC1 have used peptides from the variable number of tandem repeat (VNTR); mice so immunised can generate strong cellular and antibody responses to the VNTR of human MUC1. We now demonstrate that significant CTL and CTLp can be induced to other regions of MUC1. Using the whole native MUC1 molecule, the human milk fat globule membrane antigen (HMFG) linked to mannan, cytotoxic T cell precursors (CTLp) can be generated in BALB/c, C57BL/6, transgenic HLA-A*0201/K(b) and double transgenic HLA-A*0201/K(b)xhuman MUC1 (A2 K(b)MUC1) mice. By immunising with HMFG and testing selectively on (a) extracellular (non-VNTR); (b) VNTR and (c) intracellular peptides, it was shown that all three regions generated effective CTL. Further, the CTL responses to non-VNTR peptides were as strong as those generated to the VNTR. Epitope prediction algorithms were not particularly helpful to describe CTL epitopes: overlapping peptides had to be synthesised and tested to find the epitopes. Thus, for CTL generation, the whole HMFG molecule is a powerful immunogen when linked to mannan, especially as multiple peptide epitopes for presentation by many Class I molecules are contained within the one molecule. Furthermore, Class I restricted MUC1 CTL were generated in double transgenic A2 K(b)MUC1 mice by immunising with mannan-native mucin (HMFG), suggesting that tolerance to MUC1 can be overcome with mannan-HMFG.

Amino Acid Sequence↗