bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the guaranteed handover algorithm in satellite constellations requiring mutual visibility
Authors: Boedhihartono Poethi , Maral Gérard
Published: March 2003

Handover is one of the key subjects in maintaining the quality of service offered by non‐geostationary constellation systems. As the satellite coverage moves according to the satellite motion, the continuity of a call must be maintained from one satellite to another. In case the handover fails, the call is dropped, resulting in a quality of service degradation.

This paper proposes several handover procedures that guarantee a successful handover in non‐geostationary satellite constellations requiring mutual visibility. Reservations at next satellite must be done in advance in order to avoid call drops. Several handover performance metrics (such as call blocking probability, call dropping probability and handover rate) are presented for each procedure as a function of traffic load variation. Comparisons of handover performance metrics between these procedures are presented as well. Copyright © 2003 John Wiley & Sons, Ltd.
Stability analysis of an adaptive packet access scheme for mobile communication systems with high propagation delays
Authors: Giambene Giovanni , Zoli Enrico
Published: March 2003

In this paper, we investigate a packet access scheme that is able to support mixed traffics in the presence of high propagation delays. Referring to a Time‐Code Division Multiple Access air interface, we propose a Medium Access Control (MAC) protocol based on a random access scheme. A successful attempt grants the use of a slot‐code resource. This protocol is named Adaptive Time Code‐Packet Reservation Multiple Access (ATC‐PRMA), since the access parameters are changed, depending on the traffic load conditions, so as to fulfil Quality of Service requirements. Numerical examples are carried out for the Low Earth Orbit (LEO)‐Mobile Satellite System (MSS) scenario, but all these considerations could be applied to High‐Altitude Platform Stations (HAPSs) as well. In both cases, high propagation delays prevent an immediate feedback to users. An analytical approach is proposed to study the stability of our MAC scheme. Accordingly, we define a criterion for optimizing system performance. The predicted ATC‐PRMA behaviour is supported by simulation results. Finally, we show the performance improvement of ATC‐PRMA with respect to a MAC protocol not employing adaptive parameters. Copyright © 2003 John Wiley & Sons, Ltd.
Probability of finding HLA‐matched unrelated marrow donors for Koreans and Japanese from the Korean and Japan Marrow Donor Programs
Authors: Oh H.B. , Kim S.I. , Park M.H. , Akaza T. , Juji T.
Published: March 2003

This study was performed to assess the probability of finding HLA‐matched donors for Korean and Japanese patients from unrelated marrow donor registries of both countries. A simulation study of donor search was carried out using the donor pools of the Korean Marrow Donor Program (KMDP) with 10,244 and the Japan Marrow Donor Program (JMDP) with 53,411 HLA‐A, ‐B, ‐DR typed donors. The records of a total of 184 actual Korean patients and 1,302 simulated Japanese patients were searched and A, B, DR‐matched donors were found for 28% of Korean and 76% of Japanese patients from the KMDP and JMDP pools, respectively. Of those patients who could not find matched donors in the registry of their own country, 30% of Koreans could find matched donors in the JMDP and 10% of Japanese in the KMDP pools. It can be concluded that future international collaboration between Korea and Japan would be very effective for unrelated bone marrow transplantations.
A new β2 microglobulin mutation found in a melanoma tumor cell line
Authors: Pérez B. , Benitez R. , Fernández M.A. , Oliva M.R. , Soto J.L. , Serrano S. , López Nevot M.A. , Garrido F.
Published: March 2003

β2 microglobulin mutations are an important mechanism for HLA class I total loss, (phenotype No. I) and have been described in colon carcinomas, melanomas and lymphomas. We describe a new β2 microglobulin mutation detected in the melanoma cell line GR‐34. The new mutation reported here was identified as a deletion of 4 bases (TTCT) in the highly repetitive sequence CTCTCTCTTTCT located in the leader sequence of the β2 microglobulin gene at codon 15–16 of exon 1. The mutation produces a frameshift in the open reading frame sequence with the appearance of a stop codon at position 42. We also demonstrate that the second β2 microglobulin gene is deleted. Comparisons with β2 microglobulin mutations in other tumor cell lines suggest a mutation hot spot in exon 1.
DQB1*0602 confers genetic susceptibility to multiple sclerosis in Afro‐Brazilians
Authors: Caballero A. , Alvés‐León S. , Papais‐Alvarenga R. , Fernández O. , Navarro G. , Alonso A.
Published: March 2003

We studied the distribution of the HLA‐DRB1, ‐DQA1 and ‐DQB1 alleles in 44 Afro‐Brazilian patients with multiple sclerosis and 88 controls. Although no significant differences were found between the patients and controls for the DRB1 and DQA1 alleles, the HLA‐DQB1*0602 allele was positively associated with multiple sclerosis (45.0% vs. 17.0%, Pc=0.024, RR=3.31). The positive extended haplotypes for DQB1*0602 were more frequent in patients than controls, although the differences were not statistically significant in any of them. These results in Afro‐Brazilians are in line with other studies which have found DQB1*0602 to be associated with the disease in the absence of the DRB1*1501 allele. We therefore think that the association with the disease in this ethnic group is more allelic than haplotypic.
Melanomas and melanoma cell lines do not express HLA‐G, and the expression cannot be induced by γIFN treatment
Authors: Frumento G. , Franchello S. , Palmisano G.L. , Nicotra M.R. , Giacomini P. , Loke Y.W. , Geraghty D.E. , Maio M. , Manzo C. , Natali P.G. , Ferrara G.B.
Published: March 2003

HLA‐G is an effective ligand of natural killer (NK) inhibitory receptors, HLA‐G transcripts have been detected in several human tumors, and cytokines like γ interferon (IFN) enable HLA‐G molecules to be expressed. These findings are particularly upsetting in case of melanomas: IFN treatment is frequently included in melanoma therapeutic protocols, and downregulation of classical class I molecules occurs in nearly half of these tumors. Therefore, a melanoma cell downregulating classical class I and de novo expressing HLA‐G, either constitutively or upon IFN treatment, is probably a stealthy target for the immune system, having inhibited both the cytotoxic T lymphocyte (CTL) and the NK activity. To elucidate this point we have investigated the expression of HLA‐G molecules in 45 melanoma cell lines before and after γIFN treatment. Analysis was performed by immunofluorescence and flow cytometry, using the anti‐HLA‐G MoAbs 87G and G233, by Western blot, using the anti‐HLA‐G MEM/G1 MoAb and PAG1 antiserum, and by RT‐PCR analysis. In addition, 8 melanoma tissues from patients free from therapy and 6 nevi were studied by immunohistochemistry using the 87G MoAb. No evidence was gathered of HLA‐G expression, neither constitutive nor, in cell lines, after γIFN treatment. We therefore conclude that HLA‐G expression is an uncommon event in melanomas, and that a therapy including IFNs cannot harm the patient by inducing the de novo expression of HLA‐G molecules at least in its G1 isoform.
Production and characterization of monoclonal antibodies against conserved epitopes of P‐selectin (CD62P)
Authors: Massaguer A. , Engel P. , Pérez‐del‐Pulgar S. , Bosch J. , Pizcueta P.
Published: March 2003

P‐selectin (CD62P) is an adhesion molecule expressed on the activated endothelium and activated platelets that is involved in the initial attachment of leukocytes to inflamed vascular endothelium. Blocking monoclonal antibodies (mAbs) and P‐selectin‐deficient mice have shown that P‐selectin is a potential target in anti‐inflammatory therapy. Most mAbs against P‐selectin do not bind to conserved epitopes, including the ligand‐binding region, since P‐selectin from mammalian species shares high amino acid sequence homology. The aim of this study was to generate a novel panel of anti‐P‐selectin mAbs against the conserved epitopes present in several animal species. To produce these mAbs, P‐selectin‐deficient mice were immunized with a pre‐B‐cell line transfected with human P‐selectin cDNA. Twelve mouse mAbs that recognize human P‐selectin were obtained. Individual mAbs that bound to human, rat, mouse, rabbit and pig activated platelets were characterized by flow‐cytometry, immunohistochemistry, adhesion assays and immunoprecipitation. Four of these mAbs (P‐sel.KO.2.3, P‐sel.KO.2.4, P‐sel.KO.2.7 and P‐sel.KO.2.12) cross‐reacted with human, rat and mouse P‐selectin. Another three mAbs (P‐sel.KO.2.2, P‐sel.KO.2.11 and P‐sel.KO.2.12) blocked the attachment of HL60 cells to P‐selectin‐transfected COS cells, demonstrating that these mAbs inhibit P‐selectin‐mediated adhesion. MAb cross‐blocking experiments showed that these three mAbs bind to very close and overlapping epitopes. An ELISA assay using mAbs P‐sel.KO.2.3 and P‐sel.KO.2.12 was designed to measure soluble rat, mouse and human P‐selectin. These anti‐P‐selectin mAbs are unique since they recognize common epitopes conserved during mammalian evolution and they may be useful for studying P‐selectin function in inflammatory models in various species.
Identification of two novel human CD1E alleles
Authors: Mirones I. , Oteo M. , Parra‐Cuadrado J.F. , Martínez‐Naves E.
Published: March 2003

CD1 is a family of proteins structurally related to major histocompatibility complex (MHC) molecules and specialized in presenting lipids or glycolipids to T cells. In humans, there are five CD1 genes (CD1A to CD1E). It has been shown that, in contrast with classical MHC genes, CD1 loci display a very limited polymorphism. In the present work we describe two novel CD1E alleles found in two healthy Caucasian individuals. One allele differs from the wild‐type by a point mutation resulting in a replacement of arginine at position 154 by a tryptophan. In the second allele we found a substitution of the leucine 184 by a proline.
The molecular determination of HLA‐Cw alleles in the Mandenka (West Africa) reveals a close genetic relationship between Africans and Europeans
Authors: Sanchez‐Mazas A. , Steiner Q.‐G. , Grundschober C. , Tiercy J.‐M.
Published: March 2003

HLA‐Cw alleles were determined by high‐resolution polymerase chain reaction‐sequence‐specific oligonucleotide probe (PCR‐SSOP) oligotyping in a sample of 165 Mandenka, a population from Eastern Senegal previously analysed for A/B and DRB/DQB polymorphisms. A total of 18 Cw alleles were identified, with Cw*0401/5 and 1601 accounting for a combined frequency of 36%. A comparison of Cw allele frequencies among several populations of different origins, Mandenka, Swiss, English, Ashkenazi Jews from the UK and Japanese, reveals a high genetic heterogeneity among them, but also a much closer relationship between Mandenka, Europeans and Ashkenazi than between any of these populations and Japanese. Cw*0501, Cw*0701 and Cw*1601, among others, appear to be restricted to the European and African populations. Many B‐Cw haplotypes exhibit a significant linkage disequilibrium in the Mandenka, among which B*3501‐Cw*0401 and B*7801‐Cw*1601, formed by the most frequent B and Cw alleles, and B*5201‐Cw*1601, B*5702‐Cw*18 and B*4410‐Cw*0401, not yet observed in other populations. B*3501‐Cw*0401 is found with similar frequencies in Europeans. The results possibly support a close historical relationship between Africans and Europeans as compared to East Asiatics. However, the HLA‐Cw frequency distributions are characterised by an excess of heterozygotes, indicating that balancing selection may have played a role in the evolution of this polymorphism.
Development of a PCR‐SSOP approach capable of defining the natural killer cell inhibitory receptor (KIR) gene sequence repertoires
Authors: Crum K.A. , Logue S.E. , Curran M.D. , Middleton D.
Published: March 2003

A molecular typing method based on polymerase chain reaction (PCR) amplification of three different target domains (immunoglobulin domains 1 and 3, and the transmembrane‐cytoplasmic domain), followed by hybridisation with 26 digoxigenin‐labelled sequence‐specific oligonucleotide probes (SSOP) has been established for the polymorphic killer inhibitory receptor (KIR) genes. In addition to identifying the 12 KIR subfamilies, our PCR‐SSOP typing approach could also distinguish the putative alleles, NKB1 and NKAT3, that comprise the KIR3DL1 subfamily. Ninety unrelated blood donors and 13 families (52 individuals), including both parents, were subjected to our KIR PCR‐SSOP typing approach. All 12 KIR subfamilies, including a 2DS5 variant sequence, were present in the 90 individuals and displayed varied phenotype frequencies: 2DL1 (0.96), 2DL2 (0.31), 2DL3 (0.95), 2DS1 (0.56) 2DS2 (0.51), 2DS3 (0.27), 2DS4 (0.96), 2DS5v (0.35), 3DS1 (0.47), 3DL1 (0.96), 3DL2 (1.0) and 2DL4 (1.0). A total of 23 different KIR phenotypes were defined in this study, and 10 of these were only found on one occasion in one individual, indicating considerable diversity in the KIR phenotype profiles within the Irish population. Most individuals (93%) possessed the complement of inhibitory KIR specificities for the three well‐defined HLA‐B and ‐C ligands. An unusual probe pattern for 3DS1 was observed in 3 individuals indicating a variant 3DS1 gene sequence with changes at nucleotide positions 1185–1186, within the cytoplasmic domain. Sequencing analysis revealed a new single nucleotide polymorphism in exon 3 of 3DL1 NKB1(195, G‐A) and a 22‐bp deletion polymorphism in exon 5 of 2DS4 (nucleotides 777–798 deleted). A number of strong KIR associations were observed, namely 2DL1 with 2DL3, 2DS4 with 3DL1, 2DL2 with 2DS1/2DS2/2DS3, 2DS1 with 2DS3/2DS5v/3DS1, 2DS2 with 2DS3 and 2DS5v with 3DS1. Analysis of the KIR segregation observed in the 13 families confirmed these strong associations and permitted the definition of a number of partial KIR haplotypes, e.g. 2DL2‐2DS1‐2DS2‐2DS3‐3DL1. The segregation analysis concluded that at least 3 distinct gene loci encode 2DL1‐4 and at least 4 gene loci encode the non‐inhibitory KIR2DS1‐2DS5. In the case of 3DL1‐2 and 3DS1, our data suggests 3 gene loci, one for each subfamily.
Coordinate downregulation of multiple MHC class I antigen processing genes in chemical‐induced murine tumor cell lines of distinct origin
Authors: Seliger B. , Wollscheid U. , Momburg F. , Blankenstein T. , Huber C.
Published: March 2003

In murine tumor cell lines, downregulation of MHC class I surface expression has been frequently detected, but the underlying molecular mechanisms of such deficiencies have not been defined. In this study, murine tumor cell lines of different histology derived from spontaneous or from chemical‐induced tumors were analyzed for the expression of multiple components of the major histocompatibility complex (MHC) class I antigen‐processing machinery (APM), including the peptide transporter TAP, the interferon (IFN)‐γ inducible proteasome subunits and several chaperones. The tumor cell lines analyzed demonstrated a heterogeneous expression pattern of various APM components. In comparison to control cells an impaired coordinated expression of at least three APM components was detected. In particular, extensive APM deficiencies were found in cell lines derived from chemical‐induced tumors. A strong coordinated downregulation of expression and/or function of TAP, the low molecular weight proteins (LMP) subunits, the proteasome activator PA28 and/or tapasin was found in 5 of 10 tumor cells, which was associated with impaired MHC class I surface expression. In contrast, the expression of β2‐microglobulin (β2‐m), PA28β, the constitutive proteasome subunits X, Y, Z and of the chaperones calnexin, calreticulin, ER60 and phospho disulfide isomerase (PDI) was unaltered or only weakly decreased. The deficient expression of APM components could be corrected by IFN‐γ treatment, which also reconstituted MHC class I surface expression. However, impaired expression of APM molecules appears not to be the only cause of abnormal MHC class I expression, since it could neither be corrected by the addition of exogeneous MHC class I binding peptides nor by incubation at low temperature. These results suggest that one major mechanism of murine tumor cells, in particular chemical‐induced tumors, to evade the immune system is the combined dysregulation of various APM components and other factors, which still have to be identified.
HLA alleles and haplotypes in the Turkish population: relatedness to Kurds, Armenians and other Mediterraneans
Authors: Arnaiz‐Villena A. , Karin M. , Bendikuze N. , Gomez‐Casado E. , Moscoso J. , Silvera C. , Oguz F.S. , Sarper Diler A. , De Pacho A. , Allende L. , Guillen J. , Martinez Laso J.
Published: March 2003

Abstract: Turkish and Kurdish HLA profiles are studied for the first time. The comparative study of their allele frequencies, characteristic haplotypes, genetic distances with other Mediterraneans is complemented by neighbor‐joining dendrograms and correspondence analyses. Turks, Kurds, Armenians, Iranians, Jews, Lebanese and other (Eastern and Western) Mediterranean groups seem to share a common ancestry: the older “Mediterranean” substratum. No sign of the postulated Indo‐European (Aryan) invasion (1200 B.C.) is detected by our genetic analysis. It is concluded that this invasion, if occurred, had a relatively few invaders in comparison to the already settled populations, i.e. Anatolian Hittite and Hurrian groups (older than 2000 B.C.). These may have given rise to present‐day Kurdish, Armenian and Turkish populations.
Protective and susceptible HLA polymorphisms in IgA nephropathy patients with end‐stage renal failure
Authors: Doxiadis I.I.N. , De Lange P. , De Vries E. , Persijn G.G. , Claas F.H.J.
Published: March 2003

Abstract: Idiopathic immunoglobulin A (IgA) nephropathy is characterised by an extreme variability in clinical course, leading to end‐stage renal failure in 15–20% of adults. This subgroup of patients with IgA nephropathy is usually included in the waiting lists of organ exchange organisations. The frequency of HLA‐A,B,DR antigens of this subset of IgA nephropathy patients was calculated and compared to controls. The antigens HLA‐B35 and DR5 were significantly increased in the patients with relative risk values of 1.385 and 1.487, respectively. The antigens HLA‐B7, B8, DR2, and DR3 were found in a significantly lower frequency in the patients as compared to the controls. The relative risk (RR) values ranged between 0.695 and 0.727. Consequently, the haplotypes HLA‐A1, B8, DR3, HLA‐A3, B7, DR2, HLA‐A2, B7, DR2 together with HLA‐A1, B15, DR4, HLA‐A9, B12, DR7, and HLA‐A10, B18, DR2 were found to be protective with RR values ranging from 0.309 to 0.587. The only susceptible haplotype observed was HLA‐A2‐B5, DR5 (RR=2.990) (Note).
Quantitative predictions of peptide binding to MHC class I molecules using specificity matrices and anchor‐stratified calibrations
Authors: Lauemøller S.L. , Holm A. , Hilden J. , Brunak S. , Holst Nissen M. , Stryhn A. , Østergaard Pedersen L. , Buus S.
Published: March 2003

Abstract: Peptides are key immune targets. They are generated by fragmentation of antigenic proteins, selected by major histocompatibility complex (MHC) molecules and subsequently presented to T cells. One of the most selective requirements is that of peptide binding to MHC. Accurate descriptions and predictions of peptide‐MHC interactions are therefore important. Quantitative matrices representing MHC class I specificity can be used to search any query protein for the presence of MHC binding peptides. Assuming that each peptide residue contributes to binding in an additive and sequence independent manner, such “crude” matrix‐driven predictions can be expressed as a quantitative estimates of binding strength. Crude matrix‐driven predictions are reasonably uniform (i.e. precise), however, there is a general tendency towards overestimating binding (i.e. being inaccurate). To evaluate and possibly improve predictions, we have measured the MHC class I binding of a large number of peptides. In an attempt to further improve predictions and to include sequence dependency, we subdivided the panel of peptides according to whether the peptides had zero, one or two primary anchor residues. This allowed us to define unique anchor‐stratified calibrations, which led to predictions of improved precision and accuracy.
Novel HLA‐B alleles associated with antigens in the 7C CREG
Authors: Steiner N.K. , Jones P. , Kosman C. , Edson S. , Rizzuto G. , Gans C.P. , Mitton W. , Koester R. , Rodriguez‐Marino S.G. , Ng J. , Hartzman R.J. , Hurley C.K.
Published: March 2003

Abstract: This paper describes 9 novel HLA‐B locus alleles. All of the alleles carry sequence motifs observed in other HLA‐B alleles.
Differential tissue expression of epitopes of the tetraspanin CD151 recognised by monoclonal antibodies
Authors: Geary S.M. , Cambareri A.C. , Sincock P.M. , Fitter S. , Ashman L.K.
Published: March 2003

Abstract: CD151, a member of the tetraspanin family of cell membrane proteins, is widely expressed in epithelial, endothelial and muscle cells as well as platelets and megakaryocytes. Several monoclonal antibodies recognising CD151 in transfected cells and immunoprecipitating typical bands of 28 and 32 kDa from cell lysates have been produced. Surprisingly, these antibodies show different patterns of staining on tissue sections and on haemopoietic cells. Here we show that these differences are at least in part due to masking of certain epitopes in integrin/CD151 complexes. These data have important implications for the use of monoclonal antibodies in studies of the distribution and function of CD151. Of six monoclonal antibodies from four laboratories, 11B1 was found to be the most reliable for detection of CD151 in different cell and tissue contexts.
Identification of a novel DR4 allele, DRB1*0442
Authors: Dunn T.A. , Iglehart B.A. , Leffell M.S.
Published: March 2003

Abstract: A new DRB1 allele encoding DR4, DRB1*0442, was identified in three Caucasian siblings by reverse in‐line hybridization and defined by sequencing based typing. The DRB1*0442 allele differs from DRB1*0404 by a single nucleotide at position 227 (T→A) of codon 47 in exon 2. At the amino acid level, this substitution results in a change from tyrosine to phenylalanine. Serologically, the new allele appears to retain the DR4 antigenicity; however, this substitution may affect peptide‐binding specificity.
Genetic predispositions for the presence of cryoglobulinemia and serum autoantibodies in Chinese patients with chronic hepatitis C
Authors: Hwang S.‐J. , Chu C.‐W. , Huang D.‐F. , Lan K.‐H. , Chang F.‐Y. , Lee S.‐D.
Published: March 2003

Abstract: Chronic hepatitis C virus (HCV) infection may induce immunological disorders in the host such as the presence of cryoglobulinemia or serum autoantibodies. The pathogenesis of these phenomena remains unclear but may reflect the host's genetic predispositions. The aim of this study was to evaluate the association between these immunological manifestations and human leukocyte antigen (HLA) expression in Chinese patients with chronic hepatitis C. The presence of serum cryoglobulin and autoantibodies (antinuclear antibody, antismooth muscle antibody, antimitochondrial antibody, antiliver‐kidney‐microsomal antibody) was determined in 122 Chinese patients with chronic hepatitis C. HLA class I and class II antigens were measured by microlymphocytotoxicity assay or by DNA typing in 122 chronic hepatitis C patients and 228 healthy controls. Of the 122 patients with chronic hepatitis C, 52 (43%) had cryoglobulinemia and 48 (39%) had serum autoantibodies. A significant difference in HLA frequency was noted for DR3, which was found in 36.5% of patients with cryoglobulinemia compared with 8.6% of patients without cryoglobulinemia and 11.3% of healthy controls. A significant difference in HLA frequency was also noted for DR4, which was found in 45.8% of patients with serum autoantibodies compared with 17.6% of patients without serum autoantibodies and 19% of healthy controls. Our results suggest the existence of HLA‐linked susceptibility genes (DR3 or DR4) for the development of cryoglobulinemia or serum autoantibodies in Chinese patients with chronic hepatitis C.
Identification of a new HLA‐B*15 allele, HLA‐B*1569
Authors: Smillie D.M. , Smith P.A. , Day S. , Dunn P.P.J.
Published: March 2003

Abstract: We have identified a new HLA‐B*15 allele (B*1569) by polymerase chain reaction (PCR) using sequence‐specific primers (SSP) and sequence‐based typing (SBT). This novel allele was found in a 67‐year‐old white Caucasian male and differs from HLA‐B*1503 at 3 positions. The nucleotide substitutions at positions 544, 559 and 560 result in amino acid changes at codon 158 from GCC (alanine) to ACC (threonine), and at codon 163 from CTG(leucine) to ACG (threonine).
CTL: Caspases Terminate Life, but that's not the whole story
Authors: Waterhouse N.J. , Trapani J.A.
Published: March 2003

Abstract: The induction of cell death by cytotoxic T‐lymphocytes (CTL) or natural killer (NK) cells is one of the main ways by which higher organisms protect themselves from rogue cells, including those infected by a virus, or posing a risk of cancer. Considering the rapidity of viral replication and spread to uninfected cells, CTL and NK are extremely efficient killers. This is at least partly due to the variety of pathways that these cytolytic lymphocytes (CL) can use to ensure the death of a cell. Primarily, CL utilize two independently initiated pathways involving either ligation of death receptors or perforin mediated trafficking of granzyme B to the target cell cytosol to activate a family of death proteases (caspases) in the target cell. The caspases then orchestrate the orderly dismantling of that cell by cleavage of a set of critical substrates. If caspases are inactivated, due either to mutations in proteins that signal their activation or direct inhibition by a viral gene product, CL can utilize a caspase‐independent pathway to ensure the death of the target cell. Here we will discuss the mechanisms by which these stellar killers achieve their goal.
HLA‐DRB1 and DQB1 allele distribution in the Muong population exposed to malaria in Vietnam
Authors: Busson M. , Vu Trieu A. , Labelle P. , Pham‐Van K. , Ho‐Quang H. , Bouteiller A.M. , Bleux H. , Charron D. , Hors J.
Published: March 2003

Abstract:The distribution of 30 HLA‐DRB1 alleles in 85 individuals and of 10 HLA‐DQB1 alleles in 91 individuals of the Viet Muong population was studied and compared with those of nine other Asian populations, including 103 Viet Kinh belonging to the major ethnic group in Vietnam. In terms of genetic distance, our data are consistent with a close ethnogeographic relationship between Viet Muong, Buyi and Dai Lue, two Southern Chinese ethnic groups. Conversely, these three populations are distant from the Northern Chinese population. The Viet Kinh belong to an intermediate group, together with North‐eastern Thais, Thais and present day Thais. The striking presence of the HLA‐DQ1*0502 allele (48% frequency) in the Viet Muongs is possibly anthropological or environmental in origin: the Viet Muongs have been submitted to endemic malaria for centuries, and the survivors carry the protective trait of glucose‐6‐phosphate dehydrogenase deficiency. This raises the hypothesis of a possible resistance to lethal or severe forms of the disease, where the association with a specific HLA‐DQB1 allele may play a role.
Additional association of intra‐MHC genes, MICA and D6S273, with Addison's disease
Authors: Park Y.S. , Sanjeevi C.B. , Robles D. , Yu L. , Rewers M. , Gottlieb P.A. , Fain P. , Eisenbarth G.S.
Published: March 2003

Abstract: Intra‐MHC sequences including MHC class I chain‐related genes (MICAs), D6S273 and D6S2223 are associated with autoimmune diseases in addition to HLA class II. In the current study, we ascertained the haplotypes of 57 Caucasian patients with Addison's disease composed of these genetic markers and compared them either with 72 general population controls or with 105 child controls carrying Addison's disease high‐risk DR3‐DQ2/DR4‐DQ8 genotypes. The MICA‐A5.1/A5.1 genotype as well as HLA DR3/4 especially with DRB1*0404 were the main susceptibility markers. The homozygous MICA‐A5.1/A5.1 genotype was significantly more frequent in the patients with Addison's disease (61%) than in the healthy controls (6%). The MICA‐A5.1 allele was increased on both the DR3 and DR4 haplotypes, independent of DQ and DRB1 subtyping, in the patients with Addison's disease compared with the controls. Furthermore, the D6S273*140 allele on the DR3 haplotype and the D6S273*134 allele on the DR4 haplotype in the DR3/4 heterozygotes influenced susceptibility relative to the DR3/4 controls. The risk for Addison's disease was increased for the DR3‐D6S273*140‐MICA‐A5.1/DRB1*0404‐D6S273*134‐MICA‐A5.1 genotypes compared with that conferred by the DR3/4 controls. Susceptibility to Addison's disease is influenced by the genes around MICA and D6S273 for both the HLA DR3‐DQ2 and DR4‐DQ8 haplotypes.
Identification of a new HLA‐A null allele, A*2436 N
Authors: Li J. , Den Hollander N. , Van Oosterwijk A. , Ng C‐M. , Singal D.P.
Published: March 2003

Abstract: We describe a new HLA‐A null allele in a donor. This null allele resulted from the deletion of two nucleotides in exon 2, which effects a frameshift as well as a premature stop codon. This new null allele has been officially named HLA‐A*2436 N.
A male genital tract‐specific carbohydrate epitope on human CD52: Implications for immunocontraception
Authors: Norton E.J. , Diekman A.B. , Westbrook V.A. , Mullins D.W. , Klotz K.L. , Gilmer L.L. , Thomas T.S. , Wright D.C. , Brisker J. , Engelhard V.H. , Flickinger C.J. , Herr J.C.
Published: March 2003

Abstract: The identification of unique sperm surface epitopes that are not expressed or exposed in the female reproductive tract is a key element in the development of antibody‐based contraceptives. Western blotting and immunohistochemistry were performed to define the tissue distribution of the S19 epitope, which has been proposed as a target for immunocontraception. S19 is an IgG1 murine monoclonal antibody (mAb) directed to an N‐linked carbohydrate epitope on a 15–25 kDa glycoprotein, sperm agglutination antigen‐1 (SAGA‐1), containing a peptide core identical to that of the lymphocytic surface protein CD52. In this study, the S19 epitope was shown to be absent from human lymphocytes, demonstrating a distinction between this epitope and the CAMPATH epitope that is recognized by an antibody against the terminal tripeptide and GPI‐anchor of CD52. Further tissue specificity analysis identified the S19 epitope in the epithelium of the human epididymis and vas deferens, as well as on both epididymal and ejaculated spermatozoa. In contrast, the S19 epitope was absent in the five human female reproductive tract and 18 other somatic tissues tested. These results support the use of the S19 epitope as a contraceptive immunogen and the suitability of the S19 mAb as an intravaginal contraceptive. To test the agglutinating activity of the S19 mAb in a formulation designed for vaginal use, S19 mAb were bound to the surface of Novasomes, a multilamellar liposome delivery vehicle. S19‐Novasome formulations agglutinated human spermatozoa and were as effective as unbound S19 mAb, demonstrating the feasibility of spermistatic contraceptives targeted to the male reproductive tract specific carbohydrate epitope.
Immunogenetic study of a new HLA allele, B*2723
Authors: Darke C. , Street J. , Hammond L. , Downing J. , Thompson J.
Published: March 2003

Abstract:A novel HLA‐B*27 allele (B*2723) detected by irregular serological and PCR‐SSP typing results was identified by nucleotide sequencing of exons 2 and 3. B*2723 differs from B*27052 by nine nucleotides which encode seven amino acid changes at positions 63 (Glu to Asn), 67 (Cys to Phe), 69 (Ala to Thr), 70 (Lys to Asn), 71 (Ala to Thr), 74 (Asp to Tyr) and 77 (Asp to Ser) in the α1 helix. All these substitutions are possessed by B*35 alleles suggesting that B*2723 was created by a gene conversion‐like event involving B*27052 and a B*35 allele. Using the HLA‐A*26 and DRB1*12 alleles of the B*2723‐bearing haplotype as ‘markers’, two further examples of B*2723 were found in 29,851 blood donors. Therefore, B*2723 has a ‘minimum’ gene frequency of 0.000034 (phenotype frequency 0.0067%) in blood donors resident in Wales. In all three families, B*2723 was present on a haplotype with: A*26; Cw*0202; DRB1*1201/6/7; DRB3*02; DQA1*05; DQB1*0301. The B*2723 product failed to react with HLA‐B27 antisera and reacted weakly or not at all with Bw4 antisera. Lack of the ECAKA motif at amino acid positions 63, 67, 69–71 probably accounts for lack of the B27 specificity while the amino acid combination 74Y, 77S, 80T, 81L may cause aberrant Bw4 reactivity.
Cluster of TRIM genes in the human MHC class I region sharing the B30.2 domain
Authors: Meyer M. , Gaudieri S. , Rhodes D.A. , Trowsdale J.
Published: March 2003

Abstract: The major histocompatibility complex (MHC), a region of high gene density, contains a large number of genes relevant to the immune response, belonging to different multigenic families. We studied the genomic organization and polymorphism of a set of genes in the MHC class I region containing the tripartite motif (TRIM), consisting of a RING domain, B‐box and coiled coil region, and a B30.2‐like domain. A cluster of seven genes at 6p21.33 and two related family members telomeric of the cluster were characterized. All MHC‐encoded TRIM‐B30.2 genes showed moderate levels of polymorphism, affecting predominantly the RING and B‐box domains. In terms of structure, the genes varied by the loss of partial and, in some cases, complete domains. They were strongly conserved in exons 2, 3 and 4, which form the coiled‐coil region. The last exon, encoding the B30.2‐like domain, is shared with the otherwise unrelated butyrophilin‐like (BTN) genes, located 4.3 Mb telomeric of the TRIM‐B30.2 cluster. The data are consistent with multiple, ancient duplications giving rise to a set of related genes.
Molecular dynamics study of disulfide bond influence on properties of an RGD peptide
Authors: Wang Y. , Goh S.‐Y. , Kuczera K.
Published: March 2003

Three 1 ns length molecular dynamics simulations of an RGD peptide (Ac‐Pen‐Arg‐Gly‐Asp‐Cys‐NH2, with Pen denoting penicillamine) have been performed in aqueous solution, one for the disulfide bridged, and two for the unbridged form. The trajectories were analyzed to identify conformations explored by the two forms and to calculate several properties: NMR vicinal coupling constants, order parameters, dipole moments and diffusion coefficients, in an effort to describe the physical role of the disulfide bond. The cyclic peptide was able to explore several distinct backbone conformations centered around a turn–extended‐turn structure. However, its flexibility was limited and it appeared to be ‘locked in’ into a a family of structures characterized by a high dipole moment and a well‐defined conformation of the pharmacophore, which has been previously identified as biologically active. Excellent agreement between the simulated and observed NMR vicinal coupling constants indicates that realistic structures were sampled in the cyclic peptide simulation. The linear form of the peptide was much more flexible than the cyclic one. In the two independent 1 ns simulations of the linear form the explored conformations could be roughly grouped into two classes, of cyclic‐like and extended type. Within each simulation the peptide switched between the two classes of structures several times. Exact matches between conformations in the two linear peptide simulations were not found; several conformational regions with backbone rms deviations below 1 Å were identified, suggesting that representative structures of the linear form have also been identified. In the linear peptide simulations the RGD pharmacophore is able to adopt a wide range of conformations, including the one preferred by the cyclic form. The lower biological activity of the linear peptide compared to the cyclic one may be correlated with the lower population of this structure in the absence of the disulfide bond.
The nature of the bond between peptide and carrier molecule determines the immunogenicity of the construct
Authors: Beekman N. J. C. M. , Schaaper W. M. M. , Langeveld J. P. M. , Boshuizen R.S. , Meloen R.H.
Published: March 2003

Abstract: The influence of the nature of the bond between a peptide and a (lipidic) carrier molecule on the immunogenicity of that construct was investigated. As types of bonds a thioester‐, a disulfide‐, an amide‐ and a thioether bond were investigated. As carrier molecules a peptide, an N‐palmitoylated peptide or a C16‐hydrocarbon chain were used. The biostability of the bond between peptide and carrier molecule is thioether > amide > disulfide ≫ thioester. However, the immunogenic potency of the constructs used was found to be thioester > disulfide > amide > thioether. In conclusion, a construct with a bond between peptide and (lipidic) carrier molecule that is more susceptible to biological degradation is more immunogenic when used in a peptide‐based vaccine than a bond that is less susceptible to biological degradation.
Antibacterial, antitumor and hemolytic activities of α‐helical antibiotic peptide, P18 and its analogs
Authors: Shin S.Y. , Yang S.‐T. , Park E.J. , Eom S.H. , Song W.K. , Kim J.I. , Lee S.‐H. , Lee M.K. , Lee D.G. , Hahm K.‐S. , Kim Y.
Published: March 2003

Abstract: The α‐helical antibiotic peptide (P18: KWKLFKKIPKFLHLAKKF‐NH2) designed from the cecropin A(1–8)–magainin 2 (1−12) hybrid displayed strong bactericidal and tumoricidal activity without inducing hemolysis. The effect of the Pro9 residue at central position of P18 on cell selectivity was investigated by Pro9 → Leu or Pro9 → Ser substitution. Either substitution markedly reduced the antibacterial activity of P18 and increased hemolysis, although it did not significantly affect cytotoxicity against human transformed tumor and normal fibroblast cells. These results suggest that a proline kink in α‐helical antibiotic peptide P18 serves as a hinge region to facilitate ion channel formation on bacterial cell membranes and thus plays an important role in providing high selectivity against bacterial cells. Furthermore, to investigate the structure−antibiotic activity relationships of P18, a series of N‐ or C‐terminal deletion and substitution analogs of P18 were synthesized. The C‐terminal region of P18 was related to its antibiotic activity and α‐helical conformation on lipid membranes rather than N‐terminal one. Higher α‐helicity of the peptides was involved in the hemolytic and antitumor activity rather than antibacterial activity. Except for [L9]‐P18 and [S9]‐P18, all the designed peptides containing a Pro residue showed potent antibacterial activity, although they did not induce a cytolytic effect against human erythrocyte and normal fibroblast cells at the concentration required to kill bacteria. In particular, P18 and some analogs (N‐1, N‐2, N‐3, N‐3L and N‐4L) with potent bactericidal and tumoricidal activity and little or no normal cell toxicity may serve as an attractive candidate for the development of novel anti‐infective or antitumor agents.
The cytoplasmic helix of cannabinoid receptor CB2, a conformational study by circular dichroism and 1H NMR spectroscopy in aqueous and membrane‐like environments
Authors: Choi G. , Landin J. , Xie X.‐Q.
Published: March 2003

Abstract: The cytoplasmic helix domain (fourth cytoplasmic loop, helix 8) of numerous G protein‐coupled receptors (GPCRs) such as rhodopsin and the β‐adrenergic receptor exhibit unique structural and functional characteristics. Computer models also predict this structure for the cannabinoid CB2 receptor, another member of the GPCR superfamily. In our study, a peptide corresponding to helix 8 of the CB2 receptor was synthesized chemically and its secondary structure determined by circular dichroism (CD) and 1H NMR spectroscopy. NMR and CD revealed an α‐helical structure in this region in both dodecylphosphocholine micelles and dimethylsulfoxide, in contrast to a random coil configuration found in aqueous solvent. This finding is in good agreement with other previous GPCR structural studies including X‐ray crystallography. By combining our finding with other studies, we further hypothesize that the amphipathic nature of helix 8 can play a significant role in the function and regulation of CB receptors as well as other GPCRs in general.
Design, expression, and characterization of a synthetic human cannabinoid receptor and cannabinoid receptor/ G‐protein fusion protein
Authors: Farrens D. L. , Dunham T. D. , Fay J. F. , Dews I. C. , Caldwell J. , Nauert B.
Published: March 2003

Abstract: We report here the synthesis and characterization of two gene constructs designed to facilitate structure/function studies of the human neuronal cannabinoid receptor, CB1. The first gene, which we call shCB1, is a synthetic gene containing unique restriction sites spaced roughly 50–100 bases apart to facilitate rapid mutagenesis and cloning. A nine amino acid epitope tag (from the rhodopsin C‐terminus) is also present in the shCB1 C‐terminal tail to enable detection and purification using the monoclonal antibody 1D4. We find that that the shCB1 gene can be transiently expressed in COS cells with yield of ∼ 10–15 µg receptor per 15 cm plate and is wild type like in its ability to bind cannabinoid ligands. Our confocal microscopy studies indicate shCB1 targets to the membrane of HEK293 cells and is internalized in response to agonist. To facilitate functional studies, we also made a chimera in which the C‐terminus of shCB1 was fused with the N‐terminus of a G‐protein alpha subunit, Gαi. The shCB1/Gαi chimera shows agonist stimulated GTPγS binding, and thus provides a simplified way to measure agonist induced CB1 activation. Taken together, the shCB1 and shCB1/Gαi gene constructs provide useful tools for biochemical and biophysical examinations of CB1 structure, activation and attenuation.
Synthesis and evaluation of potential affinity labels derived from endomorphin‐2
Authors: Choi H. , Murray T.F. , Aldrich J.V.
Published: March 2003

Abstract: In an attempt to identify potential peptide‐based affinity labels for opioid receptors, endomorphin‐2 (Tyr‐Pro‐Phe‐PheNH2), a potent and selective endogenous ligand for µ‐opioid receptors, was chosen as the parent peptide for modification. The tetrapeptide analogs were prepared using standard Fmoc‐solid phase peptide synthesis in conjunction with incorporation of Fmoc‐Phe(p‐NHAlloc) and modification of the p‐amino group. The electrophilic groups isothiocyanate and bromoacetamide were introduced into the para position on either Phe3 or Phe4; the corresponding free amine‐containing peptides were also prepared for comparison. The peptides bearing an affinity label group and their free amine analogs were evaluated in a radioligand‐binding assay using Chinese hamster ovary (CHO) cells expressing µ‐ and δ‐opioid receptors. Modification on Phe4 was better tolerated than on Phe3 for µ‐receptor binding. Among the analogs tested, [Phe(p‐NH2)4]endomorphin‐2 showed the highest affinity (IC50 = 37 nm) for µ‐receptors. The Phe(p‐NHCOCH2Br)4 analog displayed the highest µ‐receptor affinity (IC50 = 158 nm) among the peptides containing an affinity label group. Most of the compounds exhibited negligible binding affinity for δ‐receptors, similar to the parent peptide.
Binding of the periodontal pathogen Actinobacillus actinomycetemcomitans to extracellular matrix proteins
Authors: Mintz K. P. , Fives‐Taylor P. M.
Published: March 2003

The interaction of Actinobacillus actinomycetemcomitans, an important pathogen implicated in juvenile and adult periodontitis, with collagenous and noncollagenous proteins of the extracellular matrix was investigated. A. actinomycetemcomitans SUNY 465 bound to immobilized type I, II, III and V but not type IV collagen. Binding to immobilized collagen was saturable and concentration dependent. This interaction could not be inhibited by soluble collagen, suggesting that binding was dependent on a specific collagen conformation. Bacteria grown anaerobically exhibited decreased collagen‐binding activity as compared with organisms grown aerobically. Bacterial outer membrane proteins were essential for binding to collagen. A. actinomycetemcomitans SUNY 465 also bound to immobilized fibronectin. In contrast, bacteria did not bind to fibrinogen, bone sialoprotein, α2‐HS glycoprotein or albumin. The mechanism of the interaction with fibronectin was more complex, possibly involving both protein and nonproteinaceous components. The majority of other A. actinomycetemcomitans strains tested bound to extracellular matrix proteins in a manner similar to SUNY 465 but with minor variation. These results demonstrate that A. actinomycetemcomitans binds to proteins found in connective tissue. The interaction with extracellular matrix proteins may contribute to the virulence of this pathogen at oral and extraoral sites of infection.
Molecular approaches to the differentiation of Actinomyces species
Authors: Jauh‐Hsun C. , Vinh T. , Davies J. K. , Figdor D.
Published: March 2003

The definition of the genus Actinomyces relies heavily on traditional methods of taxonomy. This study sought to develop molecular tools for the identification of strains of Actinomyces israelii and Actinomyces gerencseriae. Oligonucleotide probes were designed and one of these successfully differentiated A. gerencseriae from ten strains of A. israelii and three other Actinomyces species by DNA:DNA hybridization. However, probes based on known 16S rRNA sequences failed to hybridize to all the strains previously identified as A. israelii. Using the PCR technique, a region encoding a portion of the 16S rRNA was amplified from genomic DNA. The results showed that A. israelii can be divided into three different groups based on comparison of the amplified DNA sequences. This information should allow the development of probes that are specific for these newly identified groups of strains within the species A. israelii.