The amino acids upstream of NH(2)-terminal dileucine motif play a role in regulating the intracellular sorting of the Class III transporters GLUT8 and GLUT12

Abstract

The transport of glucose across cell membranes is mediated by a family of facilitative glucose transporters (GLUTs). The class III glucose transporters GLUT8 and GLUT12 both contain a similar [DE]XXXL[LI] dileucine sorting signal in their amino terminus. This type of dileucine motif facilitates protein trafficking to various organelles or to the plasma membrane via interactions with adaptor protein (AP) complexes. The [DE]XXXL[LI] motif in GLUT8 is thought to direct it to late endosomal/lysosomal compartments via its interactions with AP1 and AP2. Unlike GLUT8, the [DE]XXXL[LI] motif does not direct GLUT12 to a lysosomal compartment. Rather, GLUT12 resides in the Golgi network and at the plasma membrane. In a previous study, we found that exchanging the XXX (TQP) residues in GLUT8 with the corresponding residues in GLUT12 (GPN) resulted in a dramatic missorting of GLUT8 to the cell surface. We postulated that the XXX amino acids upstream of the dileucine motif in GLUT8 influence the degree of interaction between the [DE]XXXL[LI] motif and adaptor proteins. To further explore its trafficking mechanisms, we created mutant constructs to identify the role that each of the individual XXX amino acids has for regulating the intracellular sorting of GLUT8. Here we find that the XXX amino acids, specifically the position of a proline -2 from the dileucine residues, influence the affinity of APs for GLUT8 and GLUT12.     

The amino acids upstream of NH(2)-terminal dileucine motif play a role in regulating the intracellular sorting of the Class III transporters GLUT8 and GLUT12

The transport of glucose across cell membranes is mediated by a family of facilitative glucose transporters (GLUTs). The class III glucose transporters GLUT8 and GLUT12 both contain a similar [DE]XXXL[LI] dileucine sorting signal in their amino terminus. This type of dileucine motif facilitates protein trafficking to various organelles or to the plasma membrane via interactions with adaptor protein (AP) complexes. The [DE]XXXL[LI] motif in GLUT8 is thought to direct it to late endosomal/lysosomal compartments via its interactions with AP1 and AP2. Unlike GLUT8, the [DE]XXXL[LI] motif does not direct GLUT12 to a lysosomal compartment. Rather, GLUT12 resides in the Golgi network and at the plasma membrane. In a previous study, we found that exchanging the XXX (TQP) residues in GLUT8 with the corresponding residues in GLUT12 (GPN) resulted in a dramatic missorting of GLUT8 to the cell surface. We postulated that the XXX amino acids upstream of the dileucine motif in GLUT8 influence the degree of interaction between the [DE]XXXL[LI] motif and adaptor proteins. To further explore its trafficking mechanisms, we created mutant constructs to identify the role that each of the individual XXX amino acids has for regulating the intracellular sorting of GLUT8. Here we find that the XXX amino acids, specifically the position of a proline -2 from the dileucine residues, influence the affinity of APs for GLUT8 and GLUT12.     

In vitro activation of the rhesus macaque myeloid alpha-defensin precursor proRMAD-4 by neutrophil serine proteinases

Alpha-defensins are mammalian antimicrobial peptides expressed mainly by cells of myeloid lineage or small intestinal Paneth cells. The peptides are converted from inactive 8.5-kDa precursors to membrane-disruptive forms by post-translational proteolytic events. Because rhesus myeloid pro-alpha-defensin-4 (proRMAD-4((20-94))) lacks bactericidal peptide activity in vitro, we tested whether neutrophil azurophil granule serine proteinases, human neutrophil elastase (NE), cathepsin G (CG), and proteinase-3 (P3) have in vitro convertase activity. Only NE cleaved proRMAD-4((20-94)) at the native RMAD-4 N terminus to produce fully processed, bactericidal RMAD-4((62-94)). The final CG cleavage product was RMAD-4((55-94)), and P3 produced both RMAD-4((55-94)) and RMAD-4(57-94). Nevertheless, NE, CG, and P3 digests of proRMAD4 and purified RMAD-4((62-94)), RMAD-4((55-94)), and RMAD-4(57-94) peptides had equivalent in vitro bactericidal activities. Bactericidal peptide activity assays of proRMAD-4((20-94)) variants containing complete charge-neutralizing D/E to N/Q or D/E to A substitutions showed that (DE/NQ)-proRMAD-4((20-94)) and (DE/A)-proRMAD-4((20-94)) were as active as mature RMAD-4((62-94)). Therefore, proregion Asp and Glu side chains inhibit the RMAD-4 component of full-length proRMAD-4((20-94)), perhaps by a combination of charge-neutralizing and hydrogen-bonding interactions. Although native RMAD-4((62-94)) resists NE, CG, and P3 proteolysis completely, RMAD-4((62-94)) variants with disulfide pairing disruptions or lacking disulfide bonds were degraded extensively, evidence that the disulfide array protects the alpha-defensin moiety from degradation by the myeloid converting enzymes. These in vitro analyses support the conclusion that rhesus macaque myeloid pro-alpha-defensins are converted to active forms by serine proteinases that co-localize in azurophil granules.     

Cloning, expression, and purification of recombinant bovine rotavirus hemagglutinin, VP8*, in Escherichia coli

Rotavirus VP8* subunit is the minor trypsin cleavage product of the spike protein VP4, which is the major determinant of the viral infectivity and neutralization. To study the structure-function relationship of this fragment and to obtain type-specific reagents, substantial amounts of this protein are needed. Thus, full-length VP8* cDNA, including the entire trypsin cleavage-encoding region in gene 4, was synthesized and amplified by RT-PCR from total RNA purified from bovine rotavirus strain C486 propagated in MA104 cell culture. The extended VP8* cDNA (VP8ext) was cloned into the pGEM-T Easy plasmid and subcloned into the Escherichia coli expression plasmid pET28a(+). The correspondent 30 kDa protein was overexpressed in E. coli BL21(DE3)pLysS cells under the control of the T7 promoter. The identity and the antigenicity of VP8ext were confirmed on Western blots using anti-His and anti-rotavirus antibodies. Immobilized Ni-ion affinity chromatography was used to purify the expressed protein resulting in a yield of 4 mg of VP8ext per liter of induced E. coli culture. Our results indicate that VP8ext maintained its native antigenicity and specificity, providing a good source of antigen for the production of P type-specific immune reagents. Detailed structural analysis of pure recombinant VP8 subunit should allow a better understanding of its role in cell attachment and rotavirus tropism. Application of similar procedure to distinct rotavirus P serotypes should provide valuable P serotype-specific immune reagents for rotavirus diagnostics and epidemiologic surveys.     

Peptide motif for the rat MHC class II molecule RT1.Da: similarities to the multiple sclerosis-associated HLA-DRB1*1501 molecule

Experimental autoimmune encephalomyelitis induced with myelin proteins in DA and LEW.1AV1 rats is a model of multiple sclerosis (MS). It reproduces major aspects of this detrimental disease of the central nervous system. MS is associated with the HLA-DRB1*1501, DRB5*0101, and DQB1*0602 haplotype. DA and LEW.1AV1 rats share the RT1^av1 haplotype. So far, no MHC class II peptide motif of RT1.D^a molecules has been described. Sequence alignment of the chain of the rat MHC class II molecule RT1.D^a with human HLA class II molecules revealed strong similarity in the peptide-binding groove of RT1.D^a and HLA-DRB1*1501. According to the putative peptide-binding pockets of RT1.D^a, after comparison with the pockets of HLA-DRB1*1501, we predicted the peptide motif of RT1.D^a. To verify the predicted motif, naturally processed peptides were eluted by acidic treatment from immunoaffinity-purified RT1.D^a molecules of lymphoid tissue of DA rats and subsequently analyzed by ESI tandem mass spectrometry. In addition, we performed binding studies with combinatorial nonapeptide libraries to purified RT1.D^a molecules. Based on these studies we could define a peptide-binding motif for RT1.D^a characterized by aliphatic amino acid residues (L, I, V, M) and of F for the peptide pocket P1, aromatic residues (F, Y, W) for P4, basic residues (K, R) for P6, aliphatic residues (I, L, V) for P7, and aromatic residues (F, Y, W) and L for P9. Both methods revealed similar binding characteristics for peptides to RT1.D^a. This data will allow epitope predictions for analysis of peptides, relevant for experimental autoimmune diseases.     

Functional Characterization of the Purified Holo Form of Hemoglobin I from Lucina pectinata Overexpressed in Escherichia coli

The clam Lucina pectinata inhabits the sulfide-rich west coast of the island of Puerto Rico. It contains three different hemoglobins. Hemoglobin I (HbI), which is monomeric at all concentrations, carries H2S in its ferric state. Overexpression of recombinant HbI from Lucina pectinata in BL21STAR(DE3) Escherichia coli cells was performed in the presence of delta-aminolevulinic acid (delta-ALA). Purification of the protein was achieved using FPLC anion exchange and size exclusion chromatography. Functional characterization of the recombinant holo-protein was assessed by detection of the protein heme O2, CO, and H2S derivatives by UV-Vis spectroscopy, with Soret maxima at 416, 421, and 425 nm, respectively. The results indicated that the recombinant HbI binds H2S and forms a heme sulfide complex like the HbI wild-type hemoglobin. Kinetic measurements were performed to determine the H2S affinity of the recombinant HbI. The H2S dissociation and association rate constants were 0.055 x 10(-3)s(-1) and 0.068 x 10(5) M(-1)s(-1), respectively. The H2S affinity constant of the recombinant HbI (0.124 x 10(9) M(-1)) is eightfold lower than that of the native clam HbI reported earlier. This effect is attributed mostly to the first of two missense mutations [Met 61 (E4)-->Val 61 and Ile101 (FG4)-->Val 101] and additional amino acids present in our construct as demonstrated by measurements of the association rate with a new construct lacking most of the additional residues and the missense mutations. The elimination of these residues restores the similarity between the expressed and wild-type hemoglobins, as evidenced by H2S association kinetics. A pH dependence on the H2S association rate was also contributing to the overall affinity constant and was taken into account in the measurements of the functional properties of the new HbI construct.     

Similar [DE]XXXL[LI] Motifs Differentially Target GLUT8 and GLUT12 in Chinese Hamster Ovary Cells

The transport of glucose across cell membranes is mediated by facilitative glucose transporters (GLUTs). The recently identified class III GLUT12 is predominantly expressed in insulin-sensitive tissues such as heart, fat and skeletal muscle. We examined the subcellular localization of GLUT12 in Chinese hamster ovary and human embryonic kidney 293 cells stably expressing murine GLUT12. We have previously shown that another class III GLUT8 contains a [DE]XXXL[LI] motif that directs it to late endosomal/lysosomal compartments. Despite also having this highly conserved motif in its amino terminus, GLUT12 does not colocalize with GLUT8. Rather, GLUT12 resides in the Golgi network and at the plasma membrane (PM). Furthermore, GLUT8 and GLUT12 exhibit dramatic differences in trafficking from the PM. Whereas GLUT8 is internalized following its expression at the cell surface, GLUT12 remains largely associated with the PM. To further explore the trafficking mechanisms, we created mutant constructs to explore the potential role of GLUT12's NH₂-terminal dileucine motif in regulating its intracellular sorting. We show that both the GPN and the LL residues within the [DE]XXXL[LI] motif influence the cell surface expression of GLUT12 and conclude that the mechanisms governing the intracellular sorting of GLUT12 are distinct from those regulating the sorting of GLUT8.     

Monosaccharides modulate HCV E2 protein-derived peptide biological properties

A hepatitis C virus E(2) protein-derived sequence was selected for studying the effect of N-glycosylation on the peptide chain's conformational structure. The results suggested that the (534)TDVF(537) motif contained in peptide 33402 ((529)WGENDTDVFVLNNTRY(544)) had a type III beta-turn, relevant in antigen recognition of polyclonal antibodies, binding to human cells, and binding to HLA DRB1 *0401 molecules. N-Glycopeptides derived from this sequence contained monosaccharides in Asn(532). N-Glycopeptides presented differences in peptide chain structure compared to non-glycosylated peptides. Peptide 33402 specifically bound to human cells, specificity becoming lost when it was N-glycosylated. N-Glycosylation decreased antigen recognition of mouse polyclonal sera against this sequence. N-Glycopeptide binding to HLA DRB1 *0401 molecules was similar to that presented by non-glycosylated peptide, indicating that N-glycosylation did not affect binding to HLA DRB1 *0401 molecules. N-Glycosylation induced changes at structural and functional level which could be relevant for modulating human cell binding properties and antibody recognition.     

Experimental determination of proline hydroxylation and hydroxyproline arabinogalactosylation motifs in secretory proteins

Many secretory and several vacuolar proteins in higher plants contain hydroxylated proline residues. In many cases, hydroxyprolines in proteins are glycosylated with either arabinogalactan or oligoarabinose. We have previously shown that a sporamin precursor is O-glycosylated at the hydroxylated proline 36 residue with an arabinogalactan-type glycan when this protein is expressed in tobacco BY-2 cells (Matsuoka et al., 1995). Taking advantage of the fact that this is the only site of proline hydroxylation and glycosylation in sporamin, we analyzed the amino acid requirement for proline hydroxylation and arabinogalactosylation. We expressed several deletion constructs and many amino acid substitution mutants in tobacco cells and analyzed glycosylation and proline hydroxylation of the expressed sporamins. Hydroxylation of a proline residue requires the five amino acid sequence [AVSTG]-Pro-[AVSTGA]-[GAVPSTC]-[APS or acidic] (where Pro is the modification site) and glycosylation of hydroxyproline (Hyp) requires the seven amino acid sequence [not basic]-[not T]-[neither P, T, nor amide]-Hyp-[neither amide nor P]-[not amide]-[APST], although charged amino acids at the -2 position and basic amide residues at the +1 position relative to the modification site seem to inhibit the elongation of the arabinogalactan side chain. Based on the combination of these two requirements, we concluded that the sequence motif for efficient arabinogalactosylation, including the elongation of the glycan side chain, is [not basic]-[not T]-[AVSG]-Pro-[AVST]-[GAVPSTC]-[APS].     

Cationic cobalt(I) catalysts for the asymmetric cyclocarbonylation of 1,6-enynes

Cobalt(I) complexes, modified with (R)-(6,6'-dimethoxybiphenyl-2,2'-diyl)bis(diphenylphosphine) [Co((R)-MeO-Biphep)(CO)3]X (X = BF4 [1] or OTf [2]), were synthesized and characterized. The compounds have a trigonal bipyramidal structure and are fluxional. They were tested as catalyst precursors for the enantioselective cyclocarbonylation of 4,4-bis(carboethoxy)hept-5-en-1-yne 3. Enantioselectivities up to 78.5% were attained. However, activity and stereoselectivity are lower compared to catalytic systems based on Co2(CO)8 modified with the same atropisomeric ligand.     

Nucleotide interactions with membrane-bound transporter associated with antigen processing proteins

The transporter associated with antigen processing (TAP) contains two nucleotide-binding domains (NBD) in the TAP1 and TAP2 subunits. When expressed as individual subunits or domains, TAP1 and TAP2 NBD differ markedly in their nucleotide binding properties. We investigated whether the two nucleotide-binding sites of TAP1/TAP2 complexes also differed in their nucleotide binding properties. To facilitate electrophoretic separation of the subunits when in complex, we used TAP complexes in which one of the subunits was expressed as a fluorescent protein fusion construct. In binding experiments at 4 degrees C using the photo-cross-linkable nucleotide analogs 8-azido-[gamma-(32)P]ATP and 8-azido-[alpha-(32)P]ADP, TAP2 was found to have reduced affinity for nucleotides compared with TAP1, when the two proteins were separately expressed. Complex formation with TAP1 enhanced the binding affinity of the TAP2 nucleotide-binding site for both nucleotides. Binding analyses with mutant TAP complexes that are deficient in nucleotide binding at one or both sites provided evidence for the existence of two ATP-binding sites with relatively similar affinities in TAP1/TAP2 complexes. TAP1/TAP2 NBD interactions appear to contribute at least in part to enhanced nucleotide binding at the TAP2 site upon TAP1/TAP2 complex formation. Binding analyses with mutant TAP complexes also demonstrate that the extent of TAP1 labeling is dependent upon the presence of a functional TAP2 nucleotide-binding site.     

Definition of the Mamu A*01 peptide binding specificity: application to the identification of wild-type and optimized ligands from simian immunodeficiency virus regulatory proteins

Single amino acid substitution analogs of the known Mamu A*01 binding peptide gag 181-190 and libraries of naturally occurring sequences of viral or bacterial origin were used to rigorously define the peptide binding motif associated with Mamu A*01 molecules. The presence of S or T in position 2, P in position 3, and hydrophobic or aromatic residues at the C terminus is associated with optimal binding capacity. At each of these positions, additional residues are also tolerated but associated with significant decreases in binding capacity. The presence of at least two preferred and one tolerated residues at the three anchor positions is necessary for good Mamu A*01 binding; optimal ligand size is 8-9 residues. This detailed motif has been used to map potential epitopes from SIVmac239 regulatory proteins and to engineer peptides with increased binding capacity. A total of 13 wild type and 17 analog candidate epitopes were identified. Furthermore, our analysis reveals a significantly lower than expected frequency of epitopes in early regulatory proteins, suggesting a possible evolutionary- and/or immunoselection directed against variants of viral products that contain CTL epitopes.     

Structural Basis of Glycan Recognition in Globally Predominant Human P[8] Rotavirus

Rotavirus(RV)causes acute gastroenteritis in infants and children worldwide.Recent studies showed that glycans such as histo-blood group antigens(HBGAs)function as cell attachment factors affecting RV host susceptibility and prevalence.P[8]is the predominant RV genotype in humans,but the structural basis of how P[8]RVs interact with glycan ligands remains elusive.In this study,we characterized the interactions between P[8]VP8~*s and glycans which showed that VP8~*,the RV glycan binding domain,recognized both mucin core 2 and H type 1 antigens according to the ELISA-based oligosaccharide binding assays.Importantly,we determined the structural basis of P[8]RV-glycans interaction from the crystal structures of a Rotateq P[8]VP8~*in complex with core 2 and H type 1 glycans at 1.82.3 ?,respectively,revealing a common binding pocket and similar binding mode.Structural and sequence analysis demonstrated that the glycan binding site is conserved among RVs in the P[Ⅱ]genogroup,while genotype-specific amino acid variations determined different glycan binding preference.Our data elucidated the detailed structural basis of the interactions between human P[8]RVs and different host glycan factors,shedding light on RV infection,epidemiology,and development of anti-viral agents.     

Identification of calmodulin isoform-specific binding peptides from a phage-displayed random 22-mer peptide library

Plants express numerous calmodulin (CaM) isoforms that exhibit differential activation or inhibition of CaM-dependent enzymes in vitro; however, their specificities toward target enzyme/protein binding are uncertain. A random peptide library displaying a 22-mer peptide on a bacteriophage surface was constructed to screen peptides that specifically bind to plant CaM isoforms (soybean calmodulin (ScaM)-1 and SCaM-4 were used in this study) in a Ca2+-dependent manner. The deduced amino acid sequence analyses of the respective 80 phage clones that were independently isolated via affinity panning revealed that SCaM isoforms require distinct amino acid sequences for optimal binding. SCaM-1-binding peptides conform to a 1-5-10 ((FILVW)XXX(FILV) XXXX(FILVW)) motif (where X denotes any amino acid), whereas SCaM-4-binding peptide sequences conform to a 1-8-14 ((FILVW)XXXXXX(FAILVW)XXXXX(FILVW)) motif. These motifs are classified based on the positions of conserved hydrophobic residues. To examine their binding properties further, two representative peptides from each of the SCaM isoform-binding sequences were synthesized and analyzed via gel mobility shift assays, Trp fluorescent spectra analyses, and phosphodiesterase competitive inhibition experiments. The results of these studies suggest that SCaM isoforms possess different binding sequences for optimal target interaction, which therefore may provide a molecular basis for CaM isoform-specific function in plants. Furthermore, the isolated peptide sequences may serve not only as useful CaM-binding sequence references but also as potential reagents for studying CaM isoform-specific function in vivo.     

Functional expression in yeast of an N-deleted form of<Emphasis Type="Italic"> At</Emphasis>-ACA8, a plasma membrane Ca<Superscript>2+</Superscript>-ATPase of<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>, and characterization of a hyperactive mutant

A constitutively active form of At-ACA8, a plasma membrane Ca²⁺-ATPase from Arabidopsis thaliana (L.) Heynh., from which the first 74 amino acids containing the calmodulin-binding domain (74-At-ACA8) had been deleted, was expressed in Saccharomyces cerevisiae strain K616, which lacks the main endogenous active Ca²⁺ transport systems. 74-At-ACA8 complemented the K616 phenotype, making it able to grow in a calcium-depleted medium. 74-At-ACA8 protein, which co-migrated with the endoplasmic reticulum marker BiP in a sucrose-density gradient, catalyzed MgATP-dependent Ca²⁺ uptake and Ca²⁺-dependent MgATP hydrolysis, and retained the biochemical characteristics of the native plant plasma membrane Ca²⁺-ATPase (low specificity for nucleoside triphosphate, high sensitivity to inhibition by the fluorescein derivatives erythrosin B and eosin Y), thus confirming that it is correctly folded and functional. Substitution of the ⁷⁹⁴HE residues (numbers refer to full-length At-ACA8) following the highly conserved TGDG(TV)NDP(AS)L motif in the cytoplasmic headpiece with two lysine residues generated an hyperactive protein, with a catalytic activity 2-fold higher than that of 74-At-ACA8. The ⁷⁹⁴HEKK mutant was also about 6-fold more sensitive than 74-At-ACA8 to inhibition by vanadate, indicating that the mutation determines an increase in the proportion of enzyme in the E₂ state during the catalytic cycle.Abbreviations aa Amino acids - CaM Calmodulin - EB Erythrosin B - ER Endoplasmic reticulum - EY Eosin Y - FITC Fluorescein isothiocyanate - PM Plasma membrane     

Protective cellular immunity against P. falciparum malaria merozoites is associated with a different P7 and P8 residue orientation in the MHC-peptide-TCR complex

Developing a logical and rational methodology for obtaining vaccines, especially against the main parasite causing human malaria (P. falciparum), consists of blocking receptor-ligand interactions. Conserved peptides derived from proteins involved in invasion and having high red blood cell binding ability have thus been identified. Immunization studies using Aotus monkeys have revealed that these peptides were neither immunogenic nor protection inducing. When modified in their critical binding residues, previously identified by Glycine scanning, some of these peptides were immunogenic and non-protection inducers; others induced short-lived antibodies whilst a few were both immunogenic and protection inducing. However, very few of these modified high activity binding peptides (HABPs) reproducibly induced protection without inducing antibody production, but with high cytokine liberation, suggesting that cellular mechanisms had been activated in the protection process. The three-dimensional structure of these peptides inducing protection without producing antibodies was determined by 1H-NMR. Their HLA-DRbeta1* molecule binding ability was also determined to ascertain association between their 3D structure and ability to bind to Major Histocompatibility Complex Class-II molecules (MHC-II). 1H Nuclear Magnetic Resonance analysis and structure calculations clearly showed that these modified HABPs inducing protective cellular immune responses (but not producing antibodies against malaria) adopted special structural configuration to fit into the MHC II-peptide-TCR complex. A different orientation for P7 and P8 TCR contacting residues was clearly recognized when comparing their structure with modified peptides, which induced high antibody titers and protection, suggesting that these residues are involved in activating the immune system associated with antibody production and protection.     

The peptide motif of the single dominantly expressed class I molecule of the chicken MHC can explain the response to a molecular defined vaccine of infectious bursal disease virus (IBDV)

In contrast to typical mammals, the chicken MHC (the BF-BL region of the B locus) has strong genetic associations with resistance and susceptibility to infectious pathogens as well as responses to vaccines. We have shown that the chicken MHC encodes a single dominantly expressed class I molecule whose peptide-binding motifs can determine resistance to viral pathogens, such as Rous sarcoma virus and Marek’s disease virus. In this report, we examine the response to a molecular defined vaccine, fp-IBD1, which consists of a fowlpox virus vector carrying the VP2 gene of infectious bursal disease virus (IBDV) fused with β-galactosidase. We vaccinated parental lines and two backcross families with fp-IBD1, challenged with the virulent IBDV strain F52/70, and measured damage to the bursa. We found that the MHC haplotype B15 from line 15I confers no protection, whereas B2 from line 6₁ and B12 from line C determine protection, although another locus from line 6₁ was also important. Using our peptide motifs, we found that many more peptides from VP2 were predicted to bind to the dominantly expressed class I molecule BF2*1201 than BF2*1501. Moreover, most of the peptides predicted to bind BF2*1201 did in fact bind, while none bound BF2*1501. Using peptide vaccination, we identified one B12 peptide that conferred protection to challenge, as assessed by bursal damage and viremia. Thus, we show the strong genetic association of the chicken MHC to a T cell vaccine can be explained by peptide presentation by the single dominantly expressed class I molecule.     

Functional characterization of CTL against gp100 altered peptide ligands

In this study, four modified gp100 peptides were designed by combining amino acids from the melanoma peptide antigen gp100((209-217)) with preferred primary and auxiliary HLA-A *0201 anchor residues previously identified from combinatorial peptide library screening with recombinant HLA-A*0201. These modified peptides demonstrated stronger binding affinity for the HLA-A*0201 molecule compared to wild-type gp100 peptide. Nine CTL lines generated from patients immunized with the g209-2 M peptide and one CTL line from a non-immunized patient were tested for the ability to respond to these modified gp100 peptides. Stimulation of CTL by two of four modified peptides induced higher levels of IFN-gamma secretion than the wild-type gp100 peptide, demonstrating that higher peptide binding affinity for HLA molecules does not necessarily equate to functional activity of CTL. Two major and one minor CTL recognition pattern were observed, irrespective of previous peptide immunization, suggesting that multiple, rationally designed modified tumor peptides for the same epitope stimulate a broad CTL response by activating multiple CTL capable of cross-reacting with the natural antigenic peptide.