Differential trafficking of TLR1 I602S underlies host protection against pathogenic mycobacteria.

We recently identified I602S as a frequent single-nucleotide polymorphism of human TLR1 that greatly inhibits cell surface trafficking, confers hyporesponsiveness to TLR1 agonists, and protects against the mycobacterial diseases leprosy and tuberculosis. Because mycobacteria are known to manipulate the TLR system to their advantage, we hypothesize that the hyporesponsive 602S variant may confer protection by enabling the host to overcome this immune subversion. We report that primary human monocytes and macrophages from homozygous TLR1 602S individuals are resistant to mycobacterial-induced downregulation of macrophage MHC class II, CD64, and IFN-γ responses compared with individuals who harbor the TLR1 602I variant. Additionally, when challenged with mycobacterial agonists, macrophages from TLR1 602S/S individuals resist induction of host arginase-1, an enzyme that depletes cellular arginine stores required for the production of antimicrobial reactive nitrogen intermediates. The differences in cell activation mediated by TLR1 602S and TLR1 602I are observed upon stimulation with soluble mycobacterial-derived agonists but not with whole mycobacterial cells. Taken together, these results suggest that the TLR1 602S variant protects against mycobacterial disease by preventing soluble mycobacterial products, perhaps released from granulomas, from disarming myeloid cells prior to their encounter with whole mycobacteria.

The recognition of gammadelta TCR to protein antigen does not depend on the hydrophobic I97 residue of CDR3delta.

The crystal structure analysis demonstrated that the hydrophobic amino acid residue (isolecuine/leucine/valine) at conserved position 97 of Vdelta2 TCR plays an important role in recognizing the non-peptide antigen. But its importance to protein antigen remains unclear until now. In the present study, we focus on the role of hydrophobic amino acid residue at conserved position 97 of Vdelta2 TCR in complementarity determining region (CDR)3delta-mediated binding to protein antigen. We employed CDR3delta peptide and membrane-engineered gammadelta TCR as detecting molecules with mutated 97 hydrophobic amino acid residue in CDR3delta (nominated as OT10), a Vdelta2 CDR3 sequence derived from tumor infiltrating lymphocytes in ovarian epithelial carcinoma (OEC). Binding assays revealed that OT10 peptide and membrane-engineered gammadelta TCR (gammadelta TCR transfected cells with OT10 sequence) could bind specifically ovarian tumor cell line (SKOV3). The mutant analysis indicated that any amino acid substitution at position deltaI97 could abolish the response of the transfected cells to iso-butylamine, a known non-peptide antigen of gammadelta T cells. But amino acid substitution of isoleucine at position delta97 did not change the responsiveness of gammadelta TCR transfected cell to protein antigen. Our data suggested that a mechanism other than non-peptide antigen might mediate the recognition of Vdelta2gammadelta T cells for protein antigen. This finding may provide a possibility that gammadelta TCR recognize different ligands in diversity manners.

A single amino acid determines the immunostimulatory activity of interleukin 10.

Cellular interleukin 10s (cIL-10s) of human and murine origin have extensive sequence and structural homology to the Epstein-Barr virus BCRF-I gene product, known as viral IL-10 (vIL-10). Although these cytokines share many immunosuppressive properties, vIL-10 lacks several of the immunostimulatory activities of cIL-10 on certain cell types. The molecular and cellular bases for this dichotomy are not currently defined. Here, we show that the single amino acid isoleucine at position 87 of cIL-10 is required for its immunostimulatory function. Substitution of isoleucine in cIL-10 with alanine, which corresponds to the vIL-10 residue, abrogates immunostimulatory activity for thymocytes, mast cells, and alloantigenic responses while preserving immunosuppressive activity for inhibition of interferon gamma production and prolongation of cardiac allograft survival. Conversely, substitution of alanine with isoleucine in vIL-10 converts it to a cIL-10-like molecule with immunostimulatory activity. This single conservative residue alteration significantly affects ligand affinity for receptor; however, affinity changes do not necessarily alter specific activities for biologic responses in a predictable fashion. These results suggest complex regulation of IL-10 receptor-ligand interactions and subsequent biological responses. These results demonstrate that vIL-10 may represent a captured and selectively mutated cIL-10 gene that benefits viral pathogenesis by leading to ineffective host immune responses. The ability to manipulate the activity of IL-10 in either a stimulatory or suppressive direction may be of practical value for regulating immune responses for disease therapy, and of theoretical value for determining what aspects of IL-10 activity are important for normal T cell responses.

Epitope Mapping of Monoclonal Antibody PMab-48 Against Dog Podoplanin.

Podoplanin (PDPN), a type I transmembrane sialoglycoprotein, is expressed on normal renal podocytes, pulmonary type I alveolar cells, and lymphatic endothelial cells. Increased expression of PDPN in cancers is associated with poor prognosis and hematogenous metastasis through interactions with C-type lectin-like receptor 2 (CLEC-2) on platelets. We previously reported a novel PMab-48 antibody, which is an anti-dog PDPN (dPDPN) monoclonal antibody (mAb) recognizing PDPN expressed in lymphatic endothelial cells. However, the binding epitope of PMab-48 is yet to be clarified. In this study, an enzyme-linked immunosorbent assay and flow cytometry were used to investigate epitopes of PMab-48. The results revealed that the critical epitope of PMab-48 comprises Asp29, Asp30, Ile31, Ile32, and Pro33 of dPDPN.

Isoleucine 61 is important for the hemolytic activity of pyolysin of Trueperella pyogenes.

Pyolysin (PLO) is a hemolysin secreted by Trueperella pyogenes (T. pyogenes) and is important for the pathogenicity of T. pyogenes. Oligomerization of PLO monomers is a critical step in the process of hemolysis. However, the mechanisms of intermolecular interaction of PLO monomers are still not clearly illuminated. In this study, two monoclonal antibodies (mAbs) against PLO, named AP-1A3 and AP-4F12, respectively, were generated firstly, of which AP-1A3 showed no or undetectable hemolysis inhibition activity against recombinant PLO (rPLO), whereas AP-4F12 could markedly inhibit the hemolytic activity of rPLO. Epitope mapping revealed that AP-1A3 recognized amino acid residues ranging from 64 to 79 of mature PLO (91-106 including the signal peptide), whereas AP-4F12 recognized amino acid residues ranging from 58 to 75 (85-102 including the signal peptide). Comparison of the amino acid sequence of two epitopes revealed that six amino acid residues ranging from 58 to 63 of PLO were associated with the hemolytic activity of PLO. Alanine scan showed that substitution of each amino acid ranging from 58 to 62 with alanine had apparent impact on the hemolytic activity of rPLO, especially for the substitution of isoleucine 61 which caused almost complete loss of hemolytic activity of rPLO. Our findings identified a region in PLO and an amino acid in that region might play important role in the process of oligomerization of PLO monomers.

Effects of dietary L-isoleucine on laying performance and immunomodulation of laying hens.

Isoleucine may be a limiting amino acid for laying hens fed diets with a lowered protein level. An experiment was conducted to examine laying performance and the immune function of laying hens provided diets varying in digestible isoleucine levels during the peak production period. A total number of 400 Lohmann Brown laying hens, 28 wk of age, were allocated to 5 dietary treatment groups, each of which included 5 replicates of 16 hens per replicate (4 cages / replicate; 80 hens / treatment). L-isoleucine was added to the experimental diet (14% CP) containing synthetic amino (methionine, lysine, threonine, tryptophan, and valine) by zero, 1.0, 2.0, 3.0, and 4.0 g/kg, corresponding to 0.54%, 0.64%, 0.74%, 0.84, and 0.94% digestible isoleucine, respectively. At the end of the experiment (wk 40), dietary isoleucine did not affect laying performance or egg quality. Serum albumin concentration increased quadratically (P < 0.05) in response to digestible dietary isoleucine at 0.74%. Serum free isoleucine and lysine increased (P < 0.05) in response to digestible dietary isoleucine at 0.74%. Digestible dietary isoleucine levels did not affect the serum concentrations of total antioxidative capability (T-AOC), total superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), and CuZn-superoxide dismutase (CuZn-SOD). There was no significant (P > 0.05) response of excess digestible isoleucine level on the serum level of IgG, IgA, or IgM. In addition, dietary isoleucine levels did not affect the concentrations of secretory immunoglobulin A (sIgA), tumor necrosis factor alpha (TNFα), or interleukin (IL-2 and IL-6) in the ileum. Also, expressions of ileal MUC2 mRNA, sIgA mRNA, and IL-1ß mRNA were not changed (P > 0.05) by excess digestible isoleucine level. Furthermore, excess digestible isoleucine level did not change mRNA expression of ileal tight junction protein (claudin-1 and occludin). No effect occurred when isoleucine was supplemented, suggesting that it is not a limiting amino acid in the low crude protein diet on laying performance and intestinal mucosal immune.

Autoantibody binding to steroid 21-hydroxylase--effect of five mutations.

Steroid 21-hydroxylase (21-OH) is a key haem containing steroidogenic enzyme and a major adrenal specific autoantigen. Cys 428 in 21-OH is thought to have an important role in haem binding and we now describe the effects of mutations at Cys 428 (to Ser, Arg and Phe) on 21-OH autoantibody binding. Expression of wild type and mutated 21-OH was carried out using an in vitro transcription/translation (TnT) system and reactivity of 21-OH autoantibodies with mutated 21-OH analysed by western blotting (in the case of unlabelled proteins) or immunoprecipitation assay (IPA) (in the case of 35S-labelled proteins). All 3 substitutions at Cys 428 had similar effects on 21-OH autoantibody binding and each one caused a reduction in autoantibody binding to about 50% of wild type in the case of IPA and to about 70% of wild type in the case of western blotting analysis. In addition to mutations at Cys 428, we studied 2 naturally occurring mutations at Pro 30 to Leu and Ile 172 to Asn which are associated with diminished 21-OH enzyme activity. The Pro 30 mutation had no effect, but the Ile 172 mutation caused a reduction in 21-OH autoantibody binding in the IPA to about 80% of wild type. Overall, our studies emphasise the close relationship between the 21-OH aminoacid sequences important for 21-OH enzyme activity and 21-OH autoantibody binding.

Isoleucine needs of thirty- to forty-day-old female chickens: immunity.

Broilers fed diets with reduced amino acid levels may be limiting in isoleucine. Because research addressing daily Ile needs for broiler immunity is sparse, Ile responses for immunity in female broilers were evaluated in 2 experiments in broilers from 30 to 42 d of age. Cellular and humoral immunity were evaluated in diets limiting in Ile and diets varying in Ile from deficient to adequate. Pen was the experimental unit in both experiments. Treatments in experiment 1 consisted of 2 levels of Ile (0.42 vs. 0.72% total of diet) and 3 strains of broilers, Arbor Acres+, Ross 508, Ross 708 (6 treatments; 5 pens each). In experiment 1, measurements consisted of: a cutaneous basophil hypersensitivity test to phytohemagglutinin-P (PHA-P) on d 37 and 38; cell quantification of CD4+, CD8+, and BU-1+ lymphocytes at d 41 and 42; and relative immune organ weights at 42 d. No Ile x strain interaction occurred. Feeding an Ile-deficient diet to broilers suppressed the cell mediated response to PHA-P, and reduced thymus weight and the percentage of CD8+ T cells. There were no significant differences between strains. In experiment 2, gradations of Ile (0.42, 0.50, 0.58, 0.66, 0.74, and 0.82% total of diet) were fed to one strain (Ross 508) of female broilers (7 pens per diet). A control diet containing 0.70% Ile (6 pens) was compared with an Ile surfeit concentration. Measurements in experiment 2 consisted of a hypersensitivity test to PHA-P on d 35 and 36; a primary antibody response to SRBC from 35 to 42 d; cell quantification of CD8+ alpha, beta, and T cell receptor (TCR)-1 (delta/gamma) lymphocytes on d 41 and 42; and immune organ weights at 42 d. Immunity measurements in birds fed surfeit Ile in the titration diets were equal to birds fed the control diet. A linear response to increasing Ile was obtained for relative bursa, but no Ile quadratic responses were noted for other measurements in experiment 2. Although feeding broilers a diet deficient in Ile suppressed some immune criteria, it does not appear that a marginal Ile deficiency will compromise immunity in growing female broilers.

Residue 67 in the DRbeta1*0101 and DRbeta1*0103 chains strongly influences antigen presentation and DR-peptide molecular complex conformation.

Two closely-related molecules, DR(alpha,beta1*0101) and DR(alpha,beta1*0103), whose beta chains only differ by three amino acids at positions 67, 70, and 71, and six intermediate molecules obtained by site-directed mutagenesis were used to ascertain the respective roles of the three polymorphic residues. Substitutions at positions 70 (D-->Q), 71 (E-->R) and 67 (I or L-->F) strongly affected HA 306-318-specific T-cell recognition. The consequences of the substitution of residue 67 by a phenylalanine depended on the modified HLA-DR molecule. Although this substitution completely inhibited peptide-specific DR1-restricted T-cell recognition, its manifestations on the DR103-restricted T-cell response were variable (abolishing proliferation of some cell lines and not others), no matter what the peptide presented was (HA 306-319 or HIV P25 peptides). We also observed that inhibition of the proliferation of an alloreactive anti-DR103 T-cell clone, caused by a substitution at position 70, was completely cancelled by substitution of residue 67 by a phenylalanine. The observations based on functional experiments, thus, suggest that residue 67 plays an important role in determining conformation of the peptide presented to the T cells. Molecular modeling was used to predict changes induced by amino acid substitutions and highly supports functional data. Substitution of residue 67 by a phenylalanine could have repercussions on the structure of HLA-DR molecule/peptide complexes and affect T-cell recognition.

Differential sensitivity to mutations in a single peptide by two TCRs having identical beta-chains and closely related alpha-chains.

The TCR on CD4 T cells binds to and recognizes MHC class II:antigenic peptide complexes through molecular contacts with the peptide amino acid residues that face up and out of the peptide-binding groove. This interaction primarily involves the complementarity-determining regions (CDR) of the TCR alpha- and ss-chains contacting up to five residues of the peptide. We have used two TCRs that recognize the same antigenic peptide and have identical Vss8.2 chains, but differ in all three CDR of their related Valpha2 chains, to examine the fine specificity of the TCR:peptide contacts that lead to activation. By generating a peptide library containing all 20 aa residues in the five potential TCR contact sites, we were able to demonstrate that the two similar TCRs responded differentially when agonist, nonagonist, and antagonist peptide functions were examined. Dual substituted peptides containing an agonist residue at the N terminus, which interacts with CDR2alpha, and an antagonist residue at the C terminus, which interacts with the CDR3ss, were used to show that the nature of the overall signal through the TCR is determined by a combination of the type of signal received through both the TCR alpha- and ss-chains.