SpeS: A Novel Superantigen and Its Potential as a Vaccine Adjuvant against Strangles

Bacterial superantigens (sAgs) are powerful activators of the immune response that trigger unspecific T cell responses accompanied by the release of proinflammatory cytokines. Streptococcus equi (S. equi) and Streptococcus zooepidemicus (S. zooepidemicus) produce sAgs that play an important role in their ability to cause disease. Strangles, caused by S. equi, is one of the most common infectious diseases of horses worldwide. Here, we report the identification of a new sAg of S. zooepidemicus, SpeS, and show that mutation of the putative T cell receptor (TCR)-binding motif (YAY to IAY) abrogated TCR-binding, whilst maintaining interaction with major histocompatibility complex (MHC) class II molecules. The fusion of SpeS and SpeSY39I to six S. equi surface proteins using two different peptide linkers was conducted to determine if MHC class II-binding properties were maintained. Proliferation assays, qPCR and flow cytometry analysis showed that SpeSY39I and its fusion proteins induced less mitogenic activity and interferon gamma expression when compared to SpeS, whilst retaining Antigen-Presenting Cell (APC)-binding properties. Our data suggest that SpeSY39I-surface protein fusions could be used to direct vaccine antigens towards antigen-presenting cells in vivo with the potential to enhance antigen presentation and improve immune responses.

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Small amounts of superantigen, when presented on dendritic cells, are sufficient to initiate T cell responses.

Journal of Experimental Medicine ◽

10.1084/jem.178.2.633 ◽

1993 ◽

Vol 178 (2) ◽

pp. 633-642 ◽

Cited By ~ 91

Author(s):

N Bhardwaj ◽

J W Young ◽

A J Nisanian ◽

J Baggers ◽

R M Steinman

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Dendritic Cell ◽

Mhc Class Ii ◽

Cell Receptor ◽

Class Ii ◽

Cell Mediated Immunity ◽

Quiescent T Cells ◽

Antigen Presenting

Dendritic cells are potent antigen-presenting cells for several primary immune responses and therefore provide an opportunity for evaluating the amounts of cell-associated antigens that are required for inducing T cell-mediated immunity. Because dendritic cells express very high levels of major histocompatibility complex (MHC) class II products, it has been assumed that high levels of ligands bound to MHC products ("signal one") are needed to stimulate quiescent T cells. Here we describe quantitative aspects underlying the stimulation of human blood T cells by a bacterial superantigen, staphylococcal enterotoxin A (SEA). The advantages of superantigens for quantitative studies of signal one are that these ligands: (a) engage MHC class II and the T cell receptor but do not require processing; (b) are efficiently presented to large numbers of quiescent T cells; and (c) can be pulsed onto dendritic cells before their application to T cells. Thus one can relate amounts of dendritic cell-associated SEA to subsequent lymphocyte stimulation. Using radioiodinated SEA, we noted that dendritic cells can bind 30-200 times more superantigen than B cells and monocytes. Nevertheless, this high SEA binding does not underlie the strong potency of dendritic cells to present antigen to T cells. Dendritic cells can sensitize quiescent T cells, isolated using monoclonals to appropriate CD45R epitopes, after a pulse of SEA that occupies a maximum of 0.1% of surface MHC class II molecules. This corresponds to an average of 2,000 molecules per dendritic cell. At these low doses of bound SEA, monoclonal antibodies to CD3, CD4, and CD28 almost completely block T cell proliferation. In addition to suggesting new roles for MHC class II on dendritic cells, especially the capture and retention of ligands at low external concentrations, the data reveal that primary T cells can generate a response to exceptionally low levels of signal one as long as these are delivered on dendritic cells.

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Immortalized dendritic cell line fully competent in antigen presentation initiates primary T cell responses in vivo.

Journal of Experimental Medicine ◽

10.1084/jem.178.6.1893 ◽

1993 ◽

Vol 178 (6) ◽

pp. 1893-1901 ◽

Cited By ~ 81

Author(s):

P Paglia ◽

G Girolomoni ◽

F Robbiati ◽

F Granucci ◽

P Ricciardi-Castagnoli

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Dendritic Cell ◽

Cell Line ◽

Mhc Class Ii ◽

Class Ii ◽

Gm Csf ◽

Antigen Presenting

Dendritic cells (DC) can provide all the known costimulatory signals required for activation of unprimed T cells and are the most efficient and perhaps the critical antigen presenting cells in the induction of primary T cell-mediated immune responses. It is now shown that mouse cell lines with many of the features of DC can be generated using the MIB phi 2-N11 retroviral vector transducing a novel envAKR-mycMH2 fusion gene. The immortalized dendritic cell line (CB1) displays most of the morphologic, immunophenotypic, and functional attributes of DC, including constitutive expression of major histocompatibility complex (MHC) class II molecules, costimulatory molecules B7/BB1, heat stable antigen, intracellular adhesion molecule 1, and efficient antigen-presenting ability. Granulocyte/macrophage colony-stimulating factor (GM-CSF) proved to be effective in increasing MHC class II molecule expression and in enhancing presentation of native protein antigens. In comparison with macrophages, CB1 dendritic cells did not exhibit phagocytic and chemotactic activity in response to various stimuli and lipopolysaccharide activation was ineffective in inducing tumor necrosis factor alpha or interleukin 1 beta production. CB1 cells, pulsed with haptens in vitro and injected into naive mice were able to induce delayed-type hypersensitivity responses, further increased with pretreatment with GM-CSF, indicating that these cells may represent an immature, rather than a mature DC. The ability of CB1 to prime T cells in vivo could provide a tool to design novel immunization strategies.

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Trypanosoma cruzi Infection Modulates In Vivo Expression of Major Histocompatibility Complex Class II Molecules on Antigen-Presenting Cells and T-Cell Stimulatory Activity of Dendritic Cells in a Strain-Dependent Manner

Infection and Immunity ◽

10.1128/iai.71.3.1194-1199.2003 ◽

2003 ◽

Vol 71 (3) ◽

pp. 1194-1199 ◽

Cited By ~ 31

Author(s):

Catalina D. Alba Soto ◽

Gerardo A. Mirkin ◽

Maria E. Solana ◽

Stella M. González Cappa

Keyword(s):

Major Histocompatibility Complex ◽

T Cell ◽

Mhc Class Ii ◽

Class Ii ◽

Peritoneal Macrophages ◽

Dependent Manner ◽

Histocompatibility Complex ◽

Antigen Presenting ◽

Strain Dependent

ABSTRACT A striking feature of Chagas' disease is the diversity of clinical presentations. Such variability may be due to the heterogeneity among Trypanosoma cruzi isolates or to the host immune response. Employing two strains which differ in their virulence, we investigated the effect of in vivo infection on professional antigen-presenting cells (APC). Acute infection with the virulent RA strain downregulated the expression of major histocompatibility complex (MHC) class II on splenic dendritic cells (DC) and inhibited its induction on peritoneal macrophages and splenic B cells. It also impaired the ability of DC to prime allogeneic T cells and to form homotypic clusters, suggesting a low maturation state of these cells. In contrast, the low-virulence K98 strain maintained the expression of MHC class II on DC or stimulated it on peritoneal macrophages and B cells and preserved DC's T-cell priming capacity and homotypic clustering. DC from RA-infected mice elicited a lower activation of T. cruzi-specific T-cell proliferation than those from K98-infected mice. APC from RA-infected mice that reached the chronic phase of infection restored MHC class II levels to those found in K98-infected mice and upregulated costimulatory molecules expression, suggesting that the immunosuppression caused by this strain is only transient. Taken together, the results indicate that in vivo infection with T. cruzi modulates APC functionality and that this is accomplished in a strain-dependent manner.

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Replacement of Pre-T Cell Receptor Signaling Functions by the CD4 Coreceptor

Journal of Experimental Medicine ◽

10.1084/jem.185.1.121 ◽

1997 ◽

Vol 185 (1) ◽

pp. 121-130 ◽

Cited By ~ 25

Author(s):

Anne M. Norment ◽

Katherine A. Forbush ◽

Nhan Nguyen ◽

Marie Malissen ◽

Roger M. Perlmutter

Keyword(s):

T Cell ◽

T Cell Receptor ◽

Mhc Class Ii ◽

Cell Receptor ◽

Class Ii ◽

Experimental Manipulation ◽

Thymocyte Development ◽

Β Chain ◽

Mhc Class Ii Molecules

An important checkpoint in early thymocyte development ensures that only thymocytes with an in-frame T cell receptor for antigen β (TCR-β) gene rearrangement will continue to mature. Proper assembly of the TCR-β chain into the pre-TCR complex delivers signals through the src-family protein tyrosine kinase p56lck that stimulate thymocyte proliferation and differentiation to the CD4+CD8+ stage. However, the biochemical mechanisms governing p56lck activation remain poorly understood. In more mature thymocytes, p56lck is associated with the cytoplasmic domain of the TCR coreceptors CD4 and CD8, and cross-linking of CD4 leads to p56lck activation. To study the effect of synchronously inducing p56lck activation in immature CD4−CD8− thymocytes, we generated mice expressing a CD4 transgene in Rag2−/− thymocytes. Remarkably, without further experimental manipulation, the CD4 transgene drives maturation of Rag2−/− thymocytes in vivo. We show that this process is dependent upon the ability of the CD4 transgene to bind Lck and on the expression of MHC class II molecules. Together these results indicate that binding of MHC class II molecules to CD4 can deliver a biologically relevant, Lck-dependent activation signal to thymocytes in the absence of the TCR-α or -β chain.

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Molecular Requirements for T Cell Recognition by a Major Histocompatibility Complex Class II–restricted T Cell Receptor: The Involvement of the Fourth Hypervariable Loop of the Vα Domain

Journal of Experimental Medicine ◽

10.1084/jem.189.3.509 ◽

1999 ◽

Vol 189 (3) ◽

pp. 509-520 ◽

Cited By ~ 9

Author(s):

Jayant Thatte ◽

Ayub Qadri ◽

Caius Radu ◽

E. Sally Ward

Keyword(s):

T Cell ◽

T Cell Receptor ◽

Mhc Class Ii ◽

T Cell Activation ◽

Cell Activation ◽

Cell Receptor ◽

Cell Interaction ◽

Class Ii ◽

Wild Type ◽

Antigen Presenting

The role of two central residues (K68, E69) of the fourth hypervariable loop of the Vα domain (HV4α) in antigen recognition by an MHC class II–restricted T cell receptor (TCR) has been analyzed. The TCR recognizes the NH2-terminal peptide of myelin basic protein (Ac1-11, acetylated at NH2 terminus) associated with the class II MHC molecule I-Au. Lysine 68 (K68) and glutamic acid 69 (E69) of HV4α have been mutated both individually and simultaneously to alanine (K68A, E69A). The responsiveness of transfectants bearing wild-type and mutated TCRs to Ac1-11–I-Au complexes has been analyzed in the presence and absence of expression of the coreceptor CD4. The data demonstrate that in the absence of CD4 expression, K68 plays a central role in antigen responsiveness. In contrast, the effect of mutating E69 to alanine is less marked. CD4 coexpression can partially compensate for the loss of activity of the K68A mutant transfectants, resulting in responses that, relative to those of the wild-type transfectants, are highly sensitive to anti-CD4 antibody blockade. The observations support models of T cell activation in which both the affinity of the TCR for cognate ligand and the involvement of coreceptors determine the outcome of the T cell–antigen-presenting cell interaction.

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Faculty Opinions recommendation of T cell receptor-independent CD4 signalling: CD4-MHC class II interactions regulate intracellular calcium and cyclic AMP.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1013876.192002 ◽

2003 ◽

Author(s):

Richard Williams

Keyword(s):

T Cell ◽

Cyclic Amp ◽

Intracellular Calcium ◽

T Cell Receptor ◽

Mhc Class Ii ◽

Cell Receptor ◽

Class Ii

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Human TCR-MHC coevolution after divergence from mice includes increased nontemplate-encoded CDR3 diversity

Journal of Experimental Medicine ◽

10.1084/jem.20161784 ◽

2017 ◽

Vol 214 (11) ◽

pp. 3417-3433 ◽

Cited By ~ 8

Author(s):

Xiaojing Chen ◽

Lucia Poncette ◽

Thomas Blankenstein

Keyword(s):

T Cells ◽

T Cell ◽

Mhc Class Ii ◽

Cell Receptor ◽

Mhc Molecules ◽

Mhc Ii ◽

Cdr3 Length ◽

Tcr Repertoire ◽

Cell Diversity ◽

Antigen Presenting

For thymic selection and responses to pathogens, T cells interact through their αβ T cell receptor (TCR) with peptide–major histocompatibility complex (MHC) molecules on antigen-presenting cells. How the diverse TCRs interact with a multitude of MHC molecules is unresolved. It is also unclear how humans generate larger TCR repertoires than mice do. We compared the TCR repertoire of CD4 T cells selected from a single mouse or human MHC class II (MHC II) in mice containing the human TCR gene loci. Human MHC II yielded greater thymic output and a more diverse TCR repertoire. The complementarity determining region 3 (CDR3) length adjusted for different inherent V-segment affinities to MHC II. Humans evolved with greater nontemplate-encoded CDR3 diversity than did mice. Our data, which demonstrate human TCR–MHC coevolution after divergence from rodents, explain the greater T cell diversity in humans and suggest a mechanism for ensuring that any V–J gene combination can be selected by a single MHC II.

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CD1: From Molecules to Diseases

F1000Research ◽

10.12688/f1000research.12178.1 ◽

2017 ◽

Vol 6 ◽

pp. 1909 ◽

Cited By ~ 2

Author(s):

D. Branch Moody ◽

Sara Suliman

Keyword(s):

T Cells ◽

T Cell ◽

Ex Vivo ◽

Cell Receptor ◽

High Genetic Diversity ◽

Disease States ◽

New Research ◽

Antigen Presenting ◽

Cluster Of Differentiation

The human cluster of differentiation (CD)1 system for antigen display is comprised of four types of antigen-presenting molecules, each with a distinct functional niche: CD1a, CD1b, CD1c, and CD1d. Whereas CD1 proteins were thought solely to influence T-cell responses through display of amphipathic lipids, recent studies emphasize the role of direct contacts between the T-cell receptor and CD1 itself. Moving from molecules to diseases, new research approaches emphasize human CD1-transgenic mouse models and the study of human polyclonal T cells in vivo or ex vivo in disease states. Whereas the high genetic diversity of major histocompatibility complex (MHC)-encoded antigen-presenting molecules provides a major hurdle for designing antigens that activate T cells in all humans, the simple population genetics of the CD1 system offers the prospect of discovering or designing broadly acting immunomodulatory agents.

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