Antigen presenting system and methods for activation of T-cells

Details Antigen presenting system and methods for activation of T-cells Antigen presenting system and methods for activation of T-cells

2002-10-08

2004-12-07

Ewoldt, G. R. (Department: 1644)

Chemistry: molecular biology and microbiology

Animal cell, per se ; composition thereof; process of...

Method of regulating cell metabolism or physiology

C435S348000, C435S325000, C435S455000, C435S383000, C530S350000

Reexamination Certificate

active

06828150

ABSTRACT:

TECHNICAL FIELD
The present invention relates to materials and methods of activating T-cells with specificity for particular antigenic peptides, the use of activated T-cells in vivo for the treatment of a variety of disease conditions, and compositions appropriate for these uses.
BACKGROUND
The efficiency with which the immune system cures or protects individuals from infectious disease has always been intriguing to scientists, as it has been believed that it might be possible to activate the immune system to combat other types of diseases. Such diseases include cancer, AIDS, hepatitis and infectious disease in immunosuppressed patients. While various procedures involving the use of antibodies have been applied in those types of diseases, few if any successful attempts using cytotoxic T-cells have been recorded. Theoretically, cytotoxic T-cells would be the preferable means of treating the types of disease noted above. However, no procedures have been available to specifically activate cytotoxic T-cells.
Cytotoxic T-cells, or CD8
+
cells (i.e., cells expressing the molecule CD8) as they are presently known, represent the main line of defense against viral infections. CD8
+
lymphocytes specifically recognize and kill cells which are infected by a virus. Thus, the cost of eliminating a viral infection is the accompanying loss of the infected cells. The T-cell receptors on the surface of CD8
+
cells cannot recognize foreign antigens directly. In contrast to antibodies, antigen must first be presented to the receptors.
The presentation of antigen to CD8
+
T-cells is accomplished by major histocompatibility complex (MHC) molecules of the Class I type. The major histocompatibility complex (MHC) refers to a large genetic locus encoding an extensive family of glycoproteins which play an important role in the immune response. The MHC genes, which are also referred to as the HLA (human leucocyte antigen) complex, are located on chromosome 6 in humans. The molecules encoded by MHC genes are present on cell surfaces and are largely responsible for recognition of tissue transplants as “non-self”. Thus, membrane-bound MHC molecules are intimately involved in recognition of antigens by T-cells.
MHC products are grouped into three major classes, referred to as I, II, and III. T-cells that serve mainly as helper cells express CD4 and primarily interact with Class II molecules, whereas CD8-expressing cells, which mostly represent cytotoxic effector cells, interact with Class I molecules.
Class I molecules are membrane glycoproteins with the ability to bind peptides derived primarily from intracellular degradation of endogenous proteins. Complexes of MHC molecules with peptides derived from viral, bacterial and other foreign proteins comprise the ligand that triggers the antigen responsiveness of T-cells. In contrast, complexes of MHC molecules with peptides derived from normal cellular products play a role in “teaching” the T-cells to tolerate self-peptides, in the thymus. Class I molecules do not present entire, intact antigens; rather, they present peptide fragments thereof, “loaded” onto their “peptide binding groove”.
For many years, immunologists have hoped to raise specific cytotoxic cells targeting viruses, retroviruses and cancer cells. While targeting against viral diseases in general may be accomplished in vivo by vaccination with live or attenuated vaccines, no similar success has been achieved with retroviruses or with cancer cells. Moreover, the vaccine approach has not had the desired efficacy in immunosuppressed patients. At least one researcher has taken the rather non-specific approach of “boosting” existing CD8
+
cells by incubating them in vitro with IL-2, a growth factor for T-cells. However, this protocol (known as LAK cell therapy) will only allow the expansion of those CD8
+
cells which are already activated. As the immune system is always active for one reason or another, most of the IL-2 stimulated cells will be irrelevant for the purpose of combatting the disease. In fact, it has not been documented that this type of therapy activates any cells with the desired specificity. Thus, the benefits of LAK cell therapy are controversial at best, and the side effects are typically so severe that many studies have been discontinued.
Several novel molecules which appear to be involved in the peptide loading process have recently been identified. It has also been noted that Class I molecules without bound peptide (i.e., “empty” molecules) can be produced under certain restrictive circumstances. These “empty” molecules are often unable to reach the cell surface, however, as Class I molecules without bound peptide are very thermolabile. Thus, the “empty” Class I molecules disassemble during their transport from the interior of the cell to the cell surface.
The presentation of Class I MHC molecules bound to peptide alone has generally ineffective in activating CD8
+
cells. In nature, the CD8
+
cells are activated by antigen-presenting cells which present not only a peptide-bound Class I MHC molecule, but also a costimulatory molecule. Such costimulatory molecules include B7 which is now recognized to be two subgroups designated as B7.1 and B7.2. It has also been found that cell adhesion molecules such as integrins assist in this process.
When the CD8
+
T-cell interacts with an antigen-presenting cell having the peptide bound by a Class I MHC and costimulatory molecule, the CD8
+
T-cell is activated to proliferate and becomes an armed effector T-cell. See, generally, Janeway and Travers,
Immunobiology
, published by Current Biology Limited, London (1994), incorporated by reference.
Accordingly, what is needed is a means to activate T-cells so that they proliferate and become cytotoxic. It would be useful if the activation could be done in vitro and the activated cytotoxic T-cells reintroduced into the patient. It would also be desirable if the activation could be done by a synthetic antigen-presenting matrix comprised of a material such as cells which not only presents the selected peptide, but also presents other costimulatory factors which increase the effectiveness of the activation.
It would also be advantageous if it was possible to select the peptide so that substantially only those CD8
+
cells cytotoxic to cells presenting that peptide would be activated.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a synthetic antigen-presenting system for presenting an MHC molecule complexed to a peptide and an assisting molecule to a T-cell to activate the T-cell.
In one embodiment, the system relates to a synthetic antigen-presenting matrix having a support and at least the extracellular portion of a Class I MHC molecule capable of binding to a selected peptide operably linked to the support. The matrix also includes an assisting molecule operably linked to the support. The assisting molecule acts on a receptor on the CD8
+
T-cell. The MHC and assisting molecules are present in sufficient numbers to activate a population of T-cell lymphocytes against the peptide when the peptide is bound to the extracellular portion of the MHC molecule.
It has been found that an antigen-presenting matrix having both an MHC molecule or a portion of a MHC molecule together with an assisting molecule, provides a synergistic reaction in activating T-cell lymphocytes against the peptide. Examples of assisting molecules are costimulatory molecules such as B7.1 and B7.2 or adhesion molecules such as ICAM-1 and LFA-3. The extracellular portion of such costimulatory molecules can also be used. Another type of costimulatory molecule is one that reacts with the CD28 molecule such as anti-CD28 antibodies or functional portions thereof, e.g. Fab portions.
It has been found that a specifically effective synergistic reaction results from an antigen-presenting matrix having MHC molecules bound with a peptide, a costimulatory molecule, and an adhesion molecule. In particular, a highly effective synergistic generation of cytotoxic T

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