Chemistry: natural resins or derivatives; peptides or proteins; – Peptides of 3 to 100 amino acid residues – 25 or more amino acid residues in defined sequence
Reexamination Certificate
1999-04-30
2001-05-08
Fredman, Jeffrey (Department: 1655)
Chemistry: natural resins or derivatives; peptides or proteins;
Peptides of 3 to 100 amino acid residues
25 or more amino acid residues in defined sequence
C530S313000, C530S326000, C429S199000
Reexamination Certificate
active
06228987
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a peptide immunogen comprising a novel artificial T helper cell epitope (Th) covalently linked to a desired target antigenic site comprising B cell epitopes and optionally a general immune stimulator sequence. The artificial Th epitope imparts to the peptide immunogen the capability to induce strong T helper cell-mediated immune responses and the production of antibodies directed against the “target antigenic site.” The invention also provides for the advantageous replacement of carrier proteins and pathogen-derived T helper cell sites in established peptide immunogens by the novel artificial T helper cell epitopes for improved immunogenicity.
Many rules have been developed for predicting the amino acid sequences of T cell epitopes. However, because there is no central unifying theory on how or what makes a particular amino acid sequence useful as a T cell epitope, the rules are empirical and are not universally applicable. Being aware of these rules, the novel artificial T helper cell epitopes of the present invention were developed, nevertheless, by empirical research.
The peptide immunogens of the present invention are useful for evoking antibody responses in an immunized host to a desired target antigenic site, including sites taken from pathogenic organisms, and sites taken from normally immunosilent self-antigens and tumor-associated targets. Accordingly, the peptides of the invention are useful in diverse medical and veterinary applications, such as: vaccines to provide protective immunity from infectious disease; immunotherapies for treating disorders resulting from malfunctioning normal physiological processes; immunotherapies for treating cancer and as agents to intervene in normal physiological processes to produce desirable results.
For example, the novel artificial T helper cell epitopes of the present invention provide novel short peptide immunogens that elicit antibodies targeted to luteinizing hormone-releasing hormone (LHRH) and are useful for contraception, control of hormone-dependent tumors, prevention of boar taint, and immunocastration. The novel artificial Th epitopes of the present invention have been found to provoke an immune response when combined with target B cell epitopes of various microorganisms/proteins/peptides. In addition to LHRH, the artificial Th epitopes of the present invention have been found to be useful when linked to other target antigenic sites include somatostatin for growth promotion in farm animals; IgE for treatment of allergy; the CD4 receptor of T helper cells for treatment and prevention of HIV infection and immune disorders and foot-and-mouth disease virus capsid protein for prevention of foot-and-mouth disease.
BACKGROUND OF THE INVENTION
It is known that most antibody immune responses are cell-mediated, requiring cooperative interaction between antigen-presenting cells, B cells (antibody-producing cells which also function as antigen-presenting cells), and T helper (Th) cells. Consequently, the elicitation of an effective antibody response requires that the B cells recognize the target antigenic site (B cell epitope) of a subject immunogen and the T helper cells recognize a Th epitope. Generally, the T helper epitope on a subject immunogen is different from its B cell epitope(s) (Babbitt et al.,
Nature
, 1985; 317: 359-361). The B cell epitope is a site on the desired target recognized by B cells which in response produce antibodies to the desired target site. It is understood that the natural conformation of the target determines the site to which the antibody directly binds. The T helper cell recognition of proteins is, however, much more complex and less well understood. (Cornette et al., in
Methods in Enzymology
, vol 178, Academic Press, 1989, pp 611-634).
Under present theories, evocation of a Th cell response requires the T helper cell receptor to recognize not the desired target but a complex on the membrane of the antigen-presenting cell formed between a processed peptide fragment of the target protein and an associated class II major histocompatibility complex (MHC). Thus, peptide processing of the target protein and a three-way recognition is required for the T helper cell response. The three part complex is particularly difficult to define since the critical MHC class II contact residues are variably positioned within different MHC binding peptides (Th epitopes) and these peptides are of variable lengths with different amino acid sequences (Rudensky et al.,
Nature
, 1991; 353:622-627). Furthermore, the MHC class II molecules themselves are highly diverse depending on the genetic make-up of the host. The immune responsiveness to a particular Th epitope is thus in part determined by the MHC genes of the host. In fact, it has been shown that certain peptides only bind to the products of particular class II MHC alleles. Thus, it is difficult to identify promiscuous Th epitopes, i.e., those that are reactive across species and across individuals of a single species. It has been found that the reactivity of Th epitopes is different even among individuals of a population.
The multiple and varied factors for each of the component steps of T cell recognition: the appropriate peptide processing by the antigen-processing cell, the presentation of the peptide by a genetically determined class II MHC molecule, and the recognition of the MHC molecule/peptide complex by the receptor on T helper cells have made it difficult to determine the requirements for promiscuous Th epitopes that provide for broad responsiveness (Bianchi et al., EP 0427347; Sinigaglia et. al., chapter 6 in
Immunological Recognition of Peptides in Medicine and Biology
, ed., Zegers et al., CRC Press 1995, pp 79-87).
It is clear that for the induction of antibodies, the immunogen must comprise both the B cell determinant and Th cell determinants. Commonly, to increase the immunogenicity Th of a target, the Th response is provided by coupling the target to a carrier protein. The disadvantages of this technique are many. It is difficult to manufacture well-defined, safe, and effective peptide-carrier protein conjugates for the following reasons:
1. Chemical coupling are random reactions introducing heterogeneity of size and composition, e.g., conjugation with glutataraldehyde (Borras-Cuesta et al.,
Eur J Immunol
, 1987; 17: 1213-1215);
2. the carrier protein introduces a potential for undesirable immune responses such as allergic and autoimmune reactions (Bixler et al., WO 89/06974);
3. the large peptide-carrier protein elicits irrelevant immune responses predominantly misdirected to the carrier protein rather than the target site (Cease et al.,
Proc Natl Acad Sci USA
, 1987; 84: 4249-4253); and
4. the carrier protein also introduces a potential for epitopic suppression in a host which had previously been immunized with an immunogen comprising the same carrier protein. When a host is subsequently immunized with another immunogen wherein the same carrier protein is coupled to a different hapten, the resultant immune response is enhanced for the carrier protein but inhibited for the hapten (Schutze et al.,
J Immunol
, 1985; 135: 2319-2322).
To avoid these risks, it is desirable to replace the carrier proteins. T cell help may be supplied to a target antigen peptide by covalent binding to a well-characterized promiscuous Th determinant. Known promiscuous Th are derived from the potent pathogenic agents such as measles virus F protein (Greenstein et al.,
J Immunol
, 1992; 148: 3970-3977) and hepatitis B virus surface antigen (Partidos et al.,
J Gen Virol
1991; 72: 1293-1299). The present inventors have shown that many of the known promiscuous Th are effective in potentiating a poorly immunogenic peptide, such as the decapeptide hormone luteinizing hormone-releasing hormone (LHRH) (U.S. Pat. No. 5,759,551). Other chimeric peptides comprising known promiscuous Th epitopes with poorly immunogenic synthetic peptides to generate potent immunogens have been developed (Borras-Cuesta et al., 1987). Well-designed
Fredman Jeffrey
Morgan & Finnegan , LLP
United Biomedical Inc.
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