Prevention, treatment and diagnosis of

1. A chimeric or fusion protein for inducing an immune response to P. gingivalis , the protein comprising a first peptide joined directly or through a linker to a second peptide or polypeptide, wherein:

(A) said first peptide comprises a region of a P. gingivalis trypsin-like enzyme selected from the group consisting of the amino acid sequence that is the same as, or at least 90% homologous to, the sequence shown in any one of SEQ ID NOs: 1-34; and

(B) said second peptide or polypeptide comprises an adhesin domain of P. gingivalis , or fragment thereof, selected from the group consisting of:

(i) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of an adhesin domain of the Lys-X-proteinase of P. gingivalis shown in any one of SEQ ID NOs: 35-37 and 40-43; and

(ii) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of an adhesin domain of the Arg-X-proteinase of P. gingivalis shown in any one of SEQ ID NOs: 38-39 and 44-46;

(iii) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of a HagA adhesin domain of P. gingivalis shown in any one of SEQ ID NOs: 80-82; and

(iv) the amino acid sequence that is the same as or at least 90% homologous to the sequence shown in any one of SEQ ID NOs: 69-79 and 83 to 85.

2. The chimeric or fusion protein according to claim 1 , wherein said first peptide comprises the amino acid sequence selected from the group consisting of SEQ ID NOs: 3-34 and sequences at least 90% homologous thereto.

3. The chimeric or fusion protein according to claim 1 , wherein said second peptide or polypeptide comprises the amino acid sequence selected from the group consisting of SEQ ID NOs: 35-39 and sequences at least 90% homologous thereto.

4. The chimeric or fusion protein according to claim 1 , wherein:

(a) said first peptide comprises the amino acid sequence that is the same as or at least 90% homologous to the sequence shown in any one of SEQ ID NOs: 27-30 and said second peptide or polypeptide comprises the amino sequence that is the same as or at least 90% homologous to the sequence shown in any one of SEQ ID NOs: 36-37; or

(b) said first peptide comprises the amino acid sequence that is the same as or at least 90% homologous to the sequence shown in any one of SEQ ID NOs: 31-34 and said second peptide or polypeptide comprises a sequence that is the same as or at least 90% homologous to SEQ ID NO:39.

5. A chimeric or fusion protein according to claim 1 , wherein the C-terminal residue of said first peptide is covalently linked directly or through a linker that is either (i) up to 15 amino acids in length, or (ii) less than 5 amino acids in length, to either (a) the N-terminal residue or (b) the C-terminal residue of said second peptide or polypeptide.

6. A chimeric or fusion protein according to claim 1 , wherein the N-terminal residue of said first peptide is covalently linked directly or through a linker that is either (i) up to 15 amino acids in length, or (ii) less than 5 amino acids in length, to either (a) the N-terminal residue or (b) the C-terminal residue of said second peptide or polypeptide.

7. A composition comprising a chimeric or fusion protein according to claim 1 .

8. The composition according to claim 7 , further comprising an adjuvant.

9. A method of preventing or reducing the incidence or severity of a P. gingivalis -related condition or disease in a subject, comprising administering to the subject a chimeric or fusion protein of claim 1 .

10. A method for the diagnosis or monitoring of a P. gingivalis -related condition or disease in a subject, which comprises assaying a biological sample from said subject with the chimeric or fusion protein of claim 1 to detect anti- P. gingivalis antibodies.

11. A chimeric or fusion protein according to claim 1 wherein the second peptide or polypeptide comprises or consists of the sequence shown in one or more of SEQ ID NOs: 69 to 79 or one or more of SEQ ID NOs: 83 to 85.

12. A chimeric or fusion protein according to claim 11 wherein the first peptide comprises or consists of the sequence shown in one of more of SEQ ID NOs: 3 to 26.

13. The chimeric or fusion protein according to claim 1 , comprising:

(A) a first peptide with the sequence from a P. gingivalis trypsin-like enzyme selected from the group consisting of KAS1 (SEQ ID NO: 27), KAS2 (SEQ ID NO: 28), KAS3 (SEQ ID NO: 29), PAS1K (SEQ ID NO: 30), RAS1 (SEQ ID NO: 31), RAS2 (SEQ ID NO: 32), RAS3 (SEQ ID NO: 33), and PAS1R (SEQ ID NO: 34), and

(B) a second peptide or polypeptide comprising an adhesin domain of P. gingivalis , or fragment thereof, wherein said second polypeptide has the sequence selected from the group consisting of (i) KA1 (SEQ ID NO: 35), KA2 (SEQ ID NO: 40), KA3 (SEQ ID NO: 41), KA4 (SEQ ID NO: 42), KA5 (SEQ ID NO: 43), RA1 (SEQ ID NO: 38), RA2 (SEQ ID NO: 44), RA3 (SEQ ID NO: 45), RA4 (SEQ ID NO: 46), HA1 (SEQ ID NO: 80), HA1* (SEQ ID NO: 81), HA1** (SEQ ID NO: 82), or (ii) SEQ ID NOs.: 69-79, or (iii) SEQ ID NOs.: 83-85.

14. A chimeric or fusion protein for inducing an immune response to P. gingivalis , comprising KAS4 (SEQ ID NO: 64), KAS3 (SEQ ID NO: 29) KAS5 (SEQ ID NO: 65), and KAS6 (SEQ ID NO: 66).

15. A chimeric or fusion protein for inducing an immune response to P. gingivalis , comprising

at least two amino acid sequences that are the same as, or at least 90% homologous to the sequence from a P. gingivalis trypsin-like enzyme selected from the group consisting of KAS1 (SEQ ID NO: 27), KAS2 (SEQ ID NO: 28), KAS3 (SEQ ID NO: 29), PAS1K (SEQ ID NO: 30), RAS1 (SEQ ID NO: 31), RAS2 (SEQ ID NO: 32), RAS3 (SEQ ID NO: 33), and PAS1R (SEQ ID NO: 34); and

at least one sequence that comprises an adhesin domain of P. gingivalis , or fragment thereof, and that has the sequence selected from:

(i) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of an adhesin domain of the Lys-X-proteinase of P. gingivalis shown in any one of SEQ ID NOs: 35-37 and 40-43; and

(ii) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of an adhesin domain of the Arg-X-proteinase of P. gingivalis shown in any one of SEQ ID NOs: 38-39 and 44-46;

(iii) the amino acid sequence that is the same as, or at least 90% homologous to the sequence of a HagA adhesin domain of P. gingivalis shown in any one of SEQ ID NOs: 80-82; and

(iv) the amino acid sequence that is the same as or at least 90% homologous to the sequence shown in any one of SEQ ID NOs: 69-79 and 83 to 85.

16. The chimeric or fusion protein according to claim 4 wherein said first peptide comprises the sequence that is the same as or at least 90% homologous to the sequence shown in SEQ ID NO:28 and said second peptide or polypeptide comprises the sequence that is the same as or at least 90% homologous to the sequence shown in SEQ ID NO: 37.

17. The chimeric or fusion protein according to claim 4 wherein said first peptide comprises the sequence that is the same as or at least 90% homologous to the sequence shown in SEQ ID NO:27 and said second peptide or polypeptide comprises the sequence that is the same as or at least 90% homologous to the sequence shown in SEQ ID NO:36.