CLAIMS:

1.

A nucleic acid molecule comprising a nucleic acid sequence which encodes a polypeptide selected from any of: (a) SEQ ID No: 2; (b) SEQ ID No. 4; (c) SEQ ID No. 6; (d) an immunogenic fragment comprising at least 12 consecutive amino acids from a polypeptide of (a); and (e) a polypeptide of any one of (a) to (d) which has been modified to improve its immunogenicity, wherein said modified polypeptide is at least 75% identical in amino acid sequence to the corresponding polypeptide of any one of (a) to (d).

2.

A nucleic acid molecule comprising a nucleic acid sequence selected from any of: (a) SEQ ID No: 1; (b) SEQ ID No: 3; (c) SEQ ID No: 5; (d) a sequence which encodes a polypeptide encoded by any one of SEQ ID Nos: 1,3 and 5; (e) a sequence comprising at least 38 consecutive nucleotides from any one of the nucleic acid sequences of (a) to (d); and (f) a sequence which encodes a polypeptide which is at least 75% identical in amino acid sequence to the polypeptides encoded by any one of SEQ ID Nos: 1,3 and 5.

3.	A nucleic acid molecule comprising a nucleic acid sequence which is antisense to the nucleic acid molecule of claim 1.

4.	A nucleic acid molecule comprising a nucleic acid sequence which encodes a fusion protein, said fusion protein comprising a polypeptide encoded by a nucleic acid molecule according to claim 1 and an additional polypeptide.

5.	The nucleic acid molecule of claim 4 wherein the additional polypeptide is a heterologous signal peptide.

6.	The nucleic acid molecule of claim 4 wherein the additional polypeptide has adjuvant activity.

7.	A nucleic acid molecule according to any one of claims 1 to 6, operatively linked to one or more expression control sequences.

8.

A vaccine comprising at least one first nucleic acid according to any one of claims 1,2, and 4 to 7 and a vaccine vector wherein each first nucleic acid is expressed as a polypeptide, the vaccine optionally comprising a second nucleic acid encoding an additional polypeptide which enhances the immune response to the polypeptide expressed by said first nucleic acid.

9.	The vaccine of claim 8 wherein the second nucleic acid encodes an additional Chlamydia polypeptide.

10.	A pharmaceutical composition comprising a nucleic acid according to any one of claims 1 to 7 and a pharmaceutically acceptable carrier.

11.	A pharmaceutical composition comprising a vaccine according to claim 8 or 9 and a pharmaceutically acceptable carrier.

12.	A unicellular host transformed with the nucleic acid molecule of claim 7.

13.	A nucleic acid probe of 5 to 100 nucleotides which hybridizes under stringent conditions to the nucleic acid molecule of SEQ ID No: 1, or to a homolog or complementary or antisense sequence of said nucleic acid molecule.

14.	A primer of 10 to 40 nucleotides which hybridizes under stringent conditions to the nucleic acid molecules of SEQ ID No: 1, or to a homolog or complementary or antisense sequence of said nucleic acid molecule.

15.	A polypeptide encoded by a nucleic acid sequence according to any one of claims 1,2 and 4 to 7.

16.

A polypeptide comprising an amino acid sequence selected from any of: (a) SEQ ID No: 2; (b) SEQ ID No: 4; (c) SEQ ID No: 6; (d) an immunogenic fragment comprising at least 12 consecutive amino acids from a polypeptide of (a); and (e) a polypeptide of any one of (a) to (d) which has been modified to improve its immunogenicity, wherein said modified polypeptide is at least 75% identical in amino acid sequence to the corresponding polypeptide of any one of (a) to (d).

17.	A fusion polypeptide comprising a polypeptide of claim 15 or 16 and an additional polypeptide.

18.	The fusion polypeptide of claim 17 wherein the additional polypeptide is a heterologous signal peptide.

19.	The fusion protein of claim 17 wherein the additional polypeptide has adjuvant activity.

20.	A method for producing a polypeptide of claim 15 or 16, comprising the step of culturing a unicellular host according to claim 12.

21.	An antibody against the polypeptide of any one of claims 15 to 19.

22.	A vaccine comprising at least one first polypeptide according to any one of claims 15 to 19 and a pharmaceutically acceptable carrier, optionally comprising a second polypeptide which enhances the immune response to the first polypeptide.

23.	The vaccine of claim 22 wherein the second polypeptide comprises an additional Chlamydia polypeptide.

24.	A pharmaceutical composition comprising a polypeptide according to any one of claims 15 to 19 and a pharmaceutically acceptable carrier.

25.	A pharmaceutical composition comprising a vaccine according to claim 22 or 23 and a pharmaceutically acceptable carrier.

26.	A pharmaceutical composition comprising an antibody according to claim 21 and a pharmaceutically acceptable carrier.

27.

A method for preventing or treating Chlamydia infection using: (a) the nucleic acid of any one of claims 1 to 7; (b) the vaccine of any one of claims 8,9,22 and 23; (c) the pharmaceutical composition of any one of claims 10,11,24 to 26; (d) the polypeptide of any one of claims 15 to 19; or (e) the antibody of claim 21.

28.	A method of detecting Chlamydia infection comprising the step of assaying a body fluid of a mammal to be tested, with a component selected from any one of: (a) the nucleic acid of any one of claims 1 to 7; (b) the polypeptide of any one of claims 15 to 19; and (c) the antibody of claim 21.

29.	A diagnostic kit comprising instructions for use and a component selected from any one of: (a) the nucleic acid of any one of claims 1 to 7; (b) the polypeptide of any one of claims 15 to 19; and (c) the antibody of claim 21.

30.

A method for identifying a polypeptide of claims 15 to 19 which induces an immune response effective to prevent or lessen the severity of Chlamydia infection in a mammal previously immunized with polypeptide, comprising the steps of: (a) immunizing a mouse with the polypeptide; and (b) inoculating the immunized mouse with Chlamydia ; wherein the polypeptide which prevents or lessens the severity of Chlamydia infection in the immunized mouse compare to a nonimmunized control mouse is identified.

31.	An expression plasmid selected from the group consisting of pCACPNM555a, pCAI555 and pCAD76kDa.

32.	A nucleic acid molecule selected from the group consisting of SEQ ID Nos: 1,3,5 and 7.

33.	A polypeptide selected from the group consisting of SEQ ID Nos: 2,4,6 and 8.

34.	An isolated 76kDa protein from Chlamydia.

35.	An isolated 76kDa protein from Chlamydia pneumoniae.