1. A nucleic acid encoding truncated pneumococcal surface protein A1 (PspA1) comprising the nucleotide sequence of SEQ ID NO: 5 or SEQ ID NO: 6.
2. An expression construct comprising the nucleic acid as claimed in claim 1.
3. An expression construct capable of high level expression of truncated pneumococcal surface protein A1 (PspA1) as set forth in SEQ ID NO: 3 or SEQ ID NO: 4.
4. An expression construct for the high-level expression of truncated PspA1 (Pneumococcal Surface Protein A1) as set forth in SEQ ID NO: 3 or SEQ ID NO: 4, comprising:
a. gene encoding truncated pspA1 as set forth in SEQ ID NO: 5 or SEQ ID NO:
6;
b. origin of replication;
c. antibiotic resistance gene;
d. a promoter; and
e. ribosomal binding site.
5. An expression construct as claimed in claim 4, wherein the antibiotic resistance gene is kanamycin resistance gene.
6. An expression construct as claimed in claim 4, comprising:
a. ori R origin of replication;
b. kanamycin resistance gene;
c. Ptac promoter; and
d. gene of interest coding for a truncated pspA1 as set forth in SEQ ID NO: 5.
7. An expression construct as claimed in claim 4, comprising:
a. pUC origin of replication;
b. kanamycin resistance gene;
c. PT7 promoter; and
d. gene of interest coding for a truncated pspA1 as set forth in SEQ ID NO: 6.
8. An expression construct as claimed in claim 7 further comprising triose phosphate isomerase ribosomal binding site as set forth in SEQ ID NO: 7.
9. An expression construct for high level expression of truncated PspA1 (SEQ ID NO: 3), in Corynebacterium glutamicum which comprises:
a. gene encoding truncated pspA1 (SEQ ID NO: 5);
b. ori R origin of replication (SEQ ID NO: 12);

c. kanamycin resistance gene (SEQ ID NO: 1);
d. Ptac promoter (SEQ ID NO: 2); and
e. triose phosphate isomerase ribosomal binding site.
10. An expression construct for high level expression of truncated PspA1 (SEQ ID NO: 4),
in Escherichia coli which comprises:
a. gene encoding truncated pspA1 (SEQ ID NO: 6);
b. pUC origin of replication;
c. kanamycin resistance gene (SEQ ID NO: 1);
d. PT7 promoter (SEQ ID NO: 11); and
e. ribosomal binding site.
11. A recombinant host cell comprising the expression vector as claimed in any one of claims 2-10.
12. The recombinant host cell as claimed in claim 11, wherein the host is Corynebacterium glutamicum or Escherichia coli.
13. A method for high level expression of Streptococcus pneumoniae truncated PspA1 (Pneumococcal Surface Protein A1) which comprises culturing of bacteria transformed with an expression construct as claimed in any one of claims 2-10 and thereby purifying the expressed protein thereof.
14. A method of high level of expression and purification of the truncated PspA1 as claimed in claim 13, wherein the yield of truncated pspA1 is about 500 mg/L, about 400 mg/L, about 300 mg/L, about 250 mg/L, about 220 mg/L, about 200 mg/L, about 180 mg/L, about 160 mg/L, about 150 mg/L, about 120 mg/L, about 100 mg/L.
15. A pneumococcal conjugate vaccine comprising at least one polysaccharide from Streptococcus pneumoniae serotypes selected from 1, 2, 3, 4, 5, 6A, 6B, 6C, 6D, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15A, 15B, 15C, 16F, 17F, 18C, 19F, 19A, 20A, 20B, 22F, 23A, 23B, 23F, 24B, 24F, 31, 33F, 34, 35B, 35F, 38, 39 and 45, conjugated with truncated PspA1 as set forth in SEQ ID NO: 3 or SEQ ID NO: 4, or combination of truncated PspA1 and other carrier proteins selected from group comprising CRM197, tetanus toxoid, pertussis toxoid and PsaA.
16. The vaccine composition as claimed in claim 15, wherein the vaccine is a multivalent vaccine selected from 10 valent, 14 valent, 15 valent, 17 valent, 18 valent, 19 valent, 20 valent, 22 valent, 23 valent, 24 valent and 25 valent.
17. A multivalent conjugate vaccine as claimed in claim 15 comprising at least three

polysaccharides from Streptococcus pneumoniae serotypes 3, 6A and 6B conjugated to truncated PspA1 as set forth in SEQ ID NO: 3 or SEQ ID NO: 4, and Streptococcus pneumoniae serotypes 1, 4, 5, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F conjugated
to CRM197.