Animal models and therapeutic molecules

1. A method of obtaining an antigen specific antibody or antigen binding fragment thereof, said antibody comprising a human immunoglobulin heavy (IgH) chain, wherein said human IgH chain comprises a human IgH chain variable region and a human IgH chain constant region, and said fragment comprising a human IgH chain variable region, the method comprising:

expressing the antibody or antigen binding fragment thereof, from a first cell, wherein the cell comprises a nucleic acid encoding said human IgH chain variable region and said human IgH chain constant region of said antibody, or expressing the antigen binding fragment from a cell, wherein the cell comprises a nucleic acid encoding said human IgH chain variable region,

wherein said nucleic acid encoding said human IgH chain variable region is of a second cell which is a B cell of a transgenic mouse contacted with said antigen;

wherein the germline of said mouse has a genome with a homozygous chimeric immunoglobulin heavy chain (IgH) locus,

wherein said homozygous IgH locus comprises unrearranged human IgH V gene segments, human D gene segments and human J gene segments at an endogenous IgH locus upstream of an enhancer and a constant (C) region comprising a mouse CH gene segment,

wherein said human IgH gene segments join to mouse J/C intron DNA at a chimeric junction upstream of said enhancer,

said unrearranged human IgH V gene segments, D gene segments and J gene segments comprise all the functional human D and JH gene segments and human V gene segments Vh2-5, Vh7-41, Vh-4-4, Vhf-3, Vhf-2 and Vh6-1,

wherein said human JH gene segments comprise a human 3′JH, said 3′ JH being contiguous with human J/C intronic DNA, wherein said 3′JH is less than 2 kb upstream of said chimeric DNA junction,

wherein said mouse J/C intron DNA between said chimeric junction and said enhancer comprises a mouse 129 strain or a C57BL/6 strain DNA,

wherein bone marrow B cells of said mouse comprise more pro-B cells than pre-B cells, wherein said pro B cells express CD43 Med B220 Med and said pre B cells express CD43 low B220 high ,

wherein said transgenic mouse expresses immunoglobulin heavy chains comprising human variable regions.

2. The method of claim 1 , wherein in said mouse germline said 3′-JH gene segment comprises a human JH6 gene segment.

3. The method of claim 1 , wherein in said mouse germline DNA said human DNA downstream of said human 3′JH gene segment comprises a truncated human JC intron and said mouse JC intronic DNA comprises a truncated mouse JC intron.

4. The method of claim 1 , wherein in said mouse germline having said 129 strain DNA is 129Sv.

5. The method of claim 1 , wherein said C region comprises a mouse Cμ gene segment.

6. The method of claim 5 , wherein said mouse Cμ gene segment comprise mouse 129 strain DNA.

7. The method of claim 1 , wherein said human DNA contiguous with said human 3′JH gene segment comprises 400 base pairs of human JC intron DNA.

8. The method of claim 1 , wherein said human IgH V gene segments, D gene segments and J gene segments are operably linked to said C region to permit expression of an Ig heavy chain polypeptide comprising a human Ig heavy chain variable region and a mouse constant region.

9. The method of claim 1 , wherein said mouse is functional to produce antibody isotypes gM and IgG specific for said antigen and each isotype comprises a human heavy chain variable region.

10. The method of claim 1 , the method further comprising recovering a substance selected from the group consisting of: said antibody or antigen-binding fragment thereof; said nucleic acid encoding said human IgH chain variable region; and said cell expressing said antibody or antigen-binding fragment thereof.

11. The method of claim 1 , the method further comprising the step of providing a pharmaceutical composition comprising said antigen-specific antibody or antigen-binding fragment thereof and a pharmaceutically acceptable carrier or excipient.

12. The method of claim 1 , further comprising the step of providing said antibody or antigen-binding fragment thereof to a human subject.

13. The method of claim 1 , wherein said antigen-specific antibody or antigen binding fragment is selected from the group consisting of: a monoclonal antibody, a domain antibody, and a neutralizing antibody.

14. The method of claim 1 , wherein in said mouse germline said unrearranged human IgH VH gene segments comprise all of the human V, D and J gene segments.

15. The method of claim 1 , wherein the mouse expresses a normal relative proportion of serum IgG1, IgG2a, IgG2b and IgM antibodies.

16. The method of claim 1 , wherein said mouse produces a normal proportion or percentage of mature splenic B-cells and/or a normal proportion or percentage of bone marrow B-cell progenitor cells.

17. The method of claim 1 , wherein said germline comprises all or part of said mouse heavy chain variable region inverted with respect to said heavy chain constant region.

18. The method of claim 1 , wherein said germline comprises all or part of said mouse heavy chain variable region away from said heavy chain constant region.

19. The method of claim 1 , wherein said germline comprises all, part or none of said mouse heavy chain variable region.

20. The method of claim 1 , wherein said mouse does not express endogenous IgH heavy chain.

21. The method of claim 1 , wherein the mouse further comprises human V gene segments Vh2-26, Vhf-24, Vh3-23, Vh3-21, Vh3-20, Vh1-18, Vh3-15, Vh3-13, Vh3-11, Vh3-9, Vhf-8, and Vh3-7.

22. The method of claim 1 , wherein the mouse further comprises human V gene segments Vh3-13, Vh3-11, Vh3-9, Vhf-8, and Vh3-7, wherein said transgenic mouse expresses immunoglobulin heavy chains comprising human variable regions Vh3-13, Vh3-11, Vh3-9, Vhf-8, and Vh3-7, and wherein no more than 35% of IgH chains comprise a mouse variable region.