Transgenic non-human mammal for producing chimeric human immunoglobulin E antibodies

1. A transgenic mouse, whose genome comprises an endogenous immunoglobulin heavy-chain locus comprising the replacement of its mu heavy-chain switch sequence Sμ by a human transgenic DNA construct comprising respectively from its 5′ to its 3′end, at least:

(a) a first site-specific recombination sequence, a human immunoglobulin mu heavy-chain constant gene Cμ or a functional fragment thereof comprising at least human CH1, CH2, CH3 and CH4 exons and human membrane M1 and M2 exons, and a second site-specific recombination sequence, said first and said second recombination sequences being in the same orientation and capable of site-specific recombination, and

(b) a human immunoglobulin epsilon heavy-chain constant gene Cε or a functional fragment thereof comprising at least human CH1, CH2, CH3 and CH4 exons and human membrane M1 and M2 exons, and

wherein said transgenic mouse comprises endogenous B-cells which produce chimeric human immunoglobulin M (IgM) class antibodies and no endogenous IgM antibodies from said transgenic mouse, and wherein said B-cells switch chimeric human antibodies class production from immunoglobulin M to immunoglobulin E (IgE) following site-specific recombination between said first and second site-specific recombination sequences.

2. The transgenic mouse according to claim 1 , wherein said site-specific recombination sequences are loxP sites of Cre recombinase.

3. The transgenic mouse according to claim 1 , wherein said human transgenic DNA construct comprises the sequence SEQ ID NO: 6.

4. The transgenic mouse according to claim 1 , which further comprises one or more of a human immunoglobulin light chain transgene, a human or humanized high affinity IgE receptor transgene, and a transgene encoding a recombinase specific for said recombination sequences.

5. A method for producing a chimeric human IgM antibody specific for an antigen of interest, comprising at least:

a) contacting a transgenic mouse according to claim 1 with the antigen of interest to induce IgM antibody production in the B-cells of said mouse, and

(b) collecting said IgM antibody.

6. A method for producing a chimeric human IgE antibody specific for an antigen of interest, comprising at least:

a) contacting a transgenic mouse according to claim 1 with the antigen of interest to induce IgM antibody production in the B-cells of said mouse,

(b) inducing site-specific recombination between said first and second recombination sequences of the transgenic DNA construct from the B-cells of said mouse using a recombinase specific for said recombination sequences to elicit IgE production in said B-cells, and

(c) collecting said IgE antibody.

7. The method according to claim 6 , wherein said site-specific recombination is induced in vitro in B-cells harvested from said transgenic mouse and further immortalized.

8. The method of claim 7 , wherein the site-specific recombination is induced by introducing into the immortalized B-cells an expression vector encoding said recombinase, said recombinase, or an inductor of said recombinase.

9. The method according to claim 5 , wherein the antibody is collected from B-cells that have been harvested from said mouse and further immortalized.

10. A mouse embryonic stem cell comprising the human transgenic DNA construct as defined in claim 1 inserted in its endogenous immunoglobulin heavy-chain locus in place of Sε.

11. A B-cell harvested from a mouse according to claim 1 , wherein the B-cell has been immunized with an antigen of interest, wherein said B-cell produces a chimeric human IgM or IgE antibody specific for said antigen of interest, and wherein said B-cell has been immortalized.

12. The B-cell according to claim 11 , wherein the B-cell is an IgE producing B-cell further comprising a site-specific recombinase-induced deletion of its human immunoglobulin mu heavy-chain constant transgene Cε.

13. A kit for producing chimeric human IgM or IgE antibodies specific for an antigen of interest, comprising at least:

amouse according to claim 1 , or

a B-cell harvested from the mouse according to claim 1 , wherein the mouse has been immunized with an antigen of interest, wherein said B-cell produces a chimeric human IgM or IgE antibody specific for said antigen of interest, and wherein said B-cell has been immortalized.