Recombinant fusion proteins and libraries from immune cell repertoires

1. A method of generating a recombinant immunoglobulin library, comprising:

mixing RNA transcripts from a single isolated cell with a first primer and a second primer, wherein each of the first primer and the second primer is attached to a bead;

isolating RNA transcripts bound to the first primer or the second primer;

generating from the isolated RNA transcripts, (i) a first polynucleotide comprising a region encoding a first variable domain from the single isolated cell, and (ii) a second polynucleotide comprising a region encoding a second variable domain from the single isolated cell;

generating a plurality of circularized polynucleotide constructs, each comprising the first polynucleotide, the second polynucleotide, and a linker polynucleotide linking the first polynucleotide and the second polynucleotide, wherein each of said plurality of circularized polynucleotide constructs comprises a cognate pair of linked first and second variable domains from said single isolated cell;

inserting a third polynucleotide comprising a sequence encoding a promoter and a sequence encoding a constant region between said first polynucleotide and said second polynucleotide in each of said plurality of circularized polynucleotide constructs, thereby generating a plurality of recombinant immunoglobulin expression constructs;

inserting said plurality of recombinant immunoglobulin expression constructs into a plurality of host cells; and

expressing said plurality of recombinant immunoglobulin expression constructs in said plurality of host cells, thereby generating the recombinant immunoglobulin library comprising a plurality of recombinant immunoglobulins, wherein each of said plurality of recombinant immunoglobulins comprises a linked heavy chain variable domain and a light chain variable domain which are a cognate pair from a single cell from a mammalian donor.

2. The method of claim 1 , wherein said insertion of said third polynucleotide is performed in parallel for said plurality of circularized polynucleotide constructs.

3. The method of claim 1 , wherein at least one recombinant immunoglobulin from said recombinant immunoglobulin library specifically binds to a Streptococcus pneumonia epitope, a Hemophilis influenza epitope, or a Klebsiella pneumonia epitope.

4. The method of claim 1 , wherein said plurality of recombinant immunoglobulin expression constructs comprise expression vectors.

5. The method of claim 1 , wherein said insertion of said third polynucleotide comprises a method selected from the group consisting of: Gibson assembly, site-specific digestion and ligation, and targeted recombination.