EARLY POST-TRANSFECTION ISOLATION OF CELLS (EPIC) FOR BIOLOGICS PRODUCTION
Provided herein are methods for selecting a population of cells expressing a target polypeptide. In some aspects, the disclosure provides methods for sorting and selecting populations of transfected host cells based on their early expression of a selectable polypeptide. In certain embodiments, the sorting is performed using fluorescence-activated cell sorting or magnetic-activated cell sorting based on the selectable polypeptide. Such selection methods can be further utilized to generate clonal populations of producer cells, e.g. for large-scale manufacturing of a target polypeptide of interest.
1 . A method of producing a population of producer cells expressing a target polypeptide, the method comprising the steps of:
(a) transfecting host cells with one or more vectors that encode one or more mRNAs, wherein the one or more mRNAs encode a selectable polypeptide and a target polypeptide;
(b) isolating from the transfected host cells, within 2 to 15 days of transfection, a sub-population of early-expressing transfected host cells which express the selectable polypeptide; and
(c) expanding the sub-population of transfected host cells, thereby producing a population of producer cells expressing the target polypeptide.
2 . The method of claim 1 , wherein steps (b) and (c) are each performed in drug-selection-free medium.
3 . The method of claim 1 , further comprising isolating the target polypeptide from the population of producer cells.
4 . The method of claim 1 , further comprising isolating one or more single transfected host cells from the expanded sub-population and culturing the one or more single transfected host cells to produce clonal populations of the one or more single transfected host cells.
5 . The method of claim 4 , wherein at least one of the clonal populations of the one or more single transfected host cells yields a 2- to 30-fold improvement in production of the target polypeptide compared to that of a stable pool of transfected but uncloned host cells obtained in step (c).
6 . The method of claim 1 , wherein the transfected host cells subject to selection in step (b) contains at least 80-120×10 6 cells.
7 . The method of claim 1 , wherein the isolating in step (b) is performed less than 6 days after transfection.
8 . The method of claim 7 , wherein the isolating in step (b) is performed between two and four days after transfection.
9 . (canceled)
10 . (canceled)
11 . The method of claim 1 , wherein the sub-population of transfected host cells contains 0.5-6.0×10 6 cells prior to expansion in step (c).
12 . The method of claim 1 , wherein the expanding in step (c) is for between 4-31 days.
13 . The method of claim 1 , wherein a first of the one or more vectors encodes the mRNA encoding the target polypeptide and a second of the one or more vectors encodes the mRNA encoding the selectable polypeptide.
14 . The method of claim 1 , wherein the mRNA encoding the target polypeptide and the mRNA encoding the selectable polypeptide are both encoded on one vector.
15 . The method of claim 1 , wherein the isolating in step (b) employs magnetic activated cell sorting (MACS), fluorescence activated cell sorting (FACS), or ClonePix.
16 . The method of claim 1 , wherein the selectable polypeptide is a FACS selectable polypeptide and the isolating in step (b) employs FACS.
17 . The method of claim 1 , wherein the target polypeptide and the selectable polypeptide form a fusion polypeptide.
18 . The method of claim 1 , wherein the target polypeptide and the selectable polypeptide are encoded by a single multicistronic mRNA.
19 . The method of claim 18 , wherein the multicistronic mRNA comprises a first open reading frame (ORF) that encodes the selectable polypeptide and a second ORF that encodes the target polypeptide, wherein the first ORF is 5′ to the second ORF.
20 . The method of claim 19 , wherein the first ORF has a non-AUG start codon.
21 . (canceled)
22 . The method of claim 19 , wherein the second ORF has an AUG start codon.
23 . The method of claim 19 , wherein the ORF that encodes the selectable polypeptide is devoid of any AUG sequences.
24 - 30 . (canceled)