@article {48081, title = {Understanding unfolding and refolding of the antibody fragment (Fab) III: mapping covalent and non-covalent interactions during in-vitro refolding of light chain, heavy chain, and Fab.}, journal = {Biochemical Engineering Journal}, volume = {187}, year = {2022}, month = {NOV}, pages = {108644}, type = {Article}, abstract = {

In-vitro refolding of the antibody fragments from inclusion bodies is a critical manufacturing bottleneck. We have previously reported that Fab refolding involves the formation of an intermediate. To further decode the refolding pathway, we have mapped the covalent and non-covalent interactions during in-vitro refolding of individual light chain (LC), heavy chain (HC), and intact Fab. Intrinsic fluorescence analysis was performed to map the non -covalent interactions, whereas time-dependent disulfide mapping was performed using LC-MS/MS analysis under non-reducing and reducing atmospheres. Refolding of purified LC, HC, and intact Fab (Biosimilar rHu Ranibi-zumab) was investigated in the study. Under the reducing condition, LC, HC, and intact Fab required around 96, 30, and 70 h, respectively, whereas, under non-reducing conditions, they required only 48, 10, and 48 h, respectively, to acquire the native conformation. The disulfide bond mapping revealed that the bond between LC_Cys23/Cys88 is more unstable. The peptides mapped with the inter-chain disulfide bond were identified at 48 h during the refolding and can be considered as the rate-limiting step in (Fab) refolding. We have also studied a new refolding strategy involving assembly of separately refolded LC and HC into Fab molecule. In this case the Fab refolding yield was low (18.0 +/- 1.36\%), indicating inefficient assembly of refolded LC and HC chain into native Fab molecule.

}, keywords = {Antibody fragment, Disulfide bond formation, In-vitro refolding, Light and heavy chain, rHu Ranibizumab}, issn = {1369-703X}, doi = {10.1016/j.bej.2022.108644}, author = {Gani, Kayanat and Chirmade, Tejas and Ughade, Santosh and Thulasiram, Hirekodathakallu and Bhambure, Rahul} } @article {48728, title = {Chromatography assisted in-vitro refolding and purification of recombinant peptibody: recombinant romiplostim a case study}, journal = {International Journal of Biological Macromolecules}, volume = {249}, year = {2023}, month = {SEP }, pages = {126037}, type = {Article}, abstract = {

In-vitro protein refolding is one of the key rate-limiting unit operations in manufacturing of fusion proteins such as peptibodies expressed using E. coli. Dilution-assisted refolding is the most commonly used industrial practice to achieve the soluble, native functional form of the recombinant protein from the inclusion bodies. This study is focused on developing a chromatography-assisted in-vitro refolding platform to produce the biologically active, native form of recombinant peptibody. Recombinant Romiplostim was selected as a model protein for the study. A plug flow tubular reactor was connected in series with capture step affinity chromatography to achieve simultaneous in-vitro refolding and capture step purification of recombinant Romiplostim. Effect of various critical process parameters like fold dilution, temperature, residence time, and Cysteine: DTT ratio was studied using a central composite based design of experiment strategy to achieve a maximum refolding yield of selected peptibody. Under optimum refolding conditions, the maximum refolding yield of 57.0 \& PLUSMN; 1.5 \% and a purity of over 79.73 \& PLUSMN; 3.4 \% were achieved at 25-fold dilution, 15 degrees C temperature, 6 h residence time with 6 mM and 10 mM of cysteine and DTT, respectively. The formation of native peptibody structure was examined using various orthogonal analytical tools to study the protein{\textquoteright}s primary, secondary, and tertiary structure. The amino acid sequence for the disulfide-linked peptide was mapped using collision-induced dissociation (CID) to confirm the formation of interchain disulfide bonds between Cys7-Cys7 and Cys10-Cys10 similarly for intra-chain disulfide bonds between Cys42-Cys102, and Cys148-Cys206. The developed protocol here is a valuable tool to identify high-yield scalable refolding conditions for multi-domain proteins involving inter-domain disulfide bonds.

}, keywords = {CE-SDS, Disulfide bonds, In-vitro refolding, Peptibody, Romiplostim}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2023.126037}, author = {Rana, Sunil and Ughade, Santosh and Kumthekar, Rupali and Bhambure, Rahul} } @article {48707, title = {Mapping time dependent disulfide bond formation during in-vitro refolding of recombinant peptibody: a Fc-fusion protein}, journal = {Biochemical Engineering Journal}, volume = {197}, year = {2023}, month = {AUG}, pages = {108969}, type = {Article}, abstract = {

Disulfide bonds are commonly found in covalent interactions, which play a vital role in establishing the three-dimensional structure of proteins and maintaining their biological activity. This investigation is focused on time dependant mapping of intra and inter-disulfide bonds during in-vitro refolding of recombinant peptibody using LC-ESI-MS/MS. The selected recombinant peptibody is a homodimeric, aglycosylated Fc-fusion protein expressed in E. coli. The amino acid sequence in the disulfide bond containing peptides was confirmed at MS/MS level using the CID-based fragmentation approach. During in-vitro refolding of peptibody, a peptide with inter -chain disulfide bond is observed post 4 h, with low area intensity, and it reached a maximum in 96 h. How-ever, maximum area intensity was reached for the intra-chain disulfide bond in 72 h. Since cysteine residues responsible for intra-chain disulfide bonds are present in complex part of the Fc domain, formation of intra-chain disulfide bonds may be an overall rate-limiting step in recombinant Romiplostim refolding. Proper folding and contributions by non-covalent interactions will be required to form intra-chain disulfide bond. Monitoring time -based formation of such non-covalent interactions was carried out using intrinsic fluorescence during protein refolding. Observations from intrinsic fluorescence show that 4-6 h is most crucial time for domain formation. Observations from this study will help characterize structural integrity and quality during process and product development for consistent product quality.

}, keywords = {Disulfide bond formation, In -vitro refolding, Intrinsic fluorescence, Mass spectroscopy, Peptibody, Time based mapping}, issn = {1369-703X}, doi = {10.1016/j.bej.2023.108969}, author = {Kumthekar, Rupali and Rana, Sunil and Ughade, Santosh and Bhambure, Rahul} }