@article {46601, title = {Understanding unfolding and refolding of the antibody fragment (Fab). I. In-vitro study}, journal = {Biochemical Engineering Journal}, volume = {164}, year = {2020}, month = {DEC}, pages = {107764}, type = {Article}, abstract = {

In-vitro protein refolding is a major rate-limiting step in the large scale production of antibody fragments expressed using a microbial source like E. coli. This investigation is focused on understanding the in-vitro unfolding and refolding of the multi-domain protein involving inter-domain disulfide linkage, like antibody fragment (Fab). Solubilization behavior of the inclusion bodies and unfolding events of Fab fragment (Biosimilar rHu Ranibizumab) were studied using nano-differential scanning fluorimetry (nano-DSF). Fab unfolding behavior was studied by fitting experimental data with the two-state and three-state thermodynamic model. Based on the Fab unfolding understanding, a two-stage design of experiment (DoE) strategy was used for the optimization of the in-vitro refolding condition of a Fab fragment. Refolding yield of 56.03 +/- 1.15 \% was achieved using the optimized oxidative refolding conditions maintained by appropriate dilution factor and redox reagent ratio. Refolding kinetics of the rHu Ranibizumab was analyzed using a three-parameter kinetic model showing rate constant k(1) :7.05e(-6) l/mg.min, k(2) :0.57 l/mg.min, and k(3) :310.19 l/mg.min. Based on observed refolding kinetics, it was concluded that the Fab refolding follows a three-state mechanism with the refolding intermediate/(s) formation from light and heavy chain of the Fab fragment as an overall rate-limiting step. The method described here is a useful tool to identify high-yield scalable refolding conditions for multi-domain proteins involving inter-domain disulfide bonds.

}, keywords = {Antibody fragment, In-vitro refolding, Refolding kinetics, rHu Ranibizumab, Two-state and Three-state models}, issn = {1369-703X}, doi = {10.1016/j.bej.2020.107764}, author = {Gani, Kayanat and Bhambure, Rahul and Deulgaonkar, Prashant and Mehta, Deepa and Kamble, Manoj} } @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} }