posted on 2024-02-22, 16:09authored byVeerabhadraiah Palakollu, Lily Motabar, Christopher J. Roberts
Protein self-interactions measured via second osmotic
virial coefficients
(B22) and dynamic light scattering interaction
parameter values (kD) are often used as
metrics for assessing the favorability of protein candidates and different
formulations during monoclonal antibody (MAb) product development.
Model predictions of B22 or kD typically do not account for glycans, though glycosylation
can potentially impact experimental MAb self-interactions. To the
best of our knowledge, the impact of MAb glycosylation on the experimentally
measured B22 and kD values has not yet been reported. B22 and kD values of two fully deglycosylated
MAbs and their native (i.e., fully glycosylated) counterparts were
measured by light scattering over a range of pH and ionic strength
conditions. Significant differences between B22 and kD of the native and deglycosylated
forms were observed at a range of low to high ionic strengths used
to modulate the effect of electrostatic contributions. Differences
were most pronounced at low ionic strength, indicating that electrostatic
interactions are a contributing factor. Though B22 and kD values were statistically
equivalent at high ionic strengths where electrostatics were fully
screened, we observed protein-dependent qualitative differences, which
indicate that steric interactions may also play a role in the observed B22 and kD differences.
A domain-level coarse-grained molecular model accounting for charge
differences was considered to potentially provide additional insight
but was not fully predictive of the behavior across all of the solution
conditions investigated. This highlights that both the level of modeling
and lack of inclusion of glycans may limit existing models in making
quantitatively accurate predictions of self-interactions.