The mucosa is the primary point of entry for pathogens making it an important vaccination site to produce a protective mucosal immune response. While the sublingual (SL) mucosa presents several barriers to vaccine penetration, its unique anatomy and physiology makes it one of the best options for mucosal vaccination. Efficient and directed delivery of adjuvants and antigens to appropriate immune mediators in the SL tissue will aid in development of effective SL vaccines against infectious diseases. Herein we demonstrate a robust immune response against influenza antigens co-delivered sublingually with engineered liposomes carrying the synthetic toll like receptor-4 agonist, CRX-601. Liposome modification with PEG copolymers (Pluronics), phospholipid- PEG conjugates and chitosan were evaluated for their ability to generate an immune response in a SL murine influenza vaccine model. Phospholipid-PEG conjugates were more effective than Pluronic copolymers in generating stable, surface neutral liposomes. SL vaccination with surface modified liposomes carrying CRX-601 adjuvant generated significant improvements in flu-specific responses compared to unmodified liposomes. Furthermore, the coating of modified liposomes with methylglycol chitosan produced the most effective flu-specific immune response. These results demonstrate efficient SL vaccine delivery utilizing a combination of a mucoadhesive and surface neutral liposomes to achieve a robust mucosal and systemic immune response.
More than half of licensed therapeutic recombinant proteins (r‐proteins) are manufactured using constitutively‐expressing, stably‐transfected Chinese hamster ovary (CHO) clones. While constitutive CHO expression systems have proven their efficacy for the manufacturing of monoclonal antibodies, many next‐generation therapeutics such as cytokines and bispecific antibodies as well as biological targets such as ectodomains of transmembrane receptors remain intrinsically challenging to produce. Herein, we exploited a cumate‐inducible CHO platform allowing reduced expression of various classes of r‐proteins during selection of stable pools. Following stable pool generation, fed‐batch productions showed that pools generated without cumate (OFF‐pools) were significantly more productive than pools selected in the presence of cumate (ON‐pools) for 8 out of the 10 r‐proteins tested, including cytokines, G‐protein coupled receptors (GPCRs), the HVEM membrane receptor ectodomain, the multifunctional protein High Mobility Group protein B1 (HMGB1), as well as monoclonal and bispecific T‐cell engager antibodies. We showed that OFF‐pools contain a significantly larger proportion of cells producing high levels of r‐proteins and that these cells tend to proliferate faster when expression is turned off, suggesting that r‐protein overexpression imposes a metabolic burden on the cells. Cell viability was lower and pool recovery was delayed during selection of ON‐pools (mimicking constitutive expression), suggesting that high producers were likely lost or overgrown by faster‐growing, low‐producing cells. We also observed a correlation between the expression levels of the GPCRs with Binding immunoglobulin Protein, an endoplasmic reticulum (ER) stress marker. Taken together, these data suggest that using an inducible system to minimize r‐protein expression during stable CHO pool selection reduces cellular stresses, including ER stress and metabolic burden, leading to pools with greater frequency of high‐expressing cells, resulting in improved volumetric productivity.
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