title: Evaluating and optimizing oral formulations of live bacterial vaccines using a gastro-small intestine model.
abstract: Gastrointestinal (GI) models that mimic physiological conditions in vitro are important tools for developing and optimizing biopharmaceutical formulations. Oral administration of live attenuated bacterial vaccines (LBV) can safely and effectively promote mucosal immunity but new formulations are required that provide controlled release of optimal numbers of viable bacterial cells, which must survive gastrointestinal transit overcoming various antimicrobial barriers. Here, we use a gastro-small intestine gut model of human GI conditions to study the survival and release kinetics of two oral LBV formulations: the licensed typhoid fever vaccine Vivotif comprising enteric coated capsules; and an experimental formulation of the model vaccine Salmonella Typhimurium SL3261 dried directly onto cast enteric polymer films and laminated to form a polymer film laminate (PFL). Neither formulation released significant numbers of viable cells when tested in the complete gastro-small intestine model. The poor performance in delivering viable cells could be attributed to a combination of acid and bile toxicity plus incomplete release of cells for Vivotif capsules, and to bile toxicity alone for PFL. To achieve effective protection from intestinal bile in addition to effective acid resistance, bile adsorbent resins were incorporated into the PFL to produce a new formulation, termed BR-PFL. Efficient and complete release of 4.4×10(7) live cells per dose was achieved from BR-PFL at distal intestinal pH, with release kinetics controlled by the composition of the enteric polymer film, and no loss in viability observed in any stage of the GI model. Use of this in vitro GI model thereby allowed rational design of an oral LBV formulation to maximize viable cell release.
authors.affiliation: School of Pharmacy, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: João M S
authors.initials: JM
authors.lastname: de Barros
authors.affiliation: Food and Nutritional Sciences, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: Adele
authors.initials: A
authors.lastname: Costabile
authors.affiliation: Food and Nutritional Sciences, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Charalampopoulos
authors.affiliation: School of Pharmacy, University of Reading, Whiteknights, Reading RG6 6AD, UK.
authors.forename: Vitaliy V
authors.initials: VV
authors.lastname: Khutoryanskiy
authors.affiliation: School of Pharmacy, University of Reading, Whiteknights, Reading RG6 6AD, UK. Electronic address: a.d.edwards@reading.ac.uk.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Edwards
mesh_terms: D000284:Administration, Oral; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000737:chemistry*; D001646:Bile / Q000378:metabolism; D002214:Capsules / Q000737:chemistry; D002626:Chemistry, Pharmaceutical / Q000379:methods; D005753:Gastric Mucosa / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007421:Intestine, Small / Q000378:metabolism*; D008954:Models, Biological; D011108:Polymers / Q000737:chemistry; D014436:Typhoid-Paratyphoid Vaccines / Q000008:administration & dosage / Q000737:chemistry*; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D001428:Bacterial Vaccines; D002214:Capsules; D011108:Polymers; D014436:Typhoid-Paratyphoid Vaccines; D014613:Vaccines, Attenuated
keywords: Enteric delivery; In vitro modeling; Live bacterial vaccines; Oral administration; Polymer film