title: Optimization of an alum-adsorbed vaccine powder formulation for epidermal powder immunization.
abstract: OBJECTIVE
  To develop stable and effective aluminum salt (alum)-adsorbed vaccine powder formulations for epidermal powder immunization (EPI) via a spray freeze-drying (SFD) process.
  
  
  METHODS
  Powder properties were determined using particle size analysis, tap density, and scanning electron microscopy. Alum coagulation was monitored via optical microscopy and particle sedimentation. Protein analysis was determined by the BCA protein assay, SDS-PAGE, and an enzyme immunoassay. In vivo immunogenicity and skin reactogenicity were performed on hairless guinea pigs and pigs, respectively.
  
  
  RESULTS
  SFD of hepatitis B surface antigen (HBsAg) adsorbed to aluminum hydroxide or aluminum phosphate using an excipient combination of trehalose/mannitol/dextran produced vaccine powders of dense particles and satisfactory powder flowability and hygroscopicity. This formulation also offered excellent long-term stability to the powder and the antigen. The two most important factors influencing alum particle coagulation are the freezing rate and the concentration of aluminum in the liquid formulation for SFD. The SFD vaccines, when delivered to hairless guinea pigs by EPI or injected intramuscularly after reconstitution, were as immunogenic as the original liquid vaccine. A further study showed that EPI with SFD alum-adsorbed diphtheria-tetanus toxoid vaccine was well tolerated, whereas needle injection of the liquid formulation caused persistent granuloma.
  
  
  CONCLUSIONS
  Stabilization of alum-adsorbed vaccine by SFD has important implications in extending vaccination to areas lacking a cold chain for transportation and storage and may also accelerate the development of new immunization technologies such as EPI.
authors.affiliation: PowderJect Vaccines, Inc., Madison, Wisconsin 53711, USA. yuh-fun.maa@alza.com
authors.forename: Yuh-Fun
authors.initials: YF
authors.lastname: Maa
authors.forename: Cassandra
authors.initials: C
authors.lastname: Shu
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Ameri
authors.forename: Cindy
authors.initials: C
authors.lastname: Zuleger
authors.forename: Jenny
authors.initials: J
authors.lastname: Che
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Osorio
authors.forename: Lendon G
authors.initials: LG
authors.lastname: Payne
authors.forename: Dexiang
authors.initials: D
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D000534:Alum Compounds / Q000493:pharmacokinetics*; D000818:Animals; D002626:Chemistry, Pharmaceutical; D004355:Drug Stability; D004817:Epidermis / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D007114:Immunization / Q000379:methods; D008297:Male; D011208:Powders / Q000493:pharmacokinetics*; D014612:Vaccines / Q000493:pharmacokinetics*
chemical_list: D000534:Alum Compounds; D011208:Powders; D014612:Vaccines; C041524:aluminum sulfate