Anthrax vaccine powder formulations for nasal mucosal delivery.
Anthrax remains a serious threat worldwide as a bioterror agent. A second-generation anthrax vaccine currently under clinical evaluation consists of a recombinant Protective Antigen (rPA) of Bacillus anthracis. We have previously demonstrated that complete protection against inhalational anthrax can be achieved in a rabbit model, by intranasal delivery of a powder rPA formulation. Here we describe the preformulation and formulation development of such powder formulations. The physical stability of rPA was studied in solution as a function of pH and temperature using circular dichroism (CD), and UV-visible absorption and fluorescence spectroscopies. Extensive aggregation of rPA was observed at physiological temperatures. An empirical phase diagram, constructed using a combination of CD and fluorescence data, suggests that rPA is most thermally stable within the pH range of 6-8. To identify potential stabilizers, a library of GRAS excipients was screened using an aggregation sensitive turbidity assay, CD, and fluorescence. Based on these stability profiles, spray freeze-dried (SFD) formulations were prepared at pH 7-8 using trehalose as stabilizer and a CpG-containing oligonucleotide adjuvant. SFD formulations displayed substantial improvement in storage stability over liquid formulations. In combination with noninvasive intranasal delivery, such powder formulations may offer an attractive approach for mass biodefense immunization.
Jiang
Ge
G
BD Technologies, 21 Davis Dr., RTP, North Carolina 27709, USA.
Joshi
Sangeeta B
SB
Peek
Laura J
LJ
Brandau
Duane T
DT
Huang
Juan
J
Ferriter
Matthew S
MS
Woodley
Wendy D
WD
Ford
Brandi M
BM
Mar
Kevin D
KD
Mikszta
John A
JA
Hwang
C Robin
CR
Ulrich
Robert
R
Harvey
Noel G
NG
Middaugh
C Russell
CR
Sullivan
Vincent J
VJ
D000281:Administration, Intranasal; D022122:Anthrax Vaccines / Q000737:chemistry*; D000942:Antigens, Bacterial / Q000276:immunology; D001408:Bacillus anthracis / Q000276:immunology; D002626:Chemistry, Pharmaceutical; D004339:Drug Compounding; D004355:Drug Stability; D005612:Freeze Drying; D011208:Powders
D022122:Anthrax Vaccines; D000942:Antigens, Bacterial; D011208:Powders