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United States Patent: 6,316,006 © @ Page 3 of 10 - of the spores. It was also previously reported that protective antigen (PA) could be produced in baculovirus. [Iacono- Connors, et al., Infection and Immunity, 58:366-372 (1990); Iacono-Connors, et al., Infection and Immunity, 59:1961-1965 (1991)] A major problem in production of the PA in the baculovirus disclosed therein is that the desired antigen requires a complex purification process. Even after purification by immuno-affinity chromatography, undesired cellular material continues to contaminate the desired product. DETAILED DESCRIPTION OF THE INVENTION The instant invention provides organisms which produce protective antigen (PA) lacking lethal factor and edema factor proteins which, when present as contaminants in vaccine, can cause serious side effects. The producing organisms of the invention are also, surprisingly, non-sporulating. Furthermore, the desired antigen is expressed into the supernatant. Hence, the protective antigen produced i is easily purified and, though protective, does not cause many of the troublesome side effects of prior art vaccines. The organisms of the invention lacking spore-forming function may be killed by heat shock at temperatures as low as 60.degree. C. for 60 minutes. Hence, contamination of the environment with viable spore-forming organisms is easily avoided and decontamination is easily accomplished. Genesis of .DELTA.Sterne-1(pPA102)CR4: A 6 kb Bam HI fragment harboring the PA structural gene isolated from the endogenous Sterne plasmid pX01 was ligated into plasmid pBR322 and cloned into Escherichia coli bacteria (Vodkin and Leppla, 1983). From the resultant recombinant plasmid pSE36, the 6kb fragment was then subcloned into the gram-positive vector PUB110 using the Bam HI restriction site. The resulting plasmid was transformed into B. subtilis IS53 and two stable PA producing, kanamycin resistant isolates were found (pPA101 and pPA102) (Ivins and Welkos, 1986). Subsequent analysis of the plasmids revealed that both had suffered spontaneous deletions. The pPA102 was found to have lost 4.2 kb of DNA from 363 bp 3' of the kanamycin resistance gene to approximately 164 bp 5' of the start of the PA structural gene, a result consistent with the observed inactivation of the phleomycin resistance gene of pUB110. The plasmid was then electrotransformed into .DELTA.Sterne-1, a plasmid-free strain of B. anthracis (Infection and Immunity, 52:454-458 (1986) and transformants were selected for kanamycin resistance. Transformants displaying a stable PA+, kanamycin resistant, (LF-, EF-, capsule-) phenotype were selected. This strain, -DELTA.Sterne-1(pPA102), was then subjected to Congo Red agar selection for mutants displaying an inability to bind the dye, a characteristic known to correlate with an asporogenic phenotype (Worsham, submitted). The selected isolate, now designated .DELTA.Sterne-1(pPA102)CR4 was further subcultured three times to insure that a single clone was isolated. This clone has served as the seed stock for all research and development of fermentation conditions, and purification of PA. Materials and Methods: Fermentation Conditions Media: FA medium was used for all plates and liquid cultures described here unless otherwise specified. FA medium consisted of 33 g/l tryptone (Difco), 20 g/l yeast extract (Difco), 2 g/I L-histidine, 8 g/l Na2HPO4, 7.4 g/l NaCl, 4 g/l KH2P04 adjusted to pH 7.4 with NaOH. Precultures: A working stock of .DELTA.Sterne-1(pPA102)CR4 was prepared from the seed culture by streaking cells on an FA medium plate containing 40 .mu.g/ml of kanamycin. A sweep from the confluent growth zone on plate was cultured one time in liquid FA medium supplemented with http://patit.uspto.gov/netacgi/nph-Parser?Sectl=PTO2&Sect2=HITOFF&u=/netahtml/sear... 6/28/2005