Minicell compositions and methods

#The invention is drawn to compositions and methods for the production of achromosomal archeabacterial, eubacterial and anucleate eukaryotic cells that are used as, e.g., therapeutics and/or diagnostics, reagents in drug discovery and functional proteomics, research tools, and in other applications as well.

#The following description of the background of the invention is provided to aid in understanding the invention, but is not admitted to describe or constitute prior art to the invention. The contents of the articles, patents, and patent applications, and all other documents and electronically available information mentioned or cited in this application, are hereby incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. Applicants reserve the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other documents.

#Minicells are achromosomal cells that are products of aberrant cell division, and contain RNA and protein, but little or no chromosomal DNA. Clark-Curtiss and Curtiss III, Analysis of Recombinant DNA Using Escherichia coli Minicells, 101 Methods in Enzymology 347 (1983); Reeve and Mendelson, Minicells of Bacillus subtilis. A new system for transport studies in absence of macromolecular biosynthesis, 352 Biochim. Biophys. Acta 298-305 (1974). Minicells are capable of plasmid-directed synthesis of discrete polypeptides in the absence of synthesis directed by mRNA from the bacterial chromosome. Meagher et al., Protein Expression in E. coli Minicells by Recombinant Plasmids, 10 Cell 521, 523 (1977); Roozen et al., Synthesis of Ribonucleic Acid and Protein in Plasmid-Containing Minicells of Escherichia coli K-12, 107(1) J. of Bacteriology 21 (1971); and Curtiss III, Research on bacterial conjugation with minicells and minicell-producing E. coli strains, In: Microbial Drug Resistance, Editors Susumu Mitsuhashi & Hajime Hashimoto, p. 169 (Baltimore: University Park Press 1976). Early descriptions of minicells include those of Adler et al., Genetic control of cell division in bacteria, 154 Science 417 (1966), and Adler et al. (Miniature Escherichia coli cells deficient in DNA, 57 Proc. Nat. Acad. Sci (Wash.) 321 (1967)). However, discovery of the production of minicells can arguably be traced to the 1930's (Frazer and Curtiss III, Production, Properties and Utility of Bacterial Minicells, 69 Curr. Top. Microbiol. Immunol. 1-3 (1975)).

#FIG. 1 is a Western blot in which Edg-1-6×His and Edg-3-6×His proteins expressed in minicells produced from MC-T7 cells.

#FIG. 2 shows induction of MalE(L)-NTR in isolated minicells.

#Abbreviations and Definitions

#In order to maximize the amount of RNA transcription from episomal elements in minicells, a minicell-producing cell line that expresses an RNA polymerase specific for certain episomal expression elements was created. This E. coli strain, designated MC-T7, was created as follows.

#The P678-54 E. coli strain contains mutations that influence cell division and induce the production of minicells (Adler et al., Proc. Natl. Acad. Sci. 57:321-326 (1967), Allen et al., Biochem. Biophys. Res. Communi. 47:1074-1079 (1972), Hollenberg et al., Gene 1:33-47 (1976)). The P678-54 strain is resistant to Lambda phage due to a mutation in the malT gene (Gottesman, Bacteriophage Lambda: The Untold Story. J. Mol. Biol. 293:177-180, 1999; Friedman, Interactions Between Bacteriophage Lambda and its Escherichia Coli Host. Curr. Opin. Genet. Dev. 2:727-738, 1992). Thus, as an initial step, the P678-54 strain was altered so as to be sensitive to Lambda phage so that it could form lysogens of Lambda-DE3 (see below). Wildtype MalT-encoding sequences were restored via a HFR (high frequency recombination) conjugation protocol using the G43 E. coli strain (CGSC stain 4928).

#Recipient (P678-54) and donor (G43:BW6169) strains were grown overnight in 10 mL of LB media (10 g NaCl, 10 g select peptone 140, and 5 g yeast extract in one liter ddH20). The samples were centrifuged and then concentrated in about 0.2 mL of LB media. The concentrated samples were combined and incubated with slow rotation for 30 minutes at 30° C., and were then plated on LB agar plates that contained streptomycin (50 μg/mL) and tetracycline (50 μg/mL). (Ampicillin, streptomycin, tetracycline, and all other chemicals were purchased from Sigma Chemical (St. Louis, Mo.) unless otherwise indicated.) Recipient cells were resistant to streptomycin and donor cells were resistant to tetracycline; only conjugates, which contained both resistance genes, were able to grow on the LB agar plates that contained streptomycin (50 μg/mL) and tetracycline (50 μg/mL).