Microbial production of mature human leukocyte interferons

Details Microbial production of mature human leukocyte interferons Microbial production of mature human leukocyte interferons

1988-01-19

2002-11-19

Martinell, James (Department: 1631)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Recombinant dna technique included in method of making a...

C435S069100, C435S252300, C435S252330, C536S023520

Reexamination Certificate

active

06482613

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the microbial production, via recombinant DNA technology, of human leukocyte interferons for use in the treatment of viral and neoplastic diseases, and to the means and end products of such production.
BACKGROUND OF THE INVENTION
The publications and other materials referred to herein to illuminate the background of the invention and, in particular cases, to provide additional detail respecting its practice are incorporated herein by reference and, for convenience, are numerically referenced in the following text and respectively grouped in the appended bibliography.
Leukocyte Interferon
Human leukocyte interferon was first discovered and prepared in the form of very crude precipitates by Isaacs and Lindenmann (3). Efforts to purify and characterize the material have been ongoing since that time, and have led to the preparation of relatively homogeneous leukocyte interferons derived from normal or leukemic (chronic myelogenous leukemia or “CML”) donors' leukocytes (4). These interferons are a family of proteins characterized by a potent ability to confer a virus-resistant state in their target cells (1,2). In addition, interferon can act to inhibit cell proliferation and modulate immune response. These properties have prompted the clinical use of leukocyte interferon as a therapeutic agent for the treatment of viral infections and malignancies.
Leukocyte interferons have been purified to essential homogeneity (7,8), and reported molecular weights range from about 17,500 to about 21,000. The specific activity of these preparations is remarkably high, 2×10
8
to 1×10
9
units/mg protein, but yields from cell culture methods have been discouragingly low. Nevertheless, advances in protein sequencing techniques have, in our hands, permitted the determination of partial amino acid sequences (4). Elucidation of the glycosylation of various leukocyte interferons is not at present complete, but it is now clear (by virtue of the work reported infra) that differences in glycosylation among family members does not alone account for the spectrum of molecular weights observed. Instead, the leukocyte interferons differ markedly in amino acid composition and sequence, and amino acid homology is, in some cases, less than 80 percent.
While isolation from donor leukocytes has provided sufficient material for partial characterization and limited clinical studies with homogeneous leukocyte interferon, it is a totally inadequate source for the amounts of interferon needed for large scale clinical trials and for broad scale prophylactic and/or therapeutic use thereafter. Indeed, presently clinical investigations employing human leukocyte-derived interferons in antitumor and antiviral testing have principally been confined to crude (<1 percent pure) preparations of the material, and long lead times for the manufacture of sufficient quantities, even at unrealistic price levels, have critically delayed investigation on an expanded front.
Recombinant DNA Technology
With the advent of recombinant DNA technology, the controlled microbial production of an enormous variety of useful polypeptides has become possible. Already in hand are bacteria modified by this technology to permit the production of such polypeptide products such as somatostatin (5), the (component) A and B chains of human insulin (9) and human growth hormone (18). More recently, recombinant DNA techniques have been used to occasion the bacterial production of proinsulin and thymosin alpha 1, an immune potentiating substance produced by the thymus.
Other workers have reported on the obtention of DNA coding for human leukocyte interferon and to resultant proteins having leukocyte interferon activity—cf. Nagata et al.,
Nature
284, 316 (1980); Mantei et al.,
Gene
10, 1 (1980). See also Taniguchi et al.,
Nature
285, 547 (1980).
The workhorse of recombinant DNA technology is the plasmid, a non-chromosomal loop of double-stranded DNA found in bacteria and other microbes, oftentimes in multiple copies per cell. Included in the information encoded in the plasmid DNA is that required to reproduce the plasmid in daughter cells (i.e., a “replicon”) and ordinarily, one or more selection characteristics such as, in the case of bacteria, resistance to antibiotics which permit clones of the host cell containing the plasmid of interest to be recognized and preferentially grown in selective media. The utility of plasmids lies in the fact that they can be specifically cleaved by one or another restriction endonuclease or “restriction enzyme”, each of which recognizes a different site on the plasmidic DNA. Thereafter heterologous genes or gene fragments may be inserted into the plasmid by endwise joining at the cleavage site or at reconstructed ends adjacent to the cleavage site. DNA recombination is performed outside the cell, but the resulting “recombinant” plasmid can be introduced into it by a process known as transformation and large quantities of the heterologous gene-containing recombinant plasmid obtained by growing the transformant. Moreover, where the gene is properly inserted with reference to portions of the plasmid which govern the transcription and translation of the encoded DNA message, the resulting expression vehicle can be used to actually produce the polypeptide sequence for which the inserted gene codes, a process referred to as expression. Expression is initiated in a region known as the promoter which is recognized by and bound by RNA polymerase. In some cases, as in the tryptophan or “trp” promoter preferred in the practice of the present invention, promoter regions are overlapped by “operator” regions to form a combined promoter-operator. Operators are DNA sequences which are recognized by so-called repressor proteins which serve to regulate the frequency of transcription initiation at a particular promoter. The polymerase travels along the DNA, transcribing the information contained in the coding strand from its 5′ to 3′ end into messenger RNA which is in turn translated into a polypeptide having the amino acid sequence for which the DNA codes. Each amino acid is encoded by a nucleotide triplet or “codon” within what may for present purposes be referred to as the “structural gene”, i.e. that part which encodes the amino acid sequence of the expressed product. After binding to the promoter, the RNA polymerase first transcribes nucleotides encoding a ribosome binding site, then a translation initiation or “start” signal (ordinarily ATG, which in the resulting messenger RNA becomes AUG), then the nucleotide codons within the structural gene itself. So-called stop codons are transcribed at the end of the structural gene whereafter the polymerase may form an additional sequence of messenger RNA which, because of the presence of the stop signal, will remain untranslated by the ribosomes. Ribosomes bind to the binding site provided on the messenger RNA, in bacteria ordinarily as the mRNA is being formed, and themselves produce the encoded polypeptide, beginning at the translation start signal and ending at the previously mentioned stop signal. The desired product is produced if the sequences encoding the ribosome binding site are positioned properly with respect to the AUG initiator codon and if all remaining codons follow the initiator codon in phase. The resulting product may be obtained by lysing the host cell and recovering the product by appropriate purification from other bacterial protein.
We perceived that application of recombinant DNA technology would be the most effective way of providing large quantities of leukocyte interferon which, despite the absence in material so produced of the glycosylation characteristic of human-derived material, could be employed clinically in the treatment of a wide range of viral and neoplastic diseases.
More particularly, we proposed and have since succeeded in producing mature human leukocyte interferon microbially, by constructing one or more genes therefor which could then be inserted in microbial expression v

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