Purification, Bacterial Expression, and Biological Activities of the Human Interferons

Abstract

The structural and functional complexity of the hu man interferon system has become increasingly evident. More than eight different alpha (leukocyte) interferons are expressed in induced human cells in culture. Many of these have been purified by a combination of methods, including high-performance liquid chromatography. Moreover, at least 12 different human leukocyte inter ferons have been cloned, and several have been effi ciently expressed in Escherichia coli and other orga nisms. The availability of purified species of leukocyte interferon, both natural and recombinant, has allowed structural work to be done, including amino acid se quence determinations, chemical modification studies, and the crystallization of one species. The purified ma terial has also been used for the production of mono clonal antibodies with various specificities that are proving invaluable in rapid assays and purification techniques. Testing of the purified species for their rel ative potency in antiviral, antiproliferative, and immu nomodulatory assays has begun to demonstrate the func tional uniqueness and diversity of the purified alpha interferons. Hybrid interferon genes have been synthe sized by splicing together parts of various cloned inter feron genes. The resulting hybrid proteins have been valuable in establishing structure/function relation ships. In several cases, the functional properties of the hybrid protein were novel and unpredicted from the properties of the parental molecules.Interferon was discovered by Isaacs and Lindenmann during an investigation of the phenomenon of viral interference, wherein infection by one virus produces resistance to subse quent infection by other, apparently unrelated viruses. Their work [1,2] and that of others [3] demonstrated that cells could respond to challenge with a virus or with other substances (subsequently termed inducers) by producing a substance that could confer upon other cells resistance to subsequent viral attack. This substance, termed interferon, was characterized as a protein that had some species specificity, but that was fairly nonspecific in protecting against a wide range of viruses.Since that time, the complexity of the system has increased as more interferon species within an organism have been rec ognized and characterized and biological effects have beenThe chemical heterogeneity of the interferons has become increasingly evident (Table I). It was found that interferons produced by different cell types were either stable or labile at pH 2. This lead to the designation of types I and II, respectively.Further work demonstrated that there were two main antigen-

Differential responsiveness of cloned mammary carcinoma cell populations to the human recombinant leukocyte interferon enhancement of tumor antigen expression

“…These clones should prove valuable in elucidating the mechanism by which interferon modulates tumor antigen expression in human breast carcinoma cells. It is well established that leukocyte interferon, unlike fibroblast (0) or gamma (y), is heterogeneous and consists of at least 12 related genes (Pestka, 1983a;Langer and Pestka, 1984). Studies will be conducted to determine whether those cells within a tumor population which are unresponsive to the tumor-enhancing actions of IFN-aA might be responsive to other leukocyte interferon species, combinations of leukocyte and fibroblast or gamma interferon or combinations of interferon with other inducers of differentiation.…”