Reduction in antiviral activity of human interferon-γ in acidic media with reference to structural change

doi:10.1016/0167-4838(87)90115-4

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology

Volume 916, Issue 2, 26 November 1987, Pages 245-250

Biochimica et Biophy...

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Abstract

The fluorescence intensity of a unique tryptohan 36 in human interferon-γ was drastically decreased below pH 4 with a concomitant decrease of antiviral activity. The region of residues 32–42 of human interferon-γ was found by calculation to have a low hydrophobicity together with a high helical hydrophobic moment, and the net electric charge of this region having an amphiphilic helical structure changed significantly near pH 4. These results suggest that the region of residues 32–42 plays am important role in exhibiting antiviral activity.

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Cited by (7)

Solution behavior of a novel type 1 interferon, interferon-τ
2005, Journal of Pharmaceutical Sciences
Citation Excerpt :
Not all interferons are stable under low pH conditions. In the case of interferon-γ, there is a reduction in both structural integrity and antiviral activity of the protein when it is formulated in acidic media (<pH 4).25 Even type 1 interferons have been found to be less stable at low pH. Sharma et al. recently found that the thermal denaturation behavior of IFN-α2a exhibits some pH dependence.26
Interferon-tau (IFN-tau) is a novel cytokine that appears during fetal development of mammals. It is currently being investigated for treatment of viral infections and autoimmune diseases. In order to develop a commercial product, a stable formulation will need to be identified. In this study, the solution behavior of IFN-tau was studied using a variety of biophysical methods. The overall structure of IFN-tau is well defined, with the polypeptide chain folding into a four-helix bundle structure, much like other type 1 interferons. However, its solution behavior has not been characterized. The globular structure has a free energy of unfolding of ∼4 kcal/mole at room temperature. IFN-tau was found to remain monomeric upon increasing the protein concentration, even up to 60 mg/mL. The overall structure of IFN-tau is maintained across a pH range of 2–8, but is significantly altered in the presence of nonaqueous solvents. However, IFN-tau appears to refold efficiently when diluted into an aqueous medium from a nonaqueous solution. This behavior allows the protein to be formulated in low water content formulations suitable for use in capsules. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association.
Conformational stability of human interferon-gamma on association with and dissociation from liposomes
2000, Journal of Pharmaceutical Sciences
Citation Excerpt :
Furthermore, protein adsorption often leads to unfolding and (subsequent) aggregation of the protein, which is pharmaceutically unacceptable. External factors, such as the pH and ionic strength of the medium, might influence the membrane–protein interactions.17–19 IFNγ is a molecule of 17 kD that in its bioactive form exists as a homodimer tightly associated by numerous, mostly hydrophobic interhelical interactions.20
The integrity of a therapeutic protein has to be safeguarded when formulated in delivery systems such as liposomes. In this study, we investigated the conformational stability of recombinant human interferon gamma (hIFNγ) on association with and after dissociation from liposomal bilayers using circular dichroism (CD) and steady‐state fluorescence spectroscopy as well as time‐resolved fluorescence methodology. We used hIFNγ adsorption to and desorption from empty liposomes as a model for hIFNγ‐containing liposomes prepared via the film hydration method. CD studies indicated that no changes in the secondary and tertiary protein structure occur during and after interaction of hIFNγ with the liposomes. Steady‐state fluorescence emission spectra of untreated and liposome‐desorbed hIFNγ revealed that the environment of the sole Trp residue was not affected by the adsorption/desorption process. The Trp‐36 residue remained fully quenchable by acrylamide after desorption of hIFNγ from the liposomes. Time‐resolved fluorescence studies were conducted to probe the local environment and the mobility of Trp‐36 before, during, and after interaction of hIFNγ with the liposomal membrane. Differences in rotational correlation time between free and liposomal hIFNγ were attributed to immobilization of the protein on adsorption to the liposome bilayer. Disparities were detected between the average lifetimes of liposome‐adsorbed hIFNγ and hIFNγ–liposomes, indicating that subtle changes in the Trp‐36 environment took place during preparation of the liposomes via the film hydration method compared with the adsorption of hIFNγ to the liposome surface. The results of this study indicate that association of hIFNγ with negatively charged liposomes results in minimal changes in the secondary and tertiary structure of the protein. We conclude that all techniques used point to a full retention or restoration of the protein conformation after desorption from the liposomes. © 2000 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89: 1605–1619, 2000
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Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology

Reduction in antiviral activity of human interferon-γ in acidic media with reference to structural change

Abstract

Cell. Immunol.

J. Mol. Biol.

Biochim. Biophys. Acta

Anal. Biochem.

Biophys. J.

J. Immunol. Methods

Methods Enzymol.

J. Biol. Chem.

Nature

Science

Science

Infect. Immun.

Biochemistry

Nature

Solution behavior of a novel type 1 interferon, interferon-τ

Conformational stability of human interferon-gamma on association with and dissociation from liposomes

Protein Stability in Downstream Processing

Immune interferon: Properties and clinical applications

Effect of Amino-Terminal Processing by Staphylococcus aureus V-8 Protease on Activity and Structure of Recombinant Human Interferon-γ

Stability of Protein Pharmaceuticals