Interferons: Purification and Physicochemical Aspects

Abstract

Antiviral interferon activity in any one species can be exhibited by a variety of substances that differ in their physical and chemical properties, but the nature of these differences is not understood. Conditions that can lead to the formation of diverse types of interferons have been outlined. Reasons have been adduced why, for certain purposes, purification of interferons is desirable or even necessary, and examples have been presented to show how and to what extent this has been achieved. In spite of some very high purification factors, not a single interferon has been obtained as a pure substance. Therefore, all available knowledge of physical and chemical properties has been obtained by indirect means.The first interferon was discovered by Isaacs and Lindenmann (1) in 1957, and since then many biochemists have attempted to purify many interferons. It is perhaps worthwhile to pause for a moment and consider why it is sometimes necessary, or at least desirable, to work with purified rather than with crude interferons. WHY PURIFY INTERFERONS?Experiments with crude interferons have on several occasions led to wrong interpretations, and examples that show how this danger was sometimes overcome by purification or other means are presented. There are at least five situations where the use of crude interferons is inappropriate.Firstly, crude interferons, but also sera and tissue extracts from apparently normal animals, culture fluids from uninfected cells, urine, allantoic fluid, egg white, agar overlays, etc., frequently contain other often nonvirus-and nonspecies-specific antiviral substances that may simulate certain aspects of interferon action and may thus mislead the casual observer. A number of specific and nonspecific viral antagonists of this nature is shown in Table I which represents the "list of contents" of a recent'review article by Wassermann (2). But there are doubtless others, e.g. Buckler and Baron (3) showed that heterologous, acid-stable, antivaccinia virus activity of crude mouse sThe Journal of General Physiology interferon and of mouse serum could be readily removed from chick cells by mere washing. The same process also eliminated, again from chick cells, a noninterferon antivaccinia factor, present in normal allantoic fluid. Andrews (4) found that crude chick, calf, monkey, and human interferons had pronounced activity against vaccinia virus in rabbit skin, and even the noninfected, heterologous culture fluids themselves were active in this system. Similarly, the size of vaccinia lesions and the degree of necrosis in monkey skin were not reduced only by monkey interferon, but also by crude chick interferon. We, (5, 6) in collaboration with Doctors Andrews and Finter, found that crude allantoic chick interferon also had some activity in human embryonic lung cells and in mouse L cells against rhino-and Sendai viruses, respectively, but that partly purified and concentrated interferon, with much higher potency in chick cells, had lost its heterologous activity. Sutton and Tyrrell (7)...

Stabilisation of Mouse and Human Interferons by Acid pH Against Inactivation Due to Shaking and Guanidine Hydrochloride

“…One milliliter samples of the interferon preparations were placed in 110 X 15 mm glass-stoppered glass tubes, which were rotated end-overend at 50 rpm, at a temperature of 4°C. Under these conditions, the interferon preparations flowed from end to end of the tube, but very little or no foaming [known to inactivate interferon ( 12)] occurred.…”

Purification of Mouse Interferon by Affinity Chromatography on a Solid-Phase Immunoadsorbent

“…Previously described methods for purification of interferon have depended upon physicochemical properties of the molecule such as size, charge, and differential solubility (1,2). Alternatively, affinity chromatography, which is a method of separation based on biological specificity or antigenicity, would seem particularly well suited for the purification of interferon, which is present in extremely low concentrations in biological materials (3).…”

Effect of lead on interferon production and antiviral effect of interferon on Marek's disease in chickens

“…The physical and chemical properties of interferon have been determined by studying impure preparations and the extent to which impurities have contributed to the observed properties is as yet unknown (53).…”

“…The protein nature of interferon was first described (91). The isoelectric point varies from pH 5.0 to 10.0 (53) depending on its origin, inducer and host system (53). Disulfide bonds are required for interferon activity (119).…”

“…Some, but not all, interferons ere inactivated by urea (119). 15 Interferons are heterogeneous with regard to molecular weight and the presence of multiple molecular species in a single interferon preparation has "been reported (53). The range of molecular weight of interferon is very wide and varies from 28,000 to 160,000 (60), Carter and Pitha (27) think that human and mouse interferons are not a group of heterogeneous proteins.…”