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Because of the importance of rat models in the study of malignant, viral and immune pathogenesis, Access BioMedical provides sterile, lyophilized rat interferon for research use which is suitable in undiluted form for parenteral use by intravenous, intramuscular, intraperitoneal and subcutaneous routes and is not cytotoxic in vitro at dilutions of about 1/25 or higher. This interferon has been partially characterized in our laboratory as follows:

Pattern Of Induction

A continuous rat kidney fibroblast cell strain of our derivation, designated RtK, has been examined for interferon production in response to a variety of induction schemes. Modest quantities of interferon are produced in response to induction by poly I:C and poly I:C/DEAE- dextran complex. The cells respond well to the superinduction regimen using poly I:C/cycloheximide/actinomycin D and less well to superinduction with polyI:C/cycloheximide (no actinomycin) or poly I:C/actinomycin (no cycloheximide). Of three viral inducers tested the interferon yields are highest with Newcastle disease virus (NDV, Manhattan strain), intermediate with reovirus type 3 (Dearing) and lowest for parainfluenza type 1 (Sendai).

Priming of the rat cells by mouse alpha, beta or alpha + beta interferons had no detectable effect on yields of rat interferon except for the poly I:C/cycloheximide/actinomycin regimen where yields were increased 3- to 5- fold by pretreatment with any of the mouse interferon preparations.

Stability at pH 2

The antiviral activity, in both homo- and heterospecific cell cultures, of NDV- induced rat interferon is completely stable in extended incubation at pH 2 at 4 degrees C. Since the rat interferon products are prepared from rat kidney fibroblasts induced with virus, and since the crude materials are routinely held at pH 2.2 for some days prior to further processing, we conclude that the rat interferon products contain no acid- labile or gamma activity, but are clearly of the acid- stable, alpha and/or beta type; they have not been characterized further as regards composition of individual alpha and beta species.

Heterologous Antiviral Activities

The NDV- induced rat interferon has been assayed in heterologous cell cultures challenged with encephalomyocarditis (EMC) virus. The cross- reactivities (as percentage of homologous titer, absolute units) were: human diploid fibroblasts, 0.02- 0.08%; mouse L- cells, 30- 50%; rabbit kidney (RK13) cells, <0.005%.

In reciprocal experiments human, mouse and rabbit interferons have been assayed in RtK rat kidney fibroblasts challenged with vesicular stomatitis virus (VSV). The cross- reactivities were: human fibroblast IFN (beta), 0.2- 0.4%; human lymphoblastoid IFN (alpha, ex Namalva), 10%; human leukocyte IFN (alpha), 0.1%; mouse IFN (alpha), 5- 10%; mouse IFN (beta), 0.02- 0.2%; mouse IFN (alpha + beta), 1.2- 3.5%; rabbit IFN, <0.005%.