Interferon Activity in Bovine Colostrum and Milk

Abstract

Studies have shown that IFNs have potent immunologic (1,2) and antiviral (3,4) activity in both in vitro and in vivo testing in the bovine species. In calves given IFN orally, enteric disease due to rotavirus or mixed rotavirus and coronavirus infection was prevented or reduced(5). Interferons are also involved in immunity to protozoal infections (6), and a polypeptide with many characteristics similar to an alpha IFN has been identified that stimulated macrophages to inhibit intracellular development of Eimeria bovis (7). In preliminary studies, calves administered partially purified natural bovine alpha IFN intravenously had less coccidial diarrhea than control calves (8).

Although lymphocytes isolated from human colostrum and milk are capable of producing interferon ( IFN) when stimulated in vitro (9,10), assays of human colostrum and milk for IFN have usually yielded negative results (9-11). Since bovine peripheral blood lymphocytes, when stimulated with virus, are capable of producing alpha IFN (12), it would seem logical that these cells in mammary secretions would also have this ability. The only citation of the spontaneous occurrence of IFN in milk or colostrum from any species is a brief mention that a sample from one woman's breast milk contained antiviral activity (11). It was not known whether this woman was infected with a virus (11). It has been well documented, however, that when mother mice were inoculated with Newcastle disease virus, their milk contained measurable lFN (7). Furthermore, the newborns suckling such mothers had a significantly greater survival rate than that of controls after lethal challenge with vesicular stomatitis virus (7).

Since most mammalian infants have a lower incidence of neonatal disease when raised on maternal milk as opposed to milk replacer (13,14), it was hypothesized that interferons in mammary secretions may play an important role in neonatal immunity. Since bovine milk and colostrum had not been heretofore examined, the objective of this study was to determine whether IFN could be found in detectable levels in normal bovine colostrum and milk.