Page 882 - Veterinary Immunology, 10th Edition

receptor complex consisting of IL-10Rβ and IL-28Rα. While
VetBooks.ir structurally unrelated to type I interferons, they induce similar

intracellular signals and a similar gene expression profile. Their
effects are most apparent at intestinal and respiratory epithelia and

at the blood-brain barrier (Box 27.1).

Box 27.1

Measuring Interferons

Interferons may be assayed by measuring their antiviral effects. For

example, serum samples to be tested for interferon activity are
added to fibroblast cultures at various dilutions and incubated for
18 to 24 hours. The fibroblast monolayers are then washed, and a

standard quantity of bovine vesicular stomatitis virus is added to
each culture. After 48 hours of incubation, the monolayers are
stained, and virus plaques are seen as cleared areas in the
monolayer. The presence of interferons in the test serum will
reduce the number of plaques formed. This is called a plaque

reduction assay.

Antiviral Activities

The two major type I interferons (IFN-α and IFN-β) are produced
within a few hours of viral invasion, and high concentrations are
achieved long before adaptive immunity develops. For example, in

cattle infected with bovine herpesvirus-1 (BHV-1), peak interferon
levels in serum are reached 2 days later and then decline, but they
are still detectable by 7 days (Fig. 27.3). In contrast, antibodies are
not usually detectable in serum until 5 to 6 days after the onset of a
virus infection.

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