Detection of antibodies to ovine herpesvirus-2 interleukin-10 homologue in sheep-associated malignant catarrhal fever

Abstract EN

Interleukin-10 (IL-10) interferes with monocyte and macrophage activation of Th1 helper lymphocyte production of nitric oxide and synthesis of various inflammatory mediators.

An IL-10 homologue (vIL-10) is produced by several herpes viruses and is hypothesized to help the virus down regulate, and thus evade, host immune responses.

The gammaherpes rhadinovirus Ovine herpesvirus-2 (OvHV-2) encodes an IL-10 like molecule highly homologous to mammalian IL-10.

This virus causes sheep-associated malignant catarrhal fever (MCF), the most common form of MCF in the United States.

MCF is a lymphoproliferative and inflammatory syndrome that has delayed clinical presentation hypothesized to be influenced by the production of vIL-10.

For this study, the gene encoding vIL-10, Ov2.5 ORF, was amplified by PCR, cloned, sequenced, and a predicted 30 amino acid segment from the amino terminus synthesized.

This synthetic peptide was used to develop a novel direct enzyme-linked immunosorbant assay (ELISA) to detect isotype-specific antibodies to OvHV-2 vIL-10.

Work to date indicates that lambs do not have detectable levels of maternally derived antibody to vIL-10 during the first few weeks of age.

Ewes, which are refractory to clinical infection, generally have high levels of antibody to vIL-10.

A weak correlation exists between the vIL-10 ELISA and a commercially available competitive-inhibition ELISA (cELISA).

We believe the vIL-10 ELISA will refine the ability to identify ruminants exposed to sheep-associated MCF, provide an important tool for determining the role of vIL-10 in disease pathogenesis, and may contribute toward the development of a new vaccine strategy for the control of malignant catarrhal fever.