Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2009
Publication Date: 4/1/2009
Citation: Hoesing, L.M., Noh, S.M., White, S.N., Snekvik, K.R., Truscott, T.C., Knowles Jr, D.P. 2009. Peripheral Ovine Progressive Pneumonia Provirus Levels Correlate with and Predict Histological Tissue Lesion Severity in Naturally Infected Sheep. Clinical and Vaccine Immunology. 16(4):551-557.
Interpretive Summary: Post-mortem histological assessment of tissues is the reference standard for determining the extent of disease in an ovine progressive pneumonia virus (OPPV) infected sheep. This study evaluated whether systemic host antibody responses to OPPV and/or peripheral OPP provirus levels correlated with the severity of histological lesions in lung, mammary gland, carpal synovial joints, or brain of eleven OPPV infected ewes (mean age of 8.6 years). Tissue sections were graded for histological lesion severity. Serum anti-OPPV antibody responses and OPP provirus levels in peripheral blood leukocytes were measured 3 years prior to and at euthanasia and evaluated for their correlation with the severity of histological lesions in any of the OPPV affected tissues. The results of the study showed a significant correlation between peripheral ovine progressive pneumonia (OPP) provirus levels 3 years prior to and at euthanasia and the highest histological lesion score in any tissue. In contrast, serum anti-OPP virus antibody titers 3 years prior to and at euthanasia did not significantly correlate with the highest histological lesion score in any tissue. This suggests that peripheral OPP provirus level can be utilized as a live-animal marker of disease progression in OPPV infected sheep.
Technical Abstract: Studies were undertaken to determine whether host immune responses in the form of serum anti-ovine progressive pneumonia virus (OPPV) antibody responses or virus replication in the form of peripheral OPP provirus levels associate with the degree of histological tissue lesions in naturally OPPV infected sheep. Sections of formalin-fixed, paraffin-embedded and eosin and hemotoxylin stained lung, mammary gland, carpal synovial membrane and brain were evaluated for the extent of histological lesions from 11 OPPV infected ewes (mean age of 8.6 years) and 5 OPPV uninfected ewes (mean age of 6 years). OPP provirus levels and anti-OPPV antibody titers were measured in peripheral blood leukocytes and serum, respectively, at euthanasia and 3 years prior to euthanasia. Both mean peripheral OPP provirus levels and mean serum anti-surface envelope glycoprotein (SU) antibody titers at euthanasia were significantly higher in ewes categorically grouped as showing moderate to severe histological lesions than in ewes as showing no to mild histological lesions. However, although mean peripheral OPP provirus levels at euthanasia and 3 years prior to euthanasia significantly correlated with the highest histological lesion score in any affected tissue (2-tailed P values=0.02, 0.01), mean serum anti-SU antibody titers, anti-capsid (CA) antibody titers, or anti-transmembrane 90 (TM90) antibody titers at euthanasia did not show a significant correlation with the highest histological lesion score in any tissue (2-tailed P values=0.42, 0.72, 0.35, respectively). These data are the first to show that OPP provirus levels predict and correlate with the extent of OPPV related histological lesions in various OPPV affected tissues. These findings suggest that peripheral OPP provirus levels quantitatively contribute more to the development of histological lesions than the systemic anti-SU antibody host immune response.