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Is TB Testing Associated With Increased Blood Interferon-Gamma Levels?
Kennedy, Aideen E. O’Mahony, Jim Byrne, Noel MacSharry, John Sayers, Riona G.
Kennedy, Aideen E.
O’Mahony, Jim
Byrne, Noel
MacSharry, John
Sayers, Riona G.
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2017-10-23
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Kennedy AE, O’Mahony J, Byrne N, MacSharry J and Sayers RG (2017) Is TB Testing Associated With Increased Blood Interferon-Gamma Levels? Front. Vet. Sci. 4:176. doi: 10.3389/fvets.2017.00176
Abstract
The Republic of Ireland reports a relatively low prevalence of Johne’s disease (JD)
compared to international counterparts. Postulated reasons for this include a lower
average herd size and a grass-based production system. Ireland also engages in high
levels of bovine tuberculosis (bTB) testing. As interferon-gamma (IFN-γ) is believed to
play a key role in protecting against JD, it is our hypothesis that administration of purified
protein derivative (PPD), as part of the bTB test, is associated with a systemic increase
in IFN-γ production, which may potentially limit clinical progression of the disease.
We studied 265 cows (202 Friesian and 63 “Non-Friesian,” e.g., JerseyX, Norwegian Red)
to assess IFN-γ levels and Mycobacterium avium subspecies paratuberculosis (MAP)
antibody response before and after the bTB test. As part of the compulsory annual bTB
test, avian and bovine PPD were administered at two separate cervical sites. To assess
IFN-γ production, blood samples were taken before and 72 h after PPD administration.
MAP antibody response was assessed before and 10 days post-PPD administration.
A significant increase in MAP antibody response was identified post-bTB compared to
pre-bTB response (p < 0.001). Additionally, IFN-γ production significantly increased at
the post-bTB time point (p < 0.001) compared to the pre-bTB test readings. This may
indicate a beneficial effect of bTB testing in controlling JD.