Humoral immune responses in the horse after intrathecal challenge with ovalbumin

Background : Diagnosis of neuro-inflammatory conditions in the horse can be challenging. Current methods include evaluation of cerebrospinal fluid (CSF) for inflammation and determination of specific antibody status. The antibody index (AI) and Goldman-Witmer coefficient (C-value) can be used to aid in the interpretation.
Hypothesis : The null hypothesis to be tested was that the AI and C-values do not change in horses with neuro-inflammation.
Animals : Twelve horses of various ages (3–17 years) and breeds (Thoroughbred, Thoroughbred cross, draft, and Arabian) were included in the study.
Methods : The study was designed as a prospective randomized study. All horses were immunized with ovalbumin in adjuvant, twice. Horses of Group 1 then were challenged by intrathecal (IT) injection of ovalbumin, whereas horses of Group 2 were challenged IM. The AI and C-values for ovalbumin and equine herpesvirus were calculated.
Results : The AI for ovalbumin increased up to 5.92 in horses after intrathecal challenge, and remained normal (<1) in horses challenged IM. The C-value for ovalbumin reached a peak of 7.48, whereas for equine herpesvirus it achieved a value of 2.69. The changes in ovalbumin C-value and AI were significantly different between days 20 and 30 in horses after intrathecal challenge at day 20 ( P = .002 and .0005, respectively).
Conclusions and Clinical Importance : The results confirm the value of the AI and C-value in the evaluation of neuro-inflammation in the horse.