Effects of early IL-17A neutralization on disease induction in a primate model of experimental autoimmune encephalomyelitis

Abstract

We report on the effect of antibody-mediated neutralization of interleukin (IL)-17A in a non-human primate experimental autoimmune encephalomyelitis (EAE) model induced with recombinant human myelin oligodendrocyte glycoprotein (rhMOG). We tested a human-anti-human IL-17A-antibody in two doses (3 and 30 mg/kg) against placebo (PBS). The treatment was started 1 day before EAE induction and continued throughout the experiment. Although all monkeys developed clinically evident EAE, the onset of neurological signs was delayed in some monkeys from both treatment groups. Total CNS lesion volumes, demyelination, or inflammation did not differ between the different groups. Immune profiling revealed an altered distribution of IL-17A producing cells in the lymphoid organs of antibody-treated monkeys. Comparable numbers of IL-17A producing cells were observed in the brain. RhMOG-induced T cell proliferation in the lymph nodes was slightly reduced after anti-IL-17A antibody treatment. To summarize, we found that anti-IL-17A antibody as a single treatment from disease induction effects a trend towards delayed neurological disease progression in the marmoset EAE model, although the effect did not reach statistical significance. This suggests a role of IL-17A in late stage disease in the marmoset EAE model, but IL-17A may not be the dominant pathogenic cytokine.

Fig. 1

Plasma levels of anti-human IL-17A mAb were sustained during the study. Once a week, animals received a subcutaneous injection with 1 ml/kg PBS (not shown), 3 mg/kg anti-IL-17A mAb (left graph), or 30 mg/kg anti-IL-17A mAb (right graph) starting 1 day before immunization. Plasma was collected from venous blood at several time points during the study and anti-IL-17A mAb levels in plasma were determined by ELISA. The y-axis have log scales. As expected, the anti-IL-17A mAb plasma levels in the control animals were throughout the experiment similar to the value on post-sensitization day 0 of the treated animals (not shown). M04099 and M03144 of the low antibody dose group were not able to sustain a trough level of the antibody above 1 μg/ml

Fig. 2

Clinical score and body weight loss of rhMOG-immunized marmosets. Shown are the clinical score (solid line, right y-axis) and the body weight change in percentages compared with day 0 (dotted line, left y-axis) of the placebo group (left graphs), the low dose group (middle graphs), and the high-dose group (right graphs). Numbers in the figure represent the time points (psd) when neurological signs (score ≥2) were first observed and the day of sacrifice

Fig. 3

Survival curves. Survival time to score 2 (a) and survival time to day of sacrifice (b) are shown. p Values indicated in the graph are the results of comparing three groups. Comparing the survival to the day of sacrifice of the control group versus only the 3 mg/kg group resulted in a p value of 0.1610. When two animals of the 3 mg/kg group with low anti-IL-17A mAb plasma levels (M04099 and M03144) are included in the control group instead of the 3 mg/kg group, the p value is 0.0428. According to the Bonferroni correction this is not significant, but it is highly suggestive for a delay in disease progression

Fig. 4

Differential expression of IL-17A in the brain and lymphoid organs. IL-17A expression was detected by immunohistochemistry. a (200×) Representative examples of each group for brain, spleen, and axillary (ALN), inguinal (ILN), and cervical (CLN) lymph nodes. b IL-17A positive cells per mm² (mean ± SEM). Only one CLN of the control group was analyzed. No IL-17A producing cells were detected in the ILN of the 30 mg/kg treated group. Statistical differences between the numbers of IL-17A positive cells were analyzed by One-way ANOVA. Results were considered statistically different at p < 0.05. No statistical differences were found between the three groups

Fig. 5

T cell responses after anti-IL-17A mAb treatment. PBMC and mononuclear cells isolated from the axillary lymph node and spleen at necropsy were tested for proliferation against rhMOG and MOG peptides. The stimulation index (SI) was calculated by dividing the counts per minute (cpm) of stimulated wells by cpm of unstimulated wells. The stimulation index is divided into groups with different shading as indicated in the figure