Experimental autoimmune uveoretinitis: idiotypic regulation and disease suppression

Effect of vaccination against leptospirosis on the frequency, days to recurrence and progression of disease in horses with equine recurrent uveitis

OBJECTIVE

To evaluate the effect of vaccination against leptospirosis on frequency and days to recurrence of uveitis and progression of disease in horses with equine recurrent uveitis (ERU).

ANIMALS

Forty-one horses with ERU.

PROCEDURE

Horses were randomly assigned to experimental (vaccinated) or control groups. Vaccine containing six serovars of Leptospira or placebo was administered, an ophthalmic examination performed and blood samples drawn on days 0, 28, 180 and 365. Antibody titers were measured against each serovar. Recurrence of uveitis was verified by ophthalmic examination. Results of the initial and final ophthalmic examinations were compared and progression of disease defined as an increase in extent of synechiae, or development of new or progression of an existing cataract.

RESULTS

Vaccination increased the average geometric mean serum antibody titer from 225 on day 0, to 4077 and 593 on days 28 and 180, respectively. After the second vaccination, days to first recurrence was significantly longer (median 126 days; range 24-231 days) when compared with controls (median 86 days; range 14-192 days, P=0.04). Recurrence of ERU was observed among 7/20 (35%) vaccinated horses and 12/21 (57%) controls; however, this difference was not statistically significant (P=0.061, OR 0.25, 95% CI 0.06, 1.07). More horses in the experimental group 13/20 (65%) experienced progression of disease when compared with controls 12/21(57%); however, this difference was statistically nonsignificant (P=0.35).

CONCLUSIONS

Vaccine significantly increased days to recurrence, but failed to slow the progression of disease. These data do not support the use of vaccination against leptospirosis as adjunct therapy for the routine treatment of horses with ERU.

Anti-idiotype immunomodulation of experimental anti-phospholipid syndrome via effect on Th1/Th2 expression

Mice with experimental anti-phospholipid syndrome (APS), induced by active immunization with a human anti-cardiolipin MoAb (H-3), were treated with mouse anti-idiotypic MoAb (anti-H3, named S2.9) and with an irrelevant anti-idiotype. The immunized mice produced high titres of mouse anti-cardiolipin antibodies along with clinical manifestations of experimental APS: prolonged activated partial thromboplastin time (aPTT), thrombocytopenia and high rate of fetal loss. Treatment with the specific anti-Id (S2.9) as a whole molecule or F(ab)2 fraction, resulted in a decrease in serum levels of the anti-cardiolipin antibodies, rise in platelet count, shortened aPTT and reduced rate of fetal loss. The anti-Id effect was associated with a rise in the number of IL-2 and interferon-gamma (IFN-gamma)-secreting cells (Th1) and reduction in IL-4- and IL-6-secreting cells (Th2). The beneficial effect of the anti-Id treatment in mice with experimental APS induced by active immunization with an idiotype further supports the idiotypic aetiology of experimental APS and points to the role of Th1 cytokines in suppression of its manifestations.

Immunotolerance and prevention of ocular autoimmune disease

Immunotherapeutic approaches to autoimmune disease have a common goal of inducing antigen-specific, long-lasting tolerance to autoantigens, without otherwise compromising the immune response. Here we review some of the most interesting experimental advances in this area. We discuss the use of T cell targeting drugs that have been reported to induce long lasting tolerance to ocular antigens. Strategies involving the targeting of idiotypic and clonotypic determinants associated with ocular autoimmunity, such as idiotypic network manipulation and T cell vaccination, are reviewed. The use of cytokines to promote perturbation of the Th1/Th2 balance with its possible implications for treatment of uveitis, is analysed. Finally, we review tolerogenic strategies based on acquisition of tolerance following presentation of antigen through alternative routes, such as injection of antigen into the anterior chamber, intravenous infusion of antigen, and oral administration of retinal antigens. Special emphasis is placed on the last strategy, since there are ongoing clinical trials using oral tolerance as an immunotherapeutic approach to treat autoimmune diseases, among them uveitis.

Suppression of experimental systemic lupus erythematosus (SLE) with specific anti-idiotypic antibody-saporin conjugate

The importance of the idiotypic network is represented in experimental SLE induced by active immunization of naive mice with an anti-DNA idiotype (Ab1) emulsified in adjuvant. The mice after 4 months of incubation generate Ab3 having anti-DNA activity. In addition, the mice develop other serological markers for SLE associated with clinical and histopathological manifestations characteristic of the disease. To confirm further the etiological role of the idiotype in this experimental model, the mice were treated with specific anti-idiotypic antibodies (anti-Id) which were also conjugated to a toxin-saporin (Immunotoxin (IT)). Pretreatment of hybridoma cell line producing the anti-anti-Id (anti-DNA = (Ab3)) for 48 h with the anti-Id MoAb (Ab2) reduced the production of anti-DNA by 58%, while pretreatment with the IT resulted in 86% decrease in anti-DNA secretion (saporin alone had only 12% effect). The anti-Id MoAb had no effect on the production of immunoglobulin by an unrelated cell line. In vivo treatment of mice with experimental SLE led to a significant decrease in titres of serum autoantibodies, with diminished clinical manifestations. The results were more remarkable when the IT was employed. These suppressive effects were specific, since an anti-Id treatment of experimental anti-phospholipid syndrome was of no avail. The anti-Id effect was mediated via a reduction in specific anti-DNA antibody-forming cells, and lasted only while anti-Id injections were given. Discontinuation of the anti-Id injection was followed by a rise in titres of anti-DNA antibodies. No immunological escape of new anti-DNA Ids was noted. Our results point to the importance of pathogenic idiotypes in SLE and to the specific potential of implementing anti-idiotypic therapy, enhanced by the conjugation of the anti-Id to an immunotoxin, in particular one with low spontaneous toxicity.