Quantitative evaluation of leukocyte infiltration into the spinal cord in a model of experimental autoimmune encephalomyelitis: Statistical-analytical techniques for use in evaluating drugs

Experimental autoimmune encephalomyelitis (EAE) is considered a useful animal model for preclinical development of drugs to treat human multiple sclerosis. The relationship between clinical disease signs and leukocyte infiltration into the lower spinal cord was studied in EAE in order to assess analytical and statistical methods for evaluating drug candidates. As expected, the degree of clinical disease was correlated with the amount of leukocyte infiltration into the lower spinal cord. Additionally, we were able to distinguish patterns of clinical signs and leukocyte: infiltration for classes of recurring-remitting and progressive forms of the disease. The distributions of leukocyte infiltration sites correspond to negative binomial distributions, and the parameters calculated from the respective distributions differ significantly among disease classes. We determined the sensitivity of histological measures of the leukocyte infiltration and calculated the magnitude of differences required in order to observe statistically significant changes in leukocyte infiltration. Using immunohistochemistry to assess cell surface markers of leukocytes in the lower spinal cord, we measured the infiltration of CD4+ and CD8+ lymphocytes and cells of the macrophage/ microglial lineage stained with the monoclonal antibody, F4/80. Treatment with an anti-4 integrin monoclonal antibody, PS/2, served as an indicator of how we may expect to measure the effects of new pharmaceutical agents tested using our particular model of EAE. PS/2 treatment affected clinical signs of disease only when administered very early in the time course of the disease, despite a marked statistically significant decline in CD4+ cells regardless of when the PS/2 was administered. The analytical and statistical techniques applied here may be used to design efficient and sensitive assays for the evaluation of new drugs that may prove useful in the treatment of multiple sclerosis.