Encapsulated interferon-tau during Theiler's virus-induced demyelinating disease: efficacy of treatment and immune response profile

• Main Author: Dean, Dana Deanna
• Other Authors: Burghardt, Robert C.
• Format: Others
• Language: en_US
• Published: 2011
• Subjects: multiple sclerosis; interferon
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-3113

Multiple sclerosis (MS) is the most common primary demyelinating disease of the central nervous system in humans. Type I interferons are most frequently used to treat MS. However, their main mechanism of action remains elusive. Various biomarkers have been investigated for their ability to assess treatment efficacy, but results are often confounding due to differences in experimental design and variation in individual physiology. In fact, not all MS patients respond to IFN therapy and a significant number suffer severe negative side effects and must cease treatment. Thus, alternative therapeutics that offer less cytotoxicity and greater efficacy are a major objective of research. This dissertation evaluated a novel type I interferon, interferon-tau (IFNT), and its ability to attenuate Theiler’s virus-induced-demyelinating disease (TVID), a mouse model of MS. In this model, viral infection with the BeAn strain of Theiler’s murine encephalomyelitis virus (TMEV) is the initiating factor leading to demyelination of the CNS. It was hypothesized that IFNT would: 1) provide therapeutic benefit as witnessed by a stabilization of clinical score, a decrease in CNS inflammation, and a decrease in CNS demyelination, and 2) shift the immune profile from a Th1 to a Th2 response. Once mice developed chronic disability, IFNT treatment began. This novel IFN was delivered in an innovative way: encapsulation (eIFNT) in an alginate polymer, which allowed for slow and sustained release. eIFNT was delivered by a 100 μl intraperitoneal injection (i.p.) containing 1.4M U of IFNT once every two weeks for 8 weeks. Mice were clinically scored weekly and BeAn-eIFNT mice demonstrated a decrease in clinical score. Bright field microscopy was used to evaluate CNS tissues where a decrease in demyelination and inflammation was noted in BeAn-eIFNT-treated mice. Ex vivo stimulation of virus-specific lymphocytes revealed an increase in both T helper 1 (Th1) and T helper 2 (Th2) cytokine production. Specifically, TNFA was produced at very high levels by splenocytes from BeAneIFNT mice in response to UV-inactivated BeAn alone and in the presence of IFNT when compared to BeAn-eMOPS mice under the same conditions. IFNG was produced at elevated levels from the splenocytes of BeAn-eIFNT mice versus BeAn-eMOPS mice when stimulated in vitro with UV-inactivated Bean and with BeAn in the presence of IFNT. IL-2 was produced at moderately elevated levels from the splenocytes of BeAn-eIFNT mice versus BeAn-eMOPS mice when stimulated in vitro with UV-inactivated Bean. Il-2 was elevated to a statistically significant level (p<0.05) from BeAn-eIFNT mouse splenocytes when stimulated with BeAn in the presence of IFNT when compared to BeAn-eMOPS mice and IL-10 was produced at elevated levels by splenocytes from BeAn-eIFNT mice versus that produced from BeAn-eMOPS mouse splenocytes in response to UV-inactivated BeAn alone and in the presence of IFNT. Quantification of T regulatory (Treg) cells in the spleen of eIFNT vs. eMOPS mice and blood of eIFNT vs. eMOPS mice revealed no difference between the two groups. There was no statistical difference in virus-specific serum antibodies at the pretreatment time point noted in the OD readings of eIFNT mice at a dilution of 1/200 compared to the eMOPS mice. A modest decrease in the OD values at the 1/200 dilution were noted in the eIFNT mice compared to the eMOPS mice, but this difference was not significant. Antibody secreting cells (ASCs) from eIFNT mice versus eMOPS mice were slightly lower in the spleen and brains whereas there was a slight increase in ASCs from the spinal cord of eIFNT mice when compared to those from eMOPS mice. Altogether, the results support efficacy of the eIFNT treatment in the mice with TVID. Actual mechanisms of disease attenuation remain elusive at this time as mice exhibited an increase in certain Th1 and Th2 cytokines rather than the hypothesized shift from a Th1 to a Th2 immune profile. Likewise, mice exhibited a modest decrease in virus specific antibodies as well as the number virus-specific ASCs which also refute the hypothesized increase in these values. A remarkable finding was the fact that immune cells derived from eIFNT treated mice appeared to be divided into two distinct types of biological responders although all of the mice responded to the in vivo treatment with a decrease in disease severity. It is hypothesized that this difference is a reflection of individual genetic variability in response to immune modulation which is surprising owing to the fact that the animals used for these studies are in-bred and considered to be as identical genetically as is feasible in a population of animals. Obviously, immune modulation can proceed through different mechanisms and still provide the desired result of a decrease in disease severity. However, this reality creates an added level of difficulty when one is trying to interpret biological data in order to determine whether a therapeutic regimen is efficacious within a patient population.