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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3113 |
| Date | 2008 December 1900 |
| Creators | Dean, Dana Deanna |
| Contributors | Burghardt, Robert C., Wesh, C. Jane |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | electronic, application/pdf, born digital |
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