Investigation of the therapeutic potential of ES-62 in a murine model of SLE

Rodgers, David T. (2013) Investigation of the therapeutic potential of ES-62 in a murine model of SLE. PhD thesis, University of Glasgow.

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Autoimmune inflammatory disorders such as systemic lupus erythematosus (SLE) remain debilitating conditions, as many patients are refractory to existing conventional and biologic therapies or suffer serious adverse effects, such as susceptibility to catastrophic infection. Therapies based on the actions of parasite- derived immunomodulators that dampen inflammation to promote the survival of the parasite without seriously immunocompromising the host, may therefore provide alternative strategies for the development of novel and safer drugs. One such molecule, ES-62, protects against disease in mouse models of rheumatoid arthritis and asthma; in both of these pathologies, suppression of disease is due to modulation of pathogenic IL-17A responses. As IL-17A has been implicated in the pathogenesis of SLE, in this thesis, the therapeutic potential of ES-62 is explored in the MRL/lpr mouse model of SLE.
SLE is characterized by autoantibody responses to dsDNA, as well as other nuclear and cytoplasmic antigens, which result in the deposition of autoantibody- immune complexes that cause localized inflammation in tissues with dense capillary networks, most often the skin, joints and kidneys. The MRL/lpr mouse is genetically predisposed to develop lupus-like pathology displaying many of the characteristics of human disease, including the major cause of morbidity, glomerulonephritis. Twice weekly treatment of MRL/lpr mice with ES-62 significantly suppressed the development of proteinuria, a direct measure of renal dysfunction. Despite drastic improvement in renal function, the kidneys from ES-62 treated mice did not show substantial improvement in histopathology as indicated by the overall levels of glomeruloproliferation, cellular infiltration and complement or immunoglobulin deposition in the kidneys. However, exposure to ES-62 did reduce the expression of complement (C3aR and C5aR) and immunoglobulin receptors (FcγRI (CD64)), thus rendering renal cells hypo-responsive to these pro- inflammatory stimuli. Moreover, by modulating MyD88 signaling, ES-62 likely suppresses renal cell responsiveness to chronic DAMP and IL-1 signals as well as potentially promoting glomerular barrier stability.

Consistent with their hypo-responsive phenotype, renal fibroblasts from ES-62 treated mice produced less MCP-1 in response to TLR stimulation and this was associated with reduced infiltration into the kidney by effector T and B cells and granulocytes; along with the ability of the parasite product to modulate the production of the pro-inflammatory cytokines IL-17A and IL-22. ES-62 suppressed the production of IL-22 both prior to and following onset of disease suggesting a key role for this cytokine in lupus pathogenesis, a proposal confirmed by neutralization studies which demonstrated that IL-22 played an essential role in the development of disease in the MRL/lpr mouse. This was further supported by studies showing that recombinant IL-22 significantly accelerated and exacerbated disease. By contrast, despite suppressing early IL-17A responses, the production of IL-17A was significantly increased in ES-62 treated mice during the established phase of disease, suggesting that IL-17A may promote pathogenesis during the initiation of pathology, yet act to resolve aberrant inflammation in the kidney. This potential dual role for IL-17A in the regulation of kidney inflammation was corroborated by studies using neutralizing antibodies and recombinant IL-17A, as the early neutralization of IL-17A production slowed the onset and severity of proteinuria and the late administration of rIL-17A suppressed disease severity.
Aberrant B cell responses drive pathogenesis both in murine models of SLE and also in human disease: reflecting this, B cell depleting therapies have proved successful in the clinic. Thus, the effects of ES-62 on the population dynamics of effector and regulatory B cell subsets were investigated and these studies revealed that ES-62 induced a hypo-responsive B cell phenotype that was associated with modulated development, migration and/or activation of pathogenic effector B cells. Furthermore, the proportion of IL-10 producing ‘regulatory’ B cells were significantly elevated in the ES-62 treated MRL/lpr mice during the established phase of disease. Crucially, the protection afforded against the development of proteinuria by ES-62 was mimicked by the adoptive transfer of B cells from ES-62 treated MRL/lpr mice: moreover, such protection was associated with modulation of the IL-17A/IL-22 axis, as observed in MRL/lpr mice treated with ES-62.

Together with previous reports on the therapeutic potential of ES-62 in arthritis and asthma, these studies suggest that therapies based on the parasite product have a future in the clinic. ES-62 itself is not suitable as a therapy, due to it immunogenic nature and the complexity of its biosynthesis: thus small molecular analogues (SMAs) of the parasite product have been synthesized. Two of these were tested in the MRL/lpr mouse and found to suppress the development of proteinuria, even when administered after the onset of pathology. This protection, as with that afforded by ES-62, was associated with a modulation of MyD88 signaling in the kidney and indicates that novel drugs, based on the safe modulation of the immune system by the parasite derived product, ES-62, have the potential to treat lupus nephritis in SLE patients.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: SLE
Subjects: Q Science > QR Microbiology > QR180 Immunology
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity > Immunology & Infection
Supervisor's Name: Harnett, Professor Magaret
Date of Award: 2013
Depositing User: Dr David T Rodgers
Unique ID: glathesis:2013-4771
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 07 Apr 2014 10:22
Last Modified: 07 Apr 2014 10:35

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