Biology subjects

Gigley, J.

Publications and source records attributed to Gigley, J..

4 recordsLinked to original sources

bioRxiv2019

Anti-Asialo GM1 treatment during secondary Toxoplasma gondii infection is lethal and depletes T cells

Using vaccine challenge model of T. gondii infection, we found that treatments with two commonly used for NK cell depletion antibodies resulted in different survival outcomes during secondary infection. Anti-ASGM1 resulted in 100% death and greater parasite burden at the site of infection than anti-NK1.1. Anti-NK1.1 treatment resulted in increased parasite burdens, but animals did not die. Further we found that anti-ASGM1 treatment depleted T cells. CD8+ T cells were more susceptible that CD4+ T cells to the treatment. ASGM1 was expressed on a higher percentage of CD8+ T cells than CD4+ T cells and CD8+ T cells. In T. gondii-immunized animals ASGM1 was enriched on effector memory (Tem) and central memory (Tcm) CD8+ T cells. However, Tem were more susceptible to the treatment. After secondary infection, Tem, Tcm, effector (Tef) and naive (Tn) CD8+ T cells were positive for ASGM1. Anti-ASGM1 treatment during reinfection resulted in greater depletion of activated IFN{gamma}+, Granzyme B+, Tem and Tef than Tcm and Tn CD8+ T cells. Anti-ASGM1 also depleted IFN{gamma}+ CD4+ T cells. Recombinant IFN{gamma} supplementation prolonged survival of anti-ASGM1 treated mice, demonstrating that this antibody eliminated IFN{gamma}-producing T and NK cells important for control of the parasite. These results highlight that anti-ASGM1 antibody is not an optimal choice for targeting only NK cells and more precise approaches should be used. This study uncovers ASGM1 as a marker of activated effector T cells and the potential importance of changes in sialylation in lipid rafts for T cell activation during T. gondii infection.

immunology↗

bioRxiv2019

Iron activates microglia and directly stimulates indoleamine-2,3-dioxygenase activity in the N171-82Q mouse model of Huntington's disease

Huntingtons disease (HD) is a neurodegenerative disorder caused by a dominant CAG-repeat expansion in the huntingtin gene. Morphologic activation of microglia is a key marker of neuroinflammation that is present before clinical onset in HD patients. The kynurenine pathway of tryptophan degradation is restricted in part to microglia and is activated in HD, where it contributes to disease progression. Indoleamine-2,3-dioxygenase (IDO) is a microglial enzyme that catalyzes the first step in this pathway. HD brain microglial cells also accumulate iron; however, the role of iron in promoting microglial activation and the kynurenine pathway is unclear. Based on analyses of morphological characteristics of microglia, we showed that HD mice demonstrate an activated microglial morphology compared with controls. Neonatal iron supplementation resulted in additional microglial morphology changes compared with HD controls. Increased microglial activation in iron-supplemented HD mice was indicated by increased soma volume and decreased process length. In our assessment of whether iron can affect the kynurenine pathway, iron directly enhanced the activity of human recombinant IDO1 with an EC50 of 1.24 nM. We also detected elevated microglial cytoplasmic labile iron in N171-82Q HD mice, an increase that is consistent with the cellular location of IDO. We further demonstrated that neonatal iron supplementation, a model for studying the role of iron in neurodegeneration, activates IDO directly in the mouse brain and promotes neurodegeneration in HD mice. Kynurenine pathway metabolites were also modified in HD and by iron supplementation in wild-type mice. These findings indicate that iron dysregulation contributes to the activation of microglia and the kynurenine pathway in a mouse model of HD.

neuroscience↗

bioRxiv2019

Mutant huntingtin protein alters the response of microglial cells to inflammatory stimuli

Huntingtons disease (HD) is a progressive neurodegenerative disease that affects the striatum and cerebral cortex. It is caused by a dominant CAG trinucleotide expansion in exon 1 of the HTT gene. Mutant huntingtin protein (mHtt) is expressed in neurons and immune cells. HD patients demonstrate altered blood cytokine profiles and altered responses of peripheral immune cells to inflammatory stimuli. However, the effects of mHtt on microglial immune responses are not fully understood. Herein we discuss the current understanding of how mHtt alters microglial inflammatory responses. Using lentivirus, we expressed the N171 N-terminal fragment of wild-type or mhtt containing 18 and 82 glutamine repeats in cultured EOC-20 microglial cells. We then measured responses to lipopolysaccharide or interleukin-6. Mutant huntingtin-expressing microglial cells produced less interleukin-6 and nitric oxide in response to lipopolysaccharide stimulation than wild-type huntingtin-expressing cells. However, mHtt-expressing microglia stimulated with interleukin-6 produced more nitric oxide than wild-type cells. Mutant huntingtin-expressing cells had higher basal NF-{kappa}B and further elevations of NF-{kappa}B after interleukin-6 but not lipopolysaccharide stimulation. Thus we demonstrate the potential of mHtt to dampen responses to lipopolysaccharide but potentiate responses to interleukin-6. This work adds to the emerging understanding that mHtt alters not only baseline status of cells but may also result in altered immune responses dependent on the nature of the inflammatory stimuli. We also present our perspective that in human HD the extent of inflammation may depend, in part, on altered responses to varied inflammatory stimuli including environmental factors such as infection.

neuroscience↗

bioRxiv2019

The IL-12 and IL-23-Dependent NK Cell Response is Essential For Protective Immunity Against Secondary Toxoplasma gondii Infection.

Natural Killer (NK) cells can develop memory-like features and contribute to long-term immunity in mice and humans. NK cells are critical for protection against acute T. gondii infection. However, whether they contribute to long-term immunity in response to this parasite is unknown. We used a vaccine challenge model of parasite infection to address this question and to define the mechanism by which NK cells are activated during secondary parasite infection. We found NK cells were required for control of secondary infection. NK cells increased in number at the infection site, became cytotoxic and produced IFN{gamma}. Adoptive transfer and NK-cell fate mapping revealed that T. gondii-experienced NK cells were not intrinsically different from naive NK cells with respect to their long-term persistence and ability to protect. Thus, they did not develop memory-like characteristics. Instead, a cell-extrinsic mechanism may control protective NK-cell responses during secondary infection. To test the involvement of a cell-extrinsic mechanism, we used anti-IL-12p70 and IL-12p35-/- mice and found that the secondary NK-cell response was not fully dependent on IL-12. IL-23 depletion with anti-IL-23p19 in vivo significantly reduced the secondary NK-cell response, suggesting that both IL-12 and IL-23 were involved. Anti-IL-12p40 treatment, which blocks both IL-12 and IL-23, eliminated the protective secondary NK-cell response, supporting this hypothesis. Our results define a previously unknown protective role for NK cells during secondary T. gondii infection that is dependent on IL-12 and IL-23.

immunology↗