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Thesis
Peer Reviewed

Exploration of Endothelial Cell Directed Innate Immunity in Leprosy

Kibbie, Jon J.
Advisor(s): Modlin, Robert L

UCLA Electronic Theses and Dissertations (2013)

As an initial point of contact with circulating innate immune precursor cells, the endothelium is poised to deliver instructive signals that influence innate immune cell activation and differentiation. In an attempt to study the endothelial innate immune interaction during an inflammatory state we developed a novel bioassay that identified activated endothelium by its capacity to trigger macrophage inflammatory protein 1 beta (MIP1b from primary monocytes. After screening a small molecule library consisting of 642 compounds, we identified two structurally unique chemical families that were able to specifically activate the endothelium. Structure-function analysis combined with transcriptional profiling identified inflammatory gene networks induced exclusively by the active compounds and allowed us to further identify important regulators of endothelial activation.

With the discovery of these unique endothelial activators we sought to further characterize the CD209 positive macrophage populations arising from this interaction. As seen in human leprosy, a stark spatial distribution of CD209 positive macrophage (MF) subsets is

linked to the fate of the host and pathogen. We recapitulated divergent CD209 positive MF subsets through primary cell co-culture phenotypic screens, identifying perturbations that licensed the endothelial microenvironment to skew monocytes towards the CD209 positive and CD163 negative MF; subset that is equipped for host defense. Transcriptional profiling of endothelial cells polarized by these structurally diverse activators revealed a subset of mutually regulated genes, and integration with the transcriptome profiles from leprosy lesions led to the discovery that jagged1 (JAG1) expression strongly correlates with the spatial distribution of CD209 positive MF; subsets at the site of disease. These findings suggest that soluble JAG1 may facilitate antimycobacterial human innate immune responses.

Cover page: Exploration of Endothelial Cell Directed Innate Immunity in Leprosy

Article
Peer Reviewed

Jagged1 Instructs Macrophage Differentiation in Leprosy.

UCLA Previously Published Works (2016)

As circulating monocytes enter the site of disease, the local microenvironment instructs their differentiation into tissue macrophages (MΦ). To identify mechanisms that regulate MΦ differentiation, we studied human leprosy as a model, since M1-type antimicrobial MΦ predominate in lesions in the self-limited form, whereas M2-type phagocytic MΦ are characteristic of the lesions in the progressive form. Using a heterotypic co-culture model, we found that unstimulated endothelial cells (EC) trigger monocytes to become M2 MΦ. However, biochemical screens identified that IFN-γ and two families of small molecules activated EC to induce monocytes to differentiate into M1 MΦ. The gene expression profiles induced in these activated EC, when overlapped with the transcriptomes of human leprosy lesions, identified Jagged1 (JAG1) as a potential regulator of MΦ differentiation. JAG1 protein was preferentially expressed in the lesions from the self-limited form of leprosy, and localized to the vascular endothelium. The ability of activated EC to induce M1 MΦ was JAG1-dependent and the addition of JAG1 to quiescent EC facilitated monocyte differentiation into M1 MΦ with antimicrobial activity against M. leprae. Our findings indicate a potential role for the IFN-γ-JAG1 axis in instructing MΦ differentiation as part of the host defense response at the site of disease in human leprosy.

Cover page: Jagged1 Instructs Macrophage Differentiation in Leprosy.

Article
Peer Reviewed

Low abundance of colonic butyrate-producing bacteria in HIV infection is associated with microbial translocation and immune activation.

UC San Diego Previously Published Works (2017)

Objective

Gut microbial translocation is a major driving force behind chronic immune activation during HIV-1 infection. HIV-1-related intestinal dysbiosis, including increases in mucosa-associated pathobionts, may influence microbial translocation and contribute to mucosal and systemic inflammation. Thus, it is critical to understand the mechanisms by which gut microbes and their metabolic products, such as butyrate, influence immune cell function during HIV-1 infection.

Design

A cross-sectional study was performed to compare the relative abundance of butyrate-producing bacterial (BPB) species in colonic biopsies and stool of untreated, chronic HIV-1-infected (n = 18) and HIV-1-uninfected (n = 14) study participants. The effect of exogenously added butyrate on gut T-cell activation and HIV-1 infection was evaluated using an ex-vivo human intestinal cell culture model.

Methods

Species were identified in 16S ribosomal RNA sequence datasets. Ex-vivo isolated lamina propria mononuclear cells were infected with C-C chemokine receptor type 5-tropic HIV-1Bal, cultured with enteric gram-negative bacteria and a range of butyrate doses, and lamina propria T-cell activation and HIV-1 infection levels measured.

Results

Relative abundance of total BPB and specifically of Roseburia intestinalis, were lower in colonic mucosa of HIV-1-infected versus HIV-1-uninfected individuals. In HIV-1-infected study participants, R. intestinalis relative abundance inversely correlated with systemic indicators of microbial translocation, immune activation, and vascular inflammation. Exogenous butyrate suppressed enteric gram-negative bacteria-driven lamina propria T-cell activation and HIV-1 infection levels in vitro.

Conclusion

Reductions in mucosal butyrate from diminished colonic BPB may exacerbate pathobiont-driven gut T-cell activation and HIV replication, thereby contributing to HIV-associated mucosal pathogenesis.

Article
Peer Reviewed

Low abundance of colonic butyrate-producing bacteria in HIV infection is associated with microbial translocation and immune activation