Olga N. Malkova

Brief Report: Chikungunya Viral Arthritis in the United States: A Mimic of Seronegative Rheumatoid Arthritis

Chikungunya virus (CHIKV) is an arthritogenic mosquito‐transmitted alphavirus that spread to the Caribbean in 2013 and to the US in 2014. CHIKV‐infected patients develop inflammatory arthritis that can persist for months or years, but little is known about the rheumatologic and immunologic features of CHIKV‐related arthritis in humans, particularly as compared to rheumatoid arthritis (RA). The purpose of this study was to describe these features in a group of 10 American travelers who were nearly simultaneously infected while visiting Haiti in June 2014.

Chikungunya viral arthritis in the United States: a mimic of seronegative rheumatoid arthritis.

Chikungunya virus (CHIKV) is an arthritogenic mosquito‐transmitted alphavirus that spread to the Caribbean in 2013 and to the US in 2014. CHIKV‐infected patients develop inflammatory arthritis that can persist for months or years, but little is known about the rheumatologic and immunologic features of CHIKV‐related arthritis in humans, particularly as compared to rheumatoid arthritis (RA). The purpose of this study was to describe these features in a group of 10 American travelers who were nearly simultaneously infected while visiting Haiti in June 2014.

Cutting Edge: Human CD49e− NK Cells Are Tissue Resident in the Liver

Most knowledge on NK cells is based on studies of what are now known as conventional NK cells in the mouse spleen or human peripheral blood. However, recent studies in mice indicate the presence of tissue-resident NK cells in certain organs, such as the liver, that display different markers and transcription factor dependencies as compared with conventional NK cells. In this study, we provide evidence from cytometry by time-of-flight analysis and humanized mice indicating that human CD49e− NK cells are tissue resident in the liver. Thus, these studies indicate that tissue-resident NK cells are evolutionarily conserved in humans and mice, providing a foundation to explore their role in human disease.

Mass cytometry analysis reveals hyperactive NF Kappa B signaling in myelofibrosis and secondary acute myeloid leukemia

Myeloproliferative neoplasms (MPNs) feature a malignant clone containing the JAK2 V617F mutation, or another mutation causing dysregulated JAK2 kinase activity. The multiple disease phenotypes of MPNs, and their tendency to transform phenotypically, suggest pathophysiologic heterogeneities beyond a common phenomenon of JAK2 hyperactivation. JAK2 has the potential to activate multiple other signaling molecules, either directly through downstream effectors, or indirectly through induction of target gene expression. We have interrogated myeloproliferative signaling in myelofibrosis (MF) and secondary acute myeloid leukemia (sAML) patient samples using mass cytometry, which allows the quantitative measurement of multiple signaling molecules simultaneously at the single-cell level, in cell populations representing a nearly complete spectrum of hematopoiesis. MF and sAML malignant cells demonstrated a high prevalence of hyperactivation of the JAK-STAT, MAP kinase, PI3 kinase and NFκB signaling pathways. Constitutive NFκB signaling was evident across MF and sAML patients. A supporting gene set enrichment analysis (GSEA) of MF showed many NFκB target genes to be expressed above normal levels in MF patient CD34+ cells. NFκB inhibition suppressed colony formation from MF CD34+ cells. This study indicates that NFκB signaling contributes to human myeloproliferative disease and is abnormally activated in MF and sAML.

Analysis of Signaling Networks at the Single-Cell Level Using Mass Cytometry

Mass cytometry is a powerful technology that enables the measurement of >40 parameters at the single-cell level. The inherent spectral limitations of fluorescent flow cytometry are circumvented by the use of antibodies conjugated to metal isotope reporters, which are measured quantitatively using a CyTOF mass cytometer. The high dimensionality of mass cytometry is particularly useful for the analysis of cell signaling networks in complex biological samples. We describe here methods for cell preparation, antibody staining, data acquisition, and analysis of multidimensional data from a mass cytometry experiment.

Identification of enhanced IFN- γ signaling in polyarticular juvenile idiopathic arthritis with mass cytometry

Polyarticular juvenile idiopathic arthritis (JIA) is among the most challenging of the JIA subtypes to treat. Even with current biologic therapies, the disease remains difficult to control in a substantial subset of patients, highlighting the need for new therapies. The aim of this study was to use the high dimensionality afforded by mass cytometry with phospho-specific antibodies to delineate signaling abnormalities in immune cells from treatment-naive polyarticular JIA patients. Peripheral blood mononuclear cells were isolated from 17 treatment-naive polyarticular JIA patients, 10 of the patients after achieving clinical remission, and 19 healthy controls. Samples were stimulated for 15 minutes with IL-6 or IFN-γ and analyzed by mass cytometry. Following IFN-γ stimulation, increased STAT1 and/or STAT3 phosphorylation was observed in subsets of CD4 T cells and classical monocytes from treatment-naive patients. The enhanced IFN-γ signaling was associated with increased expression of JAK1 and SOCS1 in CD4 T cells. Furthermore, substantial heterogeneity in surface marker expression was observed among the subsets of CD4 T cells and classical monocytes with increased IFN-γ responsiveness. The identification of enhanced IFN-γ signaling in CD4 T cells and classical monocytes from treatment-naive polyarticular JIA patients provides mechanistic support for investigations into therapies that attenuate IFN-γ signaling in this disease.

High-Dimensional Analysis Delineates Myeloid and Lymphoid Compartment Remodeling during Successful Immune-Checkpoint Cancer Therapy

Although current immune-checkpoint therapy (ICT) mainly targets lymphoid cells, it is associated with a broader remodeling of the tumor micro-environment. Here, using complementary forms of high-dimensional profiling, we define differences across all hematopoietic cells from syngeneic mouse tumors during unrestrained tumor growth or effective ICT. Unbiased assessment of gene expression of tumor-infiltrating cells by single-cell RNA sequencing (scRNAseq) and longitudinal assessment of cellular protein expression by mass cytometry (CyTOF) revealed significant remodeling of both the lymphoid and myeloid intratumoral compartments. Surprisingly, we observed multiple subpopulations of monocytes/macrophages, distinguishable by the markers CD206, CX3CR1, CD1d, and iNOS, that change over time during ICT in a manner partially dependent on IFNγ. Our data support the hypothesis that this macrophage polarization/activation results from effects on circulatory monocytes and early macrophages entering tumors, rather than on pre-polarized mature intratumoral macrophages.

Brief Report: Chikungunya Viral Arthritis in the United States: A Mimic of Seronegative Rheumatoid Arthritis: CHIKUNGUNYA VIRAL ARTHRITIS MIMICS RA

Chikungunya virus (CHIKV) is an arthritogenic mosquito‐transmitted alphavirus that spread to the Caribbean in 2013 and to the US in 2014. CHIKV‐infected patients develop inflammatory arthritis that can persist for months or years, but little is known about the rheumatologic and immunologic features of CHIKV‐related arthritis in humans, particularly as compared to rheumatoid arthritis (RA). The purpose of this study was to describe these features in a group of 10 American travelers who were nearly simultaneously infected while visiting Haiti in June 2014.