Raffaello Cimbro

Immune cell characterization heavily relies on multicolor flow cytometry to identify subpopulations based on differential expression of surface markers. Setup of a classic multicolor panel requires high-end instruments, custom labeled antibodies, and careful study design to minimize spectral overlap. We developed a multiparametric analysis to identify major human immune populations (CD4⁺ and CD8⁺ T cells, γδ T cells, B cells, NK cells and monocytes) in peripheral blood by combining seven lineage markers using only two fluorochromes. Our strategy is based on the observation that lineage markers are constantly expressed in a unique combination by each cell population. Combining this information with a careful titration of the antibodies allows investigators to record five additional markers, expanding the optical limit of most flow cytometers. Head-to-head comparison demonstrated that the vast majority of immune cell populations in peripheral blood can be characterized with comparable accuracy between our method and the classic "one fluorochrome-one marker approach", although the latter is still more precise for identifying populations such as NKT cells and γδ T cells. Combining seven markers using two fluorochromes allows for the analysis of complex immune cell populations and clinical samples on affordable 6-10 fluorochrome flow cytometers, and even on 2-3 fluorochrome field instruments in areas with limited resources. High-end instruments can also benefit from this approach by using extra fluorochromes to accomplish deeper flow cytometry analysis. This approach is also very well suited for screening several cell populations in the case of clinical samples with limited number of cells.

Flow cytometry is the primary immunological technique used to analyze multiple parameters on complex cell populations. We present a staining method that identifies major human mononuclear lymphoid and myeloid populations (CD4⁺ and CD8⁺ T cells, γδ T cells, B cells, NK cells and monocytes), using only two fluorochromes and a minimal number of cells. Our approach increases the number of markers recordable on most flow cytometers allowing for a deeper and more comprehensive immunophenotyping.

Antibodies sustain viral control: For many infected individuals, antiretroviral therapy (ART) means that an HIV-1 diagnosis is no longer a death sentence. But the virus persists in treated individuals, and complying with the intense drug regimen to keep virus loads down can be challenging for patients. Seeking an alternative, Byrareddy et al. treated ART-suppressed monkeys with antibodies targeting α4β7 integrin. When ART was halted in the antibody-treated animals, viral loads stayed undetectable, and normal CD4 T cell counts were maintained for over 9 months—and persisted—even after stopping the antibody therapy. Science , this issue p. 197

Therapeutics aimed at blocking the cannabinoid 1 (CB1) receptor for treatment of obesity resulted in significant improvements in liver function, glucose uptake and pancreatic β-cell function independent of weight loss or CB1 receptor blockade in the brain, suggesting that peripherally-acting only CB1 receptor blockers may be useful therapeutic agents. Neuropsychiatric side effects and lack of tissue specificity precluded clinical use of first-generation, centrally acting CB1 receptor blockers. In this study we specifically analyzed the potential relevance to diabetes of human CB1 receptor isoforms in extraneural tissues involved in glucose metabolism. We identified an isoform of the human CB1 receptor (CB1b) that is highly expressed in β-cells and hepatocytes but not in the brain. Importantly, CB1b shows stronger affinity for the inverse agonist JD-5037 than for rimonabant compared to CB1 full length. Most relevant to the field, CB1b is a potent regulator of adenylyl cyclase activity in peripheral metabolic tissues. CB1b blockade by JD-5037 results in stronger adenylyl cyclase activation compared to rimonabant and it is a better enhancer of insulin secretion in β-cells. We propose this isoform as a principal pharmacological target for the treatment of metabolic disorders involving glucose metabolism.

The study of neuroplasticity and molecular alterations in learned behaviors is switching from the study of whole brain regions to the study of specific sets of sparsely distributed activated neurons called neuronal ensembles that mediate learned associations. Fluorescence Activated Cell Sorting (FACS) has recently been optimized for adult rat brain tissue and allowed isolation of activated neurons using antibodies against the neuronal marker NeuN and Fos protein, a marker of strongly activated neurons. Until now, Fos-expressing neurons and other cell types were isolated from fresh tissue, which entailed long processing days and allowed very limited numbers of brain samples to be assessed after lengthy and complex behavioral procedures. Here we found that yields of Fos-expressing neurons and Fos mRNA from dorsal striatum were similar between freshly dissected tissue and tissue frozen at -80 ºC for 3 - 21 days. In addition, we confirmed the phenotype of the NeuN-positive and NeuN-negative sorted cells by assessing gene expression of neuronal (NeuN), astrocytic (GFAP), oligodendrocytic (Oligo2) and microgial (Iba1) markers, which indicates that frozen tissue can also be used for FACS isolation of glial cell types. Overall, it is possible to collect, dissect and freeze brain tissue for multiple FACS sessions. This maximizes the amount of data obtained from valuable animal subjects that have often undergone long and complex behavioral procedures.

Objective: Scleroderma patients with autoantibodies to CENPs and/or interferon‐inducible protein 16 (IFI‐16) are at increased risk of severe vascular complications. This study was undertaken to determine whether these autoantigens are enriched in cells of the vasculature.Methods: Successive stages of embryoid bodies (EBs) as well as vascular progenitors were used to evaluate the expression of scleroderma autoantigens IFI‐16 and CENP by immunoblotting. CD31 was included to mark early blood vessels. IFI‐16 and CD31 expression were defined in paraffin‐embedded skin sections from scleroderma patients and from healthy controls. IFI‐16 expression was determined by flow cytometric analysis in circulating endothelial cells (CECs) and circulating hematopoietic progenitor cells.Results: Expression of CENP‐A, IFI‐16, and CD31 was enriched in EBs on days 10 and 12 of differentiation, and particularly in cultures enriched in vascular progenitors (IFI‐16, CD31, and CENPs A and B). This pattern was distinct from that of comparator autoantigens. Immunohistochemical staining of paraffin‐embedded skin sections showed enrichment of IFI‐16 in CD31‐positive vascular endothelial cells in biopsy specimens from scleroderma patients and normal controls. Flow cytometric analysis revealed IFI‐16 expression in circulating hematopoietic progenitor cells but minimal expression in CECs.Conclusion: Our findings indicate that expression of the scleroderma autoantigens IFI‐16 and CENPs, which are associated with severe vascular disease, is increased in vascular progenitors and mature endothelial cells. High level, lineage‐enriched expression of autoantigens may explain the striking association between clinical phenotypes and the immune targeting of specific autoantigens.

Scleroderma is an antigen-driven T cell-mediated autoimmune disease. Presence of anti-topoisomerase-I antibodies is associated with pulmonary fibrosis and predicts increased mortality. Characterization of autoreactive T lymphocytes may shed light on disease pathogenesis and serve as a biomarker for disease activity. Here, we aimed to quantify and functionally characterize circulating topoisomerase I (topo-I)-specific CD4+ T cells and to define their association with presence and progression of interstitial lung disease (ILD) in patients with scleroderma. Using flow cytometry, circulating topo-I-reactive CD4+ T cells were identified by the expression of specific activation markers (CD154 and CD69) upon stimulation with purified topo-I and quantified in 27 SSc patients and 4 healthy donors (HD). Polarization of autoreactive T cells (Th1, Th2, Th17, Th1–17) was defined using surface expression of specific chemokine receptors. Presence and progression of ILD were determined using high-resolution chest CT and pulmonary function tests. Topo-I-reactive CD4+ T cells were found in all topo-I-positive patients compared to one topo-I-negative subject and no HD. Topo-I-specific CD4+ T cells exhibited a distinct Th17 polarized phenotype. Autoreactive T cells were significantly increased in subjects with evidence of ILD and were quantitatively associated with the decline of lung volumes. Topo-I-specific T cells can be reliably quantified in the peripheral blood of patients with scleroderma, exhibit a pro-inflammatory Th17 phenotype, and predict progression of ILD.

We recently identified 2 sulfated tyrosines, Tys173 and Tys177, in the second variable (V2) region of HIV-1 gp120 and shown that they play a role in stabilizing the pre-fusion conformation of the envelope trimer. The sulfated region of V2 has a high similarity with the N-terminal domain of CCR5, which also contains sulfated tyrosines and interacts with V3-loop base of gp120, suggesting a potential intramolecular interaction mode between V2 and V3. Here, we employed a tyrosine- sulfated V2-derived peptide, pV2alpha-Tys, to investigate binding to gp120 and its functional consequences. A direct interaction was observed between peptide pV2alpha-Tys and the base of V3, with Tys177 playing a dominant role. Surface plasmon resonance showed that binding of the pV2alpha-Tys is enhanced by CD4-induced conformational changes in gp120, and the effect is even more significant with a soluble trimer. Functionally, pV2alpha-Tys inhibits HIV-1 entry and fusion by preventing CCR5 utilization, with a potency comparable to that of a sulfated CCR5 N-terminal peptide, pCCR5-Tys. These studies characterize the structural and functional features of the V2–V3 intramolecular interaction, providing new leads for the design of therapeutic and vaccine strategies for the control of HIV/AIDS.

This work seeks to develop a methodology for identifying reliable biomarkers of disease activity, progression and outcome through the identification of significant associations between high-throughput flow cytometry (FC) data and interstitial lung disease (ILD) - a systemic sclerosis (SSc, or scleroderma) clinical phenotype which is the leading cause of morbidity and mortality in SSc. A specific aim of the work involves developing a clinically useful screening tool that could yield accurate assessments of disease state such as the risk or presence of SSc-ILD, the activity of lung involvement and the likelihood to respond to therapeutic intervention. Ultimately this instrument could facilitate a refined stratification of SSc patients into clinically relevant subsets at the time of diagnosis and subsequently during the course of the disease and thus help in preventing bad outcomes from disease progression or unnecessary treatment side effects.