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Introducción: La actual pandemia ha desafiado a los sistemas de salud en todo el mundo, evidenciado cómo las inequidades sociales determinan el curso y desenlace de la enfermedad por SARS-CoV-2. El presente artículo presenta datos epidemiológicos, como antecedentes para plantear la existencia de una sindemia en la actual crisis sanitaria que atraviesa Chile. Materiales y métodos: La metodología de recolección de información se basó en la estrategia de búsqueda por bola de nieve de tipo no discriminatorio exponencial, donde se seleccionaron tres términos de búsqueda clave, a partir de los cuales se desarrolló la investigación; Los términos fueron: COVID-19, determinantes sociales de la salud y multimorbilidad. Se buscaron datos estadísticos acerca de los resultados en salud de personas con multimorbilidad, durante la pandemia por SARS-Cov-2, así como las diferencias en cuanto a incidencia y mortalidad según distintos contextos sociales. Se utilizaron los motores de búsqueda Google, Google Scholar y SciELO. Resultados: Se identifcaron relaciones de vulnerabilidad sindémica, asociadas a peores resultados de salud determinando el curso y resultado de la enfermedad por COVID-19. Discusión: Los datos presentados permiten observar cómo ha afectado la enfermedad por COVID-19 en distintos grupos poblacionales, donde los determinantes sociales de la salud cumplen un rol fundamental. Conclusiones: Existen los sufcientes antecedentes para plantear una relación sindémica entre COVID-19, multimorbilidad y determinantes sociales en Chile. Los resultados de esta investigación refuerzan el planteamiento de que la salud pública se debe construir con un enfoque integrador, transdisciplinario e intersectorial.

Mesenteric lymph nodes (mLNs) are sentinel sites of enteral immunosurveillance and immune homeostasis. Immune cells from the gastrointestinal tract (GIT) are constantly recruited to the mLNs in steady-state and under inflammatory conditions resulting in the induction of tolerance and immune cells activation, respectively. Surgical dissection and transplantation of lymph nodes (LN) is a technique that has supported seminal work to study LN function and is useful to investigate resident stromal and endothelial cell biology and their cellular interactions in experimental disease models. Here, we provide a detailed protocol of syngeneic mLN transplantation and report assays to analyze effective mLN engraftment in congenic recipients. Transplanted mLNs allow to study T cell activation and proliferation in preclinical mouse models. Donor mLNs proved viable and functional after surgical transplantation and regenerated blood and lymphatic vessels. Immune cells from the host completely colonized the transplanted mLNs within 7-8 weeks after the surgical intervention. After allogeneic hematopoietic cell transplantation (allo-HCT), adoptively transferred allogeneic CD4+ T cells from FVB/N (H-2q) mice homed to the transplanted mLNs in C57BL/6 (H-2b) recipients during the initiation phase of acute graft-versus-host disease (aGvHD). These CD4+ T cells retained full proliferative capacity and upregulated effector and gut homing molecules comparable to those in mLNs from unmanipulated wild-type recipients. Wild type mLNs transplanted into MHCII deficient syngeneic hosts sufficed to activate alloreactive T cells upon allogeneic hematopoietic cell transplantation, even in the absence of MHCII+ CD11c+ myeloid cells. These data support that orthotopically transplanted mLNs maintain physiological functions after transplantation. The technique of LN transplantation can be applied to study migratory and resident cell compartment interactions in mLNs as well as immune reactions from and to the gut under inflammatory and non-inflammatory conditions.

Allogeneic T cell priming is considered as an essential event determining the outcome of allogeneic hematopoietic stem cell transplantation (allo-HCT), ideally triggering anti-leukemic responses (GvL effect) or, at worst, causing life-threatening acute graft-versus-host disease (aGvHD). During aGvHD initiation, alloreactive T cells are activated by host antigen presenting cells (APCs), rapidly expand and subsequently exert tissue damage. Recently, it was discovered that in absence of host hematopoietic APCs, aGvHD cannot be prevented, suggesting a crucial role of non-hematopoietic APCs for priming alloreactive T cells (Toubai et al., Blood 2012, Li et al., J Immunol. 2012, Koyama et al., Nat Med 2012). However, the exact location and identity of host non-hematopoietic APCs triggering alloreactive T cell responses remains controversial and needs to be proven in vivo. Fibroblastic reticular cells (FRCs) have shown to provide the crucial delta-like notch ligand to alloreactive T cells (Chung et al., JCI 2017) in aGvHD, therefore we investigated the role of FRCs MHC class II in aGvHD and their potential role as non-hematopoietic APCs in MHC class II dependent manner. In vitro cultured FRCs cell line as well as FRCs from lethally irradiated mice upregulate MHCII and co-stimulatory molecules. Moreover, FACS sorted FRCs (CD45-CD24-CD31-gp38+) were able to process DQ-OVA via MHC class II machinery, indicating that FRCs have the potential to activate CD4+ T cells. Employing allo-HCT mouse models in combination with flow cytometry and advanced microscopy techniques, we explored early alloreactive T cells activation initially in a myeloablatively conditioned MHC major mismatch allo-HCT setting (FVB/NàC57Bl/6). We generated MHCIIΔCcl19 mice with a Ccl19-intrinsic deletion of MHC class II on all Ccl19 expressing reticular lineage cells by crossing mice with floxed H2-Ab1 gene (H2-Ab1fl) with a mouse expressing Cre recombinase under the control of the Ccl19 promoter (Ccl19Cre). On day+3 after allo-HCT, CD4+ T cells activation (CD44 and CD25 expression) and proliferation (Ki67 expression and CFSE dilution) did not differ in the MHCIIΔCcl19 mice from H2-Ab1fl wildtype littermates. To further elucidate FRCs MHC class II in aGvHD milieu, we utilized iFABP-tOVA transgenic model in which OVA is expressed by intestinal epithelial cells as well as ectopically by FRCs of the lymphoid organs. OT-II cells transferred from RagΔ background mice failed to proliferate in the mLNs of lethally irradiated iFABP-tOVA, whereas excessive proliferation was observed in CD11c.DOG mice (where OVA is presented by CD11c-expressing cells). Taken together these results indicate that MHCII on FRCs does not play a role in direct antigen presentation and CD4+ T cell activation. Next, we asked whether MHCII on FRCs influences alloreactivity of CD4+ T cells in the symptomatic phase of aGvHD. Indeed, in MHCIIΔCcl19 mice, CD4+ T cells expressed higher levels of effector molecules: CD44 and CD127 as well as the proliferation marker Ki67 on day +30 of allo-HCT. Furthermore, the proportion of donor CD90.1+CD4+FoxP3+ regulatory T cells (Tregs) were reduced in MHCIIΔCcl19 mice as compared to H2-Ab1fl wild-type littermates. This led to overall poor survival of MHCIIΔCcl19 mice by day+60 after allo-HCT. At this time point in MHCIIΔCcl19 mice CD4+ T cells displayed higher levels of CD44, CD127 and Ki67 and down-regulated PD-1 and Lag3. To further elucidate the effect of FRCs MHC class II on CD4+FoxP3+ donor Tregs, we transplanted CD90.1+CD4+CD25hi Tregs, TCD BM from FVB mice along with naïve luc+ CD90.1+CD4+ T cells from FVB.L2G85 mice. Tregs protected against aGvHD in H2-Ab1fl littermate controls whereas Tregs could not protect MHCIIΔCcl19 recipients rendering them susceptible to aGvHD and to poor overall survival. Conclusively, these results indicate for the first time that MHC class II on FRCs assists to maintain donor Tregs in the SLOs after allo-HCT. Conclusively, we propose a model in which FRCs promote T cell alloreactivity by providing notch ligands (Chung et al., JCI 2017) in the initiation phase and mitigate aGvHD by maintenance of Tregs via MHC class II in the aGvHD-effector phase. Disclosures Einsele: Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau; Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau; GlaxoSmithKline: Honoraria, Research Funding, Speakers Bureau.

Allogeneic T cell priming is considered as an essential event determining the outcome of allogeneic hematopoietic stem cell transplantation (allo-HCT), ideally triggering anti-leukemic responses (GvL effect) or, at worst, causing life-threatening acute graft-versus-host disease (aGvHD). During acute GvHD initiation, alloreactive T cells are activated by host antigen presenting cells (APCs), rapidly expand and subsequently exert tissue damage. Recently, it was discovered that absence of host hematopoietic APCs does not prevent acute GvHD, suggesting a crucial role of non-hematopoietic APCs for priming alloreactive T cells (Toubai et al., Blood 2012, Li et al., J Immunol. 2012). Furthermore, it was even suggested that in the absence of professional APCs allogeneic CD4+ T cells can be activated in the lamina propria by MHC class II expressing myofibroblasts (Koyama et al., Nat Med 2012). As exact location and identity of host non-hematopoietic APCs triggering alloreactive T cell responses are essential to dissect the priming of GvHD-inducing vs. GvL-mediating allogeneic T cells, we investigated the role of lymph node stromal cells (LNSCs) in the initiation phase of aGvHD and their potential role as non-hematopoietic APCs. Employing allo-HCT mouse models in combination with flow cytometry and advanced microscopy techniques, we explored early alloreactive T cells activation first in a myeloablatively conditioned MHC major mismatch allo-HCT setting (FVB→B6). Under these conditions, CD4+ and CD8+ T cells activation and proliferation occurred exclusively in secondary lymphoid organs (SLOs) and not in the intestinal lamina propria early after allo-HCT within the first three days after allo-HCT. To study non-hematopoietic antigen presentation early after allo-HCT, we generated bone marrow B6.MHCIIΔ/Δ→B6.WT chimeras that lacked MHC II expression in the host hematopoietic compartment. Subsequent allo-HCT of these chimeras revealed activation and expansion of allogenic donor CD4+ T-cells exclusively in SLOs and not the lamina propria in the first three days after transplantation. Next, we generated recipient mice that selectively lacked MHCII expression either in CD11c expressing cells or under the control of the Vav1-promoter in all hematopoietic cells. In both type of recipients, allogenic donor CD4+ T-cells were activated within 3 days after allo-HCT in SLOs and no other tissues. After irradiation of B6.WT mice we observed LNSCs upregulate co-stimulatory receptors early after irradiation (24 and 72 hours), in vitro and in vivo suggesting that they may act as active non-hematopoietic APCs. Next, we performed mixed lymphocyte reactions (MLRs) of irradiated APCs derived from TgVav1-Cre+MHCIIΔ/Δmice with alloreactive CD4+ T cells from FVB mice. Here, we observed in the total absence of hematopoietic MHCII antigen presentation reduced but still pronounced activation of alloreactive CD4+ T cells. Therefore, in these transgenic allo-HCT models, hematopoietic cells in the SLOs were dispensable for alloreactive CD4+ T cell activation in the initiation phase of aGvHD. To ascertain that SLOs are the exclusive priming sites of alloreactive CD4+ T cells, we transplanted mesenteric lymph nodes (mLNs) from a B6.CD11c.DTR mice, depleted of CD11c+ cells into B6.MHCIIΔ/Δmice. After successful engraftment of donor mLNs in these mice, allo-HCT revealed these as unique priming sites in MHCII deficient hosts for alloreactive CD4+ T cells, which differentiated into CD44hiCD62Llow effector T cells that were detectable in the transplanted mLNs. Conclusively, these results indicate that specialized non-hematopoietic lymph node stromal cells prime alloreactive CD4+ T cell within the SLOs early after allo-HCT. Pinpointing the molecular pathways in these non-hematopoietic APCs within SLOs that trigger alloreactive T cell responses may prove fruitful for selective therapeutic intervention after allo-HCT. Disclosures No relevant conflicts of interest to declare.

An enantioselective Overman 3,3-sigmatropic rearrangement on a quinuclidine skeleton was developed for the pilot-plant synthesis of a glycine transporter 1 inhibitor. The first stereocenter was produced by a Ru-catalyzed asymmetric transfer hydrogenation process followed by chirality transfer using the Overman rearrangement. The second stereocenter was generated by a diastereoselective hydrogenation reaction.

Although emerging data support the utility of real-time three-dimensional echocardiography (RT3DE) during dobutamine stress testing, the feasibility of performing contrast enhanced RT3DE during exercise treadmill stress has not been explored. Two-dimensional (2D) and three-dimensional (3D) acquisition were performed in 39 patients at rest and peak exercise. Contrast was used in 29 patients (74%). Reconstruction was performed manually by generating short axis cut planes at the base, mid-ventricle and apex, and automatically by generating 9 short axis slices. Three-dimensional acquisition was feasible during rest and stress regardless of the use of contrast. Time to acquire stress images was reduced using 3D (35.2±17.9 s) as compared to 2D acquisition (51.6±14.7 s; P less then 0.05). Using a 17-segment model, of all 663 segments, 588 resting (88.6%) and 563 stress segments (84.9%) were adequately visualized using manually reconstructed 3D data, compared with 618 resting (93.2%) and 606 stress segments (91.4%) using 2D data (P rest=0.06; P stress=0.07). We concluded that contrast enhanced RT3DE is feasible during treadmill stress echocardiography.

Objective: To assess the relative contribution of each myocardial segment to global systolic function during stress using real time three-dimensional echocardiography (RT3DE). Background: During stress, global augmentation in contractility results in an increased stroke volume. The relative contribution of each myocardial segment to these volumetric changes is unknown. Methods: Full volume was acquired using RT3DE at rest and following peak exercise in 22 patients who had no ischemia and no systolic dyssynchrony on two-dimensional (2D) stress echocardiography. The following were calculated at rest and peak stress: end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), relative SV, and relative EF. Results: With stress, an increase in global EDV from 90.8 to 101.1 ml (P < 0.001), SV from 59 to 78.4 ml (P = 0.01), and EF from 65.6 to 78.4% (P = 0.001) was observed. ESV decreased from 31.8 to 22.7 ml (P < 0.001). Segmental analysis revealed significantly higher SV, relative SV, and relative EF for the basal anterior, basal anterolateral, and basal inferolateral segments compared with the apical septum and apical inferior segments at both rest and stress (P < 0.001). The SV, relative SV, and relative EF increased significantly from apex to mid to base at both rest and stress (P < 0.001). Conclusions: The relative volumetric contribution of each myocardial segment to global left ventricular systolic function at rest and stress is not uniform. The basal segments contribute more than the mid and apical segments. Specifically, the basal anterior, basal anterolateral, and basal inferolateral segments contribute the most to augmentation of left ventricular systolic function with exercise. (ECHOCARDIOGRAPHY 2010;27:167-173)