B cells are capable of independently eliciting rapid reactivation of encephalitogenic CD4 T cells in a murine model of multiple sclerosis

<div><p>Recent success with B cell depletion therapies has revitalized efforts to understand the pathogenic role of B cells in Multiple Sclerosis (MS). Using the adoptive transfer system of experimental autoimmune encephalomyelitis (EAE), a murine model of MS, we have previously shown that mice in which B cells are the only MHCII-expressing antigen presenting cell (APC) are susceptible to EAE. However, a reproducible delay in the day of onset of disease driven by exclusive B cell antigen presentation suggests that B cells require optimal conditions to function as APCs in EAE. In this study, we utilize an <i>in vivo</i> genetic system to conditionally and temporally regulate expression of MHCII to test the hypothesis that B cell APCs mediate attenuated and delayed neuroinflammatory T cell responses during EAE. Remarkably, induction of MHCII on B cells following the transfer of encephalitogenic CD4 T cells induced a rapid and robust form of EAE, while no change in the time to disease onset occurred for recipient mice in which MHCII is induced on a normal complement of APC subsets. Changes in CD4 T cell activation over time did not account for more rapid onset of EAE symptoms in this new B cell-mediated EAE model. Our system represents a novel model to study how the timing of pathogenic cognate interactions between lymphocytes facilitates the development of autoimmune attacks within the CNS.</p></div

IL-1-induced Bhlhe40 identifies pathogenic T helper cells in a model of autoimmune neuroinflammation

The features that define autoreactive T helper (Th) cell pathogenicity remain obscure. We have previously shown that Th cells require the transcription factor Bhlhe40 to mediate experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Here, using Bhlhe40 reporter mice and analyzing both polyclonal and TCR transgenic Th cells, we found that Bhlhe40 expression was heterogeneous after EAE induction, with Bhlhe40-expressing cells displaying marked production of IFN-γ, IL-17A, and granulocyte-macrophage colony-stimulating factor. In adoptive transfer EAE models, Bhlhe40-deficient Th1 and Th17 cells were both nonencephalitogenic. Pertussis toxin (PTX), a classical co-adjuvant for actively induced EAE, promoted IL-1β production by myeloid cells in the draining lymph node and served as a strong stimulus for Bhlhe40 expression in Th cells. Furthermore, PTX co-adjuvanticity was Bhlhe40 dependent. IL-1β induced Bhlhe40 expression in polarized Th17 cells, and Bhlhe40-expressing cells exhibited an encephalitogenic transcriptional signature. In vivo, IL-1R signaling was required for full Bhlhe40 expression by Th cells after immunization. Overall, we demonstrate that Bhlhe40 expression identifies encephalitogenic Th cells and defines a PTX–IL-1–Bhlhe40 pathway active in EAE

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

B cells are capable of independently eliciting rapid reactivation of encephalitogenic CD4 T cells in a murine model of multiple sclerosis - Fig 5

<p><b>Flow cytometric analysis of lymphocytes from brains (left) and spinal cords (right).</b> (A) Mean ± SEM frequency of B cells and donor CD4 T cells as a percent of total mononuclear cells in the CNS of mice at week 1 (circles), week 2 (squares), or week 3 (triangles) post CD4 T cell transfer. Data is pooled from CD20-B^MHCIIxIgH^MOG mice, UBC^MHCII mice, and IAß^bstop^flox/floxxIgH^MOG (Cre^-) littermate controls from 9 different experiments with n = 3–5 mice at each time point prior to Tam treatment. Significance determined by Kruskal-Wallis test and Dunn’s correction for multiple comparisons. (B-D) Mean ± SEM frequency of B cells and donor CD4 T cells as a percent of total mononuclear cells in the brains (left) and spinal cords (right) harvested UBC^MHCII (red squares) and CD20-B^MHCIIxIgH^MOG (blue circles) mice approximately three days post EAE onset when mice were treated with Tam at (B) week 1, (C) week 2, or (D) week 3 post encephalitogenic CD4 T cell transfer. Data is pooled from 9 different experiments with n = 1–5 mice per genotype at each time point evaluated. Significance determined by Mann-Whitney test with two-tailed p value.</p

B cells are not sufficient APCs to support spontaneous EAE or optic neuritis.

<p>B cells are not sufficient APCs to support spontaneous EAE or optic neuritis.</p

Accelerated EAE is not induced by CD4 T cells harvested from MHCII-deficient hosts.

<p>Accelerated EAE is not induced by CD4 T cells harvested from MHCII-deficient hosts.</p

Tam-inducible MHCII expression models recapitulate WT and B-cell mediated adoptive transfer EAE models.

<p>(A) Mean ± SEM EAE scores recorded for CD20-B^MHCIIxIgH^MOG (blue circles), and UBC^MHCII (red squares) mice treated with Tam by oral gavage and WT (black squares), CD19-B^MHCIIxIgH^MOG (grey circles), treated with corn oil vehicle by oral gavage once, three days prior to receiving 5x10⁶ encephalitogenic CD4 T cells. Data is representative of three independent experiments with n = 3–5 mice per genotype. (B) Day of EAE onset post cell transfer for WT (black squares), UBC^MHCII (red squares), CD19-B^MHCIIxIgH^MOG (grey circles) treated with corn oil 72 hours prior to CD4 T cell transfer and CD20-B^MHCIIxIgH^MOG (blue circles) recipient mice treated with Tam 72 hours prior to CD4 T cell transfer. Graph shows mean day of onset ± SEM from two pooled, independent experiments with n = 2–4 mice per genotype. Unpaired t test performed to compare day of onset between WT and CD19-B^MHCIIxIgH^MOG mice. (C) Mice were treated with Tam 72 hours prior to CD4 T cell transfer. Time to EAE onset for WT (black) and UBC^MHCII (red) mice is not significantly different by log-rank test (p = 0.107). Time to EAE onset for CD19-B^MHCIIxIgH^MOG (grey), and CD20-B^MHCIIxIgH^MOG (blue) mice is not significantly different by log-rank test (p = 0.481). Incidence curves generated from two pooled, independent experiments with n = 2–4 mice per genotype.</p

Inflammation and demyelination is not evident in spinal cords of encephalitic CD4 T cell recipients prior to Tam administration.

<p>(A) Representative spinal cord sections from recipients of encephalitogenic CD4 T cells (n = 5, CD20-B^MHCIIxIgH^MOG mice; n = 6, UBC^MHCII mice) were stained with Luxol Fast Blue, scale bar = 100um; all images generated from 10x magnification. (A) Spinal cords from CD20-B^MHCIIxIgH^MOG mice harvested three weeks after T cell transfer and before Tam administration (left). CD20-B^MHCIIxIgH^MOG mice treated with Tam three weeks after T cell transfer (middle) and harvested three days post EAE onset. UBC^MHCII mice treated with Tam three weeks after T cell transfer (right) and harvested three days post EAE onset. (B) Representative spinal cord sections from recipients of encephalitogenic CD4 T cells (at least mice 5 per genotype) were stained with antibodies to detect MOG, scale bar = 100um. Spinal cords from CD20-B^MHCIIxIgH^MOG mice (top left) and UBC^MHCII mice (bottom left) harvested three weeks after T cell transfer and before Tam administration. CD20-B^MHCIIxIgH^MOG (top right) and UBC^MHCII (bottom right) mice treated with Tam three weeks after T cell transfer and harvested three days post EAE onset. (C) Regions from rostral to caudal sections of spinal cords from CD20-B^MHCIIxIgH^MOG (blue) and UBC^MHCII mice (red) were harvested and scored for inflammation. Graph shows mean +/- SEM inflammation scores and Kruskal-Wallis test with Dunn’s correction for multiple comparisons was applied. B.S. = brainstem; C = cervical; T = thoracic; L = lumbar. (D) Mean (SD) percent area of demyelinated white matter was quantified for thoracic spinal cord sections from CD20-B^MHCIIxIgH^MOG (blue) and UBC^MHCII (red) mice. Significance determined by Mann-Whitney test with two-tailed p value.</p