Eos Promotes TH2 Differentiation by Interacting with and Propagating the Activity of STAT5

The Ikaros zinc-finger transcription factor Eos has largely been associated with sustaining the immunosuppressive functions of regulatory T cells. Paradoxically, Eos has more recently been implicated in promoting proinflammatory responses in the dysregulated setting of autoimmunity. However, the precise role of Eos in regulating the differentiation and function of effector CD4+ T cell subsets remains unclear. In this study, we find that Eos is a positive regulator of the differentiation of murine CD4+ TH2 cells, an effector population that has been implicated in both immunity against helminthic parasites and the induction of allergic asthma. Using murine in vitro TH2 polarization and an in vivo house dust mite asthma model, we find that EosKO T cells exhibit reduced expression of key TH2 transcription factors, effector cytokines, and cytokine receptors. Mechanistically, we find that the IL-2/STAT5 axis and its downstream TH2 gene targets are one of the most significantly downregulated pathways in Eos-deficient cells. Consistent with these observations, we find that Eos forms, to our knowledge, a novel complex with and supports the tyrosine phosphorylation of STAT5. Collectively, these data define a regulatory mechanism whereby Eos propagates STAT5 activity to facilitate TH2 cell differentiation.

Peritonsillar Abscess Model for Ultrasound Diagnosis Using Inexpensive Materials

Audience

This low-cost peritonsillar abscess model is intended for the education of emergency medicine and otolaryngology residents and advanced care practitioners of all training levels.

Introduction

With incidence rates as high as 124 per 100,000 in the 14-21 age range, peritonsillar abscesses (PTA) are one of the more common head and neck soft tissue infections encountered in the emergency department.1 Peritonsillar abscesses can present to the emergency department in critically ill patients with the dangers of airway compromise and further local spreading. Emergency medicine (EM) residents need practice to properly identify and to minimize procedural complications such as perforation of nearby vessels, aspiration pneumonitis, and airway compromise. A major tool used in the emergency department that can help prevent complications is the use of ultrasound, which the Accreditation Council for Graduate Medical Education (ACGME) requires residents to become proficient at.2 Historically, computed tomography (CT) scanning to diagnose along with blind drainage has been the method of choice. With a sensitivity of 95.2%, intraoral ultrasound can minimize both radiation and procedure related complications.3 The current simulators available come at significant capital expenditure and do not provide high-fidelity ultrasound experience. Here we design and implement a low-cost trainer for residents to use ultrasound to diagnose and drain a PTA.

Educational Objectives

By the end of this instructional session learners should be able to: 1) identify and discuss the indications, contraindications, and complications associated with peritonsillar abscesses, 2) properly identify and measure a PTA through ultrasound, and 3) competently perform ultrasound-guided peritonsillar abscess drainage on a simulator and remove fluid.

Educational Methods

This PTA model utilizes task trainers designed from Styrofoam wig heads. An airway was modeled using readily available wood shop tools and balloons filled with a fluid mixture containing coconut lotion, water, and fragrance beads, which were inserted into the airway. This unique mixture within the balloons creates a realistic echogenicity of an abscess with loculations. With emergency medicine clinical faculty guidance and the use of ultrasound, learners are able to identify a peritonsillar abscess and subsequently demonstrate drainage of fluid with a needle and syringe.

Research Methods

This PTA model was tested with a group of 36 emergency medicine residents. Optional, anonymous post surveys were completed by 17 residents. A 5-point Likert Scale was used to assess utility of this model.

Results

The majority of users agreed the model provides a realistic image of the disease for diagnosis by ultrasound with a score of 3.6 and felt more comfortable identifying and draining peritonsillar abscesses with scores of 3.7 and 3.6 respectively. Learners' surveys revealed the session was useful and improved their knowledge with both scoring 3.8. No critical feedback was given by learners or instructors. The efficacy of the content was assessed by evaluators observing proper ultrasound, procedure set up, and drainage of PTA.

Discussion

This inexpensive model to expose residents to proper PTA drainage was effective considering learners' high response to post-procedure survey scales. The results of our pilot implementation showed this model has utility in teaching ultrasound guided identification and drainage of PTA's. With minimal build and optimized instruction time, we can improve residents' comfort in performing this procedure and allow for important simulation experience in a safe, controlled environment.

Topics

Simulation, emergency medicine, peritonsillar abscess, otolaryngology.

Cooperative roles for Aiolos and STAT3 in TH17 differentiation

TH17 cells are a subset of T helper cells involved in mucosal immunity that are defined, in part, by their production of the proinflammatory cytokine IL-17. Dysregulated Th17 cells have been implicated in several autoimmune diseases, such as multiple sclerosis and inflammatory bowel disease. Therefore, there is substantial interest in understanding the mechanisms underlying their differentiation and function. TH17 development requires signals from IL-6 to activate STAT3, which positively regulates the expression of proinflammatory genes including Il17a and Il17f. Our recent work established that the Ikaros Zinc Finger (IkZF) transcription factor Aiolos cooperates with STAT3 to positively regulate gene expression in T follicular helper cells. Given the role of STAT3 in TH17 populations, we hypothesized that Aiolos and STAT3 may also regulate the differentiation of TH17 cells. Here, we find that Aiolos expression is significantly increased in TH17 cells as compared to other T helper cell subsets. Corroborating previously published work, we find that overexpression of Aiolos results in reduced expression of Il2, which negatively regulates the TH17 gene program. Intriguingly, we find that concurrent Aiolos and STAT3 overexpression leads to further repression of Il2, as well as increased expression of the pro-TH17 gene Il6ra. However, expression of Rorc, Il17a, and Il17f were unaffected in this system, suggesting that Aiolos and STAT3 cooperate to regulate cytokine signaling pathways in TH17 cells, rather than ROR gamma t or TH17 effector functions. Collectively, these data suggest that Aiolos and STAT3 may cooperatively regulate TH17 differentiation through a feed-forward, cytokine signaling-mediated mechanism.

Novel roles for the Ikaros zinc finger transcription factor Eos in regulating TH2 differentiation

CD4+ T cells differentiate in response to specific cytokine environments that induce the activation of STAT transcription factors and, ultimately, cell-specific gene profiles. The differentiation of TH2 cells requires the cytokines IL-4 and IL-2, which signal via the activation of STAT6 and STAT5, respectively. Interestingly, signaling via the IL-2/STAT5 axis is also required for the differentiation of the TH1 cell type. Our lab recently found that IL-2 signaling induces expression of the Ikaros Zinc Finger (IkZF) transcription factor Eos (Ikzf4) in TH1 cells, and that Eos positively regulates TH1-specific gene expression. Given the requirement for IL-2 signaling in TH2 development, we hypothesized that Eos may also play a role in TH2 differentiation. Indeed, we found that Eos expression was increased in TH2 cells at both the transcript and protein level as compared to TH0, TH1, and TFH-like cells. We also found that Eos knockdown resulted in a significant decrease in the expression of the canonical TH2 genes Il4 and Il13. When we cultured Eos-deficient cells in TH2-polarizing conditions, we similarly observed a decrease in Il4 and Il13 expression, as well as reduced expression of Il2ra and Il2rb. Eos-deficient TH2 cells also displayed decreased expression of Prdm1, the gene encoding Blimp-1, which represses the expression of alternative T helper cell gene programs in TH2 cells. Taken together, these data support a novel, positive role for Eos in the regulation of the TH2 gene program.

Highly efficient maternal-fetal Zika virus transmission in pregnant rhesus macaques

Infection with Zika virus (ZIKV) is associated with human congenital fetal anomalies. To model fetal outcomes in nonhuman primates, we administered Asian-lineage ZIKV subcutaneously to four pregnant rhesus macaques. While non-pregnant animals in a previous study contemporary with the current report clear viremia within 10-12 days, maternal viremia was prolonged in 3 of 4 pregnancies. Fetal head growth velocity in the last month of gestation determined by ultrasound assessment of head circumference was decreased in comparison with biparietal diameter and femur length within each fetus, both within normal range. ZIKV RNA was detected in tissues from all four fetuses at term cesarean section. In all pregnancies, neutrophilic infiltration was present at the maternal-fetal interface (decidua, placenta, fetal membranes), in various fetal tissues, and in fetal retina, choroid, and optic nerve (first trimester infection only). Consistent vertical transmission in this primate model may provide a platform to assess risk factors and test therapeutic interventions for interruption of fetal infection. The results may also suggest that maternal-fetal ZIKV transmission in human pregnancy may be more frequent than currently appreciated.

Heterologous Protection against Asian Zika Virus Challenge in Rhesus Macaques

BACKGROUND

Zika virus (ZIKV; Flaviviridae, Flavivirus) was declared a public health emergency of international concern by the World Health Organization (WHO) in February 2016, because of the evidence linking infection with ZIKV to neurological complications, such as Guillain-Barre Syndrome in adults and congenital birth defects including microcephaly in the developing fetus. Because development of a ZIKV vaccine is a top research priority and because the genetic and antigenic variability of many RNA viruses limits the effectiveness of vaccines, assessing whether immunity elicited against one ZIKV strain is sufficient to confer broad protection against all ZIKV strains is critical. Recently, in vitro studies demonstrated that ZIKV likely circulates as a single serotype. Here, we demonstrate that immunity elicited by African lineage ZIKV protects rhesus macaques against subsequent infection with Asian lineage ZIKV.

METHODOLOGY/PRINCIPAL FINDINGS

Using our recently developed rhesus macaque model of ZIKV infection, we report that the prototypical ZIKV strain MR766 productively infects macaques, and that immunity elicited by MR766 protects macaques against heterologous Asian ZIKV. Furthermore, using next generation deep sequencing, we found in vivo restoration of a putative N-linked glycosylation site upon replication in macaques that is absent in numerous MR766 strains that are widely being used by the research community. This reversion highlights the importance of carefully examining the sequence composition of all viral stocks as well as understanding how passage history may alter a virus from its original form.

CONCLUSIONS/SIGNIFICANCE

An effective ZIKV vaccine is needed to prevent infection-associated fetal abnormalities. Macaques whose immune responses were primed by infection with East African ZIKV were completely protected from detectable viremia when subsequently rechallenged with heterologous Asian ZIKV. Therefore, these data suggest that immunogen selection is unlikely to adversely affect the breadth of vaccine protection, i.e., any Asian ZIKV immunogen that protects against homologous challenge will likely confer protection against all other Asian ZIKV strains.

A rhesus macaque model of Asian-lineage Zika virus infection

Infection with Asian-lineage Zika virus (ZIKV) has been associated with Guillain–Barré syndrome and fetal abnormalities, but the underlying mechanisms remain poorly understood. Animal models of infection are thus urgently needed. Here we show that rhesus macaques are susceptible to infection by an Asian-lineage ZIKV closely related to strains currently circulating in the Americas. Following subcutaneous inoculation, ZIKV RNA is detected in plasma 1 day post infection (d.p.i.) in all animals (N=8, including 2 pregnant animals), and is also present in saliva, urine and cerebrospinal fluid. Non-pregnant and pregnant animals remain viremic for 21 days and for up to at least 57 days, respectively. Neutralizing antibodies are detected by 21 d.p.i. Rechallenge 10 weeks after the initial challenge results in no detectable virus replication, indicating protective immunity against homologous strains. Therefore, Asian-lineage ZIKV infection of rhesus macaques provides a relevant animal model for studying pathogenesis and evaluating potential interventions against human infection, including during pregnancy.

Animal models of infection with Zika virus (ZIKV) are urgently needed for a better understanding of pathogenesis and for testing potential therapies. Here, the authors describe infection of rhesus macaques with an Asian-lineage ZIKV strain as a relevant animal model for studying ZIKV pathogenesis.