Biology subjects

Alvarez, C. A.

Publications and source records attributed to Alvarez, C. A..

4 recordsLinked to original sources

bioRxiv2020

Title: Acetylcholine regulates pulmonary inflammation and facilitates the transition from active immunity to tissue repair during respiratory viral infection

ABSTRACTInflammatory control is critical to recovery from respiratory viral infection. Acetylcholine (ACh) secreted from non-neuronal sources, including lymphocytes, plays an important, albeit underappreciated, role in regulating immune-mediated inflammation. This study was designed to explore the role of ACh in acute viral infection and recovery. Using the murine model of influenza A, cholinergic status in the lungs and airway was examined over the course of infection and recovery. The results showed that airway ACh remained constant through the early stage of infection and increased during the peak of the acquired immune response. As the concentration of ACh increased, cholinergic lymphocytes appeared in the airway and lungs. Cholinergic capacity was found primarily in CD4 T cells, but also in B cells and CD8 T cells. The cholinergic CD4+ T cells bound to influenza-specific tetramers at the same frequency as their conventional (i.e., non-cholinergic) counterparts. In addition, they were retained in the lungs throughout the recovery phase and could still be detected in the resident memory regions of the lung up to two months after infection. Histologically, cholinergic lymphocytes were found in direct physical contact with activated macrophages throughout the lung. When ACh production was inhibited, mice exhibited increased tissue inflammation, altered lung architecture, and delayed recovery. Together, these findings point to a previously unrecognized role for ACh in the transition from active immunity to recovery and pulmonary repair following respiratory viral infection.View Full Text

immunology↗

bioRxiv2020

An ex vivo model of Toxoplasma recrudescence

Toxoplasma has been a useful parasite model for decades because it is relatively easy to genetically modify and culture, however, attempts to generate and study the recrudescence of tissue cysts have come up short with lab-adapted strains generating low numbers of tissue cysts in vivo. Here we have established a new model of Toxoplasma recrudescence using bradyzoites from an unadapted Type II ME49 strain (ME49EW) isolated from murine brain tissue. Ex vivo bradyzoite infection of fibroblasts and astrocytes produced sequential tachyzoite growth stages; a fast-growing stage was followed by formation of a slower-growing stage. In astrocytes, but not in fibroblasts, bradyzoites also initiated a second recrudescent pathway involving bradyzoite to bradyzoite replication. Intraperitoneal infections of mice with either bradyzoites or the fast-growing tachyzoite stage efficiently disseminated to brain tissue leading to high numbers of tissue cysts, while infections with the slow-growing tachyzoite stage were largely retained in the peritoneum. Poor infection and cyst formation of slow-growing tachyzoites was reversible by serial tissue cyst passage, while the poor tissue cyst formation of lab-adapted tachyzoites was not reversible by these approaches. To distinguish strain developmental competency, we identified Toxoplasma genes highly expressed in ME49EW in vivo tissue cysts and developed a qPCR approach that differentiates immature from mature bradyzoites. In summary, the results presented describe a new ex vivo bradyzoite recrudescence model that fully captures the growth and developmental processes during toxoplasmosis reactivation in vivo opening the door to the further study of these important features of the Toxoplasma intermediate life cycle.

microbiology↗

bioRxiv2020

Integration of IL-2 and IL-4 Signals Coordinates Divergent Regulatory T cell Responses and Drives Therapeutic Efficacy

Cells exist within complex milieus of communicating factors, such as cytokines, that combine to generate context-specific responses, yet nearly all knowledge about the function of each cytokine and the signaling propagated downstream of their recognition is based upon the response to individual cytokines. Here, we found that regulatory T cells (Tregs) integrate concurrent signaling initiated by IL-2 and IL-4 to generate a response divergent from the sum of the two pathways in isolation. IL-4 stimulation of STAT6 phosphorylation was blocked by IL-2, while IL-2 and IL-4 synergized to enhance STAT5 phosphorylation, IL-10 production, and the selective proliferation of IL-10-producing Tregs, leading to increased inhibition of conventional T cell activation and the reversal of asthma and multiple sclerosis in mice. These data define a mechanism of combinatorial cytokine signaling and lay the foundation upon which to better understand the origins of cytokine pleiotropy while informing improved the clinical use of cytokines. Impact StatementSimultaneous cytokine signaling results in unexpected transcription factor changes that fuel a cellular response divergent from the sum of each cytokine alone.

biochemistry↗

bioRxiv2017

A checkpoint roadmap for the complex cell division of Apicomplexa parasites

The unusual cell cycles of Apicomplexa parasites are remarkably flexible with the ability to complete cytokinesis and karyokinesis coordinately or postpone cytokinesis for several rounds of chromosome replication are well recognized. Despite this surprising biology, the molecular machinery required to achieve this flexibility is largely unknown. In this study, we provide comprehensive experimental evidence that apicomplexan parasites utilize multiple Cdk-related kinases (Crks) to coordinate cell division. We determined that Toxoplasma gondii encodes seven atypical P-, H-, Y- and L- type cyclins and ten Crks to regulate cellular processes. We generated and analyzed conditional tet-OFF mutants for seven TgCrks and four TgCyclins that are expressed in the tachyzoite stage. These experiments demonstrated that TgCrk1, TgCrk2, TgCrk4 and TgCrk6, were required or essential for tachyzoite growth revealing a remarkable number of Crk factors that are necessary for parasite replication. G1 phase arrest resulted from the loss of cytoplasmic TgCrk2 that interacted with a P-type cyclin demonstrating that an atypical mechanism controls half the T. gondii cell cycle. We showed that T. gondii employs at least three TgCrks to complete mitosis. Novel kinases, TgCrk6 and TgCrk4 were required for spindle function and centrosome duplication, respectively, while TgCrk1 and its partner TgCycL were essential for daughter bud assembly. Intriguingly, mitotic kinases TgCrk4 and TgCrk6 did not interact with any cyclin tested and were instead dynamically expressed during mitosis indicating they may not require a cyclin timing mechanism. Altogether, our findings demonstrate that apicomplexan parasites utilize distinctive and complex mechanisms to coordinate their novel replicative cycles.

cell biology↗