bluuebunny/crossref_metadata_2025_split huggingface dataset:
IL-15-activated bystander CD8+ T cells contribute to host injury by NK-like cytolytic activity in acute viral hepatitis. (105.21)
Authors: Chang Dong-Yeop , Lee Hyun Woong , Kang Wonseok , Cheon Doo-Sung , Kim Hyung Joon , Shin Eui-Cheol 
Published: January 2023

Abstract
In viral infection, activation of bystander CD8+ T cells and their role have been controversial. We investigated bystander activation of CD8+ T cells and their contribution to tissue damage in acute hepatitis A (AHA), which is caused by hepatitis A virus (HAV) and manifested by severe liver injury in adults. We show bystander activation of CD8+ T cells specific to irrelevant viruses such as CMV, EBV and influenza A virus during acute necroinflammatory phase. We also demonstrate an unexpected correlation of the bystander activation to the liver injury, indicating a role of activated bystander CD8+ T cells in the liver injury. In contrast, HAV-specific T cell response was associated with viral clearance rather than the liver injury. Intriguingly, IL-15 is produced by HAV infection, and expression of IL-15 and IL-15Rα is increased in AHA. Furthermore, in vitro IL-15 treatment of healthy donors’ lymphocytes recapitulated the activated phenotype of the bystander CD8+ T cells observed in AHA. CD8+ T cells activated in vitro by IL-15 or obtained from the AHA liver exerted NK-like cytolytic activity triggered by NKG2D and/or NKp30 without TCR engagement. In addition, hepatocytes of the AHA liver over-expressed NKG2D ligands, and therefore could be cytolytic targets. Taken together, we report here a human viral disease in which bystander CD8+ T cells are activated by IL-15 and contribute to tissue damage by NK-like cytolytic activity without TCR engagement.
Co-infection alters CD8 T cell immunity and immunoprotection (105.27)
Authors: Kenney Laurie , Cornberg Markus , Chen Alex , Trees Andrew , Emonet Sebastien , de la Torre Juan Carlos , Selin Liisa 
Published: January 2023

Abstract
Co-infection with multiple pathogens can result in increased pathology and difficulties with diagnosis and treatment. Moreover, interference between co-administered vaccines has resulted in lower antibody production. However, the effect of co-infections on T cell responses remains poorly understood. We have shown that sequential infection with unrelated viruses can alter T cell responses and disease outcome. This is defined as heterologous immunity, which is mediated by crossreactive T cells. We questioned if co-infection with two viruses containing a crossreactive epitope would alter the immune response and disease outcome upon rechallenge. Compared to mice infected with a single virus, rechallenged of mice co-infected with lymphocytic choriomenigitis (LCMV) and Pichinde viruses (PV) had a loss of immunoprotection and enhanced immunopathology. Each viral rechallenge identified a different potential mechanism to explain these changes. First, co-infection resulted in fewer LCMV-specific effector-like memory CD8 T cells leading to decreased protection and enhanced liver pathology. Secondly, co-infection caused some mice to have inappropriately enhanced crossreactive responses, which contributed to increased immunopathology. As combined vaccines or simultaneous immunizations are also co-infections, our data would suggest that T cell responses should be examined in the context of vaccine development.
Do fortuitous cross-reactive CD8 memory T cells dominate the response of aged mice to primary influenza virus infection? (105.37)
Authors: Lanzer Kathleen , Yager Eric , Blackman Marcia 
Published: January 2023

Abstract
A major contributing factor to the decline in immunity with age is reduced repertoire diversity, a consequence of thymic involution. The resulting decrease in naïve T cells and accumulating antigen experience leads to a dramatic increase in the ratio of memory to naïve peripheral CD8 T cells. We have described a major impact of age-associated reduced repertoire diversity on the response of aged mice to de novo influenza virus infection, in some cases resulting in a “hole in the repertoire.” We hypothesize that because of the enhanced ratio of memory to naïve cells in aged mice, fortuitously cross-reactive memory cells dominate the response to new infections. The implications are that responses in individual aged mice may be highly stochastic, of low avidity and with a restricted repertoire. We have confirmed the ability of fortuitously cross-reactive memory cells to respond to influenza virus by adoptive transfer experiments. CD8 memory (CD44high) T cells from influenza virus naïve mice were transferred into T cell-deficient recipients, which were then infected with influenza virus and the epitope-specific response measured 12 days later. Cumulative data show that transferred memory cells from 9 out of 15 mice were able to respond to influenza virus-specific epitopes. Experiments in progress will have profound implications for understanding the cellular immune response to new infections in aged mice, and for the development of vaccine strategies targeted to the elderly.
The role of IL-21 in rescuing CD8 T Cell responses in chronically infected HIV patients (105.38)
Authors: Yi John , Weinhold Kent 
Published: January 2023

Abstract
CD4 T cells are vital in regulating CD8 T cell responses during chronic viral infections. Notably, the hallmark of HIV infection is the severe loss of CD4 T cells resulting in defective CD8 T cell responses. One consequence of CD4 depletion following HIV infection is the loss of interleukin-21 (IL-21) production by the CD4 T cells, which has been demonstrated to be a critical factor in promoting viral control in murine studies. However, it is unknown whether IL-21 can rescue the exhausted CD8 T cells in chronically infected HIV+ patients. In this study we build upon novel murine studies to demonstrate a key role for IL-21 in improving CD8 T cell responses in PBMC from chronically infected HIV patients. To determine whether IL-21 can rescue exhausted CD8 T cells, PBMCs from HIV patients with viral loads &gt; 10,000 RNA copies/mL were incubated with IL-21. Following re-stimulation with overlapping Gag-peptide, IL-21 enhanced the production of IFN-γ by CD8 T cells although no effect was observed on IL-2 or TNF-α production. In addition, an increase in the central memory (CD45RO+CD27+) population was observed with IL-21 culture along with higher MFI of Bcl-6 levels. Interestingly, IL-21 cultured CD8 T cells expressed higher MFI of PD-1 even though CD8 T cell function was enhanced. Significantly, these results provide an approach in which IL-21 can be potentially used to enhance CD8 T cell responses in chronically infected HIV patients, whose CD4 counts are low or defective.
Transmembrane domain sequences regulate the association of MHC- class II with lipid raft microdomains (106.19)
Authors: Khandelwal Sanjay , Roche Paul 
Published: January 2023

Abstract
MHC II is known to be present in cholesterol-dependent lipid raft plasma membrane microdomains, and this association is important for MHC II- dependent activation of CD4 T cells by Dendritic cells (DCs). Until now it is not clear what regulates MHC II lipid raft association. In the present study we attempt to define the signals present in the MHC II transmembrane (TM) domain that regulate MHC II association with lipid rafts. Palmitoylation of cysteine residues is a well-known modification that often results in lipid raft association of TM protein and each MHC II I-Ab subunit contains a TM cysteine. We therefore expressed MHC II-α and β-chains containing TM domain cysteine → serine mutants in DCs obtained from MHC II null mice and analyzed MHC II lipid raft association. These experiments showed that the mutation of the TM cysteine residues actually enhanced MHC II raft localization about 3 fold. We also examined the role of the entire MHC II TM domain in lipid raft association. Replacement of the MHC II-α and β-chain TM domains with that of the non-raft protein ICAM 1 reduces MHC II lipid raft association 5 fold. We are currently examining the role of TM domain sequences present in each MHC II subunit in an attempt to identify dominant raft localization sequences in MHC II.
Plasma Membrane Interactions that determine Antigen Presentation by Antigen-Presenting Cells (106.20)
Authors: Hari Aswin , Shi Yan 
Published: January 2023

Abstract
Antigen presentation is a critical process in host defense for initiating adaptive immune responses. The APC loads peptides derived from antigens onto major histocompatibility complex (MHC) molecules and exports them to the surface for T cells sampling. If the primary interaction between an APC and T cell is successful, i.e. the TCR binds an appropriate MHC-peptide complex, this leads to an adaptive immune response. Peptide antigens are presented on two types of MHC molecules, MHC I and MHC II via several distinct processing pathways. In turn, the MHC molecule dictates which type of T cell can be activated and thereby the nature of the adaptive immune response. Therefore, antigen loading onto MHC molecules is a critical determinant of the adaptive immune responses. Exogenous antigens can be presented on MHC I and II molecules. Antigen processing mechanisms have been elucidated in great detail, but the fundamental reason behind why an antigen is directed into a specific pathway is not known. One of the foremost aims for this project is to determine why particulate antigens are presented more often on MHC I and why soluble antigens are more efficiently presented on MHC II, by deciphering the interactions of plasma membrane with particulate versus soluble antigen. This fundamental sensing mechanism of the human body when elucidated can help in generating an antiviral response in diseases like HIV and in field of preventative medicine.
The transcription factor AhR modulates the balance of functionally distinct DC subsets during influenza virus infection (106.5)
Authors: Jin Guang-Bi , Lawrence B. Paige 
Published: January 2023

Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor expressed in cells of the immune system. AhR activation by high-affinity ligands such as the pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) has been shown to suppress immune responses and impair host resistance to infection. However, the mechanisms by which AhR activation modulates immune function remain poorly understood. Dendritic cells (DCs) are antigen-presenting cells (APCs) that play a key role in priming naïve T cells. We previously reported that AhR activation reduces the ability of DCs to prime influenza virus-specific naïve CD8+ T cells ex vivo. In this study, we show that AhR activation changes the number of functionally distinct DC subsets in the lung and mediastinal lymph nodes in influenza virus-infected mice. By adoptively transferring virus-specific naïve CD8+ T cells into recipient mice, we demonstrate that AhR activation in the recipients dramatically reduces the clonal expansion and differentiation of transferred naïve virus-specific CD8+ T cells. Moreover, using AhR mutant mice, which express an AhR protein that binds ligand but cannot interact directly with DNA, we found that alterations in DC phenotype require the ligand-activated AhR complex to bind DNA via AhR’s DNA binding domain. Our findings suggest that AhR activation modulates phenotypically-distinct DC subsets, which may contribute to altered susceptibility and response to respiratory viral infection.
MDA5 Inhibits the Replication of Hepatitis B Virus (108.13)
Authors: Lu Hsin-Lin , Liao Fang 
Published: January 2023

Abstract
Hepatitis B virus (HBV) infection causes a wide spectrum of liver diseases; however, the innate immunity against HBV infection has been rarely studied and remains elusive. Here, we investigated the involvement of pattern recognition receptors, RIG-I like receptors (RLRs), in HBV replication. We demonstrated that the expression of MDA5, but not RIG-I, was increased in Huh-7 cells transfected with HBV replicative plasmids. Consistent with the in vitro finding, the expression of MDA5, but not RIG-I, was also increased in mice receiving HBV replicative plasmids through hydrodynamic injection. To further determine the effect of RLRs on HBV replication, we cotransfected MDA5 or RIG-I with HBV replicative plasmids into Huh-7 cells and measured HBV replication. The results showed that with similar protein levels of MDA5 and RIG-I, only MDA5, but not RIG-I, significantly inhibited HBV replication. In line with these results, knockdown of MDA5 by siRNA in cells transfected with HBV replicative plasmids increased HBV replication while knockdown of RIG-I did not have any effect on HBV replication. Interestingly, activation of MDA5 by HBV significantly induces IRF3 phosphorylation and NF-κB translocation. This result suggests that HBV-mediated MDA5 activation may be responsible for the IRF3 and NF-κB activation. In summary, our results demonstrate that MDA5, a known cytosolic sensor for RNA virus, contributes to the innate immune response against HBV infection.
Inherent baseline levels of phosphorylated IRF7 impact pDC IFNα response to TLR7 stimulation (108.8)
Authors: Griesbeck Morgane , Doyle Erin , Lindsay Robert , Boucau Julie , LeGall Sylvie , Altfeld Marcus , Chang J. Judy 
Published: January 2023

Abstract
Background: We previously showed that plasmacytoid dendritic cells (pDCs) derived from females can produce significantly more IFNα in response to HIV-1 and HIV-1-encoded TLR7/8 ligands than pDCs derived from males, resulting in stronger secondary activation of CD8+ T cells. Given the crucial role of interferon regulatory factor 7 (IRF7) in the regulation of type I IFN production by pDCs, we hypothesized that IRF7is involved in the differences observed in IFNα production. Methods: Fresh PBMC were isolated from HIV-1-negative subjects enrolled at Massachusetts General Hospital. Levels of IRF7 were measured in pDCs by phospho-flow cytometry, In-Cell Western blotting and qRT-PCR at baseline and at different time-points after TLR7 stimulation. IFNα levels were quantified by flow cytometry, ELISA and qRT-PCR Results: We observed a higher percentage of pDCs expressing phosphorylated IRF7 at baseline in females than in males using flow cytometry (p&lt;0.05). This difference persisted after TLR7 stimulation and was associated with higher IFNα production by females. Conclusion: These data show that sex differences in the baseline level of phosphorylated IRF7 in pDCs might account for described higher IFNα production upon TLR7 stimulation, and might provide new insights into the mechanisms underlying faster HIV-1 disease progression in females compared to males after controlling for viral load.
A Bruton’s Tyrosine Kinase inhibitor prevents antigen-driven B cell activation, germinal center persistence and memory B cell re-activation in vivo (109.10)
Authors: Rodriguez Varenka , Springer John , Schnute Mark , Dunussi-Joannopoulos Kyri , Douhan John , Ruzek Melanie , Benson Micah 
Published: January 2023

Abstract
The Tec family kinase, Bruton’s Tyrosine Kinase (BTK), is one of the key intracellular signaling components proximal to the B cell receptor (BCR). In this study, we utilized an orally-accessible BTK inhibitor (BTKi) to study the functional effects blocking this signaling pathway has on antigen-driven B cell activation in vivo. We report that BTK is required for anti-IgD driven B cell activation in vivo as evidenced by suppression of the surface activation markers CD86 and mRNA transcripts (e.g. c-Myc, Bcl-xL, CCL3, CD98, EBI2, EGR1, EGR2 and IRF4) otherwise rapidly induced upon engagement of the BCR with antigen. Using the T-dependent protein PE and SRBCs as model antigens, we tested for a requirement of BTK in generating antigen-specific IgM and IgG antibody titers and germinal centers, and find that BTK is required for germinal center maintenance. Lastly, we tested for a role of BTK in long-lived PE-specific memory B cell re-activation and report that BTKi significantly suppressed the induction of PE-specific IgM and IgG titers upon antigen re-challenge. The use of BTKi allowed us to bypass the impact a genetically inactivated BTK gene has on B cell development and to assess BTK inactivation in both a wild-type setting and in a temporal manner. These results provide insight into the role of BTK in BCR-driven B cell activation in various antigen naïve and experienced B cell populations.
Functional overlap between the mTOR and the unfolded protein response in the generation of mucosal plasma cells (109.2)
Authors: Tirosh Boaz , Benhamron Sandrine 
Published: January 2023

Abstract
Plasma cells (PCs) are terminally differentiated B lymphocyte responsible for antibody secretion. Differentiation into PCs involves a remarkable expansion of the endoplasmic reticulum (ER) in a mechanism that is governed by the unfolded protein response (UPR). The transcription factor XBP-1, which is activated in the course of UPR, is necessary for PC differentiation. In the absence of XBP-1, ER expansion is impaired and little amounts of antibody molecules are secreted. mTOR is an evolutionary conserved serine/threonine kinase. When activated, mTOR promotes protein translation and lipid biosynthesis. Deletion of TSC1 or TSC2 renders mTOR constitutively active. We investigated whether activation of the mTOR can override the requirement for XBP-1 in PC differentiation. To this end we generated mice single and double knocked out for XBP-1 and TSC1 in their B cell lineage. A normal serum IgA levels was observed in double knockout (DKO) animals, while IgM and IgG were reduced similarly to what measured in XBP-1 deficient mice. Because IgA is primarily secreted by mucosal PCs we investigated the IgA secretion in gut B cells. IgA was expressed and secreted to a higher level in the DKO than in XBP-1 KO. Our data demonstrate that the program for mucosal PC development can utilize the mTOR pathway in lieu of the UPR. This is the first indication that the mTOR under certain conditions can compensate for lack of the UPR in promoting the differentiation of professional secretory cells.
Immunoglobulin heavy chain enhancer's (Eμ) role in cell selection at the pre-B to immature B cell transition (109.7)
Authors: Peng Cheng , Eckhardt Laurel 
Published: January 2023

Abstract
We have recently described a second check-point for allelic exclusion that operates at the pre-B to immature B cell transition and is dependent upon the IgH intronic enhancer Eμ. We suggest that Eμ’s function at this transition is to ensure that IgH chains are made at levels sufficient to signal positive selection, regardless of light chain sequences and despite mono-allelic expression of the heavy chain. Evidence leading to this hypothesis includes our findings that B cells expressing an Eμ-deficient allele undergo heightened light-chain editing (suggesting that only some light-chain partners can circumvent the effects of lower BCR levels), or express a second IgH allele (“double-producing” cells to achieve higher BCR levels). We now show that B cells expressing an Eμ-deficient IgH allele, consistent with inefficient positive selection, remain longer at the pre-B cell stage, resulting in a significantly diminished immature B cell compartment. To determine whether escape from this developmental stall is dependent upon light chain, we limited the available light chain repertoire in these animals by pre-assembled VL insertion. The result was an effect on both B cell development and the emergence of double-producing cells. Together with our earlier findings, these new results suggest that IgH levels at the pre-B to immature B transition have an important impact on the breadth of the BCR repertoire as well as on the maintenance of allelic exclusion.
Intrinsic role of FoxO3a in the contraction of CD8+ T cell response (110.14)
Authors: Sad Subash , Haddad Elias , Peng Stanford , Sekaly Rafick , Tzelepis Fanny 
Published: January 2023

Abstract
CD8+ T cells undergo rapid expansion during infection with intracellular pathogens, which is followed by swift and massive culling of primed CD8+ T cells. The mechanisms that govern the massive contraction of primed CD8+ T cells are not clear. We show that the transcription factor Foxo3a plays a key role in the contraction, not expansion, of CD8+ T cell response against Listeria monocytogenes (LM). FoxO3a-mutant OVA-specific CD8+ T cells isolated during peak of response displayed reduced expression of pro-apoptotic molecules BIM and PUMA, and underwent reduced apoptosis during contraction phase in comparison to WT cells. A higher number of memory precursor effector cells (MPECs) were detectable in FoxO3a-mutant mice compared to WT mice during contraction phase. Furthermore, FoxO3a-mutant OVA-specific CD8+ T cells upon transfer into normal mice underwent highly reduced contraction. These results show for the first time that FoxO3a acts in a cell intrinsic manner to promote the culling of primed CD8+T cells during the contraction phase.
IL-10-IL-21-STAT3 axis regulates memory CD8 T cell development (110.9)
Authors: Cui Weiguo , Liu Ying , Weinstein Jason , Craft Joseph , Kaech Susan 
Published: January 2023

Abstract
Developing memory CD8 T cells is a paramount goal of many vaccines that will fight infections and cancer. Many types of acute infections can generate robust memory T cells, and therefore there must be a mechanism for instilling memory cell properties into a small portion of the memory precursor effector CD8 T cells and “preserve” their potential to develop into memory cells. However, the signals and genetic pathways that govern this process remain poorly defined. Here we show that the IL-10-IL-21-STAT3 pathway was critical for memory CD8 T cell development after acute LCMV infection. Lack of either IL-10 and IL-21 or STAT3, virus-specific CD8 T cells retained terminal effector (TE) differentiation states and failed to mature into protective memory T cells that contained self-renewing central memory T cells. Expression of BCL-6 and SOCS3 was considerably reduced in STAT3-deficient memory CD8 T cells, and BCL-6- or SOCS3-deficient CD8 T cells also had perturbed memory cell development. Reduced SOCS3 expression rendered STAT3-deficient CD8 T cells hyperresponsive to IL-12, suggesting that the STAT3-SOCS3 pathway helps to insulate memory precursor cells from inflammatory cytokines that drive TE differentiation. Next, we began to dissect the cellular sources of IL-10 and IL-21 and the temporal role of these cytokines in effector and memory CD8 T cell differentiation. This will advance our understanding of cellular mechanisms of memory CD8 T cell fate commitment and maintenance.
Membrane events after cross-linking of the chB6 alloantigen (111.42)
Authors: Funk Phillip , Sanderson Bailey 
Published: January 2023

Abstract
Chickens are one of the classic models of vertebrate immunity. We have been interested in the role of the alloantigen chB6 (formerly called BU1) in the development of B cells within the bursa and have presented evidence that chB6 can trigger apoptosis. Furthermore, the pathway that triggers apoptosis is similar to that triggered by FAS, with caspase 8 as an initiator, caspases 9 and 3 as later caspases, and bcl-xl functioning as an inhibitor of apoptosis. We have been unable to demonstrate a steady state association of chB6 and caspase 8 in DT40, so the mechanism of caspase 8 activation remains unclear. Here we show that chB6 localizes in distinct clusters on the surface of DT40 cells, reminiscent of the SPOTS others have described in Fas signaling. These clusters co-localize with cholera toxin labeled lipid rafts and chB6 appears to be internalized by the B cells. Western blots indicate that chB6 is present in both detergent soluble and insoluble membrane fractions on resting DT 40 cells. However, cross-linking chB6 with a secondary antibody shows that chB6 is internalized selectively from detergent insoluble (lipid raft) fractions of the cell membrane. This suggests an active distribution of chB6 in the membrane and an internal trafficking that may be functionally important. This work offers a new insight into the signaling via chB6. This work supported by a grant from the DePaul University Research Council.