scholarly journals Mechanisms of induction of CD8⁺ T cell responses by dendritic cells

2021 ◽  
Author(s):  
◽  
Taryn Louise Osmond
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cell Activation ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cross Presentation ◽  
Cell Responses ◽  
Circulating Antigen

<p>Splenic CD8α⁺ dendritic cells (DCs) have been described as key antigen presenting cells for the induction of CD8⁺ T cell responses to circulating antigen. This is through a heightened capacity to acquire and present the antigens via the process of cross-presentation, expression of high levels of the co-stimulatory and adhesion molecules required to stimulate CD8⁺ T cells, and the capacity to release high levels of the cytokines required to drive differentiation of CD8⁺ T cells into cytotoxic T lymphocytes (CTLs). However, recent research has indicated that the splenic CD8α⁺ DC population is more heterogeneous than originally thought. A previous study from my own laboratory suggested that a population of CD8α⁺ DCs that express the c-type lectin langerin primarily possess the heightened functions previously attributed to the total CD8α⁺ population. Therefore, the aim of this thesis research was to explore this subset of DCs in more detail, with specific emphasis on gaining mechanistic insight into their ability to elicit CD8⁺ T cell responses to circulating proteins. In the first section of this thesis, the hypothesis that the splenic langerin⁺ CD8α⁺ DCs were the critical subset involved in the induction of strong systemic CD8⁺ T cell responses to circulating antigen was tested in detail. This was examined using a genetically modified mouse model in which langerin-expressing cells could be easily identified and/or specifically depleted. It was first shown that the induction of CD8⁺ T cell responses to the model antigen ovalbumin was dependent on entry into the spleen in the presence of appropriate stimulation, which in these studies was provided by agonists for the toll-like receptors (TLRs) and/or signals from innate-like lymphocytes called natural killer T (NKT) cells. The primary targets for these signals were shown to be splenic langerin⁺ CD8α⁺ DCs, as CD8⁺ T cell responses were significantly reduced in hosts depleted of these cells within the spleen. Furthermore, agonists for TLRs that were not expressed by langerin⁺ CD8α⁺ DCs failed to enhance T cell responses. The langerin⁺ CD8α⁺ DCs were shown to be located in the marginal zone of the spleen, where they could readily screen the blood for antigens, and their function was critical to the induction of CD8⁺ T cell responses within six hours of antigen delivery. Interestingly, other local langerin-negative antigen presenting cells (APCs) were shown to be capable of cross-presentation, but with significantly reduced capacity to prime CD8⁺ T cell responses. Therefore, in the second section of this thesis the hypothesis that the langerin-negative APCs were capable of contributing to CD8⁺ T cell responses with appropriately timed stimuli was investigated. One of the downstream effects of inducing NKT cell activation at the time of priming was shown to be the “pre-conditioning” of langerin-negative DCs, allowing them to respond strongly to subsequent TLR ligation. Using SiglecH-DTR mice, it was shown that plasmacytoid DCs (which are langerin-negative) were pre-conditioned by NKT cell activation, allowing them to respond more actively to the delayed TLR stimulation by producing significantly enhanced levels of IFN-α. This factor was also potentially responsible for “feeding back” to the CD8α⁺ DCs (including langerin-expressing CD8α⁺ DCs), to enhance their function, as indicated by increases in cytokine production. Significantly, the major langerin-negative DC populations, defined as CD8α⁻ DCs, were pre-conditioned to have an enhanced cytokine release response to subsequent stimulation through TLR7, a receptor not expressed by langerin-positive DCs. This enhanced ability to respond to TLR7 ligation permitted these langerin-negative APCs to contribute to increased CD8⁺ T cell accumulation, with enhanced functional activity. Importantly, the CD8⁺ T cell response induced remained significantly dependent on initial cross-priming by langerin⁺ CD8α⁺ DCs, and it was only through pre-conditioning that langerinnegative APCs could contribute to enhancing the T cell response. In the third section of this thesis, the hypothesis that the CD8⁺ T cell responses generated in the presence of langerin⁺ CD8α⁺ DCs were phenotypically and functionally distinct from those responses generated in their absence was tested. No obvious differences were seen in CD8⁺ T cell homing, memory phenotype, restimulatory capacity, and expression of key molecules involved in metabolic function, survival and cytolytic function. However, in vivo cytotoxic function several weeks after priming was comparable, suggesting that this function was not related to initial burst size, providing some evidence of difference in function between CD8⁺ T cells primed in the presence or absence of langerin⁺ CD8α⁺ DCs. In summary, the splenic langerin⁺ CD8α⁺ DCs are the major subset responsible for cross-priming CD8⁺ T cell responses to circulating antigen, and for interpreting multiple stimulatory signals for enhancing the response. However, effective CD8⁺ T cell responses can be generated in their absence, particularly when antigens are provided in the context of appropriately temporally phased stimuli.</p>

scholarly journals Mechanisms of induction of CD8⁺ T cell responses by dendritic cells

2021 ◽  
Author(s):  
◽  
Taryn Louise Osmond
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cell Activation ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cross Presentation ◽  
Cell Responses ◽  
Circulating Antigen

<p>Splenic CD8α⁺ dendritic cells (DCs) have been described as key antigen presenting cells for the induction of CD8⁺ T cell responses to circulating antigen. This is through a heightened capacity to acquire and present the antigens via the process of cross-presentation, expression of high levels of the co-stimulatory and adhesion molecules required to stimulate CD8⁺ T cells, and the capacity to release high levels of the cytokines required to drive differentiation of CD8⁺ T cells into cytotoxic T lymphocytes (CTLs). However, recent research has indicated that the splenic CD8α⁺ DC population is more heterogeneous than originally thought. A previous study from my own laboratory suggested that a population of CD8α⁺ DCs that express the c-type lectin langerin primarily possess the heightened functions previously attributed to the total CD8α⁺ population. Therefore, the aim of this thesis research was to explore this subset of DCs in more detail, with specific emphasis on gaining mechanistic insight into their ability to elicit CD8⁺ T cell responses to circulating proteins. In the first section of this thesis, the hypothesis that the splenic langerin⁺ CD8α⁺ DCs were the critical subset involved in the induction of strong systemic CD8⁺ T cell responses to circulating antigen was tested in detail. This was examined using a genetically modified mouse model in which langerin-expressing cells could be easily identified and/or specifically depleted. It was first shown that the induction of CD8⁺ T cell responses to the model antigen ovalbumin was dependent on entry into the spleen in the presence of appropriate stimulation, which in these studies was provided by agonists for the toll-like receptors (TLRs) and/or signals from innate-like lymphocytes called natural killer T (NKT) cells. The primary targets for these signals were shown to be splenic langerin⁺ CD8α⁺ DCs, as CD8⁺ T cell responses were significantly reduced in hosts depleted of these cells within the spleen. Furthermore, agonists for TLRs that were not expressed by langerin⁺ CD8α⁺ DCs failed to enhance T cell responses. The langerin⁺ CD8α⁺ DCs were shown to be located in the marginal zone of the spleen, where they could readily screen the blood for antigens, and their function was critical to the induction of CD8⁺ T cell responses within six hours of antigen delivery. Interestingly, other local langerin-negative antigen presenting cells (APCs) were shown to be capable of cross-presentation, but with significantly reduced capacity to prime CD8⁺ T cell responses. Therefore, in the second section of this thesis the hypothesis that the langerin-negative APCs were capable of contributing to CD8⁺ T cell responses with appropriately timed stimuli was investigated. One of the downstream effects of inducing NKT cell activation at the time of priming was shown to be the “pre-conditioning” of langerin-negative DCs, allowing them to respond strongly to subsequent TLR ligation. Using SiglecH-DTR mice, it was shown that plasmacytoid DCs (which are langerin-negative) were pre-conditioned by NKT cell activation, allowing them to respond more actively to the delayed TLR stimulation by producing significantly enhanced levels of IFN-α. This factor was also potentially responsible for “feeding back” to the CD8α⁺ DCs (including langerin-expressing CD8α⁺ DCs), to enhance their function, as indicated by increases in cytokine production. Significantly, the major langerin-negative DC populations, defined as CD8α⁻ DCs, were pre-conditioned to have an enhanced cytokine release response to subsequent stimulation through TLR7, a receptor not expressed by langerin-positive DCs. This enhanced ability to respond to TLR7 ligation permitted these langerin-negative APCs to contribute to increased CD8⁺ T cell accumulation, with enhanced functional activity. Importantly, the CD8⁺ T cell response induced remained significantly dependent on initial cross-priming by langerin⁺ CD8α⁺ DCs, and it was only through pre-conditioning that langerinnegative APCs could contribute to enhancing the T cell response. In the third section of this thesis, the hypothesis that the CD8⁺ T cell responses generated in the presence of langerin⁺ CD8α⁺ DCs were phenotypically and functionally distinct from those responses generated in their absence was tested. No obvious differences were seen in CD8⁺ T cell homing, memory phenotype, restimulatory capacity, and expression of key molecules involved in metabolic function, survival and cytolytic function. However, in vivo cytotoxic function several weeks after priming was comparable, suggesting that this function was not related to initial burst size, providing some evidence of difference in function between CD8⁺ T cells primed in the presence or absence of langerin⁺ CD8α⁺ DCs. In summary, the splenic langerin⁺ CD8α⁺ DCs are the major subset responsible for cross-priming CD8⁺ T cell responses to circulating antigen, and for interpreting multiple stimulatory signals for enhancing the response. However, effective CD8⁺ T cell responses can be generated in their absence, particularly when antigens are provided in the context of appropriately temporally phased stimuli.</p>

scholarly journals Role of Thymic Output in Regulating CD8 T-Cell Homeostasis during Acute and Chronic Viral Infection

2005 ◽  
Vol 79 (15) ◽  
pp. 9419-9429 ◽  
Author(s):  
Nicole E. Miller ◽  
Jennifer R. Bonczyk ◽  
Yumi Nakayama ◽  
M. Suresh
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cell Response ◽  
Viral Infections ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cell Responses ◽  
Lcmv Infection

ABSTRACT Although it is well documented that CD8 T cells play a critical role in controlling chronic viral infections, the mechanisms underlying the regulation of CD8 T-cell responses are not well understood. Using the mouse model of an acute and chronic lymphocytic choriomeningitis virus (LCMV) infection, we have examined the relative importance of peripheral T cells and thymic emigrants in the elicitation and maintenance of CD8 T-cell responses. Virus-specific CD8 T-cell responses were compared between mice that were either sham thymectomized or thymectomized (Thx) at ∼6 weeks of age. In an acute LCMV infection, thymic deficiency did not affect either the primary expansion of CD8 T cells or the proliferative renewal and maintenance of virus-specific lymphoid and nonlymphoid memory CD8 T cells. Following a chronic LCMV infection, in Thx mice, although the initial expansion of CD8 T cells was normal, the contraction phase of the CD8 T-cell response was exaggerated, which led to a transient but striking CD8 T-cell deficit on day 30 postinfection. However, the virus-specific CD8 T-cell response in Thx mice rebounded quickly and was maintained at normal levels thereafter, which indicated that the peripheral T-cell repertoire is quite robust and capable of sustaining an effective CD8 T-cell response in the absence of thymic output during a chronic LCMV infection. Taken together, these findings should further our understanding of the regulation of CD8 T-cell homeostasis in acute and chronic viral infections and might have implications in the development of immunotherapy.

The Response to Repeated Vaccination with PR1 and WT1 Peptides Admixed in Montanide Adjuvant Is Transient and Fails to Induce Sustained Anti-Leukemia Responses in Patients with Myeloid Malignancies.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4096-4096
Author(s):  
Katayoun Rezvani ◽  
Agnes S. M. Yong ◽  
Stephan Mielke ◽  
Behnam Jafarpour ◽  
Bipin N. Savani ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cell Response ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Gm Csf ◽  
Cell Responses ◽  
Ifn Γ

Abstract Abstract 4096 Poster Board III-1031 We previously demonstrated the immunogenicity of a combined vaccine approach employing two leukemia-associated antigenic peptides, PR1 and WT1 (Rezvani Blood 2008). Eight patients with myeloid malignancies received one subcutaneous 0.3 mg and 0.5 mg dose each of PR1 and WT1 vaccines in Montanide adjuvant, with 100 μg of granulocyte-macrophage colony-stimulating factor (GM-CSF). CD8+ T-cell responses against PR1 or WT1 were detected in all patients as early as 1 week post-vaccination. However, responses were only sustained for 3-4 weeks. The emergence of PR1 or WT1-specific CD8+ T-cells was associated with a significant but transient reduction in minimal residual disease (MRD) as assessed by WT1 expression, suggesting a vaccine-induced anti-leukemia response. Conversely, loss of response was associated with reappearance of WT1 transcripts. We hypothesized that maintenance of sustained or at least repetitive responses may require frequent boost injections. We therefore initiated a phase 2 study of repeated vaccination with PR1 and WT1 peptides in patients with myeloid malignancies. Five patients with acute myeloid leukemia (AML) and 2 patients with myelodysplastic syndrome (MDS) were recruited to receive 6 injections at 2 week intervals of PR1 and WT1 in Montanide adjuvant, with GM-CSF as previously described. Six of 7 patients completed 6 courses of vaccination and follow-up as per protocol, to monitor toxicity and immunological responses. Responses to PR1 or WT1 vaccine were detected in all patients after only 1 dose of vaccine. However, additional boosting did not further increase the frequency of PR1 or WT1-specific CD8+ T-cell response. In 4/6 patients the vaccine-induced T-cell response was lost after the fourth dose and in all patients after the sixth dose of vaccine. To determine the functional avidity of the vaccine-induced CD8+ T-cell response, the response of CD8+ T-cells to stimulation with 2 concentrations of PR1 and WT1 peptides (0.1 and 10 μM) was measured by IC-IFN-γ staining. Vaccination led to preferential expansion of low avidity PR1 and WT1 specific CD8+ T-cell responses. Three patients (patients 4, 6 and 7) returned 3 months following the 6th dose of PR1 and WT1 peptide injections to receive a booster vaccine. Prior to vaccination we could not detect the presence of PR1 and WT1 specific CD8+ T-cells by direct ex-vivo tetramer and IC-IFN-γ assay or with 1-week cultured IFN-γ ELISPOT assay, suggesting that vaccination with PR1 and WT1 peptides in Montanide adjuvant does not induce memory CD8+ T-cell responses. This observation is in keeping with recent work in a murine model where the injection of minimal MHC class I binding peptides derived from self-antigens mixed with IFA adjuvant resulted in a transient effector CD8+ T cell response with subsequent deletion of these T cells and failure to induce CD8+ T cell memory (Bijker J Immunol 2007). This observation can be partly explained by the slow release of vaccine peptides from the IFA depot without systemic danger signals, leading to presentation of antigen in non-inflammatory lymph nodes by non-professional antigen presenting cells (APCs). An alternative explanation for the transient vaccine-induced immune response may be the lack of CD4+ T cell help. In summary these data support the immunogenicity of PR1 and WT1 peptide vaccines. However new approaches will be needed to induce long-term memory responses against leukemia antigens. To avoid tolerance induction we plan to eliminate Montanide adjuvant and use GM-CSF alone. Supported by observations that the in vivo survival of CD8+ T-effector cells against viral antigens are improved by CD4+ helper cells, we are currently attempting to induce long-lasting CD8+ T-cell responses to antigen by inducing CD8+ and CD4+ T-cell responses against class I and II epitopes of WT1 and PR1. Disclosures: No relevant conflicts of interest to declare.

scholarly journals TLR9 and Dendritic Cells Are Required for CD8+ T Cell Responses to the AAV Capsid

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 552-552 ◽  
Author(s):  
Geoffrey L. Rogers ◽  
Roland W Herzog
Keyword(s):  
Pattern Recognition ◽  
T Cells ◽  
T Cell ◽  
Immune Responses ◽  
Cd8 T Cells ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Post Injection ◽  
Cell Responses

Abstract CD8+ T cell responses to the adeno-associated virus (AAV) capsid have posed a significant barrier to transduction in clinical trials of AAV-mediated gene therapy for hemophilia B, as reactivation of a memory CTL response to the capsid is capable of eliminating transduced hepatocytes in the absence of immunosuppression. Recently, it has been suggested that innate immune responses induced by the toll-like receptor (TLR) pathway can influence the development of adaptive immune responses to AAV-mediated gene transfer. In particular, reports have implicated TLR2 (AAV capsid), TLR9 (AAV genome), and MyD88 (downstream signaling adaptor of both these TLRs). Herein, we have used a modified AAV2 with an insertion of the immunodominant MHC class I epitope of ovalbumin into the capsid (AAV2-SIINFEKL) to study the mechanism of CD8+ T cell responses to the AAV capsid. Using an H2-Kb-SIINFEKL tetramer reagent, we determined that anti-capsid CD8+ T cell responses depended on the TLR9-MyD88 pathway. While the frequency of circulating capsid-specific CD8+ T cells peaked around 7-10 days post-injection and subsided after about 21 days in wild type (WT) mice, tetramer-positive cells were not detected in TLR9-/- or MyD88-/- mice. The kinetics and magnitude of the response was unaltered in TLR2-/- mice. Mice deficient in STING, a downstream adaptor of multiple cytoplasmic DNA sensing pathways, also developed comparable capsid-specific CD8+ T cell frequencies to WT mice, suggesting that this is not a general effect of pattern recognition of DNA. Interestingly, the frequency of capsid-specific CD8+ T cells was not reduced in AP3-/- mice, which are deficient in type I IFN signaling downstream of TLR9. Adoptively transferred OVA-specific OT-1 T cells proliferated in WT but not TLR9-/- mice that received AAV2-SIINFEKL, confirming the importance of TLR9. The effect was antigen-specific, as OT-1 cells in WT mice that received AAV2 lacking SIINFEKL showed minimal proliferation comparable to TLR9-/- mice. In addition to pattern-recognition receptors, we also assessed the role of antigen-presenting cells in the CD8+ T cell response to capsid. The formation of capsid-specific CD8+ T cells was unaltered in mice that received gadolinium chloride to inactivate macrophages, or in B cell-deficient μMT mice. Depletion of B cells in WT mice prior to vector administration also failed to affect the anti-capsid CD8+ T cell response. However, transient depletion of dendritic cells (DCs) in CD11c-DTR mice resulted in a delayed development of capsid-specific CD8+ T cells. Seven days post-injection, DC-depleted mice had a significantly reduced frequency of tetramer-positive CD8+ T cells which recovered to normal by 10 days, likely due to the repopulation of DCs before the input capsid was completely cleared. Overall, our results show that TLR9 signaling, most likely in DCs, is required for the formation of de novo anti-capsid CD8+ T cell responses. Disclosures Herzog: Genzyme: AAV-FIX technology Patents & Royalties.

scholarly journals Mesothelin-specific CD8+ T Cell Responses Provide Evidence of In Vivo Cross-Priming by Antigen-Presenting Cells in Vaccinated Pancreatic Cancer Patients

2004 ◽  
Vol 200 (3) ◽  
pp. 297-306 ◽  
Author(s):  
Amy Morck Thomas ◽  
Lynn M. Santarsiero ◽  
Eric R. Lutz ◽  
Todd D. Armstrong ◽  
Yi-Cheng Chen ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
Cross Presentation ◽  
Cell Responses ◽  
Antigen Presenting

Tumor-specific CD8+ T cells can potentially be activated by two distinct mechanisms of major histocompatibility complex class I–restricted antigen presentation as follows: direct presentation by tumor cells themselves or indirect presentation by professional antigen-presenting cells (APCs). However, controversy still exists as to whether indirect presentation (the cross-priming mechanism) can contribute to effective in vivo priming of tumor-specific CD8+ T cells that are capable of eradicating cancer in patients. A clinical trial of vaccination with granulocyte macrophage–colony stimulating factor–transduced pancreatic cancer lines was designed to test whether cross-presentation by locally recruited APCs can activate pancreatic tumor-specific CD8+ T cells. Previously, we reported postvaccination delayed-type hypersensitivity (DTH) responses to autologous tumor in 3 out of 14 treated patients. Mesothelin is an antigen demonstrated previously by gene expression profiling to be up-regulated in most pancreatic cancers. We report here the consistent induction of CD8+ T cell responses to multiple HLA-A2, A3, and A24-restricted mesothelin epitopes exclusively in the three patients with vaccine-induced DTH responses. Importantly, neither of the vaccinating pancreatic cancer cell lines expressed HLA-A2, A3, or A24. These results provide the first direct evidence that CD8 T cell responses can be generated via cross-presentation by an immunotherapy approach designed to recruit APCs to the vaccination site.

scholarly journals 612 Human CLEC9A antibodies deliver NY-ESO-1 antigen to CD141+ dendritic cells to activate naïve and memory NY-ESO-1-specific CD8+ T cells

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A648-A648
Author(s):  
Kelly-Anne Masterman ◽  
Oscar Haigh ◽  
Kirsteen Tullett ◽  
Ingrid Leal-Rojas ◽  
Carina Walpole ◽  
...  
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
Ethics Committee ◽  
Cross Presentation ◽  
Cell Responses ◽  
Melanoma Patients

BackgroundDendritic cells (DC) are crucial for the efficacy of cancer vaccines, but current vaccines do not harness the key cDC1 subtype required for effective CD8+ T cell mediated tumor immune responses. Vaccine immunogenicity could be enhanced by specific delivery of immunogenic tumor antigens to CD141+ DC, the human cDC1 equivalent. CD141+ DC exclusively express the C-type-lectin-like receptor CLEC9A, which is important for the regulation of CD8+ T cell responses. This study developed a new vaccine that harnesses a human anti-CLEC9A antibody to specifically deliver the immunogenic tumor antigen, NY-ESO-1 to human CD141+ DC. The ability of the CLEC9A-NY-ESO-1 antibody to activate NY-ESO-1 specific naïve and memory CD8+ T cells was examined and compared to a vaccine comprised of a human DEC-205-NY-ESO-1 antibody that targets all human DC.MethodsHuman anti-CLEC9A, anti-DEC-205 and isotype control IgG4 antibodies were genetically fused to NY-ESO-1 polypeptide. Cross-presentation to NY-ESO-1- epitope specific CD8+ T cells and reactivity of T cell responses in melanoma patients was assessed by IFNγ production following incubation of CD141+ DC and patient peripheral blood mononuclear cells with targeting antibodies. Humanized mice containing human DC subsets and a repertoire of naïve NY-ESO-1-specific CD8+ T cells were used to investigate naïve T cell priming. T cell effector function was measured by expression of IFNγ, MIP-1β, TNF and CD107a and by lysis of target tumor cells.ResultsCLEC9A-NY-ESO-1 Ab were effective at mediating delivery and cross-presentation of multiple NY-ESO-1 epitopes by CD141+ DC for activation of NY-ESO-1-specific CD8+ T cells. When benchmarked to NY-ESO-1 conjugated to an untargeted control antibody or to anti-human DEC-205, CLEC9A-NY-ESO-1 was superior at ex vivo reactivation of NY-ESO-1-specific T cell responses in melanoma patients. Moreover, CLEC9A-NY-ESO-1 induced priming of naïve NY-ESO-1-specific CD8+ T cells with polyclonal effector function and potent tumor killing capacity in vitro.ConclusionsThese data advocate human CLEC9A-NY-ESO-1 antibody as an attractive strategy for specific targeting of CD141+ DC to enhance tumour immunogenicity in NY-ESO-1-expressing malignancies.Ethics ApprovalWritten informed consent was obtained for human sample acquisition in line with standards established by the Declaration of Helsinki. Study approval was granted by the Mater Human Research Ethics Committee (HREC13/MHS/83 and HREC13/MHS/86) and The U.S. Army Medical Research and Materiel Command (USAMRMC) Office of Research Protections, Human Research Protection Office (HRPO; A-18738.1, A-18738.2, A-18738.3). All animal experiments were approved by the University of Queensland Animal Ethics Committee and conducted in accordance with the Australian Code for the Care and Use of Animals for Scientific Purposes in addition to the laws of the United States and regulations of the Department of Agriculture.

scholarly journals LB-18. Broad and Prevalent SARS-CoV-2 CD8+ T Cell Response in Recovered COVID-19 Individuals Demonstrates Kinetics of Early Differentiation

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S852-S853
Author(s):  
Hassen Kared ◽  
Evan Bloch ◽  
Andrew Redd ◽  
Alessandra Nardin ◽  
Hermi Sumatoh ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cell Response ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Peptide Epitopes ◽  
Cell Responses ◽  
Candidate Peptide

Abstract Background Understanding the diversity, breadth, magnitude, and functional profile of the T cell response against SARS-CoV-2 in recovered COVID-19 individuals is critical to evaluate the contribution of T cells to produce a potentially protective immune response. Methods We used a multiplexed peptide-MHC tetramer approach to screen a total of 408 SARS-CoV-2 candidate peptide epitopes for CD8+ T cell recognition in a cohort of 30 individuals recovered from COVID-19. The peptides spanned the whole viral genome and were restricted to six prevalent HLA alleles; T cells were simultaneously characterized by a 28-marker phenotypic panel. The evolution of the SARS-CoV-2 T cell responses was then statistically modeled against time from diagnosis, and in relation to humoral and inflammatory response. Workflow for Study. A multiplexed peptide-MHC tetramer approach was used to screen SARS-CoV-2 candidate peptide epitopes in a cohort of 30 COVID-19 recovered patients across 6 prevalent HLA alleles, and T cells profiled with a 28-marker phenotypic panel. Multiplex tetramer screen. One representative COVID-19 recovered patient and one healthy donor were screened for HLA- relevant SARS-CoV-2 epitopes, as well as epitopes for CMV, EBV, Influenza, Adenovirus and MART-1. Shown are the frequencies of tetramer-positive CD8 T cells from 2 technical replicates per subject. Results Almost all individuals screened showed a T cell response against SARS-CoV-2 (29/30): 132 SARS-CoV-2-specific CD8+ T cells hits were detected, corresponding to 52 unique reactive epitopes. Twelve of the 52 unique SARS-CoV-2-specific epitopes were recognized by more than 40% of the individuals screened, indicating high prevalence in the subjects. Importantly, these CD8+ T cell responses were directed against both structural and non-structural viral proteins, with the highest magnitude against nucleocapsid derived peptides, but without any antigen-driven bias in the phenotype of specific T cells. Overall, SARS-CoV-2 T cells showed specific states of differentiation (stem-cell memory and transitional memory), which differed from those of MART-1, influenza, CMV and EBV-specific T cells. UMAP visualization revealed a phenotypic profile of SARS-CoV-2-specific CD8 T cells in COVID-19 convalescent donors that is distinct from other viral specificities, such as influenza, CMV, EBV and Adenovirus. SARS-CoV-2 epitope screening revealed CD8+ T cell responses directed against both structural and non-structural viral proteins, with the highest magnitude response against nucleocapsid derived peptides Conclusion The kinetics modeling demonstrates a dynamic, evolving immune response characterized by a time-dependent decrease in overall inflammation, increase in neutralizing antibody titer, and progressive differentiation of a broad SARS-CoV-2 CD8 T cell response. It could be desirable to aim at recapitulating the hallmarks of this robust CD8 T cell response in the design of protective COVID-19 vaccines. Disclosures Hassen Kared, PhD, ImmunoScape (Shareholder) Alessandra Nardin, DvM, ImmunoScape (Shareholder) Hermi Sumatoh, BSc, Dip MTech, ImmunoScape (Shareholder) Faris Kairi, BSc, ImmunoScape (Shareholder) Daniel Carbajo, PhD, ImmunoScape (Shareholder) Brian Abel, PhD, MBA, ImmunoScape (Shareholder) Evan Newell, PhD, ImmunoScape (Shareholder)

scholarly journals Defining Kinetic Properties of HIV-Specific CD8+ T-cell Responses in Acute Infection

2019 ◽  
Author(s):  
Yiding Yang ◽  
Vitaly V. Ganusov
Keyword(s):  
T Cells ◽  
Viral Load ◽  
T Cell ◽  
Cd8 T Cells ◽  
Chronic Infection ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cell Responses ◽  
Average Viral Load

Multiple lines of evidence indicate that CD8$^+$ T cells are important in the control of HIV-1 (HIV) replication. However, CD8$^+$ T cells induced by natural infection cannot eliminate the virus or reduce viral loads to acceptably low levels in most infected individuals. Understanding the basic quantitative features of CD8$^+$ T-cell responses induced during the course of HIV infection may therefore inform us about the limits that HIV vaccines, which aim to induce protective CD8$^+$ T-cell responses, must exceed. Using previously published experimental data from a cohort of HIV-infected individuals with sampling times from acute to chronic infection we defined the quantitative properties of CD8$^+$ T-cell responses to the whole HIV proteome. In contrast with a commonly held view, we found that the relative number of HIV-specific CD8$^+$ T-cell responses (response breadth) changed little over the course of infection (first 400 days post-infection), with moderate but statistically significant changes occurring only during the first 35 symptomatic days. This challenges the idea that a change in the T-cell response breadth over time is responsible for the slow speed of viral escape from CD8$^+$ T cells in the chronic infection. The breadth of HIV-specific CD8$^+$ T-cell responses was not correlated with the average viral load for our small cohort of patients. Metrics of relative immunodominance of HIV-specific CD8$^+$ T-cell responses such as Shannon entropy or the Evenness index were also not significantly correlated with the average viral load. Our mathematical-model-driven analysis suggested extremely slow expansion kinetics for the majority of HIV-specific CD8$^+$ T-cell responses and the presence of intra- and interclonal competition between multiple CD8$^+$ T-cell responses; such competition may limit the magnitude of CD8$^+$ T-cell responses, specific to different epitopes, and the overall number of T-cell responses induced by vaccination. Further understanding of mechanisms underlying interactions between the virus and virus-specific CD8$^+$ T-cell response will be instrumental in determining which T-cell-based vaccines will induce T-cell responses providing durable protection against HIV infection.

scholarly journals Optimizing Immunization Strategies for the Induction of Antigen-Specific CD4 and CD8 T Cell Responses for Protection against Intracellular Parasites

2016 ◽  
Vol 23 (9) ◽  
pp. 785-794 ◽  
Author(s):  
Kimberly A. Hofmeyer ◽  
Malcolm S. Duthie ◽  
John D. Laurance ◽  
Michelle A. Favila ◽  
Neal Van Hoeven ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Intracellular Pathogens ◽  
Content Type ◽  
Cell Responses ◽  
Immunization Strategies

ABSTRACTImmunization strategies that generate either CD4 or CD8 T cell responses are relatively well described, but less is known with regard to optimizing regimens to induce both CD4 and CD8 memory T cells. Considering the importance of both CD4 and CD8 T cells in the control of intracellular pathogens such asLeishmania donovani, we wanted to identify vaccines that could raise both CD4 and CD8 T cell responses and determine how to configure immunization strategies to generate the best combined protective T cell response. We examined responses generated against theLeishmaniavaccine antigen F3 following its administration in either recombinant form with the Toll-like receptor 4 (TLR4) agonist-containing adjuvant formulation GLA-SE (F3+GLA-SE) or as a gene product delivered in an adenoviral vector (Ad5-F3). Homologous immunization strategies using only F3+GLA-SE or Ad5-F3 preferentially generated either CD4 or CD8 T cells, respectively. In contrast, heterologous strategies generated both antigen-specific CD4 and CD8 T cells. Administration of F3+GLA-SE before Ad5-F3 generated the greatest combined CD4 and CD8 responses. Cytotoxic CD8 T cell responses were highest when Th1 cells were generated prior to their induction by Ad5-F3. Finally, a single immunization with a combination of F3+GLA-SE mixed with Ad5-F3 was found to be sufficient to provide protection against experimentalL. donovaniinfection. Taken together, our data delineate immunization regimens that induce antigen-specific CD4 and CD8 T cell memory responses, and identify a single immunization strategy that could be used to rapidly provide protection against intracellular pathogens in regions where access to health care is limited or sporadic.

Cross Priming of Transgene Product-Specific CD8+ T Cells in Hepatic AAV Gene Transfer Depends on IL-1 Receptor and XCR1+ Dendritic Cells but Not TLR9

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 2-3
Author(s):  
Sandeep Kumar ◽  
Moanaro Biswas ◽  
Annie R Pineros ◽  
Ype P De Jong ◽  
Roland W Herzog
Keyword(s):  
T Cells ◽  
T Cell ◽  
Gene Transfer ◽  
Cd8 T Cells ◽  
Cell Response ◽  
Adaptor Protein ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
Cell Responses

Introduction: Adeno-associated virus (AAV) mediated gene transfer is currently evaluated in multiple Phase I/II and Phase III studies for the treatment of hemophilia. However, immune responses to both the AAV capsid and encoded transgene remain major impediments to clinical translation. Several studies have implicated innate immune sensors such as Toll-like receptors (TLR) and their downstream adaptor molecule MyD88 in sensing viral structures. TLR9-MyD88 signaling has been linked to cross-priming of CD8+ T cell responses to capsid and also to transgene product-specific CD8+ T cell responses. However, little is known about other signaling pathways that may lead to immune activation. Previously, our lab has shown that while liver gene transfer is capable of inducing immunological tolerance to AAV encoded transgene products, vector dose and design play a critical role. For instance, low hepatic gene expression levels may elicit a CD8+ T cell response to the AAV encoded transgene, resulting in loss of the model antigen ovalbumin (OVA) in C57BL/6 mice or of FIX expression in hemophilia B mice. We investigated innate immune sensing pathways that may play a role in initiating transgene specific CD8+ T cell response in the hepatic microenvironment. Further, we determined the contribution of hepatic antigen presenting cells (APC) by selectively depleting/neutralizing APCs and evaluating their effect on presentation of transgene product-derived antigen following AAV8-OVA liver gene delivery. Methods: Wild-type (WT) C57BL6 and specific innate sensing knockout mice on the C57BL6 background were intravenously (IV) injected with a predetermined immunogenic dose (1x109vg) of hepatotropic AAV8-OVA vector (Mol Ther 25:880, 2017). PBMCs were quantified at 4 weeks for OVA-specific CD8+ T cells using a class I MHC tetramer. Hepatic APC types [Kupffer cells, neutrophils, CD103+ dendritic cell (DC), CD11c+ DC, XCR1+ DC] involved in transgene specific CD8+ T cell activation were selectively depleted/inactivated by pre-treatment with gadolinium chloride (GdCl3), Ly6G, CD103 antibody respectively, or by administering diphtheria toxin (DT) to CD11c-DTR and XCR1-DTR mice. This was followed by intravenous administration of AAV8-OVA and CellTrace violet labeled OT-1 cells. Results: Similar to WT mice, TLR9-/-, TLR2-/-, TRIF-/-, IFNaR-/- and MDA5-/- mice developed a CD8+ T cell response indicating that these sensors do not play a role in transgene specific CD8+ T cells response. Interestingly, adaptor protein MyD88-/- mice did not elicit CD8+ T cell response to OVA, implying a MyD88 dependent but TLR9 independent response. Since MyD88 is an essential adaptor protein not only for TLR but also for interleukin-1 (IL-1) signaling pathways, we next analyzed IL-1R-/- mice. Similar to MyD88-/- mice, IL-1R-/- mice did not show OVA specific CD8+ T cells (p=0.006, 0.007 respectively), indicating that transgene-specific adaptive responses are mediated by IL-1R/MyD88 signaling. Kupffer cells and DCs are principal APCs in liver and infiltrating neutrophils could also act as APCs under inflammatory conditions in liver microenvironment. Using proliferation of OT-I cells as readout we tested if any of these cell types are required for presentation to transgene specific CD8+ T cells. In naïve control, GdCl3 treated and a-Ly6G antibody treated mice, OT-I cell proliferation reached 60%, 65% and 48% on average, respectively. Depletion of CD11c DCs substantially reduced the proliferation of OT-I cells to ~6% (p&lt;0.0001) indicating a critical role for DCs in mediating transgene specific CD8+ T cell responses. Since XCR1+ DCs are the major cross-presenting DCs and hepatic resident CD103+ DCs are shown to have intrinsically enhanced capacity to process and present antigen to naïve CD8+ T cells, we further sought to assess if any of these DCs plays a role in activation of transgene specific CD8+ T cells. Neutralization of CD103+ DCs reduced OT-I proliferation to 39% (p=0.01) whereas depletion of XCR1+ DCs reduced the proliferation to ~20% (p&lt;0.0001) indicating a major role for XCR1+ DCs. Conclusions: In summary, we uncovered a novel-signaling pathway that can activate CD8+ T cell responses during AAV gene transfer independent of TLR9 sensing. The IL-1R/MyD88 pathway drives activation of transgene specific CD8+ T cell, and XCR1+ DCs are critically involved in cross-presenting transgene product-derived antigen to CD8+ T cells. Disclosures Herzog: Takeda Pharmaceuticals: Patents & Royalties.

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