scholarly journals Deconvoluting the T Cell Response to SARS-CoV-2: Specificity Versus Chance and Cognate Cross-Reactivity

2021 ◽  
Vol 12 ◽  
Author(s):  
Alexander A. Lehmann ◽  
Greg A. Kirchenbaum ◽  
Ting Zhang ◽  
Pedro A. Reche ◽  
Paul V. Lehmann
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Response ◽  
Viral Infections ◽  
Infected Individual ◽  
False Negative ◽  
Cross Reactivity ◽  
T Cell Response ◽  
T Cell Memory ◽  
Cell Memory

SARS-CoV-2 infection takes a mild or clinically inapparent course in the majority of humans who contract this virus. After such individuals have cleared the virus, only the detection of SARS-CoV-2-specific immunological memory can reveal the exposure, and hopefully the establishment of immune protection. With most viral infections, the presence of specific serum antibodies has provided a reliable biomarker for the exposure to the virus of interest. SARS-CoV-2 infection, however, does not reliably induce a durable antibody response, especially in sub-clinically infected individuals. Consequently, it is plausible for a recently infected individual to yield a false negative result within only a few months after exposure. Immunodiagnostic attention has therefore shifted to studies of specific T cell memory to SARS-CoV-2. Most reports published so far agree that a T cell response is engaged during SARS-CoV-2 infection, but they also state that in 20-81% of SARS-CoV-2-unexposed individuals, T cells respond to SARS-CoV-2 antigens (mega peptide pools), allegedly due to T cell cross-reactivity with Common Cold coronaviruses (CCC), or other antigens. Here we show that, by introducing irrelevant mega peptide pools as negative controls to account for chance cross-reactivity, and by establishing the antigen dose-response characteristic of the T cells, one can clearly discern between cognate T cell memory induced by SARS-CoV-2 infection vs. cross-reactive T cell responses in individuals who have not been infected with SARS-CoV-2.

scholarly journals Deconvoluting the T cell response to SARS-CoV-2: specificity versus chance- and cognate cross-reactivity

2020 ◽  
Author(s):  
Alexander A. Lehmann ◽  
Greg A. Kirchenbaum ◽  
Ting Zhang ◽  
Pedro A. Reche ◽  
Paul V. Lehmann
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Response ◽  
Viral Infections ◽  
Infected Individual ◽  
False Negative ◽  
Cross Reactivity ◽  
T Cell Response ◽  
T Cell Memory ◽  
Cell Memory

AbstractSARS-CoV-2 infection takes a mild or clinically inapparent course in the majority of humans who contract this virus. After such individuals have cleared the virus, only the detection of SARS-CoV-2-specific immunological memory can reveal the exposure, and hopefully the establishment of immune protection. With most viral infections, the presence of specific serum antibodies has provided a reliable biomarker for the exposure to the virus of interest. SARS-CoV-2 infection, however, does not reliably induce a durable antibody response, especially in sub-clinically infected individuals. Consequently, it is plausible for a recently infected individual to yield a false negative result within only a few months after exposure. Immunodiagnostic attention has therefore shifted to studies of specific T cell memory to SARS-CoV-2. Most reports published so far agree that a T cell response is engaged during SARS-CoV-2 infection, but they also state that in 20-81% of non-SARS-CoV-2-exposed individuals, T cells respond to SARS-CoV-2 antigens (mega peptide pools), allegedly due to T cell cross-reactivity with coronaviruses causing Common Cold (CCC), or other antigens. Here we show that by introducing irrelevant mega peptide pools as negative controls to account for chance cross-reactivity, and by establishing the antigen dose-response characteristic of the T cells, one can clearly discern between cognate T cell memory induced by SARS-CoV-2 infection vs. cross-reactive T cell responses in individuals who had not been infected with SARS-CoV-2.

scholarly journals Mechanisms that allow vaccination against an oncolytic vesicular stomatitis virus-encoded transgene to enhance safety without abrogating oncolysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amanda W. K. AuYeung ◽  
Robert C. Mould ◽  
Ashley A. Stegelmeier ◽  
Jacob P. van Vloten ◽  
Khalil Karimi ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Vesicular Stomatitis Virus ◽  
Cell Response ◽  
Viral Infections ◽  
T Cell Response ◽  
Oncolytic Viruses ◽  
Oncolytic Virotherapy ◽  
Cell Immunity ◽  
Vesicular Stomatitis

AbstractVaccination can prevent viral infections via virus-specific T cells, among other mechanisms. A goal of oncolytic virotherapy is replication of oncolytic viruses (OVs) in tumors, so pre-existing T cell immunity against an OV-encoded transgene would seem counterproductive. We developed a treatment for melanomas by pre-vaccinating against an oncolytic vesicular stomatitis virus (VSV)-encoded tumor antigen. Surprisingly, when the VSV-vectored booster vaccine was administered at the peak of the primary effector T cell response, oncolysis was not abrogated. We sought to determine how oncolysis was retained during a robust T cell response against the VSV-encoded transgene product. A murine melanoma model was used to identify two mechanisms that enable this phenomenon. First, tumor-infiltrating T cells had reduced cytopathic potential due to immunosuppression. Second, virus-induced lymphopenia acutely removed virus-specific T cells from tumors. These mechanisms provide a window of opportunity for replication of oncolytic VSV and rationale for a paradigm change in oncolytic virotherapy, whereby immune responses could be intentionally induced against a VSV-encoded melanoma-associated antigen to improve safety without abrogating oncolysis.

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.

scholarly journals Convergent epitope-specific T cell responses after SARS-CoV-2 infection and vaccination

2021 ◽  
Author(s):  
Anastasia A Minervina ◽  
Mikhail V Pogorelyy ◽  
Allison M Kirk ◽  
Emma Kaitlynn Allen ◽  
Kim J Allison ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Mononuclear Cells ◽  
T Cell Responses ◽  
T Cell Response ◽  
Critical Parameters ◽  
T Cell Memory ◽  
Cell Memory ◽  
Cell Responses ◽  
Depth Analysis

SARS-CoV-2 mRNA vaccines, including Pfizer/Biontech BNT162b2, were shown to be effective for COVID-19 prevention, eliciting both robust antibody responses in naive individuals and boosting pre-existing antibody levels in SARS-CoV-2-recovered individuals. However, the magnitude, repertoire, and phenotype of epitope-specific T cell responses to this vaccine, and the effect of vaccination on pre-existing T cell memory in SARS-CoV-2 convalescent patients, are still poorly understood. Thus, in this study we compared epitope-specific T cells elicited after natural SARS-CoV-2 infection, and vaccination of both naive and recovered individuals. We collected peripheral blood mononuclear cells before and after BNT162b2 vaccination and used pools of 18 DNA-barcoded MHC-class I multimers, combined with scRNAseq and scTCRseq, to characterize T cell responses to several immunodominant epitopes, including a spike-derived epitope cross-reactive to common cold coronaviruses. Comparing responses after infection or vaccination, we found that T cells responding to spike-derived epitopes show similar magnitudes of response, memory phenotypes, TCR repertoire diversity, and αβTCR sequence motifs, demonstrating the potency of this vaccination platform. Importantly, in COVID-19-recovered individuals receiving the vaccine, pre-existing spike-specific memory cells showed both clonal expansion and a phenotypic shift towards more differentiated CCR7-CD45RA+ effector cells. In-depth analysis of T cell receptor repertoires demonstrates that both vaccination and infection elicit largely identical repertoires as measured by dominant TCR motifs and receptor breadth, indicating that BNT162b2 vaccination largely recapitulates T cell generation by infection for all critical parameters. Thus, BNT162b2 vaccination elicits potent spike-specific T cell responses in naive individuals and also triggers the recall T cell response in previously infected individuals, further boosting spike-specific responses but altering their differentiation state. Overall, our study demonstrates the potential of mRNA vaccines to induce, maintain, and shape T cell memory through vaccination and revaccination.

T Cell Recognition of HCMV: Pan-Genome Analysis of Immunogenic Open-Reading Frames.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 606-606 ◽  
Author(s):  
Louis J. Picker ◽  
Andrew W. Sylwester ◽  
Bridget L. Mitchell ◽  
Cara Taormina ◽  
Christian Pelte ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Peripheral Blood ◽  
Cell Response ◽  
Cd8 T Cell ◽  
Cross Reactivity ◽  
T Cell Response ◽  
Cd4 T Cell ◽  
Cell Responses

Abstract Human Cytomegalovirus (HCMV) is among the largest and most complex of known viruses with 150–200nm virions enclosing a double stranded 230kb DNA genome capable of coding for >200 proteins. HCMV infection is life-long, and for the vast majority of immune competent individuals clinically benign. Disease occurs almost exclusively in the setting of immune deficiency, suggesting that the stable host-parasite relationship that characterizes these infections is the result of an evolutionarily “negotiated” balance between viral mechanisms of pathogenesis and the host immune response. In keeping with, and perhaps because of this balance, the human CD4+ T cell response to whole HCMV viral lysates is enormous, with median peripheral blood frequencies of HCMV-specific cells ~5–10 fold higher than for analogous preparations of other common viruses. Although certain HCMV ORFs have been identified as targets of either the CD4+ or CD8+ T cell response, the specificities comprising the CD4+ T cell response, and both the total frequencies and component parts of the CD8+ T cell response are unknown. Here, we used cytokine flow cytometry and ~14,000 overlapping 15mer peptides comprising all 213 HCMV ORFs encoding proteins >100 amino acids in length to precisely define the total CD4+ and CD8+ HCMV-specific T cell responses and the HCMV ORFs responsible for these responses in 33 HCMV-seropositive, HLA-disparate donors. An additional 9 HCMV seronegative donors were similarly examined to define the extent to which non-HCMV responses cross-react with HCMV-encoded epitopes. We found that when totaled, the median frequencies of HCMV-specific CD4+ and CD8+ T cells in the peripheral blood of the seropositive subjects were 4.0% and 4.5% for the total CD4+ or CD8+ T cell populations, respectively (which corresponds to 9.1% and 10.5% of the memory populations, respectively). The HCMV-specific CD4+ and CD8+ T cell responses included a median 12 and 7 different ORFs, respectively, and all told, 73 HCMV ORFs were identified as targets for both CD4+ and CD8+ T cells, 26 ORFs as targets for CD8+ T cells alone, and 43 ORFS as targets for CD4+ T cells alone. UL55, UL83, UL86, UL99, and UL122 were the HCMV ORFs most commonly recognized by CD4+ T cells; UL123, UL83, UL48, UL122 and UL28 were the HCMV ORFs most commonly recognized by CD8+ T cells. The relationship between immunogenicity and 1) HLA haplotype and 2) ORF expression and function will be discussed. HCMV-seronegative individuals were non-reactive with the vast majority of HCMV peptides. Only 7 potentially cross-reactive responses were identified (all by CD8+ T cells) to 3 ORFs (US32, US29 and UL116) out of a total of almost 4,000 potential responses, suggesting fortuitous cross-reactivity with HCMV epitopes is uncommon. These data provide the first glimpse of the total human T cell response to a complex infectious agent, and will provide insight into the rules governing immunodominance and cross-reactivity in complex viral infections of humans.

scholarly journals Broadly targeted human cytomegalovirus-specific CD4+ and CD8+ T cells dominate the memory compartments of exposed subjects

2005 ◽  
Vol 202 (5) ◽  
pp. 673-685 ◽  
Author(s):  
Andrew W. Sylwester ◽  
Bridget L. Mitchell ◽  
John B. Edgar ◽  
Cara Taormina ◽  
Christian Pelte ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Human Cytomegalovirus ◽  
Cd8 T Cells ◽  
Viral Infections ◽  
Infectious Agent ◽  
Cross Reactivity ◽  
T Cell Response ◽  
Open Reading Frames ◽  
Human T Cell

Human cytomegalovirus (HCMV) infections of immunocompetent hosts are characterized by a dynamic, life-long interaction in which host immune responses, particularly of T cells, restrain viral replication and prevent disease but do not eliminate the virus or preclude transmission. Because HCMV is among the largest and most complex of known viruses, the T cell resources committed to maintaining this balance have never been characterized completely. Here, using cytokine flow cytometry and 13,687 overlapping 15mer peptides comprising 213 HCMV open reading frames (ORFs), we found that 151 HCMV ORFs were immunogenic for CD4+ and/or CD8+ T cells, and that ORF immunogenicity was influenced only modestly by ORF expression kinetics and function. We further documented that total HCMV-specific T cell responses in seropositive subjects were enormous, comprising on average ∼10% of both the CD4+ and CD8+ memory compartments in blood, whereas cross-reactive recognition of HCMV proteins in seronegative individuals was limited to CD8+ T cells and was rare. These data provide the first glimpse of the total human T cell response to a complex infectious agent and will provide insight into the rules governing immunodominance and cross-reactivity in complex viral infections of humans.

Rapid T Cell Response to Vaccination Can Occur without Antibody Response in Children Post HSCT.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2235-2235
Author(s):  
W. Nicholas Haining ◽  
J. Evans ◽  
N. Seth ◽  
G. Callaway ◽  
K. Wucherpfennig ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cell ◽  
Cell Response ◽  
Influenza A ◽  
T Cell Response ◽  
T Cell Memory ◽  
Cell Immunity ◽  
Before And After ◽  
B Cell Response

Abstract Vaccination is widely used to improve pathogen-specific immunity in patients post HSCT, but it is not known whether patients can mount an effective T cell response to vaccine antigens (vAg). Moreover the relationship between T and B cell response to vAg has not been studied. We hypothesized that a sufficiently sensitive assay of T cell response to vAg would allow vaccination to be used as a tool to measure immune recovery post HSCT and improve vaccine design. We therefore: (1) developed a flow-cytometry-based approach to quantify and characterize T cells specific for vAg; (2) validated it by measuring T cell immunity to influenza A in normal donors; and (3) characterized the T and B cell response to influenza vaccination in pediatric HSCT patients. PBMC were labeled with CFSE and stimulated in vitro with whole influenza Ag. Ag-specific T cells were sensitively detected by their proliferation (loss of CFSE fluorescence) and simultaneous expression of the activation marker HLA-DR. Proliferating/active T cells could be readily detected after stimulation with influenza A Ag in healthy adult (n=4) and pediatric (n=19) donors but were absent in control conditions. Both CD4+ and CD8+ T cell proliferation was detected in all donors but one, and in children as young as 6mo. Staining with MHC I- and MHC II-tetramers confirmed that the proliferating/active population contained T cells specific for immunodominant CD8+ and CD4+ epitopes, demonstrating that vAg were processed and presented to epitope-specific T cells. To characterize the phenotype of influenza-specific T cell memory, we separated memory and naive CD4+ cells prior to antigen-stimulation. Antigen-experienced (CD45RA−/CCR7−) but not naive (CD45RA+/CCR7+) T cells proliferated to vAg confirming that the assay detected pre-existing influenza-A-specific T cell memory. We next assessed Influenza-A-specific T cell immunity before and after influenza vaccination in five pediatric HSCT recipients (mean age 10.6y, range 5–15y; mean time from transplant 13m, range 3–21m). Prior to vaccination the CD4 proliferation to influenza-A was a mean of 3.3% (range 0.04–11%). Following vaccination CD4 proliferation increased significantly in all patients (mean 19.0%, range 6.9%–31.8%, p=0.02). This increase was specific as proliferation to control Ag was unchanged. Influenza-A CD8+ proliferation also increased in 3 of 5 patients but was not statistically significant for the group consistent with the limited efficacy of soluble vAg in inducing CD8+ T cell response. All patients had detectable influenza-A-specific IgG levels prior to vaccination but despite a T cell response to vaccination in all patients, none had a significant increase in IgG level following vaccination. Only one patient had an IgM response; this patient also had the highest influenza-A-specific CD4 proliferation before and after immunization suggesting that there may be a threshold of T cell response required for a B cell response. Using a novel assay we demonstrate that a T cell response to vaccination can occur without an accompanying B cell response. This assay provides a more sensitive measure of immunity to vaccination and allows vaccine response to be used as a benchmark of strategies to accelerate post-HSCT T cell reconstitution.

Immunological Memory: Remembering Our Pathogens.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. sci-23-sci-23
Author(s):  
Rafi Ahmed
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cell ◽  
Viral Infections ◽  
Memory T Cells ◽  
Immunological Memory ◽  
T Cell Response ◽  
Cell Memory ◽  
Humoral And Cellular Immunity ◽  
B Cell Memory

Abstract Acute viral infections induce long-term humoral and cellular immunity. However, the nature of T- and B-cell memory is different. Antiviral B-cell memory is usually manifested by continuous antibody production that lasts for many years after infection or vaccination. In contrast, the effector phase of the T cell response is short-lived (a few weeks), and “memory” in the T-cell compartment results from the presence of memory T cells, which are found at higher frequencies and can respond faster and develop into effector cells (i.e., CTL or cytokine producers) more efficiently than can naïve T cells. In this talk, I will discuss the following aspects of immunological memory: Functional differences between naïve and memory T cells; Memory T cell differentiation and memory cell subsets; and Protective immunity by memory CD8 T cells.

scholarly journals The significance of low bcl-2 expression by CD45RO T cells in normal individuals and patients with acute viral infections. The role of apoptosis in T cell memory.

1993 ◽  
Vol 178 (2) ◽  
pp. 427-438 ◽  
Author(s):  
A N Akbar ◽  
N Borthwick ◽  
M Salmon ◽  
W Gombert ◽  
M Bofill ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Viral Infections ◽  
Apoptotic Cell ◽  
Interleukin 2 ◽  
Lymphoid Cells ◽  
T Cell Memory ◽  
Varicella Zoster Virus Infection ◽  
Cell Memory ◽  
Activated T Cells

The bcl-2 gene product has been shown to prevent apoptotic cell death. We have now investigated the bcl-2 protein expression by resting and activated mature T cell populations. Freshly isolated CD45RO+ T cells within CD4+ and CD8+ subsets expressed significantly less bcl-2 than CD45RO- (CD45RA+) T cells (p < 0.001). When CD45RA+ T cells within both CD4+ and CD8+ subsets were activated in vitro, the transition to CD45RO phenotype was associated with a decrease in bcl-2 expression. Patients with acute viral infections such as infectious mononucleosis caused by Epstein-Barr virus infections or chickenpox, resulting from varicella zoster virus infection, had circulating populations of activated CD45RO+ T cells which also showed low bcl-2 expression. In these patients, a significant correlation was seen between low bcl-2 expression by activated T cells and their apoptosis in culture (r = 0.94, p < 0.001). These results suggest that the primary activation of T cells leads to the expansion of a population that is destined to perish unless rescued by some extrinsic event. Thus the suicide of CD45RO+ T cells could be prevented by the addition of interleukin 2 to the culture medium which resulted in a concomitant increase in the bcl-2 expression of these cells. Alternatively, apoptosis was also prevented by coculturing the activated T lymphocytes with fibroblasts, which maintained the viability of lymphoid cells in a restinglike state but with low bcl-2 expression. The paradox that the CD45RO+ population contains the primed/memory T cell pool yet expresses low bcl-2 and is susceptible to apoptosis can be reconciled by the observations that maintenance of T cell memory may be dependent on the continuous restimulation of T cells, which increases their bcl-2 expression. Furthermore, the propensity of CD45RO+ T cells to extravasate may facilitate encounter with fibroblast-like cells in tissue stroma and thus be an important additional factor which promotes the survival of selected primed/memory T cells in vivo.

scholarly journals CCR5 deficiency impairs CD4+ T cell memory responses and antigenic sensitivity through increased ceramide synthesis

2020 ◽  
Author(s):  
Ana Martín-Leal ◽  
Raquel Blanco ◽  
Josefina Casas ◽  
María E. Sáez ◽  
Elena Rodríguez-Bovolenta ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Response ◽  
T Cell Memory ◽  
Functional Fitness ◽  
Cell Memory ◽  
Lipid Species ◽  
Ceramide Synthesis ◽  
Ceramide Synthases ◽  
Specific Lipid

ABSTRACTIn CD4+ T cells, CCR5 is not only a coreceptor for HIV-1 infection, but also contributes to their functional fitness. Here we show that by limiting GATA-1-induced transcription of specific ceramide synthases, CCR5 signaling reduces ceramide levels and thereby increases T cell antigen receptor (TCR) nanoclustering in antigen-experienced mouse and human CD4+ T cells. This activity is CCR5-specific and independent of CCR5 costimulatory activity. CCR5-deficient mice showed reduced production of high affinity class-switched antibodies, but only after antigen rechallenge, which implies an impaired memory CD4+ T cell response. This study identifies a CCR5 function in the generation of CD4+ T cell memory responses, and establishes an antigen-independent mechanism that regulates TCR nanoclustering by altering specific lipid species.

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