Biomedical subjects

Ingrid Leiner

Publications and source records attributed to Ingrid Leiner.

13 recordsLinked to original sources

PubMed2006

Innate immune activation and CD4+ T cell priming during respiratory fungal infection.

Aspergillus fumigatus is a mold that causes a spectrum of diseases, including lethal lung infections in immunocompromised humans and allergic asthma in atopic individuals. T helper 1 (Th1) CD4(+) T cells protect against invasive A. fumigatus infections whereas Th2 CD4(+) T cells exacerbate asthma upon inhalation of A. fumigatus spores. Herein, we demonstrate that A. fumigatus-specific T cells were rapidly primed in lymph nodes draining the lung and fully differentiated into interferon-gamma (IFN-gamma)-producing Th1 CD4(+) T cells upon arrival in the airways. T-bet induction in A. fumigatus-specific CD4(+) T cells was enhanced by MyD88-mediated signals in draining lymph nodes, but T cell proliferation, trafficking, and Th1 differentiation in the airways were Toll-like receptor (TLR) and MyD88 independent. Our studies demonstrate that CD4(+) T cell differentiation during respiratory fungal infection occurs incrementally, with TLR-mediated signals in the lymph node enhancing the potential for IFN-gamma production whereas MyD88-independent signals promote Th1 differentiation in the lung.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Remodeling specific immunity by use of MHC tetramers: demonstration in a graft-versus-host disease model.

Major histocompatibility complex (MHC) molecules carrying selected peptides will bind specifically to their cognate T-cell receptor on individual clones of reactive T cells. Fluorescently labeled, tetrameric MHC-peptide complexes have been widely used to detect and quantitate antigen-specific T-cell populations via flow cytometry. We hypothesized that such MHC-peptide tetramers could also be used to selectively deplete unique reactive T-cell populations, while leaving the remaining T-cell repertoire and immune response intact. In this report, we successfully demonstrate that a tetramer-based depletion of T cells can be achieved in a murine model of allogeneic bone marrow transplantation. Depletion of a specific alloreactive population of donor splenocytes (< 0.5% of CD8+ T cells) prior to transplantation significantly decreased morbidity and mortality from graft-versus-host disease. There was no early regrowth of the antigen-specific T cells in the recipient and in vivo T-cell proliferation was greatly reduced as well. Survival was increased more than 3-fold over controls, yet the inherent antitumor activity of the transplant was retained. This method also provides the proof-of-concept for similar strategies to selectively remove other unwanted T-cell clones, which could result in novel therapies for certain autoimmune disorders, T-cell malignancies, and solid organ graft rejection.

Animals↗

PubMed2005

Distinct regulation of H2-M3-restricted memory T cell responses in lymph node and spleen.

CD8 T cell populations restricted by H2-M3 MHC class Ib molecules expand rapidly during primary Listeria monocytogenes infection but only minimally upon reinfection. In contrast, CD8 T cells restricted by MHC class Ia molecules undergo more delayed expansion during primary infection but rapid and robust expansion following reinfection. In this study we demonstrate that primary H2-M3-restricted CD8 T cell responses are unaffected by the frequency of naive MHC class Ia-restricted T cells during L. monocytogenes infection. The magnitude of H2-M3-restricted memory responses, in contrast, is down-modulated by increasing frequencies of MHC class Ia-restricted effector T cells following secondary systemic infection. Suppression by MHC class Ia-restricted T cells, however, is not a universal feature of MHC class Ib-restricted memory responses. Primary systemic L. monocytogenes infection followed by secondary tissue infection, for example, results in robust expansion of H2-M3-restricted memory T cells in draining lymph nodes, despite the activation of MHC class Ia-restricted memory T cell responses. Thus, whereas MHC class Ia-restricted memory T cell populations predominate in spleens following systemic reinfection, H2-M3-restricted memory T cell responses remain prominent in lymph nodes draining localized infections. Our studies demonstrate that interactions between CD8 T cell populations can differ, depending on the status of the responding T cells (naive vs memory) and the route of reinfection. These results may have important implications for prime-boost vaccination strategies.

Animals↗

PubMed2005

Distinct in vivo dendritic cell activation by live versus killed Listeria monocytogenes.

Immunization of mice with live or heat-killed Listeria monocytogenes (HKLM) efficiently primes pathogen-specific CD8(+) T cells. T lymphocytes primed by HKLM, however, undergo attenuated proliferation and do not fully differentiate. Thus, only infection with live bacteria induces long-term, CD8(+) T cell-mediated protective immunity. In this study we demonstrate that live and heat-killed bacteria, while both associating with Mac-3(+)CD11b(hi) cells, localize to distinct splenic areas following intravenous inoculation. While HKLM localize to the marginal zone and the splenic red pulp, live L. monocytogenes are carried to the T cell zone of splenic white pulp. Despite these differences, in vivo depletion of CD11c-expressing cells prevents priming of naive T cells by either HKLM or live L. monocytogenes. Analysis of CD11c(hi) dendritic cells (DC) reveals that infection with live L. monocytogenes induces higher levels of CD40, CD80 and CD86 expression than immunization with HKLM. Our results suggest that CD8(+) T cell priming following HKLM immunization or live infection is mediated by DC and that the disparate outcomes of priming can be attributed to suboptimal conditioning of DC in the absence of live, cytosol-invasive bacteria.

Animals↗

PubMed2005

Cross-recognition of N-formylmethionine peptides is a general characteristic of H2-M3-restricted CD8+ T cells.

H2-M3-restricted CD8+ T cells can exhibit cross-reactivity to different bacterially derived N-formylmethionine peptides. The extent of this promiscuity is unclear. We deleted the nonredundant fMIVTLF epitope and found that Listeria monocytogenes still primed fMIVTLF-specific T cells. Thus, cross-reactivity appears to be a more general characteristic of H2-M3-restricted T cells.

Animals↗

PubMed2004

Targeted deletion of T-cell clones using alpha-emitting suicide MHC tetramers.

Immunosuppressive agents in current use are nonspecific. The capacity to delete specific CD8 T-cell clones of unique specificity could prove to be a powerful tool for dissecting the precise role of CD8(+) T cells in human disease and could form the basis for a safe, highly selective therapy of autoimmune disorders. Major histocompatibility complex (MHC) tetramers (multimeric complexes capable of binding to specific CD8 T-cell clones) were conjugated to (225)Ac (an alpha-emitting atomic nanogenerator, capable of single-hit killing from the cell surface) to create an agent for CD8 T-cell clonal deletion. The "suicide" tetramers specifically bound to, killed, and reduced the function of their cognate CD8 T cells (either human anti-Epstein-Barr virus (EBV) or mouse anti-Listeria in 2 model systems) while leaving the nonspecific control CD8 T-cell populations unharmed. Such an approach may allow a pathway to selective ablation of pathogenic T-cell clones ex vivo or in vivo without disturbing general immune function.

Animals↗

PubMed2004

Rapid development of T cell memory.

Prime-boost immunization is a promising strategy for inducing and amplifying pathogen- or tumor-specific memory CD8 T cell responses. Although expansion of CD8 T cell populations following the second Ag dose is integral to the prime-boost strategy, it remains unclear when, after priming, memory T cells become competent to proliferate. In this study, we show that Ag-specific CD8 T cells with the capacity to undergo extensive expansion are already present at the peak of the primary immune response in mice. These early memory T cells represent a small fraction of the primary immune response and, at early time points, their potential to proliferate is obscured by large effector T cell populations that rapidly clear Ag upon reimmunization. With sufficient Ag boosting, however, secondary expansion of these memory cells can be induced as early as 5-7 days following primary immunization. Importantly, both early and delayed boosting result in similar levels of protective immunity to subsequent pathogen challenge. Early commitment and differentiation of memory T cells during primary immunization suggest that a short duration between priming and boosting is feasible, providing potential logistic advantages for large-scale prime-boost vaccination of human populations.

Animals↗

PubMed2003

Promiscuity of MHC class Ib-restricted T cell responses.

Murine infection with the Gram-positive intracellular bacterium Listeria monocytogenes activates CD8(+) T cells that recognize bacterially derived N-formyl methionine peptides in the context of H2-M3 MHC class Ib molecules. Three peptides, fMIGWII, fMIVIL, and fMIVTLF, are targets of L. monocytogenes-specific CD8(+) T cells. To investigate epitope cross-recognition by H2-M3-restricted CD8(+) T cells, we deleted the sequence encoding fMIGWII from a virulent strain of L. monocytogenes. Infection with fMIGWII-deficient L. monocytogenes unexpectedly primed CD8(+) T cells that stain with fMIGWII/H2-M3 tetramers and lyse fMIGWII-coated target cells in vivo. Because the fMIGWII sequence is nonredundant, we speculated that other bacterially derived Ags are priming these responses. HPLC peptide fractionation of bacterial culture supernatants revealed several distinct L. monocytogenes-derived peptides that are recognized by fMIGWII-specific T cells. Our results demonstrate that the dominant H2-M3-restricted CD8(+) T cell population, although reactive with fMIGWII, is primed by other, non-fMIGWII peptides derived from L. monocytogenes. Although this degree of Ag receptor promiscuity is unusual for the adaptive immune system, it may be a more common feature of T cell responses restricted by nonpolymorphic MHC class Ib molecules.

Animals↗

PubMed2003

H2-M3-restricted memory T cells: persistence and activation without expansion.

H2-M3-restricted T cells respond more rapidly to primary Listeria monocytogenes infection than conventional MHC class Ia-restricted T cells. Reinfection with L. monocytogenes, while inducing explosive proliferation of H2-K(d)-restricted T cells, does not stimulate significant expansion of H2-M3-restricted CTL. These disparate responses to reinfection are apparent within 5 days of primary L. monocytogenes infection. However, H2-M3-restricted memory T cells are generated, and are indistinguishable from classically restricted T cells in terms of cell surface memory markers and longevity. Early responses of H2-M3- and H2-K(d)-restricted memory T cells to reinfection are similar, with increases in size and expression of activation markers. Interestingly, priming of H2-M3-restricted T cells with an L. monocytogenes-derived N-formyl peptide plus anti-CD40 generates memory T cells that expand upon re-exposure to Ag during L. monocytogenes infection. Our data indicate that disparate H2-M3- and MHC class Ia-restricted memory T cell responses reflect intrinsic differences between these T cell populations. Although distinct proliferative programs appear to be hardwired in these populations during primary L. monocytogenes infection, under different inflammatory circumstances M3-restricted T cell populations can maintain the ability to expand upon re-exposure to Ag.

Animals↗

PubMed2003

Impaired recovery of Epstein-Barr virus (EBV)--specific CD8+ T lymphocytes after partially T-depleted allogeneic stem cell transplantation may identify patients at very high risk for progressive EBV reactivation and lymphoproliferative disease.

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes are considered pivotal to prevent lymphoproliferative disease (LPD) in allogeneic stem cell transplantation (SCT) recipients. We evaluated the recovery of EBV-specific CD8+ T cells after partially T-cell-depleted SCT and studied the interaction between EBV-specific CD8+ T cells, EBV reactivation, and EBV-LPD. EBV-specific CD8+ T cells were enumerated using 12 class I HLA tetramers presenting peptides derived from 7 EBV proteins. Blood samples were taken at regular intervals after SCT in 61 patients, and EBV DNA levels were assessed by real-time polymerase chain reaction. Forty-five patients showed EBV reactivation, including 25 with high-level reactivation (ie, more than 1000 genome equivalents [geq] per milliliter). Nine of these 25 patients progressed to EBV-LPD. CD8+ T cells specific for latent or lytic EBV epitopes repopulated the peripheral blood at largely similar rates. In most patients, EBV-specific CD8+ T-cell counts had returned to normal levels within 6 months after SCT. Concurrently, the incidence of EBV reactivations clearly decreased. Patients with insufficient EBV-specific CD8+ T-cell recovery were at high risk for EBV reactivation in the first 6 months after SCT. Failure to detect EBV-specific CD8+ T cells in patients with high-level reactivation was associated with the subsequent development of EBV-LPD (P =.048). Consequently, the earlier defined positive predictive value of approximately 40%, based on high-level EBV reactivation only, increased to 100% in patients without detectable EBV-specific CD8+ T cells. Thus, impaired recovery of EBV-specific CD8+ T cells in patients with high-level EBV reactivation may identify a subgroup at very high risk for EBV-LPD and supports that EBV-specific CD8+ T cells protect SCT recipients from progressive EBV reactivation and EBV-LPD.

Adolescent↗

PubMed2002

Robust recall and long-term memory T-cell responses induced by prime-boost regimens with heterologous live viral vectors expressing human immunodeficiency virus type 1 Gag and Env proteins.

We investigated long-term memory and recall cellular immune responses to human immunodeficiency virus type 1 (HIV-1) Env and Gag proteins elicited by recombinant vesicular stomatitis viruses (VSVs) expressing Env and Gag. More than 7 months after a single vaccination with VSV-Env, approximately 6% of CD8(+) splenocytes stained with major histocompatibility complex class I tetramers containing the Env p18-I10 immunodominant peptide and showed a memory phenotype (CD44(Hi)). The level of tetramer-positive cells in memory was about 14% of the peak primary response. Recall responses elicited in these mice 5 days after boosting with a heterologous recombinant vaccinia virus expressing HIV-1 Env showed that 40 to 45% of CD8(+) splenocytes were tetramer positive and activated (CD62L(Lo)), and these cells produced gamma interferon after stimulation with Env peptide, indicating that they were functional. Five months after the boost, the long-term memory cell population (tetramer positive, CD44(Hi)) constituted 30% of the CD8(+) splenocytes. Recall responses to HIV-1 Gag were examined in mice primed with VSV recombinants expressing HIV-1 Gag protein and boosted with a vaccinia virus recombinant expressing Gag. Using this protocol, we found that approximately 40% of CD8(+) splenocytes were activated (CD62L(Lo)) and specific for a Gag immunodominant peptide (tetramer positive). The high-level Gag recall response elicited by the vaccinia virus-Gag was greater than that obtained by boosting with a VSV-Gag vector with a different VSV glycoprotein. The corresponding levels of CD44(Hi) memory cells were also higher long after boosting with vaccinia virus-Gag than after boosting with a glycoprotein exchange VSV-Gag. Our results show that VSV vectors elicit high-level memory CTL responses and that these can be amplified as much as six- to sevenfold using a heterologous boosting vector.

AIDS Vaccines↗

PubMed2002

High-level primary CD8(+) T-cell response to human immunodeficiency virus type 1 gag and env generated by vaccination with recombinant vesicular stomatitis viruses.

We investigated the primary cellular immune responses to human immunodeficiency virus type 1 (HIV-1) Env and Gag proteins elicited by recombinant vesicular stomatitis viruses (rVSVs). The primary response to Env peaked 5 to 7 days after intraperitoneal vaccination, at which time 40% of CD8(+) cells were Env tetramer positive and activated (CD62L(Lo)). These freshly isolated cells actively lysed target cells pulsed with the p18-I10 peptide and secreted gamma interferon and tumor necrosis factor alpha after stimulation with the Env p18-I10 peptide. The primary response to Env elicited by rVSVs was sixfold higher than that elicited by recombinant vaccinia viruses (rVVs) at 5 days postvaccination. An intranasal route of vaccination with VSV-Env also elicited a strong primary response to Env. The primary immune response to Gag elicited by rVSV peaked 7 days after vaccination, at which time 3% of CD8(+) cells were Gag tetramer positive and CD62L(Lo) and functional by intracellular cytokine staining. This response was eightfold higher than that elicited by rVV expressing Gag. VSV-GagEnv, which expresses both Gag and Env from a single recombinant, also induced strong cytotoxic T-lymphocyte (CTL) responses to both Env and Gag. Our quantitative analyses illustrate the potency of the VSV vector system in CTL induction.

AIDS Vaccines↗

PubMed2002

Rescue of CD8 T cell-mediated antimicrobial immunity with a nonspecific inflammatory stimulus.

Reconstitution of protective immunity by adoptive transfer of pathogen-specific T cells has been successful in patients with compromised cellular immunity. The in vivo effectiveness of in vitro-expanded CD8 CTLs is variable, however. For example, adoptively transferred Listeria monocytogenes-specific CD8 CTLs only confer protective immunity if challenge infection occurs within 48 hours of T cell infusion. Herein we show that transferred CTLs persist in lymphoid compartments for many weeks, but that their response to bacterial challenge decreases during the first week following transfer. While T cells transferred less than 48 hours before infection proliferate, those transferred 7 days before infection die. Remarkably, treatment of mice with anti-CD40 at the time of T cell infusion reprograms transferred T cells, allowing them to proliferate and confer protective immunity upon bacterial challenge 7 days later. Our study demonstrates, for the first time to our knowledge that CD40-mediated stimuli can influence CD8 T cell activation independent of concurrent antigen exposure. The ability to modulate long-term responsiveness of CD8 T cells with a transient, nonspecific inflammatory stimulus has importation implications for adoptive immunotherapy.

Animals↗