Biomedical subjects

Naeem Khan

Publications and source records attributed to Naeem Khan.

15 recordsLinked to original sources

PubMed2006

Ageing is associated with a decline in peripheral blood CD56bright NK cells.

BACKGROUND: Natural killer (NK) cells are cytotoxic lymphocytes that lack CD3 and express variable levels of CD16, CD56 and CD57. In recent years NK cells have been categorised into two major groups based on the level of CD56 expression. This phenotypic classification correlates with functional activity as CD56bright NK cells are the major cytokine producing subset whereas CD56dim NK cells exhibit greater cytotoxic activity. Previous studies have revealed a reduction in total NK cell numbers in association with ageing and this study sought to determine the potential influence of ageing on the number of NK cell subsets within peripheral blood. RESULTS: The number of NK (CD56+CD3-) cells within peripheral blood did not change with increasing age. The number of CD56dim NK cells also remained stable with ageing. In contrast the absolute number of CD56bright NK cells within peripheral blood declined by 48% with ageing from a mean of 15.6/microl in individuals aged 20-40 years to 8.1/microl in those aged 60+ years (p = 0.0004). CONCLUSION: The number of CD56bright NK cells within peripheral blood declines with age. As this population plays a central role in cytokine secretion during the innate immune response this decline may contribute to impaired immune regulation in elderly individuals.

Journal Article↗

PubMed2005

CD8+ T cells specific for cancer germline gene antigens are found in many patients with multiple myeloma, and their frequency correlates with disease burden.

The expression of cancer germline antigens (CGAgs) is normally restricted to the testis but is also present in many types of malignant cells including plasma cells from patients with myeloma. Because T-cell immune responses to CGAg have been identified in patients with solid tumors, this may offer a novel target for immunotherapy in patients with myeloma. We have used 12 peptide epitopes from a range of CGAgs to screen for CGAg-specific T cells in blood from patients with multiple myeloma at various stages of their disease. T cells from 15 of 37 patients responded to one or more CGAg peptides and the magnitude of the CGAg-specific CD8+ T-cell response ranged between 0.0004% and 0.1% of the total CD8+ T-cell pool. Serial analyses showed that these immune responses were detectable in individual patients at multiple time points during the course of their disease. In patients undergoing treatment or in disease relapse, the magnitude of the CGAg-specific T-cell response was positively correlated with the level of paraprotein. Functional T cells specific for CGAgs are therefore present in a proportion of patients with multiple myeloma and offer the possibility of a novel approach for immunotherapy in this disease.

Adult↗

PubMed2005

Tonsillar homing of Epstein-Barr virus-specific CD8+ T cells and the virus-host balance.

Patients with infectious mononucleosis (IM) undergoing primary EBV infection show large expansions of EBV-specific CD8+ T cells in the blood. While latent infection of the B cell pool is quickly controlled, virus shedding from lytically infected cells in the oropharynx remains high for several months. We therefore studied how responses localize to the tonsil, a major target site for EBV, during primary infection and persistence. In acute IM, EBV-specific effectors were poorly represented among CD8+ T cells in tonsil compared with blood, coincident with absence of the CCR7 lymphoid homing marker on these highly activated cells. In patients who had recently recovered from IM, latent epitope reactivities were quicker than lytic reactivities both to acquire CCR7 and to accumulate in the tonsil, with some of these cells now expressing the CD103 integrin, which mediates retention at mucosal sites. By contrast, in long-term virus carriers in whom both lytic and latent infections had been controlled, there was 2- to 5-fold enrichment of lytic epitope reactivities and 10- to 20-fold enrichment of latent epitope reactivities in tonsil compared with blood; up to 20% of tonsillar CD8+ T cells were EBV specific, and many now expressed CD103. We suggest that efficient control of EBV infection requires appropriate CD8+ T cell homing to oropharyngeal sites.

Antigens, CD↗

PubMed2005

Adoptive transfer of cytomegalovirus-specific CTL to stem cell transplant patients after selection by HLA-peptide tetramers.

Stem cell transplantation is used widely in the management of a range of diseases of the hemopoietic system. Patients are immunosuppressed profoundly in the early posttransplant period, and reactivation of cytomegalovirus (CMV) remains a significant cause of morbidity and mortality. Adoptive transfer of donor-derived CMV-specific CD8+ T cell clones has been shown to reduce the rate of viral reactivation; however, the complexity of this approach severely limits its clinical application. We have purified CMV-specific CD8+ T cells from the blood of stem cell transplant donors using staining with HLA-peptide tetramers followed by selection with magnetic beads. CMV-specific CD8+ cells were infused directly into nine patients within 4 h of selection. Median cell dosage was 8.6 x 10(3)/kg with a purity of 98% of all T cells. CMV-specific CD8+ T cells became detectable in all patients within 10 d of infusion, and TCR clonotype analysis showed persistence of infused cells in two patients studied. CMV viremia was reduced in every case and eight patients cleared the infection, including one patient who had a prolonged history of CMV infection that was refractory to antiviral therapy. This novel approach to adoptive transfer has considerable potential for antigen-specific T cell therapy.

Adoptive Transfer↗

PubMed2005

Virus-specific cytotoxic T lymphocytes differentially express cell-surface leukocyte immunoglobulin-like receptor-1, an inhibitory receptor for class I major histocompatibility complex molecules.

Leukocyte immunoglobulin-like receptor-1 (LIR-1) is an inhibitory receptor that negatively regulates T cell effector functions after interaction with host class I major histocompatibility complex molecules and, additionally, binds to UL18, a human cytomegalovirus (HCMV)-encoded class I homologue. Here, we demonstrate that virus-specific cytotoxic T lymphocytes (CTLs) differentially express LIR-1, with high frequencies of expression on HCMV-specific CD8+ T cells and intermediate and low frequencies of expression on influenza virus-specific and Epstein-Barr virus (EBV)-specific CTLs, respectively. Expression of LIR-1 was dependent on CTL-antigen specificity and was associated with a differentiated effector memory phenotype, as demonstrated by decreased expression of CD28 and increased expression of CD57. During primary HCMV and EBV infections, expression of LIR-1 on virus-specific CTLs was low and increased slowly. These results indicate that expression of LIR-1 increases during differentiation of virus-specific CD8+ effector T cells. Furthermore, they suggest that a potential immunoregulatory function of UL18 may be to preferentially target highly differentiated HCMV-specific effector memory T cells during persistent infection.

Antigens, CD↗

PubMed2005

The impact of telomere erosion on memory CD8+ T cells in patients with X-linked lymphoproliferative syndrome.

Patients with X-linked lymphoproliferative syndrome (XLP) experience excessive T cell proliferation after primary Epstein-Barr virus (EBV) infection, due to mutations in the signalling lymphocyte activation molecule (SLAM) associated protein (SAP) molecule. We examined the impact of dysfunctional proliferative control on the extent of CD8+ T cell differentiation in XLP patients who recovered from primary EBV infection. Although these young patients have normal numbers of lytic and latent EBV-epitope-specific CD8+ T cells, they were extremely differentiated as defined by loss of CCR7 and CD27, low telomerase activity and very short telomeres. This was not a direct effect arising from the loss of SAP, but was due to excessive T cell stimulation due to this defect. Thus, transduction of XLP CD8+ T cells with the catalytic component of telomerase (hTERT), but not SAP, prevented telomere loss and considerably extended proliferative lifespan in vitro. These results indicate that excessive proliferation in CD8+ T cells in XLP patients may lead to end-stage differentiation and loss of functional EBV-specific CD8+ T cells through replicative senescence. This may contribute to the defective immunity found in XLP patients who survive acute EBV infection who develop EBV-related B cell lymphomas before the fourth decade of life.

Adult↗

PubMed2005

HIV patients on antiretroviral therapy have high frequencies of CD8 T cells specific for Immediate Early protein-1 of cytomegalovirus.

OBJECTIVE: To assess the frequency and phenotype of cytomegalovirus (CMV)-specific CD8 T cells in previously immunocompromised HIV patients with stable undetectable HIV viremia due to highly active antiretroviral therapy (HAART). METHODS: Twenty-one CMV-seropositive HIV patients with nadir CD4 T-cell counts < 50 x 10(6) cells/l, at least 4 years on HAART and 6 months of complete viral suppression (< 50 HIV RNA copies/ml) and 12 CMV-seropositive, HIV-seronegative age/sex-matched controls were studied. CD4 and CD8 T-cell responses to whole CMV and two HLA-A*02 restricted CMV peptides [NLV from pp65 and VLE from Immediate Early 1 (IE1)] were measured by interferon (IFN)gamma ELISpot. Phenotypes of peptide-specific CD8 T cells were determined by tetramer staining. RESULTS: In the ELISpot assay, HIV patients had significantly more CD8 T cells producing IFN gamma in response to VLE than controls, whereas numbers of NLV-specific and CMV-specific IFN gamma spots were similar. Four HIV patients and one control had large VLE and/or NLV-specific CD8 T-cell populations despite the absence of CMV-specific CD4 T cells. The majority of peptide-specific CD8 T cells from HIV patients and controls were CD28-, CD45RO+ and CD45RA-. However, a significantly higher proportion of VLE-specific CD8 T cells expressed perforin compared to NLV-specific CD8 T cells in HIV patients. CONCLUSIONS: HIV patients had elevated numbers of IE1-specific, IFNgamma-producing perforin-positive CD8 T cells compared to controls. As IE1 is expressed early during CMV reactivation, these cells may be important for preventing CMV replication to pathogenic levels. In addition, CMV-specific CD4 T cells are not essential for maintenance of large populations of CMV-specific CD8 T cells in aviremic HIV patients on HAART.

Adult↗

PubMed2005

Identification of cytomegalovirus-specific cytotoxic T lymphocytes in vitro is greatly enhanced by the use of recombinant virus lacking the US2 to US11 region or modified vaccinia virus Ankara expressing individual viral genes.

Cytomegalovirus (CMV) elicits a potent T-cell response in humans that appears to protect the host from virus-associated disease. Despite facing strong host defense mechanisms, CMV remains as a lifelong infection that may reactivate and cause life-threatening disease in immunocompromised individuals. This persistence is probably assisted by expression of immune subversion proteins of the virus encoded by genes belonging to the US gene family. These proteins modulate major histocompatibility complex expression in infected cells and bias in vitro experiments toward the detection of only certain specificities. We have combined the use of recombinant CMV, lacking the US2 to US11 region genes, and cytoplasmic gamma interferon staining to define a more accurate assessment of CMV-specific responses in vivo. Recombinant CMV stimulation reveals a CD8 response much larger than that of parental virus in all donors tested. In some cases, this represented up to 10-fold increases in the number of cells detected. Responses were directed mainly against pp65, IE-1, and pp50 in the majority of donors. In addition, previously unreported IE-2-specific T-cell responses could be detected in a minority of cases. Furthermore, we observed a less marked increase in the response to mutant CMV by CD4 T cells in some donors. This suggests that a much broader T-cell response to CMV exists in vivo than is revealed by restimulation with wild-type virus and adds to the evidence that the efficacy of immune evasion strategies may not be as absolute as previously believed.

Base Sequence↗

PubMed2004

Herpesvirus-specific CD8 T cell immunity in old age: cytomegalovirus impairs the response to a coresident EBV infection.

Aging in humans is associated with increased infections and the reduced proliferative capacity of T cells, part of the more global phenomenon termed immune senescence. The etiology of immune senescence is unknown but the accumulation of virus-specific memory T cells may be a contributory factor. We have examined CD8 T cell responses to two persistent herpesvirus infections, CMV and EBV, and to a recurrent virus infection, influenza, in different age cohorts of healthy donors using HLA-peptide tetramers and intracellular cytokine detection. Of these, CMV appears to be the most immunogenic, with the CD8 T cell response representing over 10% of the CD8 pool in many elderly donors. Interestingly, the effect of age upon EBV-specific responses depends upon donor CMV sero-status. In CMV seropositive donors, the magnitude of the EBV-specific immune response is stable with age, but in CMV seronegative donors, the response to EBV increases significantly with age. By contrast, the influenza-specific CD8 T cell immune response decreases with age, independent of CMV status. The functional activity of the herpesvirus-specific immune response decreases in elderly donors, although the characteristic phenotypes of CMV- and EBV-specific memory populations are retained. This demonstrates that aging is associated with a marked accumulation of CMV-specific CD8 T cells together with a decrease in immediate effector function. Moreover, infection with CMV can reduce prevailing levels of immunity to EBV, another persistent virus. These results suggest that carriage of CMV may be detrimental to the immunocompetent host by suppressing heterologous virus-specific immunity during aging.

Adult↗

PubMed2003

Adoptive cellular therapy for early cytomegalovirus infection after allogeneic stem-cell transplantation with virus-specific T-cell lines.

Adoptive transfer of CMV-specific T cells offers the potential for reconstitution of viral immunity after allogeneic transplantation. However, the logistics of producing virus-specific T-cell clones has limited the application of cellular therapies. We treated 16 patients for CMV infection with polyclonal CMV-specific T-cell lines generated by short-term culture. Massive in-vivo expansions of CMV-specific cytotoxic T lymphocytes were observed, resulting in reconstitution of viral immunity. In eight cases antiviral drugs were not required, and subsequent episodes of reactivation occurred in only two patients. Our findings indicate that application of CMV-specific cell lines is both feasible and effective in a clinical environment.

Adoptive Transfer↗

PubMed2003

Palliative surgery for advance osteosarcoma of shoulder region.

We are presenting here eight cases of advanced osteosarcoma of shoulder region involving scapula and upper humerus in children upto the age of thirteen years. All patients had complete loss of movement. Five patients underwent fore quarter amputation. Extensive amputation although a major mutilating procedure, provides patients a dramatic relief for the period that he survives.

Adolescent↗

PubMed2003

Reconstitution of T-cell repertoire after autologous stem cell transplantation: influence of CD34 selection and cytomegalovirus infection.

The period of immunodeficiency following autologous hematopoietic stem cell transplantation is characterized by transient expansions of CD8+CD45RO+CD57+ T lymphocytes, displaying markers of an activated phenotype. Most evidence suggests that this early reconstitution results from proliferation of mature T cells that have survived conditioning or were transferred with the graft. Although homeostatic mechanisms are thought to act in maintaining total T-cell numbers, the degree to which antigen-driven expansions contribute and the nature of the stimulating antigens remain unclear. CD34 selection of stem cell grafts reduces the available T-cell pool, potentially delaying immune reconstitution and resulting in increased infective complications. In the allogeneic transplantation setting, lymphopenia has been associated with cytomegalovirus (CMV) infection risk and, if persistent, with adverse outcome. We prospectively studied patients undergoing CD34-selected (n = 13) or unselected (n = 13) autologous hematopoeitic stem cell transplantation for immune reconstitution and CMV infection. No significant differences were demonstrated between graft types with respect to lymphocyte subset recovery, T-cell receptor beta-chain variable region spectratype diversity, or CMV DNA detection rates (45% versus 40%). CMV infection was associated with a trend toward higher rather than lower CD8+ counts at 6 weeks posttransplantation (P =.08) that became significant by 3 months (P=.007), and that was associated with decreased T-cell receptor beta-chain variable region spectratype diversity (P =.01). CMV-specific HLA-tetramer analysis demonstrated transient expansions with CDR3 lengths corresponding to those of some of the major posttransplantation T-cell expansions demonstrated by spectratype analysis suggesting that CMV-specific T cells contribute to the pattern of immune reconstitution.

Adult↗

PubMed2002

B cells immortalized by a mini-Epstein-Barr virus encoding a foreign antigen efficiently reactivate specific cytotoxic T cells.

Lymphoblastoid cell lines (LCLs) are human B cells latently infected and immortalized by Epstein-Barr virus (EBV). Presenting viral antigens, they efficiently induce EBV-specific T-cell responses in vitro. Analogous ways to generate T-cell cultures specific for other antigens of interest are highly desirable. Previously, we constructed a mini-EBV plasmid that consists of less than half the EBV genome, is unable to cause virus production, but still immortalizes B cells in vitro. Mini-EBV-immortalized B-cell lines (mini-LCLs) are efficiently produced by infection of B cells with viruslike particles carrying only mini-EBV DNA. Mini-EBV plasmids can be engineered to express an additional gene in immortalized B cells. Here we present a mini-EBV coding for a potent CD8(+) T-cell antigen, the matrix phosphoprotein pp65 of human cytomegalovirus (CMV). By means of this pp65 mini-EBV, pp65-expressing mini-LCLs could be readily established from healthy donors in a one-step procedure. We used these pp65 mini-LCLs to reactivate and expand effector T cells from autologous peripheral blood cells in vitro. When generated from cytomegalovirus (CMV)-seropositive donors, these effector T-cell cultures displayed strong pp65-specific HLA-restricted cytotoxicity. A large fraction of CD8(+) T cells with pp65 epitope specificity was present in such cultures, as demonstrated by direct staining with HLA/peptide tetramers. We conclude that the pp65 mini-EBV is an attractive tool for CMV-specific adoptive immunotherapy. Mini-EBVs could also facilitate the generation of T cells specific for various other antigens of interest.

Antigens, Viral↗

PubMed2002

Cytomegalovirus seropositivity drives the CD8 T cell repertoire toward greater clonality in healthy elderly individuals.

The deterioration in immune function with aging is thought to make a major contribution to the increased morbidity and mortality from infectious disease in old age. One aspect of immune senescence is the reduction in CD8 T cell repertoire as due to the accumulation of oligoclonal, memory T cells and a reduction in the naive T cell pool. CD8 T cell clonal expansions accumulate with age, but their antigenic specificity remains unknown. In this study, we show that in elderly individuals seropositivity for human CMV leads to the development of oligoclonal populations of CMV-specific CTL that can constitute up to one-quarter of the total CD8 T cell population. Furthermore, CMV-specific CTL have a highly polarized membrane phenotype that is typical of effector memory cells (CD28(-), CD57(+), CCR7(-)). TCR analyses show that CMV-specific CTL have highly restricted clonality with greater restriction in the larger expansions. Clonal analysis of the total CD8 T cell repertoire was compared between CMV-seropositive and CMV-seronegative donors. Thirty-three percent more clonal expansions were observed in CMV-seropositive donors in comparison with seronegative individuals. These data implicate CMV as a major factor in driving oligoclonal expansions in old age. Such a dramatic accumulation of virus-specific effector CTL might impair the ability to respond to heterologous infection and may underlie the negative influence of CMV seropositivity on survival in the very elderly.

Aged↗

PubMed2002

Comparative analysis of CD8+ T cell responses against human cytomegalovirus proteins pp65 and immediate early 1 shows similarities in precursor frequency, oligoclonality, and phenotype.

CD8+ T cells are key effectors of the immune response against human cytomegalovirus (HCMV). A number of HCMV-derived CD8+ T cell epitopes are known. Using epitope prediction and subsequent testing for interferon-gamma responses by the ELISPOT assay, we identified an optimal human leukocyte antigen (HLA)-A*0201-restricted CD8+ T cell epitope derived from the major immediate early 1 (IE-1) gene product. As many as one-third of HLA-A*0201-positive, HCMV-seropositive donors make responses to this peptide (residues 316-324 [VLEETSVML]), which can exceed responses against a published immunodominant pp65 epitope (residues 495-503 [NLVPMVATV]). Major histocompatibility complex peptide tetramer staining facilitated detailed phenotypic analyses and revealed populations that resemble terminally differentiated effector cells (CD57+ and CD28-), with considerable restriction in T cell receptor beta-chain variable region use. The results confirm that, although pp65 is a major target for CD8+ T cells, the IE-1 protein may itself stimulate comparable responses in some persons.

Antigens, Viral↗