Biomedical subjects

Phyllis-Jean Linton

Publications and source records attributed to Phyllis-Jean Linton.

8 recordsLinked to original sources

PubMed2006

Vector prime/protein boost vaccine that overcomes defects acquired during aging and cancer.

We showed that the Ad-sig-TAA/ecdCD40L vaccine induces a tumor suppressive immune response to the hMUC-1 and rH2N tumor-associated self Ags (TAA) and to the Annexin A1 tumor vascular Ag, even in mice in which anergy exists to these Ags. When the TAA/ecdCD40L protein is given s.c. as a boost following the Ad-sig-TAA/ecdCD40L vector, the levels of the TAA-specific CD8 T cells and Abs increase dramatically over that seen with vector alone, in young (2-mo-old) as well as old (18-mo-old) mice. The Abs induced against hMUC-1 react with human breast cancer. This vaccine also induces a 4-fold decrement of negative regulatory CD4CD25FOXP3-T cells in the tumor tissue of 18-mo-old mice. These results suggest that the Ad-sig-TAA/ecdCD40L vector prime-TAA/ecdCD40L protein boost vaccine platform may be valuable in reducing postsurgery recurrence in a variety of epithelial neoplasms.

Aging↗

PubMed2005

Intrinsic versus environmental influences on T-cell responses in aging.

A decline in T-cell responses and a switch to memory T-cell predominance occur with aging. We have used the T-cell receptor (TCR) transgenic mouse model to study age-associated changes in T-cell responses that are a consequence of shifts in subset representation versus changes intrinsic to T cells versus changes in the 'aged' microenvironment. We found that naive transgene-expressing (Tg(+)) CD4(+) T cells from aged mice respond to antigen with reduced interleukin-2 (IL-2) production, decreased cell expansion, and limited differentiation to effectors. Comparable to the characteristic accumulation of memory phenotype T cells in aged humans and conventional rodents, Tg(+) CD4(+) T cells from old OTII and 6.5 TCR transgenic mice acquire a memory phenotype without immunization and become hyporesponsive. The naive Tg(+) CD8(+) T cells from aged 2C mice expressed activation markers, produced IL-2, proliferated, and differentiated into cytotoxic T lymphocytes as efficiently as their young counterparts. Responses by adoptive transferred Tg(+) cells from young mice, immunized in young and old conventional hosts, indicated that the host age influences the onset of cell division, level of cell expansion, and number of cytokine-producing cells. Co-transfer of dendritic cells (DCs) from young and less so from aged conventional mice partially restored responses. Furthermore, DCs and T-cell migration to draining lymphoid organs was reduced due to deficiencies intrinsic to aged cells and the aged environment. Thus, alterations in T-cell responses in aging are attributable to intrinsic and environmental influences.

Aging↗

PubMed2004

Multistep process through which adenoviral vector vaccine overcomes anergy to tumor-associated antigens.

Our goal in the present work was to characterize the multiple steps involved in overcoming the anergy that exists in tumor hosts to tumor-associated antigen (TAA). Our studies showed that the subcutaneous injection of the Ad-sig-TAA/ecdCD40L vector resulted in secretion of the TAA/ecdCD40L protein for at least 10 days from infected cells. Binding of the TAA/ecdCD40L protein to dendritic cells (DCs) resulted in the induction of CCR-7 chemokine receptor expression and cytokine release. This was followed by migration of the DCs to regional lymph nodes. Tetramer staining, enzyme-linked immunospot (ELISPOT) assay, and cytotoxicity assay all showed that the Ad-sig-TAA/ecdCD40L vector increased the levels of splenic CD8(+) T cells specific for the 2 TAAs (human MUC1 [hMUC1] and HPV E7) tested. Vaccination with the Ad-sighMUC1/ecdCD40L vector suppressed the growth of hMUC1 antigen-positive tumor cells in 100% of the test mice that were previously anergic to the hMUC1 antigen. These data suggest that Ad-sig-TAA-ecd/ecdCD40L vector injections may be of value in treating the many epithelial malignancies in which TAA-like hMUC1 is overexpressed.

Adenoviridae↗

PubMed2003

An adenoviral vector cancer vaccine that delivers a tumor-associated antigen/CD40-ligand fusion protein to dendritic cells.

To develop a method to overcome the anergy that exists in tumor hosts to cancer, we have designed an adenoviral vector for the in vivo activation and tumor antigen loading of dendritic cells. This adenoviral vector encodes a fusion protein composed of an amino-terminal tumor-associated antigen fragment fused to the CD40 ligand (CD40L). Subcutaneous injection of an adenoviral vector encoding a fusion protein of the human papillomavirus E7 foreign antigen linked to the CD40L generates CD8+ T cell-dependent immunoresistance to the growth of the E7-positive syngeneic TC-1 cancer cells in C57BL/6 mice for up to 1 year. We also studied the s.c. injection of a vector carrying the gene for the human MUC-1 (hMUC-1) self-antigen fused to the CD40L. When this vector was injected into hMUC-1.Tg mice, which are transgenic for the hMUC-1 antigen, the growth of syngeneic hMUC-1-positive LL1/LL2hMUC-1 mouse cancer cells was suppressed in 100% of the injected animals. The hMUC-1.Tg mice are anergic to the hMUC-1 antigen before the injection of the vector. These experimental results show that it is possible to use vector injection to activate a long-lasting cellular immune response against self-antigens in anergic animals. The vector-mediated in vivo activation, and tumor-associated antigen loading of dendritic cells does not require additional cytokine boosting to induce the immune response against the tumor cells. This vector strategy may therefore be of use in the development of immunotherapy for the many carcinomas in which the hMUC-1 antigen is overexpressed.

Adenoviridae↗

PubMed2003

Costimulation via OX40L expressed by B cells is sufficient to determine the extent of primary CD4 cell expansion and Th2 cytokine secretion in vivo.

The development of effector and memory CD4 cell populations depends upon both T cell receptor (TCR) engagement of peptide/major histocompatibility complex (MHC) class II complexes and ligation of costimulatory molecules with counter receptors on antigen-presenting cells (APCs). We showed previously that sustained interactions with APCs could be crucial for optimal expansion of CD4 cells and for development of effectors that secrete cytokines associated with Th2 cells. Using an adoptive transfer model with TCR transgenic CD4 cells, we now show that responses of CD4 cells primed in B cell-deficient mice become aborted, but are fully restored upon the transfer of activated B cells. Although B cells have the capacity to secrete multiple cytokines that could affect CD4 priming, including IL-4, we were unable to distinguish a role for cytokines that are secreted by B cells. However, B cell costimulation via the OX40L/OX40 pathway that has been implicated in CD4 cell expansion, survival, and Th2 development was required. Th2 but not Th1 responses were impaired in OX40L-deficient recipients and normal responses were restored with OX40L sufficient B cells. The results suggest that without engagement of OX40L on B cells, CD4 cell responses to many protein Ag would be dominated by Th1 cytokines. These data have important implications for strategies to achieve optimal priming of CD4 subsets.

Animals↗

PubMed2003

CD8 T cells and aging.

Aging of the immune system, or "immunosenescence," is associated with both a marked reduction in responsiveness as well as functional dysregulation. These changes have been implicated in the increased morbidity and mortality of the elderly population from infectious disease, and may also play a role in autoimmunity and cancer. Though marginal alterations in B lymphocytes are apparent, the dramatic decline in humoral and cell-mediated responses is predominantly the consequence of alterations in the T-cell compartment. The effect of aging on CD4 cell function has been extensively summarized elsewhere. This review, therefore, focuses on the CD8 T-cell subset. Age-related changes in thymic function and involution, cellular homeostasis and lifespan, population shifts, T-cell activation, the process of replicative senescence, and oligoclonal expansions are discussed in terms of their effect on CD8 T cells. Age-associated alterations in CD4 T cells and antigen-presenting cells are mentioned insofar as these cells affect CD8 T-cell activation and function. Distinct patterns of immunosenescence in humans and mice are also noted.

Aging↗

PubMed2002

Early antigen-specific response by naive CD8 T cells is not altered with aging.

Both a dramatic decline in CD8 responses and a switch to memory T cell predominance occur with aging. The extent to which the loss of responsiveness is the consequence of the accumulation of more differentiated vs intrinsically defective T cells (or both) has been unclear. Using similar conditions of Ag stimulation, we have examined the responses generated by CD8(+) cells isolated from aged TCR transgenic mice. We found that the naive transgene(+) CD8(+) cells from aged 2C mice expressed activation markers, produced IL-2, proliferated, and differentiated into cytotoxic T cells as efficiently as their young counterparts. The extent of responsiveness and the level of the responses were comparable in both age groups regardless of the stimulatory conditions used, i.e., partial costimulation/adhesion molecule expression on APCs, or presentation of lower affinity peptide or diminished peptide concentrations. By day 4 after Ag stimulation, no significant age-related differences were observed in the number of effector cells generated nor in the levels of secreted IL-2 or IFN-gamma. Upon restimulation of effector cells, IL-2 secretion and to a lesser extent TNF-alpha expression, but not IFN-gamma secretion, were diminished with age. These findings suggest that age-associated alterations in naive CD8 cell function are not found after primary stimulation, but may become apparent upon restimulation.

Aging↗

PubMed2002

Availability of antigen-presenting cells can determine the extent of CD4 effector expansion and priming for secretion of Th2 cytokines in vivo.

Like dendritic cells (DC), activated B cells are effective antigen-presenting cells (APC) for naïve CD4 cells due to their expression of MHC class II and multiple costimulatory molecules. We showed previously that CD4 cells primed in B cell-deficient micro MT) mice undergo more limited expansion than in normal animals after immunization with keyhole limpet hemocyanin. Here we report that in the absence of B cells, priming of effectors with the capacity to produce the Th2 cytokines, IL-4, IL-5 and IL-13, was profoundly reduced whereas the development of effectors that secrete the Th1 cytokine IFN-gamma was much less affected. A blockade of IL-12 reduced priming of IFN-gamma-secreting effectors but did not reverse the IL-4, IL-5, or IL-13 deficiency of the response. CD4 cell expansion and priming for Th2 cytokines in micro MT mice was reconstituted by adoptive transfer of activated splenic B cells, which were present throughout the primary response. However, transfer of splenic DC from either control or micro MT mice also supported development of Th2 cytokine responses, indicating that an APC deficit rather than a unique contribution of B cells accounted for diminished effector priming. We conclude that CD4 cell expansion must be sustained via APC for the development of Th2 cytokine-secreting effectors in vivo and that in responses to protein antigen, B cells can be a crucial population to serve in this role. The results suggest that the level of APC engagement can not only determine the extent of effector expansion, but also the overall Th1/Th2 cytokine balance.

Animals↗