Importance of MUC1 and spontaneous mouse tumor models for understanding the immunobiology of human adenocarcinomas.

Many important aspects of cancer biology, such as cancer initiation, progression, and metastasis, have been studied in animal models, mostly mice. As long as cancer was considered primarily a genetic disease, the study of transplantable mouse tumors, or even human tumor xenografts in immunocompromised mice, appeared to suffice. Many important genetic events that lead to transformation and in vivo tumor growth were elucidated. However, many even more important factors that determine whether or not the genetic potential of a tumor cell will be realized, such as the host response to the tumor and the tumor microenvironment that influences this response over a long period of time of tumor development, remained untested and unappreciated. This is slowly changing with the advent of molecular techniques that have spurred efforts to engineer better mouse models of human tumors. In this review, we show results of our efforts to combine a genetic mouse model of spontaneous human adenocarcinomas based on a Kras mutation, with an important human molecule MUC1 that is abnormally expressed on human adenocarcinomas, promoting oncogenesis, proinflammatory tumor microenvironment, and immunosurveillance.

Early CD4(+) T cell help prevents partial CD8(+) T cell exhaustion and promotes maintenance of Herpes Simplex Virus 1 latency.

HSV-specific CD8(+) T cells provide constant immunosurveillance of HSV-1 latently infected neurons in sensory ganglia, and their functional properties are influenced by the presence of latent virus. In this study, we show that ganglionic HSV-specific CD8(+) T cells exhibit a higher functional avidity (ability to respond to low epitope density) than their counterparts in noninfected lungs, satisfying a need for memory effector cells that can respond to low densities of viral epitopes on latently infected neurons. We further show that lack of CD4(+) T cell help during priming leads to a transient inability to control latent virus, which was associated with a PD-1/PD-L1 mediated reduced functional avidity of ganglionic HSV-specific CD8(+) T cells. CD4(+) T cells are not needed to maintain CD8(+) T cell memory through 34 d after infection, nor do they have a direct involvement in the maintenance of HSV-1 latency.

A phase I/II study of a MUC1 peptide pulsed autologous dendritic cell vaccine as adjuvant therapy in patients with resected pancreatic and biliary tumors.

Pancreatic and biliary cancers are relatively resistant to chemotherapy and radiation and may therefore provide an opportunity for testing the potential of immunotherapy. MUC1 is an epithelial cell glycoprotein that is highly overexpressed and aberrantly glycosylated in many adenocarcinomas, including pancreatic tumors, providing a tumor specific antigen and target. We performed a Phase I/II clinical trial of a MUC1 peptide-loaded DC vaccine in 12 pancreatic and biliary cancer patients following resection of their primary tumors. The primary endpoints were vaccine toxicity and immunogenicity and the secondary endpoint was clinical outcome. The vaccine was well tolerated and no toxicity was observed. Three patients had pre-existing MUC1 antibody responses that remained stable post vaccination. MUC1-specific T cell responses were difficult to evaluate due to increases in activity of all CD8 and CD4 T cells following each vaccination. Prior to vaccination, patients entered onto this trial had a significantly higher percentage of FoxP3+CD4+ T cells compared to age matched healthy controls. The percentage of these cells also increased transiently following each injection, returning to baseline or below before the next injection. Vaccinated patients have been followed for over four years and four of the twelve patients are alive, all without evidence of recurrence. Study of the immune parameters in long-term survivors several years after vaccination may yield the sought after immune correlates of clinical responses that analysis of immune responses shortly after vaccination has not revealed.

How herpes simplex virus type 1 rescinds corneal privilege.

Properties of the cornea such as a lack of blood and lymphatic vessels, a lack of professional antigen-presenting cells, and exposure to immunosuppressive factors in the aqueous humor contribute to a relative state of immune privilege. Ironically, corneal damage and the accompanying visual morbidity following herpes simplex virus type 1 (HSV-1) infection does not results from uncontrolled viral replication, but from an immunoinflammatory process referred to as herpes stromal keratitis (HSK). This review highlights changes in the immune-privileged status of the cornea following HSV-1 infection that contribute to HSK.

Expression and function of the OX40/OX40L costimulatory pair during herpes stromal keratitis.

Herpes stromal keratitis (HSK) is an immunopathological disease regulated by Th1 CD4 T cells, which require APC and costimulation within the infected cornea to mediate disease. Recent studies suggest the OX40:OX40 ligand (OX40L) interaction enhances effector cell cytokine secretion at inflammatory sites. OX40(+) cells were detected in HSV-1-infected mouse corneas as early as 3 days postinfection (dpi), prior to the onset of HSK, and their frequency increased through 15 dpi, when all mice exhibited severe HSK. OX40L(+) cells were first detected at 7 dpi, coincident with the initiation of HSK. It is interesting that the OX40L(+) cells did not coexpress MHC Class II or the dendritic cell (DC) marker CD11c. Our findings demonstrate rapid infiltration of activated (OX40(+)) CD4(+) T cells into HSV-1-infected corneas and expression of OX40L on MHC Class II-negative cells but surprisingly, not on MHC Class II(+) CD11c(+) DC, which are present in the infected corneas and required for HSK. Moreover, neither local nor systemic treatment of mice with a blocking antibody to OX40L or with a blocking fusion protein altered the course of HSK significantly, possibly as a result of a lack of OX40L expression on functional APC.

CD8 T cells mediate transient herpes stromal keratitis in CD4-deficient mice.

PURPOSE: To evaluate the role of CD4(+) T cells in the development of murine herpes stromal keratitis (HSK). METHODS: The corneas of wild-type (WT) BALB/c mice and three types of CD4-deficient BALB/c mice (CD4(-/-), CD4-depleted, CD4 and CD8 double-depleted) were infected with different doses of HSV-1 RE, and HSK incidence and severity were monitored. Corneal infiltrates were quantitatively and functionally assayed by flow cytometric analysis of individually digested diseased corneas and documented histologically. RESULTS: At a relatively high infectious dose (1 x 10(5) pfu/cornea): (1) CD4-deficient and WT BALB/c mice had severe HSK with a similar incidence (80%-100%), whereas HSK did not develop in mice deficient in both CD4(+) and CD8(+) T cells; (2) neutrophils were the predominate leukocyte in the corneas of CD4-deficient and WT mice; (3) the corneas of WT mice had activated, HSV-1-specific CD4(+) T cells, but few if any CD8(+) T cells; (4) the corneas of CD4-deficient mice had activated, HSV-1-specific CD8(+) T cells; and (5) HSK in CD4-deficient mice was transient, showing loss of CD8(+) T cells at 2 to 3 weeks after infection (pi) followed by a loss of neutrophils. At a relatively low infectious dose of HSV-1 (10(3) pfu/cornea) severe HSK developed in 80% to 90% of WT mice, but in only 30% to 40% of CD4-deficient mice. CONCLUSIONS: CD4(+) T cells preferentially mediate HSK, but, in their absence, a high infectious dose of HSV-1 can induce histologically similar but transient HSK that is mediated by CD8(+) T cells.

CD154 signaling regulates the Th1 response to herpes simplex virus-1 and inflammation in infected corneas.

Approximately 7 days after HSV-1 corneal infection, BALB/c mice develop tissue-destructive inflammation in the cornea termed herpes stromal keratitis (HSK), as well as periocular skin lesions that are characterized by vesicles, edema, and fur loss. CD4(+) T cells and Th1 cytokines contribute to both the immunopathology in the cornea and the eradication of viral replication in the skin. We demonstrate that disruption of CD40/CD154 signaling does not impact the initial expansion of CD4(+) T cells in the draining lymph nodes, but dramatically reduces the persistence and Th1 polarization of these cells. Despite the reduced Th1 response, CD154(-/-) mice developed HSK and periocular skin disease with similar kinetics and severity (as assessed by clinical examination) as wild-type (WT) mice. However, when the composition of the inflammatory infiltrate was examined by flow cytometric analysis, CD154(-/-) mice exhibited significantly fewer CD4(+) and CD8(+) T cells and neutrophils than WT mice at the peak of HSK. Moreover, CD4(+) T cells from infected corneas of CD154(-/-) mice produced significantly less IFN-gamma than those of WT mice when stimulated with viral Ags in vitro. The IFN-gamma production of cells from infected corneas of WT mice was not affected by addition of anti-CD154 mAb to the stimulation cultures. This suggests that CD154 signaling is required at the inductive phase, but not at the effector phase, of the Th1 response within the infected cornea. We conclude that local disruption of CD40/CD154 signaling is not likely to be a useful therapy for HSK.

Immune control of herpes simplex virus during latency.

Herpes simplex virus type 1 (HSV-1) persists within the host in the presence of concomitant immunity by establishing a latent infection within sensory neurons. HSV-1 latency is widely viewed as a neuron-enforced quiescent state of the virus, in which a lack of viral protein synthesis prevents recognition of the infected neuron by the host immune system. On the basis of recent findings, however, we propose a more dynamic view of HSV-1 latency characterized by persistent or intermittent low-level viral gene expression in some latently infected neurons. We further propose that HSV-1-specific memory/effector CD8(+) T lymphocytes that are retained in the ganglion in close apposition to the neurons prevent full reactivation and virion formation through IFN-gamma production and an additional undefined mechanism(s).

Co-stimulatory requirements of effector T cells at inflammatory sites.

There is a growing appreciation of the importance of T cell costimulation at inflammatory sites. Here, we briefly review the literature on the subject, and describe recent pertinent findings in our model of herpes simplex keratitis.

Identification of a novel macrophage population in the normal mouse corneal stroma.

PURPOSE: To examine the normal murine corneal stroma for the presence of bone marrow-derived leukocytes. METHODS: Wholemounts of paraformaldehyde-fixed corneal stroma from normal mice at 5 to 16 weeks of age were examined in single- and double-color immunomorphologic studies performed with confocal microscopy. The phenotype, morphology, distribution, and density of immunopositive cells were determined. RESULTS: Numerous CD45(+) cells with pleomorphic and dendriform morphology were found within the pericentral and central region of the corneal stroma (200-300 cells/mm(2)). Dual-color immunostaining demonstrated that 100% of the CD45(+) cells coexpressed CD11b and 50% coexpressed F4/80. Approximately 30% of the total cells and 50% of the F4/80(+) cells coexpressed major histocompatibility complex (MHC) class II antigens. Very small to negligible numbers of cells expressed markers of dendritic cells (CD11c) or granulocytes (Ly6G). Markers for T-cells and NK cells were absent from the corneal stroma, indicating that all the cells identified in the stroma were of the myeloid lineage. CONCLUSIONS: The normal murine corneal stroma contains a significant number of CD45(+) leukocytes. Most these cells express the CD11b marker, but not other dendrite, granulocyte, T-cell, or NK markers, placing them in the monocyte/macrophage lineage.