Pavelko, Kevin D

Quantitative activity through the TCR-proximal protein network specifies thymic positive versus negative selection.

Abstract Picornaviruses have emerged as promising cancer therapies due to their ability to drive cytotoxic cellular immune responses and for promoting oncolysis. These properties include preferential replication in tumor cells, the induction of strong innate and adaptive immune responses, and the ease with which their genomes can be manipulated. We have developed Theiler's murine encephalomyelitis virus (TMEV) as an immunotherapy vector that promotes strong adaptive immune responses to tumor antigens embedded within its genome. To further explore its usefulness as cancer therapy, we investigated whether direct intratumoral delivery of TMEV could promote tumor regression. We generated several picornavirus hybrids using substrains of TMEV that have unique immunopathologic characteristics, despite their extensive sequence homology. These hybrids exhibit a unique propensity to infect and replicate in melanoma. We have identified GD7-KS1, a virus that is particularly effective at replicating and infecting B16 melanoma in vitro and provides benefit as an oncolytic therapy in vivo after intratumoral injection. In addition, this virus promotes the mobilization and accumulation of CD8+ T cells within treated tumors. Altogether, these findings demonstrate that picornavirus substrains can be used to rationally design virus hybrids that promote antitumor responses and add to the known strategies identified by us and others to further enhance the therapeutic potential of vectors used to treat cancer. Mol Cancer Ther; 15(3); 523–30. ©2016 AACR.

Recombinant virus vaccines are often less effective due to immunodominant responses against endogenous vector antigens. However, the use of small RNA virus vectors provides an opportunity to limit host exposure to endogenous virus antigens and focus immune responses on the desired vaccine antigen. Using the Daniel's strain of Theiler's murine encephalomyelitis virus, we have identified strategies to modulate responses to endogenous viral proteins by manipulating the host CD8+ T-cell repertoire prior to infection or through the use of mutations introduced into the virus genome. Both of these approaches enhance responses to vaccine antigens introduced into the picornavirus. However, the use of mutant immunodominant epitopes provides an opportunity for enhancing vaccine responses without further manipulation of the host. Using this strategy, we demonstrate that modification of the consensus MHC class I anchor residue within the virus genome can promote enhanced immunity to foreign antigens and self-antigens embedded in the virus genome.

Abstract Innate immune effector mechanisms triggered by oncolytic viruses may contribute to the clearance of both infected and uninfected tumor cells in immunocompetent murine hosts. Here, we developed an in vitro tumor cell/bone marrow coculture assay and used it to dissect innate immune sensor and effector responses to intratumoral vesicular stomatitis virus (VSV). We found that the type III IFN interleukin-28 (IL-28) was induced by viral activation of innate immune-sensing cells, acting as a key mediator of VSV-mediated virotherapy of B16ova melanomas. Using tumor variants which differentially express the IL-28 receptor, we showed that IL-28 induced by VSV within the tumor microenvironment sensitizes tumor cells to natural killer cell recognition and activation. These results revealed new insights into the immunovirological mechanisms associated with oncolytic virotherapy in immune-competent hosts. Moreover, they defined a new class of tumor-associated mutation, such as acquired loss of responsiveness to IL-28 signaling, which confers insensitivity to oncolytic virotherapy through a mechanism independent of viral replication in vitro. Lastly, the findings suggested new strategies to manipulate immune signals that may enhance viral replication, along with antitumor immune activation, and improve the efficacy of oncolytic virotherapies. Cancer Res; 70(11); 4539–49. ©2010 AACR.

Abstract Vaccine strategies for cancer immunotherapy have focused on peptide ligands with high affinity for MHC class I. Largely, these vaccines have not been therapeutic. We have examined the peptide specificity of a strongly protective T-cell response that eradicates established B16 melanoma and find that the recognized epitope is generated by a low-affinity MHC class I ligand from tyrosinase-related protein 1 (TRP1). Cytotoxic T-cell responses are induced against TRP1222-229 by several vaccination schemes using a Toll-like receptor agonist, T regulatory cell depletion, or the immune modulator B7-DCXAb to drive immunity. TRP1222 CTL are generated from multiple antigen sources, including antigens expressed by tumors growing in situ, tumor cell lysates, and peptide vaccines. The key finding in this study is that protection from freshly implanted or established B16 tumors is primarily mediated by TRP1222-specific CTL and not by CTL specific for more traditional melanoma antigens such as TRP2 or gp100. This finding challenges the assumption that the optimal peptide antigens for cancer vaccines are high-affinity MHC ligands. We propose that when administered appropriately, native low-affinity MHC ligands are optimal inducers of immunotherapeutic CTL. [Cancer Res 2009;69(7):3114–20]

Abstract Antigenically distinct tumor variants can emerge in response to selective pressures inherent to host-tumor interactions. The development of successful immunotherapeutic strategies can be limited by these disparate antigenic profiles. Using the immunomodulator B7-DC XAb to activate cytolytic T cells specific for tumor-associated antigens, we found that the specificity of immune responses elicited by live tumors are distinct from the specificity of the responses elicited by soluble proteins derived from the same tumors. Remarkably, whereas the induced antitumor immunity generated against live variants of the B16 melanoma and EL4 thymic lymphoma tumors were highly specific for the original tumor variant used in the challenge, immunity generated using soluble proteins derived from tumor lysates was broadly reactive, recognizing the challenge tumor, as well as antigenically distinct variants. The antigens detected using live tumor and tumor lysate vaccines could be distinguished biochemically, demonstrating that they are structurally distinct. We show that vaccines using antigens present in tumor cell lysates induce protective immunity with strong memory against distantly related tumor variants. The existence of a class of antigens shared among tumor variants provides an attractive target for vaccine development. [Cancer Res 2008;68(7):2471–8]

ABSTRACTWe evaluated the participatory role of human HLA-DR molecules in control of virus from the central nervous system and in the development of subsequent spinal cord demyelination. The experiments utilized intracranial infection with Theiler's murine encephalomyelitis virus (TMEV), a picornavirus that, in some strains of mice, results in primary demyelination. We studied DR2 and DR3 transgenic mice that were bred onto a combined class I-deficient mouse (beta-2 microglobulin deficient; β2m0) and class II-deficient mouse (Aβ0) of theH-2bbackground. Aβ0.β2m0mice infected with TMEV died within 18 days of infection. These mice showed severe encephalomyelitis due to rapid replication of virus genome. In contrast, transgenic mice with insertion of a single human class II major histocompatibility complex (MHC) gene (DR2 or DR3) survived the acute infection. DR2 and DR3 mice controlled virus infection by 45 days and did not develop spinal cord demyelination. Levels of virus RNA were reduced in HLA-DR transgenic mice compared to Aβ0.β2m0mice. Virus-neutralizing antibody responses did not explain why DR mice survived the infection and controlled virus replication. However, DR mice showed an increase in gamma interferon and interleukin-2 transcripts in the brain, which were associated with protection. The findings support the hypothesis that the expression of a single human class II MHC molecule can, by itself, influence the control of an intracerebral pathogen in a host without a competent class I MHC immune response. The mechanism of protection appears to be the result of cytokines released by CD4+T cells.

ABSTRACT Epidemiological studies suggest that an environmental factor (possibly a virus) acquired early in life may trigger multiple sclerosis (MS). The virus may remain dormant in the central nervous system but then becomes activated in adulthood. All existing models of MS are characterized by inflammation or demyelination that follows days after virus infection or antigen inoculation. While investigating the role of CD4 + T cell responses following Theiler's virus infection in mice deficient in STAT4 or STAT6, we discovered a model in which virus infection was followed by demyelination after a very prolonged incubation period. STAT4−/− mice were resistant to demyelination for 180 days after infection, but developed severe demyelination after this time point. Inflammatory cells and up‐regulation of Class I and Class II MHC antigens characterized these lesions. Virus antigen was partially controlled during the early chronic phase of the infection even though viral RNA levels remained high throughout infection. Demyelination correlated with the appearance of virus antigen expression. Bone marrow reconstitution experiments indicated that the mechanism of the late onset demyelination was the result of the STAT4−/− immune system. Thus, virus infection of STAT4−/− mice results in a model that may allow for dissection of the immune events predisposing to late‐onset demyelination in MS.

ABSTRACTWe evaluated the role of gamma interferon (IFN-γ) in protecting neurons from virus-induced injury following central nervous system infection. IFN-γ−/−and IFN-γ+/+mice of the resistant major histocompatibility complex (MHC)H-2bhaplotype and intracerebrally infected with Theiler's murine encephalomyelitis virus (TMEV) cleared virus infection from anterior horn cell neurons. IFN-γ+/+H-2bmice also cleared virus from the spinal cord white matter, whereas IFN-γ−/−H-2bmice developed viral persistence in glial cells of the white matter and exhibited associated spinal cord demyelination. In contrast, infection of IFN-γ−/−mice of the susceptibleH-2qhaplotype resulted in frequent deaths and severe neurologic deficits within 16 days of infection compared to the results obtained for controls. Morphologic analysis demonstrated severe injury to spinal cord neurons in IFN-γ−/−H-2qmice during early infection. More virus RNA was detected in the brain and spinal cord of IFN-γ−/−H-2qmice than in those of control mice at 14 and 21 days after TMEV infection. Virus antigen was localized predominantly to anterior horn cells in infected IFN-γ−/−H-2qmice. IFN-γ deletion did not affect the humoral response directed against the virus. However, the level of expression of CD4, CD8, class I MHC, or class II MHC in the central nervous system of IFN-γ−/−H-2qmice was lower than those in IFN-γ+/+H-2qmice. Finally, in vitro analysis of virus-induced death in NSC34 cells and spinal motor neurons showed that IFN-γ exerted a neuroprotective effect in the absence of other aspects of the immune response. These data support the hypothesis that IFN-γ plays a critical role in protecting spinal cord neurons from persistent infection and death.

ABSTRACTWe investigated the role of the immune system in protecting against virus-induced demyelination by generating lines of transgenic B10 (H-2b) congenic mice expressing three independent contiguous coding regions of the Theiler's murine encephalomyelitis virus (TMEV) under the control of a class I major histocompatibility complex (MHC) promoter. TMEV infection of normally resistant B10 mice results in virus clearance and development of inflammatory demyelination in the spinal cord. Transgenic expression of the viral capsid genes resulted in inactivation of virus-specific CD8+T lymphocytes (class I MHC immune function) directed against the relevant peptides, but it did not affect production of virus capsid-specific antibodies or lymphocyte proliferation to the virus antigen (class II MHC immune functions). Following intracerebral infection with TMEV, all three lines of mice survived the acute encephalitis but transgenic mice expressing VP1 (or the cluster of virus capsid proteins [VP4, VP2, and VP3] mapping to the left of VP1 in the TMEV genome) developed virus persistence and subsequent demyelination in spinal cord white matter. Transgenic mice expressing noncapsid proteins mapping to the right of VP1 (2A, 2B, 2C, 3A, 3B, 3C, and 3D) cleared the virus and did not develop demyelination. These results are consistent with the hypothesis that virus capsid gene products of TMEV stimulate class I-restricted CD8+T-cell immune responses, which are important for virus clearance and for protection against myelin destruction. Presented within the context of self-antigens, inactivation of these cells by ubiquitous expression of relevant virus capsid peptides partially inhibited resistance to virus-induced demyelination.