Robert L. Yauch

Preferential Induction of IL-10 in APC Correlates with a Switch from Th1 to Th2 Response Following Infection with a Low Pathogenic Variant of Theiler’s Virus

Theiler’s murine encephalomyelitis virus induces immune-mediated demyelination in susceptible mice after intracerebral inoculation. A naturally occurring, low pathogenic Theiler’s murine encephalomyelitis virus variant showed a single amino acid change within a predominant Th epitope from lysine to arginine at position 244 of VP1. This substitution is the only one present in the entire viral capsid proteins. In this paper, we demonstrate that the majority of T cells specific for VP1233–250 and VP274–86 from wild-type virus-infected mice are Th1 type and these VP1-specific cells poorly recognize the variant VP1 epitope (VP1K244R) containing the substituted arginine. In contrast, the Th2-type T cell population specific for these epitopes predominates in variant virus-infected mice. Immunization with UV-inactivated virus or VP1 epitope peptides could not duplicate the preferential Th1/Th2 responses following viral infection. Interestingly, the major APC populations, such as dendritic cells and macrophages, produce IL-12 on exposure to the pathogenic wild-type virus, whereas they preferentially produce IL-10 in response to the low pathogenic variant virus. Thus, such a spontaneous mutant virus may have a profoundly different capability to induce Th-type responses via selective production of cytokines involved in T cell differentiation and the consequent pathogenicity of virally induced immune-mediated inflammatory diseases.

Effect of immunization with Theiler's virus on the course of demyelinating disease

Intracerebral (i.c.) inoculation of susceptible mice with Theilers murine encephalomyelitis virus (TMEV) results in a demyelinating disease similar to human multiple sclerosis (MS). Mice develop a strong immune response to TMEV and the disease is believed to be immune-mediated. In order to investigate the effects of the immune response to TMEV on the course of demyelination, we immunized host mice with UV-inactivated TMEV at various time periods in relation to intracerebral inoculation with live TMEV. Here, we show that subcutaneous immunization of mice with TMEV prior to infection with virus is able to protect susceptible, SJL/J mice from demyelinating disease. This protective effect appears to be long-lasting; immunization greater than 90 days prior to i.c. inoculation of the virus protects mice from subsequent infection. However, immunization of mice after i.c. infection with TMEV does not confer protection, but rather exacerbates the disease symptoms. Thus, this system offers a model for studying viral capsid proteins and/or epitopes which are involved in either protection from disease or immune-mediated pathogenesis leading to myelin destruction in susceptible mice.

B cell lymphomas of C57l/J mice; the role of natural killer cells and T helper cells in lymphoma development and growth

The Hodgkins-like Type B neoplasms which arise spontaneously in aging C57L mice (25% incidence at 21 months of age) were first reported over 40 years ago, but since then relatively little has been published about these lymphomas. Based on previous studies in SJL mice, we investigated the phenotypic and functional properties of C57L-derived lymphomas in relation to Mtv29-encoded vSAg expression by the tumor cells, and their ability to stimulate TCR Vbeta-restricted T cells. The cell surface phenotype of the C57L lymphomas indicates a B cell origin (sIg(+), MHC II(+)). These B lymphoma cells also express co-stimulatory molecules [B7-1 (CD80) and HSA (CD24)], and stimulate marked proliferation of syngeneic CD4(+) T cells. C57L B lymphoma cells exhibit Mtv-encoded mRNA by northern analysis, and also stimulate IL-2 production from Vbeta16(+) T cell hybrids, suggesting a role for Mtv 29 in this syngeneic T cell response. After transfer to syngeneic recipients, primary C57L lymphomas grow slowly, if at all. However, tumor growth is greatly accelerated by pretreatment of C57L recipients with anti-asialo GM1 antibody (but not anti-CD8 mAb), suggesting that NK cells play a major role in inhibiting lymphoma growth. If, in addition to anti-asialo GM1, the mice are also pretreated with anti-CD4 mAb, tumor growth is markedly inhibited, indicating that the lymphoma-responsive syngeneic CD4(+) T cells promote tumor growth. Therefore, although the vSAg-induced response stimulated by vSAg29 expressing lymphoma cells in syngeneic TCR Vbeta-restricted CD4(+) T cells is an important etiologic factor in this type of B cell neoplasm both in C57L and in SJL mice, the final outcome of the spontaneous neoplastic process appears strongly influenced by endogenous NK activity in aging mice.

Analysis of T cell epitope specificity differentiating pathogenic and non-pathogenic Theiler's murine encephalomyelitits virus

Introduction: lntracerebral inoculation of snsceptible strains of mice with Thcilcrs murine encephalomyelitis virus (TMEV) results in immune-mediated demyelination. Like other picornaviruses, TMEV consists of only 4 viral capsid proteins. Based on studies with other picornavirusos, VPI appears to be the most important for viral pathogenesis and protective immunity to the viruses. Materials and Methods: Standard methods were used for T cell cloning, selection of T cell hybridomas, T cell proliferation, and plaque isolation of virus clones. GST-fusion proteins and synthetic pcptidcs wcr¢ also used. Results: We have identified a major T cell epitop¢ and defined the region within the VP1 protein based on the rcactivities ofT cell clones derived from dcmyelinating spinal cords of virus-infected SJL mice. Interestingly, these VPIreactive clones recognizing the region of VP1233.2s o did not recognize a spomancousiy mutated virus (M2) displaying extremely low-pathogenicity. Our preliminary results indicate that the mutant virus has a single base alteration leading to a lysine --~ arginine substitution within the T cell epitop¢. Conclusions: We believe that this VPI T cell epitopc may play an important role in the pathogenesis of viral demyelinating disease. (Supported by NIH grants, NS28752 and NS33008)