Robert S. Fujinami

Is Theiler's murine encephalomyelitis virus infection of mice an autoimmune disease?

Viruses can initiate disease by many different means. Direct viral, immune mediated and host factors all play important parts. Molecular mimicry or having cross‐reacting determinants that result in immune responses which have the potential to cause damage can be incorporated into this framework. Here, autoimmune responses generated by virus infection have been presented in relation to these other parameters. The cross‐reacting immune response originally generated by virus would have to be directed toward or involve a disease inducing site such as an EAE (encephalitogenic), thyroiditis, or diabetogenic site. If the cross‐reaction took place at a nondisease inducing site, the ensuring immune response may result in the production of autoantibodies, however no disease would occur. In other systems autoantibodies can potentiate an ongoing inflammatory response. This may be the case that is described here with Theilers murine encephalomyelitis virus infection. Lastly, viruses having common determinants with MHC determinants may modify immune responses leading to immunosuppression and allowing virus to persist. In addition, similar determinants may lead to disease by an alternative route. For example, we have described a region of human cytomegalovirus that has a common determinant with HLA DR beta chain. This region is associated with diabetes in humans (Todd et al. 1988). Thus, many factors are involved in the outcome of disease induction by viruses of which autoimmunity is one.

Monoclonal antibody defines determinant between Theiler's virus and lipid-like structures ☆

Theilers murine encephalomyelitis virus is known to cause a chronic demyelinating disease in mice. The contributions of immunologic factors, i.e. humoral and cellular responses to virus and/or myelin components, and direct virus-cell interactions leading to demyelination are still unclear. One important factor could be antibody initiation of myelin destruction. Here we describe four monoclonal antibodies that react with Theilers murine encephalomyelitis virus. Three of these neutralize the virus and one of these three could also bind to various lipid-like structures including galactocerebroside, a myelin component. Further, this monoclonal antibody reacted with oligodendrocyte-like cells in vitro. All four monoclonal antibodies reacted with VP-1 by Western blot analysis. Thus, an immune response generated by virus that cross-reacts with a myelin element such as galactocerebroside could play a role in directing autoimmune processes toward myelin destruction.

Purification of measles virus glycoproteins and their integration into artificial lipid membranes.

We report a simple method for the isolation of the measles virus glycoproteins, and their subsequent incorporation into artificial lipid bilayers. The two viral glycoproteins, HA and F, were isolated in preparative amounts from disrupted purified virus by lentil lectin affinity chromatography. The proteins were reconstituted into single bilayer lipid vesicles by: (i) exchanging the non-dialysable detergent Nonidet P40 (NP40) for a dialysable one, octylglucoside, while the proteins were immobilized on the lectin column and (ii) co-dialysis of the eluted glycoproteins in octylglucoside with phosphatidylcholine. The resultant virosomes had visible spikes and possessed haemagglutinating activity. These measles virosomes should provide a useful reagent for studying immune responses to measles virus, independent of the immunosuppressive effects of the whole virus.

Pathogenesis of Theiler's murine encephalomyelitis virus

n Publisher Summaryn n Theilers murine encephalomyelitis virus belongs to the family of picornaviridae. Picornaviruses are small ( “pico”), phylogenetically related RNA viruses. Based on different biochemical and biophysical characteristics picornaviruses are subdivided into four groups: enteroaphthovirus (foot-and-mouth disease virus), cardiovirus [encephalomyocarditis virus (EMCV), Mengo virus], and rhinovirus (human rhinovirus). Theilers murine encephalomyelitis virus was originally classified among the picornaviridae as an enterovirus because of its biological similarities with poliovirus. Further comparison of the complete genome of TMEV BeAn 8386 strain identifies remarkable similarities at the level of nucleotides and predicted amino acids between BeAn and the cardioviruses EMCV and Mengo virus. Theilers murine encephalomyelitis virus is a single-stranded nonenveloped RNA virus. The viral RNA is of positive sense, having the same polarity as mRNA. Viral mRNA lacks the cap structure found at the 5’ end of almost all eukaryotic mRNAs.n n

Virus‐Induced Autoimmunity Through Molecular Mimicry

The fundamental cause of many chronic debilitating diseases is not known. However, host responses to self could play an important role in many of these instances. Microorganisms and/or viruses in coalition with host immune responses are often associated with occurrences of disease. Viruses have been implicated with the initiation of autoimmunity; however, direct cause and effect evidence is often hard to derive. Immunologic cross-reactions or molecular mimicry, that is, shared determinants between a microorganism and self epitopes, could account for the breaking of tolerance and the initiation of antiself responses, leading to autoimmunity. Advances in current methodology have allowed us to explore the immunologic cross-reactions and determine what epitopes are important in the induction of disease. The first suggestive evidence that viruses could share common determinants with their hosts came from experiments showing an association between infection and the incidence of autoantibodies in patients with infectious active hepatitis. Ajdukiewicz et al. reported the presence of anti-smooth muscle antibodies. Later Toh et a/.* extended these observations to include infectious hepatitis, chicken pox, measles, and mumps viruses. They found reactivity to intermediate filament proteins. Over half the sera from infected individuals reacted with intermediate filament proteins. Only 6% of control sera were positive. Similar antibodies were also found in patients with infectious mononucleosis. However, in many instances it was not clear if these antibodies reacted with virus and self, or if the antibodies arose through polyclonal B-cell activation, or both. Reaction to other intracytoplasmic proteins has been described by Sotelo et aZ? They found autoantibodies against axonal neurofilaments in patients with subacute spongiform encephalopathies such as Kuru and Jakob-Creutzfeldt disease. These sera were tested in in vitro central nervous system cultures. Almost two thirds of patients with Jakob-Creutzfeldt disease and approximately one third of patients with Kuru had autoantibodies. These findings were the first evidence of an immune reaction occurring in relation to either of these encephalopathic diseases. In mouse studies of vaccinia virus infection, Steck ez al. demonstrated that inoculation of mice with a neurotropic strain resulted in the production of antibodies that reacted with myelin and oligodendrocytes. No antibodies were found to bind to neurons or thymocytes. Mice injected with a dermotropic strain of vaccinia did not produce autoantibodies to central nervous system elements. The antimyelin and the antioligodendrocyte antibodies could therefore not be removed by absorption using

Mimicry by Virus of Host Molecules: Implications for Autoimmune Disease

n n Molecular mimicry defines the shared identity of molecules from disparate genes or proteins. Thus, although their origins are as separate as a virus and the self-determinant of a human or lower animal, two molecules linear amino acid sequences or their conformational fits may be shared. Such molecular homologies between proteins occur frequently and likely play roles in the processing of viral proteins inside cells. The homologies shared between viruses and host cytoskeletal proteins likely indicate that shared determinants on cell linker proteins guided viral proteins along highways and stop points inside cells. Most importantly, these unexpected cross-reactivities have broad and major implications for understanding autoimmune disease. Molecular mimicry is detected either by using humoral or cellular immune components, that cross-react with two presumably unrelated protein structures, or by computer searches to match descriptions of proteins in storage banks. The use of both these approaches to define molecular mimicry and establish its potential role in autoimmune disease is the topic of this chapter.n n

Interferon-induced alterations in sialic acid and glycoconjugates of L-929 cells

Abstract Changes in Sialic acid and glycosphingolipid (GSL) metabolism were demonstrated in interferon (IFN)-treated L-929 cells. IFN induced an increase in total cell Sialic acid, sialoglycoproteins, and gangliosides, as shown by calorimetric and radiolabeling techniques. Expression of cell surface (neuraminidase-releasable) Sialic acid on IFN-treated cells was markedly elevated, particularly in the GSL fractions. The incorporation of [14C]galactose into glycoproteins, most neutral GSL homologs, and most ganglioside homologs also was elevated, with the more striking effects (two- to threefold) in the lipid fractions. An increase in the concentration of a ganglioside with the migration of GM2, as measured by chemical staining of chromatograms, was also shown. The observed effects were IFN dose dependent at ranges from 10 to 10,000 U/ml. As shown previously, IFN-treated L-929 cells became resistant to lysis by virus-induced IFN-activated natural killer cells. Correlations between high levels of surface Sialic acid, resistance to NK cell-mediated lysis, and tumor invasiveness have been shown in other systems.

Antibody Initiates Virus Persistence: Immune Modulation and Measles Virus Infection

By antibody-induced antigenic modulation, we mean the removal of antigens from the surface of cells by specific antibody. The result is to render such cells resistant to killing by immune reagents, i.e., antibody and complement or cytotoxic lymphocytes. Stripping of surface antigens to allow cells to withstand immunologic attack was first described in the context of the thymus leukemia (TL) differentiation antigen system. TL antigen could be stripped or modulated in vivo and in vitro by anti-TL antibody (reviewed in [1]). We have expanded the concept of antibody-induced antigenic modulation as an aid to understanding several persistent infections, with our primary interest in persistent measles virus infection of humans.

Mapping of the major histocompatibility complex and viral antigens on the plasma membrane of a measles virus-infected cell

The two measles virus glycoproteins, the hemagglutinin and fusion protein, are expressed on the surfaces of infected cells. Although the two molecules are chemically distinct, they associate on the cell surface, judging from their ability to comigrate (co-cap). However, neither is directly complexed with the major histocompatibility (MHC) gene products, HLA-A, -B, -C or -D, on the plasma membrane, based on results from three distinct assays. First, in tests of capping, these viral glycoproteins failed to comigrate with any HLA determinant. Second, electron microscopy showed that the viral glycoproteins occupied domains on the plasma membrane distinct from MHC gene products; 125I labeling of cell surface determinants and subsequent analysis by immune precipitation and PAGE confirmed this result. Third, incubation of measles virus-infected cells in the presence of monoclonal or polyclonal antibodies to measles virus glycoproteins removed the viral glycoproteins from the cells surfaces but did not cause a corresponding decrease in amounts of HLA molecules. These results indicate that the hemagglutinin and fusion polypeptides of measles virus lie in close association on the plasma membrane; however, neither is linked with MHC gene products.

Effects of regional spinal X-irradiation on demyelinating disease caused by Theiler's virus, mouse hepatitis virus or experimental allergic encephalomyelitis.

The effects of X-irradiation on the course of chronic demyelinating disease were examined in mice with experimental allergic encephalitis (EAE), mouse hepatitis virus (MHV) or Theilers virus (DAV) infection. One month after the induction of EAE or 2-16 months after inoculation of DAV, exposure of the cervical spinal cord to 20 Gy X-rays caused local exacerbation of disease activity but spinal irradiation did not affect MHV-induced demyelination. In EAE, there was a significant increase in the number of inflammatory cells in the irradiated part of the cord. Mice infected with DAV showed locally increased demyelination and axonal degeneration but no change in the titer of infectious virus within the cord. Thus in DAV infection, as in EAE, the exacerbation of disease seemed to be due to vascular or immunological factors rather than viral reactivation.