Molecular mimicry that primes for autoimmunity which is triggered by infection

Molecular mimicry in multiple sclerosis

Two main etiological components are considered important in human autoimmune diseases including multiple sclerosis (MS), first the immunogenetic background and second environmental factors. Among the latter, infectious organisms are probably the most relevant, and epidemiological studies in MS firmly support that viral infections often precede disease exacerbations or the onset of MS. Infectious agents can contribute to disease development or phenotypic expression in different ways. Our focus will be directed on molecular mimicry, i.e. antigenic similarity between structural epitopes or peptide sequences from infectious organisms with those found in self proteins of the host. The intriguing concept of molecular mimicry has evolved substantially since its introduction over 20 years ago. We will summarize the most important developments and discuss puzzling questions, which remain open despite many claims that molecular mimicry is involved in the development of human autoimmune disease after infections or vaccinations.

Prenatal viral infection in mouse causes differential expression of genes in brains of mouse progeny: a potential animal model for schizophrenia and autism

Schizophrenia and autism are neurodevelopmental disorders with genetic and environmental etiologies. Prenatal viral infection has been associated with both disorders. We investigated the effects of prenatal viral infection on gene regulation in offspring of Balb-c mice using microarray technology. The results showed significant upregulation of 21 genes and downregulation of 18 genes in the affected neonatal brain homogenates spanning gene families affecting cell structure and function, namely, cytosolic chaperone system, HSC70, Bicaudal D, aquaporin 4, carbonic anhydrase 3, glycine receptor, norepinephrine transporter, and myelin basic protein. We also verified the results using QPCR measurements of selected mRNA species. These results show for the first time that prenatal human influenza viral infection on day 9 of pregnancy leads to alterations in a subset of genes in brains of exposed offspring, potentially leading to permanent changes in brain structure and function.

Hit-Hit and hit-Run: viruses in the playing field of multiple sclerosis

Viruses have been major players in the search for the cause of multiple sclerosis (MS). In support of the viral theory is the predominance of CD8+ T cells and class-I major histocompatibility complex in lesions, the powerful therapeutic effects of beta interferons, the ease of inducing demyelination in experimental models following virus challenge, and the documented examples of several human demyelinating diseases conclusively demonstrated to be of viral origin. We propose two hypotheses of how viruses may cause MS. In the "Hit-Hit" hypothesis, the virus persists or may be reactivated in the central nervous system (CNS). Injury is the result of direct viral damage and by an attempt of the immune response to clear the infectious agent. In the "Hit-Run" hypothesis, virus infects the periphery but never enters the CNS. The virus sets up an abnormal immunologic milieu for subsequent autoimmunity. In both scenarios, knowing the inciting virus would be expected to eliminate disease if the population were vaccinated to prevent infection. In the treatment of patients with fully established disease, the Hit-Hit hypothesis would require that antiviral agents enter the CNS and stop replication. In the case of the Hit-Run hypothesis, treatment of patients with established disease with antiviral agents would be futile.