Methyl-CpG binding protein 2, receptors of innate immunity and receptor for advanced glycation end-products in human viral meningoencephalitis.

Inflammation is a normal host defense reaction to infections and tissue injury. In pathology, the process of inflammation is deregulated by various environmental factors, prolonged activation of Toll-like receptors (TLRs), induction of epigenetic machinery or expression of receptors for advanced glycation end-products (RAGE). In the present study, we examined immunoexpression of proteins participating in the above-mentioned mechanisms, in the brain of patients with viral meningoencephalitis. The results showed that depending on the period of the disease, the process of inflammation is deregulated in different ways. In an early period of viral meningoencephalitis, we found numerous so-called microglial nodules which were strongly immunopositive to methyl-CpG protein 2 (MeCP2). This protein is an epigenetic factor important for methylation of DNA; therefore, our results suggest that cells collected in the nodules may participate in modification of the host defense reaction. Moreover, in the early period of viral meningoencephalitis, we found that Purkinje cells of the cerebellum contain TLR3 or TLR9 receptors that can recognize viral pathogens and may activate a self-destructive mechanism in these neurons. In the later (advanced) period of viral meningoencephalitis, despite some of the above observations, RAGE protein was detected in the brain of adult and aging patients. It means that in this period of the disease, the inflammatory process may be deregulated by numerous post-translationally modified proteins that are transported to the brain after binding with activated RAGE. In addition, young patients appeared more susceptible to viral infections than adult and aging patients, because most of them died during the early period of meningoencephalitis.