Abstract

Several microorganisms can cause neuroinfections of the central nervous system (CNS). The most common cause of long-lasting neurologic symptoms with potentially fatal consequences is viruses. Viral infections of the CNS not only cause rapid alterations in a variety of cellular processes and have direct effects on their host cells, but they also result in a strong immune response. Microglia, the primary immune cells of the CNS, is essential for the regulation of the innate immune response, although astrocytes also play a role. These cells line along blood arteries and ventricular canals, making them one of the first cell types to contract an infection when the virus enters the central nervous system. A significant impact on cellular and tissue physiology and morphology may result from the immune response triggered by the presence of intracellular virus particles. Moreover, astrocytes are increasingly understood to be a possible viral reservoir in the central nervous system (CNS). Given that they might be a factor in recurrent neurologic sequelae, these alterations should be addressed in terms of lingering infections. A number of viruses, including those from the families Flaviviridae, Coronaviridae, Retroviridae, Togaviridae, Paramyxoviridae, Picomaviridae, Rhabdoviridae, and Herpesviridae, have been demonstrated to infect astrocytes thus far. Many receptors are expressed by astrocytes, which can detect virus particles and start signaling processes that result in an innate immune response. In this review, we describe the current understanding of viral receptors that trigger astrocyte production of inflammatory cytokines and show how astrocytes are involved in CNS immunological processes.