Virus-Induced Changes in Neural Cells

Virus infections of the CNS have attracted particular interest not only because of their medical importance but also because of the unique features that infections display within a compartmentalized and highly specialized organ system such as the CNS. To reach the CNS, the virus must overcome or circumvent the anatomical and physiological barriers of the CNS. Once inside the CNS, there seems to be no CNS intrinsic immune system activated but a recruitment of macrophages and an invasion of immune-competent and phagocytic cells. Immune reactions are probably crucial for clearance of virus from the infected CNS but they may also be involved in disease-associated reactions. Although most clinically manifested virus infections tend to become generalized, and virus infections of the CNS therefore may represent the result of a systemic spread of the infection, some viruses demonstrate a greater affinity for neural cells than others and exhibit neurotropic properties. The present chapter presents various aspects of virus-nerve cell interactions, but as information in particular at the molecular level is still very limited, it has been necessary for a more complete presentation to add some relevant observations on viral effects on nonneural cells.