What is the mechanism of viral injury?
Mechanisms of Viral Injury 1. Viral Tropism (Tissue and Cell Specificity) Host receptors for viruses Viruses are coated with surface proteins that bind with high specificity to particular host cell surface proteins. Entry of many viruses into cells commences with binding to normal host cell receptors. For example, HIV glycoprotein gp120 binds to CD4 and CXCR4 and CCR5 on T cells and macrophages. Host proteases may be needed to enable binding of the virus to host cells; for instance, a host protease cleaves and activates the influenza virus hemagglutinin. Specificity of transcription factors The ability of the virus to replicate inside particular cell types depends on the presence of lineage-specific transcription factors that recognize viral enhancer and promoter elements. For example, the JC virus, which causes leukoencephalopathy, replicates only in oligodendroglia in the CNS because the promoter and enhancer DNA sequences regulating viral gene expression are active in glial c...