Immunology of viral infections

Immune responses to nonenveloped and enveloped viruses are different (see Table 1). The immune reactions to nonenveloped viruses are predominantly humoral responses against extracellular viruses, because nonenveloped viruses usually are released rapidly, a process that results in lysis and death of the infected cell, and because viral antigens are not present on the cell membrane. In contrast, cell-mediated immunity, together with humoral immune response, plays a major role in the defense against enveloped viral infections, since the release of enveloped viruses from the infected cells occurs slowly and the cell membrane contains viral antigens that become targets for effector cells of cell-mediated immunity.