How viruses may overcome non-specific defences in the host

Abstract

The pathogenicity of a virus is mainly related to its capacity to overcome the non-specific defences of a host. Fever limits the multiplication of viruses in vivo , thus allowing recovery; thermoresistant strains are virulent because they are capable of escaping the effect of hyperthermia. Resistance to the antiviral effect of interferon does not seem to exist per se but interferon may play an indirect role in virus virulence: (i) its effect may be minimized by the destruction of interferon-producing cells such as macrophages; (ii) interferon may render virus-infected target cells resistant to natural killer cell lysis. The interaction of viruses with phagocytic cells plays a predominant role; the ability to grow in macrophages or to induce macrophage blockade or paralysis may constitute a marker of virulence. This is particularly important in the liver in which the infection of Kupffer cells often represents the key event of the disease.